Loop control system and method

Abstract

The application relates to the field of optical fiber communication, and discloses a loop control system and method, the system comprising a coupler, a pump laser, an optical fiber amplifier, a variable optical attenuator, an optical splitter, a photodetector and a loop controller; in the application, a control feedback loop, i.e. the control feedback loop of the variable optical attenuator, is arranged; the actual output light of the system is received by the photodetector, the photoelectric signal is converted and input to the loop controller, so that the loop controller can adjust the attenuation value of the variable optical attenuator according to the actual output light power of the system, thereby improving the stability of the actual output light power of the system; meanwhile, the control feedback loop of the variable optical attenuator is adopted, so that the noise interference caused by the frequent change of the size of the pump light of the pump laser is eliminated.

Description

Technical Field

[0001] This application relates to the field of optical fiber communication, and in particular to a loop control system and method. Background Technology

[0002] Optical fiber amplifiers (OFAs) are widely used in optical fiber communication lines, such as erbium-doped fiber amplifiers, praseodymium-doped fiber amplifiers, and niobium-doped fiber amplifiers. As a novel all-optical amplifier, the OFA eliminates the need for complex processes like photoelectric conversion, electro-optic conversion, and signal regeneration, directly amplifying signals optically. It exhibits excellent "transparency" and is particularly suitable for relay amplification in long-distance optical communication. OFA lays a technological foundation for realizing all-optical communication. Currently, the application of fiber amplifiers involves simultaneously injecting signal light and pump light into the fiber amplifier. Under the excitation of the pump light, the fiber amplifier amplifies and outputs the signal light. To achieve a relatively stable output optical signal, related technologies typically adjust the amplification factor of the input light by adjusting the magnitude of the pump light output from the pump laser, thereby stabilizing the output optical signal.

[0003] However, the frequent changes in the magnitude of the pump light output by the pump laser can cause significant disturbances to the output light, resulting in substantial noise interference. Summary of the Invention

[0004] The main objective of this application is to propose a loop control system and method to reduce the fluctuation of the system's output light and improve the stability of the system's output light power.

[0005] To achieve the above objectives, this application provides a loop control system, characterized in that it includes: a coupler, a pump laser, an fiber amplifier, a variable optical attenuator, a beam splitter, a photodetector, and a loop controller; the first input terminal of the coupler serves as the input terminal of the system and receives signal light; the second input terminal of the coupler is connected to the output terminal of the pump laser; the output terminal of the coupler is connected to the input terminal of the fiber amplifier, the output terminal of the fiber amplifier is connected to the input terminal of the variable optical attenuator, and the output terminal of the variable optical attenuator is connected to the input terminal of the beam splitter; the first output terminal of the beam splitter serves as the output terminal of the system, the second output terminal of the beam splitter is connected to the input terminal of the photodetector, the output terminal of the photodetector is connected to the input terminal of the loop controller, and the first control terminal of the loop controller is connected to the control terminal of the variable optical attenuator.

[0006] To achieve the above objectives, this application also provides a loop control method applied to a loop controller in a loop control system; the loop control system further includes: a coupler, a pump laser, an fiber amplifier, a variable optical attenuator, a beam splitter, and a photodetector; the first input terminal of the coupler serves as the input terminal of the system and receives signal light; the second input terminal of the coupler is connected to the output terminal of the pump laser; the output terminal of the coupler is connected to the input terminal of the fiber amplifier, the output terminal of the fiber amplifier is connected to the input terminal of the variable optical attenuator, and the output terminal of the variable optical attenuator is connected to the input terminal of the beam splitter; the first output terminal of the beam splitter serves as the output terminal of the system. The second output terminal of the beam splitter is connected to the input terminal of the photodetector, the output terminal of the photodetector is connected to the input terminal of the loop controller, and the first control terminal of the loop controller is connected to the control terminal of the variable optical attenuator. The method includes: acquiring the electrical signal output by the photodetector and determining the actual output optical power of the system based on the electrical signal; if the actual output optical power of the system does not match the preset output optical power of the system, obtaining the target attenuation value of the variable optical attenuator based on the actual output optical power of the system, the preset output optical power of the system, and the current attenuation value of the variable optical attenuator; and adjusting the attenuation value of the variable optical attenuator to the target attenuation value.

[0007] The loop control system proposed in this application includes a control feedback loop, namely the control feedback loop of the variable optical attenuator. This loop receives the actual output light of the system through a photodetector, converts it into a photoelectric signal, and inputs it to the loop controller. This allows the loop controller to adjust the attenuation value of the variable optical attenuator according to the actual output optical power of the system, thereby improving the stability of the actual output optical power. Furthermore, by employing the control feedback loop of the variable optical attenuator, this application eliminates noise interference caused by frequent changes in the magnitude of the pump light from the pump laser. Attached Figure Description

[0008] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0009] Figure 1 This is a schematic diagram of the loop control system according to the first embodiment of this application;

[0010] Figure 2 This is a schematic diagram of the loop controller according to the first embodiment of this application;

[0011] Figure 3This is a schematic diagram of the loop control system according to the second embodiment of this application;

[0012] Figure 4 This is a flowchart illustrating the loop control method according to the third embodiment of this application;

[0013] Figure 5 This is a flowchart illustrating the loop control method according to the fourth embodiment of this application;

[0014] Figure 6 This is a flowchart illustrating the loop control method according to the fifth embodiment of this application. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this application to help readers better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0016] The first embodiment of this application relates to a loop control system. A schematic diagram of the loop control system in this embodiment is shown below. Figure 1 As shown, it includes: coupler 101, pump laser 102, fiber amplifier 103, variable optical attenuator 104, beam splitter 105, photodetector 106, and loop controller 107.

[0017] Specifically, the first input terminal of coupler 101 serves as the input terminal of the system and receives the signal light emitted by the signal source; the second input terminal of coupler 101 is connected to the output terminal of pump laser 102; the output terminal of coupler 101 is connected to the input terminal of fiber amplifier 103, the output terminal of fiber amplifier 103 is connected to the input terminal of variable optical attenuator 104, the output terminal of variable optical attenuator 104 is connected to the input terminal of beam splitter 105; the first output terminal of beam splitter 105 serves as the output terminal of the system, the second output terminal of beam splitter 105 is connected to the input terminal of photodetector 106, the output terminal of photodetector 106 is connected to the input terminal of loop controller 107, and the first control terminal of loop controller 107 is connected to the control terminal of variable optical attenuator 104.

[0018] Specifically, the variable optical attenuator 104, the beam splitter 105, the photodetector 106, and the loop controller 107 form a control feedback loop for the variable optical attenuator 104.

[0019] In practical applications, the wavelength and power of the signal light received at the first input terminal of coupler 101 can be set according to the actual application requirements. For example, the wavelength of the signal light can be set to 1550nm.

[0020] Specifically, the first input terminal of coupler 101 receives the signal light emitted by the signal source, and the second input terminal of coupler 101 is connected to the output terminal of pump laser 102 to receive the pump light from pump laser 102. In practical applications, the wavelength of the pump light can be 980nm or 1480nm. After receiving the signal light and pump light, coupler 101 couples the signal light and pump light into fiber amplifier 103. Within fiber amplifier 103, the signal light is amplified under the excitation of the pump light. The amplification factor of the signal light is positively correlated with the intensity of the pump light; that is, the stronger the pump light intensity, the greater the amplification factor of the signal light.

[0021] In one example, coupler 101 is an isolation coupler. Specifically, the coupler 101 has the function of an isolator. Since there will be reflected light signals during the transmission of signal light in the optical fiber, by setting the coupler 101 as an isolation coupler, the reflected light signals generated by the optical fiber amplifier 103 can be isolated, preventing the reflected signal light generated by the optical fiber amplifier 103 from affecting the operation of the pump laser 102.

[0022] Specifically, after the fiber amplifier 103 amplifies the signal light, the actual output optical power of the fiber amplifier 103 fluctuates significantly, affecting the system's stability. Therefore, in related technologies, to achieve stability in the actual output optical power, the loop controller 107 adjusts the output current of the pump laser 102 in real time based on the actual output optical power. However, the more times the pump laser 102 is adjusted, the more noise it generates while continuously adjusting the pump light. To simultaneously meet the requirements of both the stability of the actual output light and noise reduction, this application improves the stability of the actual output light by setting a feedback loop with a variable optical attenuator, while also avoiding the noise generated by excessively high adjustment frequencies of the pump laser 102 in related technologies.

[0023] In this embodiment, the actual output optical power of the fiber amplifier 103 is attenuated to a certain extent by the variable optical attenuator 104, thereby meeting the requirements of system stability.

[0024] Specifically, after the variable optical attenuator 104 attenuates the actual output optical power of the fiber amplifier 103, the splitter 105 outputs the attenuated output optical power of the fiber amplifier 103 to obtain the actual output light of the system. However, after the actual output optical power of the fiber amplifier 103 is attenuated by the variable optical attenuator 104, the actual output light power of the system may not be within the preset range. Therefore, the first output end of the splitter 105 is connected to the back-end device, such as the optical power monitor (OPM), as the output end of the system. The second output end of the splitter 105 is connected to the photodetector 106, transmitting part of the output light to the photodetector 106 for photoelectric signal conversion. After that, the converted electrical signal enters the loop controller 107. Through the control feedback loop of the variable optical attenuator 104, the attenuation value of the variable optical attenuator 104 can be adjusted in real time according to the output light power of the system, thereby reducing the fluctuation of the system's output light and improving the stability of the system's output optical power.

[0025] In one example, the fiber amplifier 103 is one of an erbium-doped fiber amplifier, a praseodymium-doped fiber amplifier, or a niobium-doped fiber amplifier. In practical applications, one type of fiber amplifier can be selected according to actual needs; this embodiment does not impose specific limitations.

[0026] The loop control system proposed in this application includes a control feedback loop, namely the control feedback loop of the variable optical attenuator. This loop receives the actual output light of the system through a photodetector, converts it into a photoelectric signal, and inputs it to the loop controller. This allows the loop controller to adjust the attenuation value of the variable optical attenuator according to the actual output optical power of the system, thereby improving the stability of the actual output optical power. Furthermore, by employing the control feedback loop of the variable optical attenuator, this application eliminates noise interference caused by frequent changes in the magnitude of the pump light from the pump laser.

[0027] In one example, such as Figure 2 As shown, the loop controller 107 includes: an analog-to-digital converter 1071, a controller 1072, an adder 1073, a first integrator 1074, a second integrator 1075, a first digital-to-analog converter 1076, and a second digital-to-analog converter 1077.

[0028] Specifically, controller 1072 is connected to analog-to-digital converter 1071, adder 1073, first integrator 1074, second integrator 1075, first digital-to-analog converter 1076, and second digital-to-analog converter 1077. The input terminal of analog-to-digital converter 1071 serves as the input terminal of loop controller, and the output terminal of analog-to-digital converter 1071 is connected to the input terminal of adder 1073. The output terminal of adder 1073 is connected to the input terminals of first integrator 1074 and second integrator 1075. The output terminal of first integrator 1074 is connected to the input terminal of first digital-to-analog converter 1076, and the output terminal of first digital-to-analog converter 1076 is connected to variable optical attenuator 104. The output terminal of second integrator 1075 is connected to the input terminal of second analog-to-digital converter 1077, and the output terminal of second digital-to-analog converter 1077 is connected to pump laser 102.

[0029] In practical applications, the controller 1072 has the function of initializing and driving control of other modules; the input terminal of the analog-to-digital converter 1071 receives the analog signal from the photodetector 106 and converts the analog signal from the photodetector into a digital signal; the adder 1073 is used to receive the digital signal output by the analog-to-digital converter 1071 and the instructions provided by the controller for calculation; the first integrator 1074 is used to perform integration calculation according to the data output by the adder 1073 and the instructions of the controller, and sends it to the first digital-to-analog converter 1076, which converts the integrated digital signal into an analog signal and inputs it to the variable optical attenuator 104; the second integrator 1075 is used to perform integration calculation according to the data output by the adder 1073 and the instructions of the controller, and sends it to the second digital-to-analog converter 1077, which converts the integrated digital signal into an analog signal and inputs it to the pump laser 102.

[0030] The second embodiment of the present invention relates to a loop control system. The second embodiment is largely the same as the first embodiment, with the main difference being that in the second embodiment, the second control terminal of the loop controller is connected to the control terminal of the pump laser. It should be noted that the relevant technical details of the first embodiment described above are still valid in this embodiment, and will not be repeated here to avoid repetition.

[0031] The schematic diagram of the loop control system in this embodiment is shown below. Figure 3 As shown, the loop control system includes: coupler 201, pump laser 202, fiber amplifier 203, variable optical attenuator 204, beam splitter 205, photodetector 206, and loop controller 207.

[0032] Specifically, the first input terminal of coupler 201 serves as the system input terminal and receives the signal light emitted by the signal source; the second input terminal of coupler 201 is connected to the output terminal of pump laser 202; the output terminal of coupler 201 is connected to the input terminal of fiber amplifier 203, the output terminal of fiber amplifier 203 is connected to the input terminal of variable optical attenuator 204, and the output terminal of variable optical attenuator 204 is connected to the input terminal of beam splitter 205; the first output terminal of beam splitter 205 serves as the system output terminal, the second output terminal of beam splitter 205 is connected to the input terminal of photodetector 206, the output terminal of photodetector 206 is connected to the input terminal of loop controller 207, the first control terminal of loop controller 207 is connected to the control terminal of variable optical attenuator 204, and the second control terminal of loop controller 207 is connected to the control terminal of pump laser 202.

[0033] In this embodiment, not only is there a control feedback loop for the variable optical attenuator 204, but also a control feedback loop for the pump laser 202 formed by the pump laser 202, the beam splitter 205, the photodetector 206, and the loop controller 207.

[0034] This embodiment has two control feedback loops: the control feedback loop of the variable optical attenuator 204 and the control feedback loop of the pump laser 202. The two feedback loops can selectively adjust at least one of the variable optical attenuator 204 and the pump laser 202. The two feedback loops can cooperate with each other to adjust the power of the actual output light of the system, thereby further improving the stability of the actual output light of the system.

[0035] In one example, such as Figure 3 As shown, the loop control system also includes an isolator 208. In this embodiment, by setting an isolator between the fiber amplifier 203 and the variable optical attenuator 204, the reflected light signal of the variable optical attenuator 204 can be isolated, preventing the reflected light signal of the variable optical attenuator 204 from affecting the operation of the fiber amplifier 203 and improving the stability of the system.

[0036] The third embodiment of this application relates to a loop control method applied to the loop control system in the first embodiment described above; a flowchart of the loop control method according to the third embodiment of this application is shown below. Figure 4 As shown, it includes the following steps:

[0037] Step 301: Obtain the electrical signal output by the photodetector and determine the actual output optical power of the system based on the electrical signal.

[0038] Specifically, after the photodetector receives the actual output light of the system from the beam splitter, it converts the actual output light into an electrical signal. The loop controller has a functional relationship between the actual output light of the system and the voltage of the electrical signal output by the photodetector. After receiving this electrical signal, the loop controller calculates the power of the actual output light of the system based on the functional relationship between the actual output light of the system and the electrical signal output by the photodetector, as well as the voltage of the electrical signal.

[0039] In one example, determining the actual output optical power of the system based on the electrical signal includes: obtaining the actual output optical power of the system based on the preset function between the actual output optical power of the system and the voltage of the electrical signal, and obtaining the actual output optical power of the system based on the voltage of the electrical signal.

[0040] Specifically, the loop control system has a preset function relating the actual output optical power to the voltage of the electrical signal. When the voltage of the electrical signal output by the photodetector is known, the loop controller can obtain the actual output optical power of the system based on this function.

[0041] In practical applications, the functional relationship between the actual output light power of the system and the voltage of the electrical signal output by the photodetector differs at different wavelengths. To avoid large errors in the actual output light power calculated by the loop controller due to wavelength differences, this application calibrates the preset function between the actual output light power of the system and the voltage of the electrical signal output by the photodetector before acquiring the electrical signal output by the photodetector, i.e. before the loop control system officially starts operating, and determines the coefficients of this function.

[0042] For example, the actual output optical power of the system is Pout0, and the voltage of the output electrical signal of the photodetector is V. TIA Both should satisfy V TIA The function relationship is k * Pout0 + b. However, since the values ​​of k and b differ at different wavelengths of the light transmitted by the system, this application requires that V be determined before the system is officially put into operation. TIA The function relationship = k*Pout0+b is calibrated to obtain the values ​​of k and b, thus completing the calibration of the function relationship, and the calibrated function relationship is stored in the loop controller.

[0043] Step 302: When the actual output light power of the system does not match the preset output light power of the system, the target attenuation value of the variable optical attenuator is obtained based on the actual output light power of the system, the preset output light power of the system, and the attenuation value of the current variable optical attenuator.

[0044] Specifically, the loop controller has a preset output optical power, i.e., the ideal output optical power of the system. After obtaining the actual output optical power of the system, the loop controller compares the actual output optical power with the preset output optical power. If the actual output optical power matches the preset output optical power, it means that the actual output optical power has reached the ideal state. At this time, it is sufficient to maintain the internal parameters of the variable optical attenuator, i.e., the control voltage, without the need for loop feedback control. However, if the actual output optical power does not match the preset output optical power, it means that the actual output optical power has not reached the ideal state. Therefore, the loop controller will calculate the attenuation value of the variable optical attenuator based on the actual output optical power, the preset output optical power, and the current attenuation value of the variable optical attenuator.

[0045] In one example, the target attenuation value of the variable optical attenuator is obtained based on the actual output light power of the system, the preset output light power of the system, and the current attenuation value of the variable optical attenuator. This includes: obtaining the adjustment value of the attenuation value of the variable optical attenuator based on the actual output light power of the system and the preset output light power of the system; and obtaining the target attenuation value based on the current attenuation value and the adjustment value of the variable optical attenuator.

[0046] Specifically, in this embodiment, the adjustment value of the attenuation value of the variable optical attenuator is first obtained based on the actual output light power of the system and the preset output light power of the system. Then, the specific process of obtaining the target attenuation value based on the current attenuation value and the adjustment value of the variable optical attenuator is as follows: when the actual output light power of the system is less than the preset output light power of the system, the difference between the current attenuation value and the adjustment value of the variable optical attenuator is taken as the target attenuation value; when the actual output light power of the system is greater than the preset output light power of the system, the sum of the current attenuation value and the adjustment value of the variable optical attenuator is taken as the target attenuation value.

[0047] In practical applications, when the system starts operating, the attenuation value inside the variable optical attenuator is obtained based on the system's preset output optical power Pout and preset fiber amplifier output optical power Pout1, that is, the attenuation value VOA1 = Pout1 - Pout at this time. However, during the actual operation of the system, each operating parameter in the system may deviate due to external factors. Therefore, it is necessary to adjust the attenuation value of the variable optical attenuator through a feedback control loop so that the actual output optical power of the system is within the ideal range.

[0048] Step 303: Adjust the attenuation value of the variable optical attenuator to the target attenuation value.

[0049] Specifically, after the loop controller obtains the target attenuation value, it will adjust the attenuation value of the variable optical attenuator to the target attenuation value, thereby realizing the adjustment of the control feedback loop of the variable optical attenuator.

[0050] In one example, adjusting the attenuation value of the variable optical attenuator to the target attenuation value includes: obtaining the target control voltage of the variable optical attenuator based on the target attenuation value; and adjusting the control voltage of the variable optical attenuator to the target control voltage so that the attenuation value of the variable optical attenuator is adjusted to the target attenuation value.

[0051] Specifically, the loop controller is configured with a functional relationship between the attenuation value of the variable optical attenuator and its control voltage. After obtaining the target attenuation value of the variable optical attenuator, the loop controller obtains the target control voltage of the variable optical attenuator based on the functional relationship between the attenuation value and the control voltage, and the target attenuation value. This voltage is then input to the variable optical attenuator so that it can control the attenuation value to the target value. In other words, the attenuation value of the variable optical attenuator is adjusted to the target attenuation value, thereby attenuating the output light power of the fiber amplifier and ensuring that the actual output light power of the system matches the preset output light power of the system.

[0052] In practical applications, the loop controller has a preset function for the attenuation value and control voltage of the variable optical attenuator. This function consists of multiple linear function segments. The loop controller can determine the linear function segment corresponding to the target attenuation value based on the target attenuation value. Then, the control voltage of the variable optical attenuator is obtained based on the linear function segment and the target attenuation value.

[0053] In this embodiment, the attenuation value of the variable optical attenuator is adjusted by the control loop of the variable optical attenuator, thereby attenuating the output optical power of the fiber amplifier, so that the actual output optical power of the system is within a preset range. At the same time, by adjusting the actual output optical power of the system through the variable optical attenuator, the frequency of pump laser adjustment can be reduced, which is also beneficial to reducing the noise problem caused by excessive adjustment of the pump laser.

[0054] The fourth embodiment of this application relates to a loop control method applied to the loop control system in the second embodiment described above. The fourth embodiment is largely the same as the third embodiment, with the main difference being that in the fourth embodiment, the second control terminal of the loop controller in the loop control system is connected to the control terminal of the pump laser. After acquiring the electrical signal output by the photodetector and determining the actual output optical power of the system based on the output electrical signal, a pump laser adjustment step is also included.

[0055] The flowchart of the loop control method involved in the fourth embodiment of this application is shown below. Figure 5 As shown, it includes the following steps:

[0056] Step 401: Obtain the electrical signal output by the photodetector and determine the actual output optical power of the system based on the electrical signal.

[0057] Step 4021: When the actual output light power of the system does not match the preset output light power of the system, the target attenuation value of the variable optical attenuator is obtained based on the actual output light power of the system, the preset output light power of the system, and the current attenuation value of the variable optical attenuator.

[0058] Step 4031: Adjust the attenuation value of the variable optical attenuator to the target attenuation value.

[0059] Steps 401, 4021, and 4031 described above are the same as steps 301 to 303 in the third embodiment, and will not be repeated here to avoid repetition.

[0060] This embodiment, after acquiring the electrical signal output by the photodetector and determining the actual output optical power of the system based on the output electrical signal, also includes a pump laser adjustment step, which is as follows:

[0061] Step 4022: Obtain the actual output optical power of the fiber amplifier by summing the actual output optical power of the system with the current attenuation value of the variable optical attenuator.

[0062] Specifically, in the third embodiment described above, the attenuation value of the variable optical attenuator is adjusted according to the preset output optical power of the fiber amplifier. However, in practical applications, due to the aging of the pump laser itself or the influence of other devices, the actual output optical power of the fiber amplifier may decrease, affecting the actual output optical power of the system. Therefore, this application needs to adjust the pump light of the pump laser through the control feedback loop of the pump laser so that the actual output optical power of the fiber amplifier is consistent with the preset output optical power of the fiber amplifier.

[0063] Specifically, the actual output light power of the system is obtained by attenuating the actual output light power of the fiber amplifier using a variable optical attenuator. Therefore, the actual output light power of the fiber amplifier should be equal to the sum of the actual output light power of the system and the current attenuation value of the variable optical attenuator. In this embodiment, the actual output light power of the fiber amplifier is obtained by adding the actual output light power of the system to the current attenuation value of the variable optical attenuator. Then, it is determined whether the pump light of the pump laser needs to be adjusted based on the magnitude of the actual output light power of the fiber amplifier and the preset output light power of the fiber amplifier.

[0064] Step 4032: When the actual output optical power of the fiber amplifier does not match the preset output optical power of the fiber amplifier, the target output current is obtained based on the actual output optical power of the fiber amplifier, the preset output optical power of the fiber amplifier, and the current output current of the pump laser.

[0065] Step 4033: Adjust the output current of the pump laser to the target output current.

[0066] Specifically, the loop controller has a preset output optical power of an optical fiber amplifier, which is the ideal output optical power of the optical fiber amplifier.

[0067] Specifically, the loop controller is set with a redundancy value. When the difference between the actual output optical power of the fiber optic amplifier and the preset output optical power of the fiber optic amplifier is within this redundancy value, it means that the actual output optical power of the fiber optic amplifier matches the preset output optical power of the fiber optic amplifier. When the difference between the actual output optical power of the fiber optic amplifier and the preset output optical power of the fiber optic amplifier is not within this redundancy value, it means that the actual output optical power of the fiber optic amplifier does not match the preset output optical power of the fiber optic amplifier.

[0068] Specifically, after the loop controller obtains the actual output optical power of the fiber amplifier, if the actual output optical power of the fiber amplifier does not match the preset output optical power of the fiber amplifier, that is, if the difference between the actual output optical power of the fiber amplifier and the preset output optical power of the fiber amplifier is greater than the redundancy value, the target output current is obtained based on the actual output optical power of the fiber amplifier, the preset output optical power of the fiber amplifier, and the current output current of the pump laser. The output current of the pump laser is then adjusted to the target output current, thereby adjusting the pump light output by the pump laser so that the actual output optical power of the fiber amplifier is consistent with the preset output optical power of the fiber amplifier.

[0069] Specifically, the process of obtaining the target output current is as follows: the difference between the actual output optical power of the fiber amplifier and the preset output optical power of the fiber amplifier is integrated, and the adjustment value of the output current of the pump laser is obtained by using a digital soft-start algorithm; the target output current is obtained based on the adjustment value and the current output current of the pump laser.

[0070] In this embodiment, two control feedback loops are set up: a control feedback loop for the variable optical attenuator and a control feedback loop for the pump laser. The two feedback loops selectively adjust at least one of the variable optical attenuator and the pump laser. The two feedback loops can cooperate with each other to adjust the power of the actual output light of the system, thereby further improving the stability of the actual output light of the system.

[0071] The fifth embodiment of this application relates to a loop control method, which is applied to the loop control system in the first and second embodiments described above. The fifth embodiment is largely the same as the third embodiment, with the main difference being that: in the fifth embodiment, after obtaining the target attenuation value of the variable optical attenuator based on the actual output optical power of the system, the preset output optical power of the system, and the current attenuation value of the variable optical attenuator, the method further includes: determining whether the target attenuation value is within the preset attenuation range of the variable optical attenuator.

[0072] The flowchart of the loop control method involved in the fifth embodiment of this application is shown below. Figure 6 As shown, it includes the following steps:

[0073] Step 501: Obtain the electrical signal output by the photodetector and determine the actual output light power of the system based on the electrical signal.

[0074] Step 502: When the actual output light power of the system does not match the preset output light power of the system, the target attenuation value of the variable optical attenuator is obtained based on the actual output light power of the system, the preset output light power of the system, and the current attenuation value of the variable optical attenuator.

[0075] Step 503: Determine whether the target attenuation value is within the preset attenuation range of the variable optical attenuator.

[0076] Specifically, if the target attenuation value is within the preset attenuation range of the variable optical attenuator, proceed to step 504 to adjust the attenuation value of the variable optical attenuator to the target attenuation value; if the target attenuation value is not within the preset attenuation range of the variable optical attenuator, proceed to step 505 to adjust the pump laser.

[0077] Step 504: Adjust the attenuation value of the variable optical attenuator to the target attenuation value.

[0078] Step 505: Calculate the actual output optical power of the fiber amplifier based on the actual output optical power of the system and the current attenuation value of the variable optical attenuator.

[0079] Step 506: Obtain the target output current of the pump laser based on the actual output optical power of the fiber amplifier, the preset output optical power of the fiber amplifier, and the current output current of the pump laser.

[0080] Step 507: Adjust the output current of the pump laser to the target output current.

[0081] It is not difficult to see that steps 501, 502, and 504 are the same as steps 301 to 303 in the third embodiment, and steps 505, 506, and 507 are the same as steps 4022, 4032, and 4033 in the fourth embodiment. To avoid repetition, they will not be described again here.

[0082] In this embodiment, it is necessary to determine whether the target attenuation value is within the preset attenuation range of the variable optical attenuator. When the target attenuation value is not within the preset attenuation range, the attenuation value of the variable optical attenuator cannot be adjusted to the target attenuation value, and the control feedback loop of the variable optical attenuator cannot adjust the actual output optical power of the current system. Therefore, in this embodiment, when the target attenuation value is not within the preset attenuation range, the control feedback loop of the pump laser is activated. When the target attenuation value is within the preset attenuation range, adjustment is made through the control feedback loop of the variable optical attenuator. Thus, in the entire loop control, the control feedback loop of the variable optical attenuator is used as much as possible to adjust the actual output optical power of the system. The control feedback loop of the pump laser is activated only when the variable optical attenuator cannot be adjusted. The activation frequency of the control feedback loop of the pump laser is minimized, so that the two feedback loops can cooperate with each other to adjust the actual output optical power of the system, further improving the stability of the actual output optical power of the system and eliminating noise interference caused by frequent changes in the magnitude of the pump light of the pump laser.

[0083] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A loop control system, characterized in that, include: Couplers, pump lasers, fiber amplifiers, variable optical attenuators, beam splitters, photodetectors, and loop controllers; The first input terminal of the coupler serves as the input terminal of the system and receives signal light. The second input terminal of the coupler is connected to the output terminal of the pump laser; The output of the coupler is connected to the input of the fiber optic amplifier, the output of the fiber optic amplifier is connected to the input of the variable optical attenuator, and the output of the variable optical attenuator is connected to the input of the beam splitter. The first output terminal of the beam splitter serves as the output terminal of the system, the second output terminal of the beam splitter is connected to the input terminal of the photodetector, the output terminal of the photodetector is connected to the input terminal of the loop controller, and the first control terminal of the loop controller is connected to the control terminal of the variable optical attenuator. The second control terminal of the loop controller is connected to the control terminal of the pump laser. The control feedback loop of the pump laser is activated when the variable optical attenuator cannot be adjusted. The variable optical attenuator cannot be adjusted when the target attenuation value of the variable optical attenuator is not within the preset attenuation range of the variable optical attenuator.

2. The loop control system according to claim 1, characterized in that, The loop controller includes: an analog-to-digital converter, a controller, an adder, a first integrator, a second integrator, a first digital-to-analog converter, and a second digital-to-analog converter; The controller is connected to the analog-to-digital converter, the adder, the first integrator, the second integrator, the first digital-to-analog converter, and the second digital-to-analog converter, respectively. The input terminal of the analog-to-digital converter serves as the input terminal of the loop controller, and the output terminal of the analog-to-digital converter is connected to the input terminal of the adder; The output of the adder is connected to the input of the first integrator and the input of the second integrator, respectively. The output of the first integrator is connected to the input of the first digital-to-analog converter, and the output of the first digital-to-analog converter is connected to the variable optical attenuator; the output of the second integrator is connected to the input of the second digital-to-analog converter, and the output of the second digital-to-analog converter is connected to the pump laser.

3. The loop control system according to any one of claims 1 to 2, characterized in that, The system also includes: an isolator; The isolator is positioned between the fiber amplifier and the variable optical attenuator.

4. The loop control system according to any one of claims 1 to 2, characterized in that, The coupler is an isolation coupler.

5. The loop control system according to any one of claims 1 to 2, characterized in that, The fiber amplifier is one of the following: erbium-doped fiber amplifier, praseodymium-doped fiber amplifier, or niobium-doped fiber amplifier.

6. A loop control method, characterized in that, A loop controller is applied in a loop control system; the loop control system further includes: a coupler, a pump laser, an fiber amplifier, a variable optical attenuator, a beam splitter, and a photodetector; the first input terminal of the coupler serves as the input terminal of the system and receives signal light; the second input terminal of the coupler is connected to the output terminal of the pump laser; the output terminal of the coupler is connected to the input terminal of the fiber amplifier, the output terminal of the fiber amplifier is connected to the input terminal of the variable optical attenuator, and the output terminal of the variable optical attenuator is connected to the input terminal of the beam splitter; the first output terminal of the beam splitter serves as the output terminal of the system, the second output terminal of the beam splitter is connected to the input terminal of the photodetector, the output terminal of the photodetector is connected to the input terminal of the loop controller, the first control terminal of the loop controller is connected to the control terminal of the variable optical attenuator, and the second control terminal of the loop controller is connected to the control terminal of the pump laser; the control feedback loop of the pump laser is activated when the variable optical attenuator cannot be adjusted, wherein the variable optical attenuator cannot be adjusted when the target attenuation value of the variable optical attenuator is not within the preset attenuation range of the variable optical attenuator; the method includes: The electrical signal output by the photodetector is acquired, and the actual output optical power of the system is determined based on the electrical signal. When the actual output optical power of the system does not match the preset output optical power of the system, the target attenuation value of the variable optical attenuator is obtained based on the actual output optical power of the system, the preset output optical power of the system, and the current attenuation value of the variable optical attenuator. The attenuation value of the variable optical attenuator is adjusted to the target attenuation value.

7. The loop control method according to claim 6, characterized in that, After acquiring the electrical signal output by the photodetector and determining the actual output optical power of the system based on the output electrical signal, the method further includes the pump laser adjustment step. The pump laser adjustment steps include: The actual output optical power of the fiber amplifier is obtained based on the actual output optical power of the system and the current attenuation value of the variable optical attenuator. When the actual output optical power of the fiber amplifier does not match the preset output optical power of the fiber amplifier, the target output current of the pump laser is obtained based on the actual output optical power of the fiber amplifier, the preset output optical power of the fiber amplifier, and the current output current of the pump laser. The output current of the pump laser is adjusted to the target output current.

8. The loop control method according to claim 7, characterized in that, After obtaining the target attenuation value of the variable optical attenuator based on the actual output optical power of the system, the preset output optical power of the system, and the current attenuation value of the variable optical attenuator, the process further includes: Determine whether the target attenuation value is within the preset attenuation range of the variable optical attenuator; If so, then perform the step of adjusting the attenuation value of the variable optical attenuator to the target attenuation value; If not, then perform the pump laser adjustment steps.

9. The loop control method according to any one of claims 6 to 8, characterized in that, The process of obtaining the target attenuation value of the variable optical attenuator based on the actual output optical power of the system, the preset output optical power of the system, and the current attenuation value of the variable optical attenuator includes: The adjustment value of the attenuation value of the variable optical attenuator is obtained based on the actual output optical power of the system and the preset output optical power of the system. The target attenuation value is obtained based on the current attenuation value of the variable optical attenuator and the adjustment value.

10. The loop control method according to any one of claims 6 to 8, characterized in that, Determining the actual output optical power of the system based on the electrical signal includes: The actual output optical power of the system is obtained based on the function between the actual output optical power of the system and the voltage of the electrical signal, which is preset in the system, and the voltage of the electrical signal.

11. The loop control method according to any one of claims 6 to 8, characterized in that, Adjusting the attenuation value of the variable optical attenuator to the target attenuation value includes: The target control voltage of the variable optical attenuator is obtained based on the target attenuation value; The control voltage of the variable optical attenuator is adjusted to the target control voltage, so that the attenuation value of the variable optical attenuator is adjusted to the target attenuation value.

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