A dual-receiving and dual-transmitting optical fiber phase stabilization device based on a DFB analog direct modulation laser

Abstract

The application provides a double-receiving and double-transmitting optical fiber stable phase device based on a DFB analog direct modulation laser, belongs to the field of microwave photonics, and comprises a central station module, a remote station module and a module external device, the module external device is connected with the central station module and the remote station module respectively, and the central station module is connected with the remote station module through an optical fiber disc; the central station module serves as a transmitting side, actively detects and pre-compensates phase noise introduced by optical fiber transmission; the remote station module is used for receiving optical carrier radio frequency signals transmitted by the central station, restoring radio frequency signals through photoelectric conversion, and generating reverse optical carrier radio frequency signals to return to the central station by using a local feedback loop, so that an active closed loop is formed with the central station module, the signal transmission stability is improved, and a frequency signal phase-locked to the central station atomic clock is obtained. The application adopts the above device, solves the problems of high cost and complexity of a traditional external modulation link, poor direct modulation noise, difficulty in suppressing bidirectional disturbance by one-way compensation, low signal-to-noise ratio of multi-path stability and no redundancy.

Description

Technical Field

[0001] This invention relates to the field of microwave photonics, and in particular to a dual-receive, dual-transmit fiber phase-stabilized device based on a DFB analog direct-modulated laser. Background Technology

[0002] Optical fiber media is susceptible to interference from external factors such as ambient temperature fluctuations, mechanical vibrations, and external stresses. These factors simultaneously induce random fluctuations in the fiber's refractive index and physical length, continuously accumulating a large amount of phase noise along the link. Ultimately, this results in severe phase jitter and frequency stability degradation in the far-end output RF signal, failing to meet the stringent requirements of high-coherence systems for signal phase consistency. Therefore, the industry commonly employs a phase closed-loop compensation architecture to offset the phase drift introduced by the optical fiber.

[0003] Most current mainstream fiber-optic phase-stabilized systems rely on electro-optic external modulation optical paths to load radio frequency signals. While this approach offers advantages such as low signal distortion and wide operating bandwidth, it suffers from numerous optical path device layers, significant system integration challenges, and high hardware procurement and engineering deployment costs, making it unsuitable for miniaturized, low-power, and lightweight equipment applications. Distributed feedback (DFB) lasers, with their simplified structure, compact size, and direct modulation capabilities, are gradually gaining traction in phase-stabilized transmission research. Direct intensity modulation optical paths can significantly simplify the system architecture, but the DFB's analog direct modulation mode inevitably generates frequency chirp, nonlinear distortion, and optical power fluctuation noise, severely degrading the phase noise performance of fiber optic links. Furthermore, traditional unidirectional compensation loops have inherent limitations in suppressing disturbances during bidirectional transmission over long distances, restricting compensation accuracy and dynamic stability range.

[0004] To improve the phase stability performance of long links, the industry has developed dual-transmitter or dual-receiver multi-path calibration architectures, relying on cross-verification of multi-channel signals to improve phase error correction capabilities. However, most existing multi-path calibration solutions still rely on high-cost electro-optic external modulation light sources, and their overall cost and size advantages are not prominent. Moreover, there are many technical difficulties in key aspects such as multi-path RF frequency planning, multi-stage mixing link matching, loop delay suppression, and phase noise collaborative optimization. If the matching degree of optical path and RF link design is insufficient, it is easy to cause the signal-to-noise ratio of the beat frequency output signal to deteriorate and the closed-loop compensation bandwidth to narrow, directly reducing the long-term working stability of the entire phase stabilization system, making it difficult to meet the three core engineering requirements of high phase stability, low cost, and small integration. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-transmit, dual-receive fiber optic phase stabilization device based on DFB analog direct-modulated lasers. This addresses the problems of traditional externally modulated fiber optic phase stabilization systems, such as complex structure and high cost, severe noise degradation in ordinary DFB direct-modulated links, difficulty in suppressing bidirectional phase disturbances in long-distance fibers with unidirectional compensation architectures, poor beat frequency signal-to-noise ratio and low reliability due to lack of redundancy in existing multi-channel phase stabilization schemes, and the inability to simultaneously achieve small size, low cost, and ultra-high long-term frequency stability. This invention uses two DFB analog direct-modulated lasers as light sources for dual emission and employs a proportional-integral-derivative PID algorithm for measuring and pre-compensating for transmission delay variations, achieving 10... -19 Frequency stability over 10000 seconds.

[0006] To achieve the above objectives, this invention provides a dual-transmit / receive fiber optic phase-stabilization device based on a DFB analog direct-modulated laser, comprising a central station module, a remote station module, and external devices. The external devices are connected to the central station module and the remote station module, respectively. The central station module and the remote station module are connected via an optical fiber disk. The central station module, acting as the transmitter, actively detects and pre-compensates for phase noise introduced by fiber optic transmission. The remote station module, also acting as the transmitter, forms a loop with the central station module to improve signal transmission stability, thereby obtaining a frequency signal whose phase is locked to a reference frequency source. The central station module includes a third bandpass filter BPF3, a first phase-locked medium oscillator DRO1, a second mixer, a first temperature-controlled voltage-controlled oscillator OCXO1, a second phase-locked medium oscillator DRO2, a first photodetector PD1, a first DFB analog direct-modulated laser DML1, a first fiber polarization scrambler Ps1, a first circulator, and a first optical filter OF1. The output of the third bandpass filter BPF3 is connected to the input of the first phase-locked medium oscillator DRO1, and the output of the first phase-locked medium oscillator DRO1 is connected to the LO terminal of the second mixer. The IF output signal of the second mixer calculates the transmission delay using a PID algorithm, and inputs the transmission delay into the first isothermal voltage-controlled oscillator OCXO1. The output of the first isothermal voltage-controlled oscillator OCXO1 is sequentially connected to the second phase-locked medium oscillator DRO2, the first DFB analog direct-modulation laser DML1, the first fiber polarization scrambler Ps1, and the first circulator. The first circulator is connected to the other end of the fiber optic disk and the input of the first optical filter OF1. The output of the first optical filter OF1 is connected to the input of the first photodetector PD1. The output of the first photodetector PD1 is connected to the RF terminal of the second mixer. Port 1 of the first circulator is connected to the output of the first fiber polarization scrambler Ps1, port 2 of the first circulator is connected to the other end of the G.652 fiber optic disk, and port 3 of the first circulator is connected to the input of the first optical filter OF1. The remote station module includes a second circulator, a second optical filter OF2, a second photodetector PD2, a third mixer, a second temperature-controlled voltage-controlled oscillator OCXO2, a third power divider PS3, a third phase-locked dielectric oscillator DRO3, a fourth power divider PS4, a fifth bandpass filter BPF5, a second DFB analog direct-modulated laser DML2, a second fiber polarization scrambler Ps2, a fourth bandpass filter BPF4, a second power divider PS2, a sixth bandpass filter BPF6, and a fourth phase-locked dielectric oscillator DRO4. Port 2 of the second circulator is connected to one end of a G.652 fiber optic cable, and port 3 of the second circulator is connected to the input of the second optical filter OF2. The output of the second optical filter OF2 is connected to the input of the second photodetector PD2, and the output of the second photodetector PD2 is connected to the RF terminal of the third mixer. The LO terminal of the third mixer is connected to the output terminal of the fourth bandpass filter BPF4, the input terminal of the fourth bandpass filter BPF4 is connected to port 1 of the fourth power divider PS4, the port 2 of the fourth power divider PS4 is connected to the input terminal of the fifth bandpass filter BPF5, the output terminal of the fifth bandpass filter BPF5 is connected in sequence to the second DFB analog direct-modulated laser DML2 and the second fiber polarizer Ps2, and the output terminal of the second fiber polarizer Ps2 is connected to port 1 of the second circulator. The S port of the fourth power divider PS4 is connected to the output of the third phase-locked dielectric oscillator DRO3. The input of the third phase-locked dielectric oscillator DRO3 is connected to the 2 port of the third power divider PS3. The 1 port of the third power divider PS3 is connected to the S port of the second power divider PS2. The 1 port of the second power divider PS2 is connected to the input of the sixth bandpass filter BPF6. The 2 port of the second power divider PS2 is connected to the input of the fourth phase-locked dielectric oscillator DRO4. The S port of the third power divider PS3 is connected to the output of the second isothermal voltage-controlled oscillator OCXO2. The signal output from the IF port of the third mixer is calculated by a PID algorithm and input into the second isothermal voltage-controlled oscillator OCXO2. The sixth bandpass filter BPF6 is connected to the RF port of the first mixer.

[0007] Preferably, the external components of the module include a rubidium atomic clock, a first bandpass filter BPF1, a first power divider PS1, a second bandpass filter BPF2, a first mixer, a low-pass filter LPF, a digital multimeter, and a computer. The rubidium atomic clock is connected to the input terminal of the first bandpass filter BPF1. The output terminal of the first bandpass filter BPF1 is connected to the S terminal of the first power divider PS1. The I terminal of the first power divider PS1 is connected to the input terminal of the second bandpass filter BPF2. The output terminal of the second bandpass filter BPF2 is connected to the LO terminal of the first mixer. The IF terminal of the first mixer is connected to the input terminal of the low-pass filter LPF. The output terminal of the low-pass filter LPF is connected to the digital multimeter and the computer in sequence. The RF terminal of the first mixer is connected to the output terminal of the remote station module. The input terminal of the remote station module is connected to one end of the fiber optic tray. The other end of the fiber optic tray is connected to the output terminal of the central station module. The input terminal of the central station module is connected to the II terminal of the first power divider PS1 through a third bandpass filter BPF3.

[0008] Preferably, the fiber optic cable is of model G.652 with a link loss of <11dB; The rubidium atomic clock outputs a 100MHz signal with an output power of 9~13dBm and a stability of <10-14 / s. The first bandpass filter BPF1 and the second bandpass filter BPF2 operate at frequencies of 95~105MHz, have a filtering bandwidth of <10MHz, and an insertion loss of <5dB. The first power divider PS1 has an allowable bandwidth of 2~500MHz and an insertion loss of <1.5dB; The operating bandwidth of the LO and RF terminals of the first mixer is 0.5-500MHz, the operating bandwidth of the IF terminal is DC-500MHz, and the frequency conversion loss is ≤8dB. The low-pass filter LPF operates at a frequency ≤1MHz and has an isolation of <40dB. The noise floor of the digital multimeter is ≤100mV, 7 1 / 2 Measurement accuracy.

[0009] Preferably, the insertion loss of the first circulator is <3dB, the operating wavelength is C-band, and the isolation between the ports of the circulator is >60dB; The third bandpass filter BPF3 operates at a frequency of 95~105MHz, has a filtering bandwidth of <10MHz, and an insertion loss of <5dB. The signal output power of the first phase-locked dielectric oscillator DRO1 and the second phase-locked dielectric oscillator DRO2 are both ≥13dBm, and the phase noise is ≤-113dBc / Hz@1KHz; The signal output power of the first temperature-controlled voltage oscillator OCXO1 is ≥15dBm and the phase noise is ≤-110dBc@1KHz; The first DFB analog direct-modulated laser DML1 has a working wavelength of 1550nm, a maximum output power of ≤12dBm, a modulation bandwidth of ≤18GHz, a slope efficiency of >0.14mW / mA, a linewidth of <10MHz, and a relative intensity noise of <-145dB / Hz; The first fiber polarization scrambler Ps1 operates at a wavelength of 1260-1650nm, with an insertion loss of <0.5dB and a return loss of >65dB. The first optical filter OF1 has an operating wavelength of 1550.116nm, an operating bandwidth of <0.1nm, and an insertion loss of ≤0.8dB. The first photodetector PD1 operates in the C-band with a bandwidth of ≥10GHz; The second mixer has a working bandwidth of 7-34GHz for both the LO and RF terminals, a working bandwidth of DC-8GHz for the IF terminal, and a conversion loss of ≤15dB.

[0010] Preferably, the insertion loss of the second circulator is <3dB, the operating wavelength is C-band, and the isolation between the ports of the circulator is >60dB; The second DFB analog direct-modulated laser DML2 has a working wavelength of 1550.8nm, a maximum output power of ≤13dBm, a modulation bandwidth of ≤19GHz, a slope efficiency of >0.14mW / mA, a linewidth of <2MHz, and a relative intensity noise of <-150dB / Hz; The second fiber polarization scrambler Ps2 operates at a wavelength of 1260-1650nm, with an insertion loss of <0.5dB and a return loss of >65dB. The second optical filter OF2 has an operating wavelength of 1550.918nm, an operating bandwidth of <0.1nm, and an insertion loss of ≤0.8dB.

[0011] Preferably, the signal output power of the third phase-locked dielectric oscillator DRO3 and the fourth phase-locked dielectric oscillator DRO4 are both ≥13dBm and the phase noise is ≤-113dBc / Hz@1KHz; The signal output power of the second constant temperature voltage-controlled oscillator OCXO2 is ≥15dBm and the phase noise is ≤-110dBc@1KHz; The fourth bandpass filter BPF4 and the fifth bandpass filter BPF5 operate at frequencies of 8.9~9.1GHz, with a filtering bandwidth of <200MHz and an insertion loss of <3dB; the sixth bandpass filter BPF6 operates at frequencies of 95~105MHz, with a filtering bandwidth of <10MHz and an insertion loss of <5dB. The second power divider PS2 and the third power divider PS3 have an allowable bandwidth of 2~500MHz and an insertion loss of <1.5dB; the fourth power divider PS4 has an allowable bandwidth of 7~12.4GHz and an insertion loss of <1dB.

[0012] Preferably, the operating bandwidth of the LO and RF terminals of the third mixer is 7-34GHz, the operating bandwidth of the IF terminal is DC-8GHz, and the frequency conversion loss is ≤15dB. The second photodetector PD2 operates in the C-band with a bandwidth of ≥10GHz.

[0013] Therefore, the present invention employs the above-mentioned dual-receive, dual-transmit fiber phase-stabilizing device based on a DFB analog direct-modulated laser, and the technical effects are as follows: 1. This invention uses a DFB laser for direct modulation, which significantly simplifies the system structure and reduces the number of components and cost compared to the traditional external modulation structure. At the same time, by optimizing frequency planning and link design, it effectively suppresses the chirp and nonlinear effects introduced by direct modulation, resulting in a significant improvement in the radio frequency phase noise after transmission.

[0014] 2. This invention achieves bidirectional, dual-path mutual calibration and compensation of the link by setting up dual-channel transmission and dual-channel reception structures at the central station and remote station respectively, so that the beat frequency signal has a higher signal-to-noise ratio and more stable phase characteristics, thereby enhancing the accuracy of error detection and compensation in the stable phase loop.

[0015] 3. By rationally configuring the mixing relationship between the LO and RF signals and introducing multi-stage bandpass and low-pass filtering modules, this invention effectively suppresses crosstalk, side lobes, and unnecessary harmonic components, making the final intermediate frequency beat frequency signal purer and improving the locking accuracy and stability of the phase-stable loop.

[0016] 4. This invention incorporates phase feedback and PID control modules at both the central station and remote stations, and utilizes dual-link feedback information for comprehensive compensation. This significantly reduces fiber optic phase drift caused by environmental disturbances (sudden temperature changes, stress variations, etc.), enabling the system to maintain 10 GHz even during long-distance transmission. -19 Frequency stability over 10000 seconds. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a dual-receiver dual-transmit fiber phase-stabilizing device based on a DFB analog direct-modulated laser according to the present invention; Figure 2 This is a frequency stability test curve of a dual-receiver dual-transmit fiber optic phase-stable transmission device based on a DFB analog direct-modulated laser according to the present invention. Figure 3The phase stability curves of the comparison device using a two-stage DFB analog direct-modulated laser as a single light source are shown. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0020] Example 1 like Figure 1 As shown, this invention provides a dual-transmit, dual-receive fiber optic phase-stabilized device based on a DFB analog direct-modulated laser, comprising a central station module, a remote station module, and external devices. The external devices are connected to both the central station module and the remote station module, which are connected via an optical fiber disk. The central station module, acting as the transmitter, actively detects and pre-compensates for phase noise introduced by fiber optic transmission. The remote station module, also acting as the transmitter, forms a loop with the central station module to improve signal transmission stability, obtaining a frequency signal phase-locked to a reference frequency source. This fiber optic phase-stabilized transmission device is smaller in size and consumes less power.

[0021] External components include a rubidium atomic clock, a first bandpass filter (BPF1), a first power divider (PS1), a second bandpass filter (BPF2), a first mixer, a low-pass filter (LPF), a digital multimeter, and a computer. The rubidium atomic clock is connected to the input of the first bandpass filter (BPF1). The output of the first bandpass filter (BPF1) is connected to the source (S) terminal of the first power divider (PS1). The output (1) terminal of the first power divider (PS1) is connected to the input of the second bandpass filter (BPF2). The output of the second bandpass filter (BPF2) is connected to the source (LO) terminal of the first mixer. The input (IF) terminal of the first mixer is connected to the input of the low-pass filter (LPF). The output of the low-pass filter (LPF) is connected to the digital multimeter and the computer. The RF terminal of the first mixer is connected to the output of the remote station module. The input of the remote station module is connected to one end of the fiber optic cable, and the other end of the fiber optic cable is connected to the output of the central station module. The input of the central station module is connected to the source (2) terminal of the first power divider (PS1) via a third bandpass filter (BPF3).

[0022] The 100MHz reference frequency output from the rubidium atomic clock undergoes multi-stage filtering and power distribution. One path is connected to a mixer as a local phase detection reference (LO), while the other supplies the central station's RF link, achieving a unified reference source across the entire system and fundamentally avoiding the inherent phase deviation introduced by multiple frequency sources. The RF signal transmitted from the remote end is fed into the mixer's RF port and undergoes beat frequency processing with the reference LO. A low-pass filter then extracts the low-frequency DC error signal carrying only phase difference information, effectively filtering out RF harmonics and spurious crosstalk. This solves the problems of low signal-to-noise ratio and excessive noise interference in the error signal found in traditional solutions. Subsequently, a digital multimeter and computer are used to accurately acquire the error voltage, precisely quantifying the real-time phase fluctuation of the fiber optic link. This provides reliable numerical input for the PID compensation algorithm, significantly improving the quantization accuracy of end-to-end delay compensation.

[0023] In this invention, the fiber optic disk is model G.652, with a link loss <11dB; the rubidium atomic clock outputs a 100MHz signal with an output power of 9~13dBm and a stability of <10-14 / s; the first bandpass filter BPF1 and the second bandpass filter BPF2 operate at frequencies of 95~105MHz, with a filtering bandwidth <10MHz and an insertion loss <5dB; the first power divider PS1 has an allowable bandwidth of 2~500MHz and an insertion loss <1.5dB; the first mixer's LO and RF terminals both operate at bandwidths of 0.5-500MHz, and the IF terminal operates at a bandwidth of DC-500MHz, with a conversion loss ≤8dB; the low-pass filter LPF operates at a frequency ≤1MHz and has an isolation of <40dB; the digital multimeter has a noise floor ≤100mV. 1 / 2 Measurement accuracy.

[0024] This invention utilizes G.652 standard single-mode fiber adapted to the 1550nm communication band, strictly controlling the total loss of a 55km long-distance link to within 11dB. This ensures sufficient optical power for both round-trip optical signals, completely avoiding problems such as photodetector saturation and signal demodulation failure caused by insufficient optical power in traditional long-fiber links. A second stability better than 10 is selected. -14 The rubidium atomic clock provides an ultra-high purity frequency reference for the entire system, reducing the system's inherent phase noise from the source and effectively compensating for the inherent deficiency of long-term stability in ordinary crystal oscillators. The system front-end is equipped with a 100MHz narrowband bandpass filter, which can deeply suppress reference signal harmonics and external RF interference. Combined with a low insertion loss power divider to reduce power loss in the reference link, it ensures that both branch reference signals have sufficient output power. The back-end uses a high-isolation low-frequency low-pass filter to completely block high-frequency RF components, retaining only the DC component carrying phase difference information. This, combined with a high-precision 7.5-digit digital multimeter to reduce acquisition noise, allows even extremely small phase fluctuations to be accurately captured, significantly improving the phase detection sensitivity of the entire link.

[0025] The central station module includes a third bandpass filter BPF3, a first phase-locked medium oscillator DRO1, a second mixer, a first temperature-controlled voltage-controlled oscillator OCXO1, a second phase-locked medium oscillator DRO2, a first photodetector PD1, a first DFB analog direct-modulated laser DML1, a first fiber polarizer Ps1, a first circulator, and a first optical filter OF1.

[0026] The output of the third bandpass filter BPF3 is connected to the input of the first phase-locked dielectric oscillator DRO1. The output of the first phase-locked dielectric oscillator DRO1 is connected to the LO terminal of the second mixer. The output signal of the second mixer's IF terminal calculates the transmission delay using a PID algorithm and inputs the transmission delay to the first isothermal voltage-controlled oscillator OCXO1. The output of the first isothermal voltage-controlled oscillator OCXO1 is connected in sequence to the second phase-locked dielectric oscillator DRO2, the first DFB analog direct-modulated laser DML1, the first fiber polarizer Ps1, and the first circulator. The first circulator is connected to the other end of the fiber optic disk and the input of the first optical filter OF1. The output of the first optical filter OF1 is connected to the input of the first photodetector PD1. The output of the first photodetector PD1 is connected to the RF terminal of the second mixer.

[0027] The system upconverts the reference frequency to the microwave band via DRO, precisely matching the modulation bandwidth of the DFB directly modulated laser. This fundamentally solves the technical pain points of limited bandwidth and severe nonlinear distortion when directly modulating 100MHz low-frequency signals. The central station collects the round-trip reflected light signals of the fiber optic link through a local photodetector PD1, mixes them with the local microwave LO, demodulates the total time delay error of the round-trip link, and then uses a PID algorithm to control the voltage control end of the OCXO in real time to achieve positive phase pre-compensation, thus offsetting the phase drift caused by environmental influences on the fiber optic link in advance. At the optical path level, a closed-loop architecture of "laser-polarizer-circulator-transmission fiber-reflected light filtering and demodulation" is adopted. This not only realizes single-port fiber transceiver integration, greatly simplifying the complexity of optical path cabling, but also establishes a local self-calibration channel at the central station, significantly improving the real-time response capability of the entire link time delay compensation.

[0028] Port 1 of the first circulator is connected to the output of the first fiber polarization scrambler Ps1, port 2 of the first circulator is connected to the other end of the G.652 fiber optic disk, and port 3 of the first circulator is connected to the input of the first optical filter OF1. The insertion loss of the first circulator is <3dB, the operating wavelength is C-band, and the isolation between the ports of the circulator is >60dB; the operating frequency of the third bandpass filter BPF3 is 95~105MHz, the filtering bandwidth is <10MHz, and the insertion loss is <5dB; the signal output power of the first phase-locked dielectric oscillator DRO1 and the second phase-locked dielectric oscillator DRO2 are both ≥13dBm, and the phase noise is ≤-113dBc / Hz@1KHz; the signal output power of the first temperature-controlled voltage-controlled oscillator OCXO1 is ≥15dBm, and the phase noise is ≤-110dBc@1KHz; the operating wavelength of the first DFB analog direct-modulated laser DML1 is 1550nm, and the maximum output power is ≤ The first optical fiber polarizer Ps1 operates at a wavelength of 1260-1650nm, with an insertion loss of <0.5dB and a return loss of >65dB. The first optical filter OF1 operates at a wavelength of 1550.116nm, with an insertion loss of <0.1nm and an insertion loss of ≤0.8dB. The first photodetector PD1 operates at a wavelength in the C-band and has an insertion loss of ≥10GHz. The second mixer has an operating bandwidth of 7-34GHz at both the LO and RF ends, and a DC-8GHz operating bandwidth at the IF end, with a conversion loss of ≤15dB.

[0029] The three-port circulator provides deep physical isolation between the transmitted light and the round-trip reflected light. Its ultra-high port isolation of over 60dB completely blocks the transmitted light from directly interfering with the receiving demodulation path. This eliminates self-excitation interference caused by port leakage in traditional dual-transmit / receive architectures and effectively compensates for the inherent defect of severe crosstalk in ordinary couplers. The entire system operates at a C-band wavelength, precisely matched to the 1550nm output band of the DFB laser. The low insertion loss throughout ensures that the power of both the forward transmitted and reverse returned light does not significantly decrease, guaranteeing the demodulation signal-to-noise ratio of the photodetector from an optical power perspective. Simultaneously, leveraging the low phase noise characteristics of the DRO, the inherent noise of the microwave modulation signal is reduced. Combined with the temperature-controlled design of the OCXO, the temperature drift of the local oscillator is suppressed, further reducing the overall system phase noise level from the RF local oscillator perspective. The central station DML1 uses a 1550nm independent wavelength, narrow linewidth, and low relative intensity noise direct-modulated laser, forming a dual-wavelength configuration with another wavelength laser at the remote station. This fundamentally avoids coherent Rayleigh scattering noise interference in bidirectional optical signals and improves the link performance degradation caused by the inherent chirp and nonlinear distortion of DFB direct modulation. The fiber polarization scrambler configured in the optical path can disrupt the polarization state of the optical signal across the entire domain, significantly reducing the impact of fiber polarization mode dispersion on the demodulation phase and solving the phase jump problem caused by random polarization jitter during long-distance fiber transmission. The 0.1nm ultra-narrowband optical filter at the end only filters the reflected light from the central station itself, accurately filtering out stray light of different wavelengths transmitted back from the remote station, realizing the split demodulation of dual-optical-path signals. It can clearly distinguish the phase error of bidirectional transmission and provides core support for the dual-receive and dual-transmit cross-calibration function.

[0030] The isolation of >60dB between the ports of the first circulator is set to avoid port leakage caused by dual-transmit and dual-receiver transmission through the circulator in the fiber optic link. The operating wavelength of the first DFB analog direct-tuned laser DML1 is set to 1550nm, which differs from that of the second DFB analog direct-tuned laser DML2, in order to reduce the impact of coherent Rayleigh noise. The first fiber polarizer Ps1 is set to reduce the sensitivity to polarization mode dispersion in the fiber by rapidly disrupting the polarization state of the input light.

[0031] The mid-to-long-range station module includes a second circulator, a second optical filter OF2, a second photodetector PD2, a third mixer, a second temperature-controlled voltage-controlled oscillator OCXO2, a third power divider PS3, a third phase-locked dielectric oscillator DRO3, a fourth power divider PS4, a fifth bandpass filter BPF5, a second DFB analog direct-modulated laser DML2, a second fiber polarizer Ps2, a fourth bandpass filter BPF4, a second power divider PS2, a sixth bandpass filter BPF6, and a fourth phase-locked dielectric oscillator DRO4.

[0032] Port 2 of the second circulator is connected to one end of the G.652 fiber optic disc. Port 3 of the second circulator is connected to the input of the second optical filter OF2. The output of the second optical filter OF2 is connected to the input of the second photodetector PD2. The output of the second photodetector PD2 is connected to the RF terminal of the third mixer. The LO terminal of the third mixer is connected to the output of the fourth bandpass filter BPF4. The input of the fourth bandpass filter BPF4 is connected to port 1 of the fourth power divider PS4. Port 2 of the fourth power divider PS4 is connected to the input of the fifth bandpass filter BPF5. The output of the fifth bandpass filter BPF5 is sequentially connected to the second DFB analog direct-modulated laser DML2 and the second fiber polarizer Ps2. The output of the second fiber polarizer Ps2 is connected to the second circulator 1. Port connections: The S port of the fourth power divider PS4 is connected to the output of the third phase-locked dielectric oscillator DRO3; the input of the third phase-locked dielectric oscillator DRO3 is connected to port 2 of the third power divider PS3; port 1 of the third power divider PS3 is connected to the S port of the second power divider PS2; port 1 of the second power divider PS2 is connected to the input of the sixth bandpass filter BPF6; port 2 of the second power divider PS2 is connected to the input of the fourth phase-locked dielectric oscillator DRO4; the S port of the third power divider PS3 is connected to the output of the second isothermal voltage-controlled oscillator OCXO2; the signal output from the IF terminal of the third mixer is calculated by a PID algorithm and input into the second isothermal voltage-controlled oscillator OCXO2; the sixth bandpass filter BPF6 is connected to the RF terminal of the first mixer.

[0033] The remote station is equipped with an active photoelectric conversion and local signal recovery loop to provide a reverse transmission reference signal for the central station's closed-loop compensation and improve the quality of the remote output signal. The remote station sends the demodulated phase error signal to a local PID module, which controls the local OCXO in real time to complete secondary phase compensation on the remote side. Through the dual compensation mechanism of the central and remote stations, the phase accumulation drift of long-distance optical fibers caused by environmental factors such as temperature and mechanical stress is significantly reduced. One microwave signal output from the remote station drives a local DFB laser to generate a reverse return optical signal sent to the central station for secondary phase detection. Another microwave signal is directly supplied to external users as a high-precision stable phase output, simultaneously achieving both stable phase signal return and high-precision frequency output functions under the same hardware architecture. Simultaneously, the high-isolation three-port circulator configured in the remote station achieves physical isolation between the remote received light and the reverse emitted light, completely avoiding crosstalk issues within the remote optical path and fully ensuring the purity of the PD2 demodulated signal from the remote station.

[0034] The second circulator has an insertion loss of <3dB, operates in the C-band, and has an isolation of >60dB between its ports; the second DFB analog direct-modulated laser DML2 operates at a wavelength of 1550.8nm, has a maximum output power of ≤13dBm, a modulation bandwidth of ≤19GHz, a slope efficiency of >0.14mW / mA, a linewidth of <2MHz, and a relative intensity noise of <-150dB / Hz; the second fiber polarization scrambler Ps2 operates at a wavelength of 1260-1650nm, has an insertion loss of <0.5dB, and a return loss of >65dB; the second optical filter OF2 operates at a wavelength of 1550.918nm, has a bandwidth of <0.1nm, and an insertion loss of ≤0.8dB.

[0035] DML2 operates at a completely different frequency (1550.8nm) from the central station DML1, paired with a narrowband optical filter corresponding to the central station's 1550.918nm wavelength. This allows for precise separation of the central station's forward incident light from the remote station's reverse emitted light, deeply suppressing coherent interference and coherent Rayleigh scattering of bidirectional optical signals, thus fundamentally solving the link signal-to-noise ratio degradation problem caused by dual-wavelength transmission. DML2 uses devices with narrower linewidths and lower relative intensity noise, further optimizing the noise floor performance of the reverse return optical link. Simultaneously, the fiber polarizer configured at the remote station synchronously suppresses polarization mode dispersion, forming a completely symmetrical anti-polarization interference design with the central station's optical path, significantly improving phase stability under long-distance transmission. The 0.1nm ultra-narrowband optical filter at the link end only allows the central station's incident light to enter PD2 for demodulation, completely filtering out crosstalk from the remote station's own reverse emitted light, achieving complete optical splitting isolation between the remote receiving and transmitting optical paths, further ensuring the purity of the demodulated signal.

[0036] The signal output power of the third phase-locked dielectric oscillator (DRO3) and the fourth phase-locked dielectric oscillator (DRO4) are both ≥13dBm, and the phase noise is ≤-113dBc / Hz@1KHz; the signal output power of the second isothermal voltage-controlled oscillator (OCXO2) is ≥15dBm, and the phase noise is ≤-110dBc@1KHz; the operating frequency of the fourth bandpass filter (BPF4) and the fifth bandpass filter (BPF5) is 8.9~9.1GHz, the filtering bandwidth is <200MHz, and the insertion loss is <3dB; the operating frequency of the sixth bandpass filter (BPF6) is 95~105MHz, the filtering bandwidth is <10MHz, and the insertion loss is <5dB; the allowable bandwidth of the second power divider (PS2) and the third power divider (PS3) is 2~500MHz, and the insertion loss is <1.5dB; the allowable bandwidth of the fourth power divider (PS4) is 7~12.4GHz, and the insertion loss is <1dB.

[0037] The remote station is configured with dual DROs to construct two co-source low-phase-noise microwave RF links. One link serves as the local phase-detection reference (LO), while the other directly drives the DFB laser to complete the reverse optical signal modulation. The co-source nature of the two signals ensures low noise throughout the remote RF link, preventing the introduction of additional random phase disturbances during transmission. A 9GHz narrowband microwave filter within the link effectively filters out harmonics and various spurious interferences from the microwave signal. Combined with a low-loss millimeter-wave power divider, it ensures uniform microwave power distribution and sufficient output power, precisely matching the 18-19GHz modulation bandwidth requirements of the DFB laser and preventing signal distortion during modulation. A sixth-stage bandpass filter further refines the 100MHz reference signal recovered from the remote link before sending it back to the central station's master phase-detection mixer, forming a closed-loop error acquisition path covering the entire link. This ultimately enables bidirectional joint phase calibration between the central and remote stations.

[0038] The third mixer has a working bandwidth of 7-34GHz at both the LO and RF ends, and a working bandwidth of DC-8GHz at the IF end, with a conversion loss ≤15dB. The second photodetector PD2 operates in the C-band with a working bandwidth ≥10GHz. The second DFB analog direct-modulated laser DML2 is configured to comprehensively compensate for environmental disturbances (such as sudden temperature changes and stress variations) through dual-link feedback information, significantly reducing fiber phase drift and ensuring high stability of the system during long-distance transmission.

[0039] This system uses a 7~34GHz ultra-wideband mixer, which can completely cover all microwave modulation frequency bands across the entire link. Its DC intermediate frequency bandwidth can extract the error voltage carrying phase difference information without distortion, perfectly matching the high-precision acquisition requirements of the PID algorithm for low-speed compensation signals, and avoiding the low-frequency phase information loss problem caused by narrowband mixers. Simultaneously, a large-bandwidth photodetector above 10GHz is configured to completely reproduce the microwave modulated RF signal after long-distance fiber optic transmission, with no high-frequency signal attenuation or waveform distortion throughout the entire process. This ensures that the phase detection accuracy of the remote station remains consistent with that of the central station, ultimately achieving perfect matching of dual-end compensation performance and guaranteeing the uniformity of bidirectional phase stabilization effect across the entire link.

[0040] The working process of the fiber optic phase-stabilized transmission device of this invention is as follows: The phase-stabilized transmission device mainly uses the first photodetector PD1 to collect the signal round-trip delay caused by the 55km long link transmission. The collected delay information is extracted by the PID algorithm of the central station and the delay is compensated in the next transmission. The second photodetector PD2 at the remote station demodulates the signal transmitted through the long link, and after passing through the PID algorithm, the second isothermal voltage-controlled oscillator OCXO2 recovers a stable signal for user use.

[0041] This invention employs a direct mixing method to measure the change in transmission delay. The LO input of the first mixer is a reference frequency standard, and the RF input is the signal to be phase detected. Both have the same frequency but a phase difference Δ. (t), since the amplitude change of the output signal during the mixing process cannot be accurately derived, the amplitude of its beat frequency signal is represented by C, D is the DC potential in the IF output, and V(t) is the real-time measurement value of a high-precision digital multimeter. First, by artificially changing the phase of the steady-state signal, Δ (t) undergoes a 2π phase change, when Δ When (t) takes the values ​​0 and π, the measured value will reach its maximum value V respectively. max and minimum value V min With simple calculations, C and D can be represented using known maximum and minimum values. Therefore, the phase difference Δ can be deduced from the voltage measurement of the IF signal. (t), and the corresponding relative time delay fluctuation Δφ(t) can also be calculated: ; It is also used for frequency stability calculations.

[0042] In a specific implementation, the dual-receiver dual-transmit fiber phase-stabilized device based on a DFB analog direct-modulated laser of the present invention is used. The output power of the 100MHz signal from the rubidium atomic clock is set to 13.12dBm, and the stability is 4.95×10⁻⁶. -15 / s; The first DFB analog direct-modulated laser DML1 has a maximum output power of 12dBm, a modulation bandwidth of 18GHz, a slant efficiency of 0.141mW / mA, and a linewidth of 5MHz; The second DFB analog direct-modulated laser DML2 has a maximum output power of 13dBm, a modulation bandwidth of 19GHz, a slant efficiency of 0.144mW / mA, and a linewidth of 1.2MHz; Based on the different noise requirements of the forward and reverse links, DML2 uses a narrower linewidth device to reduce the noise of the reverse backhaul link; The first phase-locked dielectric oscillator DRO1 has a signal output power of 13dBm and a phase noise of -115dBc@1KHz; The second phase-locked dielectric oscillator DRO2, the third phase-locked dielectric oscillator DRO3, and the... The four phase-locked dielectric oscillators (DRO4) all have an output power of 16 dBm and a phase noise of -120 dBc at 1 kHz; the first and second temperature-controlled voltage-controlled oscillators (OCXO1 and OCXO2) both have an output power of 15.1 dBm and a phase noise of -118 dBc at 1 kHz; the first, second, and third bandpass filters (BPF1, BPF2, BPF3, and BPF6) all operate at 100 MHz with a bandwidth of 5 MHz; the fourth and fifth bandpass filters (BPF4 and BPF5) both operate at 9 GHz with a bandwidth of 100 MHz; and the low-pass filter (LPF) operates at 1 MHz. The isolation is 35dB; the allowable bandwidth of the first power divider PS1, the second power divider PS2, and the third power divider PS3 is 100MHz, and the insertion loss is 2dB; the allowable bandwidth of the fourth power divider PS4 is 9GHz, and the insertion loss is 0.8dB; the operating bandwidth of the LO and RF terminals of the first mixer is 100MHz, the operating bandwidth of the IF terminal is DC, and the conversion loss is 5dB; the operating bandwidth of the LO and RF terminals of the second and third mixers is 9GHz, the operating bandwidth of the IF terminal is DC, and the conversion loss is 6.9dB; the operating wavelength of the first circulator and the second circulator is 1550nm, the insertion loss is 1dB, and the isolation between the ports of the circulator is 65dB; optical... The fiber optic tray is model G.652, with a link loss of 10.9dB; the first photodetector PD1 and the second photodetector PD2 both operate at a wavelength of 1550nm and a bandwidth of 10.1GHz; the first optical filter OF1 operates at a wavelength of 1550.116nm, a bandwidth of 0.088nm, and an insertion loss of 0.78dB; the second optical filter OF2 operates at a wavelength of 1550.918nm, a bandwidth of 0.088nm, and an insertion loss of 0.6dB; the first fiber polarizer Ps1 and the second fiber polarizer Ps2 both operate at a wavelength of 1550nm, with an insertion loss of 0.3dB and a return loss of 68dB; the digital multimeter has a noise floor of 100mV.

[0043] The maximum and minimum voltage values ​​measured by the high-precision digital multimeter are respectively V max =280mV and V min =281mV, phase detection signal frequency band f0=100MHz, then the corresponding relative time delay fluctuation satisfies the following relationship: ; The relative time delay fluctuation value calculated using the measurement data of V(t) from a single experiment is -0.00984 ps, indicating that the second stability of the steady-state transmission device reaches 10. -15 At this level, according to Allan variance test results, the system frequency stability reaches 10 at an integration time of 10000s. -19 The result indicates that the device of the present invention possesses high long-term frequency stability.

[0044] Comparative Example 1 To verify the technical advantages of this invention, which employs dual independent DFB analog direct-modulated lasers and a dual-receive, dual-transmit active far-end structure compared to the traditional single-source solution, a comparative experiment was conducted. The comparative device used a single two-segment DFB analog direct-modulated laser as the bidirectional transmission source, with a passive reflection link constructed using a Faraday rotator at the far end. No far-end photoelectric recovery or remodulation module was included. The remaining G.652 single-mode fiber link length, frequency reference source, testing instruments, and stability calculation method remained consistent with Example 1.

[0045] Under a 55km G.652 single-mode fiber optic link, long-term frequency stability tests were conducted on the devices of Example 1 and the comparative example, respectively. The test results are as follows: Figure 2 and Figure 3 As shown. By Figure 2 It can be seen that the frequency stability of the device of the present invention reaches 10 Hz within an integration time of 10000s. -19 Magnitude; by Figure 3 It can be seen that the stability of the comparative device using a single two-stage DFB simulated direct-modulation laser structure is approximately 10 under the same test conditions. -18 The results show that, under the same G.652 single-mode fiber link and test conditions, this invention effectively reduces the correlation interference between bidirectional transmitted optical signals and improves long-term frequency stability by employing dual independent DFB analog direct-modulated lasers and a remote active feedback structure.

[0046] Both Embodiment 1 and Comparative Example 1 of this invention were tested under the same conditions of a 55 km G.652 single-mode fiber optic link, the same frequency reference source, the same test equipment, and the same frequency stability calculation method to ensure that the experimental results are comparable.

[0047] Test results show that Embodiment 1 of the present invention achieved 10 in an integration time of 10000s. -19 The frequency stability is on the order of magnitude, while the long-term frequency stability of the first comparison sample under the same test conditions is approximately 10. -18 The long-term frequency stability of this invention is improved by approximately one order of magnitude compared to the comparative example.

[0048] This invention employs two independent DFB analog direct-modulated lasers to transmit forward and reverse optical radio frequency signals, respectively. The two optical signals have different center wavelengths, reducing the correlation between optical fields during bidirectional propagation and thus mitigating the impact of coherent Rayleigh scattering and return light interference on system phase noise. Simultaneously, the remote station utilizes photodetector, radio frequency recovery, and remodulation to form an active feedback link, independent of passive reflection return optical signals. This further reduces coupling errors between the link's round-trip signals, improving error signal detection accuracy and PID control algorithm compensation effectiveness. The combination of dual independent DFB analog direct-modulated lasers and the remote active feedback structure produces a superior long-term phase stability compared to a single two-stage DFB analog direct-modulated laser with a passive reflection structure. This effect is not directly predictable by existing technologies, thus representing a significant technological advancement.

[0049] Therefore, this invention employs a dual-receive, dual-transmit fiber optic phase stabilization device based on a DFB analog direct-modulated laser. Compared to existing technologies, the dual-receive, dual-transmit architecture of this invention's fiber optic phase stabilization transmission device allows the forward and reverse optical signals to be generated by independent light sources, reducing the correlation between the bidirectional optical signals, improving the system's anti-interference capability and long-term stability, and making it suitable for engineering deployments in complex environments. Simultaneously, by adopting a DFB direct-modulation scheme and reducing the number of external modulators, and through a reasonable layout of RF and fiber optic links, the system can achieve high-performance phase stabilization with a smaller size and lower power consumption, making it suitable for applications sensitive to size and power consumption, such as satellite ground stations and distributed array platforms.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A dual-receiver, dual-transmitter fiber-optic phase-stabilized device based on a DFB analog direct-modulated laser, characterized in that, It includes a central station module, a remote station module, and external devices. The external devices are connected to the central station module and the remote station module respectively. The central station module and the remote station module are connected via an optical fiber disk. The central station module, as the transmitter, actively detects and pre-compensates for phase noise introduced by optical fiber transmission. The remote station module, as the transmitter, forms a loop with the central station module to improve signal transmission stability and obtain a frequency signal phase-locked to a reference frequency source.

2. The dual-receiver dual-transmit fiber phase-stabilized device based on a DFB analog direct-modulated laser according to claim 1, characterized in that, The central station module includes a third bandpass filter BPF3, a first phase-locked medium oscillator DRO1, a second mixer, a first temperature-controlled voltage-controlled oscillator OCXO1, a second phase-locked medium oscillator DRO2, a first photodetector PD1, a first DFB analog direct-modulated laser DML1, a first fiber polarization scrambler Ps1, a first circulator, and a first optical filter OF1. The output of the third bandpass filter BPF3 is connected to the input of the first phase-locked medium oscillator DRO1, and the output of the first phase-locked medium oscillator DRO1 is connected to the LO terminal of the second mixer. The IF output signal of the second mixer calculates the transmission delay using a PID algorithm, and inputs the transmission delay into the first isothermal voltage-controlled oscillator OCXO1. The output of the first isothermal voltage-controlled oscillator OCXO1 is sequentially connected to the second phase-locked medium oscillator DRO2, the first DFB analog direct-modulation laser DML1, the first fiber polarization scrambler Ps1, and the first circulator. The first circulator is connected to the other end of the fiber optic disk and the input of the first optical filter OF1. The output of the first optical filter OF1 is connected to the input of the first photodetector PD1. The output of the first photodetector PD1 is connected to the RF terminal of the second mixer. Port 1 of the first circulator is connected to the output of the first fiber polarizer Ps1, port 2 of the first circulator is connected to the other end of the G.652 fiber optic disk, and port 3 of the first circulator is connected to the input of the first optical filter OF1.

3. The dual-receiver dual-transmit fiber phase-stabilizing device based on a DFB analog direct-modulated laser according to claim 1, characterized in that, The remote station module includes a second circulator, a second optical filter OF2, a second photodetector PD2, a third mixer, a second temperature-controlled voltage-controlled oscillator OCXO2, a third power divider PS3, a third phase-locked dielectric oscillator DRO3, a fourth power divider PS4, a fifth bandpass filter BPF5, a second DFB analog direct-modulated laser DML2, a second fiber polarization scrambler Ps2, a fourth bandpass filter BPF4, a second power divider PS2, a sixth bandpass filter BPF6, and a fourth phase-locked dielectric oscillator DRO4. Port 2 of the second circulator is connected to one end of a G.652 fiber optic cable, and port 3 of the second circulator is connected to the input of the second optical filter OF2. The output of the second optical filter OF2 is connected to the input of the second photodetector PD2, and the output of the second photodetector PD2 is connected to the RF terminal of the third mixer. The LO terminal of the third mixer is connected to the output terminal of the fourth bandpass filter BPF4, the input terminal of the fourth bandpass filter BPF4 is connected to port 1 of the fourth power divider PS4, the port 2 of the fourth power divider PS4 is connected to the input terminal of the fifth bandpass filter BPF5, the output terminal of the fifth bandpass filter BPF5 is connected in sequence to the second DFB analog direct-modulated laser DML2 and the second fiber polarizer Ps2, and the output terminal of the second fiber polarizer Ps2 is connected to port 1 of the second circulator. The S port of the fourth power divider PS4 is connected to the output of the third phase-locked dielectric oscillator DRO3. The input of the third phase-locked dielectric oscillator DRO3 is connected to the 2 port of the third power divider PS3. The 1 port of the third power divider PS3 is connected to the S port of the second power divider PS2. The 1 port of the second power divider PS2 is connected to the input of the sixth bandpass filter BPF6. The 2 port of the second power divider PS2 is connected to the input of the fourth phase-locked dielectric oscillator DRO4. The S port of the third power divider PS3 is connected to the output of the second isothermal voltage-controlled oscillator OCXO2. The signal output from the IF port of the third mixer is calculated by a PID algorithm and input into the second isothermal voltage-controlled oscillator OCXO2. The sixth bandpass filter BPF6 is connected to the RF port of the first mixer.

4. The dual-receiver dual-transmit fiber phase-stabilizing device based on a DFB analog direct-modulated laser according to claim 1, characterized in that, The external components of the module include a rubidium atomic clock, a first bandpass filter BPF1, a first power divider PS1, a second bandpass filter BPF2, a first mixer, a low-pass filter LPF, a digital multimeter, and a computer. The rubidium atomic clock is connected to the input of the first bandpass filter BPF1. The output of the first bandpass filter BPF1 is connected to the S terminal of the first power divider PS1. The I terminal of the first power divider PS1 is connected to the input of the second bandpass filter BPF2. The output of the second bandpass filter BPF2 is connected to the LO terminal of the first mixer. The IF terminal of the first mixer is connected to the input of the low-pass filter LPF. The output of the low-pass filter LPF is connected to the digital multimeter and the computer in sequence. The RF terminal of the first mixer is connected to the output of the remote station module. The input of the remote station module is connected to one end of the fiber optic tray. The other end of the fiber optic tray is connected to the output of the central station module. The input of the central station module is connected to the II terminal of the first power divider PS1 through a third bandpass filter BPF3.

5. The dual-receiver dual-transmit fiber phase-stabilizing device based on a DFB analog direct-modulated laser according to claim 4, characterized in that, The fiber optic cable is model G.652, with a link loss of <11dB; The rubidium atomic clock outputs a 100MHz signal with an output power of 9~13dBm and a stability of <10-14 / s. The first bandpass filter BPF1 and the second bandpass filter BPF2 operate at frequencies of 95~105MHz, have a filtering bandwidth of <10MHz, and an insertion loss of <5dB. The first power divider PS1 has an allowable bandwidth of 2~500MHz and an insertion loss of <1.5dB; The operating bandwidth of the LO and RF terminals of the first mixer is 0.5-500MHz, the operating bandwidth of the IF terminal is DC-500MHz, and the frequency conversion loss is ≤8dB. The low-pass filter LPF operates at a frequency ≤1MHz and has an isolation of <40dB. The digital multimeter has a noise floor of ≤100mV and a measurement accuracy of 7 1 / 2.

6. The dual-receiver dual-transmit fiber phase-stabilized device based on a DFB analog direct-modulated laser according to claim 2, characterized in that, The first circulator has an insertion loss of <3dB, operates at the C-band wavelength, and has an isolation of >60dB between its ports. The third bandpass filter BPF3 operates at a frequency of 95~105MHz, has a filtering bandwidth of <10MHz, and an insertion loss of <5dB. The signal output power of the first phase-locked dielectric oscillator DRO1 and the second phase-locked dielectric oscillator DRO2 are both ≥13dBm, and the phase noise is ≤-113dBc / Hz@1KHz; The signal output power of the first temperature-controlled voltage oscillator OCXO1 is ≥15dBm and the phase noise is ≤-110dBc@1KHz; The first DFB analog direct-modulated laser DML1 has a working wavelength of 1550nm, a maximum output power of ≤12dBm, a modulation bandwidth of ≤18GHz, a slope efficiency of >0.14mW / mA, a linewidth of <10MHz, and a relative intensity noise of <-145dB / Hz; The first fiber polarization scrambler Ps1 operates at a wavelength of 1260-1650nm, with an insertion loss of <0.5dB and a return loss of >65dB. The first optical filter OF1 has an operating wavelength of 1550.116nm, an operating bandwidth of <0.1nm, and an insertion loss of ≤0.8dB. The first photodetector PD1 operates in the C-band with a bandwidth of ≥10GHz; The second mixer has a working bandwidth of 7-34GHz for both the LO and RF terminals, a working bandwidth of DC-8GHz for the IF terminal, and a conversion loss of ≤15dB.

7. The dual-receiver dual-transmit fiber phase-stabilized device based on a DFB analog direct-modulated laser according to claim 3, characterized in that, The second circulator has an insertion loss of <3dB, operates at the C-band wavelength, and has an isolation of >60dB between its ports. The second DFB analog direct-modulated laser DML2 has a working wavelength of 1550.8nm, a maximum output power of ≤13dBm, a modulation bandwidth of ≤19GHz, a slope efficiency of >0.14mW / mA, a linewidth of <2MHz, and a relative intensity noise of <-150dB / Hz; The second fiber polarization scrambler Ps2 operates at a wavelength of 1260-1650nm, with an insertion loss of <0.5dB and a return loss of >65dB. The second optical filter OF2 has an operating wavelength of 1550.918nm, an operating bandwidth of <0.1nm, and an insertion loss of ≤0.8dB.

8. The dual-receiver dual-transmit fiber phase-stabilized device based on a DFB analog direct-modulated laser according to claim 3, characterized in that, The signal output power of the third phase-locked dielectric oscillator DRO3 and the fourth phase-locked dielectric oscillator DRO4 are both ≥13dBm, and the phase noise is ≤-113dBc / Hz@1KHz. The signal output power of the second constant temperature voltage-controlled oscillator OCXO2 is ≥15dBm and the phase noise is ≤-110dBc@1KHz; The fourth bandpass filter BPF4 and the fifth bandpass filter BPF5 operate at frequencies of 8.9~9.1GHz, have a filtering bandwidth of <200MHz, and an insertion loss of <3dB. The sixth bandpass filter BPF6 operates at a frequency of 95~105MHz, has a filtering bandwidth of <10MHz, and an insertion loss of <5dB. The second power divider PS2 and the third power divider PS3 have an allowable bandwidth of 2~500MHz and an insertion loss of <1.5dB; the fourth power divider PS4 has an allowable bandwidth of 7~12.4GHz and an insertion loss of <1dB.

9. A dual-receiver dual-transmit fiber phase-stabilized device based on a DFB analog direct-modulated laser according to claim 3, characterized in that, The operating bandwidth of the LO and RF terminals of the third mixer is 7-34GHz, the operating bandwidth of the IF terminal is DC-8GHz, and the frequency conversion loss is ≤15dB. The second photodetector PD2 operates in the C-band with a bandwidth of ≥10GHz.

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