WO2009107702A1 - Light transmission system, light relay device, light relay device control method and program - Google Patents

Abstract

Provided is a light transmission system including: a light relay device (12) which amplifies light transmitted from a plurality of subscriber terminal devices (ONU #1 to #n); a terminal device (16) having an excitation light source which generates an excitation light for controlling the gain of the light relay device (12); and a control device (OLT 14) which controls the terminal device (16) so as to transmit the excitation light at the timing when the excitation light is superposed by an optical signal transmitted from the respective subscriber terminal devices.

Description

Optical transmission system, optical repeater, control method of optical repeater, and program

The present invention relates to an optical transmission system such as a PON (Passive Optical Network), an optical repeater, a control method of an optical repeater, and a program for causing a computer to execute the method.

The PON system is an economical system in which a transmission line fiber and a central office side terminal (OLT: Optical Line Terminal) can be shared by a plurality of subscribers. In order to improve its economics, the number of allowable branches of splitters is increased in dense urban areas of subscribers, and the distance between OLT and subscriber network unit (ONU: Optical Network Unit) is increased in sparse sparsely populated areas of subscribers. Is required.

Although repeaters are provided to cope with so-called high loss and long distance, the repeaters include 3R (Reshaping, Retiming, Regenerating) repeaters and an optical repeater. The 3R repeater converts an optical signal into an electrical signal, regenerates a clock from the electrical signal, and converts the electrical signal, which has been subjected to identification regeneration with the regenerated clock, into an optical signal again. Optical repeaters use optical amplifiers that use stimulated emission to amplify the signal as it is. The 3R relay is a technology that can be reliably realized because it is only necessary to configure the receiving unit of the OLT and the transmitting unit of the ONU, but there are problems such as large size, high cost, and reliance on bit rate. Although the optical repeater solves the problems of the 3R repeater, the technical hurdles are high in that the optical repeater is compatible with the burst signal.

In the PON system, since the signal (downlink) from the OLT to the ONU is a general continuous light, it is possible to apply the optical repeater used in the backbone system optical network. However, in the signal from the ONU to the OLT (uplink), it is a so-called burst signal in which each ONU sequentially transmits a signal at a predetermined interval (guard time). Since the distance between the OLT and each ONU is different, the signal light power input to the optical repeater changes at high speed within the range of the input dynamic range. For this purpose, in order to keep the output of the optical repeater constant, the gain of the optical amplifier must be changed at high speed corresponding to the burst.

In an ordinary optical repeater, so-called AGC (Automatic Gain Control) control is generally performed to monitor the output power of the optical repeater and apply feedback to the gain so that it becomes constant. An example of the optical power equivalent device is disclosed in Japanese Patent Laid-Open No. 2005-6313. In the optical power equivalent device disclosed in this document, the intensity of the optical signal input to the optical amplifier is measured, and the time required to obtain the gain necessary to make the output of the optical amplifier constant, that is, the necessary pumping light A scheme is employed in which the optical signal is delayed by the time required to output the intensity.

However, in the general feedback control described above, when there is no input, the gain is controlled to be maximized in an attempt to increase the output, but at that time, if a signal is rapidly input, the AGC control delay is It causes the light surge that is the cause.

An example of the object of the present invention is an optical transmission system capable of effectively preventing an optical surge even under high-speed input fluctuations such as burst signals, an optical repeater, a method of controlling an optical repeater, and a method for causing a computer to execute the method. To provide the program.

An optical transmission system according to one aspect of the present invention includes an optical repeater that amplifies optical signals received from a plurality of subscriber terminals, and an excitation light source that generates excitation light for controlling the gain of the optical repeater. The apparatus includes a control device that controls the terminal device to transmit the excitation light transmitted from the terminal device at the timing when it overlaps with the light signal transmitted from each subscriber terminal device.

Further, an optical repeater according to one aspect of the present invention is an optical repeater optically connected between a plurality of subscriber terminals and a controller, and an optical signal received from the plurality of subscriber terminals From each of the plurality of subscriber terminal devices according to the instruction from the control device, an optical amplification means for amplifying and outputting to the control device, an excitation light generation means for generating excitation light for controlling the gain of the optical amplification means, And control means for transmitting the excitation light to the optical amplification means at a timing overlapping with the input optical signal.

Further, a control method of an optical repeater according to one aspect of the present invention is a control method of an optical repeater for amplifying an optical signal received from a plurality of subscriber terminal apparatuses, which is for controlling the gain of the optical repeater. The intensity of the excitation light is set for each of the optical signals sent from the subscriber terminal, and the excitation light is generated at a timing that overlaps with the optical signal sent from the subscriber terminal.

Furthermore, a program according to one aspect of the present invention is a program for causing a computer that controls an optical repeater that amplifies optical signals sent from a plurality of subscriber terminals to be executed, and controlling the gain of the optical repeater. Setting the intensity of the excitation light for each optical signal sent from the subscriber terminal, and causing the computer to perform processing for causing the optical repeater to generate the excitation light at a timing overlapping with the optical signal sent from the subscriber terminal It is made to run.

FIG. 1 is a block diagram showing the configuration of a PON system using an optical repeater according to an embodiment of the present invention. FIG. 2A is a block diagram showing an example of an OLT in the first embodiment. FIG. 2B is a block diagram showing an example of ONU # 0 in the first embodiment. FIG. 3 is a sequence diagram showing a general discovery process. FIG. 4A is a flowchart showing an excitation light control process of the OLT in the first embodiment. FIG. 4B is a flowchart showing an operation of the ONU # 0 in the first embodiment. FIG. 5A is a time chart showing existing excitation timings and idle time slots. FIG. 5B is a time chart schematically showing the excitation light intensity adjusted by the vacant time slot. FIG. 6 is a sequence diagram showing an example of the excitation timing eT # i and the transmission timing eT # i in the first embodiment. FIG. 7A is a time chart showing an example of the excitation light control method according to the second embodiment. FIG. 7B is a time chart showing an example of the excitation light control method according to the third embodiment. FIG. 7C is a time chart showing an example of the excitation light control method according to the fourth embodiment.

Explanation of sign

10 optical splitter 11 optical coupler 12 upstream optical repeater 13 optical coupler 14 OLT
15 downstream optical repeater 16 terminal device having excitation light source (ONU # 0)
DESCRIPTION OF SYMBOLS 101 Optical coupler 102 Photoelectric converter 103 CDR / DMUX
104 processing unit 105 excitation light power setting unit 106 scheduler 107 MUX
108 driver 109 light source 201 optical coupler 202 photoelectric converter 203 CDR / DMUX
204 processing unit 205 MUX
206 driver 207 light source 208 excitation light source

As an example of an optical transmission system to which the present invention is applied, a PON system in which a plurality of subscriber terminal units ONU # 1 to #n and a central office side terminal OLT as a control device are connected through an optical splitter and an optical repeater. Now, the present invention will be described in detail.

An optical transmission system according to an embodiment of the present invention will be described.

In the optical transmission system according to one embodiment of the present invention, a terminal unit ONU # 0 having an excitation light source is provided separately from the plurality of subscriber terminal units ONU # 1 to ONU # n. Under control of the OLT, the ONU # 0 outputs excitation light of corresponding intensities at timings overlapping with respective upstream optical signals from the ONUs # 1 to #n, whereby each upstream optical signal input to the OLT Keep the power of

Normally, when an ONU is newly connected to the PON system, a registration procedure called Discovery Process is performed with the OLT. At that time, by measuring the delay time ΔT between each ONU and the OLT, the OLT separates the transmission start time by leaving a fixed interval (guard time) so that the data (uplink signal) from each ONU does not collide. Allocate transmission time.

According to this embodiment, the process of measuring the power of the optical signal input from each ONU to the OLT, and calculating the respective gains so as to keep the output power of the optical repeater constant is added.

The OLT notifies each ONU # 1 to #n of the transmission start time and the transmission time, but at the same time, the ONU # 0 has a constant optical repeater output at a timing overlapping with the signal from each ONU. The optical repeater is notified to output the excitation light with the excitation light power at which the gain is obtained. As a result, the gain corresponding to each ONU in the upstream optical repeater is set at high speed by feed forward, so that amplification is performed without any transient response (light surge) in the burst signal in the PON system in which the signal light level changes rapidly. It becomes possible.

Furthermore, as described later, the transmission order from each ONU is set according to the gain, and the pump light in the guard time is complemented by the pump light intensity before and after that, thereby making the gain change of the optical repeater smooth. It is also possible to reduce the optical surge due to the delay of the population inversion density of the optical amplifier.

Thus, according to one embodiment of the present invention, the gain at the optical repeater can be changed at high speed by feedforward, so that it can be used only in a conventional optical repeater including a gain adjustment (AGC) circuit for feedback. It is possible to prevent the optical surge due to the delay of the AGC circuit being Furthermore, by smoothing the gain change of the optical repeater, it is possible to reduce the optical surge caused by the delay of the reverse distribution density of the optical amplifier. Hereinafter, examples of the present invention will be described in detail.

(First embodiment)
1) Configuration FIG. 1 is a block diagram showing the configuration of a PON system using an optical repeater according to an embodiment of the present invention. Here, the upstream optical signals respectively output from the n subscriber terminal units ONU # 1 to #n are transmitted through the optical splitter 10, the optical coupler 11, the upstream optical repeater 12, and the optical coupler 13 to a central office side terminal (OLT ) Is transmitted.

Further, the downstream optical signal from the OLT 14 is transmitted to the n subscriber terminal units ONU # 1 to #n through the optical coupler 13, the downstream optical repeater 15, the optical coupler 11 and the optical splitter 10. The OLT 14 is basically a control device having a receiving unit, a transmitting unit, and a processing unit in the present embodiment (details will be described later). The upstream optical repeater 12 and the downstream optical repeater 15 have an optical amplifier that amplifies the signal as it is by using stimulated emission.

Furthermore, a terminal device 16 having an excitation light source (hereinafter referred to as ONU # 0) is connected to the optical coupler 11, and excitation light for changing the gain of the upstream optical repeater 12 according to the control of the OLT 14 as described later. Output. The ONU # 0 basically has a receiving unit, a transmitting unit, an excitation light source, and a processing unit, and the details will be described later. The ONU # 0 has basically the same configuration as the subscriber terminal units ONU # 1 to #n except for the excitation light source, and the delay process ΔT # 0 is first at first by the discovery process with the OLT 14 as well. It is measured.

The optical repeater according to the present embodiment includes the optical coupler 11, the upstream optical repeater 12, the optical coupler 13, the downstream optical repeater 15, and the ONU # 0 (broken line portion). The optical coupler 11, the upstream optical repeater 12, the optical coupler 13 and the downstream optical repeater 15 may be one optical repeater, and the ONU # 0 may be connected to the optical splitter 10 and provided on the subscriber side.

Uplink optical signals output at respective timings from n subscriber terminal units ONU # 1 to #n are amplified by being input to the upstream optical repeater 12 at the same timing as excitation light from ONU # 0. , And output to the OLT 14 with substantially constant power.

FIG. 2A is a block diagram showing an example of an OLT in the present embodiment. The optical signal input to the photoelectric converter 102 via the optical coupler 101 is converted into an electrical signal by the photoelectric converter 102, and is input to the CDR / DMUX 103. The photoelectric converter 102 is, for example, a photodiode (PD). The CDR / DMUX 103 regenerates clock and data from the output signal of the photoelectric converter 102 (CDR), performs parallel conversion (DMUX), and outputs a low-speed reception signal to the processing unit 104.

The OLT 14 in the present embodiment further includes a pumping light power setting unit 105 and a scheduler 106. The processing unit 104 controls the excitation light power setting unit 105 and the scheduler 106 while monitoring the input power output from the photoelectric converter 102 and the synchronization error output from the CDR / DMUX 103 as described later. The necessary excitation light power is calculated, and the output timing of the excitation light for each upstream optical signal is calculated.

The low speed data output from the processing unit 104 is serial converted by the MUX 107, and the driver 108 drives the light source 109 according to the high speed data to generate a transmission light signal, and the generated signal is transmitted through the optical coupler 101. Be done. The light source 109 is, for example, a laser diode (LD).

The processing unit 104 also executes processing of the main signal including generation / analysis of the preamble of the transmission / reception signal, monitoring of each device, management of an alarm, and the like. In addition, although the types of the light source 109, the driver 108 and the photoelectric converter 102 may be different between the OLT 14 and the ONU, the basic configuration is the same. Also, the CDR / DMUX 103 and the MUX 107 may be supplied on separate chips, or may be supplied on one chip. Furthermore, the light source 109 and the driver 108 may be an integral module, and are not limited to the configuration of FIG. 2A.

In addition, the processing unit 104, the excitation light power setting unit 105, and the scheduler 106 implement functions equivalent to the functions described in the present embodiment by causing a program control processor such as a CPU to execute a program.

FIG. 2B is a block diagram showing an example of the ONU # 0 in this embodiment. The optical signal input to the photoelectric converter 202 via the optical coupler 201 is converted into an electrical signal by the photoelectric converter 202, and is input to the CDR / DMUX 203. The photoelectric converter 202 is, for example, a photodiode (PD). The CDR / DMUX 203 recovers clock and data from the output signal of the photoelectric converter 202 (CDR), performs parallel conversion (DMUX), and outputs a low-speed reception signal to the processing unit 204.

The low speed data output from the processing unit 204 is serial converted by the MUX 205, and the driver 206 drives the light source 207 according to the high speed data to generate a transmission light signal, and the generated signal is transmitted through the optical coupler 201. Be done. The light source 207 is, for example, a laser diode (LD). In this way, ONU # 0 becomes capable of bi-directional communication with the OLT 14. The processing unit 204 also executes main signal processing including generation / analysis of preambles of transmission / reception signals, monitoring of each device, management of alarms, and the like.

The ONU # 0 in the present embodiment further includes the excitation light source 208. The processing unit 204 controls the excitation light source 208 according to an instruction from the OLT 14, and the excitation light source 208 sends out the excitation light through the optical coupler 201 at the instructed intensity and transmission timing of the excitation light. The processing unit 204 corresponds to control means in the ONU # 0.

Note that the CDR / DMUX 203 and the MUX 205 may be supplied on separate chips, or may be supplied on one chip. Furthermore, the light source 207 and the driver 206 may be an integral module, and are not limited to the configuration of FIG. 2B.

2) Discovery Process As described above, the delay process ΔT between the OLT and ONU is measured by the discovery process. In this embodiment, since the measured delay time ΔT is used to determine the excitation light transmission timing, the discovery process will be briefly described.

FIG. 3 is a sequence diagram showing a general discovery process. Here, the discovery process in Ethernet PON (EPON) (however, Ethernet is a registered trademark) will be described.

If ONU # i (i is an arbitrary value of 1 to n) is newly added to the PON system, a discovery process is performed. First, the OLT 14 transmits a Discovery Gate command including the local time T1 of the OLT 14 and OLT information. When ONU #i receives the Discovery Gate command, ONU #i sets the built-in clock to time T1, and sends a Register_Request command including transmission time T2 of ONU #i toward OLT 14 after a lapse of random time.

Assuming that the OLT 14 receives the Register_Request command at time T3, the processing unit 104 of the OLT 14 calculates and stores the delay time ΔT # i with the ONU #i from the time information of T1, T2 and T3. Then, the OLT 14 assigns a Logical Link Identifier (LLID) to the ONU #i, and a Register command for notifying the LL ID to the ONU #i, and a GATE command including a transmission start time T5 and a transmission time L. Send each

When ONU # i receives the Register and GATE commands, the ONU # i transmits the Register_ACK command with LLID set to the OLT 14 during a lapse of L time from the designated time T5 to notify the LLID to the OLT 14, thereby the ONU # i's registration procedure is complete.

If ONU #i does not receive the Register command despite sending the Register_Request command, it retransmits the Register_Request command. As a result, initial communication in the upstream direction is realized, and measurement of the delay time ΔT # i between the OLT 14 and the ONU # i becomes possible.

However, the delay time ΔT # 0 with the ONU # 0 needs to be performed first at the start of the PON system in the same process as described above.

3) Pumping light control When the dynamic range of the upstream optical repeater 12 shown in FIG. 1 is narrower than or equal to the dynamic range of the OLT 14, the transmission loss between the upstream optical repeater 12 and the upstream optical repeater 12 and the OLT 14 is The initial communication (discovery process) is feasible if it has a gain of minutes as a fixed value. In this case, although the output power of the optical repeater 12 is not constant, the upstream signals from the ONUs # 1 to #n are received within the dynamic range of the OLT 14, so initial communication is possible.

However, when the dynamic range of the upstream optical repeater 12 is wider than the dynamic range of the OLT 14, the gain of the upstream optical repeater 12 is set to the optical repeater 12 and the OLT 14 so that an optical signal exceeding the dynamic range of the OLT 14 is not input. It is necessary to keep it smaller than the transmission loss during the However, in this case, the upstream optical signals from the other ONUs fall below the dynamic range of the OLT 14 and the signals from the other ONUs do not reach the OLT 14 and there is a possibility that the initial communication can not be realized.

Therefore, the OLT 14 performs excitation light control by monitoring the presence or absence of input power and synchronization. Hereinafter, excitation light control according to the present embodiment will be described in detail with reference to FIGS. 4A to 6.

FIG. 4A is a flow chart showing the excitation light control process of the OLT according to the present embodiment, and FIG. 4B is a flow chart showing the operation of ONU # 0. FIG. 5A is a time chart showing the existing excitation timing and the vacant time slot, and FIG. 5B is a time chart schematically showing the excitation light intensity adjusted by the vacant time slot.

Hereinafter, as shown in FIG. 5A, it is assumed that the ONUs # 1 and # 2 have already been registered in the OLT 14, and the excitation timing from the ONU # 0 has been determined. In this state, it is assumed that ONU #n is newly added. In FIGS. 5A and 5B, excitation light # 1 is for the optical signal of ONU # 1, and excitation light # 2 is for the optical signal of ONU # 2.

In FIG. 4A, the processing unit 104 of the OLT 14 monitors the input power detection output from the photoelectric converter 102 to detect an optical input (step 301). If there is an optical input, whether the power is equal to or higher than a certain level It is determined whether or not (step 302).

If the input light is equal to or higher than a predetermined level (step 302: YES), the processing unit 104 determines whether synchronization has been established in the CDR / DMUX 103 (step 303). If synchronization is not achieved (step 303: YES), the processing unit 104 reaches a level at which the signal can be correctly received by the OLT 14 because the ONU #n is newly added but the gain in the upstream optical repeater 12 is small. The excitation light power setting unit 105 calculates the excitation light intensity (P # n) necessary to amplify from the power received by the photoelectric converter 102 to the predetermined power that can be correctly received (step 304). .

Subsequently, the scheduler 106 of the OLT 14 determines the excitation timing eT # n corresponding to the ONU # n in a vacant time slot other than the excitation timing corresponding to the already operating ONU # 1, # 2, and so on. Then, as shown in FIG. 5B, the OLT 14 transmits a transmission timing T # n to the ONU # n, and a control signal including an instruction to raise the excitation light to the ONU # 0 to the intensity P # n at the excitation timing eT # n. Is sent (step 305).

Thus, by adjusting the excitation light intensity at time slots other than the excitation timing corresponding to the existing ONU # 1, # 2, etc., the discovery process is executed with the ONU #n that has not reached the reception level. (Step 306).

The control signal addressed to the ONU # 0 is sent out as an optical signal from the light source 109, amplified by the downstream optical repeater 15, and reaches the ONU # 0 through the optical coupler 11.

In FIG. 4B, the processing unit 204 of ONU # 0 determines the presence or absence of the control signal from the OLT 14 (step 401), and when the control signal is received, the excitation timing (here, eT # n) and excitation included in the instruction are received. The light intensity (here, P # n) is set (step 402). Every time the excitation timing eT # i including the excitation timing eT # n set in this way is reached (Step 403: YES), the excitation light source 208 is driven with the set excitation light intensity P # i to transmit excitation light (Step 404). Hereinafter, specific examples of the excitation timing eT # i and the transmission timing eT # i will be described.

FIG. 6 is a sequence diagram showing an example of the excitation timing eT # i and the transmission timing eT # i in this embodiment. Here, it is assumed that the delay time ΔT # n of ONU # n and the delay time ΔT # 0 of ONU # 0 have already been calculated and stored in the discovery process.

The OLT 14 transmits a GATE command (transmission start time T6, transmission time L) to the ONU # n, and at the same time, transmits a GATE command (excitation start time [T6 + ΔT # n-ΔT # 0] to the ONU # 0, excitation time L, excitation light Send the strength P # n). The ONU #n that has received the GATE command (T6, L) transmits an LLID # n MAC frame of time L at time T6. Upon receiving the GATE command (T6 + .DELTA.T # n-.DELTA.T # 0, L, P # n), ONU # 0 excites the excitation light intensity P # n for a time L at time [T6 + .DELTA.T # n-.DELTA.T # 0] (CW) Send light As described above, the excitation light transmitted by ONU # 0 at time [T6 + ΔT # n-ΔT # 0] is incident on upstream optical repeater 12 at the timing when it overlaps with the LLID # n MAC frame transmitted by ONU # n at time T6. Do. By this, the gain according to the attenuation amount from the ONU #n to the upstream optical repeater 12 is set in the optical repeater 12 by feedforward. By this, it is possible to prevent the optical surge caused by the delay of feedback gain adjustment (AGC) which is observed in a general optical repeater.

After the discovery process, each ONU calculates the amount of frames it wants to transmit and notifies the OLT 14 using the Report command. The OLT 14 assembles the transmission order of Gate commands in accordance with the Report request from each ONU and the algorithm for bandwidth allocation (DBA: Dynamic Bandwidth Allocation), and sequentially transmits Gate commands to the ONU. Also send GATE command. The output of the optical repeater 12 is obtained by entering the upstream optical repeater 12 at the timing when the excitation light from the ONU # 0 and the upstream optical signal from each ONU overlap while considering the delay time in the same manner as described above. It can be made constant without light surge.

4) As described above, according to this embodiment, the gain in the optical repeater 12 can be changed at high speed by feed forward. For this reason, it is possible to effectively prevent the optical surge due to the delay of the AGC circuit with respect to the high speed input level fluctuation observed in the ordinary optical repeater.

Second Embodiment
In the first embodiment described above, the excitation light is turned ON / OFF so that the timing is overlapped with the upstream optical signal, but the present invention is not limited to this, and the excitation light may be complemented between time slots. Is also possible.

FIG. 7A is a time chart showing an example of the excitation light control method according to the second embodiment of the present invention. Here, the excitation light time slots of the ONUs # 1 to # 4 are set, but the processing unit 204 continuously transmits the excitation light from the ONU # 0 also in the complementary regions 501 to 503 thereof. By continuously changing the pumping light in this manner, it is possible to suppress a sudden change in gain and to reduce an optical surge caused by the delay of the population inversion density of the optical amplifier in the optical repeater 12. As a result, even when the timing of the upstream signal light and the timing of the excitation light deviate, it is possible to prevent the absence of signal light.

Third Embodiment
FIG. 7B is a time chart showing an example of the excitation light control method according to the third embodiment of the present invention. Here, the rapid change in the gain is suppressed by arranging the transmission order from the ONUs # 1 to # 4 in the order of the gain in the upstream optical repeater 12. The transmission order is set by the scheduler 106 in the order of the excitation light intensity (gain) set by the excitation light power setting unit 105 of the OLT 14. In the example shown to FIG. 7B, although arranged in the ascending order of the gain in the upstream optical repeater 12, you may be descending order.

Furthermore, as in the second embodiment described above, the processing unit 204 also performs excitation from ONU # 0 also in the complementary regions 601 to 603 of the respective excitation light time slots of ONUs # 1 to # 4 arranged in ascending order of gain. Light is sent out continuously. Thus, by changing the pumping light to be successively smaller (or larger) continuously, an abrupt change in gain can be suppressed, and an optical surge caused by the delay of the population inversion density of the optical amplifier in the optical repeater 12 can be obtained. Can be reduced. As a result, even when the timings of the upstream signal light and the excitation light are shifted, it is possible to prevent the absence of signal light.

Fourth Embodiment
FIG. 7C is a time chart showing an example of the excitation light control method according to the fourth embodiment of the present invention. As in the second embodiment described above, the excitation light time slots of the ONUs # 1 to # 4 are set, but the excitation light is continuously transmitted from the ONU # 0 also in the complementary regions 701 to 703 thereof. Let

Furthermore, in the fourth embodiment, the guard time is set long when the gain difference between the signals from the ONUs is equal to or greater than a predetermined value. Here, assuming that the intensity difference between the excitation light for ONU # 3 and the excitation light for subsequent ONU # 1 is equal to or greater than a predetermined value, the processing unit 204 lengthens the guard time between them. Therefore, the change of the pump light in the complementary region 703 between the pump lights # 3 and # 1 becomes more gradual, the rapid change of the gain is suppressed, and the light surge due to the delay of the population inversion density of the optical amplifier is reduced. Be done.

As an example of the effect of the present invention, light surge can be prevented even under high-speed input fluctuations such as burst signals.

In addition, although the optical amplifier of the optical repeater generally forms a population inversion by excitation light and amplifies an optical signal by stimulated emission, a light surge occurs due to a response delay of the population inversion density. It will On the other hand, in the present embodiment, the transmission order from each ONU is set according to the gain, and the excitation light in the guard time is complemented by the excitation light intensities before and after that. Therefore, as an example of the effect of the present invention, it is possible to smooth the gain change of the optical repeater and reduce the light surge caused by the delay of the population inversion density of the optical amplifier.

The present invention is applicable to an optical repeater in a PON system.

Although the present invention has been described above with reference to the embodiments and the examples, the present invention is not limited to the above embodiments and the examples. The configurations and details of the present invention can be modified in various ways that can be understood by those skilled in the art within the scope of the present invention.

This application incorporates all the contents of Japanese Patent Application No. 2008-047137 filed on February 28, 2008, and claims priority based on this Japanese application.

Claims (18)

An optical repeater for amplifying optical signals received from a plurality of subscriber terminals;
A terminal device including an excitation light source generating excitation light for controlling the gain of the optical repeater;
A control device that controls the terminal device to transmit the excitation light transmitted from the terminal device at a timing overlapping the light signal transmitted from each subscriber terminal device;
Optical transmission system. The terminal device is
The optical transmission system according to claim 1, wherein the intensity of excitation light, the transmission start time and the transmission time are determined by an instruction from the control device. The controller is
The intensity of the excitation light emitted from the terminal unit is determined for each optical signal transmitted from the subscriber terminal unit in order to make the output of the optical repeater constant. The optical transmission system described in. The controller is
If the optical signal of a predetermined level is detected in the input signal received from the optical repeater and synchronization with the input signal is not received, the terminal is instructed to increase the gain in time slots other than the already set time slots. The optical transmission system according to any one of claims 1 to 3, which is output to a device. The optical transmission system according to any one of claims 1 to 4, wherein the terminal device changes the generated excitation light continuously. The terminal device is
The optical transmission system according to any one of claims 1 to 5, wherein the transmission order of the optical signals transmitted from the plurality of subscriber terminal devices is set in the order of gain in the optical repeater. The terminal device is
When the gain difference in the optical repeater is greater than or equal to a predetermined value among the signals transmitted from the plurality of subscriber terminal devices, the transmission interval of the optical signals transmitted from the plurality of subscriber terminal devices is increased. The optical transmission system according to claim 5 or 6. An optical repeater optically connected between a plurality of subscriber terminals and a controller,
Optical amplification means for amplifying optical signals received from the plurality of subscriber terminal devices and outputting the amplified optical signals to the control device;
Excitation light generating means for generating excitation light for controlling the gain of the optical amplification means;
Control means for transmitting the excitation light to the light amplification means at a timing overlapping the light signal input from each of the plurality of subscriber terminal devices according to an instruction from the control device;
An optical repeater having The control means
9. The optical repeater according to claim 8, wherein the intensity of excitation light, the transmission start time and the transmission time are determined by an instruction from the controller. The intensity of the excitation light is determined for each of the optical signals transmitted from the subscriber terminal device by the control device in order to make the signal transmitted from the optical amplification means have a constant output. Or the optical repeater according to claim 9. The optical relay apparatus according to any one of claims 8 to 10, wherein the control means changes the excitation light continuously. A control method of an optical repeater for amplifying an optical signal received from a plurality of subscriber terminals, comprising:
Setting the intensity of excitation light for controlling the gain of the optical repeater for each optical signal transmitted from the subscriber terminal;
The control method of the optical repeater which generates the said excitation light at the timing which overlaps with the optical signal sent from the said subscriber terminal device. The control method of the optical repeater according to claim 12, wherein the intensity of the excitation light is determined for each of the optical signals sent from the subscriber terminal device in order to make the output of the optical repeater constant. The side receiving the input signal sent from the optical repeater detects an optical input of a predetermined level by the input signal, and if it can not synchronize with the input signal, a time other than the time slot already set. The control method of the optical repeater according to claim 12 or 13, wherein the timing is set in a slot. The control method of the optical repeater according to any one of claims 12 to 14, wherein the excitation light is continuously changed. The optical repeater according to any one of claims 12 to 15, wherein the transmission order of optical signals transmitted from the plurality of subscriber terminal devices is set in the order of gain in the optical repeater. Control method. When the gain difference in the optical repeater is greater than or equal to a predetermined value among the signals transmitted from the plurality of subscriber terminal devices, the transmission interval of the optical signals transmitted from the plurality of subscriber terminal devices is increased. The control method of the optical repeater according to claim 15 or 16. A program for causing a computer that controls an optical repeater that amplifies optical signals sent from a plurality of subscriber terminals to execute.
Setting the intensity of excitation light for controlling the gain of the optical repeater for each optical signal transmitted from the subscriber terminal;
A program for causing the computer to execute a process of causing the optical repeater to generate the excitation light at a timing overlapping with an optical signal transmitted from the subscriber terminal device.

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