Large-gain bidirectional amplification system and method based on unidirectional erbium-doped fiber amplifier

Abstract

The invention belongs to the technical field of optical fiber optical frequency transmission, and provides a large-gain bidirectional amplification system and method based on a unidirectional erbium-doped optical fiber amplifier, and the system comprises a first input unit, a second input unit, a forward amplification unit, a reverse amplification unit, and a frequency mixing compensation unit. The input end of the forward amplification unit is connected with the first input unit, the input end of the reverse amplification unit is connected with the second input unit, and the output ends of the forward amplification unit and the reverse amplification unit are jointly connected to the frequency mixing compensation unit; the forward amplification unit and the reverse amplification unit are respectively used for generating beat frequency signals, and the frequency mixing compensation unit is used for receiving the beat frequency signals and compensating the reverse amplification unit after frequency mixing. The gain of each amplifier is independently controlled, so that the self-excitation effect is avoided. In the scheme, the two amplifiers are independently controlled, so that the situation can be effectively avoided, and the stability and the gain performance of the whole amplification system are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber optical frequency transmission, and in particular relates to a large-gain bidirectional amplification system and method based on a unidirectional erbium-doped optical fiber amplifier. Background Art

[0002] Optical frequency standards play an important role in geodesy, satellite navigation, radio astronomy, dark matter detection and other fields. Optical fiber has the characteristics of low loss, large capacity and strong anti-interference ability, which ensures the stability of optical frequency signals. In long-distance optical fiber optical frequency transmission systems, as the optical fiber distance increases, the optical fiber loss also increases, resulting in the deterioration of the optical frequency signal signal-to-noise ratio and power reduction. The bidirectional erbium-doped fiber amplifier is limited by the self-excited effect, and the gain is generally controlled at 16dB-18dB, which can no longer meet the amplification requirements. In view of this situation, there are currently two main methods to compensate for optical fiber loss. One is to use optical fiber amplifiers such as fiber Raman amplifiers and fiber Brillouin amplifiers. Fiber Raman amplifiers have ultra-wide bandwidth and low noise figure, but small gain, and must be used in conjunction with erbium-doped fiber amplifiers EDFA (Erbium-Doped Fiber Amplifier) ​​to obtain high gain; fiber Brillouin amplifiers have high gain and high conversion efficiency, but will be affected by self-excited Brillouin scattering, which will degrade the performance of the amplifier and limit its gain. The other is to use an amplification system based on optical injection locking. Although a larger gain can be obtained, an additional laser is required, the injection locking process is also more complicated, and it is very sensitive to environmental changes.

[0003] At present, there is a technology that proposes to use a unidirectional erbium-doped fiber amplifier for bidirectional amplification, and use an optical phase-locked loop to lock the phase difference between two unidirectional erbium-doped fiber amplifiers, which significantly improves the gain of the amplification system. However, during the transmission process, the transmitted light is affected by the optical fiber link. When measuring the phase difference, the beat frequency signal is unstable and effective phase detection cannot be performed. Summary of the invention

[0004] The purpose of the present invention is to provide a high-gain bidirectional amplification system and method based on a unidirectional erbium-doped fiber amplifier to solve the problem that the transmitted light is affected by the optical fiber link during the transmission process of the prior art, and the beat frequency signal is unstable when the phase difference is measured.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a large-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier, characterized in that it comprises a first input unit, a second input unit, a forward amplification unit, a reverse amplification unit and a mixing compensation unit; the input end of the forward amplification unit is connected to the first input unit, the input end of the reverse amplification unit is connected to the second input unit, and the output ends of the forward amplification unit and the reverse amplification unit are commonly connected to the mixing compensation unit; The forward amplification unit and the reverse amplification unit are used to generate beat frequency signals respectively, and the mixing compensation unit is used to receive the beat frequency signal and compensate the reverse amplification unit after mixing.

[0006] Furthermore, the forward amplification unit includes a first optical coupler, a first acousto-optic modulator, a first optical circulator, a second optical circulator, a second optical coupler, a first unidirectional erbium-doped fiber amplifier and a fourth wavelength division multiplexer; the input end of the first optical coupler is connected to the first input unit, and the output end of the first optical coupler is divided into two paths, one path is connected to the second optical coupler through the first acousto-optic modulator; the other path is connected to the second optical coupler through the first optical circulator, the first unidirectional erbium-doped fiber amplifier and the second optical circulator in sequence, the second optical coupler is connected to the fourth wavelength division multiplexer, and the beat frequency signal is generated by the fourth wavelength division multiplexer.

[0007] Furthermore, the fourth wavelength division multiplexer is connected to a second photodetector for detecting the beat frequency signal.

[0008] Furthermore, the reverse amplification unit includes a second unidirectional erbium-doped fiber amplifier, a third wavelength division multiplexer and a second acousto-optic modulator; the input end of the second optical coupler is connected to the second input unit, and the output end of the second optical coupler is divided into two paths, one path is connected to the first optical coupler through the first acousto-optic modulator; the other path is connected to the first optical coupler in sequence through the second optical circulator, the second acousto-optic modulator, the second unidirectional erbium-doped fiber amplifier and the first optical circulator, the first optical coupler is connected to the third wavelength division multiplexer, and the beat frequency signal is generated through the third wavelength division multiplexer.

[0009] Furthermore, the third wavelength division multiplexer is connected to a first photodetector for detecting the beat frequency signal.

[0010] Furthermore, the mixing compensation unit includes a first bandpass filter, a second bandpass filter, a third bandpass filter, a first mixer, a second mixer and a proportional integral differential circuit; the input ends of the first bandpass filter and the second bandpass filter are respectively connected to the first photodetector and the second photodetector, the output ends of the first bandpass filter and the second bandpass filter are connected to the input end of the first mixer, the output end of the first mixer is connected to the input end of the second mixer through the third bandpass filter, the output end of the second mixer is connected to the proportional integral differential circuit, and the proportional integral differential circuit is connected to the second acousto-optic modulator.

[0011] Furthermore, the second mixer inputs a radio frequency reference signal.

[0012] Furthermore, the first input unit includes a first laser and a first wavelength division multiplexer; the first laser is connected to the input end of the first wavelength division multiplexer, and the output end of the first wavelength division multiplexer is connected to the first optical coupler; the first wavelength division multiplexer inputs the signal to be amplified.

[0013] Furthermore, the second input unit includes a second laser and a second wavelength division multiplexer; the second laser is connected to the input end of the second wavelength division multiplexer, and the output end of the second wavelength division multiplexer is connected to the second optical coupler; the second wavelength division multiplexer inputs the signal to be amplified.

[0014] In a second aspect, the present invention provides an amplification method of a high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier, comprising the following steps: The optical signal of the first input unit enters the forward amplification unit to generate an optical signal E2 and an optical signal E3, and the optical signal E2 and the optical signal E3 pass through the fourth wavelength division multiplexer to generate a beat frequency signal E4; The optical signal of the second input unit enters the reverse amplification unit to generate optical signals E5 and E6. The beat frequency signal generated by the optical signals E5 and E6 after passing through the third wavelength division multiplexer is E7. The beat frequency signals E4 and E7 are mixed and compensated by a frequency mixing unit to obtain an optical signal E8. The optical signal E8 is mixed and phase-detected with a radio frequency reference signal with a frequency of ω2 to obtain a phase difference signal ΦEDFA1-ΦEDFA2 between the first unidirectional erbium-doped fiber amplifier and the second unidirectional erbium-doped fiber amplifier. The phase difference signal is fed back to control the reverse amplification unit.

[0015] Compared with the prior art, the present invention has the following technical effects: The present invention realizes bidirectional amplification of optical signals by connecting a first unidirectional erbium-doped fiber amplifier and a second unidirectional erbium-doped fiber amplifier by using a first optical circulator and a second optical circulator. The gain of the first unidirectional erbium-doped fiber amplifier and the second unidirectional erbium-doped fiber amplifier can be independently controlled, thereby avoiding the self-excitation effect. In this solution, since the first unidirectional erbium-doped fiber amplifier and the second unidirectional erbium-doped fiber amplifier are independently controlled, this situation can be effectively avoided, thereby improving the stability and gain performance of the entire amplification system.

[0016] The present invention generates beat frequency signals E4 and E7 and uses a mixing compensation unit to detect the phase difference between the first unidirectional erbium-doped fiber amplifier and the second unidirectional erbium-doped fiber amplifier. The detection of the phase difference is achieved by using light of a different wavelength from the transmitted light as the measuring light, so the measuring light is not affected by the phase noise of the optical fiber link. This improves the signal-to-noise ratio of the detection signal and makes the phase discrimination process more stable.

[0017] The detected phase difference signal (ΦEDFA1-ΦEDFA2) is fed back to control the reverse amplification unit, especially by adjusting the second acousto-optic modulator to achieve phase compensation of the reverse amplification path. This feedback control mechanism helps to maintain the phase consistency between the first unidirectional erbium-doped fiber amplifier and the second unidirectional erbium-doped fiber amplifier, further improving the stability and performance of the amplification system.

[0018] Since the scheme can independently control the gain of the first unidirectional erbium-doped fiber amplifier and the second unidirectional erbium-doped fiber amplifier and effectively compensate for the phase difference, the number of amplification systems can be reduced, which reduces the complexity and cost of the system and improves the reliability and maintainability of the system.

[0019] The present invention uses measurement light of different wavelengths for phase difference detection, avoiding the influence of optical fiber link phase noise on the detection signal. This significantly improves the signal-to-noise ratio of the detection signal, allowing the system to more accurately detect and compensate for the phase difference. The proportional-integral-differential circuit in the mixing compensation unit can perform precise control and adjustment according to the phase difference signal, further improving the stability and response speed of the system.

[0020] The design of this technical solution is highly flexible and scalable. By adjusting the configuration of optical components and signal processing units, it can adapt to different optical signal amplification requirements and application scenarios.

[0021] In summary, this technical solution effectively solves the problems existing in the traditional bidirectional amplification system through a series of innovative designs and implementation methods, and improves the gain performance, stability and reliability of the amplification system. At the same time, this solution is also highly flexible and scalable, providing new ideas and development directions for future optical signal amplification technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a system structure diagram of the present invention.

[0023] in: The first optical coupler OC1, the first acousto-optic modulator AOM1, the first optical circulator CIR1, the second optical circulator CIR2, the second optical coupler OC2, the first unidirectional erbium-doped fiber amplifier EDFA1, the fourth wavelength division multiplexer WDM4, the first photodetector PD1, the second photodetector PD2, the second unidirectional erbium-doped fiber amplifier EDFA2, the third wavelength division multiplexer WDM3, the second acousto-optic modulator AOM2, the first bandpass filter BPF1, the second bandpass filter BPF2, the third bandpass filter BPF3, the first mixer MIX1, the second mixer MIX2, the proportional integral differential circuit PID, and the radio frequency reference signal RF. DETAILED DESCRIPTION

[0024] Explanation of relevant terms: OC: Optical Coupler is an optical device that realizes light splitting and light combining.

[0025] AOM: Acousto-optic modulator (AOM) is a high-speed optical modulation device based on the acousto-optic effect. It changes the refractive index of certain crystals or glass materials (photoelastic effect) through the oscillating mechanical strain of sound waves, thereby achieving modulation and power control of the laser beam.

[0026] WDM: Wavelength Division Multiplexing is a fiber optic communication technology device that allows multiple optical signals of different wavelengths to be transmitted simultaneously in the same optical fiber.

[0027] CIR: Circulator is an optical device with multiple ports in which optical signals can only be transmitted in one direction, that is, after being input from one port, they will be output from the next port in a specific order.

[0028] EDFA: Erbium-Doped Fiber Amplifier is an optical amplifier that uses erbium-doped fiber as the gain medium.

[0029] PD: Photodetector is a photoelectric device that converts light signals into electrical signals.

[0030] BPF: A band-pass filter is a filter that allows light signals within a specific frequency range to pass through, but blocks light signals of other frequencies from passing through.

[0031] MIX: A mixer is used to combine two or more signals into one output signal.

[0032] PID: Proportional Integration Differentiation is a control circuit.

[0033] RF: Radio Frequency is the abbreviation of a high-frequency alternating electromagnetic wave.

[0034] The present invention is further described below in conjunction with the accompanying drawings: Embodiment 1, the present invention provides a large-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier, comprising a first input unit, a second input unit, a forward amplification unit, a reverse amplification unit and a mixing compensation unit; the input end of the forward amplification unit is connected to the first input unit, the input end of the reverse amplification unit is connected to the second input unit, the output ends of the forward amplification unit and the reverse amplification unit are commonly connected to the mixing compensation unit, and the mixing compensation unit is connected to the reverse amplification unit; The forward amplification unit and the reverse amplification unit are used to generate beat frequency signals respectively, and the mixing compensation unit is used to receive the beat frequency signal and compensate the reverse amplification unit after mixing.

[0035] The design of the forward amplification unit and the reverse amplification unit realizes the bidirectional amplification of the optical signal. This design not only increases the transmission distance of the signal, but also enhances the signal strength.

[0036] The introduction of the mixing compensation unit provides the system with the ability to compensate for the phase difference and frequency offset that may occur during the amplification process, thereby ensuring the accuracy and stability of signal amplification.

[0037] The forward amplification unit and the reverse amplification unit generate beat frequency signals respectively, which are the basis for subsequent mixing compensation. The generation of beat frequency signals utilizes the characteristics of optical components, such as acousto-optic modulators and optical circulators, to achieve precise control of optical signals.

[0038] The mixing compensation unit receives and processes these beat frequency signals, extracts useful information through mixing and phase comparison, and uses it to compensate the reverse amplifier unit. This utilization method not only improves the utilization rate of the signal, but also enhances the adaptive ability of the system.

[0039] The mixer in the mixing compensation unit mixes the received beat frequency signal to generate a new signal. This process requires high-precision frequency and phase control to ensure that the mixed signal can accurately reflect the information of the original signal.

[0040] By comparing the mixed signal with the reference signal, the possible phase difference or frequency offset between the forward amplification unit and the reverse amplification unit can be obtained. Then, the reverse amplification unit can be accurately compensated using control algorithms such as the proportional integral differential circuit PID. This compensation mechanism not only improves the amplification quality of the signal, but also enhances the stability and reliability of the system.

[0041] In summary, the gain bidirectional amplification system based on the unidirectional erbium-doped fiber amplifier has a reasonable system architecture, accurate beat frequency signal generation and utilization, accurate mixing compensation mechanism and flexible scalability. These technical features make the system have broad application prospects and important technical value in the field of optical signal amplification. By continuously optimizing and improving the system, the transmission distance of the optical signal can be further increased, the signal strength can be enhanced, and the stability and reliability of the system can be improved.

[0042] Example 2, please refer to Figure 1 The present invention provides a high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier, specifically comprising: A first input unit, a second input unit, a forward amplifying unit, a reverse amplifying unit and a mixing compensation unit. The input end of the forward amplifying unit is connected to the first input unit, and the input end of the reverse amplifying unit is connected to the second input unit. The output ends of the forward amplifying unit and the reverse amplifying unit are both connected to the mixing compensation unit, and the mixing compensation unit is further connected to the reverse amplifying unit. The main functions of the forward amplifying unit and the reverse amplifying unit are to generate beat frequency signals respectively, which are then received and processed by the mixing compensation unit to accurately compensate the reverse amplifying unit.

[0043] The forward amplification unit and the reverse amplification unit generate beat frequency signals respectively, and the mixing compensation unit accurately processes these beat frequency signals to achieve accurate compensation for the reverse amplification unit. This not only improves the amplification quality of the signal, but also significantly enhances the stability and reliability of the system, providing strong support for long-distance, high-speed optical signal transmission.

[0044] In the specific structure of the forward amplification unit, key components such as the first optical coupler OC1, the first acousto-optic modulator AOM1, the first optical circulator CIR1, the second optical circulator CIR2, the second optical coupler OC2, the first unidirectional erbium-doped fiber amplifier EDFA1 and the fourth wavelength division multiplexer WDM4 are used. The input end of the first optical coupler OC1 is connected to the first input unit, and its output end is divided into two paths: one path is connected to the second optical coupler OC2 after the frequency shift ω1 through the first acousto-optic modulator AOM1; the other path passes through the first optical circulator CIR1, the first unidirectional erbium-doped fiber amplifier EDFA1 and the second optical circulator CIR2 in sequence, and finally connected to the second optical coupler OC2. The second optical coupler OC2 is then connected to the fourth wavelength division multiplexer WDM4, and a beat frequency signal is generated through the wavelength division multiplexer. In addition, the fourth wavelength division multiplexer WDM4 is also connected to a second photodetector PD2 for detecting the generated beat frequency signal.

[0045] In the forward amplification unit, the present invention forms an efficient optical signal amplification path. Through the frequency shifting effect of the first acousto-optic modulator AOM1 and the amplification effect of the first unidirectional erbium-doped fiber amplifier, the system can generate high-quality beat frequency signals. At the same time, the introduction of the fourth wavelength division multiplexer enables the beat frequency signal to be effectively extracted and separated. The setting of the second photodetector further ensures the accurate detection of the beat frequency signal and provides a reliable basis for subsequent mixing compensation. This series of designs not only improves the amplification efficiency of the forward amplification unit, but also ensures the quality and stability of the beat frequency signal.

[0046] In the reverse amplification unit, some components are shared with the forward amplification unit, including the first optical circulator CIR1, the second optical circulator CIR2, the first acousto-optic modulator AOM1, the first optical coupler OC1 and the second optical coupler OC2. The input end of the second optical coupler OC2 is connected to the second input unit, and its output end is also divided into two paths: one path is connected to the first optical coupler OC1 after the frequency shift ω1 through the first acousto-optic modulator AOM1; the other path passes through the second optical circulator CIR2, the second acousto-optic modulator AOM2 frequency shift ω2, the second unidirectional erbium-doped fiber amplifier EDFA2 and the first optical circulator CIR1 in sequence, and finally also connects to the first optical coupler OC1. The first optical coupler OC1 is then connected to the third wavelength division multiplexer WDM3, and another beat frequency signal is generated through the third wavelength division multiplexer WDM3. The third wavelength division multiplexer WDM3 is also connected to the first photodetector PD1 for detecting this beat frequency signal. The mixing compensation unit is responsible for receiving and processing the two beat frequency signals, and accurately compensates the reverse amplifier unit through a series of mixing, filtering, and proportional integral differential control processes. In addition, the second mixer MIX2 in the mixing compensation unit is also connected to the radio frequency reference signal RF, which is used to provide a reference frequency in the mixing process. In the first input unit and the second input unit, the first laser and the second laser are used as light sources, respectively, and are multiplexed with the signal to be amplified through the first wavelength division multiplexer WDM1 and the second wavelength division multiplexer WDM2 and then input into the system.

[0047] In the reverse amplification unit, the present invention realizes the optimal utilization of resources by sharing some components of the forward amplification unit. At the same time, by introducing new components such as the second unidirectional erbium-doped fiber amplifier, the second acousto-optic modulator and the third wavelength division multiplexer, a reverse amplification path independent of the forward amplification unit is constructed. This path can also generate a beat signal and accurately detect it through the first photodetector. As the core part of the system, the mixing compensation unit realizes accurate compensation of the reverse amplification unit by receiving and processing two beat signals. The present invention adopts the first bandpass filter BPF1, the second bandpass filter BPF2, the third bandpass filter BPF3, the first mixer MIX1, the second mixer MIX2 and the proportional integral differential circuit PID, which can effectively eliminate the phase difference and frequency offset and ensure that the output signal of the reverse amplification unit is consistent with the original signal. In addition, the introduction of the radio frequency reference signal provides a stable reference frequency for the mixing process, further improving the accuracy and stability of the compensation. Not only the amplification quality of the reverse amplification unit is improved, but also the adaptability and robustness of the entire system are significantly enhanced.

[0048] Embodiment 3, the present invention provides an amplification method of a large-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier, comprising the following steps: The optical signal of the first input unit enters the forward amplification unit, generating two optical signals, namely optical signal E2 and optical signal E3. The optical signals E2 and E3 pass through the fourth wavelength division multiplexer WDM4 to generate a beat frequency signal E4. The optical signal of the second input unit enters the reverse amplification unit, generating two optical signals, namely optical signal E5 and optical signal E6. The optical signals E5 and E6 generate a beat frequency signal E7 after passing through the third wavelength division multiplexer WDM3. The beat frequency signals E4 and E7 are mixed and compensated by a frequency mixing unit to obtain an optical signal E8. The optical signal E8 is mixed and phase-detected with a radio frequency reference signal with a frequency of ω2 to obtain a phase difference signal ΦEDFA1-ΦEDFA2 between the first unidirectional erbium-doped fiber amplifier EDFA1 and the second unidirectional erbium-doped fiber amplifier EDFA2. The phase difference signal is fed back to control the reverse amplification unit.

[0049] Take 1510nm laser as an example to amplify 1550nm laser.

[0050] The optical signal E1 of the first 1510nm laser is expressed as cos(ν0t+Φ0), enters the amplification system through the first wavelength division multiplexer WDM1, and is divided into two paths after passing through the first optical coupler OC1. One path is shifted by ω1 through the first acousto-optic modulator AOM1 and reaches the second optical coupler OC2. The optical signal E2 is expressed as cos[(ν0+ω1)t+Φ0]; the other path passes through the first unidirectional erbium-doped fiber amplifier EDFA1 and the second optical circulator CIR1 and reaches the second optical coupler OC2. The optical signal E3 is expressed as cos(ν0t+Φ0+ΦEDFA1), where ΦEDFA1 is the phase noise generated by the optical signal passing through the first unidirectional erbium-doped fiber amplifier EDFA1. The beat frequency signal E4 generated by the optical signals E2 and E3 after passing through the fourth wavelength division multiplexer WDM4 is expressed as cos(ω1t-ΦEDFA1), which is detected by the second photodetector PD2. Where: v0 is the initial frequency of the laser, t is the independent variable time, φ0 is the initial phase, and ω1 is the driving frequency of the AOM.

[0051] The optical signal E1 of the second 1510nm laser is expressed as cos(ν0t+Φ0), enters the amplification system in reverse from the second wavelength division multiplexer WDM2, and is divided into two paths after passing through the second optical coupler OC2. One path is shifted in frequency by ω1 through the first acousto-optic modulator AOM1 and reaches the first optical coupler OC1. The optical signal E5 is expressed as cos[(ν0+ω1)t+Φ0]; the other path is shifted in frequency by ω2 through the second optical circulator CIR2, the second unidirectional erbium-doped fiber amplifier EDFA2 and the first optical circulator CIR1 and reaches the first optical coupler OC1. The optical signal E6 is expressed as cos[(ν0+ω2)t+Φ0+ΦEDFA2], where ΦEDFA2 is the phase noise generated by the optical signal passing through the second unidirectional erbium-doped fiber amplifier EDFA2. After the optical signals E5 and E6 pass through the third wavelength division multiplexer WDM3, the beat signal E7 generated is expressed as cos[(ω1-ω2)t-ΦEDFA2] and detected by PD1. Among them: v0 is the initial frequency of the laser, t is the independent variable time, φ0 is the initial phase, ω1 and ω2 are the driving frequencies of the acousto-optic modulator.

[0052] The two electrical signals of beat frequency signal E4 and beat frequency signal E7 are filtered by the first bandpass filter BPF1 and the second bandpass filter BPF2, and then passed through the mixer to obtain E8=cos(ω2t-ΦEDFA1+ΦEDFA2). The signal is mixed and phase-detected with the RF reference signal with a frequency of ω2 to obtain the phase difference between EDFA1 and EDFA2, that is, ΦEDFA1-ΦEDFA2. The error signal is passed to the proportional integral differential circuit PID feedback control second acousto-optic modulator AOM2, and the 1550nm laser is compensated when passing through the second acousto-optic modulator AOM2.

[0053] The two 1510nm lasers are co-source lasers, and the transmission of the 1510nm laser in the amplification system does not affect the transmission of the 1550nm laser.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier, characterized in that: It includes a first input unit, a second input unit, a forward amplification unit, a reverse amplification unit and a mixing compensation unit; the input end of the forward amplification unit is connected to the first input unit, the input end of the reverse amplification unit is connected to the second input unit, and the output ends of the forward amplification unit and the reverse amplification unit are commonly connected to the mixing compensation unit; The forward amplification unit and the reverse amplification unit are used to generate beat frequency signals respectively, and the mixing compensation unit is used to receive the beat frequency signal and compensate the reverse amplification unit after mixing.

2. The high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier according to claim 1, characterized in that: The forward amplification unit comprises a first optical coupler, a first acousto-optic modulator, a first optical circulator, a second optical circulator, a second optical coupler, a first unidirectional erbium-doped fiber amplifier and a fourth wavelength division multiplexer; the input end of the first optical coupler is connected to the first input unit, and the output end of the first optical coupler is divided into two paths, one path is connected to the second optical coupler through the first acousto-optic modulator; the other path is connected to the second optical coupler through the first optical circulator, the first unidirectional erbium-doped fiber amplifier and the second optical circulator in sequence, the second optical coupler is connected to the fourth wavelength division multiplexer, and a beat frequency signal is generated through the fourth wavelength division multiplexer.

3. The high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier according to claim 2, characterized in that: The fourth wavelength division multiplexer is connected to a second photodetector for detecting the beat frequency signal.

4. The high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier according to claim 3, characterized in that: The reverse amplification unit includes a second unidirectional erbium-doped fiber amplifier, a third wavelength division multiplexer and a second acousto-optic modulator; the input end of the second optical coupler is connected to the second input unit, and the output end of the second optical coupler is divided into two paths, one of which is connected to the first optical coupler through the first acousto-optic modulator; the other path is connected to the first optical coupler through the second optical circulator, the second acousto-optic modulator, the second unidirectional erbium-doped fiber amplifier and the first optical circulator in sequence, the first optical coupler is connected to the third wavelength division multiplexer, and a beat frequency signal is generated through the third wavelength division multiplexer.

5. The high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier according to claim 4, characterized in that: The third wavelength division multiplexer is connected to the first photoelectric detector for detecting the beat frequency signal.

6. The high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier according to claim 5, characterized in that: The mixing compensation unit includes a first bandpass filter, a second bandpass filter, a third bandpass filter, a first mixer, a second mixer and a proportional integral differential circuit; the input ends of the first bandpass filter and the second bandpass filter are respectively connected to the first photodetector and the second photodetector, the output ends of the first bandpass filter and the second bandpass filter are connected to the input end of the first mixer, the output end of the first mixer is connected to the input end of the second mixer through the third bandpass filter, the output end of the second mixer is connected to the proportional integral differential circuit, and the proportional integral differential circuit is connected to the second acousto-optic modulator.

7. The high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier according to claim 6, characterized in that: The second mixer inputs a radio frequency reference signal.

8. The high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier according to claim 2, characterized in that: The first input unit includes a first laser and a first wavelength division multiplexer; the first laser is connected to the input end of the first wavelength division multiplexer, and the output end of the first wavelength division multiplexer is connected to the first optical coupler; the first wavelength division multiplexer inputs the signal to be amplified.

9. The high-gain bidirectional amplification system based on a unidirectional erbium-doped fiber amplifier according to claim 2, characterized in that: The second input unit includes a second laser and a second wavelength division multiplexer; the second laser is connected to the input end of the second wavelength division multiplexer, and the output end of the second wavelength division multiplexer is connected to the second optical coupler; the second wavelength division multiplexer inputs the signal to be amplified.

10. The amplification method of the high-gain bidirectional amplification system based on the unidirectional erbium-doped fiber amplifier according to any one of claims 1 to 9, characterized in that: The following steps are involved: The optical signal of the first input unit enters the forward amplification unit to generate an optical signal E2 and an optical signal E3, and the optical signal E2 and the optical signal E3 generate a beat frequency signal E4 after passing through the fourth wavelength division multiplexer; The optical signal of the second input unit enters the reverse amplification unit to generate optical signals E5 and E6, and the optical signals E5 and E6 generate beat frequency signal E7 after passing through the third wavelength division multiplexer; The beat frequency signals E4 and E7 are mixed and compensated by a frequency mixing unit to obtain an optical signal E8, and the optical signal E8 is mixed and phase-detected with a radio frequency reference signal with a frequency of ω2 to obtain a phase difference signal ΦEDFA1-ΦEDFA2 between the first unidirectional erbium-doped fiber amplifier and the second unidirectional erbium-doped fiber amplifier, and the phase difference signal is fed back to control the reverse amplification unit.

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