WO2016166973A1 - Communication device, communication method, and communication system - Google Patents

Abstract

There is provided a communication device that includes: a communication unit that supplies a first signal to an optical transmitter and receives a second signal from an optical receiver, in which the optical transmitter transmits an optical signal, and the optical receiver receives an optical signal; and a coupling detection unit that performs a first coupling detecting operation that involves detection of coupling to a communication partner with use of an electrical signal.

Description

COMMUNICATION DEVICE, COMMUNICATION METHOD, AND COMMUNICATION SYSTEM CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of japanese priority patent application jp 2015-084692 filed on April 17, 2015, the entire contents of which are incorporated herein by reference.

The disclosure relates to a communication device that exchanges data, a communication method used in the communication device, and a communication system including the communication device.

In accordance with recent higher-functionalization and multi-functionalization of electronic apparatuses, an electronic apparatus comes to exchange a larger amount of information with other electronic apparatuses. For example, an electronic apparatus may be often coupled to other electronic apparatuses by means of wired communication. Wired communication may often involve using an optical fiber in a case with exchange of a larger amount of data.

In an optical communication system with use of an optical fiber, measures may be often taken to restrain influences of an optical signal on a human body. For example, Patent Literature 1 (PTL1) discloses a communication system that supervises coupling of communication devices by means of transmission and reception of pulse signals with use of light of a wavelength different from a wavelength used in data communication. Patent Literature 2 (PTL2) discloses a communication system that includes a coupling confirmation mode and a normal communication mode; in the coupling confirmation mode, a pulse signal may be transmitted and received to confirm coupling of communication devices; after the coupling is confirmed, modes may be switched from the coupling confirmation mode to the normal communication mode.

JP 2000-286798A JP 2011-147086A

Summary

As described, in communication systems, there has been pursuit for a high level of safety, as well as expectation for further enhancement in safety.

It is therefore desirable to provide a communication device, a communication method, and a communication system that make it possible to enhance safety.

According to an embodiment of the disclosure, there is provided a communication device that includes: a communication unit; and a coupling detection unit. The communication unit supplies a first signal to an optical transmitter and receives a second signal from an optical receiver, in which the optical transmitter transmits an optical signal, and the optical receiver receives an optical signal. The coupling detection unit performs a first coupling detecting operation that involves detection of coupling to a communication partner with use of an electrical signal.

According to an embodiment of the disclosure, there is provided a communication method that includes: performing a first coupling detecting operation that involves detection of coupling to a communication partner with use of an electrical signal; and performing a second coupling detecting operation that involves detection of coupling to the communication partner with use of an optical signal, after the coupling has been detected in the first coupling detecting operation.

According to an embodiment of the disclosure, there is provided a communication system that includes: a first communication device; and a second communication device. The first communication device includes a communication unit and a coupling detection unit. The communication unit supplies a first signal to an optical transmitter and receives a second signal from an optical receiver, in which the optical transmitter transmits an optical signal to the second communication device, and the optical receiver receives an optical signal transmitted from the second communication device. The coupling detection unit performs a first coupling detecting operation that involves detection of coupling to the second communication device with use of an electrical signal.

In the communication device and the communication system according to the above-described embodiments of the disclosure, in the coupling detection unit, the first coupling detecting operation is performed with use of the electrical signal. Then, the first signal is supplied from the communication unit to the optical transmitter, and the second signal is supplied from the optical receiver to the communication unit.

In the communication method according to the above-described embodiment of the disclosure, the first coupling detecting operation is performed with use of the electrical signal, while the second coupling detecting operation is performed with use of the optical signal. The second coupling detecting operation is performed after the coupling has been detected in the first coupling detecting operation.

According to the communication device, the communication method, and the communication system according to the above-described embodiments of the disclosure, the first coupling detecting operation is performed with use of the electrical signal. Hence, it is possible to enhance safety. It is to be noted that some effects described here are not necessarily limitative, and any of other effects described herein may be achieved.

Fig. 1 is a block diagram of one configuration example of a communication system according to an embodiment of the disclosure. Fig. 2 is a waveform chart of one waveform example of pulse signals. Fig. 3 is a waveform chart of another waveform example of the pulse signals. Fig. 4A is a flowchart of one operation example of a communication device. Fig. 4B is a flowchart of one operation example of the communication device. Fig. 5 is a flowchart illustrating an example of a connection establishment sequence. Fig. 6A is a waveform chart illustrating an example of a pulse signal in an optical connection detection portion of a connection establishment sequence. Fig. 6B is a waveform chart illustrating an example of a pulse signal in an optical connection detection portion of a connection establishment sequence. Fig. 6C is a waveform chart illustrating an example of a pulse signal in an optical connection detection portion of a connection establishment sequence. Fig. 7 is a timing diagram illustrating timing relationships among electrical connection detection and optical connection detection portions of a connection establishment sequence.

In the following, some embodiments of the disclosure are described in detail with reference to the drawings.

(Configuration Example)
Fig. 1 illustrates one configuration example of a communication system (a communication system 1) according to an embodiment. The communication system 1 is adapted to perform communication by means of an optical signal. The communication system 1 may include a transmission cable 90, and communication devices 10 and 20. The communication device 10 and the communication device 20 may be coupled to one another through the transmission cable 90.

The transmission cable 90 may include optical fibers 901 and 902, electrical wires 911 and 912, and connectors 91 and 92. The optical fiber 901 is adapted to transmit a signal from the communication device 10 to the communication device 20. The optical fiber 902 is adapted to transmit a signal from the communication device 20 to the communication device 10. The electrical wires 911 and 912 are adapted to allow the communication devices 10 and 20 to transmit a coupling signal to detect coupling to one another. Specifically, the electrical wire 911 is adapted to transmit a coupling signal S51 from the communication device 10 to the communication device 20. The electrical wire 912 is adapted to transmit a coupling signal S81 from the communication device 20 to the communication device 10. The connector 91 may be provided at one end of the transmission cable 90, and may be configured to be coupled to a connector 11 of the communication device 10. The connector 92 may be provided at another end of the transmission cable 90, and may be configured to be coupled to a connector 21 of the communication device 20.

(Communication Device 10)
The communication device 10 is adapted to transmit a signal to the communication device 20 through the optical fiber 901, and to receive a signal transmitted from the communication device 20 through the optical fiber 902. The communication device 10 may include the connector 11, a coupling detector 50, a transmitter 30, an optical transmitter 12, an optical receiver 13, a receiver 40, and controller 14.

The connector 11 is configured to be coupled to the connector 91 of the transmission cable 90.

The coupling detector 50 is adapted to perform a coupling detecting operation M1. The coupling detecting operation M1 may involve detection of coupling of the communication devices 10 and 20 to one another through the electrical wires 911 and 912. The coupling detector 50 may include a coupling signal transmitter 51 and a coupling signal receiver 52. The coupling signal transmitter 51 is adapted to transmit the coupling signal S51 to the communication device 20 through the electrical wire 911. The coupling signal receiver 52 is adapted to receive, through the electrical wire 912, the coupling signal S81 transmitted from the communication device 20, and thereby to detect the coupling of the communication devices 10 and 20 to one another through the electrical wire 912. The coupling signal receiver 52 is adapted to notify the controller 14 of a result of the detection of the coupling.

The transmitter 30 is adapted to transmit pulse signals P11 and P12 in a coupling detecting operation M2, and to transmit data INF1 in a data communicating operation M3. The coupling detecting operation M2 may involve detection of coupling of the communication devices 10 and 20 to one another through the optical fibers 901 and 902. The transmitter 30 may include pulse signal generators 32 and 33, a processor 31, and a selector 34.

The pulse signal generator 32 is adapted to generate the pulse signal P11 and to supply the pulse signal P11 to the selector 34, in the coupling detecting operation M2. Similarly, the pulse signal generator 33 is adapted to generate the pulse signal P12 and to supply the pulse signal P12 to the selector 34, in the coupling detecting operation M2.

Fig. 2 illustrates one waveform example of the pulse signals P11 and P12. The pulse signals P11 and P12 may have a pulse waveform repeated in a predetermined cycle T. In the communication system 1, use of the pulse signals P11 and P12 makes it possible to reduce average energy of an optical signal, in the coupling detecting operation M2. In this way, for example, in a case with a leakage of the optical signal from the optical fiber 901, it is possible to restrain influences of the leak optical signal on a human body. In this example, a pulse width PW11 of the pulse signal P11 may be smaller than a pulse width PW12 of the pulse signal P12. Note that this is non-limiting. For example, the pulse width PW11 of the pulse signal P11 may be larger than the pulse width PW12 of the pulse signal P12.

The processor 31 is adapted to perform predetermined processing to generate the data INF1, and to supply the data INF1 to the selector 34, in the data communicating operation M3.

The selector 34 is adapted to select, based on a control signal SEL1, one of the data INF1, the pulse signal P11, and the pulse signal P12, and to output the selected signal as a signal S30.

With this configuration, the transmitter 30 is adapted to selectively transmit one of the pulse signal P11 and the pulse signal P12, in the coupling detecting operation M2. Also, the transmitter 30 is adapted to alternatively select the pulse signal P11 and the pulse signal P12 every predetermined time T1, and to transmit the selected one, as illustrated in Fig. 3, in the coupling detecting operation M2. Moreover, the transmitter 30 is adapted to transmit the data INF1, in the data communicating operation M3.

The optical transmitter 12 is adapted to convert an electrical signal (the signal S30) to an optical signal, and to output the optical signal, and may include, for example, a laser diode. Also, the optical transmitter 12 is adapted to supply the optical signal thus outputted, to the communication device 20 through the optical fiber 901.

The optical receiver 13 is adapted to convert an optical signal transmitted from the communication device 20 through the optical fiber 902, to an electrical signal to generate a signal S13, and may include, for example, a photodetector. The signal S13 may include data INF2, and pulse signals P21 and P22. The pulse signal P21 may be a similar signal to the pulse signal P11 (see Fig. 2). The pulse signal P22 may be a similar signal to the pulse signal P12 (see Fig. 2).

The receiver 40 is adapted to receive the pulse signals P21 and P22 in the coupling detecting operation M2, and to receive the data INF2 in the data communicating operation M3. The receiver 40 may include pulse signal detectors 42 and 43, and a processor 41. The pulse signal detector 42 is adapted to detect the pulse signal P21 included in the signal P13, and to supply a result of the detection to the controller 14, in the coupling detecting operation M2. The pulse signal detector 43 is adapted to detect the pulse signal P22 included in the signal P13, and to supply a result of the detection to the controller 14, in the coupling detecting operation M2. The processor 41 is adapted to perform predetermined processing based on the data INF2 included in the signal P13, in the data communicating operation M3.

The controller 14 is adapted to control operation of each block in the communication device 10. Specifically, first, the controller 14 may control the coupling detector 50 to allow the coupling detecting operation M1 to be started. Then, in a case in which the coupling of the communication devices 10 and 20 to one another through the electrical wire 912 has been detected in the coupling detecting operation M1, the controller 14 may control the transmitter 30 and the receiver 40 to allow the coupling detecting operation M2 to be started. Then, in a case in which the coupling of the communication devices 10 and 20 to one another through the optical fibers 901 and 902 has been detected in the coupling detecting operation M2, the controller 14 may control the transmitter 30 and the receiver 40 to allow the coupling detecting operation M2 to be terminated and to allow the data communicating operation M3 to be started.

The controller 14 may include a timer 15. The timer 15 is adapted to start measurement of time simultaneously with the start of the coupling detecting operation M2. In a case in which the coupling detecting operation M2 is not terminated within a predetermined time (a time limit Tlim) prescribed in advance, the controller 14 may control the transmitter 30 and the receiver 40 to allow the coupling detecting operation M2 to be terminated and to allow the coupling detecting operation M1 to be performed again.

(Communication Device 20)
The communication device 20 is adapted to transmit a data signal to the communication device 10 through the optical fiber 902, and to receive a data signal transmitted from the communication device 10 through the optical fiber 901. The communication device 20 may include a connector 21, a coupling detector 80, a transmitter 60, an optical transmitter 22, an optical receiver 23, a receiver 70, and a controller 24. In other words, the communication device 20 may have a similar configuration to that of the communication device 10.

The connector 21 is configured to be coupled to the connector 92 of the transmission cable 90.

The coupling detector 80 is adapted to perform the coupling detecting operation M1, similarly to the coupling detector 50 of the communication device 10. The coupling detector 80 may include a coupling signal transmitter 81 and a coupling signal receiver 82. The coupling signal transmitter 81 is adapted to transmit the coupling signal S81 to the communication device 10 through the electrical wire 912. The coupling signal receiver 82 is adapted to receive, through the electrical wire 911, the coupling signal S51 transmitted from the communication device 10, and thereby to detect the coupling of the communication devices 10 and 20 to one another through the electrical wire 911. The coupling signal receiver 82 is adapted to notify the controller 24 of a result of the detection of the coupling.

The transmitter 60 is adapted to transmit the pulse signals P21 and P22 in the coupling detecting operation M2, and to transmit data INF2 in the data communicating operation M3, similarly to the transmitter 30 of the communication device 10. The transmitter 60 may include pulse signal generators 62 and 63, a processor 61, and a selector 64. The pulse signal generator 62 is adapted to generate the pulse signal P21 and to supply the pulse signal P21 to the selector 64, in the coupling detecting operation M2. The pulse signal generator 63 is adapted to generate the pulse signal P22 and to supply the pulse signal P22 to the selector 64, in the coupling detecting operation M2. The processor 61 is adapted to perform predetermined processing to generate the data INF2, and to supply the data INF2 to the selector 64, in the data communicating operation M3. The selector 64 is adapted to select, based on a control signal SEL2, one of the data INF2, the pulse signal P21, and the pulse signal P22, and to output the selected signal as a signal S60. With this configuration, the transmitter 60 is adapted to selectively transmit one of the pulse signal P21 and the pulse signal P22, in the coupling detecting operation M2. Also, the transmitter 60 is adapted to alternatively select the pulse signal P21 and the pulse signal P22 every predetermined time T1, and to transmit the selected one, in the coupling detecting operation M2. Moreover, the transmitter 60 is adapted to transmit the data INF2, in the data communicating operation M3.

The optical transmitter 22 is adapted to convert an electrical signal (the signal S60) to an optical signal, and to output the optical signal, similarly to the optical transmitter 12 of the communication device 10. Also, the optical transmitter 22 is adapted to supply the optical signal thus outputted, to the communication device 10 through the optical fiber 902.

The optical receiver 23 is adapted to convert an optical signal transmitted from the communication device 10 through the optical fiber 901, to an electrical signal to generate a signal S23, similarly to the optical receiver 13 of the communication device 10. The signal S23 may include the data INF1, and the pulse signals P11 and P12.

The receiver 70 may include pulse signal detectors 72 and 73, and a processor 71, similarly to the receiver 40 of the communication device 10. The pulse signal detector 72 is adapted to detect the pulse signal P11 included in the signal P23, and to supply a result of the detection to the controller 24, in the coupling detecting operation M2. Similarly, the pulse signal detector 73 is adapted to detect the pulse signal P12 included in the signal P23, and to supply a result of the detection to the controller 24, in the coupling detecting operation M2. The processor 71 is adapted to perform predetermined processing based on the data INF1 included in the signal P23, in the data communicating operation M3.

The controller 24 is adapted to control operation of each block in the communication device 20, similarly to the controller 14 of the communication device 10. Specifically, first, the controller 24 may control the coupling detector 80 to allow the coupling detecting operation M1 to be started. Then, in a case in which the coupling of the communication devices 10 and 20 to one another through the electrical wire 911 has been detected in the coupling detecting operation M1, the controller 24 may control the transmitter 60 and the receiver 70 to allow the coupling detecting operation M2 to be started. Then, in a case in which the coupling of the communication devices 10 and 20 to one another through the optical fibers 901 and 902 has been detected in the coupling detecting operation M2, the controller 24 may control the transmitter 60 and the receiver 70 to allow the coupling detecting operation M2 to be terminated and to allow the data communicating operation M3 to be started.

The controller 24 may include a timer 25. The timer 25 is adapted to start measurement of time simultaneously with the start of the coupling detecting operation M2. In a case in which the coupling detecting operation M2 is not terminated within a predetermined time (the time limit Tlim), the controller 24 may control the transmitter 60 and the receiver 70 to allow the coupling detecting operation M2 to be terminated and to allow the coupling detecting operation M1 to be performed again.

Here, the transmitter 30 and the receiver 40 correspond to one concrete example of a "communication unit" of the disclosure. The coupling detector 50 corresponds to one concrete example of a "coupling detection unit" of the disclosure. The coupling detecting operation M1 corresponds to one concrete example of a "first coupling detecting operation" of the disclosure. The coupling detecting operation M2 corresponds to one concrete example of a "second coupling detecting operation" of the disclosure. The pulse signal P11 corresponds to one concrete example of a "first pulse signal" of the disclosure. The pulse signal P21 corresponds to one concrete example of a "second pulse signal" of the disclosure. The pulse signal P12 corresponds to one concrete example of a "third pulse signal" of the disclosure. The pulse signal P22 corresponds to one concrete example of a "fourth pulse signal" of the disclosure.

(Operation and Workings)
Next, description is given on the operation and workings of the communication system 1 according to the embodiment.

(Outline of General Operation)
First, an outline of general operation of the communication system 1 is described with reference to Fig. 1. In the communication system 1, first, the communication devices 10 and 20 may perform the coupling detecting operation M1. Specifically, the coupling signal transmitter 51 of the communication device 10 may transmit the coupling signal S51 to the communication device 20 through the electrical wire 911; the coupling signal receiver 82 of the communication device 20 may receive the coupling signal S51. Similarly, the coupling signal transmitter 81 of the communication device 20 may transmit the coupling signal S81 to the communication device 10 through the electrical wire 912; the coupling signal receiver 52 of the communication device 10 may receive the coupling signal S81. Then, in a case in which the coupling of the communication devices 10 and 20 to one another through the electrical wires 911 and 912 has been detected in the coupling detecting operation M1, the communication devices 10 and 20 may perform the coupling detecting operation M2. Specifically, the transmitter 30 of the communication device 10 may transmit the pulse signals P11 and P12 to the communication device 20 through the optical fiber 901; the receiver 70 of the communication device 20 may receive the pulse signals P11 and P12. Similarly, the transmitter 60 of the communication device 20 may transmit the pulse signals P21 and P22 to the communication device 10 through the optical fiber 902; the receiver 40 of the communication device 10 may receive the pulse signals P21 and P22. Then, in a case in which the coupling of the communication devices 10 and 20 to one another through the optical fibers 901 and 902 has been detected in the coupling detecting operation M2, the communication devices 10 and 20 may perform the data communicating operation M3.

(Detailed Operation)
Description is given next of details of the coupling detecting operations M1 and M2 in the communication system 1.

Figs. 4A and 4B illustrate one operation example in the communication device 10. Note that, although description in this example is given on the communication device 10, the description may apply to the communication device 20; the operation of the communication device 10 and the operation of the communication device 20 may be performed in parallel to one another. First, the communication device 10 may start the coupling detecting operation M1 (steps S1 and S2), and next, may start the coupling detecting operation M2 (steps S3 to S18). Then, in a case in which the coupling of the communication devices 10 and 20 to one another through the optical fibers 901 and 902 has been detected in the coupling detecting operation M2, the communication device 10 may allow the coupling detecting operation M2 to be terminated, and may allow the data communicating operation M3 to be started. In the following, description is given in detail of this operation.

First, when powered on, the communication device 10 may start transmission of the coupling signal S51 and may start detection of the coupling signal S81 (step S1). Specifically, the coupling signal transmitter 51 of the coupling detector 50 may start the transmission of the coupling signal S51 to the communication device 20, while the coupling signal receiver 52 of the coupling detector 50 may start the detection of the coupling signal S81 transmitted from the communication device 20.

Next, the controller 14 may confirm whether or not the coupling signal receiver 52 has detected the coupling signal S81 transmitted from the communication device 20 (step S2). When the coupling signal receiver 52 has not detected the coupling signal S81 ("N" in step S2), the flow may repeat step S2 until the coupling signal S81 is detected.

Note that, even after this, the communication device 10 may continuously perform the operation of the detection of the coupling signal S81 (the coupling detecting operation M1), as illustrated in steps S7, S12, and S17.

In step S2, when the coupling signal receiver 52 has detected the coupling signal S81 ("Y" in step S2), the timer 15 of the controller 14 may start the measurement of time.

Next, the transmitter 30 may start the transmission of the pulse signal P11, while the receiver 40 may start the detection of the pulse signal P21 (step S4). Specifically, the controller 14 may control the selector 34 with use of the control signal SEL1; the selector 34 may select the pulse signal P11 and may output the pulse signal P11. Also, the controller 14 may control the pulse signal detector 42 with use of an undepicted control signal; the pulse signal detector 42 may start the detection of the pulse signal P21.

Next, the controller 14 may confirm whether or not time indicated by the timer 15 is within the time limit Tlim (step S5).

In step S5, when the time indicated by the timer 15 exceeds the time limit Tlim ("N" in step S5), the transmitter 30 may stop the transmission of the pulse signal P11, while the receiver 40 may stop the detection of the pulse signal P21 (step S6). Then, the flow may return to step S2.

In step S5, when the time indicated by the timer 15 is within the time limit Tlim ("Y" in step S5), the controller 14 may confirm whether or not the coupling signal receiver 52 is continuously detecting the coupling signal S81 transmitted from the communication device 20 (step S7).

In step S7, when the coupling signal receiver 52 is not detecting the coupling signal S81 ("N" in step S7), the flow may proceed to step S6. Then, the transmitter 30 may stop the transmission of the pulse signal P11, while the receiver 40 may stop the detection of the pulse signal P21, and the flow may return to step S1.

In step S7, when the coupling signal receiver 52 is continuously detecting the coupling signal S81 ("Y" in step S7), the controller 14 may confirm whether or not the receiver 40 has detected the pulse signal P21 (step S8). When the receiver 40 has not detected the pulse signal P21 ("N" in step S8), the flow may return to step S5, and may repeat steps S5 to S8.

In step S8, when the receiver 40 has detected the pulse signal P21 ("Y" in step S8), the transmitter 30 may start the transmission of the pulse signals P11 and P12, while the receiver 40 may start the detection of the pulse signals P21 and P22 (step S9). Specifically, the controller 14 may control the selector 34 with use of the control signal SEL1; as illustrated in Fig. 3, the selector 34 may alternately select the pulse signal P11 and the pulse signal P12 every predetermined time T1, and may output the selected one. Also, the controller 14 may control the pulse signal detectors 42 and 43 with use of an undepicted control signal; the pulse signal detector 42 may start the detection of the pulse signal P21, while the pulse signal detector 43 may start the detection of the pulse signal P22.

Next, the controller 14 may confirm whether or not the time indicated by the timer 15 is within the time limit Tlim (step S10).

In step S10, when the time indicated by the timer 15 exceeds the time limit Tlim ("N" in step S10), the transmitter 30 may stop the transmission of the pulse signals P11 and P12, while the receiver 40 may stop the detection of the pulse signals P21 and P22 (step S11). Then, the flow may return to step S2.

In step S10, when the time indicated by the timer 15 is within the time limit (Tlim) ("Y" in step S10), the controller 14 may confirm whether or not the coupling signal receiver 52 is continuously detecting the coupling signal S81 transmitted from the communication device 20 (step S12).

In step S12, when the coupling signal receiver 52 is not detecting the coupling signal S81 ("N" in step S12), the flow may proceed to step S11. Then, the transmitter 30 may stop the transmission of the pulse signals P11 and P12, while the receiver 40 may stop the detection of the pulse signals P21 and P22, and the flow may return to step S1.

In step S12, when the coupling signal receiver 52 is continuously detecting the coupling signal S81 ("Y" in step S12), the controller 14 may confirm whether or not the receiver 40 has detected the pulse signals P21 and P22 (step S13). When the receiver 40 has not detected the pulse signals P21 and P22 ("N" in step S13), the flow may return to step S10, and may repeat steps S10 to S13.

In step S13, when the receiver 40 has detected the pulse signals P21 and P22 ("Y" in step S13), the transmitter 30 may start the transmission of the pulse signal P12, while the receiver 40 may start the detection of the pulse signal P22 (step S14). Specifically, the controller 14 may control the selector 34 with use of the control signal SEL1; the selector 34 may select the pulse signal P12, and may output the pulse signal P12. Also, the controller 14 may control the pulse signal detector 43 with use of an undepicted control signal; the pulse signal detector 43 may start the detection of the pulse signal P22.

Next, the controller 14 may confirm whether or not the time indicated by the timer 15 is within the time limit Tlim (step S15).

In step S15, when the time indicated by the timer 15 exceeds the time limit Tlim ("N" in step S15), the transmitter 30 may stop the transmission of the pulse signal P12, while the receiver 40 may stop the detection of the pulse signal P22 (step S16). Then, the flow may return to step S2.

In step S15, when the time indicated by the timer 15 is within the time limit Tlim ("Y" in step S15), the controller 14 may confirm whether or not the coupling signal receiver 52 is continuously detecting the coupling signal S81 transmitted from the communication device 20 (step S17).

In step S17, when the coupling signal receiver 52 is not detecting the coupling signal S81 ("N" in step S17), the flow proceeds to step S16. Then, the transmitter 30 may stop the transmission of the pulse signal P12, while the receiver 40 may stop the detection of the pulse signal P22, and the flow may return to step S1.

In step S17, when the coupling signal receiver 52 is continuously detecting the coupling signal S81 ("Y" in step S17), the controller 14 may confirm whether or not the receiver 40 has detected the pulse signal P22 (step S18). When the receiver 40 has not detected the pulse signal P22 ("N" in step S18), the flow may return to step S15, and may repeat steps S15 to S18.

In step S18, when the receiver 40 has detected the pulse signal P22 ("Y" in step S18), the transmitter 30 may start data communication (step S19). Specifically, the controller 14 may control the selector 34 with use of the control signal SEL1; the selector 34 may select the data INF1 and may transmit the data INF1. Also, the controller 14 may control the processor 41 with use of an undepicted control signal; the processor 41 may receive the data INF2.

Note that, after the start of the data communication in this way, the confirmation whether or not the coupling signal receiver 52 is continuously detecting the coupling signal S81 may be continued. Then, when the coupling signal receiver 52 is not detecting the coupling signal S81, the transmitter 30 may stop the transmission of the data INF1, and the flow may return to step S2.

Thus, the flow may be terminated. The communication device 10 may perform the coupling detecting operation M1 and the coupling detecting operation M2 in this way. After the coupling of the communication devices 10 and 20 to one another through the optical fibers 901 and 902 has been detected in the coupling detecting operation M2, the communication device 10 may start the data communicating operation M3.

As described, in the communication system 1, first, the coupling detecting operation M1 with use of the electrical signal is performed. The coupling detecting operation M1 involves the detection of the coupling of the communication devices 10 and 20 to one another through the electrical wires 911 and 912. Accordingly, in the communication system 1, the coupling detecting operation M2 with use of the optical signal is not started, when the communication devices 10 and 20 are not coupled to one another through the transmission cable 90. Hence, it is possible to reduce possibility of exposure of a human body to the optical signal.

Also, in the communication system 1, the coupling detecting operation M2 with use of the optical signal may be performed after the coupling detecting operation M1 with use of the electrical signal. Accordingly, in the communication system 1, it is possible to detect a case in which the electrical wires 911 and 912 are connected but the optical fibers 901 and 902 are disconnected.

Moreover, the pulse signal may be used in the coupling detecting operation M2, leading to reduction in the average energy of the optical signal. Hence, in a case of the leakage of the optical signal, it is possible to restrain the influences of the leak optical signal on a human body.

Furthermore, the data communicating operation M3 with use of the optical signal may be started, after connection of the optical fibers 901 and 902 has been detected in the coupling detecting operation M2. Accordingly, the data communicating operation M3 with use of the optical signal is not started, in a case with, for example, disconnection of the optical fibers 901 and 902. Hence, it is possible to reduce possibility of a leakage of the optical signal having high average energy from the optical fibers 901 and 902.

In addition, in the communication system 1, there may be provided the time limit Tlim; in a case in which the coupling detecting operation M2 with use of the optical signal is not terminated within the time limit Tlim, the transmission of the optical signal may be stopped, and the coupling detecting operation M1 with use of the electrical signal may be performed again. Accordingly, in the communication system 1, there is no unnecessary continuous transmission of the optical signal. Hence, it is possible to reduce possibility of exposure of a human body to the optical signal.

Moreover, in the communication system 1, the coupling signal receiver 52 may continuously detect the coupling signal S81. Accordingly, the transmission of the optical signal may be stopped, for example, in a case in which the transmission cable 90 comes off from the communication devices 10 and 20, or in a case in which the transmission cable 90 is disconnected. Hence, it is possible to reduce possibility of exposure of a human body to the optical signal.

(Effects)
As described above, in the embodiment, the coupling detecting operation M1 with use of the electrical signal is performed. Accordingly, the coupling detecting operation M2 with use of the optical signal is not started in a case in which the communication devices are not coupled to one another through the transmission cable. Hence, it is possible to reduce possibility of exposure of a human body to the optical signal.

In the embodiment, the coupling detecting operation M2 with use of the optical signal may be performed, after the coupling detecting operation M1 with use of the electrical signal. Hence, it is possible to detect a case in which the electrical wires are connected but the optical fibers are disconnected.

In the embodiment, the pulse signals may be used in the coupling detecting operation M2, leading to reduction in the average energy of the optical signal. Hence, in a case of the leakage of the optical signal, it is possible to restrain the influences of the leak optical signal on a human body.

In the embodiment, the data communicating operation M3 may be started, after the coupling detecting operation M2. Accordingly, the data communicating operation M3 with use of the optical signal is not started, in a case with, for example, disconnection of the optical fibers. Hence, it is possible to reduce possibility of a leakage of the optical signal having high average energy from the optical fibers.

Moreover, in the communication system 1, there may be provided a time limit; in a case in which the coupling detecting operation M2 with use of the optical signal is not terminated within the time limit, the transmission of the optical signal may be stopped. Accordingly, there is no unnecessary continuous transmission of the optical signal, leading to reduction in possibility of exposure of a human body to the optical signal.

In the embodiment, the coupling signal receiver may continuously detect the coupling signal. Accordingly, the transmission of the optical signal may be stopped, for example, in a case in which the transmission cable comes off from the communication device, or in a case in which the transmission cable is disconnected. Hence, it is possible to reduce possibility of exposure of a human body to the optical signal.

In one example, Automatic Power Reduction (APR) is applied according to Laser Safety Requirements defined in IEC 60825-2. There, the appropriate APR of the transmitter channel(s) of communication device(s) is performed whenever the connection is determined to be broken.

Fig. 5 is a flowchart illustrating an example of a connection establishment sequence. The sequence may be performed by either or both communication devices for which a connection is being established.

In a no-connection (NC) state (502) the communication devices are not connected, or at least are determined as not being connected. Once a connection (504) is made, the connection establishment sequence initiates, commencing with an electrical connection establishment (ECE), then an optical connection detection (OCD), then an establish and configure connection (ECC).

The ECE (506) is determined using an electrical connection between the communication devices, such as the previously described electrical wires (Fig. 1, 911, 912).

Preferably, the communication devices subject to the connection establishment sequence shall always observe and detect the electrical connection. For example, the coupling signal transmitter provides a voltage level to another communication device through the electrical connection, and the coupling signal receiver detects a voltage level from the other communication device through the electrical connection. The controller is configured to monitor those signals accordingly.

In one example, in the absence of a confirmed electrical connection or “ECE state”, all optical output shall be prohibited from the communication devices.

Table 1 provides an example of conditions to be satisfied to confirm an ECE state.
Table 1:

Once an ECE state is established, the electrical connection continues to be monitored. Table 2 provides an example of conditions that, when detected, result in a determination that there is no longer a valid ECE state, or an electrical connection invalidation (ECI).
Table 2:

If there is an ECI at any point (depicted as ECE “fail”), then an ECE must be re-established to continue with the sequence.

As is evident from the exemplary duration times, there is a timing difference between a connection phase (ECE) and a disconnection phase (ECI). Specifically, the duration time in ECI is shorter than the duration time for ECE, which contributes to safety. Also, the electrical cable could be relatively long, so the threshold in ECE (e.g., >2.3V) is preferably arranged to take into account the IR drop from ideal voltage. But at still lower voltages (e.g., < 1.0V), it can indicate a condition that the cable is about to break, making the resistance even higher. The different timings and thresholds of ECE and ECI contribute to safety.

If an ECE is established and remains valid, then the communication device(s) can perform the OCD (508). The OCD preferably involves the detection of an appropriate optical connection via pulsed optical communication.

Fig. 7 is a timing diagram 700 illustrating timing relationships among electrical connection detection (ECE) and optical connection detection (OCD) portions of a connection establishment sequence.

The timing diagram illustrates the connection sequence for first and second devices (Device #1, Device #2). The perspective of Device #1 is illustrated in the top portion of the timing diagram. Device #1 power initially goes to H, and this is detected at Device #2 as indicated by the dotted arrow. Similarly, Device #2 power goes to H and this is detected during ECE at Device #1. Within a maximum of 2 seconds of valid and ongoing ECE conditions, the sequence progresses to OCD. However, as indicated in the Device #1 portion, an ECI detection may occur. As indicated in the timing diagram, here the Device #1 Detect level is illustrated as going from H to L. An ECI may be a badly deteriorated cable, a completely disconnected cable, or the like, and is detected when the predetermined conditions are met (e.g., <1.0V).

At this point, the OCD may have started (as illustrated) but regardless, the ongoing connection detection sequence terminates within the denoted time duration (e.g., 0.5msec), and the sequence restarts at ECE. First, the Device #1 Power goes to L, which is detected at Device #2. After a period of time, both Device #1 and Device #2 Power synchronously transition to H, and the normal connection detection sequence continues, firstly with ECE followed by OCD.

There are preferably four steps in OCD (508). The communication device is configured to observe the pulse width, period and duration of various pulses for a detection of a valid optical connection.

Step 1:
In the first step, the transmission channel(s) of the communication device output a first pulse signal. FIG. 6A illustrates an example of the pulse signal 600a, and Table 3 below lists the parameters.
Table 3 - parameters for pulse in step 1:

The pulse signal in step 1 is comparable to the pulse signals P11 and/or P21 previously described. On the transmission side, an optical transmitter transmits the pulses, and on the reception side, an optical receiver receives the pulses. The communication device includes circuitry for carrying out the pulse signal detection. As described above, this may involve a receiver unit having pulse signal detectors, in conjunction with a controller configured to check the timing of the pulses. This OCD functionality may be carried out by an integrated circuit configured to perform the pulse signal detection on behalf of a communication device in which the integrated circuit resides.

When the communication device detects at least a predetermined number of continuous pulses having the defined characteristics for step 1, the OCD proceeds to Step 2. Preferably, the detection of at least five (5) continuous pulses having the defined characteristics satisfies step 1. But the characteristics of the pulses and the number of pulses may vary as required by timing constraints, etc.
Step 2:
Once the pulses of Step 1 are detected, the OCD proceeds to Step 2. Step 2 involves two pulse signals respectively having different pulse widths. The first pulse signal has a first pulse width and the second pulse signal has a second pulse width that is different from the first pulse width. The first pulse signal is initially transmitted, followed by the second pulse signal. Although the pulse signals have different pulse widths, Step 2 of OCD is preferably arranged such that the duration of the detection period for the respective pulse signals is the same. That is, if the duration for detecting the first pulse signals is “T”, the duration for detecting the second pulse signals is also “T”, and the total duration for Step 2 is “2T”.

FIG. 6B illustrates an example of the pulse signal 600b, and Table 4 below lists the parameters.
Table 4 - parameters for pulses in step 2:

When the communication device detects at least a predetermined number of continuous pulses respectively having the defined characteristics for the pulse signals of step 2, the OCD proceeds to Step 3. Preferably, the detection of at least five (5) continuous pulses of the first pulse signal and then at least five (5) continuous pulses of the second pulse signal, according to the above-defined characteristics satisfies step 2. But again the characteristics of the pulses and the number of pulses may vary.
Step 3:
Once the pulses of Step 2 are detected, the OCD proceeds to Step 3. Step 3 involves a pulse signal having a pulse width as set forth in FIG. 6C and Table 5 below.
Table 5 - parameters for pulses in Step 3:

As evident from these characteristics, the pulse signal of Step 3 may be the same as the second pulse signal from Step 2 (i.e., the longer pulse width).

Similar to Step 1, when the communication device detects at least a predetermined number of continuous pulses having the defined characteristics for step 3, the OCD proceeds to Step 4. Preferably, the detection of at least five (5) continuous pulses having the defined characteristics satisfies step 3.
Step 4:
If the counterpart device is detected in Step 3 (within 2msec), then the system proceeds to the next sequence (ECC).

When any continuous pulses defined in Step 3 or no pulse are detected at any reception channels in the communication device, the device shall stop the output of the pulse signal of Step 3 signal from its transmission channels and complete OCD.

If any pulses are observed and any continuous Step 3 characteristic pulses are not detected within a time duration (e.g., 3msec), the Device shall stop the output of Step 3 pulses and make its power pin less than the ECI voltage (e.g., <1.0 V) for at least 150ms, and then apply more than the ECE voltage (e.g., >2.3V) in order to re-initiate ECE. This re-initiation can be attempted up to 2 times.

The detection connection sequence may be arranged to use 1msec, so it could take 2msec to perform Tx/Rx electrical communication.

Once OCD concludes, ECC (510) confirms lanes for transmission/reception, allocates links and pairings for further communications, and accommodates a locking-in of the link timing. Once ECC is completed the communication device is ready for data communication.

As depicted in FIG. 5 and FIG. 7, any failure of OCD or ECC may prompt re-initiation of the process at ECE. An ECE failure (ECI) prompts the repetition of the ECE process as described above.

Although description has been made by giving the example embodiments as mentioned above, the contents of the technology are not limited to the above-mentioned example embodiments and may be modified in a variety of ways.

For example, in the forgoing example embodiments, the communication device 10 transmits the optical signal with use of the single optical fiber 901, and the communication device 20 transmits the optical signal with use of the single optical fiber 902. However, this is non-limiting. For example, the communication device may transmit the optical signal with use of a plurality of optical fibers.

It is to be noted that effects described herein are merely exemplified and not limitative, and effects of the disclosure may be other effects or may further include other effects.

It is to be noted that the technology may have the following configurations.

(1) A communication device, including:
a communication unit that supplies a first signal to an optical transmitter and receives a second signal from an optical receiver, the optical transmitter transmitting an optical signal, and the optical receiver receiving an optical signal; and
a coupling detection unit that performs a first coupling detecting operation that involves detection of coupling to a communication partner with use of an electrical signal.

(2) The communication device according to (1),
wherein the communication unit supplies the first signal to start a second coupling detecting operation, after the coupling detection unit has detected the coupling in the first coupling detecting operation.

(3) The communication device according to (2),
wherein, during a term in which the communication unit performs the second coupling detecting operation,
the coupling detection unit continuously performs the first coupling detecting operation, and
the communication unit terminates the second coupling detecting operation, in a case in which the coupling detection unit has detected disconnection of the coupling in the first coupling detecting operation.

(4) The communication device according to (2) or (3),
wherein the communication unit terminates the second coupling detecting operation, in a case in which no coupling has been detected within predetermined time, in the second coupling detecting operation.

(5) The communication device according to any one of (2) to (4),
wherein the first signal includes a first pulse signal, and
the communication unit supplies the first pulse signal, in the second coupling detecting operation.

(6) The communication device according to (5),
wherein the second signal includes a second pulse signal, and
the communication unit receives the second pulse signal, in the second coupling detecting operation.

(7) The communication device according to (6),
wherein the first signal further includes a third pulse signal, and
the communication unit supplies a first mixed signal that includes the first pulse signal and the third pulse signal, after receiving the second pulse signal, in the second coupling detecting operation.

(8) The communication device according to (7),
wherein a pulse width of the third pulse signal is different from a pulse width of the first pulse signal.

(9) The communication device according to (7) or (8),
wherein the second signal further includes a fourth pulse signal, and
the communication unit receives a second mixed signal that includes the second pulse signal and the fourth pulse signal, after supplying the first pulse signal, in the second coupling detecting operation.

(10) The communication device according to (9),
wherein the communication unit supplies the third pulse signal, after receiving the second mixed signal, in the second coupling detecting operation.

(11)
The communication device according to (10),
wherein the communication unit receives the fourth pulse signal, after supplying the first mixed signal, in the second coupling detecting operation.

(12) The communication device according to (11),
wherein the communication unit terminates the second coupling detecting operation, after receiving the fourth pulse signal.

(13) The communication device according to (12),
wherein the first signal includes a data signal, and
the communication unit supplies the data signal, after terminating the second coupling detecting operation.

(14) A communication method, including:
performing a first coupling detecting operation that involves detection of coupling to a communication partner with use of an electrical signal; and
performing a second coupling detecting operation that involves detection of coupling to the communication partner with use of an optical signal, after the coupling has been detected in the first coupling detecting operation.

(15) A communication system, including:
a first communication device; and
a second communication device,
the first communication device including
a communication unit that supplies a first signal to an optical transmitter and receives a second signal from an optical receiver, the optical transmitter transmitting an optical signal to the second communication device, and the optical receiver receiving an optical signal transmitted from the second communication device, and
a coupling detection unit that performs a first coupling detecting operation that involves detection of coupling to the second communication device with use of an electrical signal.

(1A) A communication device comprising:
a communication unit configured for optical communication with an other communication device through an optical transmitter that transmits optical signals and an optical receiver that receives optical signals; and
a coupling detection unit that performs an electrical coupling detection using an electrical connection with the other communication device.

(2A) The communication device according to (1A), wherein the coupling detection unit is configured to perform an optical coupling detection that uses the optical communication, after the electrical coupling detection with the other communication device is confirmed.

(3A) The communication device according to (2A),
wherein, during the optical coupling detection,
the coupling detection unit continuously performs the electrical coupling detection, and
the optical coupling detection is terminated in a case in which a disconnection of the electrical connection is determined.

(4A) The communication device according to (2A), wherein the optical coupling detection is terminated in a case in which no coupling has been detected within a predetermined time in the optical coupling detection.

(5A) The communication device according to (2A), wherein the optical coupling detection comprises transmitting a pulse signal having a first pulse width to the other communication device, and confirming a receipt of a counterpart pulse signal having the first pulse width from the other communication device.

(6A) The communication device according to (2A), wherein the optical coupling detection comprises transmitting a combination of pulse signals respectively having a first pulse width and a second pulse width to the other communication device, and confirming a receipt of a counterpart combination of pulse signals having the first pulse width and the second pulse width from the other communication device.

(7A) The communication device according to (6A), wherein the first pulse width is different from the second pulse width.

(8A) The communication device according to (5A), wherein the optical coupling detection comprises transmitting a combination of pulse signals respectively having the first pulse width and a second pulse width to the other communication device, and confirming a receipt of a counterpart combination of pulse signals having the first pulse width and the second pulse width from the other communication device.

(9A) The communication device according to (8A), wherein the first pulse width is different from the second pulse width.

(10A) The communication device according to (8A), wherein the optical coupling detection comprises transmitting an additional pulse signal having the second pulse width to the other communication device, and confirming a receipt of a counterpart additional pulse signal having the second pulse width from the other communication device.

(11A) The communication device according to (5A), wherein the optical coupling detection comprises transmitting an additional pulse signal having a second pulse width to the other communication device, and confirming a receipt of a counterpart additional pulse signal having the second pulse width from the other communication device.

(12A) The communication device according to (2A), wherein the communication unit supplies a data signal after the confirmation of the electrical connection detection and a confirmation of the optical coupling detection.

(13A) An apparatus for a first communication device, the apparatus comprising:
a communication unit configured to accommodate optical communication with a second communication device through an optical transmitter that transmits optical signals to the second communication device and an optical receiver that receives optical signals from the second communication device; and
a coupling detection unit that performs an electrical coupling detection using an electrical connection between the first communication device and the second communication device.

(14A) The apparatus according to (13A), wherein the coupling detection unit is configured to perform an optical coupling detection that uses the optical communication, after the electrical coupling detection with the other communication device is confirmed.

(15A) The apparatus according to (14A),
wherein, during the optical coupling detection,
the coupling detection unit continuously performs the electrical coupling detection, and
the optical coupling detection is terminated in a case in which a disconnection of the electrical connection is determined.

(16A) The apparatus according to (14A), wherein the optical coupling detection is terminated in a case in which no coupling has been detected within a predetermined time in the optical coupling detection.

(17A) The apparatus according to (14A), wherein the optical coupling detection comprises transmitting a pulse signal having a first pulse width to the other communication device, and confirming a receipt of a counterpart pulse signal having the first pulse width from the other communication device.

(18A) The apparatus according to (14A), wherein the optical coupling detection comprises transmitting a combination of pulse signals respectively having a first pulse width and a second pulse width to the other communication device, and confirming a receipt of a counterpart combination of pulse signals having the first pulse width and the second pulse width from the other communication device.

(19A) The apparatus according to (14A), wherein the communication unit supplies a data signal after the confirmation of the electrical connection detection and a confirmation of the optical coupling detection.

(20A) A method for determining a connection between a first communication device and a second communication device, the method comprising:
performing an electrical coupling detection using an electrical connection between the first communication device and the second communication device; and
performing an optical coupling detection that uses an optical communication between the first communication device and the second communication device, after the electrical coupling detection between the first communication device and the second communication device is confirmed.

It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

1 communication system
10, 20 communication device
11, 21 connector
12, 22 optical transmitter
13, 23 optical receiver
14, 24 controller
15, 25 timer
30, 60 transmitter
31, 61 processor
32, 33, 62, 63 pulse signal generator
34, 64 selector
40, 70 receiver
41, 71 processor
42, 43, 72, 73 pulse signal detector
50, 80 coupling detector
51, 81 coupling signal transmitter
52, 82 coupling signal receiver
90 transmission cable
901, 902 optical fiber
911, 912 electrical wire
INF1, INF2 data
PW11, PW12 pulse width
P11, P12, P21, P22 pulse signal
SEL1, SEL2 control signal
S51, S81 coupling signal
Tlim time limit

Claims (20)

1. A communication device comprising:
   a communication unit configured for optical communication with an other communication device through an optical transmitter that transmits optical signals and an optical receiver that receives optical signals; and
   a coupling detection unit that performs an electrical coupling detection using an electrical connection with the other communication device.
   
2. The communication device according to claim 1, wherein the coupling detection unit is configured to perform an optical coupling detection that uses the optical communication, after the electrical coupling detection with the other communication device is confirmed.
   
3. The communication device according to claim 2,
   wherein, during the optical coupling detection,
   the coupling detection unit continuously performs the electrical coupling detection, and
   the optical coupling detection is terminated in a case in which a disconnection of the electrical connection is determined.
   
4. The communication device according to claim 2, wherein the optical coupling detection is terminated in a case in which no coupling has been detected within a predetermined time in the optical coupling detection.
   
5. The communication device according to claim 2, wherein the optical coupling detection comprises transmitting a pulse signal having a first pulse width to the other communication device, and confirming a receipt of a counterpart pulse signal having the first pulse width from the other communication device.
   
6. The communication device according to claim 2, wherein the optical coupling detection comprises transmitting a combination of pulse signals respectively having a first pulse width and a second pulse width to the other communication device, and confirming a receipt of a counterpart combination of pulse signals having the first pulse width and the second pulse width from the other communication device.
   
7. The communication device according to claim 6, wherein the first pulse width is different from the second pulse width.
   
8. The communication device according to claim 5, wherein the optical coupling detection comprises transmitting a combination of pulse signals respectively having the first pulse width and a second pulse width to the other communication device, and confirming a receipt of a counterpart combination of pulse signals having the first pulse width and the second pulse width from the other communication device.
   
9. The communication device according to claim 8, wherein the first pulse width is different from the second pulse width.
   
10. The communication device according to claim 8, wherein the optical coupling detection comprises transmitting an additional pulse signal having the second pulse width to the other communication device, and confirming a receipt of a counterpart additional pulse signal having the second pulse width from the other communication device.
    
11. The communication device according to claim 5, wherein the optical coupling detection comprises transmitting an additional pulse signal having a second pulse width to the other communication device, and confirming a receipt of a counterpart additional pulse signal having the second pulse width from the other communication device.
    
12. The communication device according to claim 2, wherein the communication unit supplies a data signal after the confirmation of the electrical connection detection and a confirmation of the optical coupling detection.
    
13. An apparatus for a first communication device, the apparatus comprising:
    a communication unit configured to accommodate optical communication with a second communication device through an optical transmitter that transmits optical signals to the second communication device and an optical receiver that receives optical signals from the second communication device; and
    a coupling detection unit that performs an electrical coupling detection using an electrical connection between the first communication device and the second communication device.
    
14. The apparatus according to claim 13, wherein the coupling detection unit is configured to perform an optical coupling detection that uses the optical communication, after the electrical coupling detection with the other communication device is confirmed.
    
15. The apparatus according to claim 14,
    wherein, during the optical coupling detection,
    the coupling detection unit continuously performs the electrical coupling detection, and
    the optical coupling detection is terminated in a case in which a disconnection of the electrical connection is determined.
    
16. The apparatus according to claim 14, wherein the optical coupling detection is terminated in a case in which no coupling has been detected within a predetermined time in the optical coupling detection.
    
17. The apparatus according to claim 14, wherein the optical coupling detection comprises transmitting a pulse signal having a first pulse width to the other communication device, and confirming a receipt of a counterpart pulse signal having the first pulse width from the other communication device.
    
18. The apparatus according to claim 14, wherein the optical coupling detection comprises transmitting a combination of pulse signals respectively having a first pulse width and a second pulse width to the other communication device, and confirming a receipt of a counterpart combination of pulse signals having the first pulse width and the second pulse width from the other communication device.
    
19. The apparatus according to claim 14, wherein the communication unit supplies a data signal after the confirmation of the electrical connection detection and a confirmation of the optical coupling detection.
    
20. A method for determining a connection between a first communication device and a second communication device, the method comprising:
    performing an electrical coupling detection using an electrical connection between the first communication device and the second communication device; and
    performing an optical coupling detection that uses an optical communication between the first communication device and the second communication device, after the electrical coupling detection between the first communication device and the second communication device is confirmed.

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