Method and system for wavelength tuning of a tunable semiconductor laser based on optoelectronic feedback

Abstract

The present application relates to optical fiber sensing, optical communication technical field, disclose a kind of wavelength tuning system of tunable semiconductor laser based on photoelectric feedback, including user control module, modulated grating Y laser, user application light path, beam splitter, optical isolator, photoelectric conversion circuit, negative feedback amplification circuit, adjustable current source circuit;The output light of modulated grating Y laser passes through beam splitter, and part of light enters optical isolator, and then enters user application light path, another part of light enters photoelectric conversion circuit, input negative feedback amplification circuit, and then control adjustable current source circuit, to control SOA current output to modulated grating Y laser, to change output light power.The present application is in the calibration and normal working process of modulated grating Y laser, and the light power of laser output is collected in real time by beam splitter, forms negative feedback at SOA current, only needs to input left current, right current, phase current, and automatically matches appropriate SOA current to carry out power compensation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber sensing and optical communication technology, and particularly relates to a wavelength tuning method and system of a tunable semiconductor laser based on photoelectric feedback. BACKGROUND

[0002] The tunable semiconductor laser is one of the most commonly used light sources in digital coherent optical communication systems and optical fiber sensing systems. The wavelength can be continuously tunable in the ITU channel or C band, with high precision, high power and low cost, which are the main requirements for tunable lasers. The modulation grating Y laser meets all the above requirements and is widely used in the fields of optical fiber sensing and optical communication.

[0003] Currently, the wavelength calibration method for the modulation grating Y laser is to scan the left current, the right current and the phase current, select the left, right and phase current values corresponding to the required wavelength, and then adjust the SOA current to compensate the output optical power, so that the optical power stability of all wavelengths meets the requirements. However, the modulation method and structure of the modulation grating Y laser cause the change of the SOA current to have a weak influence on the output wavelength of the laser, resulting in a change in the wavelength. At this time, the phase current needs to be fine-tuned to make the wavelength meet the requirements, and the fine-tuning of the phase current will cause the output optical power of the laser to change. The SOA current needs to be adjusted again to calibrate the optical power. At this time, although the adjustment range of the SOA current is smaller than the first adjustment and has less influence on the wavelength, the phase current still needs to be adjusted again to calibrate the output wavelength. Similarly, the range of the second fine-tuning of the phase current is also smaller than the first adjustment, but it will also affect the output optical power. Therefore, after the first rough calibration of the modulation method of the modulation grating Y laser, the phase current and the SOA current need to be repeatedly adjusted for each output wavelength to calibrate in a cycle, so that the wavelength accuracy and the output power meet the requirements.

[0004] The above is the existing counting level, which mainly has the following shortcomings:

[0005] 1. Since the phase current and the SOA current of the modulation grating Y laser will affect the output wavelength and the output optical power, the existing method of adjusting one current alone and calibrating in a cycle cannot make the output wavelength and the output optical power completely meet the target requirements, but only can approach them gradually.

[0006] 2. In the field of optical communication, the ITU-T G.692 standard defines the center wavelength of the 40-wave or 80-wave system in the C band. In the field of optical fiber sensing, especially in the optical fiber grating demodulation system, the modulation grating Y laser needs to output more than 4000 wavelengths. Therefore, the existing method of calibrating the phase current and the SOA current in a cycle causes a great amount of work and a long time for the calibration of the modulation grating Y laser. SUMMARY

[0007] The application provides a wavelength tuning method and system of a tunable semiconductor laser based on photoelectric feedback.

[0008] The application provides a wavelength tuning system of a tunable semiconductor laser based on photoelectric feedback, which comprises a user control module, a modulated grating Y laser, a photoelectric feedback device and a user application light path.

[0009] The photoelectric feedback device comprises a beam splitter, an optical isolator, an optical-electric conversion circuit, a negative feedback amplification circuit and an adjustable current source circuit.

[0010] The user control module inputs left current, right current, phase current and gain current to the modulated grating Y laser.

[0011] Further, the optical-electric conversion circuit, the negative feedback amplification circuit and the adjustable current source circuit specifically comprise:

[0012] a constant current source I3, a capacitor C1, a first resistor R1, a second resistor R3, a third resistor R4, a fourth resistor R5, a fifth resistor R6, a sixth resistor R10, a first operational amplifier X8, a second operational amplifier X9, a third operational amplifier X10, a 2N3904 transistor Q1 and a light emitting diode D1.

[0013] One end of the constant current source I3 is grounded, the other end is connected to one end of the capacitor C1, one end of the first resistor R1, and the inverting input terminal of the first operational amplifier X8. The other end of the capacitor C1 and the other end of the first resistor R1 converge and are connected to the output terminal of the first operational amplifier X8 and the non-inverting input terminal of the second operational amplifier X9. The non-inverting input terminal of the first operational amplifier X8 is grounded. The inverting input terminal and the output terminal of the second operational amplifier X9 are both connected to one end of the second resistor R3. The other end of the second resistor R3 is connected to one end of the fifth resistor R6 and the inverting input terminal of the third operational amplifier X10. The non-inverting input terminal of the third operational amplifier X10 is connected to one end of the third resistor R4 and one end of the fourth resistor R5. The other end of the third resistor R4 is connected to a power supply, and the other end of the fourth resistor R5 is grounded. The other end of the fifth resistor R6 and the output terminal of the third operational amplifier X10 are both connected to the base of the 2N3904 transistor Q1. The collector of the 2N3904 transistor Q1 is connected to a power supply. The emitter of the 2N3904 transistor Q1 is connected to one end of the sixth resistor R10. The other end of the sixth resistor R10 is connected to the anode of the light-emitting diode D1. The cathode of the light-emitting diode D1 is grounded.

[0014] Further, the optical splitter is a 1x2 optical splitter, and the splitting ratio is 1:99. The 99% of the output light enters the optical isolator, and the 1% of the output light enters the photoelectric conversion circuit.

[0015] Further, in the photoelectric feedback device,

[0016] The optical isolator is used to prevent the user application from interfering with the photoelectric feedback system.

[0017] The negative feedback amplification circuit is used to reverse and amplify the feedback electrical signal. The reverse effect is that when the output optical power of the modulated grating Y laser decreases, the 1% feedback light decreases, and the corresponding feedback electrical signal decreases. At this time, it is necessary to increase the SOA current, and then the adjustable current source circuit needs to increase the output. The amplification effect is that the fluctuation range of the feedback light signal is matched with the input range of the adjustable current source circuit.

[0018] Further, the modulated grating Y laser includes a left sampling grating, a right sampling grating, a multimode interference coupler, a phase adjustment module, a gain control module, and a SOA semiconductor optical amplifier. The left sampling grating and the right sampling grating are connected to the multimode interference coupler. The multimode interference coupler is connected to the phase adjustment. The phase adjustment module, the gain control module, and the SOA semiconductor optical amplifier are connected in sequence.

[0019] The left sampling grating, the right sampling grating, the phase adjustment module, the gain control module and the SOA semiconductor optical amplifier are all driven by constant current; the left sampling grating and the right sampling grating are used as reflectors, are two comb gratings with multiple reflection peaks, the vernier effect is formed by using the two comb gratings, the reflection peak of a specific wavelength is returned after the multimode interference coupler is superimposed, then the gain control module is inputted for longitudinal mode screening, the phase adjustment module is used for realizing longitudinal mode moving, the spectral range of tuning under each longitudinal mode is widened, and the SOA semiconductor amplifier is used for optical power compensation, so that the output optical power in the tuning range is ensured to be in a set range.

[0020] The application further provides a wavelength tuning method of a tunable semiconductor laser based on photoelectric feedback, which is based on the wavelength tuning system of the tunable semiconductor laser.

[0021] S1, the user control module inputs left current, right current, phase current and gain current to the modulation grating Y laser;

[0022] S2, in the modulation grating Y laser, the left sampling grating and the right sampling grating are used as comb gratings, the vernier effect is formed by using the two comb gratings, the reflection peak of a specific wavelength is returned after the multimode interference coupler is superimposed, then the gain control module is inputted for longitudinal mode screening, the phase adjustment module is used for realizing longitudinal mode moving, the spectral range of tuning under each longitudinal mode is widened, and the SOA semiconductor amplifier is used for optical power compensation, so that the output optical power in the tuning range is ensured to be in a set range;

[0023] S3, the output light of the modulation grating Y laser passes through a light splitter, the splitting ratio of the light splitter is 1:99, the part of 99% of the light output enters the optical isolator, and then enters the user application light path;

[0024] The part of 1% of the light output enters the photoelectric conversion circuit to convert the feedback optical signal into a feedback electrical signal, and the feedback electrical signal is inputted into the negative feedback amplification circuit;

[0025] S4, the negative feedback amplification circuit reverses and amplifies the feedback electrical signal;

[0026] Reversing: when the output optical power of the modulation grating Y laser decreases, the 1% feedback light decreases, the corresponding feedback electrical signal decreases, at this time, the SOA current is increased, and the output of the adjustable current source circuit is increased;

[0027] Amplification: the fluctuation range of the feedback optical signal is greatly matched with the input range of the adjustable current source circuit;

[0028] S5, the feedback electrical signal output by the negative feedback amplification circuit controls the adjustable current source circuit, so as to control the SOA current output to the modulation grating Y laser, thereby changing the output optical power.

[0029] The beneficial effects of the present application are:

[0030] In the modulation grating Y laser in the present application, after the user control module inputs left current, right current, phase current and GAIN current each time during calibration and normal working process, the photoelectric feedback system will automatically generate corresponding SOA current. In the calibration process, the photoelectric feedback device is introduced, which is equivalent to inputting a phase current, and the phase current and SOA current are adjusted and controlled simultaneously, so that the phase current and SOA current can realize accurate calibration together, thereby realizing accurate calibration of output wavelength and optical power, without the need for cyclic and successive approximation calibration of phase current and SOA current, improving the calibration accuracy and reducing the calibration time. At the same time, in the negative feedback amplification circuit, an adjustable potentiometer is designed to adjust the negative feedback amplification multiple, so as to adjust the output optical power during calibration; in the actual application process, the left current, the right current, the phase current and the gain current are output according to the calibrated current, and the output optical power is modulated by the photoelectric feedback device, so as to automatically match the SOA current during calibration, so as to achieve the output wavelength and optical power during calibration. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a structure schematic diagram of the tunable semiconductor laser wavelength tuning system based on photoelectric feedback in the present application.

[0032] Figure 2 It is a structure schematic diagram of the modulation grating Y laser in the present application.

[0033] Figure 3 It is an application circuit diagram of the photoelectric conversion circuit, the negative feedback amplification circuit and the adjustable current source circuit in the present application.

[0034] Figure 4 It is a simulation result schematic diagram of the photoelectric conversion circuit, the negative feedback amplification circuit and the adjustable current source circuit in the present application.

[0035] The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings in combination with the embodiments. DETAILED DESCRIPTION

[0036] It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0037] As Figure 1As shown, this invention provides a tunable semiconductor laser wavelength tuning system based on photoelectric feedback. During the calibration and normal operation of the modulation grating Y laser, the photoelectric feedback loop collects the laser output optical power in real time through a beam splitter, forming negative feedback at the SOA current. Only the left current, right current, and phase current need to be input, and the feedback system will automatically match a suitable SOA current for power compensation. The photoelectric feedback loop includes an adjustable potentiometer, allowing manual adjustment of the required output optical power. Figure 1 The diagram shows a block diagram of a modulation grating Y laser application system, including a user control module, a modulation grating Y laser, a photoelectric feedback device, and a user application optical path. The user control module is connected to the modulation grating Y laser, the modulation grating Y laser is connected to the photoelectric feedback device, and the photoelectric feedback device is connected to the user application optical path.

[0038] (1) Modulated grating Y laser

[0039] like Figure 2 As shown, the modulation grating Y laser includes a left sampling grating, a right sampling grating, a multimode interference (MMI) 1x2 coupler, a phase adjustment module, a gain control module, and an SOA semiconductor optical amplifier. The left and right sampling gratings are both connected to the multimode interference coupler, which is connected to the phase adjustment. The phase adjustment module, gain control module, and SOA semiconductor optical amplifier are connected in sequence.

[0040] The left sampling grating, right sampling grating, phase adjustment module, gain control module, and SOA semiconductor optical amplifier are all driven by constant current. The left and right sampling gratings, as reflectors, are two comb-shaped gratings with multiple reflection peaks and a small difference in the spacing between the comb peaks. The two comb-shaped gratings form a vernier effect, causing the coupler to return a reflection peak of a specific wavelength after superposition. This peak is then input into the gain control region for longitudinal mode screening. The phase adjustment module is used to realize longitudinal mode shifting and broaden the spectral range of each longitudinal mode. The SOA semiconductor amplifier is used for optical power compensation to ensure high output optical power within the tuning range and high stability.

[0041] (2) Photoelectric feedback device

[0042] The photoelectric feedback device includes a beam splitter (1x2 optical splitter with a splitting ratio of 1:99), an optical isolator, a photoelectric conversion circuit, a negative feedback amplifier circuit, and an adjustable current source circuit. The beam splitter and the adjustable current source circuit are both connected to the modulation grating Y laser. The beam splitter is also connected to the optical isolator and the photoelectric conversion circuit. The optical isolator is connected to the user application optical path. The photoelectric conversion circuit is connected to the negative feedback amplifier circuit, and the negative feedback amplifier circuit is connected to the adjustable current source circuit.

[0043] When the system is working, the user control module inputs left current, right current, phase current and GAIN current (gain current) to the modulated grating Y laser, the output light of the modulated grating Y laser passes through the optical splitter, the splitting ratio of which is 1:99, the 99% part of the output light enters the optical isolator and then enters the user application light path; the 1% part of the output light enters the photoelectric conversion circuit to convert the feedback light signal into a feedback electric signal, the feedback electric signal is input to the negative feedback amplification circuit, and then the adjustable current source circuit is controlled to control the SOA current output to the modulated grating Y laser, so as to change the output light power.

[0044] Wherein,

[0045] The optical isolator is used to prevent the interference of the back light in the user application on the photoelectric feedback system.

[0046] The main function of the photoelectric conversion circuit is to convert the feedback light signal into an electric signal.

[0047] The negative feedback amplification circuit is used to reverse and amplify the feedback electric signal, the reverse function is that when the output light power of the modulated grating Y laser decreases, the 1% feedback light decreases, the corresponding feedback electric signal decreases, at this time, the SOA current needs to be increased, so the adjustable current source circuit needs to be controlled to increase the output; the amplification function is mainly to match the fluctuation range of the feedback light signal with the input range of the adjustable current source circuit.

[0048] Based on the photoelectric feedback device proposed in the application, during the calibration and normal working process of the modulated grating Y laser, the photoelectric feedback system will automatically generate the corresponding SOA current after the user control module inputs the left current, right current, phase current and GAIN current (gain current) each time. During the calibration process, the photoelectric feedback device proposed in the application is introduced, which is equivalent to inputting a phase current, and the phase current and the SOA current are adjusted and controlled simultaneously, so that the phase current and the SOA current can realize accurate calibration together, so as to realize accurate calibration of the output wavelength and the light power, without the need of cyclic and successive approximation calibration of the phase current and the SOA current, thereby improving the calibration accuracy and reducing the calibration time. Meanwhile, in the negative feedback amplification circuit, the application designs an adjustable potentiometer to adjust the negative feedback amplification multiple, so as to adjust the output light power during calibration; during the actual application process, the left current, right current, phase current and GAIN current are output according to the calibrated current, and the output light power is modulated by the photoelectric feedback system, so as to automatically match the SOA current during calibration, so as to achieve the output wavelength and the light power during calibration.

[0049] As Figure 3 The application circuit diagram of the photoelectric conversion circuit, the negative feedback amplification circuit and the adjustable current source circuit is shown in the figure, which specifically comprises:

[0050] Constant current source I3, capacitor C1, first resistor R1, second resistor R3, third resistor R4, fourth resistor R5, fifth resistor R6, sixth resistor R10, first operational amplifier X8, second operational amplifier X9, third operational amplifier X10, 2N3904 transistor Q1, light emitting diode D1;

[0051] One end of the constant current source I3 is grounded, the other end is connected with one end of the capacitor C1, one end of the first resistor R1 and the reverse input end of the first operational amplifier X8, the other end of the capacitor C1 and the other end of the first resistor R1 converge and are connected with the output end of the first operational amplifier X8 and the non-inverting input end of the second operational amplifier X9, the non-inverting input end of the first operational amplifier X8 is grounded, the reverse input end and the output end of the second operational amplifier X9 are connected with one end of the second resistor R3, the other end of the second resistor R3 is connected with the reverse input end of the third operational amplifier X10 and one end of the fifth resistor R6, the non-inverting input end of the third operational amplifier X10 is connected with one end of the third resistor R4 and one end of the fourth resistor R5, the other end of the third resistor R4 is connected with a power supply, the other end of the fourth resistor R5 is grounded, the other end of the fifth resistor R6 and the output end of the third operational amplifier X10 are connected with the base of the 2N3904 transistor Q1, the collector of the 2N3904 transistor Q1 is connected with a power supply, the emitter of the 2N3904 transistor Q1 is connected with one end of the sixth resistor R10, the other end of the sixth resistor R10 is connected with the anode of the light emitting diode D1, and the cathode of the light emitting diode D1 is grounded.

[0052] As Figure 3 The circuit diagram shown in the case: the output light power standard value of the tunable grating Y laser is 20mW, the initial calibration light power calibration range is ±2mW, the SOA standard current is 110mA, and the adjustable range is ±20mA. The circuit uses a current source to simulate a photoelectric collection tube, uses a phototube to simulate a laser, and after light splitting through a 1:99 optical splitter, the light signal entering the feedback system is 0.18mW to 0.22mW, and after conversion through a 1A / W phototube, the current is 0.18mA to 0.22mA, so the range of the simulated current source is 0.18mA to 0.22mA, and the simulation result is shown in Figure 4 .

[0053] The application also provides a tunable semiconductor laser wavelength tuning method based on photoelectric feedback, which is based on the tunable semiconductor laser wavelength tuning system as described above, and specifically comprises the following steps:

[0054] S1, the user control module inputs left current, right current, phase current and gain current to the modulated grating Y laser;

[0055] S2, in the modulation grating Y laser, the left sampling grating and the right sampling grating are used as comb-shaped gratings, the vernier effect is formed by using the two comb-shaped gratings, the reflection peak of a specific wavelength is returned after the superposition of the multimode interference coupler, the gain control module is input, the longitudinal mode is selected, the phase adjustment module is used to realize the longitudinal mode movement, the spectral range of tuning under each longitudinal mode is widened, and the optical power compensation is performed on the SOA semiconductor amplifier; and the optical power in a set range is output;

[0056] S3, the output light of the modulation grating Y laser passes through a light splitter, the splitting ratio of the light splitter is 1:99, 99% of the light is output and enters the optical isolator, and then enters the user application light path;

[0057] 1% of the light is output and enters the photoelectric conversion circuit to convert the feedback optical signal into a feedback electrical signal; and the feedback electrical signal is input into the negative feedback amplification circuit;

[0058] S4, the negative feedback amplification circuit is used to perform reverse and amplification on the feedback electrical signal;

[0059] Reverse: when the output optical power of the modulation grating Y laser decreases, the 1% feedback light decreases, the corresponding feedback electrical signal decreases, at this time, the SOA current is increased, the output of the adjustable current source circuit is increased;

[0060] Amplification: the fluctuation range of the feedback optical signal is greatly matched with the input range of the adjustable current source circuit;

[0061] S5, the feedback electrical signal output by the negative feedback amplification circuit is used to control the adjustable current source circuit, so that the SOA current output to the modulation grating Y laser is controlled, so that the output optical power is changed.

[0062] The output optical power is optoelectronically collected, fed back to the SOA current, and automatically matched with the SOA current, so that the optical power is cooperatively tuned. The output optical power is adjusted by using the optoelectronic feedback device, especially in the calibration process of the tuning grating Y laser, the optoelectronic feedback system can realize accurate wavelength and optical power calibration, and the calibration time is changed from the cyclic successive approximation calibration to single calibration, so that accurate wavelength and optical power can be realized, and the calibration efficiency is improved.

[0063] It should be noted that, in this document, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, device, article or method including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, device, article or method. Without more limitation, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, device, article or method including the element.

[0064] The above merely provides the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structure or equivalent flowchart transformation, or direct or indirect application in other related technical fields, which is made according to the contents of the present application specification and drawings, shall be included in the patent protection scope of the present application.

Claims

1. A wavelength tuning system for a tunable semiconductor laser based on photoelectric feedback, characterized in that, It includes a user control module, a modulated grating Y laser, a photoelectric feedback device, and a user application optical path. The user control module is connected to the modulated grating Y laser, the modulated grating Y laser is connected to the photoelectric feedback device, and the photoelectric feedback device is connected to the user application optical path. The photoelectric feedback device includes a beam splitter, an optical isolator, a photoelectric conversion circuit, a negative feedback amplifier circuit, and an adjustable current source circuit. The beam splitter and the adjustable current source circuit are both connected to the modulation grating Y laser. The beam splitter is also connected to the optical isolator and the photoelectric conversion circuit. The optical isolator is connected to the user application optical path. The photoelectric conversion circuit is connected to the negative feedback amplifier circuit. The negative feedback amplifier circuit is connected to the adjustable current source circuit. The user control module inputs left current, right current, phase current, and gain current to the modulation grating Y laser. The output light of the modulation grating Y laser passes through a beam splitter. According to the splitting ratio of the beam splitter, part of the output light enters the optical isolator and then enters the user application optical path. The other part of the output light enters the photoelectric conversion circuit to convert the feedback optical signal into a feedback electrical signal. The feedback electrical signal is input to the negative feedback amplifier circuit, which in turn controls the adjustable current source circuit to control the SOA current output to the modulation grating Y laser, thereby changing the output optical power.

2. The wavelength tuning system for a tunable semiconductor laser based on photoelectric feedback according to claim 1, characterized in that, The photoelectric conversion circuit, negative feedback amplifier circuit, and adjustable current source circuit specifically include: Constant current source I3, capacitor C1, first resistor R1, second resistor R3, third resistor R4, fourth resistor R5, fifth resistor R6, sixth resistor R10, first operational amplifier X8, second operational amplifier X9, third operational amplifier X10, 2N3904 transistor Q1, light-emitting diode D1; One end of the constant current source I3 is grounded, and the other end is connected to one end of capacitor C1, one end of the first resistor R1, and the inverting input terminal of the first operational amplifier X8. The other end of capacitor C1 and the other end of the first resistor R1 converge and are connected to the output terminal of the first operational amplifier X8 and the non-inverting input terminal of the second operational amplifier X9. The non-inverting input terminal of the first operational amplifier X8 is grounded. The inverting input terminal and the output terminal of the second operational amplifier X9 are both connected to one end of the second resistor R3. The other end of the second resistor R3 is connected to the inverting input terminal of the third operational amplifier X10 and one end of the fifth resistor R6. The non-inverting input of the third operational amplifier X10 is connected to one end of the third resistor R4 and one end of the fourth resistor R5. The other end of the third resistor R4 is connected to the power supply, and the other end of the fourth resistor R5 is grounded. The other end of the fifth resistor R6 and the output of the third operational amplifier X10 are both connected to the base of the 2N3904 transistor Q1. The collector of the 2N3904 transistor Q1 is connected to the power supply. The emitter of the 2N3904 transistor Q1 is connected to one end of the sixth resistor R10. The other end of the sixth resistor R10 is connected to the anode of the light-emitting diode D1, and the cathode of the light-emitting diode D1 is grounded.

3. The wavelength tuning system for a tunable semiconductor laser based on photoelectric feedback according to claim 2, characterized in that, The beam splitter is a 1x2 optical splitter with a splitting ratio of 1:

99. 99% of the emitted light enters the optical isolator, and 1% of the emitted light enters the photoelectric conversion circuit.

4. The wavelength tuning system for a tunable semiconductor laser based on photoelectric feedback according to claim 3, characterized in that, In the photoelectric feedback device The optical isolator is used to prevent backlighting in user applications from interfering with the photoelectric feedback system. The negative feedback amplifier circuit is used to reverse and amplify the feedback electrical signal. The reverse function is that when the output optical power of the modulated grating Y laser decreases, the 1% feedback light decreases, and the corresponding feedback electrical signal decreases. At this time, the SOA current needs to be increased, so the adjustable current source circuit needs to be controlled to increase the output. The amplification function is to match the fluctuation range of the feedback optical signal with the input range of the adjustable current source circuit.

5. The wavelength tuning system for a tunable semiconductor laser based on photoelectric feedback according to claim 4, characterized in that, The modulation grating Y laser includes a left sampling grating, a right sampling grating, a multimode interference coupler, a phase adjustment module, a gain control module, and an SOA semiconductor optical amplifier. The left and right sampling gratings are both connected to the multimode interference coupler, which is connected to the phase adjustment module. The phase adjustment module, gain control module, and SOA semiconductor optical amplifier are connected in sequence. The left sampling grating, right sampling grating, phase adjustment module, gain control module, and SOA semiconductor optical amplifier are all driven by constant current. The left and right sampling gratings, as reflectors, are two comb gratings with multiple reflection peaks. The two comb gratings form a vernier effect, causing the multimode interference coupler to return a reflection peak of a specific wavelength after superposition. This peak is then input to the gain control module for longitudinal mode selection. The phase adjustment module is used to realize longitudinal mode shifting and broaden the spectral range of each longitudinal mode. The SOA semiconductor amplifier is used for optical power compensation to ensure that the output optical power within the set range is within the tuning range.

6. A wavelength tuning method for a tunable semiconductor laser based on photoelectric feedback, characterized in that, Based on the tunable semiconductor laser wavelength tuning system according to claim 5, the method specifically includes: S1. The user control module inputs the left current, right current, phase current, and gain current to the modulation grating Y laser; S2. In the modulated grating Y laser, the left sampling grating and the right sampling grating are used as comb gratings. The two comb gratings form a vernier effect, so that the reflection peak of a specific wavelength is returned after the multimode interference coupler is superimposed. The input gain control module performs longitudinal mode screening, the phase adjustment module realizes longitudinal mode shifting, and widens the spectral range of each longitudinal mode. The SOA semiconductor amplifier performs optical power compensation and outputs optical power within a set range. S3. The output light of the modulated grating Y laser passes through a beam splitter with a splitting ratio of 1:

99. 99% of the output light enters the optical isolator and then enters the user application optical path. One percent of the emitted light enters the photoelectric conversion circuit to convert the feedback optical signal into a feedback electrical signal, which is then input to the negative feedback amplifier circuit. S4. The negative feedback amplifier circuit inverts and amplifies the feedback electrical signal; Conversely: When the output optical power of the modulated grating Y laser decreases, the 1% feedback light decreases, and the corresponding feedback electrical signal decreases. At this time, the SOA current is increased to control the adjustable current source circuit to increase the output. Amplification: The fluctuation range of the feedback optical signal is well matched with the input range of the adjustable current source circuit; S5. The feedback electrical signal output by the negative feedback amplifier circuit controls the adjustable current source circuit to control the SOA current output to the modulation grating Y laser, thereby changing the output optical power.

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