WO2022095077A1 - Optical carrier terahertz wave/millimeter wave generation system and method, and transmitter - Google Patents

Abstract

Provided are an optical carrier terahertz wave/millimeter wave generation system, comprising an optical wave generator and integrated intensity modulators. The optical wave generator generates a preset number of coherent optical comb teeth. Each integrated intensity modulator is configured to receive the preset number of coherent optical comb teeth generated by the optical wave generator, and modulate the received coherent optical comb teeth by using data and a local oscillator frequency, so as to generate a modulated signal. Further provided are a transmitter for optical communication, and an optical carrier terahertz wave/millimeter wave generation method.

Description

Optical carrier terahertz wave/millimeter wave generation system and method, transmitter technical field

The present invention relates to communication technology, and more particularly, to a light-borne terahertz wave/millimeter wave generation technology and a transmitter for optical communication.

Background technique

With the explosive growth of mobile data traffic, low-frequency spectrum resources are becoming increasingly scarce. Wireless communication carrier frequencies are beginning to evolve towards millimeter waves in the frequency range of 30GHz to 300GHz and terahertz (THz) bands in the frequency range up to 100GHz to 10THz.

Due to the high frequency and large bandwidth of terahertz waves, its related technologies are considered to be important candidate technologies for future 6G mobile communications. Traditional electronics-based all-solid-state terahertz wave generation systems are limited in frequency and bandwidth by electronic bottlenecks. In order to break through these electronic bottlenecks, the researchers proposed a photonics-based terahertz wave generation scheme.

According to the different light sources used in the system, the light-borne terahertz wave generation schemes can generally be divided into two categories: schemes based on dual lasers and schemes based on optical frequency combs. For now, no matter which scheme is adopted, there is a problem of phase noise.

Phase noise will deteriorate the signal-to-noise ratio of the signal at the receiving end, resulting in serious bit errors. It is possible to use digital signal processing (DSP) algorithm to compensate phase noise, but DSP algorithm will bring greater power consumption and delay, and DSP algorithm needs to collect data for processing. This makes the use of DSP algorithms to compensate for phase noise inapplicable in many scenarios, for example, in scenarios with particularly large data streams such as 3D-Full-HD TV and S-HDTV.

Therefore, it is necessary to improve the way of generating terahertz waves.

SUMMARY OF THE INVENTION

In view of this, the present application provides an improved light-borne terahertz wave/millimeter wave generation system. The light-borne terahertz wave/millimeter wave generation system includes a light wave generator configured to generate a preset number of coherent optical combs; an integrated intensity modulator configured to receive the light generated by the light wave generator A preset number of coherent optical comb teeth are modulated with data and local oscillator frequencies to generate a modulation signal.

According to the optical carrier terahertz wave/millimeter wave generation system of the example of the present application, optionally, the integrated intensity modulator includes at least two sub-modulators, and the integrated intensity modulator is further configured to receive a DC bias voltage, to adjust the phase between the modulated signals output by the sub-modulators.

According to the light-borne terahertz wave/millimeter wave generation system of an example of the present application, optionally, the light wave generator includes: an optical frequency comb generator, which is configured to generate a plurality of coherent optical combs, wherein the plurality of The coherent optical combs are a plurality of coherent optical combs with adjacent frequency intervals f; a first fiber amplifier is used for receiving the plurality of coherent optical combs and is configured to amplify the received coherent light comb teeth; a first filter for receiving the coherent light comb teeth amplified by the first fiber amplifier and configured to filter out the preset amount of coherent light from the received coherent light comb teeth comb and send to the integrated intensity modulator.

According to the light-borne terahertz wave/millimeter-wave generation system of the example of the present application, optionally, the light-borne terahertz wave/millimeter wave generation system further includes: a second optical fiber amplifier, which is used for receiving the integrated intensity modulation the modulated signal generated by the optical fiber amplifier and amplify it; a second filter for receiving the signal amplified by the second fiber amplifier, and filtering it to generate a to-be-beat signal, wherein the to-be-beat signal The frequency interval between nf and the sum of the local oscillator frequency, n≥2 and n is an integer; a photodetector, which is used to receive the to-be-beat signal and is configured to detect the to-be-beat signal Heterodyne beating is performed to generate the terahertz/millimeter waves to be transmitted.

According to the light-borne terahertz wave/millimeter-wave generation system of an example of the present application, optionally, the light-borne terahertz wave/millimeter wave generation system further includes an antenna for emitting the generated terahertz wave/millimeter wave.

According to the optical carrier terahertz wave/millimeter wave generation system of the example of the present application, optionally, the first and second fiber amplifiers are both erbium-doped fiber amplifiers, and the first filter is configured to filter out two coherent fibers. Optical comb teeth, the integrated intensity modulator is a dual parallel Mach-Zehnder modulator.

According to the optical carrier terahertz wave/millimeter wave generation system of an example of the present application, optionally, each of the at least two sub-modulators is configured to operate at a minimum transmission point.

According to yet another aspect of the present application, there is also provided a transmitter for optical communication, the transmitter comprising: an optical wave generator configured to generate a preset number of coherent optical combs; one or more subsystems, each of which The systems are each configured to receive the predetermined number of coherent optical combs from the light wave generator. Each of the subsystems includes: an integrated intensity modulator configured to receive the preset number of coherent light combs generated by the light wave generator, and pair the received coherent light with data, local oscillator frequencies The comb teeth are modulated to generate a modulated signal; an optical fiber amplifier is used to receive and amplify the modulated signal generated by the integrated intensity modulator; a filter is used to receive the signal amplified by the optical fiber amplifier, filtering it to generate a to-be-beat signal; a photodetector for receiving the to-be-beat signal and configured to heterodyne beat the to-be-beat signal to generate a terahertz wave to be transmitted / mmWave. As an example, each of the integrated intensity modulators includes at least two sub-modulators, and each of the integrated intensity modulators is further configured to receive a DC bias voltage to adjust the difference between the modulation signals output by the sub-modulators phase.

According to the transmitter for optical communication of the present application, optionally, each subsystem further includes an antenna for transmitting the generated terahertz wave/millimeter wave. And in some examples, where the transmitter includes multiple subsystems, the antennas of the multiple subsystems are arranged based on a phased array principle.

According to the transmitter for optical communication of the present application, optionally, the light wave generator includes: an optical frequency comb generator configured to generate a plurality of coherent optical combs, wherein the plurality of coherent optical combs The teeth are a plurality of coherent optical comb teeth with an adjacent frequency interval of f; a pre-fiber amplifier is used for receiving the plurality of coherent optical comb teeth and is configured to amplify the received coherent optical comb teeth; pre-filtering a device for receiving the coherent optical combs amplified by the pre-fiber amplifier, and configured to filter out the preset number of coherent optical combs from the received coherent optical combs and send them to the Integrated intensity modulator. Optionally, the frequency interval between the to-be-beat frequency signals is the sum of nf and the local oscillator frequency, where n≧2 and n is an integer.

According to the transmitter for optical communication of the present application, for example, the fiber amplifier and the pre-fiber amplifier are both erbium-doped fiber amplifiers, and the pre-filter is configured to filter out two coherent optical combs, so The integrated intensity modulator is a dual parallel Mach-Zehnder modulator.

According to the transmitter for optical communication of the present application, optionally, each of the at least two sub-modulators is configured to operate at a minimum transmission point.

According to yet another aspect of the present application, an optical carrier/millimeter wave generation method for optical communication is also provided, which includes: generating a preset number of coherent optical comb teeth by an optical wave generator; The comb teeth are sent to the integrated intensity modulator, and each sub-modulator in the integrated intensity modulator modulates the received coherent optical comb teeth with data and local oscillator frequencies. As an example, the phase between the signals output by each of the sub-modulators is adjusted by a DC bias voltage applied to the integrated intensity modulator and the modulated signal is output by the integrated intensity modulator.

According to the optical carrier generation method for optical communication of the present application, optionally, the generating a preset number of coherent optical comb teeth by an optical wave generator includes: generating a plurality of coherent optical comb teeth by an optical frequency comb generator, wherein , the multiple coherent optical comb teeth are multiple coherent optical comb teeth with adjacent frequency interval f; the multiple coherent optical comb teeth are amplified by a fiber amplifier; the multiple coherent optical comb teeth are filtered by a filter is a preset number of coherent light combs.

According to the optical carrier generation method for optical communication of the present application, optionally, the method further includes: amplifying the modulated signal generated by the integrated intensity modulator; filtering the amplified modulated signal to generate a to-be-beat frequency signal, wherein the frequency interval between the to-be-beat frequency signals is the sum of nf and the local oscillator frequency, n≥2 and n is an integer; perform heterodyne beat frequency processing on the to-be-beat frequency signal.

According to the optical carrier generation method for optical communication of the present application, optionally, the preset number is 2.

According to the optical carrier generation method for optical communication of the present application, optionally, a dual-parallel Mach-Zehnder modulator is used as the integrated intensity modulator.

According to the optical carrier generation method for optical communication of the present application, optionally, each of the sub-modulators is configured to work at a minimum transmission point.

Description of drawings

These features, different aspects, and advantages of the present disclosure will become better understood when reading the following detailed description with reference to the accompanying drawings, wherein like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic structural diagram of a light-borne terahertz wave/millimeter wave generation system according to an embodiment of the present application;

FIG. 2 is a schematic structural diagram of a light-borne terahertz wave/millimeter wave generation system according to yet another embodiment of the present application;

Fig. 3a is a plurality of coherent optical combs with adjacent frequency interval f generated by the optical frequency comb generator 200 in Fig. 2;

Fig. 3b is the output schematic diagram of filter 204 in Fig. 2;

Fig. 3c is a modulation signal output by the dual parallel Mach-Zehnder modulator 22 in Fig. 2, including a first modulation signal 300a and a second modulation signal 302a;

Figure 3d is a diagram of a coherent signal light and a local oscillator light output after the second filter 26 is filtered in Figure 2;

4 is a light-borne terahertz wave/millimeter wave generation system according to another example of the present application;

5 is a schematic structural diagram of a transmitter for optical communication according to an example of the present application;

6 is a flow chart of a method for generating terahertz waves/millimeter waves over an optical carrier according to an example of the present application;

FIG. 7 is a flowchart of yet another example of a method for generating a terahertz wave/millimeter wave over light according to the present application.

Detailed ways

The present invention will now be described in detail with reference to the accompanying drawings and examples. The described embodiments are merely exemplary and represent subsets of embodiments of the invention. Those skilled in the art may recognize additional embodiments based on the embodiments of the present invention without inventive effort, and all such embodiments fall within the scope of the present invention.

FIG. 1 is a schematic structural diagram of a light-borne terahertz wave/millimeter wave generation system according to an embodiment of the present application. As shown in the figure, the light-borne terahertz wave/millimeter wave generation system includes a light wave generator 10 and an integrated intensity modulator 12 . The light wave generator 10 is configured to generate a preset number of coherent optical comb teeth. The integrated intensity modulator 12 is an integrated device that receives a preset number of optical comb teeth generated by the light wave generator 10 , and performs the received coherent optical comb teeth with data 13 and a local oscillator (LO) frequency (f _LO ) 15 . modulated to generate a modulated signal.

In this application, terahertz wave/millimeter wave refers to terahertz wave or millimeter wave. For example, according to the optical carrier terahertz wave/millimeter wave generation system exemplified in the present application, the optical carrier can be generated by adjusting the filter in the light wave generator (for example, the first filter or pre-filter hereinafter), etc. The hertz wave/millimeter wave generation system generates terahertz waves over light or generates millimeter waves over light.

In the example of the present application, the preset number is 2, that is, the light wave generator 10 generates two coherent light combs. The following will be described as an example, but it should be understood that the preset number may be other than 2 according to practical applications. Returning to FIG. 1 , for the two coherent optical comb teeth generated by the light wave generator 10 , the integrated intensity modulator 12 modulates the two optical comb teeth with the input data 13 and the local oscillator frequency 15 to generate a modulated signal. The resulting modulated signal carries the same data, just with a different optical carrier frequency.

The optical carrier terahertz wave/millimeter wave generation system according to the example in FIG. 1 adopts the integrated intensity modulator 12, so that the light waves are separated inside the integrated intensity modulator 12, which effectively avoids the influence of the external environment on the separated light wave signal. inconsistency.

According to some examples of the present application, a main DC bias voltage (Parent Direct Current, PDC) 17 is applied to the integrated intensity modulator 12 to phase light waves input into the integrated intensity modulator 12 by the main DC bias voltage 17 change so that the phase of the light-carrying terahertz wave/millimeter wave that will be generated later can be adjusted. In these examples, integrated intensity modulator 12 may include at least two sub-modulators. The main DC bias voltage 17 changes the refractive index of the modulator waveguide, thus adjusting the phase difference between the modulated signals output by each sub-modulator. After the photodetector performs heterodyne beat frequency on the modulated signal in the subsequent processing, the phase difference will be transmitted to the phase of the generated terahertz wave/millimeter wave. Accordingly, the optical-borne terahertz wave/millimeter-wave generation system exemplified in the present application is a phase-adjustable optical-borne terahertz wave/millimeter-wave generation system.

According to some examples of the present application, the integrated intensity modulator 12 employs a Dual-Parallel Mach-Zehnder Modulator (DPMZM).

According to some examples of the present application, the light wave generator 10 includes an optical comb generator, a fiber amplifier, and a filter. The optical comb generator generates multiple coherent optical combs with adjacent frequency interval f, the fiber amplifier amplifies the generated multiple coherent optical combs with adjacent frequency interval f, and the filter amplifies the amplified coherent optical combs. A series of coherent optical combs with adjacent frequency interval f are filtered to output two coherent optical combs with frequency interval nf, where n is an integer and n≥2. It should be noted here that more than two coherent optical combs can be output by configuring the filter, but in the examples below in this application, two coherent optical combs are generated as an example to illustrate. In addition, the frequency spacing between the generated coherent optical combs can be varied according to n. It should be noted that, among the multiple coherent optical combs generated by the optical comb generator, the number of optical combs and the value of the frequency interval f between adjacent optical combs can be generated according to the optical combs used. According to the configuration of the transmitter and the actual demand scenario, as long as the light wave generator 10 can generate the required preset number of coherent optical comb teeth, and can finally generate the terahertz wave/millimeter wave when applied to the transmitter. As an example, the optical comb generator may employ an optical frequency comb generator, or may employ a laser such as phase and frequency locking, which can generate coherent optical combs.

FIG. 2 is a schematic structural diagram of a light-borne terahertz wave/millimeter wave generation system according to yet another embodiment of the present application. As shown in the figure, the light-borne terahertz wave/millimeter wave generation system includes a light wave generator 20 and a dual parallel Mach-Zehnder modulator 22 . The light wave generator 20 includes an optical frequency comb generator (Optical Frequency Comb Generation; OFCG) 200 , a fiber amplifier 202 , and a filter 204 .

The optical frequency comb generator 200 is configured to generate a plurality of coherent optical combs with adjacent frequency spacing f. FIG. 3 a illustrates a plurality of coherent optical combs with adjacent frequency intervals f generated by the optical frequency comb generator 200 . Figure 3a illustrates n+1 optical comb teeth, where n≥2 and n is an integer, and nf is the order of terahertz wave/millimeter wave frequency. In FIG. 3a, the solid line and the dashed line are used to distinguish the plurality of optical comb teeth, and the distinction is only to illustrate the two optical comb teeth with a difference of nf frequency represented by the solid line, that is, the first optical comb tooth 300 and the nth optical comb Teeth 302 will be the two optical comb teeth that remain after subsequent filtering.

A plurality of coherent optical combs with adjacent frequency interval f generated by the optical frequency comb generator 200 will be transmitted to the fiber amplifier 202 for amplification. The fiber amplifier 202 is an Erbium-Doped Fiber Amplifier (EDFA) in this example. Fiber amplifier 202 transmits the amplified coherent optical comb to filter 204, which is filtered. The filter 204 is set in this example to retain only the first optical comb tooth 300 and the n-th optical comb tooth 302, ie, two optical comb teeth with a frequency separation of nf. FIG. 3b is a schematic diagram of the output of filter 204. FIG. In this example, the electric field E ₁ of the two coherent optical comb teeth in FIG. 3b , that is, the first optical comb tooth 300 and the n-th optical comb tooth 302 can be expressed as formula (1):

E ₁ ∝ exp(j2πf _c t)+exp[j2π(f _c +nf)t] (1)

Among them, f _c is the frequency of the first optical comb, j is a complex number, and t is time.

The dual-parallel Mach-Zehnder modulator 22 receives the first and nth optical comb teeth output from the filter 204 to be modulated by the data 23 and the local oscillator frequency 25 input to the dual-parallel Mach-Zehnder modulator 22 , thereby generating a modulated signal. The dual parallel Mach-Zehnder modulator 22 includes a first sub-modulator 220 and a second sub-modulator 222, both of which may be set to operate at a minimum transmission point, by way of example. The term operating at the minimum transmission point is consistent with the understanding of those skilled in the art, that is, the modulator operates at a phase difference of 180°+m*360° between the upper and lower arms of the modulator brought about by the DC bias voltage applied to it. case, where m is an integer. According to the present application, a main DC bias voltage 27 is applied to the dual parallel Mach-Zehnder modulator 22 . The main DC bias voltage 27 can change the refractive index of the modulator optical waveguide, so that the modulation signals output by the first sub-modulator 220 and the second sub-modulator 222 generate a phase difference. FIG. 3c is a modulation signal output by the dual parallel Mach-Zehnder modulator 22, including a first modulation signal 300a and a second modulation signal 302a. In the figure, the first local oscillator light 3001 and the second local oscillator light 3002 are located on both sides of the first modulation signal 300a, respectively, and the third local oscillator light 3003 and the fourth local oscillator light located on both sides of the second modulation signal 302a are respectively. Light 3004.

In the example of FIG. 2 , the two coherent optical combs filtered by the filter 204 , namely the first optical comb 300 and the n-th optical comb 302 , are data summed in the dual-parallel Mach-Zehnder modulator 22 . Local oscillator frequency modulation. Because the dual-parallel Mach-Zehnder modulator 22 is an integrated device, the optical signal does not introduce phase noise therein due to the separation of physical optical paths. And, as mentioned above, the two sub-modulators of the dual parallel Mach-Zehnder modulators 22 are all biased at the minimum transmission point to realize carrier suppressed-Double Sidebands (Carrier suppressed-Double Sidebands; CS-DSB), Thus, the optical carrier is suppressed, and signal light and local oscillator light are generated. Under small-signal modulation, the output electric field E ₂ of the dual-parallel Mach-Zehnder modulator 22 can be expressed as Equation (2):

是双平行马赫-曾德尔调制器22的主直流偏置电压27带来的光信号的相位差。在小信号调制下，双平行马赫-曾德尔调制器22的输出示意在图3c中。 where s(t) is the input data signal, f _LO is the local oscillator frequency, m ₁ and m ₂ are the modulation factors of the first sub-modulator 220 and the second sub-modulator 222, respectively,

is the phase difference of the optical signal brought about by the main DC bias voltage 27 of the dual parallel Mach-Zehnder modulators 22 . Under small signal modulation, the output of the dual parallel Mach-Zehnder modulator 22 is illustrated in Figure 3c.

The optical carrier terahertz wave/millimeter wave generation system described herein in conjunction with FIG. 2 can optionally further include a fiber amplifier for receiving the two modulated signals output by the dual parallel Mach-Zehnder modulators 22 and a fiber amplifier connected to the amplifier. connected filter. In order to distinguish them from the fiber amplifier 202 and the filter 204 in the lightwave generator described above, the amplifier and filter arranged at the output end of the double parallel Mach-Zehnder modulator 22 are respectively referred to as the second fiber amplifier and the second filter. , correspondingly, the fiber amplifier 202 in FIG. 2 above is referred to as the first fiber amplifier, and the filter 204 is referred to as the first filter. The second fiber amplifier is used to amplify the two modulated signals output by the dual parallel Mach-Zehnder modulators 22, and the second filter includes filtering the output of the second fiber amplifier.

Returning to FIG. 2 , optionally, the light-borne terahertz wave/millimeter wave generation system further includes a second fiber amplifier 24 , a second filter 26 and a photodetector. In each example of the present application, by way of example but not limitation, the photodetector adopts a single-row carrier photodetector (Uni-Traveling-Carrier Photodiode; UTC-PD) 28 . The second fiber amplifier 24 amplifies the incoming signal and is filtered by the second filter 26 . The second filter 26 outputs a signal light and a local oscillator light after filtering, and the frequency interval between the two is the sum of nf and the local oscillator frequency f _LO . In this example, the outputs of the second filter 26 are illustrated in FIG. 3d , which are the first modulated signal 300 a and the fourth local oscillator 3004 . It should be noted that the second filter 26 is configurable, and can output different combinations of signal light (ie, modulated signal) and local oscillator light, such as the first signal light and the third local oscillator light, and the second signal light. light and the first local oscillator light, etc. The electric field E3 of the coherent signal light and the local oscillator light shown in Fig. _3d can be expressed as formula (3):

Wherein, each parameter has been described above in conjunction with formulas (1) and (2), and will not be repeated here.

The two coherent light waves output by the second filter 26 , that is, the optical comb teeth of the second signal light and the first local oscillator light, have been CS-DSB modulated in the first sub-modulator 220 and the second sub-modulator 222 . . Due to the two coherent optical combs screened by the filter 204, the carrier suppression double sideband modulation CS-DSB is implemented in both the first sub-modulator 220 and the second sub-modulator 222, which suppresses the optical carrier and reduces the entry of single-line carrier The useless optical power of the electron photodetector 28 improves the receiving sensitivity of the light-borne terahertz wave/millimeter wave generation system. The data signal and the pilot signal are respectively used to drive the first sub-modulator 220 and the second sub-modulator 222, so that the isolation of the data signal and the pilot signal is effectively guaranteed, and the mutual interference in the signal modulation process is reduced. In addition, since the data signal is a baseband signal, according to the example of the present application, the requirement for the bandwidth of the dual parallel Mach-Zehnder modulator is also reduced.

The filtered output signal of the second filter 26 is transmitted to the single-row carrier photodetector 28 for heterodyne beat frequency. In this example, ignoring the DC term generated by the single-row carrier photodetector 28, the terahertz photocurrent i(t) generated by the single-row carrier photodetector 28 can be expressed as:

是E ₃的共轭，其余参数已在上文介绍。 in,

is the conjugate _of E3, and the remaining parameters have been introduced above.

According to some examples of this application, antennas may also be added. For example, the system shown in FIG. 2 adds an antenna 30 to transmit the beat-frequency processed signal of the single-row carrier photodetector 28 . As an example, the antenna is, for example, the Horn Antenna (Horn Antenna; HA) shown in FIG. 2 .

According to some examples of the present application, the over-optical terahertz wave/millimeter wave generation system shown in FIGS. 1 and 2 may include more than one integrated intensity modulator. That is, two coherent optical combs generated by one lightwave generator, such as lightwave generator 10 of FIG. 1 or lightwave generator 20 of FIG. 2, can be fed to multiple integrated intensity modulators in parallel, by their respective to be processed. Optionally, a second fiber amplifier, a second filter, a single row of carrier photodetectors, and an antenna can be placed behind each integrated intensity modulator. In this case, an optical comb equivalent to the output of one lightwave generator is transmitted to a plurality of combs consisting of an integrated intensity modulator, a second fiber amplifier, a second filter, a single-row carrier photodetector and an antenna connected in sequence. in the communication channel.

According to the present application, a light-borne terahertz wave/millimeter wave generation system may include a light wave generator and a plurality of integrated intensity modulators connected in parallel to the light wave generator. The one light wave generator generates a preset number of coherent optical comb teeth with adjacent frequency intervals of f, and each integrated intensity modulator receives the preset number of coherent optical comb teeth to generate a modulation signal. For example, the plurality of integrated intensity modulators 12 shown in FIG. 1 are connected to the light wave generator 10 in parallel, and each of the plurality of integrated intensity modulators 12 receives two coherent optical numbers output by the light wave generator 10, A modulated signal is generated after modulation.

FIG. 4 is a light-borne terahertz wave/millimeter wave generation system according to another example of the present application. Compared with the example shown in FIG. 2 , the difference is that, in the example of FIG. 4 , one light wave generator 20 in the light-borne terahertz wave/millimeter wave generation system corresponds to a plurality of sub-channels CH1 ˜ CHK. In FIG. 4 , each sub-channel includes dual parallel Mach-Zehnder modulators 22 . A plurality of dual parallel Mach-Zehnder modulators 22 are connected in parallel to the same light wave generator 20 . Thereby, a preset number of coherent optical combs generated by the light wave generator 20 are sent to the dual parallel Mach-Zehnder modulators 22 of each channel. Here, the preset number is, for example, 2, and the light wave generator 20 generates 2 coherent light comb teeth.

According to the example of FIG. 4 , in some cases, each sub-channel further includes a second fiber amplifier 24 and a second filter 26 . Each dual parallel Mach-Zehnder modulator 22 modulates the two coherent optical combs with externally input data and local oscillator frequency, and the generated modulated signal is input to the second fiber amplifier 24 connected thereto.

The second fiber amplifier 24 sends the amplified signal to the second filter 26 to generate the to-be-beat signal through filtering. In still other cases, each subchannel may also include a single row of carrier photodetectors 28 in accordance with the example of FIG. 4 . The to-be-beat signal is sent to the single-row carrier photodetector 28 , which performs heterodyne beating to generate terahertz/millimeter waves, and sends it to the antenna 30 for emission.

It should be noted that, due to the relationship of the drawings, among the plurality of sub-channels CH1 to CHK, only the components of the outermost sub-channel CHK facing the reader are shown in FIG. 4 . In addition, in the example given in FIG. 4 , the components are not limited to those shown, for example, the optical wave generator can replace the optical frequency comb generator with a phase- and frequency-locked laser; the other components can also adopt other alternatives. , as long as the function to be achieved can be achieved.

According to some examples of the present application, a transmitter for optical communication is also provided. FIG. 5 is a schematic structural diagram of a transmitter for optical communication according to an example of the present application. As shown, the transmitter includes a lightwave generator 50, a subsystem or subsystems, wherein the subsystems are indicated by subsystem 1, subsystem 2 through subsystem K, where K is an integer and greater than or equal to 2. A subsystem is equivalent to a signal transmission channel. The subsystems are connected to the lightwave generator 50 in a parallel connection. The signal generated by the light wave generator 50 is transmitted to each subsystem.

一致的方式来设置要施加到各集成式强度调制器52的主直流偏置电压。光纤放大器54接收集成式强度调制器52生成的调制信号并对其进行放大。放大后的调制信号被输送到滤波器56中以对其进行滤波从而生成待拍频信号。光电探测器58(例如为单行载流子光电探测器)对该待拍频信号进行外差拍频处理，随后由天线60将拍频后的信号发射出去。 According to examples of the present application, each subsystem includes an integrated intensity modulator 52 , a fiber amplifier 54 , a filter 56 , a photodetector 58 and an antenna 60 . The integrated intensity modulator 52 is configured to receive a preset number of coherent optical comb teeth generated by the light wave generator 50, and modulate the received coherent optical comb teeth with the data 53 and the local oscillator frequency 55, thereby generating a modulation signal. The main DC bias voltages applied to the integrated intensity modulators 52 of each subsystem are different for beamforming. Illustratively, the optical phase difference can be generated by making the main DC bias voltage of the integrated intensity modulator 52 of the adjacent subsystem

The main DC bias voltage to be applied to each integrated intensity modulator 52 is set in a consistent manner. Fiber amplifier 54 receives and amplifies the modulated signal generated by integrated intensity modulator 52 . The amplified modulated signal is fed to filter 56 to filter it to generate a to-be-beat signal. The photodetector 58 (for example, a single-row carrier photodetector) performs heterodyne beat frequency processing on the to-be-beated signal, and then the antenna 60 transmits the beat-frequency signal.

For example, the preset number is 2, that is, the light wave generator 50 generates 2 coherent optical comb teeth, and the interval frequency of the two coherent optical comb teeth is greater than 100 GHz, for example.

The light wave generator 50 includes an optical frequency comb generator 500 , a pre-fiber amplifier 502 , and a pre-filter 504 . The optical frequency comb generator 500 is configured to generate a plurality of coherent optical comb teeth, wherein the plurality of coherent optical comb teeth are a plurality of coherent optical comb teeth with an adjacent frequency interval of f. The front fiber amplifier 502 is used to receive the plurality of coherent optical combs and is configured to amplify the received coherent optical combs. The pre-filter 504 receives the coherent optical combs amplified by the pre-fiber amplifier 502 and is configured to filter out a preset number of coherent optical combs from the received coherent optical combs and send them to the integrated intensity modulator 52 . It should be noted that the "front" in the pre-fiber amplifier 502 and the pre-filter 504 is to distinguish them from the fiber amplifier 54 and the filter 56 provided at the output end of the integrated intensity modulator 52, and there is no other limitation.

As an example, the integrated intensity modulator 52 includes two sub-modulators. The integrated intensity modulator 52 is also configured to receive the main DC bias voltage, and to generate a phase difference between the modulated optical signals output by the respective sub-modulators by the main DC bias voltage. Fiber amplifier 54 amplifies the output of integrated intensity modulator 52 and delivers the amplified signal to filter 56 , which filters out the desired signal, which is delivered to photodetector 58 . The photodetector 58 performs heterodyne beat processing on the signal input therein to generate terahertz/electromagnetic waves to be emitted. At this time, the phase difference between the modulated optical signals output by each sub-modulator previously generated by the main DC bias voltage is transferred to the terahertz wave/electromagnetic wave generated after the beat frequency. Thus, the transmitter shown in FIG. 5 is a transmitter with a controllable optical carrier phase. It is possible that the integrated intensity modulator 52 includes more sub-modulators. Also, in this example, the sub-modulator can be set to operate at the minimum transmission point.

Illustratively, the optical frequency comb generator 500 in FIG. 5 may be replaced by a phase and frequency locked laser. Illustratively, the integrated intensity modulator 52 may employ dual parallel Mach-Zehnder modulators.

According to some examples of the present application, a transmitter for optical communication may be a transmitter employing the optical-borne terahertz wave/millimeter wave generation system described above in connection with the various examples.

FIG. 6 is a flowchart of a method for generating terahertz waves/millimeter waves over an optical carrier according to an example of the present application. The method will be described below in conjunction with FIG. 2 . It should be noted that this method can also be applied to other systems or devices, such as the optical carrier terahertz wave/millimeter wave generation system shown in FIG. 1 and FIG. 4 and the transmitter shown in FIG. 5 .

Referring to FIG. 6 and FIG. 2 , in step S600 , a preset number of coherent optical comb teeth are generated by the light wave generator 20 . In step S602, the generated preset number of coherent optical combs is sent to the dual-parallel Mach-Zehnder modulator 22, which modulates the received coherent optical combs with data 23 and local oscillator frequency 25 to A modulated signal is generated.

FIG. 7 is a flow chart of yet another example of a method for generating terahertz waves/millimeter waves over light according to the present application. 2 and 7 are also referred to.

In step S700, a plurality of coherent optical comb teeth are generated by the optical frequency comb generator 200, wherein the plurality of coherent optical comb teeth are a plurality of coherent optical comb teeth whose adjacent frequency interval is f.

In step S702 , the plurality of coherent optical comb teeth are amplified by the fiber amplifier 202 .

In step S704 , the plurality of coherent optical comb teeth are filtered into a preset number of coherent optical comb teeth by the filter 204 . Illustratively, the preset number is 2.

In step S706, the received coherent optical comb teeth are modulated with data 23, local oscillator frequency 25 by each sub-modulator in the dual-parallel Mach-Zehnder modulator 22; The main DC bias voltage 27 of the modulator 22 is to generate a phase difference between the modulated optical signals of the sub-modulators in the dual parallel Mach-Zehnder modulator 22; wherein the sub-modulators are, for example, configured to operate at a minimum transfer point.

In step S708 , the modulated signal generated by the dual parallel Mach-Zehnder modulator 22 is amplified by the second fiber amplifier 24 .

In step S710, the amplified modulated signal is filtered by the second filter 26 to generate a to-be-beat signal.

In step S712 , the single-row carrier photodetector 28 performs heterodyne beat processing on the to-be-beat signal to generate the terahertz wave/millimeter wave to be emitted, here, in the dual-parallel Mach-Zehnder modulator 22 The generated phase difference between the modulated optical signals of the sub-modulators is transferred to the phase of the generated terahertz wave/millimeter wave.

The terahertz wave/millimeter wave generated in step S712 to be transmitted can be transmitted by the antenna 30, as shown in step S714.

The method of generating terahertz wave/millimeter wave on optical carrier shown in Fig. 6 or Fig. 7 is adopted, because the coherent optical comb is sent to the integrated modulator for modulation, which avoids the influence of the external environment on the separated light wave signal to the greatest extent. inconsistency. And, in some instances, a phase difference is also created between the modulated optical signals of the sub-modulators by the DC bias voltage (also referred to as the main DC bias voltage, depending on the context) applied to the integrated modulator, and ultimately the This phase difference is transferred to the phase of the generated terahertz wave/millimeter wave, thereby realizing the generation process of the phase-adjustable terahertz wave/millimeter wave.

In the example given in this application, f is, for example, 20 GHz, and n is, for example, 10, then the optical frequency comb generator generates 10 coherent optical comb teeth, and the frequency interval f of adjacent optical comb teeth is 20 GHz. The local oscillator frequency f _LO is, for example, 30 GHz, and the frequency interval between the to-be-beat signals is the sum of nf and the local oscillator frequency f _LO , that is, 230 GHz.

被传递到最终产生的太赫兹波/毫米波的相位上。据此，按照本申请各示例，通过调节施加到双平行马赫-曾德尔调制器的主直流偏置电压，即可实现对所产生的太赫兹波/毫米波相位的控制。 In the above examples, the phase difference generated between the modulated optical signals at the outputs of the sub-modulators of an integrated intensity modulator (eg, dual parallel Mach-Zehnder modulators) via the main DC bias voltage

is transferred to the phase of the resulting terahertz/millimeter wave. Accordingly, according to various examples of the present application, by adjusting the main DC bias voltage applied to the dual-parallel Mach-Zehnder modulator, the phase control of the generated terahertz wave/millimeter wave can be achieved.

Since the phase noise caused by the separation of physical optical paths is not introduced during the entire modulation and optical filtering process, the generated terahertz/millimeter waves have high phase stability. In the generation process of terahertz waves/millimeter waves, the use of electronic devices is not involved, so the generated terahertz waves/millimeter waves are theoretically not limited by the bottleneck of electronic devices.

Accordingly, according to the examples of the present application, the generation of single-channel, low-phase-noise, phase-adjustable optical-carrier terahertz waves/millimeter waves can be realized without using a DSP algorithm at the receiving end.

相等，如公式(5)： In addition, in multi-channel or multi-subsystem embodiments such as those described in conjunction with Figures 4 and 5, each channel is adjusted for multiple low-phase-noise, phase-tunable optical carrier THz/millimeter-wave channels The main DC bias voltage of the dual parallel Mach-Zehnder modulators makes the phase difference of the THz/millimeter waves generated by the adjacent two channels

are equal, as in formula (5):

为集成式强度调制器的子调制器所输出的调制光信号之间的相位差；

下标中的K、K+1和K-1是用来指示

所归属的通道；其中，K表示通道数，K≥2且K为整数，K为本通道的话，K+1和K-1则为本通道相邻两个通道。 in,

is the phase difference between the modulated optical signals output by the sub-modulators of the integrated intensity modulator;

K, K+1 and K-1 in the subscript are used to indicate

The channel to which it belongs; where K represents the number of channels, K≥2 and K is an integer, if K is the channel, K+1 and K-1 are the adjacent two channels of the channel.

According to some examples of the present application, the antennas of each subsystem or each channel can be arranged according to the principle of phased array, so that beamforming of terahertz waves/millimeter waves can be realized, and the wireless transmission distance of terahertz waves can be improved. By cooperatively controlling the main DC bias voltages applied to each of the dual parallel Mach-Zehnder modulators, the scanning of space by a THz/mmWave beam can be achieved.

To sum up, according to the solution of the examples in this application, the integrated intensity modulator can be used to avoid the phase noise problem caused by the inconsistent influence of the external environment on the separated light wave signal, and at the same time, the main DC bias voltage can also be applied to the An integrated intensity modulator to achieve phase tuning of the resulting THz/mmWave signal.

Various examples of the present application have been described with reference to the accompanying drawings, but the above examples and implementations are only illustrative and not limiting. For those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, which should be covered by the protection scope of the claims of the present application.

Claims (22)

An optical-borne terahertz wave/millimeter wave generation system, characterized in that the system comprises: an optical wave generator configured to generate a preset number of coherent optical combs; An integrated intensity modulator configured to receive the preset number of coherent optical comb teeth generated by the light wave generator, and modulate the received coherent optical comb teeth with data and local oscillator frequencies to generate modulation Signal. The optical carrier terahertz wave/millimeter wave generation system of claim 1, wherein the integrated intensity modulator comprises at least two sub-modulators, and the integrated intensity modulator is further configured to receive direct current a bias voltage to adjust the phase between the modulation signals output by the at least two sub-modulators. The optical carrier terahertz wave/millimeter wave generation system according to claim 1 or 2, wherein the light wave generator comprises: an optical frequency comb generator configured to generate a plurality of coherent optical comb teeth, wherein the plurality of coherent optical comb teeth are a plurality of coherent optical comb teeth with an adjacent frequency interval of f; a first fiber amplifier for receiving the plurality of coherent optical combs and configured to amplify the received plurality of coherent optical combs; and a first filter for receiving the plurality of coherent optical combs amplified by the first fiber amplifier and configured to filter out the preset number from the received plurality of coherent optical combs The coherent optical combs are sent to the integrated intensity modulator. The optical-borne terahertz wave/millimeter-wave generation system according to claim 3, wherein the optical-borne terahertz wave/millimeter-wave generation system further comprises: a second fiber amplifier for receiving and amplifying the modulated signal generated by the integrated intensity modulator; The second filter is used for receiving the signal amplified by the second fiber amplifier, and filtering it to generate a signal to be beat frequency, wherein the frequency interval between the frequency signal to be beat is nf and the frequency the sum of the vibration frequencies, n ≥ 2 and n is an integer; and A photodetector for receiving the to-be-beat signal and configured to heterodyne beat on the to-be-beat signal to generate a terahertz wave/millimeter wave to be transmitted. The optical carrier terahertz wave/millimeter wave generating system according to claim 4, wherein the optical carrier terahertz wave/millimeter wave generating system further comprises a terahertz wave/millimeter wave for emitting the to-be-transmitted terahertz wave/millimeter wave 's antenna. The optical carrier terahertz wave/millimeter wave generation system according to claim 4, wherein the first fiber amplifier and the second fiber amplifier are both erbium-doped fiber amplifiers, and the first filter is configured To filter out two coherent light combs, the integrated intensity modulator is a dual parallel Mach-Zehnder modulator. The optical carrier terahertz wave/millimeter wave generation system according to any one of claims 2 to 6, wherein each of the at least two sub-modulators is configured to operate at a minimum transmission point. A transmitter for optical communication, characterized in that the transmitter comprises: an optical wave generator configured to generate a preset number of coherent optical combs; and one or more subsystems, each of the subsystems configured to receive the preset number of coherent optical combs from the lightwave generator, each of the subsystems comprising: An integrated intensity modulator configured to receive the preset number of coherent optical comb teeth generated by the light wave generator, and modulate the received coherent optical comb teeth with data and local oscillator frequencies to generate modulation Signal; a fiber amplifier for receiving and amplifying the modulated signal generated by the integrated intensity modulator; a filter for receiving the signal amplified via the fiber amplifier, filtering it to generate a signal to be beat; and A photodetector for receiving the to-be-beat signal and configured to perform heterodyne beat on the to-be-beat signal to generate a terahertz wave/millimeter wave to be transmitted. The transmitter for optical communication of claim 8, wherein each integrated intensity modulator includes at least two sub-modulators, and wherein each integrated intensity modulator is further configured to receive a DC bias A voltage is set to adjust the phase between the modulation signals output by the at least two sub-modulators. The transmitter for optical communication according to claim 8, wherein each of the subsystems further comprises: an antenna for transmitting the terahertz wave/millimeter wave to be transmitted. The transmitter for optical communication according to claim 9, wherein when the transmitter includes the multiple subsystems, the antennas of the multiple subsystems are arranged based on a phased array principle. The transmitter for optical communication according to claim 8, wherein the light wave generator comprises: an optical frequency comb generator configured to generate a plurality of coherent optical comb teeth, wherein the plurality of coherent optical comb teeth are a plurality of coherent optical comb teeth with an adjacent frequency interval of f; a pre-fiber amplifier for receiving the plurality of coherent optical combs and configured to amplify the received plurality of coherent optical combs; and A pre-filter for receiving the plurality of coherent optical combs amplified by the pre-fiber amplifier, and configured to filter out the preset number of coherent optical combs from the received coherent optical combs and sent to the integrated intensity modulator. The transmitter for optical communication according to claim 12, wherein the frequency interval between the to-be-beat signals is the sum of nf and the local oscillator frequency, where n≥2 and n is an integer. The transmitter for optical communication according to claim 12, wherein the fiber amplifier and the pre-fiber amplifier are both erbium-doped fiber amplifiers, and the pre-filter is configured to filter out two coherent light beams Comb teeth, the integrated intensity modulator is a dual parallel Mach-Zehnder modulator. 15. The transmitter for optical communication according to any one of claims 8 to 14, wherein each of the at least two sub-modulators is configured to operate at a minimum transmission point. A method for generating light-borne terahertz waves/millimeter waves, characterized in that the method comprises: generating a preset number of coherent optical combs by a lightwave generator; and Sending the generated preset number of coherent optical combs to the integrated intensity modulator, and each sub-modulator in the integrated intensity modulator modulates the received coherent optical combs with data and local oscillator frequency . The optical carrier terahertz wave/millimeter wave generation method according to claim 16, wherein the method further comprises: The phase between the modulated signals output by each of the sub-modulators is adjusted by a DC bias voltage applied to the integrated intensity modulator, and the modulated signals are output by the integrated intensity modulator. The method for generating a terahertz wave/millimeter wave on an optical carrier according to claim 16, wherein the generating a preset number of coherent optical comb teeth by the light wave generator comprises: generating a plurality of coherent optical comb teeth by an optical frequency comb generator, wherein the plurality of coherent optical comb teeth are a plurality of coherent optical comb teeth whose adjacent frequency interval is f; amplifying the plurality of coherent optical combs by a fiber amplifier; and The plurality of coherent optical comb teeth are filtered into the preset number of coherent optical comb teeth by a filter. The optical carrier terahertz wave/millimeter wave generation method according to claim 16, wherein the method further comprises: amplifying the modulated signal generated by the integrated intensity modulator; Filtering the amplified modulated signal to generate a to-be-beat signal, wherein the frequency interval between the to-be-beat signals is the sum of nf and the local oscillator frequency, n≥2 and n is an integer; and Perform heterodyne beat processing on the to-be-beat signal. The method for generating terahertz waves/millimeter waves over an optical carrier according to any one of claims 16 to 19, wherein the preset number is two. The method for generating terahertz waves/millimeter waves over an optical carrier according to any one of claims 16 to 19, wherein a dual-parallel Mach-Zehnder modulator is used as the integrated intensity modulator. The method for generating terahertz waves/millimeter waves over an optical carrier according to any one of claims 16 to 19, wherein each of the sub-modulators is configured to operate at a minimum transmission point.

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