Wavelength-variable light source module based on PWM temperature control

Abstract

This utility model describes a wavelength-variable light source module based on PWM temperature control, belonging to the field of optical communication technology. It includes a housing, a power indicator light, and a fiber optic jumper. The housing houses an MCU control circuit, an active low-pass filter, an H-bridge gating circuit, a temperature-controlled constant current circuit, an output optical power acquisition circuit, and an RS422 communication circuit. The MCU control circuit uses an Atmega S128 microcontroller. It controls the active low-pass filter via PWM signals to convert the signal into voltage, and then controls the temperature-controlled constant current circuit via the H-bridge gating circuit to achieve precise temperature control of the laser, thereby adjusting the wavelength. Simultaneously, the output optical power acquisition circuit converts the optical signal into an electrical signal and feeds it back to the MCU control circuit.

Description

Technical Field

[0001] This utility model belongs to the field of optical communication technology, specifically relating to a wavelength-variable light source module based on PWM temperature control. Background Technology

[0002] In the field of optical communication, the laser seed source, as a core component of the laser, directly affects the quality and stability of the optical signal. However, current seed sources generally suffer from limitations, such as the fixed wavelength of most seed sources, making it difficult to meet the diverse wavelength requirements of practical applications. While some seed sources can achieve wavelength adjustment, this often involves combining multiple lasers, which not only increases cost and size but also enhances control complexity. Furthermore, traditional methods struggle to achieve precise temperature control, thus affecting the accurate adjustment of the wavelength and failing to meet the needs of applications requiring high wavelength precision. Additionally, output optical power monitoring is also impossible.

[0003] A prior art technology, CN206292643U, describes a switchable semiconductor laser temperature control system. This system samples the temperature of a thermoelectric cooler (TEC) via a data sampling circuit and feeds this data back to a microcontroller. The microcontroller then uses a neural network control algorithm to calculate the control variable based on the temperature difference. This variable, along with a PWM drive circuit, generates a drive current to control the TEC, thereby heating or cooling the laser and achieving constant temperature control. However, this system relies on a single-channel temperature control circuit, resulting in insufficient temperature control accuracy and a lack of real-time monitoring of the output optical power. Utility Model Content

[0004] The technical problem solved by this utility model is to overcome the defects in the existing technology and provide a wavelength variable light source module based on PWM temperature control.

[0005] The technical solution adopted in this utility model is as follows:

[0006] The wavelength-variable light source module based on PWM temperature control described in this utility model includes a housing. The exterior of the housing has a power indicator light and a fiber optic jumper. The interior contains a power supply. Inside the housing, there is also an MCU control circuit, an active low-pass filter, an H-bridge gating circuit, a temperature-controlled constant current circuit, an output optical power acquisition circuit, and an RS422 communication circuit. The MCU control circuit is connected to the active low-pass filter, the H-bridge gating circuit, and the RS422 communication circuit. The active low-pass filter and the H-bridge gating circuit are both connected to the temperature-controlled constant current circuit. The temperature-controlled constant current circuit is connected to a laser. The laser is connected to the output optical power acquisition circuit, which is connected to the MCU control circuit.

[0007] The MCU control circuit includes a microcontroller, which is an AtmegaS128 microcontroller. The microcontroller is connected to resistors R1-R4, capacitors C1-C12, LED D1, ferrite beads L1-L2, and crystal oscillator X1. The pin connections of the microcontroller are as follows:

[0008] Pin PE5 is connected to the negative terminal of LED D1, and the positive terminal of LED D1 is connected to resistor R1, which is connected to the power supply.

[0009] Pin PEN is connected to resistor R2, and resistor R2 is connected to the power supply.

[0010] Pin XTAL1 is connected to capacitors C1 and C2 in sequence and then grounded; pin XTAL1 is connected to the crystal X with resistors R3 and R4 in parallel; crystal X1 is connected to ferrite bead L1 and capacitor C3; ferrite bead L1 is connected to the power supply; capacitor C3 is connected to capacitor C4 and then grounded.

[0011] Pin VCC is connected to capacitors C5 and C6 in sequence and then grounded; pin VCC is connected to capacitors C7 and C8 in sequence and then grounded.

[0012] The AVCC pin is connected to capacitors C9 and C10 in sequence and then grounded. The AVCC pin is connected to ferrite bead L2 and then to the power supply.

[0013] The AREF pin is connected to capacitors C11 and C12 in sequence and then grounded.

[0014] An active low-pass filter includes a PWM coarse-tuning circuit and a PWM fine-tuning circuit;

[0015] The PWM coarse adjustment circuit includes comparator A1, resistors R5 to R6, and capacitors C13 to C14. The non-inverting input of comparator A1 is connected to resistor R5 and capacitor C13 respectively. Capacitor C13 is grounded. The output of comparator A1 is connected to resistor R6. Resistor R6 is connected to capacitor C14. Both capacitors C13 and C14 are grounded. The inverting input of comparator A1 is connected to the output of comparator A1.

[0016] The PWM fine-tuning circuit includes comparator A2, resistors R7 to R8, and capacitors C15 to C16. The non-inverting input of comparator A2 is connected to resistor R7 and capacitor C15, respectively. Capacitor C15 is grounded. The output of comparator A2 is connected to resistor R8. Resistor R8 is connected to capacitor C16. Both capacitors C15 and C16 are grounded. The inverting input of comparator A2 is connected to the output of comparator A2.

[0017] The H-bridge gating circuit includes transistors Q1 to Q4 and resistors R9 to R12;

[0018] Resistors R9 to R12 are connected to the bases of transistors Q1 to Q4 respectively. The collectors of transistors Q1 and Q3 are connected to the power supply. The emitters of transistors Q2 and Q4 are grounded. The emitter of transistor Q1 is connected to the collector of transistor Q2, and the emitter of transistor Q3 is connected to the collector of transistor Q4.

[0019] The temperature-controlled constant current circuit includes a first temperature-controlled constant current circuit and a second temperature-controlled constant current circuit.

[0020] The first temperature-controlled constant current circuit includes resistors R13 to R17, capacitors C17 to C18, comparator A3, and transistor Q5. Resistors R13 and capacitor C17 are both connected to the non-inverting input of comparator A3, capacitor C17 is grounded, resistor R14 is connected between the output of comparator A3 and the base of transistor Q5, the inverting input of comparator A3 is connected to resistors R15 and R16 in sequence, the emitter of transistor Q5 and one end of resistor R17 are both connected between resistors R15 and R16, the other end of resistor R17 is grounded, and capacitor C18 is connected between the output of comparator A3 and the inverting input of comparator A3.

[0021] The second temperature-controlled constant current circuit includes resistors R18-R22, capacitors C19-C20, comparator A4, and transistor Q6. Resistor R18 and capacitor C19 are both connected to the non-inverting input of comparator A4, capacitor C19 is grounded, and resistor R19 is connected between the output of comparator A4 and the base of transistor Q6. The inverting input of comparator A4 is connected to resistors R20 and R21 in sequence. The emitter of transistor Q6 and one end of resistor R22 are both connected between resistors R20 and R21, and the other end of resistor R22 is grounded. Capacitor C20 is connected between the output of comparator A4 and the inverting input of comparator A4. The collector of transistor Q5 is connected to the collector of transistor Q6.

[0022] The output optical power acquisition circuit includes operational amplifier A5 and resistors R23 to R25. The non-inverting input terminal of operational amplifier A5 is grounded, and the output terminal of operational amplifier A5 is connected to resistors R23, R24 and R25 respectively. Resistor R23 is connected to the inverting input terminal of operational amplifier A5, and resistor R25 is grounded.

[0023] The RS422 communication circuit includes a transmitting communication circuit and a receiving communication circuit;

[0024] The transmitting communication circuit includes a driver, resistors R26 to R30, and capacitors C21 to C22. The driver model is AM26LS31CDR, and the pin connections of the driver are as follows:

[0025] Pin EN is not connected to resistor R26; resistor R26 is grounded.

[0026] Pin EN is connected to resistor R27, and resistor R27 is connected to the power supply.

[0027] Pin INA is connected to TXD;

[0028] Pins INB, INC, and IND are all connected to resistor R28, which is grounded.

[0029] The VCC pin is connected to capacitors C22 and C21 in sequence, and capacitor C21 is grounded.

[0030] Pin OUTA is connected to resistor R29;

[0031] Pin OUTA is not connected to resistor R30.

[0032] The receiving communication circuit includes a receiver, resistors R31 to R38, capacitors C23 to C24, and diode D2. The receiver model is AM26LS3CDR, and the pin connections of the receiver are as follows:

[0033] Pin EN is not connected to resistor R31, and resistor R31 is grounded;

[0034] Pin EN is connected to resistor R32, and resistor R32 is connected to the power supply.

[0035] Pin INA+ is connected to resistors R33, R35 and R34 in sequence, and resistor R34 is connected to pin INA-.

[0036] The positive terminal of diode D2 is connected to the power supply, and the negative terminal of diode D2 is connected to resistor R36. Resistor R36 is connected between resistors R35 and R33. One end of resistor R37 is connected between resistors R35 and R34, and the other end is grounded.

[0037] Pin VDD is connected to capacitors C24 and C23 in sequence and then grounded;

[0038] Connect pin OUTA to resistor R38.

[0039] This utility model has the following beneficial effects:

[0040] 1. The MCU control circuit outputs a PWM signal, which is converted into a voltage signal by an active low-pass filter, to achieve precise control of the laser temperature and effectively overcome the problems of fixed wavelength and complex adjustment.

[0041] 2. The temperature control constant current circuit and H-bridge gating circuit effectively improve the temperature control accuracy, enabling the laser temperature to stabilize near the set value, thereby improving the accuracy and stability of wavelength adjustment.

[0042] 3. The H-bridge gating circuit controls the conduction and cutoff of the transistor to change the direction of the current, thereby controlling the cooling and heating of the laser. This enables the laser to operate stably over a wider temperature range and enhances the module's environmental adaptability.

[0043] 4. The output optical power acquisition circuit converts the optical signal output by the laser into an electrical signal through a PIN diode, and feeds it back to the MCU control circuit after being conditioned by an operational amplifier. This enables real-time monitoring of the output optical power, which facilitates timely detection and adjustment of the output status of the light source, ensuring the quality of optical communication and overcoming the deficiency of some light source modules in the existing technology that cannot be monitored in real time.

[0044] 5. In the MCU control circuit, resistors, capacitors, ferrite beads and crystal oscillators are reasonably configured to provide the microcontroller with a stable clock signal and power supply filtering, ensuring its reliable operation.

[0045] 6. The RS422 communication circuit communicates with the host computer, ensuring the transmission quality of control signals and improving the reliability and stability of the system. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the external structure of this utility model;

[0047] Figure 2 This is a diagram of the electrical connection system of this utility model;

[0048] Figure 3 This is the schematic diagram of the MCU control circuit.

[0049] Figure 4 This is a schematic diagram of an active low-pass filter circuit.

[0050] Figure 5 This is the schematic diagram of the H-bridge gating circuit;

[0051] Figure 6 This is a schematic diagram of a temperature-controlled constant current circuit.

[0052] Figure 7 Schematic diagram of the output optical power acquisition circuit;

[0053] Figure 8 This is a schematic diagram of the communication circuit for transmission.

[0054] Figure 9 This is a schematic diagram of a receiving communication circuit. Detailed Implementation

[0055] like Figures 1 to 9As shown, the wavelength-variable light source module based on PWM temperature control of this utility model includes a housing. The exterior of the housing is equipped with a power indicator light and a fiber optic jumper. The interior of the housing contains a power supply. Inside the housing, there is also an MCU control circuit, an active low-pass filter, an H-bridge gating circuit, a temperature-controlled constant current circuit, an output optical power acquisition circuit, and an RS422 communication circuit. The MCU control circuit is connected to the active low-pass filter, the H-bridge gating circuit, and the RS422 communication circuit. The active low-pass filter and the H-bridge gating circuit are both connected to the temperature-controlled constant current circuit. The temperature-controlled constant current circuit is connected to a laser. The laser is connected to the output optical power acquisition circuit, and the output optical power acquisition circuit is connected to the MCU control circuit.

[0056] The MCU control circuit includes a microcontroller, which is an AtmegaS128 microcontroller. The microcontroller is connected to resistors R1-R4, capacitors C1-C12, LED D1, ferrite beads L1-L2, and crystal oscillator X1. The pin connections of the microcontroller are as follows:

[0057] Pin PE5 is connected to the negative terminal of LED D1, and the positive terminal of LED D1 is connected to resistor R1, which is connected to the power supply.

[0058] Pin PEN is connected to resistor R2, and resistor R2 is connected to the power supply.

[0059] Pin XTAL1 is connected to capacitors C1 and C2 in sequence and then grounded; pin XTAL1 is connected to the crystal X with resistors R3 and R4 in parallel; crystal X1 is connected to ferrite bead L1 and capacitor C3; ferrite bead L1 is connected to the power supply; capacitor C3 is connected to capacitor C4 and then grounded.

[0060] Pin VCC is connected to capacitors C5 and C6 in sequence and then grounded; pin VCC is connected to capacitors C7 and C8 in sequence and then grounded.

[0061] The AVCC pin is connected to capacitors C9 and C10 in sequence and then grounded. The AVCC pin is connected to ferrite bead L2 and then to the power supply.

[0062] The AREF pin is connected to capacitors C11 and C12 in sequence and then grounded.

[0063] An active low-pass filter includes a PWM coarse-tuning circuit and a PWM fine-tuning circuit;

[0064] The PWM coarse adjustment circuit includes comparator A1, resistors R5 to R6, and capacitors C13 to C14. The non-inverting input of comparator A1 is connected to resistor R5 and capacitor C13 respectively. Capacitor C13 is grounded. The output of comparator A1 is connected to resistor R6. Resistor R6 is connected to capacitor C14. Both capacitors C13 and C14 are grounded. The inverting input of comparator A1 is connected to the output of comparator A1.

[0065] The PWM fine-tuning circuit includes comparator A2, resistors R7 to R8, and capacitors C15 to C16. The non-inverting input of comparator A2 is connected to resistor R7 and capacitor C15, respectively. Capacitor C15 is grounded. The output of comparator A2 is connected to resistor R8. Resistor R8 is connected to capacitor C16. Both capacitors C15 and C16 are grounded. The inverting input of comparator A2 is connected to the output of comparator A2.

[0066] The H-bridge gating circuit includes transistors Q1 to Q4 and resistors R9 to R12;

[0067] Resistors R9 to R12 are connected to the bases of transistors Q1 to Q4 respectively. The collectors of transistors Q1 and Q3 are connected to the power supply. The emitters of transistors Q2 and Q4 are grounded. The emitter of transistor Q1 is connected to the collector of transistor Q2, and the emitter of transistor Q3 is connected to the collector of transistor Q4.

[0068] The temperature-controlled constant current circuit includes a first temperature-controlled constant current circuit and a second temperature-controlled constant current circuit.

[0069] The first temperature-controlled constant current circuit includes resistors R13 to R17, capacitors C17 to C18, comparator A3, and transistor Q5. Resistors R13 and capacitor C17 are both connected to the non-inverting input of comparator A3, capacitor C17 is grounded, resistor R14 is connected between the output of comparator A3 and the base of transistor Q5, the inverting input of comparator A3 is connected to resistors R15 and R16 in sequence, the emitter of transistor Q5 and one end of resistor R17 are both connected between resistors R15 and R16, the other end of resistor R17 is grounded, and capacitor C18 is connected between the output of comparator A3 and the inverting input of comparator A3.

[0070] The second temperature-controlled constant current circuit includes resistors R18-R22, capacitors C19-C20, comparator A4, and transistor Q6. Resistor R18 and capacitor C19 are both connected to the non-inverting input of comparator A4, capacitor C19 is grounded, and resistor R19 is connected between the output of comparator A4 and the base of transistor Q6. The inverting input of comparator A4 is connected to resistors R20 and R21 in sequence. The emitter of transistor Q6 and one end of resistor R22 are both connected between resistors R20 and R21, and the other end of resistor R22 is grounded. Capacitor C20 is connected between the output of comparator A4 and the inverting input of comparator A4. The collector of transistor Q5 is connected to the collector of transistor Q6.

[0071] The output optical power acquisition circuit includes operational amplifier A5 and resistors R23 to R25. The non-inverting input terminal of operational amplifier A5 is grounded, and the output terminal of operational amplifier A5 is connected to resistors R23, R24 and R25 respectively. Resistor R23 is connected to the inverting input terminal of operational amplifier A5, and resistor R25 is grounded.

[0072] The RS422 communication circuit includes a transmitting communication circuit and a receiving communication circuit;

[0073] The transmitting communication circuit includes a driver, resistors R26 to R30, and capacitors C21 to C22. The driver model is AM26LS31CDR, and the pin connections of the driver are as follows:

[0074] Pin EN is not connected to resistor R26; resistor R26 is grounded.

[0075] Pin EN is connected to resistor R27, and resistor R27 is connected to the power supply.

[0076] Pin INA is connected to TXD;

[0077] Pins INB, INC, and IND are all connected to resistor R28, which is grounded.

[0078] The VCC pin is connected to capacitors C22 and C21 in sequence, and capacitor C21 is grounded.

[0079] Pin OUTA is connected to resistor R29;

[0080] Pin OUTA is not connected to resistor R30.

[0081] The receiving communication circuit includes a receiver, resistors R31 to R38, capacitors C23 to C24, and diode D2. The receiver model is AM26LS3CDR, and the pin connections of the receiver are as follows:

[0082] Pin EN is not connected to resistor R31, and resistor R31 is grounded;

[0083] Pin EN is connected to resistor R32, and resistor R32 is connected to the power supply.

[0084] Pin INA+ is connected to resistors R33, R35 and R34 in sequence, and resistor R34 is connected to pin INA-.

[0085] The positive terminal of diode D2 is connected to the power supply, and the negative terminal of diode D2 is connected to resistor R36. Resistor R36 is connected between resistors R35 and R33. One end of resistor R37 is connected between resistors R35 and R34, and the other end is grounded.

[0086] Pin VDD is connected to capacitors C24 and C23 in sequence and then grounded;

[0087] Connect pin OUTA to resistor R38.

[0088] Specifically, this technical solution uses the AtmegaS128 microcontroller as the main control chip for remote control and telemetry, which is used to control the enable switch of the laser and to control the operating temperature and wavelength of the laser through PWM modulation signals. At the same time, it can also upload the monitoring data of the laser's operating current, operating temperature and output power through an A / D converter.

[0089] Specifically, the active low-pass filter consists of an RC filter and a comparator. The PWM coarse adjustment circuit and the PWM fine adjustment circuit convert PWM signals with different duty cycles into the required voltage control signals. The time constant of the RC filter is much larger than the period of the PWM signal. All selected control waveforms are 3.3V and 10Hz. The PWM coarse adjustment circuit and the PWM fine adjustment circuit can achieve voltage regulation from 0 to 3.3V.

[0090] Specifically, the H-bridge gating circuit is used to control the cooling and heating of the laser, that is, to regulate the temperature of the laser. When the AtmegaS128 microcontroller sends a high TEC_C signal, it is converted to TEC_CTRL after being isolated by a follower. At the same time, this signal is converted into a non-TEC_CTRL signal by an inverter. At this time, transistors Q1 and Q4 are turned on, while transistors Q2 and Q3 are turned off. The current flows from TEC- to TEC+, realizing cooling and temperature reduction. The opposite is true for heating and temperature rise.

[0091] Specifically, in the first temperature-controlled constant current circuit, when current flows through resistor R17, a voltage drop is generated. This voltage drop is captured by comparator A3 and compared with the set value V. REF By making comparisons, the current control function is ultimately achieved. For example, when transistor Q5 is turned on, a current I is generated, which in turn generates a voltage V at the position of resistor R17. R17 At this point, the voltage representing the current magnitude enters comparator A3 after being current-limited by resistor R15, and the voltage V... R17 Comparison voltage V (preset) REF When comparing, when V R17 Greater than V REF When the current is at a certain time, the comparator is turned off; otherwise, the comparator is turned on. This controls the transistor Q5 so that the current flowing through the transistor Q5 reaches the preset value, thereby achieving constant current control. The constant current control of the second temperature control constant current circuit is the same.

[0092] Specifically, the magnitudes controlled by the first and second temperature-controlled constant current circuits depend on the resistance values ​​of resistors R17 and R22, respectively. The first temperature-controlled constant current circuit, after PWM modulation, can be controlled from 0 to 3A, while the second temperature-controlled constant current circuit can be controlled from 0.01 to 0.1A to achieve laser temperature control to two decimal places. The total current is calculated as follows:

[0093] I 总 =V_EMP×R17+V_WL×R22

[0094] Substitute the PWM signal:

[0095] I 总 =(V PWM_TEMP ×duty cycle)×R17+(V PWM_WL (×duty cycle)×R22

[0096] Specifically, the laser converts the acquired output optical signal into an electrical signal via a PIN diode, and then modulates it into a proportional signal using operational amplifier A5 before sending it to the microcontroller to monitor the output optical power. The output voltage V of the output optical power acquisition circuit... OUT The relationship with optical power is as follows:

[0097]

[0098] Specifically, the RS422 communication circuit includes a transmitting communication circuit with the AM26LS31CDR driver as its core and a receiving communication circuit with the AM26LS32CDR receiver as its core. Both the driver and receiver are surface-mount packaged and supplied with a voltage of 3.3V.

[0099] Specifically, a 5V / 2A constant current source is connected to the power supply, and an RS422 communication cable is used to connect to a host computer for laser enable control and temperature adjustment. The laser output power is measured using an optical power meter, and the actual measured light source voltage is 5-10mV. The laser constant current is 180mA, and the maximum current of the cooler is 2.3A, the maximum voltage is 2.5V, and the maximum power consumption is 4.5W.

[0100] Specifically, the laser will operate stably near the set temperature. The temperature-to-wavelength tuning factor is generally 0.02nm / ℃. To achieve the predetermined target, a high-precision laser temperature control circuit needs to be designed. Therefore, through a PWM coarse adjustment circuit and a PWM fine adjustment circuit, one circuit provides a wide range of coarse adjustment at the ampere level, while the other circuit provides fine adjustment at the mA level, so that the temperature is precisely controlled near the temperature point.

Claims

1. A PWM temperature control-based wavelength variable light source module, comprising a shell, an external power indicator and a fiber jumper are arranged on the shell, and a power supply is arranged in the shell, characterized in that, The housing also includes an MCU control circuit, an active low-pass filter, an H-bridge gating circuit, a temperature-controlled constant current circuit, an output optical power acquisition circuit, and an RS422 communication circuit. The MCU control circuit is connected to the active low-pass filter, the H-bridge gating circuit, and the RS422 communication circuit. The active low-pass filter and the H-bridge gating circuit are both connected to the temperature-controlled constant current circuit. The temperature-controlled constant current circuit is connected to a laser. The laser is connected to the output optical power acquisition circuit, and the output optical power acquisition circuit is connected to the MCU control circuit.

2. The PWM temperature-controlled wavelength variable light source module according to claim 1, wherein, The MCU control circuit includes a microcontroller, which is an AtmegaS128 microcontroller. The microcontroller is connected to resistors R1-R4, capacitors C1-C12, LED D1, ferrite beads L1-L2, and crystal oscillator X1. The pin connections of the microcontroller are as follows: Pin PE5 is connected to the negative terminal of LED D1, and the positive terminal of LED D1 is connected to resistor R1, which is connected to the power supply. Pin PEN is connected to resistor R2, and resistor R2 is connected to the power supply. Pin XTAL1 is connected to capacitors C1 and C2 in sequence and then grounded; pin XTAL1 is connected to the crystal X with resistors R3 and R4 in parallel; crystal X1 is connected to ferrite bead L1 and capacitor C3; ferrite bead L1 is connected to the power supply; capacitor C3 is connected to capacitor C4 and then grounded. Pin VCC is connected to capacitors C5 and C6 in sequence and then grounded; pin VCC is connected to capacitors C7 and C8 in sequence and then grounded. The AVCC pin is connected to capacitors C9 and C10 in sequence and then grounded. The AVCC pin is connected to ferrite bead L2 and then to the power supply. The AREF pin is connected to capacitors C11 and C12 in sequence and then grounded.

3. The wavelength-variable light source module based on PWM temperature control according to claim 2, characterized in that, The active low-pass filter includes a PWM coarse-tuning circuit and a PWM fine-tuning circuit; The PWM coarse adjustment circuit includes comparator A1, resistors R5 to R6, and capacitors C13 to C14. The non-inverting input of comparator A1 is connected to resistor R5 and capacitor C13 respectively. Capacitor C13 is grounded. The output of comparator A1 is connected to resistor R6. Resistor R6 is connected to capacitor C14. Both capacitors C13 and C14 are grounded. The inverting input of comparator A1 is connected to the output of comparator A1. The PWM fine-tuning circuit includes comparator A2, resistors R7 to R8, and capacitors C15 to C16. The non-inverting input of comparator A2 is connected to resistor R7 and capacitor C15, respectively. Capacitor C15 is grounded. The output of comparator A2 is connected to resistor R8. Resistor R8 is connected to capacitor C16. Both capacitors C15 and C16 are grounded. The inverting input of comparator A2 is connected to the output of comparator A2.

4. The wavelength-variable light source module based on PWM temperature control according to claim 3, characterized in that, The H-bridge gating circuit includes transistors Q1 to Q4 and resistors R9 to R12; Resistors R9 to R12 are connected to the bases of transistors Q1 to Q4 respectively. The collectors of transistors Q1 and Q3 are connected to the power supply. The emitters of transistors Q2 and Q4 are grounded. The emitter of transistor Q1 is connected to the collector of transistor Q2, and the emitter of transistor Q3 is connected to the collector of transistor Q4.

5. The wavelength-variable light source module based on PWM temperature control according to claim 1, characterized in that, The temperature control constant current circuit includes a first temperature control constant current circuit and a second temperature control constant current circuit. The first temperature control constant current circuit includes resistors R13 to R17, capacitors C17 to C18, comparator A3, and transistor Q5. Resistors R13 and capacitor C17 are both connected to the non-inverting input of comparator A3, capacitor C17 is grounded, resistor R14 is connected between the output of comparator A3 and the base of transistor Q5, the inverting input of comparator A3 is connected to resistors R15 and R16 in sequence, the emitter of transistor Q5 and one end of resistor R17 are both connected between resistors R15 and R16, the other end of resistor R17 is grounded, and capacitor C18 is connected between the output of comparator A3 and the inverting input of comparator A3.

6. The wavelength-variable light source module based on PWM temperature control according to claim 5, characterized in that, The second temperature control constant current circuit includes resistors R18-R22, capacitors C19-C20, comparator A4, and transistor Q6. Resistor R18 and capacitor C19 are both connected to the non-inverting input of comparator A4, capacitor C19 is grounded, and resistor R19 is connected between the output of comparator A4 and the base of transistor Q6. The inverting input of comparator A4 is connected to resistors R20 and R21 in sequence. The emitter of transistor Q6 and one end of resistor R22 are both connected between resistors R20 and R21, and the other end of resistor R22 is grounded. Capacitor C20 is connected between the output of comparator A4 and the inverting input of comparator A4. The collector of transistor Q5 is connected to the collector of transistor Q6.

7. The wavelength-variable light source module based on PWM temperature control according to claim 1, characterized in that, The output optical power acquisition circuit includes an operational amplifier A5 and resistors R23 to R25. The non-inverting input terminal of the operational amplifier A5 is grounded, and the output terminal of the operational amplifier A5 is connected to resistors R23, R24 and R25 respectively. Resistor R23 is connected to the inverting input terminal of the operational amplifier A5, and resistor R25 is grounded.

8. The wavelength-variable light source module based on PWM temperature control according to claim 1, characterized in that, The RS422 communication circuit includes a transmitting communication circuit and a receiving communication circuit; The transmitting communication circuit includes a driver, resistors R26 to R30, and capacitors C21 to C22. The driver is an AM26LS31CDR, and its pin connections are as follows: Pin EN is not connected to resistor R26; resistor R26 is grounded. Pin EN is connected to resistor R27, and resistor R27 is connected to the power supply. Pin INA is connected to TXD; Pins INB, INC, and IND are all connected to resistor R28, which is grounded. The VCC pin is connected to capacitors C22 and C21 in sequence, and capacitor C21 is grounded. Pin OUTA is connected to resistor R29; Pin OUTA is not connected to resistor R30.

9. The wavelength-variable light source module based on PWM temperature control according to claim 8, characterized in that, The receiving communication circuit includes a receiver, resistors R31 to R38, capacitors C23 to C24, and diode D2. The receiver is an AM26LS3CDR, and its pin connections are as follows: Pin EN is not connected to resistor R31, and resistor R31 is grounded; Pin EN is connected to resistor R32, and resistor R32 is connected to the power supply. Pin INA+ is connected to resistors R33, R35 and R34 in sequence, and resistor R34 is connected to pin INA-; the positive terminal of diode D2 is connected to the power supply, the negative terminal of diode D2 is connected to resistor R36, resistor R36 is connected between resistors R35 and R33, one end of resistor R37 is connected between resistors R35 and R34, and the other end is grounded. Pin VDD is connected to capacitors C24 and C23 in sequence and then grounded; Connect pin OUTA to resistor R38.

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