A control circuit for a high power fiber amplifier

Abstract

The utility model discloses a kind of control circuit of high-power optical fiber amplifier, it is related to optical fiber amplifier technical field, high-power optical fiber amplifier includes the first stage gain unit and second stage gain unit sequentially arranged along the transmission direction of light;Control circuit includes the control module, first gain control ring and second gain control ring connected;When starting optical fiber amplifier, control module controls first gain control ring to start first stage gain unit, and the output light power of first stage gain unit is collected, control module controls second gain control ring to start second stage gain unit when the output light power of first stage gain unit is greater than threshold light power;When closing optical fiber amplifier, control module first controls second gain control ring to close second stage gain unit, then controls first gain control ring to close first stage gain unit.The control circuit can improve the security and reliability of the high-power optical fiber amplifier application.

Description

Technical Field

[0001] This utility model relates to the field of fiber optic amplifier technology, and in particular to a control circuit for a high-power fiber optic amplifier. Background Technology

[0002] In order to fully tap the potential of optical communication networks, longer wavelength division multiplexing (WDM) system transmission distances have become the preferred solution and research hotspot in the field of optical fiber communication. However, the output power of traditional EDFAs that support multi-wavelength transmission is usually not large enough, and the nonlinear effects of traditional optical fiber transmission systems are severe, which means they are destined not to carry out long-distance single-span transmission.

[0003] In recent years, hollow-core fiber optic transmission systems have begun to emerge. Because they transmit through air, nonlinear effects during transmission are significantly reduced, making the demand for high-power multimode amplifiers extremely urgent. Amplifiers supporting hollow-core fiber transmission have high output power (above 33 dBm), and because of air transmission, nonlinear effects are minimal, effectively avoiding performance degradation caused by nonlinear effects such as four-wave mixing, Raman shift, and Brillouin scattering. This makes transmissions with a single span greater than 300 kilometers a reality. Traditional fiber optic amplifiers have reached their output power saturation point and cannot meet the requirements of hollow-core fiber optic transmission systems. Furthermore, traditional high-power amplifiers generate huge reverse ASE (Amplified Spontaneous Emission) signals when there is no input optical signal, easily burning out multimode pump and other optical path components. Utility Model Content

[0004] In response to the aforementioned problems and technical requirements, the applicant has proposed a control circuit for a high-power fiber optic amplifier.

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

[0006] A control circuit for a high-power fiber optic amplifier, the high-power fiber optic amplifier comprising a first-stage gain unit and a second-stage gain unit arranged sequentially along the direction of light transmission;

[0007] The control circuit of the high-power fiber amplifier includes a control module, a first gain control loop, and a second gain control loop connected to each other. The first gain control loop is connected to a first-stage gain unit, and the second gain control loop is connected to a second-stage gain unit.

[0008] When the fiber amplifier is turned on, the control module controls the first gain control loop to turn on the first-stage gain unit. The first gain control loop is used to collect the output optical power of the first-stage gain unit and transmit it to the control module. When the output optical power of the first-stage gain unit is greater than the threshold optical power, the control module controls the second gain control loop to turn on the second-stage gain unit.

[0009] When shutting down the fiber amplifier, the control module first controls the second gain control loop to shut down the second-stage gain unit, and then controls the first gain control loop to shut down the first-stage gain unit.

[0010] The further technical solution is that the first-stage gain unit includes a first photodetector, a fourth photodetector, a first pump source, and a second pump source;

[0011] The control circuit includes a first linear amplifier module, which includes an MCU, a DAC, and an ADC; the first gain control loop includes a first PID control module, a first current-to-voltage conversion module, a second current-to-voltage conversion module, and a second linear amplifier module.

[0012] The input terminal of the first current-to-voltage conversion module is connected to the negative terminal of the first photodetector, the input terminal of the first linear amplification module is connected to the positive terminal of the first photodetector, the output terminal of the first current-to-voltage conversion module is connected to the ADC, and the output terminal of the first linear amplification module is connected to the first input terminal of the first PID control module.

[0013] A further technical solution is that the input terminal of the second linear amplification module is connected to the positive electrode of the fourth photodetector, and the output terminal of the second linear amplification module is connected to the second input terminal of the first PID control module.

[0014] The input terminal of the second current-to-voltage conversion module is connected to the negative terminal of the fourth photodetector, and the output terminal of the second current-to-voltage conversion module is connected to the ADC.

[0015] The first output terminal of the first PID control module is connected to the first pump source, and the second output terminal of the first PID control module is connected to the second pump source.

[0016] The further technical solution is that the second-stage gain unit includes a fifth photodetector, a first multimode pump source, and a second multimode pump source;

[0017] The second gain control loop includes a second PID control module, a third current-to-voltage conversion module, and a third linear amplification module;

[0018] The input terminal of the third current-to-voltage conversion module is connected to the negative terminal of the fifth photodetector, and the input terminal of the third linear amplification module is connected to the positive terminal of the fifth photodetector.

[0019] The output terminal of the third current-to-voltage conversion module is connected to the ADC, the output terminal of the third linear amplifier module is connected to the first input terminal of the second PID control module, and the output terminal of the first linear amplifier module is also connected to the second input terminal of the second PID control module.

[0020] The first output terminal of the second PID control module is connected to the first multimode pump source, and the second output terminal of the second PID control module is connected to the second multimode pump source.

[0021] A further technical solution is that the MCU is connected to the first PID control module and the second PID control module respectively, the input terminal of the DAC is connected to the MCU, and the output terminal of the DAC is connected to the first PID control module and the second PID control module respectively.

[0022] A further technical solution includes a connector for connecting to the MCU, wherein the connector receives a switching signal for controlling the switching state of the high-power fiber optic amplifier and transmits it to the MCU;

[0023] The MCU is used to turn on the high-power fiber amplifier when the switch signal is valid;

[0024] The MCU obtains the input optical power of the high-power fiber amplifier through the first current-to-voltage conversion module and the ADC;

[0025] The MCU is used to shut down the high-power fiber amplifier when the input optical power is below the shutdown threshold and / or the switch signal is invalid.

[0026] Its further technical solution also includes a power management module and a power failure detection module;

[0027] The power supply is connected to the power management module via a connector. The power management module is used to supply power to the control module, the power failure detection module, the first gain control loop, the second gain control loop, the first-stage gain unit, and the second-stage gain unit.

[0028] The power management module includes a first DC-DC conversion circuit, which is used to convert the power supply voltage into the operating voltage required by the first multimode pump source and the second multimode pump source, and to supply power to the first multimode pump source and the second multimode pump source.

[0029] The power failure detection module is used to detect power failure of the power supply. When the power failure detection module detects that the power supply is cut off, it controls the first DC-DC conversion circuit to stop supplying power to the first multimode pump source and the second multimode pump source, so as to shut down the second-stage gain unit.

[0030] A further technical solution is that the power failure detection module includes a voltage comparator U1, a capacitor C1, resistors R1, R2, R3, and R4, wherein...

[0031] The non-inverting input terminal of the voltage comparator U1 is connected to one end of resistor R1 and one end of resistor R2. The other end of resistor R1 is connected to the power supply, and the other end of resistor R2 is connected to analog ground.

[0032] The inverting input terminal of the voltage comparator U1 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the reference voltage source, and the output terminal of the voltage comparator U1 is connected to the enable terminal of the first DC-DC conversion circuit through the resistor R4.

[0033] One end of the capacitor C1 is connected to the power supply terminal of the voltage comparator U1, and the other end of the capacitor C1 is connected to the ground terminal of the voltage comparator U1.

[0034] A further technical solution is that the first-stage gain unit further includes an input signal port, a first optical splitter, a first isolator, a first wavelength division multiplexer, a first erbium-doped fiber, a second wavelength division multiplexer, a first IGFF unit, a third wavelength division multiplexer, a second erbium-doped fiber, a second IGFF unit, a second optical splitter, a variable attenuator, a third optical splitter, a fourth wavelength division multiplexer, a third erbium-doped fiber, a second isolator, a fourth optical splitter, a second photodetector, and a third photodetector, wherein...

[0035] The input signal port is connected to the input end of the first beam splitter, the first beam splitter's first beam splitter's first beam splitter's first beam splitter's first beam splitter's first beam splitter's input end is connected to the input end of the first isolator, the second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's third ... second beam splitter's second beam splitter's second beam splitter'

[0036] The output of the first wavelength division multiplexer is connected to the input of the second wavelength division multiplexer through a first section of erbium-doped fiber. The first output of the second wavelength division multiplexer is connected to the first input of the third wavelength division multiplexer. The second output of the second wavelength division multiplexer is connected to the second input of the third wavelength division multiplexer through a first IGFF unit.

[0037] The output of the third wavelength division multiplexer is connected to the input of the second IGFF unit via a second erbium-doped fiber. The output of the second IGFF unit is connected to the input of the second beam splitter. The first beam splitter of the second beam splitter is connected to the input of the variable attenuator. The second beam splitter of the second beam splitter is connected to the second photodetector. The output of the variable attenuator is connected to the input of the third beam splitter. The first beam splitter of the third beam splitter is connected to the first input of the fourth wavelength division multiplexer. The second beam splitter of the third beam splitter is connected to the third photodetector.

[0038] The second input terminal of the fourth wavelength division multiplexer is connected to the second pump source, the output terminal of the fourth wavelength division multiplexer is connected to the input terminal of the second isolator through the third erbium-doped fiber, the output terminal of the second isolator is connected to the input terminal of the fourth beam splitter, and the first beam splitter of the fourth beam splitter is connected to the fourth photodetector.

[0039] The further technical solution is that the second-stage gain unit includes a multimode pump combiner, a first section of erbium-ytterbium co-doped fiber, a third isolator, a fifth beam splitter, an output signal port, a first multimode pump source, a second multimode pump source, and a fifth photodetector;

[0040] The second splitting end of the fourth beam splitter is connected to the first input end of the multimode pump combiner. The first multimode pump source is connected to the second input end of the multimode pump combiner. The second multimode pump source is connected to the third input end of the multimode pump combiner. The output end of the multimode pump combiner is connected to the input end of the third isolator through a first section of erbium-ytterbium co-doped fiber. The output end of the third isolator is connected to the input end of the fifth beam splitter. The first splitting end of the fifth beam splitter is connected to the output signal port. The second splitting end of the fifth beam splitter is connected to the fifth photodetector.

[0041] The beneficial technical effects of this utility model are:

[0042] A control circuit for a high-power fiber optic amplifier is provided, capable of controlling the amplifier to achieve high power output, suitable for use in hollow-core fiber optic transmission systems, and supporting multi-wavelength transmission. Simultaneously, it can control the on / off sequence of the first-stage and second-stage gain units in the fiber optic amplifier, preventing the high-power fiber optic amplifier from generating a large reverse ASE signal that could burn out multimode pump and other optical path components when there is no input optical signal, thus improving the safety and reliability of its application.

[0043] In addition, the control circuit can also detect power failure of the fiber optic amplifier, so that even in the extreme case of sudden power failure, the second-stage gain unit can still be turned off before the first-stage gain unit, ensuring that the entire high-power fiber optic amplifier can operate safely and reliably in all application scenarios, whether the built-in MCU is running normally or in a power failure state. Attached Figure Description

[0044] Figure 1 This is a structural block diagram of one embodiment of the high-power fiber optic amplifier control circuit provided by this utility model.

[0045] Figure 2 This is a schematic diagram of the optical path of one embodiment of the high-power fiber optic amplifier provided by this utility model.

[0046] Figure 3This is a circuit diagram of one embodiment of the power failure detection module provided by this utility model.

[0047] Figure reference numerals: 1-Input signal port, 2-First optical splitter, 3-First isolator, 4-First wavelength division multiplexer, 5-First erbium-doped fiber segment, 6-Second wavelength division multiplexer, 7-First IGFF unit, 8-Third wavelength division multiplexer, 9-Second erbium-doped fiber segment, 10-Second IGFF unit, 11-Second optical splitter, 12-Variable attenuator, 13-Third optical splitter, 14-Fourth wavelength division multiplexer, 15-Third erbium-doped fiber segment, 16-Second isolator 17-Fourth beam splitter, 18-Multimode pump combiner, 19-First erbium-ytterbium co-doped fiber, 20-Third isolator, 21-Fifth beam splitter, 22-Output signal port, 23-First photodetector, 24-First pump source, 25-Second photodetector, 26-Third photodetector, 27-Second pump source, 28-Fourth photodetector, 29-First multimode pump source, 30-Second multimode pump source, 31-Fifth photodetector. Detailed Implementation

[0048] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0049] This utility model provides a control circuit for a high-power fiber optic amplifier, which includes a first-stage gain unit and a second-stage gain unit arranged sequentially along the direction of light transmission.

[0050] The control circuit of the high-power fiber amplifier includes a control module, a first gain control loop (Gain control loop 1), and a second gain control loop (Gain control loop 2) that are adapted to each other. The first gain control loop is connected to the first-stage gain unit, and the second gain control loop is connected to the second-stage gain unit.

[0051] Specifically, in the high-power fiber amplifier, the first-stage gain unit amplifies the input signal light to near the saturation output optical power of conventional erbium fiber; the pump source in the second-stage gain unit can be a multimode pump source with a maximum drive current of 13A and a pump power of 10000mW, amplifying the output optical power of the first-stage gain unit to a high power of over 33dBm to meet the requirements of hollow-core fiber transmission systems. The specific structure of the optical path of the high-power fiber amplifier is described below.

[0052] Because the fiber amplifier provided in this invention has a maximum total output power of over 33dBm, the second-stage gain unit, in the absence of signal light input, will generate a large reverse ASE signal due to the large current driving the multimode pump source. This can cause optical path components such as isolators, GFFs (gain flattening filters), and multimode pump sources to burn out. Therefore, when turning on the fiber amplifier, it is essential to strictly follow the turn-on sequence of first turning on the first-stage gain unit and then the second-stage gain unit.

[0053] When the fiber amplifier is turned on, the control module controls the first gain control loop to activate the first-stage gain unit. The first gain control loop is used to collect the output optical power of the first-stage gain unit and transmit it to the control module. When the output optical power of the first-stage gain unit is greater than the threshold optical power, the control module controls the second gain control loop to activate the second-stage gain unit. At this time, the output optical power of the first-stage gain unit is relatively stable, and no large ASE signal will be generated after the second-stage gain unit is activated. After the second-stage gain unit is activated, the driving current of the multimode pump source in the second-stage gain unit will slowly increase until the output optical power of the second-stage gain unit reaches the second target optical power, ensuring the safe and reliable operation of the high-power fiber amplifier. The control methods of the first-stage gain unit and the second-stage gain unit can be referred to the following description, and the threshold optical power can be set according to the actual situation.

[0054] When shutting down the high-power amplifier, for safety and reliability reasons, and to prevent the second-stage gain unit from generating a large ASE signal due to the lack of signal light input, the shutdown sequence must be reversed from the startup sequence: first shut down the second-stage gain unit, and then shut down the first-stage gain unit.

[0055] Further, please refer to Figure 2 In this embodiment, the first-stage gain unit includes a first photodetector 23 (PD1), a fourth photodetector 28 (PD4), a first pump source 24 (PUMP1), a second pump source 27 (PUMP2), an input signal port 1, a first beam splitter 2, a first isolator 3, a first wavelength division multiplexer 4, a first erbium-doped fiber 5, a second wavelength division multiplexer 6, a first IGFF unit 7, a third wavelength division multiplexer 8, a second erbium-doped fiber 9, a second IGFF unit 10, a second beam splitter 11, a variable attenuator 12, a third beam splitter 13, a fourth wavelength division multiplexer 14, a third erbium-doped fiber 15, a second isolator 16, a fourth beam splitter 17, a second photodetector 25, and a third photodetector 26.

[0056] The input signal port 1 is connected to the input end of the first beam splitter 2. The first beam splitter 2 is connected to the input end of the first isolator 3. The second beam splitter 2 is connected to the first photodetector 23. The output end of the first isolator 3 is connected to the first input end of the first wavelength division multiplexer 4. The first pump source 24 is connected to the second input end of the first wavelength division multiplexer 4. The output end of the first wavelength division multiplexer 4 is connected to the input end of the second wavelength division multiplexer 6 through the first erbium-doped fiber 5. The first output end of the second wavelength division multiplexer 6 is connected to the first input end of the third wavelength division multiplexer 8. The second output end of the second wavelength division multiplexer 6 is connected to the second input end of the third wavelength division multiplexer 8 through the first IGFF unit 7. The output of the third wavelength division multiplexer 8 is connected to the input of the second IGFF unit 10 via the second erbium-doped fiber 9. The output of the second IGFF unit 10 is connected to the input of the second beam splitter 11. The first beam splitter of the second beam splitter 11 is connected to the input of the variable attenuator 12. The second beam splitter of the second beam splitter 11 is connected to the second photodetector 25. The output of the variable attenuator 12 is connected to the input of the third beam splitter 13. The first beam splitter of the third beam splitter 13 is connected to the first input of the fourth wavelength division multiplexer 14. The second beam splitter of the third beam splitter 13 is connected to the third photodetector. The second input of the fourth wavelength division multiplexer 14 is connected to the second pump source 27. The output of the fourth wavelength division multiplexer 14 is connected to the input of the second isolator 16 via the third erbium-doped fiber 15. The output of the second isolator 16 is connected to the input of the fourth beam splitter 17. The first beam splitter of the fourth beam splitter 17 is connected to the fourth photodetector 28.

[0057] The second-stage gain unit includes a multimode pump combiner 18, a first section of erbium-ytterbium co-doped fiber 19, a third isolator 20, a fifth beam splitter 21, an output signal port 22, a first multimode pump source 29 (MP1), a second multimode pump source 30 (MP2), and a fifth photodetector 31 (PD5).

[0058] The second splitting end of the fourth beam splitter 17 is connected to the first input end of the multimode pump combiner 18. The first multimode pump source 29 is connected to the second input end of the multimode pump combiner 18. The second multimode pump source 30 is connected to the third input end of the multimode pump combiner 18. The output end of the multimode pump combiner 18 is connected to the input end of the third isolator 20 through the first erbium-ytterbium co-doped fiber 19. The output end of the third isolator 20 is connected to the input end of the fifth beam splitter 21. The first splitting end of the fifth beam splitter 21 is connected to the output signal port 22. The second splitting end of the fifth beam splitter 21 is connected to the fifth photodetector 31.

[0059] Furthermore, the control circuit includes a first linear amplifier module (OPA1), which includes a DAC (Digital-to-Analog Converter), an ADC (Analog-to-Digital Converter), and an MCU. The first gain control loop includes a first PID control module (PID & Pump control1), a first current-to-voltage conversion module (Current Mirror & Log Converter1), a second current-to-voltage conversion module (Current Mirror & Log Converter2), and a second linear amplifier module (OPA2). The first linear amplifier module can be considered as part of either the first gain control loop or the second gain control loop.

[0060] Specifically, the input terminal of the first current-to-voltage conversion module is connected to the negative terminal of the first photodetector 23, the input terminal of the first linear amplification module is connected to the positive terminal of the first photodetector 23, the output terminal of the first current-to-voltage conversion module is connected to the ADC, and the output terminal of the first linear amplification module is connected to the first input terminal of the first PID control module.

[0061] The input terminal of the second linear amplifier module is connected to the positive terminal of the fourth photodetector 28, and the output terminal of the second linear amplifier module is connected to the second input terminal of the first PID control module.

[0062] The input terminal of the second current-to-voltage conversion module is connected to the negative terminal of the fourth photodetector 28, and the output terminal of the second current-to-voltage conversion module is connected to the ADC.

[0063] The first output terminal of the first PID control module is connected to the first pump source 24, and the second output terminal of the first PID control module is connected to the second pump source 27.

[0064] The second gain control loop includes a second PID control module (PID & Pump control 2), a third current-to-voltage conversion module (Current Mirror & Log Converter 3), and a third linear amplification module (OPA 3);

[0065] The input terminal of the third current-to-voltage conversion module is connected to the negative terminal of the fifth photodetector 31, and the input terminal of the third linear amplification module is connected to the positive terminal of the fifth photodetector 31.

[0066] The output terminal of the third current-to-voltage conversion module is connected to the ADC, the output terminal of the third linear amplifier module is connected to the first input terminal of the second PID control module, and the output terminal of the first linear amplifier module is connected to the second input terminal of the second PID control module.

[0067] The first output terminal of the second PID control module is connected to the first multimode pump source 29, and the second output terminal of the second PID control module is connected to the second multimode pump source 30.

[0068] The MCU is connected to the first PID control module and the second PID control module respectively. The input terminal of the DAC is connected to the MCU, and the output terminal of the DAC is connected to the first PID control module and the second PID control module respectively.

[0069] Furthermore, the control circuit also includes a connector connected to the MCU, the connector receiving a switching signal for controlling the switching state of the high-power fiber optic amplifier and transmitting it to the MCU;

[0070] The MCU is used to turn on the high-power fiber amplifier when the switch signal is valid;

[0071] The MCU obtains the input optical power of the high-power fiber amplifier through the first current-to-voltage conversion module and the ADC; the MCU is used to turn off the high-power fiber amplifier when the input optical power is lower than the shutdown threshold and / or the switch signal is invalid.

[0072] Specifically, in one embodiment of this utility model, the current-to-voltage conversion module (first current-to-voltage conversion module and second current-to-voltage conversion module) includes a current mirror circuit and a logarithmic amplifier circuit. The first photodetector 23 detects the input optical signal of the fiber optic amplifier and converts the input optical signal into a first current signal. The first linear amplifier module converts and linearly amplifies the first current signal into a first voltage signal (Input Ctrl). The first voltage signal is input to the first input terminal of the first PID control module. The current mirror circuit in the first current-to-voltage conversion module copies the first current signal at a 1:1 ratio and transmits it to the logarithmic amplifier circuit. The logarithmic amplifier circuit converts the copied current signal into a second voltage signal (Input log ADC). The second voltage signal is logarithmically related to the first current signal. The second voltage signal is input to the ADC.

[0073] The fourth photodetector 28 detects the output optical signal of the first gain unit of the fiber amplifier and converts the output optical signal of the first gain unit into a second current signal. The second linear amplification module converts and linearly amplifies the second current signal into a third voltage signal (Mid Output Ctrl). The third voltage signal is input to the second input terminal of the first PID control module. The current mirror circuit in the second current-voltage conversion module copies the second current signal at a 1:1 ratio and transmits it to the logarithmic amplifier circuit. The logarithmic amplifier circuit converts the copied current signal into a fourth voltage signal (Mid Output log ADC). The fourth voltage signal is logarithmically related to the second current signal and is input to the ADC.

[0074] The fifth photodetector 31 detects the output optical signal of the second gain unit of the fiber optic amplifier and converts it into a third current signal. The second linear amplification module converts and linearly amplifies the third current signal into a fifth voltage signal (Output Ctrl), which is input to the first input terminal of the third PID control module. The current mirror circuit in the third current-to-voltage conversion module replicates the third current signal at a 1:1 ratio and transmits it to the logarithmic amplifier circuit. The logarithmic amplifier circuit converts the replicated current signal into a sixth voltage signal (Output log ADC), which is logarithmically related to the third current signal. The sixth voltage signal is input to the ADC. The first voltage signal is also input to the second input terminal of the second PID control module. The current mirror circuit, logarithmic amplifier circuit, and linear amplification module can all adopt common forms in this technical field.

[0075] The PID control module (first PID control module and second PID control module) includes a PID controller and a pump source drive circuit. The MCU is connected to the PID controller in the first PID control module and the second PID control module respectively. The input terminal of the DAC is connected to the MCU, and the output terminal of the DAC is connected to the PID controller in the first PID control module and the second PID control module respectively.

[0076] The specific working process of the control circuit is as follows:

[0077] The MCU receives a switch signal through a connector. When the switch signal is valid, the MCU enables the first PID control module. The first gain control loop controls the first-stage gain unit to start working, and the first PID control module performs PID control on the output optical power of the first-stage gain unit. In one possible implementation, the MCU inputs a digital signal corresponding to the first target gain signal to the DAC. The DAC converts the digital signal into an analog signal of the first target gain signal and inputs it to the PID controller in the first PID control module. The PID controller in the first PID control module uses the first pump drive signal as the control quantity, the sum of the first voltage signal and the first target gain signal as the target quantity, and the third voltage signal as the feedback quantity. It performs PID control based on the first voltage signal, the third voltage signal, and the first target gain signal to generate the first pump drive signal. The pump source drive circuit in the first PID control module controls the drive current of the first pump source 24 and the second pump source 27 according to the first pump drive signal to stabilize the output optical power of the first gain unit at the first target optical power. The PID controller and pump source drive circuit can be common forms in this technical field, and the PID controller can perform PID control in a manner consistent with existing technologies.

[0078] The first voltage signal (Input log ADC) is converted into a digital signal by the ADC and input to the MCU. The MCU calculates the input optical power based on the converted digital signal and compares the input optical power with a threshold optical power. When the input optical power is greater than the threshold optical power, the MCU enables the second PID control module. The second gain control loop controls the second-stage gain unit to start working, and the second PID control module performs PID control on the output optical power of the second-stage gain unit. In one possible implementation, the MCU inputs a second target gain signal to the PID controller in the second PID control module via the DAC. The PID controller in the second PID control module uses the second pump drive signal as the control quantity, the sum of the first voltage signal and the first target gain signal as the target quantity, and the fifth voltage signal as the feedback quantity. It performs PID control based on the first voltage signal, the fifth voltage signal, and the second target gain signal to generate the second pump drive signal. The pump source drive circuit in the second PID control module controls the drive current of the first multimode pump source 29 and the second multimode pump source 30 according to the second pump drive signal to stabilize the output optical power of the second-stage gain unit at the second target optical power.

[0079] When the MCU detects that the switch signal becomes invalid and / or the input optical power is less than the shutdown threshold, it sequentially stops enabling the second PID control module and the first PID control module, thereby sequentially shutting down the second-stage gain unit and the first-stage gain unit to ensure optical path safety. The specific method by which the MCU enables the first / second PID control modules can be consistent with existing technologies.

[0080] Furthermore, the above control logic can generally be implemented using a firmware algorithm built into the MCU to sequentially control the operating states of the first gain unit and the second gain unit when the fiber optic amplifier is turned on or off. However, in the extreme case of a power supply failure for the MCU, the MCU is in an uncontrolled state and cannot complete the above logic control, thus failing to guarantee the turn-on and turn-off sequence of the fiber optic amplifier.

[0081] Therefore, to prevent the second-stage gain unit from generating a large ASE signal due to the lack of signal light input when the power supply fails, an additional power failure detection module is required. During the operation of the high-power fiber amplifier, the power supply to the high-power fiber amplifier is detected for power failure, and the second-stage gain unit is immediately shut down upon detection of a power failure. Subsequently, the first-stage gain unit shuts down naturally as the power is depleted, thus achieving the shutdown sequence of shutting down the second-stage gain unit first, and then the first-stage gain unit. This ensures that the high-power amplifier can operate safely and reliably even under extreme power failure conditions, avoiding damage to internal components.

[0082] Please refer to Figure 3 The control circuit also includes a power management module and a power failure detection module;

[0083] The power supply is connected to the power management module via a connector. The power management module is used to supply power to the control module, the power failure detection module, the first gain control loop, the second gain control loop, the first-stage gain unit, and the second-stage gain unit. The power management module includes a first DC-DC conversion circuit, which is used to convert the power supply voltage into the operating voltage required by the first multimode pump source and the second multimode pump source, and to supply power to the first multimode pump source and the second multimode pump source.

[0084] The power failure detection module is used to detect power failure of the power supply. When the power failure detection module detects that the power supply is cut off, it controls the first DC-DC conversion circuit to stop supplying power to the first multimode pump source and the second multimode pump source, so as to shut down the second-stage gain unit.

[0085] The power failure detection module includes a voltage comparator U1, a capacitor C1, resistors R1, R2, R3, and R4. The non-inverting input of voltage comparator U1 is connected to one end of resistor R1 and one end of resistor R2. The other end of resistor R1 is connected to the power supply, and the other end of resistor R2 is connected to analog ground. The inverting input of voltage comparator U1 is connected to one end of resistor R3. The other end of resistor R3 is connected to a reference voltage source. The output of voltage comparator U1 is connected to the enable terminal of the first DC-DC conversion circuit through resistor R4. One end of capacitor C1 is connected to the power supply terminal of voltage comparator U1, and the other end of capacitor C1 is connected to the ground terminal of voltage comparator U1.

[0086] Specifically, the power management module (POWER MANAGER) also includes multiple DC-DC conversion circuits, which are used to convert the power supply voltage into the required voltage for the powered objects. The powered objects are the devices in the control module, power failure detection module, first gain control loop, second gain control loop, first-stage gain unit, and second-stage gain unit. Different powered objects require different voltage specifications, so different specifications of DC-DC conversion circuits are required for power supply. For example, the first pump source 24 and the second pump source 27 are designed with lower drive voltages to reduce power consumption on the drive power transistors and reduce heat generation; the first multimode pump source 29 and the second multimode pump source 30 have larger drive currents and require further reduction in power consumption on the drive power transistors, so their drive voltages need to be even lower.

[0087] In this embodiment, the first DC-DC conversion circuit is a DC-DC chip (U2). Figure 3 The document also shows the peripheral circuitry of the DC-DC chip, including capacitors C2, C3, C4, and C5, inductor L1, resistors R6, R7, R8, R9, R10, and R11. The model of the DC-DC chip can be set according to actual needs.

[0088] The ILMT pin of the DC-DC chip is grounded through resistor R6. The enable pin of the DC-DC chip, i.e., the aforementioned enable terminal, is connected to the power supply through resistor R5. The VCC pin is connected to one end of capacitor C2. The PG pin is connected to one end of capacitor C2 through resistor R7. The other end of capacitor C2 is grounded. The VIN pin is connected to the power supply. The BS pin is connected to the LX pin through capacitor C3. The LX pin is connected to inductor L1. One end of resistors R8, R9, and R10 is connected to the FBS pin. The other end of resistor R8 is connected to one end of capacitor C4. The other end of resistor R9 is connected to the GNDS pin through resistor R11. The other end of resistor R10 and the other end of capacitor C4 form the output terminal, which is connected to the first multimode pump source 29 and the second multimode pump source 30. The MODE pin is grounded through resistor R12, and the SS pin is grounded through capacitor C5.

[0089] In this embodiment, in the power failure detection module, the voltage comparator U1 is a precision voltage comparator with open-drain output. The power supply voltage is 5V. The inverting input terminal of U1 is connected to a 2.5V reference voltage source. Resistors R1 and R2 form a voltage divider circuit to divide the power supply voltage. The output signal of the voltage comparator U1 is input to the enable pin (EN) of the DC-DC chip through resistor R4.

[0090] The specific working principle of the power failure detection module is as follows: when the power supply voltage is normal, the voltage at the non-inverting input terminal (IN+) of the voltage comparator U1 is greater than the voltage at the inverting input terminal (IN-). The output of the voltage comparator U1 is an open-drain output, which has no effect on the enable pin (EN) of the DC-DC chip U2. The DC-DC chip U2 works normally, providing normal power to the first multimode pump source 29 and the second multimode pump source 30.

[0091] When a power outage occurs, the power supply voltage drops, and the voltage at the non-inverting input (IN+) of voltage comparator U1 is less than the voltage at the inverting input (IN-). The output of voltage comparator U1 is low, and the enable pin of DC-DC chip U2 is pulled low. DC-DC chip U2 stops outputting voltage, and the first multimode pump source 29 and the second multimode pump source 30 powered by it naturally shut down. At this time, the power supply voltage has not been completely consumed, so the single-mode pump sources in the first-stage gain unit, namely the first pump source 24 and the second pump source 27, still have current driving, and the first-stage gain unit still outputs signal light. As the power gradually depletes, the first-stage gain unit naturally shuts down, thus achieving the function of the second-stage gain unit shutting down before the first-stage gain unit when power is lost. This mechanism completely eliminates the possibility of the second-stage gain unit driving the multimode pump with a large current, which could generate a huge ASE signal due to the lack of signal light and burn out the optical path devices.

[0092] In the description of this specification, the terms "first," "second," "third," "fourth," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. The use of the term "an embodiment / mode," etc., means that a specific feature, structure, or characteristic described in connection with that embodiment / mode is included in at least one embodiment / mode of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode. In the description of this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0093] Those skilled in the art should understand that the above descriptions are merely preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A control circuit for a high-power fiber optic amplifier, characterized in that, The high-power fiber amplifier includes a first-stage gain unit and a second-stage gain unit arranged sequentially along the direction of light transmission. The control circuit of the high-power fiber amplifier includes a control module, a first gain control loop, and a second gain control loop connected to each other. The first gain control loop is connected to a first-stage gain unit, and the second gain control loop is connected to a second-stage gain unit. When the fiber amplifier is turned on, the control module controls the first gain control loop to turn on the first-stage gain unit. The first gain control loop is used to collect the output optical power of the first-stage gain unit and transmit it to the control module. When the output optical power of the first-stage gain unit is greater than the threshold optical power, the control module controls the second gain control loop to turn on the second-stage gain unit. When shutting down the fiber amplifier, the control module first controls the second gain control loop to shut down the second-stage gain unit, and then controls the first gain control loop to shut down the first-stage gain unit.

2. The control circuit of the high-power fiber optic amplifier according to claim 1, characterized in that, The first-stage gain unit includes a first photodetector, a fourth photodetector, a first pump source, and a second pump source; The control circuit includes a first linear amplifier module, which includes an MCU, a DAC, and an ADC; the first gain control loop includes a first PID control module, a first current-to-voltage conversion module, a second current-to-voltage conversion module, and a second linear amplifier module. The input terminal of the first current-to-voltage conversion module is connected to the negative terminal of the first photodetector, the input terminal of the first linear amplification module is connected to the positive terminal of the first photodetector, the output terminal of the first current-to-voltage conversion module is connected to the ADC, and the output terminal of the first linear amplification module is connected to the first input terminal of the first PID control module.

3. The control circuit of the high-power fiber optic amplifier according to claim 2, characterized in that, The input terminal of the second linear amplifier module is connected to the positive terminal of the fourth photodetector, and the output terminal of the second linear amplifier module is connected to the second input terminal of the first PID control module. The input terminal of the second current-to-voltage conversion module is connected to the negative terminal of the fourth photodetector, and the output terminal of the second current-to-voltage conversion module is connected to the ADC. The first output terminal of the first PID control module is connected to the first pump source, and the second output terminal of the first PID control module is connected to the second pump source.

4. The control circuit of the high-power fiber optic amplifier according to claim 3, characterized in that, The second-stage gain unit includes a fifth photodetector, a first multimode pump source, and a second multimode pump source; The second gain control loop includes a second PID control module, a third current-to-voltage conversion module, and a third linear amplification module; The input terminal of the third current-to-voltage conversion module is connected to the negative terminal of the fifth photodetector, and the input terminal of the third linear amplification module is connected to the positive terminal of the fifth photodetector. The output terminal of the third current-to-voltage conversion module is connected to the ADC, the output terminal of the third linear amplifier module is connected to the first input terminal of the second PID control module, and the output terminal of the first linear amplifier module is also connected to the second input terminal of the second PID control module. The first output terminal of the second PID control module is connected to the first multimode pump source, and the second output terminal of the second PID control module is connected to the second multimode pump source.

5. The control circuit for the high-power fiber optic amplifier according to claim 4, characterized in that, The MCU is connected to the first PID control module and the second PID control module respectively. The input terminal of the DAC is connected to the MCU, and the output terminal of the DAC is connected to the first PID control module and the second PID control module respectively.

6. The control circuit for the high-power fiber optic amplifier according to claim 5, characterized in that, It also includes a connector for connecting to the MCU, the connector receiving a switching signal for controlling the switching state of the high-power fiber optic amplifier and transmitting it to the MCU; The MCU is used to turn on the high-power fiber amplifier when the switch signal is valid; The MCU obtains the input optical power of the high-power fiber amplifier through the first current-to-voltage conversion module and the ADC; The MCU is used to shut down the high-power fiber amplifier when the input optical power is below the shutdown threshold and / or the switch signal is invalid.

7. The control circuit for the high-power fiber optic amplifier according to claim 6, characterized in that, It also includes a power management module and a power failure detection module; The power supply is connected to the power management module via a connector. The power management module is used to supply power to the control module, the power failure detection module, the first gain control loop, the second gain control loop, the first-stage gain unit, and the second-stage gain unit. The power management module includes a first DC-DC conversion circuit, which is used to convert the power supply voltage into the operating voltage required by the first multimode pump source and the second multimode pump source, and to supply power to the first multimode pump source and the second multimode pump source. The power failure detection module is used to detect power failure of the power supply. When the power failure detection module detects that the power supply is cut off, it controls the first DC-DC conversion circuit to stop supplying power to the first multimode pump source and the second multimode pump source, so as to shut down the second-stage gain unit.

8. The control circuit for the high-power fiber optic amplifier according to claim 7, characterized in that, The power failure detection module includes a voltage comparator U1, a capacitor C1, resistors R1, R2, R3, and R4, wherein... The non-inverting input terminal of the voltage comparator U1 is connected to one end of resistor R1 and one end of resistor R2. The other end of resistor R1 is connected to the power supply, and the other end of resistor R2 is connected to analog ground. The inverting input terminal of the voltage comparator U1 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the reference voltage source, and the output terminal of the voltage comparator U1 is connected to the enable terminal of the first DC-DC conversion circuit through the resistor R4. One end of the capacitor C1 is connected to the power supply terminal of the voltage comparator U1, and the other end of the capacitor C1 is connected to the ground terminal of the voltage comparator U1.

9. The control circuit of the high-power fiber optic amplifier according to claim 4, characterized in that, The first-stage gain unit further includes an input signal port, a first optical splitter, a first isolator, a first wavelength division multiplexer, a first erbium-doped fiber segment, a second wavelength division multiplexer, a first IGFF unit, a third wavelength division multiplexer, a second erbium-doped fiber segment, a second IGFF unit, a second optical splitter, a variable attenuator, a third optical splitter, a fourth wavelength division multiplexer, a third erbium-doped fiber segment, a second isolator, a fourth optical splitter, a second photodetector, and a third photodetector, wherein... The input signal port is connected to the input end of the first beam splitter, the first beam splitter's first beam splitter's first beam splitter's first beam splitter's first beam splitter's first beam splitter's input end is connected to the input end of the first isolator, the second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's second beam splitter's third ... second beam splitter's second beam splitter's second beam splitter' The output of the first wavelength division multiplexer is connected to the input of the second wavelength division multiplexer through a first section of erbium-doped fiber. The first output of the second wavelength division multiplexer is connected to the first input of the third wavelength division multiplexer. The second output of the second wavelength division multiplexer is connected to the second input of the third wavelength division multiplexer through a first IGFF unit. The output of the third wavelength division multiplexer is connected to the input of the second IGFF unit via a second erbium-doped fiber. The output of the second IGFF unit is connected to the input of the second beam splitter. The first beam splitter of the second beam splitter is connected to the input of the variable attenuator. The second beam splitter of the second beam splitter is connected to the second photodetector. The output of the variable attenuator is connected to the input of the third beam splitter. The first beam splitter of the third beam splitter is connected to the first input of the fourth wavelength division multiplexer. The second beam splitter of the third beam splitter is connected to the third photodetector. The second input terminal of the fourth wavelength division multiplexer is connected to the second pump source, the output terminal of the fourth wavelength division multiplexer is connected to the input terminal of the second isolator through the third erbium-doped fiber, the output terminal of the second isolator is connected to the input terminal of the fourth beam splitter, and the first beam splitter of the fourth beam splitter is connected to the fourth photodetector.

10. The control circuit of the high-power fiber optic amplifier according to claim 9, characterized in that, The second-stage gain unit includes a multimode pump combiner, a first section of erbium-ytterbium co-doped fiber, a third isolator, a fifth beam splitter, an output signal port, a first multimode pump source, a second multimode pump source, and a fifth photodetector; The second splitting end of the fourth beam splitter is connected to the first input end of the multimode pump combiner. The first multimode pump source is connected to the second input end of the multimode pump combiner. The second multimode pump source is connected to the third input end of the multimode pump combiner. The output end of the multimode pump combiner is connected to the input end of the third isolator through a first section of erbium-ytterbium co-doped fiber. The output end of the third isolator is connected to the input end of the fifth beam splitter. The first splitting end of the fifth beam splitter is connected to the output signal port. The second splitting end of the fifth beam splitter is connected to the fifth photodetector.

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