A fiber-optic phase-stable transmission device based on laser frequency shifting

Abstract

The present invention discloses a fiber-optic phase-stable transmission device based on laser frequency shifting, comprising a signal demodulation and compensation control unit, a fiber-optic phase drift detection unit, a fiber-optic frequency signal transmission and phase drift compensation unit, and a frequency signal transmission link unit. The signal demodulation and compensation control unit, the fiber-optic phase drift detection unit, and the frequency signal transmission link unit are sequentially connected, and the signal demodulation and compensation control unit, the fiber-optic frequency signal transmission and phase drift compensation unit, and the frequency signal transmission link unit are sequentially connected. This device can achieve phase-stable transmission of time-frequency signals by changing the center frequency of a narrow-linewidth laser serving as a carrier. Theoretically, it can achieve a compensation range far greater than that achieved by changing the optical fiber path length, and a compensation accuracy comparable to that achieved by changing the optical fiber path length for phase-stable compensation.

Description

Technical Field

[0001] The present invention relates to an optical fiber phase-stable transmission technology, in particular to an optical fiber phase-stable transmission device based on laser frequency shift. Background Art

[0002] Fiber-optic phase-stabilized transmission equipment is an optoelectronic device used to compensate for delay variations in optical fiber links and maintain stable phase differences when time-frequency signals are distributed and transmitted via optical fiber. Traditional fiber-optic phase-stabilized transmission equipment uses microwave phase-locking to achieve phase stabilization. This involves cohering the microwave signal traveling back and forth within the fiber with the local oscillator microwave signal. Phase drift is detected and compensated for by varying the fiber delay of the transmission link, or by varying the microwave signal's phase to stabilize the frequency signal at the receiving end of the fiber-optic transmission.

[0003] However, the method of compensating for the phase drift by changing the optical fiber delay of the transmission link has some inherent defects, such as limited adjustable range and time lag in the compensation process; the method of compensating by changing the phase of the microwave signal has the problems of limited compensation resolution and phase mutation of a certain amplitude in the compensated frequency signal. Summary of the Invention

[0004] The present invention addresses the technical limitations of existing fiber-optic phase-stable transmission devices, providing a fiber-optic phase-stable transmission device based on laser frequency shifting. This device achieves phase-stable transmission of time-frequency signals by varying the center frequency of a narrow-linewidth laser serving as a carrier. Theoretically, it can achieve a compensation range far greater than that achieved by varying the optical fiber pathlength, and comparable accuracy to phase-stable compensation achieved by varying the optical fiber pathlength.

[0005] The technical solution for achieving the purpose of the present invention is:

[0006] A fiber optic phase-stable transmission device based on laser frequency shifting includes a signal demodulation and compensation control unit, an optical fiber phase drift detection unit, an optical fiber frequency signal transmission and phase drift compensation unit, and a frequency signal transmission link unit, wherein the signal demodulation and compensation control unit, the optical fiber phase drift detection unit, and the frequency signal transmission link unit are connected in sequence, and the signal demodulation and compensation control unit, the optical fiber frequency signal transmission and phase drift compensation unit, and the frequency signal transmission link unit are connected in sequence.

[0007] The signal demodulation and compensation control unit includes a control circuit having a first photodetector PD1, a second photodetector PD2, a third photodetector PD3, a fourth photodetector PD4, a fifth photodetector PD5, a sixth photodetector PD6, a seventh photodetector PD7, an eighth photodetector PD8, a ninth photodetector PD9 and a tenth photodetector PD10 connected in sequence. The main chip of the control circuit adopts a KINTEX-7 series or similar FPGA chip, a dual-fiber interferometer and a third wavelength division multiplexer WDM3. The control circuit and the third wavelength division multiplexer WDM3 are both connected to the optical fiber phase drift detection unit and the optical fiber frequency signal transmission and phase drift compensation unit.

[0008] The fiber phase drift detection unit includes a first narrow linewidth laser, a first 1×2 fiber coupler and a first fiber interferometer connected in sequence, the first 1×2 fiber coupler is connected to a third wavelength division multiplexer WDM3, wherein the first fiber interferometer is provided with a first 3×3 fiber coupler and a second Faraday magnetic rotation mirror FRM2 connected in sequence, the measuring arm length of the first fiber interferometer is L1, the sensing fiber length can be approximately L1, and the reference arm length is negligible, the first fiber interferometer outputs two optical signals which are received by a first photodetector PD1 and a second photodetector PD2 of a control circuit, wherein the detection signals of the first photodetector PD1 and the second photodetector PD2 can be demodulated by the control circuit to obtain an interference fringe change N1 of the first fiber interferometer with respect to the first narrow linewidth laser, where N1 is a rational number including decimals.

[0009] The fiber frequency signal transmission and phase drift compensation unit is provided with a second narrow linewidth laser, an acousto-optic frequency shifter, a second 1×2 fiber coupler, an electro-optic modulator and a microwave frequency source connected in sequence, wherein the second 1×2 fiber coupler is connected to the third wavelength division multiplexer WDM3, and the acousto-optic frequency shifter is connected to the control circuit in the signal demodulation and compensation control unit.

[0010] The laser wavelengths of the first narrow linewidth laser and the second narrow linewidth laser do not overlap, and the wavelength difference between them is not less than 0.8 nm.

[0011] The frequency signal transmission link unit is provided with a first wavelength division multiplexer WDM1, a second wavelength division multiplexer WDM2 and a first Faraday magnetic rotation mirror FRM1 connected in sequence. A transmission optical fiber L1 is connected between the first wavelength division multiplexer WDM1 and the second wavelength division multiplexer WDM2. The second wavelength division multiplexer WDM2 is connected to the frequency signal receiving device.

[0012] The optical fiber phase-stabilized transmission device based on laser frequency shifting further includes a second optical fiber interferometer and a third optical fiber interferometer, wherein the second optical fiber interferometer is provided with a second 3×3 optical fiber coupler, a measuring arm optical fiber L2, and a third Faraday magnetic rotation mirror FRM3 connected in sequence, the second 3×3 optical fiber coupler is further connected to a fourth Faraday magnetic rotation mirror FRM4, a fourth wavelength division multiplexer WDM4, and a fifth wavelength division multiplexer WDM5, the front end of the second 3×3 optical fiber coupler is connected to a third 1×2 optical fiber coupler, the fourth wavelength division multiplexer WDM4 is connected to the third photodetector PD3 in the control circuit , the fifth photodetector PD5 is connected, the fifth wavelength division multiplexer WDM5 is connected to PD4 and PD6 in the control circuit, and the length of the reference arm of the second fiber optic interferometer can be ignored; the third fiber optic interferometer is provided with a third 3×3 fiber optic coupler, a measuring arm optical fiber L3 and a fifth Faraday magnetic rotation mirror FRM5 connected in sequence, the third 3×3 fiber optic coupler is also connected to a sixth Faraday magnetic rotation mirror FRM6, a sixth wavelength division multiplexer WDM6, and a seventh wavelength division multiplexer WDM7, the front end of the third 3×3 fiber optic coupler is connected to a third 1×2 fiber optic coupler and the sixth wavelength division multiplexer WDM6 The seventh photodetector PD7 and the ninth photodetector PD9 in the control circuit are connected. The seventh wavelength division multiplexer WDM7 is connected to the first photodetector, the eighth photodetector PD8, and the tenth photodetector PD10 in the control circuit. The third 1×2 fiber coupler is connected to the third wavelength division multiplexer WDM3. The reference arm length of the third fiber interferometer can be ignored. The detection signals of the third photodetector PD3 and the fourth photodetector PD4 can be demodulated by the control circuit to obtain the interference fringe change N2 of the second fiber interferometer with respect to the first narrow linewidth laser. The fifth photodetector PD5 The detection signal of the sixth photodetector PD6 can be demodulated by the control circuit to obtain the interference fringe change N4 of the second fiber interferometer with respect to the second narrow linewidth laser. The detection signals of the seventh photodetector PD7 and the eighth photodetector PD8 can be demodulated by the control circuit to obtain the interference fringe change N3 of the third fiber interferometer with respect to the first narrow linewidth laser. The detection signals of the ninth photodetector PD9 and the tenth photodetector PD10 can be demodulated by the control circuit to obtain the interference fringe change N5 of the third fiber interferometer with respect to the second narrow linewidth laser. N2, N3, N4, and N5 are all rational numbers containing decimals.

[0013] The first wavelength division multiplexer WDM1, the second wavelength division multiplexer WDM2, the third wavelength division multiplexer WDM3, the fourth wavelength division multiplexer WDM4, the fifth wavelength division multiplexer WDM5, the sixth wavelength division multiplexer WDM6, and the seventh wavelength division multiplexer WDM7 are all provided with three ports, wherein the center wavelength of the transmission end is consistent with the operating wavelength of the first narrow linewidth laser, the operating wavelength of the reflection end covers the operating wavelength of the second narrow linewidth laser, and the common end jointly transmits the laser signals of the first narrow linewidth laser and the second narrow linewidth laser; or the center wavelength of the transmission end is consistent with the operating wavelength of the second narrow linewidth laser, the operating wavelength of the reflection end covers the operating wavelength of the first narrow linewidth laser, and the common end jointly transmits the laser signals of the first narrow linewidth laser and the second narrow linewidth laser.

[0014] The temperature delay variation coefficients of the measuring arm optical fiber L2 of the second optical fiber interferometer and the measuring arm optical fiber L3 of the second optical fiber interferometer have the following relationship:

[0015]

[0016] Wherein, T is the temperature change, dT is the temperature differential, A is the proportional coefficient, A≠1, n2 is the refractive index of optical fiber L2, and n3 is the refractive index of optical fiber L3.

[0017] In the optical fiber phase drift detection unit, the first narrow linewidth laser emits a coherent continuous laser signal which enters the first optical fiber interferometer through the first 1×2 optical fiber coupler beam splitting output port 1. The measuring arm of the first optical fiber interferometer outputs a coherent continuous laser signal which is connected to the transmission end of the first wavelength division multiplexer WDM1 and is output from the common end of the first wavelength division multiplexer WDM1 into the transmission optical fiber. The transmission optical fiber outputs a coherent continuous laser signal which is connected to the common end of the second wavelength division multiplexer WDM2. The transmission end of the second wavelength division multiplexer WDM2 outputs a coherent continuous laser signal to the first Faraday magnetic rotation mirror FRM1. The first Faraday magnetic rotation mirror FRM1 reflects the coherent continuous laser signal and returns it to the first optical fiber interferometer along the original optical path. The signal is coherent with the local oscillator light of the first optical fiber interferometer and outputs two coherent signals which are connected to the first photodetector PD1 and the second photodetector PD1 of the control circuit. PD2, the control circuit demodulates the interference fringe change N1 of the transmission optical fiber L1; the first narrow linewidth laser emits a coherent continuous laser signal, which is output through the output port 2 of the first 1×2 optical fiber coupler, connected to the transmission end of the third wavelength division multiplexer WDM3, and enters the dual-fiber interferometer through the common end of the third wavelength division multiplexer WDM3. The dual-fiber interferometer outputs a coherent detection signal to the third photodetector PD3 and the fourth photodetector PD4 of the control circuit, and demodulates the interference fringe change N2 of the second optical fiber interferometer relative to the first narrow linewidth laser; the dual-fiber interferometer outputs a coherent detection signal to the seventh photodetector PD7 and the eighth photodetector PD8 of the control circuit, and demodulates the interference fringe change N3 of the third optical fiber interferometer relative to the first narrow linewidth laser; the frequency drift per unit time of the first narrow linewidth laser is demodulated by N2 and N3. for:

[0018]

[0019] The second narrow linewidth laser outputs a continuous laser signal that enters the acousto-optic frequency shifter. The acousto-optic frequency shifter compensates for the transmission delay variation in the transmission optical fiber minus the system error by changing the frequency of the continuous laser signal output by the second narrow linewidth laser and generating a group velocity delay difference. The signal is connected to the electro-optic modulator via the beam splitting output port 1 of the second 1×2 optical fiber coupler. The electro-optic modulator modulates the frequency signal loaded by the second narrow linewidth laser to generate an ROF frequency signal, which is then connected to the reflection end of the first wavelength division multiplexer WDM1. The common end of the first wavelength division multiplexer WDM1 is connected to the transmission optical fiber. The ROF frequency signal output by the transmission optical fiber is then connected to the common end of the second wavelength division multiplexer WDM2. The reflection end of the second wavelength division multiplexer WDM2 outputs a phase-stable transmission signal. The ROF frequency signal is sent to the frequency signal receiving device; the output port 2 of the second 1×2 optical fiber coupler is connected to the reflection end of the third wavelength division multiplexer WDM3 and enters the dual-fiber interferometer, and the dual-fiber interferometer outputs a coherent detection signal to the fifth photodetector PD5 and the sixth photodetector PD6 of the control circuit, and demodulates the interference fringe change N4 of the second optical fiber interferometer relative to the second narrow linewidth laser; the dual-fiber interferometer outputs a coherent detection signal to the ninth photodetector PD9 and the tenth photodetector PD10 of the control circuit, and demodulates the interference fringe change N5 of the third optical fiber interferometer relative to the second narrow linewidth laser; the frequency drift per unit time of the second narrow linewidth laser is demodulated by N4 and N5. for:

[0020]

[0021] The control circuit of the optical fiber phase-stabilized transmission device in this technical solution adjusts the acousto-optic frequency shifter to make the frequency drift of the second narrow linewidth laser The following relationship is satisfied to achieve stable phase transmission:

[0022]

[0023] Where t is the time change, dt is the time differential, and c is the speed of light in a vacuum.

[0024] Compared with the existing technology, this technical solution achieves the purpose of phase-stable transmission of time-frequency signals by highly accurately detecting and adjusting the center frequency of a narrow-linewidth laser serving as a carrier, rather than performing phase-stable compensation control by adjusting the fiber delay with a limited range. This can achieve a compensation range far greater than that obtained by changing the fiber optical path and a compensation accuracy comparable to that achieved by changing the fiber optical path for phase-stable compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the principle of the device in the embodiment;

[0026] Figure 2 Schematic diagram of the structure of the first fiber interferometer in the embodiment;

[0027] Figure 3 Schematic diagram of the dual-fiber interferometer structure in the embodiment. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited thereto.

[0029] Example:

[0030] Reference Figure 1 , an optical fiber phase-stable transmission device based on laser frequency shift, including a signal demodulation and compensation control unit, an optical fiber phase drift detection unit, an optical fiber frequency signal transmission and phase drift compensation unit and a frequency signal transmission link unit, wherein the signal demodulation and compensation control unit, the optical fiber phase drift detection unit and the frequency signal transmission link unit are connected in sequence, and the signal demodulation and compensation control unit, the optical fiber frequency signal transmission and phase drift compensation unit and the frequency signal transmission link unit are connected in sequence.

[0031] The signal demodulation and compensation control unit includes a control circuit having a first photodetector PD1, a second photodetector PD2, a third photodetector PD3, a fourth photodetector PD4, a fifth photodetector PD5, a sixth photodetector PD6, a seventh photodetector PD7, an eighth photodetector PD8, a ninth photodetector PD9 and a tenth photodetector PD10 connected in sequence. In this example, the main chip of the control circuit adopts the KINTEX-7 series. The control circuit and the third wavelength division multiplexer WDM3 are both connected to the optical fiber phase drift detection unit and the optical fiber frequency signal transmission and phase drift compensation unit.

[0032] The optical fiber phase drift detection unit includes a first narrow linewidth laser, a first 1×2 optical fiber coupler and a first optical fiber interferometer connected in sequence, and the first 1×2 optical fiber coupler is connected to a third wavelength division multiplexer WDM3, wherein Figure 2 As shown, the first fiber optic interferometer is provided with a first 3×3 fiber optic coupler and a second Faraday magnetic rotation mirror FRM2 connected in sequence. The measuring arm length of the first fiber optic interferometer is L1, the sensing fiber length can be approximately L1, and the reference arm length is negligible. The first fiber optic interferometer outputs two optical signals which are received by a first photodetector PD1 and a second photodetector PD2 of a control circuit. The detection signals of the first photodetector PD1 and the second photodetector PD2 can be demodulated by the control circuit to obtain a change N1 of the interference fringes of the first fiber optic interferometer with respect to the first narrow linewidth laser, where N1 is a rational number including decimals.

[0033] The fiber frequency signal transmission and phase drift compensation unit is provided with a second narrow linewidth laser, an acousto-optic frequency shifter, a second 1×2 fiber coupler, an electro-optic modulator and a microwave frequency source connected in sequence, wherein the second 1×2 fiber coupler is connected to the third wavelength division multiplexer WDM3, and the acousto-optic frequency shifter is connected to the control circuit in the signal demodulation and compensation control unit.

[0034] The laser wavelengths of the first narrow linewidth laser and the second narrow linewidth laser do not overlap, and the wavelength difference between them is not less than 0.8 nm.

[0035] The frequency signal transmission link unit is provided with a first wavelength division multiplexer WDM1, a second wavelength division multiplexer WDM2 and a first Faraday magnetic rotation mirror FRM1 connected in sequence, a transmission optical fiber L1 is connected between the first wavelength division multiplexer WDM1 and the second wavelength division multiplexer WDM2, and the second wavelength division multiplexer WDM2 is connected to the frequency signal receiving device.

[0036] like Figure 3As shown, the optical fiber phase-stabilized transmission device based on laser frequency shift includes a second optical fiber interferometer and a third optical fiber interferometer, wherein the second optical fiber interferometer is provided with a second 3×3 optical fiber coupler, a measuring arm optical fiber L2 and a third Faraday magnetic rotation mirror FRM3 connected in sequence, the second 3×3 optical fiber coupler is further connected to a fourth Faraday magnetic rotation mirror FRM4, a fourth wavelength division multiplexer WDM4, and a fifth wavelength division multiplexer WDM5, the front end of the second 3×3 optical fiber coupler is connected to a third 1×2 optical fiber coupler, the fourth wavelength division multiplexer WDM4 is connected to the first in the control circuit. The third photodetector PD3 and the fifth photodetector PD5 are connected, and the fifth wavelength division multiplexer WDM5 is connected to the fourth photodetector PD4 and the sixth photodetector PD6 in the control circuit. The length of the reference arm of the second fiber optic interferometer can be ignored. The third fiber optic interferometer is provided with a third 3×3 fiber optic coupler, a measuring arm optical fiber L3 and a fifth Faraday magnetic rotation mirror FRM5 connected in sequence. The third 3×3 fiber optic coupler is also connected to a sixth Faraday magnetic rotation mirror FRM6, a sixth wavelength division multiplexer WDM6, a seventh wavelength division multiplexer WDM7, and the third 3×3 fiber optic coupler is connected to a sixth Faraday magnetic rotation mirror FRM6, a sixth wavelength division multiplexer WDM6, and a seventh wavelength division multiplexer WDM7. The front end of the fiber coupler is connected to the third 1×2 fiber coupler, the sixth wavelength division multiplexer WDM6 is connected to the seventh photodetector PD7 and the ninth photodetector PD9 in the control circuit, the seventh wavelength division multiplexer WDM7 is connected to the eighth photodetector PD8 and the tenth photodetector PD10 in the control circuit, the third 1×2 fiber coupler is connected to the third wavelength division multiplexer WDM3, the reference arm length of the third fiber interferometer can be ignored, wherein the detection signals of the third photodetector PD3 and the fourth photodetector PD4 can be demodulated by the control circuit to obtain the second fiber interferometer. Regarding the interference fringe change N2 of the first narrow linewidth laser, the detection signals of the fifth photodetector PD5 and the sixth photodetector PD6 can be demodulated by the control circuit, the detection signal of the eighth photodetector PD8 can be demodulated by the control circuit to obtain the interference fringe change N3 of the third fiber interferometer regarding the first narrow linewidth laser, and the detection signals of the ninth photodetector PD9 and the tenth photodetector PD10 can be demodulated by the control circuit to obtain the interference fringe change N5 of the third fiber interferometer regarding the second narrow linewidth laser. N2, N3, N4, and N5 are all rational numbers containing decimals.

[0037] The first wavelength division multiplexer WDM1, the second wavelength division multiplexer WDM2, the third wavelength division multiplexer WDM3, the fourth wavelength division multiplexer WDM4, the fifth wavelength division multiplexer WDM5, the sixth wavelength division multiplexer WDM6, and the seventh wavelength division multiplexer WDM7 are all provided with three ports, wherein the center wavelength of the transmission end is consistent with the operating wavelength of the first narrow linewidth laser, the operating wavelength of the reflection end covers the operating wavelength of the second narrow linewidth laser, and the common end jointly transmits the laser signals of the first narrow linewidth laser and the second narrow linewidth laser; or the center wavelength of the transmission end is consistent with the operating wavelength of the second narrow linewidth laser, the operating wavelength of the reflection end covers the operating wavelength of the first narrow linewidth laser, and the common end jointly transmits the laser signals of the first narrow linewidth laser and the second narrow linewidth laser.

[0038] The temperature delay variation coefficients of the measuring arm optical fiber L2 of the second optical fiber interferometer and the measuring arm optical fiber L3 of the second optical fiber interferometer have the following relationship:

[0039]

[0040] Wherein, T is the temperature change, dT is the temperature differential, A is the proportional coefficient, A≠1, n2 is the refractive index of optical fiber L2, and n3 is the refractive index of optical fiber L3.

[0041] In the optical fiber phase drift detection unit, the first narrow linewidth laser emits a coherent continuous laser signal which enters the first optical fiber interferometer through the first 1×2 optical fiber coupler beam splitting output port 1. The measuring arm of the first optical fiber interferometer outputs a coherent continuous laser signal which is connected to the transmission end of the first wavelength division multiplexer WDM1 and is output from the common end of the first wavelength division multiplexer WDM1 into the transmission optical fiber. The transmission optical fiber outputs a coherent continuous laser signal which is connected to the common end of the second wavelength division multiplexer WDM2. The transmission end of the second wavelength division multiplexer WDM2 outputs a coherent continuous laser signal to the first Faraday magnetic rotation mirror FRM1. The first Faraday magnetic rotation mirror FRM1 reflects the coherent continuous laser signal and returns it to the first optical fiber interferometer along the original optical path. The signal is coherent with the local oscillator light of the first optical fiber interferometer and outputs two coherent signals which are connected to the first photodetector PD1 and the second photodetector PD1 of the control circuit. PD2, the control circuit demodulates the interference fringe change N1 of the transmission optical fiber L1; the first narrow linewidth laser emits a coherent continuous laser signal, which is output through the output port 2 of the first 1×2 optical fiber coupler, connected to the transmission end of the third wavelength division multiplexer WDM3, and enters the dual-fiber interferometer through the common end of the third wavelength division multiplexer WDM3. The dual-fiber interferometer outputs a coherent detection signal to the third photodetector PD3 and the fourth photodetector PD4 of the control circuit, and demodulates the interference fringe change N2 of the second optical fiber interferometer relative to the first narrow linewidth laser; the dual-fiber interferometer outputs a coherent detection signal to the seventh photodetector PD7 and the eighth photodetector PD8 of the control circuit, and demodulates the interference fringe change N3 of the third optical fiber interferometer relative to the first narrow linewidth laser; the frequency drift per unit time of the first narrow linewidth laser is demodulated by N2 and N3. for:

[0042]

[0043] The second narrow linewidth laser outputs a continuous laser signal that enters the acousto-optic frequency shifter. The acousto-optic frequency shifter compensates for the transmission delay variation in the transmission optical fiber minus the system error by changing the frequency of the continuous laser signal output by the second narrow linewidth laser and generating a group velocity delay difference. The signal is connected to the electro-optic modulator via the beam splitting output port 1 of the second 1×2 optical fiber coupler. The electro-optic modulator modulates the frequency signal loaded by the second narrow linewidth laser to generate an ROF frequency signal, which is then connected to the reflection end of the first wavelength division multiplexer WDM1. The common end of the first wavelength division multiplexer WDM1 is connected to the transmission optical fiber. The ROF frequency signal output by the transmission optical fiber is then connected to the common end of the second wavelength division multiplexer WDM2. The reflection end of the second wavelength division multiplexer WDM2 outputs a phase-stable transmission signal. The ROF frequency signal is sent to the frequency signal receiving device; the output port 2 of the second 1×2 optical fiber coupler is connected to the reflection end of the third wavelength division multiplexer WDM3 and enters the dual-fiber interferometer, and the dual-fiber interferometer outputs a coherent detection signal to the fifth photodetector PD5 and the sixth photodetector PD6 of the control circuit, and demodulates the interference fringe change N4 of the second optical fiber interferometer relative to the second narrow linewidth laser; the dual-fiber interferometer outputs a coherent detection signal to the ninth photodetector PD9 and the tenth photodetector PD10 of the control circuit, and demodulates the interference fringe change N5 of the third optical fiber interferometer relative to the second narrow linewidth laser; the frequency drift per unit time of the second narrow linewidth laser is demodulated by N4 and N5. for:

[0044]

[0045] The control circuit of the optical fiber phase-stabilized transmission device in this technical solution adjusts the acousto-optic frequency shifter to make the frequency drift of the second narrow linewidth laser The following relationship is satisfied to achieve stable phase transmission:

[0046]

[0047] Where t is the time change, dt is the time differential, and c is the speed of light in a vacuum.

Claims

1. An optical fiber phase-stabilized transmission device based on laser frequency shifting, characterized in that: It includes a signal demodulation and compensation control unit, an optical fiber phase drift detection unit, an optical fiber frequency signal transmission and phase drift compensation unit, and a frequency signal transmission link unit, wherein the signal demodulation and compensation control unit, the optical fiber phase drift detection unit, and the frequency signal transmission link unit are connected in sequence, and the signal demodulation and compensation control unit, the optical fiber frequency signal transmission and phase drift compensation unit, and the frequency signal transmission link unit are connected in sequence; The signal demodulation and compensation control unit includes a control circuit, a dual-fiber interferometer, and a third wavelength division multiplexer WDM3, which are sequentially connected and provided with a first photodetector PD1, a second photodetector PD2, a third photodetector PD3, a fourth photodetector PD4, a fifth photodetector PD5, a sixth photodetector PD6, a seventh photodetector PD7, an eighth photodetector PD8, a ninth photodetector PD9, and a tenth photodetector PD10. The control circuit and the third wavelength division multiplexer WDM3 are both connected to the optical fiber phase drift detection unit and the optical fiber frequency signal transmission and phase drift compensation unit; The fiber phase drift detection unit includes a first narrow linewidth laser, a first 1×2 fiber coupler, and a first fiber interferometer connected in sequence, the first 1×2 fiber coupler is connected to a third wavelength division multiplexer WDM3, wherein the first fiber interferometer is provided with a first 3×3 fiber coupler and a second Faraday magnetic rotation mirror FRM2 connected in sequence, the measuring arm length of the first fiber interferometer is L1, the sensing fiber length is L1, and the reference arm length is negligible, the first fiber interferometer outputs two optical signals which are received by a first photodetector PD1 and a second photodetector PD2 of a control circuit, wherein the detection signals of the first photodetector PD1 and the second photodetector PD2 are demodulated by the control circuit to obtain an interference fringe change N1 of the first fiber interferometer with respect to the first narrow linewidth laser, where N1 is a rational number including decimals; The fiber frequency signal transmission and phase drift compensation unit is provided with a second narrow linewidth laser, an acousto-optic frequency shifter, a second 1×2 fiber coupler, an electro-optic modulator and a microwave frequency source connected in sequence, wherein the second 1×2 fiber coupler is connected to the third wavelength division multiplexer WDM3, and the acousto-optic frequency shifter is connected to the control circuit in the signal demodulation and compensation control unit; The frequency signal transmission link unit is provided with a first wavelength division multiplexer WDM1, a second wavelength division multiplexer WDM2 and a first Faraday magnetic rotation mirror FRM1 connected in sequence, a transmission optical fiber L1 is connected between the first wavelength division multiplexer WDM1 and the second wavelength division multiplexer WDM2, and the second wavelength division multiplexer WDM2 is connected to the frequency signal receiving device.

2. The optical fiber phase-stabilized transmission device based on laser frequency shifting according to claim 1, characterized in that: The laser wavelengths of the first narrow linewidth laser and the second narrow linewidth laser do not overlap, and the wavelength difference between them is not less than 0.8 nm.

3. The optical fiber phase-stabilized transmission device based on laser frequency shifting according to claim 1, characterized in that: The optical fiber phase-stabilized transmission device based on laser frequency shifting further includes a second optical fiber interferometer and a third optical fiber interferometer, wherein the second optical fiber interferometer is provided with a second 3×3 optical fiber coupler, a measuring arm optical fiber L2, and a third Faraday magnetic rotation mirror FRM3 connected in sequence, the second 3×3 optical fiber coupler is further connected to a fourth Faraday magnetic rotation mirror FRM4, a fourth wavelength division multiplexer WDM4, and a fifth wavelength division multiplexer WDM5, the front end of the second 3×3 optical fiber coupler is connected to a third 1×2 optical fiber coupler, the fourth wavelength division multiplexer WDM4 is connected to the third photodetector PD3 in the control circuit , the fifth photodetector PD5 is connected, the fifth wavelength division multiplexer WDM5 is connected to the fourth photodetector PD4 and the sixth photodetector PD6 in the control circuit, and the length of the reference arm of the second fiber optic interferometer is ignored; the third fiber optic interferometer is provided with a third 3×3 fiber optic coupler, a measuring arm optical fiber L3 and a fifth Faraday magnetic rotation mirror FRM5 connected in sequence, the third 3×3 fiber optic coupler is also connected to a sixth Faraday magnetic rotation mirror FRM6, a sixth wavelength division multiplexer WDM6, and a seventh wavelength division multiplexer WDM7, and the front end of the third 3×3 fiber optic coupler is connected to the third 1×2 fiber optic coupler The sixth wavelength division multiplexer WDM6 is connected to the seventh photodetector PD7 and the ninth photodetector PD9 in the control circuit. The seventh wavelength division multiplexer WDM7 is connected to the eighth photodetector PD8 and the tenth photodetector PD10 in the control circuit. The third 1×2 fiber coupler is connected to the third wavelength division multiplexer WDM3. The length of the reference arm of the third fiber interferometer is ignored. The detection signals of the third photodetector PD3 and the fourth photodetector PD4 are demodulated by the control circuit to obtain the interference fringe change N2 of the second fiber interferometer with respect to the first narrow linewidth laser. The fifth photodetector The detection signals of PD5 and the sixth photodetector PD6 are demodulated by the control circuit to obtain the interference fringe change N4 of the second fiber interferometer with respect to the second narrow linewidth laser. The detection signals of the seventh photodetector PD7 and the eighth photodetector PD8 are demodulated by the control circuit to obtain the interference fringe change N3 of the third fiber interferometer with respect to the first narrow linewidth laser. The detection signals of the ninth photodetector PD9 and the tenth photodetector PD10 are demodulated by the control circuit to obtain the interference fringe change N5 of the third fiber interferometer with respect to the second narrow linewidth laser. N2, N3, N4, and N5 are all rational numbers containing decimals.

4. The optical fiber phase-stabilized transmission device based on laser frequency shifting according to claim 1, characterized in that: The first wavelength division multiplexer WDM1, the second wavelength division multiplexer WDM2, the third wavelength division multiplexer WDM3, the fourth wavelength division multiplexer WDM4, the fifth wavelength division multiplexer WDM5, the sixth wavelength division multiplexer WDM6, and the seventh wavelength division multiplexer WDM7 are all provided with three ports, wherein the center wavelength of the transmission end is consistent with the operating wavelength of the first narrow linewidth laser, the operating wavelength of the reflection end covers the operating wavelength of the second narrow linewidth laser, and the common end jointly transmits the laser signals of the first narrow linewidth laser and the second narrow linewidth laser; or the center wavelength of the transmission end is consistent with the operating wavelength of the second narrow linewidth laser, the operating wavelength of the reflection end covers the operating wavelength of the first narrow linewidth laser, and the common end jointly transmits the laser signals of the first narrow linewidth laser and the second narrow linewidth laser.

5. The optical fiber phase-stabilized transmission device based on laser frequency shifting according to claim 3, characterized in that: The temperature delay variation coefficients of the measuring arm optical fiber L2 of the second optical fiber interferometer and the measuring arm optical fiber L3 of the third optical fiber interferometer have the following relationship: Wherein, T is the temperature change, dT is the temperature differential, A is the proportional coefficient, A≠1, n2 is the refractive index of optical fiber L2, and n3 is the refractive index of optical fiber L3.

6. The optical fiber phase-stabilized transmission device based on laser frequency shifting according to claim 1, characterized in that: The frequency drift per unit time of the first narrow linewidth laser for The frequency drift per unit time of the second narrow linewidth laser for The control circuit adjusts the frequency drift of the second narrow linewidth laser The following relations are satisfied: Where t is the time change, dt is the time differential, and c is the speed of light in a vacuum.

Images