阅读说明：本技术 一种用于光纤稳相传输设备的校准装置 (Calibration device for optical fiber phase-stabilized transmission equipment ) 是由 岳耀笠 张首刚 高帅和 胡珍源 李鹏伟 张昕 眭明 农定鹏 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种用于光纤稳相传输设备的校准装置,包括一次连接的稳频激光器、基于3×3光纤耦合器的迈克尔逊光纤干涉仪、第一波分复用器WDM-1、第二波分复用器WDM-2和设有第一光电探测器PD1及第二光电探测器PD2解调电路板。这种装置采用稳频激光器作为光源、光纤干涉仪进行传输延时变化量测量,能实现1fs量级或亚飞秒量级的传输延时变化量测量分辨率和测量准确度。(The invention discloses a calibration device for optical fiber phase-stabilized transmission equipment, which comprises a frequency-stabilized laser, a Michelson optical fiber interferometer based on a 3 x 3 optical fiber coupler, a first wavelength division multiplexer (WDM-1), a second wavelength division multiplexer (WDM-2) and a demodulation circuit board provided with a first photoelectric detector PD1 and a second photoelectric detector PD2, wherein the frequency-stabilized laser is connected at one time. The device adopts the frequency stabilized laser as a light source and an optical fiber interferometer to measure the transmission delay variation, and can realize the measurement resolution and the measurement accuracy of the transmission delay variation with the magnitude of 1fs or the magnitude of sub-femtosecond.)

1. A calibration device for an optical fiber phase-stabilized transmission device is characterized by comprising a frequency stabilized laser, a Michelson optical fiber interferometer based on a 3 x 3 optical fiber coupler, a first wavelength division multiplexer WDM-1, a second wavelength division multiplexer WDM-2 and a demodulation circuit board provided with a first photoelectric detector PD1 and a second photoelectric detector PD2, wherein the frequency stabilized laser outputs narrow-linewidth frequency stabilized laser which is connected to a port 1 of the 3 x 3 optical fiber coupler and divided into three beams which are respectively output by ports 4, 5 and 6 of the 3 x 3 optical fiber coupler, a port 4 of the 3 x 3 optical fiber coupler is connected with a reflection port of the first wavelength division multiplexer-1, a common end of the first wavelength division multiplexer-1 is externally connected with an input end of an optical fiber phase compensator, an output end of the optical fiber phase compensator is connected with a transmission optical fiber, the other end of the transmission optical fiber is connected with a common end of the second wavelength division multiplexer WDM-2, the reflection end of the second wavelength division multiplexer WDM-2 is connected with a third Faraday rotation reflector FRM-3, the third Faraday rotation reflector FRM-3 reflects the frequency stabilized laser back to the 3X 3 optical fiber coupler as a detection optical signal, the frequency stabilized laser which is output from the 6 port of the 3X 3 optical fiber coupler enters a fourth Faraday rotation reflector FRM-4 connected with the 6 port of the 3X 3 optical fiber coupler and is reflected back to the 3X 3 optical fiber coupler is used as a reference optical signal, in addition, the transmission end of the first wavelength division multiplexer WDM-1 is connected with a first Faraday rotation reflector FRM-1, the transmission end of the second wavelength division multiplexer WDM-2 is connected with a second Faraday rotation reflector FRM-2, the 2 port of the 3X 3 optical fiber coupler and the 3 port are respectively connected with a first photoelectric detector PD 78, 1, a second photoelectric detector PD1, a third photoelectric detector PD on the board, The second photoelectric detector PD2 outputs the detected real-time compensation effect of the optical fiber phase compensator to an external computer by the demodulation board, when an input end optical fiber interferometer and an output end optical fiber interferometer are arranged in the external optical fiber phase compensator, one path of phase drift detection laser emitted by the optical fiber phase compensator is emitted by the input end, is output to the public end of the first wavelength division multiplexer WDM-1, is output by the transmission end of the first wavelength division multiplexer WDM-1, enters the first Faraday magnetic rotating reflector FRM-1 and is reflected back to the optical fiber phase compensator input end optical fiber interferometer in the original path; the other path of phase drift detection laser emitted by the optical fiber phase compensator is emitted by an output end, is output to a public end of a second wavelength division multiplexer WDM-2 through transmission optical fiber, is output by a transmission end of the second wavelength division multiplexer WDM-2, enters a second Faraday magnetic rotating reflector FRM-2, is reflected back to an optical fiber interferometer at the output end of the optical fiber phase compensator in the original path, completes the phase drift detection closed loop of an input optical fiber and an output optical fiber of the optical fiber phase compensator, and further completes the compensation closed loop of a transmission optical fiber link; when only the output end optical fiber interferometer exists in the optical fiber phase compensator, phase drift detection laser emitted by the optical fiber phase compensator is emitted by the output end, is output to the public end of the second wavelength division multiplexer WDM-2 through transmission optical fiber, is output by the transmission end of the second wavelength division multiplexer WDM-2, enters the second Faraday magnetic rotating reflector FRM-2, and is reflected back to the optical fiber phase compensator output end optical fiber interferometer by the original circuit, phase drift detection closed loop of the input optical fiber and the output optical fiber of the optical fiber phase compensator is completed, compensation closed loop of a transmission optical fiber link is further completed, and the first wavelength division multiplexer WDM-1 and the first Faraday magnetic rotating reflector FRM-1 do not work.

2. The calibration device according to claim 1, wherein the difference between the operating wavelength of the frequency stabilized laser and the operating wavelength of the externally connected fiber phase compensator built-in laser is at least 0.8nm, and the frequency interval is 100 GHz.

3. The calibration device according to claim 1, wherein the linewidth of the frequency stabilized laser is an order of magnitude lower than the linewidth of the laser corresponding to the coherence length required by the arm length difference of the michelson fiber optic interferometer.

4. The calibration device according to claim 1, wherein the frequency stabilized laser is adapted to:

assuming that the arm length difference of the Michelson optical fiber interferometer is L, the unit of the L is m, the unit of the L is fs, the measurement error D is allowed by the calibration device of the optical fiber phase-stabilizing transmission equipment, and the unit of the D is fs, the frequency-stabilizing laserThe frequency stability of the frequency stabilized laser is achieved when the laser frequency is f, the refractive index of the fiber core of the optical fiber is n, and c is the vacuum light velocityThe indexes of the stability in the day are:

。

5. the calibration apparatus for a fiber phase-stabilized transmission device according to claim 1, wherein assuming that the fiber length from the 3 × 3 fiber coupler to the first wavelength division multiplexer WDM-1 is L1, the fiber length from the first wavelength division multiplexer WDM-1 to the first faraday magnetic rotation mirror FRM-1 is L2, the fiber length from the second wavelength division multiplexer WDM-2 to the third faraday magnetic rotation mirror FRM-3 is L3, the fiber length from the second wavelength division multiplexer WDM-2 to the second faraday magnetic rotation mirror FRM-2 is L4, the fiber length from the 3 × 3 fiber coupler to the fourth faraday magnetic rotation mirror FRM-4 is L5, and the fibers used in L1-L5 should operate in the same temperature environment, and satisfy the following relationships:

。

6. the calibration device according to claim 1, wherein the first wavelength division multiplexer WDM-1 and the second wavelength division multiplexer WDM-2 are each provided with three optical fiber ports, namely a common port, a transmission port and a reflection port, wherein the working bandwidth of the reflection port covers the working wavelength of the frequency stabilized laser, and the working bandwidth of the transmission port covers the working wavelength of the external optical fiber phase compensator; or the working bandwidth of the transmission end covers the working wavelength of the frequency stabilized laser, the working bandwidth of the reflection end covers the working wavelength of the external optical fiber phase compensator, at the moment, the transmission end of the first wavelength division multiplexer WDM-1 is connected with 4 ports of the 3 multiplied by 3 optical fiber coupler, the reflection end of the first wavelength division multiplexer WDM-1 is connected with the first Faraday magnetic rotation reflector FRM-1, and the common end of the first wavelength division multiplexer WDM-1 is externally connected with the input end of the optical fiber phase compensator; the transmission end of the second wavelength division multiplexer WDM-2 is connected with the third Faraday magnetic rotation reflector FRM-3, the reflection end of the second wavelength division multiplexer WDM-2 is connected with the second Faraday magnetic rotation reflector FRM-2, and the public end of the second wavelength division multiplexer WDM-2 is externally connected with the output end of the optical fiber phase compensator.

7. The calibration device according to claim 1, wherein the 1, 2, and 3 ports of the 3 x 3 fiber coupler are interchangeable and are all located on the same side of the 3 x 3 fiber coupler, and the 4, 5, and 6 ports of the 3 x 3 fiber coupler are also interchangeable and are all located on the other side of the 3 x 3 fiber coupler, i.e. on a different side from the 1, 2, and 3 ports of the 3 x 3 fiber coupler.

Technical Field

The invention relates to an optical fiber transmission technology, in particular to a calibration device for optical fiber phase-stabilized transmission equipment.

Background

The optical fiber phase-stabilizing transmission technology is widely applied to the fields of time-frequency transmission, satellite measurement and control, phase-coherent signal transmission and the like, and achieves a high technical level, wherein the transmission delay variation measurement and compensation precision of the optical fiber phase-stabilizing transmission technology based on microwave phase discrimination and optical domain compensation reaches 0.1ps magnitude, and the transmission delay variation measurement and compensation precision of the optical fiber phase-stabilizing transmission technology based on optical fiber interferometer coherent detection and optical domain compensation reaches 1fs magnitude. However, at present, no mature technology and instrument support femtosecond-level high-precision calibration and calibration of the transmission delay variation of the above optical fiber phase-stabilized transmission equipment, and effective technical performance inspection of the above optical fiber phase-stabilized transmission equipment is also impossible.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a calibration device for an optical fiber phase-stabilized transmission device. The device adopts the frequency stabilized laser as a light source and an optical fiber interferometer to measure the transmission delay variation, and can realize the measurement resolution and the measurement accuracy of the transmission delay variation with the magnitude of 1fs or the magnitude of sub-femtosecond.

The technical scheme for realizing the purpose of the invention is as follows:

a calibration device for an optical fiber phase-stabilized transmission device comprises a frequency stabilized laser, a Michelson optical fiber interferometer based on a 3 x 3 optical fiber coupler, a first wavelength division multiplexer WDM-1, a second wavelength division multiplexer WDM-2 and a demodulation circuit board provided with a first photoelectric detector PD1 and a second photoelectric detector PD2, wherein the frequency stabilized laser outputs narrow-linewidth frequency stabilized laser which is connected to a port 1 of the 3 x 3 optical fiber coupler and divided into three beams which are respectively output by ports 4, 5 and 6 of the 3 x 3 optical fiber coupler, a port 4 of the 3 x 3 optical fiber coupler is connected with a reflection port of the first wavelength division multiplexer WDM-1, a common end of the first wavelength division multiplexer WDM-1 is externally connected with an input end of an optical fiber phase compensator, an output end of the optical fiber phase compensator is connected with a transmission optical fiber, the other end of the transmission optical fiber is connected with a common end of the second wavelength division multiplexer WDM-2, the reflection end of the second wavelength division multiplexer WDM-2 is connected with a third Faraday rotation reflector FRM-3, the third Faraday rotation reflector FRM-3 reflects the frequency stabilized laser back to the 3X 3 optical fiber coupler as a detection optical signal, the frequency stabilized laser which is output from the 6 port of the 3X 3 optical fiber coupler enters a fourth Faraday rotation reflector FRM-4 connected with the 6 port of the 3X 3 optical fiber coupler and is reflected back to the 3X 3 optical fiber coupler is used as a reference optical signal, in addition, the transmission end of the first wavelength division multiplexer WDM-1 is connected with a first Faraday rotation reflector FRM-1, the transmission end of the second wavelength division multiplexer WDM-2 is connected with a second Faraday rotation reflector FRM-2, the 2 port of the 3X 3 optical fiber coupler and the 3 port are respectively connected with a first photoelectric detector PD 78, a second photoelectric detector PD1, a third photoelectric detector PD-3, a third Faraday rotation reflector FRM-3, and a third Faraday rotation reflector FRM-3 are connected with the third Faraday rotation reflector FRM-3 and the third Faraday rotation reflector FRM-3 and the frequency stabilized laser which is connected with the third Faraday rotation reflector and the optical fiber coupler and the third fiber coupler respectively, The second photoelectric detector PD2 outputs the detected real-time compensation effect of the optical fiber phase compensator to an external computer by the demodulation board, when an input end optical fiber interferometer and an output end optical fiber interferometer are arranged in the external optical fiber phase compensator, one path of phase drift detection laser emitted by the optical fiber phase compensator is emitted by the input end, is output to the public end of the first wavelength division multiplexer WDM-1, is output by the transmission end of the first wavelength division multiplexer WDM-1, enters the first Faraday magnetic rotating reflector FRM-1 and is reflected back to the optical fiber phase compensator input end optical fiber interferometer in the original path; the other path of phase drift detection laser emitted by the optical fiber phase compensator is emitted by an output end, is output to a public end of a second wavelength division multiplexer WDM-2 through transmission optical fiber, is output by a transmission end of the second wavelength division multiplexer WDM-2, enters a second Faraday magnetic rotating reflector FRM-2, is reflected back to an optical fiber interferometer at the output end of the optical fiber phase compensator in the original path, completes the phase drift detection closed loop of an input optical fiber and an output optical fiber of the optical fiber phase compensator, and further completes the compensation closed loop of a transmission optical fiber link; when only the output end optical fiber interferometer exists in the optical fiber phase compensator, phase drift detection laser emitted by the optical fiber phase compensator is emitted by the output end, is output to the public end of the second wavelength division multiplexer WDM-2 through transmission optical fiber, is output by the transmission end of the second wavelength division multiplexer WDM-2, enters the second Faraday magnetic rotating reflector FRM-2, and is reflected back to the optical fiber phase compensator output end optical fiber interferometer by the original circuit, phase drift detection closed loop of the input optical fiber and the output optical fiber of the optical fiber phase compensator is completed, compensation closed loop of a transmission optical fiber link is further completed, and the first wavelength division multiplexer WDM-1 and the first Faraday magnetic rotating reflector FRM-1 do not work.

The working wavelength of the frequency stabilized laser is different from that of the externally connected optical fiber phase compensator built-in laser by at least 0.8nm, and the frequency interval is 100 GHz.

The laser linewidth of the frequency stabilized laser needs to be one order of magnitude lower than the laser linewidth corresponding to the coherence length needed by the arm length difference of the Michelson fiber interferometer.

The frequency stabilized laser needs to satisfy the following conditions:

assuming that the arm length difference of the Michelson optical fiber interferometer is L, the unit of the L is m, the measurement error D is allowed by the optical fiber phase-stabilizing transmission equipment calibration device, the unit of the D is fs, the laser frequency of the frequency-stabilized laser is f, the refractive index of the fiber core of the optical fiber is n, and the c is the vacuum light velocity, the frequency stability of the frequency-stabilized laser is realizedThe indexes of the stability in the day are:

。

assuming that the length of the optical fiber from the 3 × 3 optical fiber coupler to the first wavelength division multiplexer WDM-1 is L1, the length of the optical fiber from the first wavelength division multiplexer WDM-1 to the first faraday magnetic rotating mirror FRM-1 is L2, the length of the optical fiber from the second wavelength division multiplexer WDM-2 to the third faraday magnetic rotating mirror FRM-3 is L3, the length of the optical fiber from the second wavelength division multiplexer WDM-2 to the second faraday magnetic rotating mirror FRM-2 is L4, the length of the optical fiber from the 3 × 3 optical fiber coupler to the fourth faraday magnetic rotating mirror FRM-4 is L5, and the optical fibers used by L1-L5 need to operate in the same temperature environment, and satisfy the following relationships:

。

the first wavelength division multiplexer WDM-1 and the second wavelength division multiplexer WDM-2 are respectively provided with three optical fiber ports of a public end, a transmission end and a reflection end, wherein the working bandwidth of the reflection end covers the working wavelength of the frequency stabilized laser, and the working bandwidth of the transmission end covers the working wavelength of an external optical fiber phase compensator; or the working bandwidth of the reflection end covers the working wavelength of the frequency stabilized laser, the working bandwidth of the transmission end covers the working wavelength of the external optical fiber phase compensator, at this time, the reflection end of the first wavelength division multiplexer WDM-1 is connected with 4 ports of the 3 x 3 optical fiber coupler, the reflection end of the first wavelength division multiplexer WDM-1 is connected with the first Faraday magnetic rotation reflector FRM-1, the common end of the first wavelength division multiplexer WDM-1 is connected with the input end of the external optical fiber phase compensator, the transmission end of the second wavelength division multiplexer WDM-2 is connected with the third Faraday magnetic rotation reflector FRM-3, the reflection end of the second wavelength division multiplexer WDM-2 is connected with the second Faraday magnetic rotation reflector FRM-2, and the common end of the second wavelength division multiplexer WDM-2 is connected with the output end of the external optical fiber phase compensator.

The 1, 2 and 3 ports of the 3 × 3 optical fiber coupler are interchangeable and are all located on the same side of the 3 × 3 optical fiber coupler, and the 4, 5 and 6 ports of the 3 × 3 optical fiber coupler are also interchangeable and are all located on the other side of the 3 × 3 optical fiber coupler, that is, on different sides from the 1, 2 and 3 ports of the 3 × 3 optical fiber coupler.

According to the technical scheme, a fringe counting method is adopted for measuring the transmission delay variation, and the delay variation resolution ratio corresponding to the actually measured count value multiplied by 1 count value is the transmission delay variation compensation error of the optical fiber phase-stabilized transmission equipment.

Compared with the prior art, the technical scheme can realize femtosecond-level optical fiber transmission delay variation measurement under the condition of controllable system errors, and provides a measurement basis for the compensation performance and the system error control performance of the optical fiber phase-stabilized transmission equipment.

The device adopts the frequency stabilized laser as a light source and an optical fiber interferometer to measure the transmission delay variation, and can realize the measurement resolution and the measurement accuracy of the transmission delay variation with the magnitude of 1fs or the magnitude of sub-femtosecond.

Drawings

Fig. 1 is a schematic structural diagram of the embodiment.

Detailed Description

The invention will be further elucidated with reference to the drawings and examples, without however being limited thereto.

Example (b):

referring to fig. 1, a calibration device for an optical fiber phase-stabilized transmission device comprises a frequency stabilized laser, a michelson optical fiber interferometer based on a 3 × 3 optical fiber coupler, a first wavelength division multiplexer WDM-1, a second wavelength division multiplexer WDM-2, and a demodulation circuit board provided with a first photodetector PD1 and a second photodetector PD2, wherein the frequency stabilized laser outputs a narrow-linewidth frequency stabilized laser, the narrow-linewidth frequency stabilized laser is connected to a port 1 of the 3 × 3 optical fiber coupler and is divided into three beams, the three beams are respectively output by ports 4, 5 and 6 of the 3 × 3 optical fiber coupler, a port 4 of the 3 × 3 optical fiber coupler is connected to a reflection port of the first wavelength division multiplexer-1, a common end of the first wavelength division multiplexer WDM-1 is externally connected with an input end of an optical fiber phase compensator, an output end of the optical fiber phase compensator is connected to a transmission optical fiber, and the other end of the transmission optical fiber is connected to a common end of the second wavelength division multiplexer WDM-2, the reflection end of the second wavelength division multiplexer WDM-2 is connected with a third Faraday rotation reflector FRM-3, the third Faraday rotation reflector FRM-3 reflects the frequency stabilized laser back to the 3X 3 optical fiber coupler as a detection optical signal, the frequency stabilized laser which is output from the 6 port of the 3X 3 optical fiber coupler enters a fourth Faraday rotation reflector FRM-4 connected with the 6 port of the 3X 3 optical fiber coupler and is reflected back to the 3X 3 optical fiber coupler is used as a reference optical signal, in addition, the transmission end of the first wavelength division multiplexer WDM-1 is connected with a first Faraday rotation reflector FRM-1, the transmission end of the second wavelength division multiplexer WDM-2 is connected with a second Faraday rotation reflector FRM-2, the 2 port of the 3X 3 optical fiber coupler and the 3 port are respectively connected with a first photoelectric detector PD 78, 1, a second photoelectric detector PD1, a third photoelectric detector PD on the board, The second photoelectric detector PD2 outputs the detected real-time compensation effect of the optical fiber phase compensator to an external computer by the demodulation board, when an input end optical fiber interferometer and an output end optical fiber interferometer are arranged in the external optical fiber phase compensator, one path of phase drift detection laser emitted by the optical fiber phase compensator is emitted by the input end, is output to the public end of the first wavelength division multiplexer WDM-1, is output by the transmission end of the first wavelength division multiplexer WDM-1, enters the first Faraday magnetic rotating reflector FRM-1 and is reflected back to the optical fiber phase compensator input end optical fiber interferometer in the original path; the other path of phase drift detection laser emitted by the optical fiber phase compensator is emitted by an output end, is output to a public end of a second wavelength division multiplexer WDM-2 through transmission optical fiber, is output by a transmission end of the second wavelength division multiplexer WDM-2, enters a second Faraday magnetic rotating reflector FRM-2, is reflected back to an optical fiber interferometer at the output end of the optical fiber phase compensator in the original path, completes the phase drift detection closed loop of an input optical fiber and an output optical fiber of the optical fiber phase compensator, and further completes the compensation closed loop of a transmission optical fiber link; when only the output end optical fiber interferometer exists in the optical fiber phase compensator, phase drift detection laser emitted by the optical fiber phase compensator is emitted by the output end, is output to the public end of the second wavelength division multiplexer WDM-2 through transmission optical fiber, is output by the transmission end of the second wavelength division multiplexer WDM-2, enters the second Faraday magnetic rotating reflector FRM-2, and is reflected back to the optical fiber phase compensator output end optical fiber interferometer by the original circuit, phase drift detection closed loop of the input optical fiber and the output optical fiber of the optical fiber phase compensator is completed, compensation closed loop of a transmission optical fiber link is further completed, and the first wavelength division multiplexer WDM-1 and the first Faraday magnetic rotating reflector FRM-1 do not work.

The working wavelength of the frequency stabilized laser is different from that of an externally connected optical fiber phase compensator built-in laser by at least 0.8nm, and the frequency interval is 100GHz, in the embodiment, the working wavelength of the frequency stabilized laser is 1550.12nm, the working wavelength of the optical fiber phase compensator built-in laser is 1550.92nm, and the wavelength difference between the working wavelength of the frequency stabilized laser and the working wavelength of the externally connected optical fiber phase compensator built-in laser is 0.8 nm.

The laser linewidth of the frequency stabilized laser needs to be an order of magnitude lower than the laser linewidth corresponding to the coherence length required by the arm length difference of the michelson optical fiber interferometer, in the embodiment, the laser linewidth of the frequency stabilized laser is 1Hz, the coherence length in the corresponding michelson optical fiber interferometer is 100000km at most, and the actual length of the arm length difference optical fiber of the michelson optical fiber interferometer, namely the lengths of the optical fiber phase compensator and the transmission optical fiber, is 2.5km and is far smaller than 100000km by more than one order of magnitude.

The frequency stabilized laser needs to satisfy the following conditions:

supposing that the arm length difference of the michelson optical fiber interferometer is L, the unit of L is m, the measurement error D is allowed by the optical fiber phase-stabilized transmission equipment calibration device, the unit of D is fs, the laser frequency of the frequency stabilized laser is f, the refractive index of the fiber core of the optical fiber is n, and c is the vacuum light velocity, then the frequency stability and the weather stability index of the frequency stabilized laser are as follows:

，

in this example, the arm length difference of the michelson fiber interferometer is L =2.5km, the calibration device of the fiber phase-stabilized transmission equipment allows the measurement error D =10fs, the working frequency f =193.4THz (corresponding to the wavelength of 1550.12 nm) of the frequency-stabilized laser, and the vacuum light speed c =3 × 10⁸And the refractive index n =1.468 of the optical fiber, the frequency stability of the frequency stabilized laserThe stability index needs to satisfy the following relationship:

。

assuming that the length of the optical fiber from the 3 × 3 optical fiber coupler to the first wavelength division multiplexer WDM-1 is L1, the length of the optical fiber from the first wavelength division multiplexer WDM-1 to the first faraday magnetic rotating mirror FRM-1 is L2, the length of the optical fiber from the second wavelength division multiplexer WDM-2 to the third faraday magnetic rotating mirror FRM-3 is L3, the length of the optical fiber from the second wavelength division multiplexer WDM-2 to the second faraday magnetic rotating mirror FRM-2 is L4, the length of the optical fiber from the 3 × 3 optical fiber coupler to the fourth faraday magnetic rotating mirror FRM-4 is L5, and the optical fibers used by L1-L5 need to operate in the same temperature environment, and satisfy the following relationships:

L5=（L1-L2）+（L3-L4），

in this example, L1=2m, L2=1m, L3=2m, L4=1m, L5= (L1-L2) + (L3-L4) = (2 m-1 m) + (2 m-1 m) =2 m.

The first wavelength division multiplexer WDM-1 and the second wavelength division multiplexer WDM-2 are respectively provided with three optical fiber ports of a public end, a transmission end and a reflection end, wherein the working bandwidth of the reflection end covers the working wavelength of the frequency stabilized laser, and the working bandwidth of the transmission end covers the working wavelength of the external optical fiber phase compensator.

The 1, 2 and 3 ports of the 3 × 3 optical fiber coupler are interchangeable and are all located on the same side of the 3 × 3 optical fiber coupler, and the 4, 5 and 6 ports of the 3 × 3 optical fiber coupler are also interchangeable and are all located on the other side of the 3 × 3 optical fiber coupler, that is, on different sides from the 1, 2 and 3 ports of the 3 × 3 optical fiber coupler.

The device adopts a fringe counting method to measure the transmission delay variation, takes a middle point of interference output power as a counting threshold value, namely takes a half-wave period of a sine wave as a counting value, and the counting resolution corresponding to 1550nm laser is 1.29 fs; assuming that the minimum value of the measured count value is-100 and the maximum value is +100 within 24 hours, the compensation error of the transmission delay variation of the optical fiber phase-stabilized transmission equipment is 258 fs.

In this example, the arm length difference between the measurement arm and the reference arm of the fiber interferometer is equal to the length of the optical fiber between the input end and the output end of the fiber phase compensator, or equal to the length of the optical fiber of the closed-loop optical link of the fiber phase compensator, and the optical fiber of the measurement arm and the optical fiber of the reference arm which are equal to the optical fiber of the reference arm work at the same temperature, and the frequency stability of the frequency stabilized laser is less than that of the frequency stabilized laserIn the process, femtosecond-level optical fiber transmission delay variation measurement can be realized under the condition of controllable system errors, and measurement basis is provided for compensation performance and system error control performance of optical fiber phase-stabilized transmission equipment.