Double-closed-loop control circuit of uncooled electro-absorption modulated laser and implementation method of double-closed-loop control circuit

Abstract

The invention belongs to the technical field of laser control, and relates to a double-closed-loop control circuit of an uncooled electro-absorption modulated laser and an implementation method. According to the double-closed-loop control circuit, a backlight current detection diode is used for monitoring the backlight power of a DFB laser of an electro-absorption modulator, and a sampling resistor and a differential amplifier are used for collecting backlight current and modulation current of an EAM modulator; the closed-loop control of the bias current of the DFB laser and the closed-loop control of the bias current of the EAM modulator are realized by using the circuit architecture of the comparator and the fitting device of the main control unit. According to the invention, the comparator triggers the DAC setting by using the main control unit, and the working state of the target system is predicted through the linear fitting unit. The invention solves the problem that the light emitting power of the DFB laser and the bias state of the EAM modulator of the electro-absorption modulated laser deviate along with the change of the environment temperature and the increase of the use time, and can be realized on a high-speed multi-channel optical module.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser control, and in particular relates to a double closed-loop control circuit and an implementation method of an uncooled electro-absorption modulated laser. Background Art

[0002] Electro-absorption modulated laser (EML laser) is an integrated device composed of an electro-absorption modulator (EAM modulator) and a distributed feedback laser (DFB laser). It has the advantages of low driving voltage, low power consumption, high modulation bandwidth, small chirp and dispersion, and small chip size. It is widely used in high-speed and long-distance signal transmission.

[0003] Due to the complex structure and high integration of EML lasers, any drift in the working state of the DFB laser and the EAM modulator will cause the performance of the EML laser to deteriorate. Therefore, the conventional solution places the EML laser on a thermoelectric cooler (TEC), and the microcontroller unit (MCU) adjusts the magnitude and direction of the current flowing through the TEC according to the real-time collected laser temperature to achieve a stable laser operating temperature and thus a stable working state. The conventional solution requires the use of thermoelectric coolers, thermistors, and corresponding hardware control circuits to control the laser temperature. There are many components, and the algorithms and processes are complex. The industry has proposed the need to apply EML lasers to non-refrigerated environments.

[0004] The microcontroller unit uses an open-loop temperature lookup table. Each temperature point in the lookup table contains the bias current of the electro-absorption modulated laser DFB and the bias voltage of the EAM modulator. The MCU collects the working environment temperature of the electro-absorption modulated laser and sets the corresponding bias voltage and current through the lookup table.

[0005] EML lasers work in an uncooled environment. The operating temperature of the laser, the bias current and voltage of the DFB and EAM change with the ambient temperature. Compared with the cooling solution, a more severe working environment will accelerate the aging of the device. The fully open-loop control circuit of the existing technology cannot compensate for aging conditions such as the decrease in the slope efficiency of the DFB laser and the change in the bias point of the EAM modulator, causing the device performance to deviate from the initial value, which may seriously lead to system failure. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a dual closed-loop control circuit and an implementation method for an uncooled electro-absorption modulated laser.

[0007] In a first aspect, the present invention provides a dual closed-loop control circuit for an uncooled electro-absorption modulated laser, comprising an electro-absorption modulated laser, a backlight current detection diode, a constant current source, a first bias voltage source, a second bias voltage source, a BIASTEE bias network, a first current detection circuit, a second current detection circuit and a main control unit;

[0008] The first current detection circuit includes a first current sampling resistor and a first differential amplifier; the second current detection circuit includes a second current sampling resistor and a second differential amplifier;

[0009] The electro-absorption modulated laser is composed of a DFB laser and an EAM modulator; the backlight current detection diode is arranged in the back-light emitting direction close to the DFB laser;

[0010] The positive electrode of the EAM modulator is electrically connected to the second end of the first current sampling resistor and the second input end of the first differential amplifier through the BIAS TEE bias network; the first bias voltage source is electrically connected to the first end of the second current sampling resistor and the first input end of the first differential amplifier; the output end of the first differential amplifier is electrically connected to the second input end of the main control unit;

[0011] The positive electrode of the constant current source is electrically connected to the positive electrode of the DFB laser; the negative electrode of the constant current source is electrically connected to the output end of the second bias voltage source, the first end of the second current sampling resistor, and the first input end of the second differential amplifier; the second end of the second current sampling resistor is electrically connected to the second input end of the second differential amplifier and the negative electrode of the backlight current detection diode; the output end of the second differential amplifier is electrically connected to the first input end of the main control unit; the positive electrode of the backlight current detection diode is electrically connected to the negative electrode of the DFB laser and the negative electrode of the EAM modulator; the main control unit is electrically connected to the control input end of the constant current source;

[0012] The output terminal of the main control unit is electrically connected to the control input terminal of the constant current source; the main control unit is electrically connected to the control input terminal of the first bias voltage source;

[0013] The main control unit calculates the modulation current of the EAM modulator according to the first voltage signal collected by the first differential amplifier and the first current sampling resistor, and the main control unit adjusts the output voltage of the first bias voltage source to adjust the bias state of the EAM modulator;

[0014] The main control unit calculates the backlight current according to the second voltage signal collected by the second differential amplifier and the second current sampling resistor to determine the light output power of the DFB laser, and adjusts the light output power of the DFB laser by adjusting the output current of the constant current source.

[0015] In a second aspect, the present invention provides a method for implementing a dual closed-loop control circuit based on an uncooled electro-absorption modulated laser, comprising:

[0016] Setting several operating temperature points of the electro-absorption modulated laser;

[0017] The bias current of the DFB laser and the bias voltage of the EAM modulator are adjusted at the first temperature point. After the electro-absorption modulator reaches the bias operating point, the main control unit collects the first voltage signal and the second voltage signal and stores them in a non-volatile memory inside the main control unit.

[0018] After the first temperature point is debugged, the main control unit sends an enable signal to the first comparator; the main control unit continuously collects the second voltage signal in each main cycle and compares it with the stored reference voltage. If the first comparator outputs a high level, the corresponding light output power of the DFB laser is greater than a preset value, and the main control unit is instructed to control the output of the constant current source to decrease. Conversely, if the first comparator outputs a low level, the main control unit controls the output of the constant current source to increase, so that the light output power of the DFB laser increases, thereby realizing closed-loop control of the bias current of the DFB laser.

[0019] At the second temperature point and the third temperature point, the bias current of the DFB laser is controlled by a closed loop so that the optical power of the DFB laser remains unchanged; after the first bias voltage reaches the set value, a first voltage signal reflecting the magnitude of the modulation current and a constant voltage source voltage are obtained;

[0020] Substitute the three temperature points and the first voltage signal, the second voltage signal and the constant voltage source voltage reflecting the modulation current of the EAM modulator into the linear fitting unit respectively; within the temperature range defined by the first voltage signal, the second voltage signal and the constant voltage source voltage, any temperature is input, and the linear fitting unit calculates the required modulation current of the EAM modulator at the temperature through a linear fitting algorithm;

[0021] After the three temperature points corresponding to the first voltage signal, the second voltage signal and the constant voltage source voltage are debugged and written into the lookup table required by the linear fitting unit, the main control unit sends an enable signal to the second comparator. The main control unit continuously inputs the temperature value and the first voltage signal in each main cycle and compares them with the output of the linear fitting unit at the corresponding input temperature value. If the second comparator outputs a high level, the bias point of the EAM modulator is greater than the predicted value, and the main control unit controls the first bias voltage source to reduce the first bias voltage. Conversely, if the second comparator outputs a low level, the main control unit controls the first bias voltage source to increase the first bias voltage, thereby realizing closed-loop control of the bias current of the EAM modulator.

[0022] Based on the above technical solution, the present invention can also be improved as follows.

[0023] Furthermore, the main control unit includes a first comparison unit, a second comparison unit, a storage unit and a linear fitting unit; the storage unit is used to store a reference voltage; the linear fitting unit performs linear fitting according to the input temperature and voltage to output the voltage at the corresponding temperature; the first comparison unit and the second comparison unit control the output voltage of the main control unit by outputting high and low levels;

[0024] The first input terminal of the first comparison unit is electrically connected to the second differential amplifier; the second input terminal of the first comparison unit is electrically connected to the storage unit; the output terminal of the first comparison unit is electrically connected to the control input terminal of the constant current source;

[0025] The first input terminal of the second comparison unit is electrically connected to the output terminal of the first differential amplifier; the second input terminal of the second comparison unit is electrically connected to the output terminal of the linear fitting unit; the output terminal of the second comparison unit is electrically connected to the control input terminal of the first bias voltage source.

[0026] The beneficial effects of the present invention are:

[0027] (1) The present invention uses a backlight current detection diode to monitor the backlight power of the DFB laser of the electro-absorption modulator, uses a sampling resistor plus a differential amplifier to collect the backlight current and the modulation current of the EAM modulator, and uses the circuit architecture of the comparator and the fitter of the main control unit to realize the closed-loop control of the bias current of the DFB laser and the closed-loop control of the bias current of the EAM modulator. The present invention predicts the working state of the target system through a linear fitting unit. The present invention solves the problem that the light output power of the DFB laser of the electro-absorption modulated laser and the bias state of the EAM modulator are offset with the change of ambient temperature and the increase of the use time, and can be implemented on a high-speed multi-channel optical module;

[0028] (2) The present invention locks the backlight current of the DFB laser and the modulation current of the EAM modulator of the electro-absorption modulated laser to compensate for the problems of the decrease in the luminous slope efficiency of the DFB laser or the change in the modulation slope or the drift of the modulation point of the EAM modulator in the long-term use of the device in an uncooled environment. This enables the electro-absorption modulated laser to maintain long-term stable and reliable performance even when working in an uncooled environment, thereby improving the competitiveness of the uncooled EML laser and meeting the industry's demand for applying the EML laser to an uncooled environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A circuit diagram of a dual closed-loop control circuit of an uncooled electro-absorption modulated laser provided in Example 1 of the present invention;

[0030] Figure 2 This is a circuit architecture schematic diagram of a dual closed-loop control circuit for an uncooled electro-absorption modulated laser provided in Example 1 of the present invention.

[0031] Icon: U0-electroabsorption modulated laser; Q1-backlight current detection diode; R1-first current sampling resistor; R2-second current sampling resistor; U1-first differential amplifier; U2-second differential amplifier; U3-constant current source; U4-storage unit; VEA-first bias voltage source; VCC-second bias voltage source VCC; L-BIAS TEE bias network; MCU-main control unit; S1-first comparison unit; S2-second comparison unit; S3-linear fitting unit. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0033] Example 1

[0034] As an example, Figure 1 As shown, in order to solve the above technical problems, this embodiment provides a dual closed-loop control circuit of an uncooled electro-absorption modulated laser, including an electro-absorption modulated laser U0, a backlight current detection diode Q1, a constant current source U3, a first bias voltage source VEA, a second bias voltage source VCC, a BIAS TEE bias network L, a first current detection circuit, a second current detection circuit and a main control unit MCU;

[0035] The first current detection circuit includes a first current sampling resistor R1 and a first differential amplifier U1; the second current detection circuit includes a second current sampling resistor R2 and a second differential amplifier U2;

[0036] The electro-absorption modulated laser U0 is composed of a DFB laser and an EAM modulator; the backlight current detection diode Q1 is arranged in the back-light emitting direction close to the DFB laser;

[0037] The positive electrode of the EAM modulator is electrically connected to the second end of the first current sampling resistor R1 and the second input end of the second differential amplifier U2 through the BIAS TEE bias network L; the first bias voltage source VEA is electrically connected to the first end of the first current sampling resistor R1 and the first input end of the first differential amplifier U1; the output end of the first differential amplifier U1 is electrically connected to the second input end of the main control unit MCU;

[0038] The positive electrode of the constant current source U3 is electrically connected to the positive electrode of the DFB laser; the negative electrode of the constant current source U3 is electrically connected to the output end of the second bias voltage source VCC, the first end of the second current sampling resistor R2, and the first input end of the second differential amplifier U2; the second end of the second current sampling resistor R2 is electrically connected to the second input end of the second differential amplifier U2 and the negative electrode of the backlight current detection diode Q1; the output end of the second differential amplifier U2 is electrically connected to the first input end of the main control unit MCU; the positive electrode of the backlight current detection diode Q1 is electrically connected to the negative electrode of the DFB laser and the negative electrode of the EAM modulator; the main control unit MCU is electrically connected to the control input end of the constant current source U3;

[0039] The output terminal of the main control unit MCU is electrically connected to the control input terminal of the constant current source U3; the main control unit MCU is electrically connected to the control input terminal of the first bias voltage source VEA;

[0040] The main control unit MCU calculates the modulation current of the EAM modulator according to the first voltage signal collected by the first differential amplifier U1 and the first current sampling resistor R1, and the main control unit MCU adjusts the output voltage of the first bias voltage source VEA to adjust the bias state of the EAM modulator;

[0041] The main control unit MCU calculates the backlight current according to the second voltage signal collected by the second differential amplifier U2 and the second current sampling resistor R2 to determine the optical power of the DFB laser, and adjusts the optical power of the DFB laser by adjusting the output current of the constant current source U3.

[0042] In actual application, VCC provides bias voltage for the backlight current detection diode Q1 and the constant current source U3. The constant current source U3 provides a stable bias current for the DFB laser under the control of the MCU. The first bias voltage source VEA provides a negative bias voltage for the EAM modulator. L is a simplified BIAS TEE bias network. The first differential amplifier U1 and the second differential amplifier U2 respectively form a current detection circuit with the first current sampling resistor R1 and the second current sampling resistor R2, converting the current signal flowing through into a voltage signal, amplifying it and inputting it into the analog to digital converter (ADC) acquisition port of the main control unit MCU. The main control unit MCU collects the voltage signals output by the first differential amplifier U1 and the second differential amplifier U2, and sets the output current of the constant current source and the bias voltage of the constant voltage source through the digital to analog converter (DAC).

[0043] The DFB laser and the EAM modulator of the electro-absorption modulator U0 are both temperature-sensitive devices, so that the optical power of the DFB laser and the bias operating point of the EAM modulator change with temperature.

[0044] It is known that the DFB laser is a side-emitting device. There is a backlight on the back of the light-emitting surface that is proportional to the forward light power, which is used to indicate the current forward light power of the DFB laser. This light power is called the backlight power. The backlight current detection diode Q1 is placed close to the backlight direction of the DFB laser. The backlight power is converted into the backlight current Impd by the backlight current detection diode Q1, and the second current sampling resistor R2 and the second differential amplifier U2 are converted and amplified into the second voltage signal Vmpd suitable for collection by the ADC of the main control unit MCU. The main control unit MCU monitors the voltage to obtain the backlight current Impd to determine the light output power of the DFB laser and adjusts the light output power of the DFB laser by adjusting the output current of the constant current source U3.

[0045] The EAM modulator is a light intensity modulation device made by using the semiconductor exciton absorption effect. When it is in reverse bias, that is, the anode voltage is lower than the cathode voltage, a modulation current Iea associated with the EAM modulator operating temperature, bias voltage and input optical power from the DFB laser will be generated. In refrigeration applications, the optical power of the DFB laser and the operating temperature of the EAM modulator remain unchanged, so the modulation current of the EAM modulator is only related to the bias voltage of the EAM modulator. In non-refrigeration applications, the first current sampling resistor R1 and the first differential amplifier U1 are designed. The first current sampling resistor R1 and the first differential amplifier U1 convert and amplify the modulation current into a voltage Viea1 suitable for ADC collection of the main control unit MCU, and calculate the modulation current of the EAM modulator in the corresponding state. The main control unit MCU uses DAC to adjust the first bias voltage VEA to adjust the bias state of the EAM modulator, and a series of modulation currents are obtained accordingly. The modulation current reflects the bias state of the EAM modulator at a specific operating temperature and DFB light emitting power.

[0046] Optional, as attached Figure 2 As shown, the main control unit MCU includes a first comparison unit S1, a second comparison unit S2, a storage unit U4 and a linear fitting unit S3; the storage unit U4 is used to store a reference voltage; the linear fitting unit S3 performs linear fitting according to the input temperature and voltage and outputs a voltage at a corresponding temperature; the first comparison unit S1 and the second comparison unit S2 control the output voltage of the main control unit MCU by outputting high and low levels;

[0047] The first input terminal of the first comparison unit S1 is electrically connected to the second differential amplifier U2; the second input terminal of the first comparison unit S1 is electrically connected to the storage unit U4; the output terminal of the first comparison unit S1 is electrically connected to the control input terminal of the constant current source U3;

[0048] The first input terminal of the second comparison unit S2 is electrically connected to the output terminal of the first differential amplifier U1; the second input terminal of the second comparison unit S2 is electrically connected to the output terminal of the linear fitting unit S3; the output terminal of the second comparison unit S2 is electrically connected to the control input terminal of the first bias voltage source U1.

[0049] In actual application, according to the working environment requirements of the electro-absorption modulated laser, three typical working temperature points are selected. The closed-loop control process of the bias current of the DFB laser and the closed-loop control process of the bias current of the EAM modulator are as follows:

[0050] (1) The closed-loop control process of the bias current of the DFB laser is as follows: the bias current of the DFB laser and the bias voltage of the EAM modulator are adjusted at the first temperature point. After the optimal linearity working state of the electro-absorption modulator is reached, the main control unit MCU collects the first voltage signal Viea1 and the second reference voltage Vmpd1 used by the storage unit U4 and stores them in the non-volatile memory inside the main control unit MCU.

[0051] After the first temperature point is debugged, the main control unit MCU sends an enable signal to the first comparison unit S1. The main control unit MCU continuously collects the second voltage signal Vmpd in each main cycle and compares it with the stored reference voltage Vmpd1. The first comparison unit S1 outputs a high level corresponding to the light output power of the DFB laser being greater than the preset value, instructing the main control unit MCU to control the DAC to reduce the output of the constant current source U3. Conversely, the low level output instructs the main control unit MCU to control the DAC to increase the output of the constant current source U3 to increase the light output power of the DFB laser, thereby realizing closed-loop control of the bias current of the DFB laser.

[0052] (2) The closed-loop control process of the bias current of the EAM modulator is as follows: at the second and third temperature points, the bias current of the DFB laser at different temperature points is controlled by closed loop so that the output light power remains unchanged, and the modulation current of the EAM modulator is related to the bias voltage and the working environment temperature. At the second and third temperature points, the first bias voltage source VEA is adjusted to bias the EAM modulator to the optimal linearity state, and the first voltage signal Viea2 reflecting the magnitude of the modulation current and the constant current source signal Viea3 are obtained.

[0053] The three working environment temperature points and the three voltage signals Viea1, Viea2 and Viea3 reflecting the modulation current of the EAM modulator are correspondingly brought into the linear fitting unit S3. Within the temperature range defined by the three temperature points, any temperature Vtemp is input, and S3 calculates the modulation current required for the EAM modulator to be biased in the optimal linearity state at this temperature through the linear fitting algorithm.

[0054] After the three temperature points are debugged and written into the lookup table required by the linear fitting unit, the main control unit MCU sends an enable signal to the second comparison unit S2. The main control unit MCU continuously collects the input temperature Vtemp and the first voltage signal Viea in each main cycle, and compares them with the voltage signal output by the linear fitting unit S3 at the corresponding input temperature value. If the second comparison unit S2 outputs a high level corresponding to the EAM modulator bias point being greater than the predicted value, the main control unit MCU controls the DAC to reduce the absolute value of the bias voltage VEA. Conversely, if the second comparison unit S2 outputs a low level, the main control unit MCU controls the DAC to increase the bias voltage of the EAM modulator, thereby realizing closed-loop control of the bias current of the EAM modulator.

[0055] The present invention can target different EAM modulators and, in actual applications, can support complex fitting algorithms such as piecewise linear fitting algorithms with more than three points or quadratic fitting to predict the bias current corresponding to the bias of the intermediate temperature EAM modulator at the expected operating point.

[0056] The present invention proposes a dual closed-loop control circuit for the stable operation of an uncooled electro-absorption modulated laser. The circuit collects the backlight current of a DFB laser and the modulation current of an EAM modulator of the EML laser in real time and realizes the stable operation of the EML laser over temperature and time through a dual closed-loop control method.

[0057] The present invention locks the backlight current of the DFB laser and the modulation current of the EAM modulator of the electro-absorption modulated laser, thereby compensating for the problems of the decrease in the luminous slope efficiency of the DFB laser or the change in the modulation slope or the drift of the modulation point of the EAM modulator in the long-term use of the device in a non-refrigerated environment. Therefore, the electro-absorption modulated laser can maintain long-term stable and reliable performance even when working in a non-refrigerated environment, thereby improving the competitiveness of the non-refrigerated EML laser and meeting the demand of the industry for applying the EML laser to a non-refrigerated environment.

[0058] The present invention uses a backlight current detection diode to monitor the backlight power of a DFB laser of an electro-absorption modulator, uses a sampling resistor plus a differential amplifier to collect backlight current and modulation current of an EAM modulator, and uses a circuit architecture of a comparator and a fitter of a main control unit to implement closed-loop control of bias current of the DFB laser and closed-loop control of bias current of the EAM modulator. The present invention uses a main control unit to implement comparator trigger DAC settings, and predicts the working state of a target system through a linear fitting unit. The present invention solves the problem that the output power of a DFB laser of an electro-absorption modulated laser and the bias state of an EAM modulator are offset as the ambient temperature changes and the use time increases, and can be implemented on a high-speed multi-channel optical module.

[0059] Example 2

[0060] Based on the same principle as the dual closed-loop control circuit shown in Embodiment 1 of the present invention, the embodiment of the present invention further provides a method for implementing a dual closed-loop control circuit based on an uncooled electro-absorption modulated laser, including:

[0061] Setting several operating temperature points of the electro-absorption modulated laser;

[0062] The bias current of the DFB laser and the bias voltage of the EAM modulator are adjusted at the first temperature point. After the electro-absorption modulator reaches the bias operating point, the main control unit collects the first voltage signal and the second voltage signal and stores them in a non-volatile memory inside the main control unit.

[0063] After the first temperature point is debugged, the main control unit sends an enable signal to the first comparator; the main control unit continuously collects the second voltage signal in each main cycle and compares it with the stored reference voltage. If the first comparator outputs a high level, the corresponding light output power of the DFB laser is greater than a preset value, and the main control unit is instructed to control the output of the constant current source to decrease. Conversely, if the first comparator outputs a low level, the main control unit controls the output of the constant current source to increase, so that the light output power of the DFB laser increases, thereby realizing closed-loop control of the bias current of the DFB laser.

[0064] At the second temperature point and the third temperature point, the bias current of the DFB laser is controlled by a closed loop so that the optical power of the DFB laser remains unchanged; after the first bias voltage reaches the set value, a second voltage signal reflecting the magnitude of the modulation current and a constant current source voltage are obtained;

[0065] Substitute the three temperature points and the first voltage signal, the second voltage signal and the constant voltage source voltage reflecting the modulation current of the EAM modulator into the linear fitting unit respectively; within the temperature range defined by the first voltage signal, the second voltage signal and the constant voltage source voltage, any temperature is input, and the linear fitting unit calculates the required modulation current of the EAM modulator at the temperature through a linear fitting algorithm;

[0066] After the three temperature points corresponding to the first voltage signal, the second voltage signal and the constant voltage source voltage are debugged and written into the lookup table required by the linear fitting unit, the main control unit sends an enable signal to the second comparator. The main control unit continuously inputs the temperature value and the first voltage signal in each main cycle, and compares them with the output of the linear fitting unit at the corresponding input temperature value. If the second comparator outputs a high level, the bias point of the EAM modulator is greater than the predicted value, and the main control unit controls the first bias voltage source to reduce the first bias voltage. Conversely, if the second comparator outputs a low level, the main control unit controls the first bias voltage source to increase the first bias voltage, thereby realizing closed-loop control of the bias current of the EAM modulator.

[0067] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dual closed-loop control circuit for an uncooled electro-absorption modulated laser, characterized in that: It includes an electro-absorption modulated laser, a backlight current detection diode, a constant current source, a first bias voltage source, a second bias voltage source, a BIAS TEE bias network, a first current detection circuit, a second current detection circuit and a main control unit; The first current detection circuit includes a first current sampling resistor and a first differential amplifier; the second current detection circuit includes a second current sampling resistor and a second differential amplifier; The electro-absorption modulated laser is composed of a DFB laser and an EAM modulator; the backlight current detection diode is arranged in the back-light emitting direction close to the DFB laser; The positive electrode of the EAM modulator is electrically connected to the second end of the first current sampling resistor and the second input end of the first differential amplifier through the BIAS TEE bias network; the first bias voltage source is electrically connected to the first end of the second current sampling resistor and the first input end of the first differential amplifier; the output end of the first differential amplifier is electrically connected to the second input end of the main control unit; The positive electrode of the constant current source is electrically connected to the positive electrode of the DFB laser; the negative electrode of the constant current source is electrically connected to the output end of the second bias voltage source, the first end of the second current sampling resistor, and the first input end of the second differential amplifier; the second end of the second current sampling resistor is electrically connected to the second input end of the second differential amplifier and the negative electrode of the backlight current detection diode; the output end of the second differential amplifier is electrically connected to the first input end of the main control unit; the positive electrode of the backlight current detection diode is electrically connected to the negative electrode of the DFB laser and the negative electrode of the EAM modulator; the main control unit is electrically connected to the control input end of the constant current source; The output terminal of the main control unit is electrically connected to the control input terminal of the constant current source; the main control unit is electrically connected to the control input terminal of the first bias voltage source; The main control unit calculates the modulation current of the EAM modulator according to the first voltage signal collected by the first differential amplifier and the first current sampling resistor, and the main control unit adjusts the output voltage of the first bias voltage source to adjust the bias state of the EAM modulator; The main control unit calculates the backlight current according to the second voltage signal collected by the second differential amplifier and the second current sampling resistor to determine the light output power of the DFB laser, and adjusts the light output power of the DFB laser by adjusting the output current of the constant current source.

2. The dual closed-loop control circuit of the uncooled electro-absorption modulated laser according to claim 1, characterized in that: The main control unit includes a first comparison unit, a second comparison unit, a storage unit and a linear fitting unit; the storage unit is used to store a reference voltage; the linear fitting unit performs linear fitting according to the input temperature and voltage and outputs the voltage at the corresponding temperature; the first comparison unit and the second comparison unit control the output voltage of the main control unit by outputting high and low levels, thereby controlling the output current of the constant current source and the bias voltage of the first bias voltage source; The first input terminal of the first comparison unit is electrically connected to the second differential amplifier; the second input terminal of the first comparison unit is electrically connected to the storage unit; An output terminal of the first comparison unit is electrically connected to a control input terminal of the constant current source; A first input terminal of the second comparison unit is electrically connected to an output terminal of the first differential amplifier; The second input terminal of the second comparison unit is electrically connected to the output terminal of the linear fitting unit; The output terminal of the second comparison unit is electrically connected to the control input terminal of the first bias voltage source.

3. A method for implementing a dual closed-loop control circuit of an uncooled electro-absorption modulated laser according to claim 2, characterized in that: include: Setting several operating temperature points of the electro-absorption modulated laser; The bias current of the DFB laser and the bias voltage of the EAM modulator are adjusted at the first temperature point. After the electro-absorption modulator reaches the optimal linearity, the main control unit collects the first voltage signal and the second voltage signal and stores them in a non-volatile memory inside the main control unit. After the first temperature point is debugged, the main control unit sends an enable signal to the first comparator; the main control unit continuously collects the second voltage signal in each main cycle and compares it with the stored reference voltage. If the first comparator outputs a high level, the corresponding light output power of the DFB laser is greater than a preset value, and the main control unit is instructed to control the output of the constant current source to decrease. Conversely, if the first comparator outputs a low level, the main control unit controls the output of the constant current source to increase, so that the light output power of the DFB laser increases, thereby realizing closed-loop control of the bias current of the DFB laser. At the second temperature point and the third temperature point, the bias current of the DFB laser is controlled by a closed loop so that the optical power of the DFB laser remains unchanged; after the first bias voltage reaches the set value, a first voltage signal reflecting the magnitude of the modulation current and a constant voltage source voltage are obtained; Substitute the three temperature points and the first voltage signal, the second voltage signal and the constant voltage source voltage reflecting the modulation current of the EAM modulator into the linear fitting unit respectively; within the temperature range defined by the first voltage signal, the second voltage signal and the constant current source voltage, any temperature is input, and the linear fitting unit calculates the required modulation current of the EAM modulator at the temperature through a linear fitting algorithm; After the three temperature points corresponding to the first voltage signal, the second voltage signal and the constant voltage source voltage are debugged and written into the lookup table required by the linear fitting unit, the main control unit sends an enable signal to the second comparator. The main control unit continuously inputs the temperature value and the first voltage signal in each main cycle and compares them with the output of the linear fitting unit at the corresponding input temperature value. If the second comparator outputs a high level, the bias point of the EAM modulator is greater than the predicted value, and the main control unit controls the first bias voltage source to reduce the first bias voltage. Conversely, if the second comparator outputs a low level, the main control unit controls the first bias voltage source to increase the first bias voltage, thereby realizing closed-loop control of the bias current of the EAM modulator.

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