CN103812553B - High-precision optical fiber two-way Time transfer receiver equipment delay unsymmetry scaling method - Google Patents

Abstract

A method for calibrating the time delay asymmetry of high-precision fiber optic bidirectional time comparison equipment, comprising the steps of: ① establishing a time delay calibration system for fiber optic bidirectional time comparison equipment; ② calibrating the receiving link time between the fiber optic bidirectional time comparison equipment Delay difference; ③ Calibrate the delay difference of the receiving link between the optical fiber two-way time comparison equipment; ④ Calibrate the delay asymmetry between the optical fiber two-way time comparison equipment. The present invention can not only easily and conveniently calibrate the asymmetry of time delay between optical fiber two-way time comparison equipment, but also can calibrate the time delay asymmetry between any time-frequency equipment, effectively overcome the difference of optical fiber or cable time delay The impact of delay accuracy.

Description

Calibration method for delay asymmetry of high-precision optical fiber two-way time comparison equipment

technical field

The invention relates to a method for calibrating time delay of equipment in the field of optical fiber time synchronization, in particular to a method for calibrating asymmetry of time delay of high-precision optical fiber bidirectional time comparison equipment.

Background technique

Device delay refers to the additional delay generated when the signal passes through the device, which is an inherent characteristic of the device. High-precision optical fiber two-way time comparison sends and receives timing signals through optical fiber links for time synchronization. To obtain accurate time synchronization accuracy, it is necessary to deduct the delay asymmetry of the optical fiber time comparison equipment to obtain accurate clock difference. Therefore, the calibration accuracy of the time delay asymmetry of the optical fiber time synchronization equipment itself will directly affect the accuracy of the optical fiber time synchronization system, and it is a key technology of the optical fiber time synchronization system.

At present, system calibration based on satellite and cable time synchronization mainly calibrates the system delay by measuring the electrical delay. The equipment delay measurement methods mainly include vector network analyzer method, oscilloscope method and time interval counter method. The German Federal Institute of Physics and Technology (Federal Institute of Physics and Technology) proposed a satellite-based optical fiber two-way time comparison method for equipment delay asymmetry (Rost, M., et al. "Time transfer through optical fibers over a distance of 73km with an uncertainty below 100ps."Metrologia49.6(2012):772.), but it cannot deduct the influence of optical fiber and cable on the accuracy of the equipment.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art, provide a high-precision optical fiber two-way time comparison equipment time delay asymmetry calibration method, through the combination of measurement methods, realize the time delay asymmetry of the optical fiber two-way time comparison equipment High precision calibration.

Device latency refers to the time delay required for a signal to travel from a device input port to an output port. The delay of the optical fiber two-way time comparison equipment is divided into the delay of the transmission link and the delay of the reception link: the starting point of the delay of the transmission link is the input port of the timing signal transmitted on the device, and the end point of the delay of the transmission link is the device The output port of the optical signal carrying the transmitted timing signal; the starting point of the receiving link delay is the input port on the device that receives the optical signal carrying the timing signal of the other party, and the end point is the output port of the timing signal received from the other party.

The delay of the transmitting device comes from the following two links that introduce delay: time coding processing delay Delay introduced by electro-optical conversion and optical fiber duplexer (such as circulator, WDM, etc.) Therefore, the transmit link delay can be expressed as:

Similar to the delay of the transmitting device, the delay of the receiving device also comes from two links that introduce delay: the delay introduced by photoelectric conversion and optical fiber duplexer (such as circulator, WDM, etc.) Delay of time decoding circuit Therefore, the receiving link delay can be expressed as: ${\mathrm{\τ}}_i^R={\mathrm{\τ}}_{\mathrm{E.}\mathrm{D.}i}^R+{\mathrm{\τ}}_{Ti}^R.$

The present invention respectively measures the asymmetry of the time delay of the receiving link of the two-way time comparison system (denoted as device A and device B) by combining the time delay measurement method (that is, the time delay of the receiving link between the two devices Difference, ) and the asymmetry of the transmission link delay (that is, the delay difference of the transmission link between two devices, ). On this basis, the asymmetry of the time delay of the two-fiber two-way time comparison equipment is further calibrated ${\mathrm{\Δ\τ}}_{AB}={\mathrm{\Δ\τ}}_{AB}^T-{\mathrm{\Δ\τ}}_{AB}^R.$

Concrete technical solution of the present invention is as follows:

A method for calibrating time delay asymmetry of high-precision optical fiber two-way time comparison equipment is characterized in that the method includes the following steps:

①Using time-frequency reference, cable, optical fiber, optical fiber two-way time comparison and calibration equipment, high-precision delay test equipment, the first equipment to be calibrated and the second equipment to be calibrated to establish an optical fiber two-way time comparison equipment delay calibration system;

② Calibrate the receiving link delay difference between optical fiber two-way time comparison equipment;

③ Calibrate the receiving link delay difference between optical fiber two-way time comparison equipment;

④ Calibrate the time delay asymmetry between optical fiber two-way time comparison equipment.

Described step 1. establishes the optical fiber two-way time comparison equipment delay calibration system, including the first time-frequency reference, the second time-frequency reference, multiple cables, multiple optical fibers, the first optical fiber two-way time comparison calibration equipment, the second Optical fiber two-way time comparison and calibration equipment, first high-precision time delay testing equipment, second high-precision time delay testing equipment, optical fiber two-way time comparison equipment i (i=A, B) to be calibrated;

The first output end of the first time-frequency reference is connected to the first input end of the first high-precision delay test equipment through a cable, and the second output end of the first time-frequency reference is connected to the first optical fiber through a cable The input end of the two-way time comparison and calibration equipment is connected, and the output end of the first optical fiber two-way time comparison and calibration equipment is connected to the input end of the optical fiber two-way time comparison equipment i (i=A, B) to be calibrated via an optical fiber. The output end of the optical fiber bidirectional time comparison device i (i=A, B) to be calibrated is connected to the second input end of the first high-precision time delay testing device through a cable;

The first output end of the second time-frequency reference is connected to the first input end of the second high-precision time-delay test equipment through a cable, and the second output end of the second time-frequency reference is connected to the device to be calibrated through a cable. The input end of the optical fiber two-way time comparison device i (i=A, B) is connected, and the optical fiber two-way time comparison device i (i=A, B) to be calibrated is connected with the second optical fiber two-way time comparison calibration device through the optical fiber The input end is connected, and the output end of the second optical fiber bidirectional time comparison calibration device is connected to the second input end of the second high-precision time delay testing device through a cable.

The step 2. calibrates the receiving link delay difference between optical fiber two-way time comparison devices, specifically including the following steps;

Step 2-1. The timing information output by the first time-frequency reference is divided into two channels: one channel of timing information is input to the high-precision delay test equipment through the cable; the other channel of timing information is input into the first optical fiber two-way time comparison and calibration device through the cable The optical signal carrying timing information output by the first optical fiber two-way time comparison calibration device is input to the optical fiber two-way time comparison device i (i=A, B) to be calibrated through the optical fiber, and the optical fiber two-way time comparison to be calibrated The timing information output by device i is input to the high-precision delay test equipment through the cable;

Step 2-2. When the optical fiber bidirectional time comparison device i to be calibrated is the first device to be calibrated:

The timing information output by the first time-frequency reference measured by the first high-precision time-delay testing equipment is composed of cables, the transmission link of the first optical fiber two-way time comparison calibration equipment, optical fibers, the receiving link of the first equipment to be calibrated, and cables. The delay difference between the one-way time transfer link and the timing information output by the first time-frequency reference input to the high-precision delay test equipment through the cable

Step 2-3. When the optical fiber bidirectional time comparison device i to be calibrated is the second device to be calibrated:

The timing information output by the first time-frequency reference measured by the first high-precision time-delay test equipment is composed of cables, the transmission link of the first optical fiber two-way time comparison calibration equipment, optical fibers, the receiving link of the second equipment to be calibrated, and cables. The delay difference between the one-way time transfer link and the timing information output by the first time-frequency reference input to the high-precision delay test equipment through the cable

Step 2-4. Calculate the receiving link delay difference between optical fiber two-way time comparison devices The formula is as follows:

${\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; .</span>$

The step ③ calibrates the receiving link delay difference between the optical fiber two-way time comparison equipment, including the following steps:

Step 3-1. The timing information output by the second time-frequency reference is divided into two channels: one channel of timing information is input to the second high-precision delay test equipment through the cable, and the other channel of timing information is input through the cable to the optical fiber bidirectional time ratio to be calibrated For equipment i (i=A, B), the optical signal carrying timing information output by the optical fiber two-way time comparison device i to be calibrated is input to the second optical fiber two-way time comparison calibration device through the optical fiber, and the second optical fiber two-way time comparison The timing information output by the calibration equipment is input to the second high-precision delay test equipment through the cable;

Step 3-2, when the optical fiber two-way time comparison device i to be calibrated is the first device to be calibrated, the second high-precision delay test device measures the timing information output by the second time-frequency reference through the cable, the first The sending link of the equipment to be calibrated, the optical fiber, and the second optical fiber are compared with the receiving link and the cable of the calibration equipment to form a one-way time transfer link and the timing signal output by the second time-frequency reference is input to the second high-level through the cable. Delay difference of precision delay test equipment

Step 3-3, when the optical fiber two-way time comparison device i to be calibrated is the second device to be calibrated, the second high-precision delay test device measures the timing information output by the second time-frequency reference through the cable, the first The two-way time comparison of the transmission link of the equipment to be calibrated, the optical fiber, and the second optical fiber The receiving link and cable of the calibration equipment constitute a one-way time transfer link and the timing signal output by the second time-frequency reference is input to the second high-level through the cable. Delay difference of precision delay test equipment

4) Calculate the receiving link delay difference between optical fiber two-way time comparison equipment The formula is as follows:

${\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; .</span>$

The step ④ calibrates the time delay asymmetry Δτ _AB between the optical fiber two-way time comparison equipment, the formula is as follows

${\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}$

in, is the delay difference of the sending link, is the delay difference of the receiving link.

Compared with the prior art, the present invention can not only easily and conveniently calibrate the asymmetry of time delay between optical fiber two-way time comparison equipment, but also can calibrate the time delay asymmetry of any time-frequency equipment, and can effectively overcome The impact of different fiber or cable delays on accuracy.

Description of drawings

Figure 1 Schematic diagram of receiving link delay difference calibration;

Fig. 2 Schematic diagram of calibration of delay difference of sending link.

detailed description

A specific implementation example of the present invention is given below in conjunction with the accompanying drawings. This embodiment is carried out on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific work flow are given, but the protection scope of the present invention is not limited to the following embodiments.

Figure 1 is a schematic diagram of the calibration of the receiving link delay difference, which mainly consists of the first time-frequency reference H ₁ , the first optical fiber two-way time comparison calibration equipment C ₁ , and the optical fiber two-way time comparison equipment i to be calibrated (i=A, B ), the first high-precision time delay measurement device M ₁ , cables and optical fibers. Timing information output by the first time-frequency reference H ₁ (such as various atomic clocks) is divided into two channels. One channel of timing information is input to the _first high-precision delay test equipment M1 (such as time interval measuring instrument, oscilloscope, etc.) through the cable 1-1; the other channel of timing information is input to the first optical fiber two-way time comparison and calibration through the cable 1-2 Device C ₁ , the optical signal carrying timing information output by the first optical fiber bidirectional time comparison calibration device C ₁ is input to the optical fiber bidirectional time comparison device i (i=A, B) to be calibrated through the optical fiber 1-3, and the device i The output timing information is input to the first high precision time delay measuring device M ₂ through cables 1-4. When the optical fiber bidirectional time comparison device i to be calibrated is device A, the first high-precision delay test device M ₁ measures the timing information (such as 1pps) output by the first time-frequency reference H ₁ through the cable 1-2, the first The sending link of optical fiber two-way time comparison calibration equipment C ₁ , the receiving link of optical fiber 1-3, equipment A and cable _1-4 constitute the timing signal ( Such as 1pps) through the cable 1-1 input to the delay difference of the _first high-precision delay test equipment M1: When the optical fiber bidirectional time comparison device i to be calibrated is device B, measure the timing information (such as 1pps) output by the first time-frequency reference H ₁ through the cable 1-2, the first optical fiber bidirectional time comparison calibration device C ₁ The timing signal (such as 1pps) output by the transmission link, optical fiber 1-3, the receiving link of equipment B and the one-way time transfer link formed by the cable 1-4 and the first time-frequency reference H ₁ is input through the cable 1-1 The delay difference to the _first high-precision delay test equipment M1: Will and The measured results are subtracted to obtain the delay difference between devices A and B receiving links

Figure 2 is a schematic diagram of the calibration of the transmission link delay difference, which mainly consists of the second time-frequency reference H ₂ , the second optical fiber two-way time comparison calibration equipment C ₂ , and the optical fiber two-way time comparison equipment i to be calibrated (i=A, B ), the second high-precision time delay measurement device M ₂ , cables and optical fibers. The timing information output by the second time-frequency reference H ₂ (such as various atomic clocks) is divided into two channels and one timing information is input to the second high-precision time delay testing equipment M ₂ (such as time interval measuring instrument, oscilloscope, etc.) through the cable 2-1. ). Another way of timing information is input to the optical fiber two-way time comparison device i (i=A, B) to be calibrated through the cable 2-2, and the optical signal carrying the timing information output by i is input to the second optical fiber two-way time comparison device through the optical fiber 2-3 Compare calibration equipment C ₂ . The timing information output by C ₂ is input to the second high-precision time delay testing device M ₂ through the cable 2-4. When the optical fiber bidirectional time comparison device i to be calibrated is device A, the second high-precision delay test device M ₂ measures the timing information (such as 1pps) output by the second time-frequency reference H ₂ through the cable 2-2, device A _The timing signal ₍ Such as 1pps) through the cable 2-1 input to the delay difference of the second high-precision delay test equipment M ₂ : When the optical fiber bidirectional time comparison device i to be calibrated is B, the second high-precision time delay testing device M ₂ measures the timing information (such as 1pps) output by the second time-frequency reference H ₂ through the cable 2-2 and the device B. Sending link, optical fiber 2-3, the receiving link of the second optical fiber two-way time comparison calibration equipment C ₂ and cable _2-4 constitute the timing signal (as 1pps) through the cable 2-1 input to the delay difference of the second high-precision delay test equipment M ₂ : the above and Subtract the measured results in to obtain the delay difference between the transmission links of devices A and B

The delay difference of the sending link will be calibrated Delay difference between link and receiving link Obtain the asymmetry of the time delay of the two-fiber two-way time comparison equipment by subtraction

Claims (4)

1. A method for calibrating time delay asymmetry of high-precision optical fiber two-way time comparison equipment, is characterized in that, the method comprises the steps: ①Using time-frequency reference, cable, optical fiber, optical fiber two-way time comparison and calibration equipment, high-precision delay test equipment, the first equipment to be calibrated and the second equipment to be calibrated to establish an optical fiber two-way time comparison equipment delay calibration system; the optical fiber Two-way time comparison equipment delay calibration system, including the first time-frequency reference, the second time-frequency reference, multiple cables, multiple optical fibers, the first optical fiber two-way time comparison calibration equipment, and the second optical fiber two-way time comparison calibration equipment , the first high-precision time delay testing equipment, the second high-precision time delay testing equipment, the optical fiber two-way time comparison equipment i (i=A, B) to be calibrated; The first output end of the first time-frequency reference (H ₁ ) is connected to the first input end of the first high-precision delay test equipment (M ₁ ) via a cable (1-1), and the first time-frequency The second output end of the frequency reference (H ₁ ) is connected to the input end of the first optical fiber two-way time comparison and calibration equipment (C ₁ ) through the cable (1-2), and the first optical fiber two-way time comparison calibration equipment (C ₁ ) output end is connected with the input end of the optical fiber two-way time comparison device i (i=A, B) to be calibrated through the optical fiber (1-3), and the optical fiber two-way time comparison device i (i=A, B) to be calibrated is connected The output end of B) is connected to the second input end of the first high-precision time delay testing device (M ₁ ) via a cable (1-4); The first output end of the second time-frequency reference (H ₂ ) is connected to the first input end of the second high-precision delay test equipment (M ₂ ) via a cable (2-1), and the second time-frequency The second output end of the frequency reference (H ₂ ) is connected to the input end of the optical fiber two-way time comparison device i (i=A, B) to be calibrated via the cable (2-2), and the optical fiber two-way time comparison device to be calibrated Device i (i=A, B) is connected to the input end of the second optical fiber two-way time comparison and calibration device (C ₂ ) via an optical fiber (2-3), and the second optical fiber two-way time comparison and calibration device (C ₂ ) The output end is connected to the second input end of the second high-precision time delay testing device (M ₂ ) via a cable (2-4); ② Calibrate the receiving link delay difference between optical fiber two-way time comparison equipment; ③ Calibrate the transmission link delay difference between optical fiber two-way time comparison equipment; ④ Calibrate the time delay asymmetry between optical fiber two-way time comparison equipment. 2. The high-precision optical fiber two-way time comparison device delay asymmetry calibration method according to claim 1, characterized in that, described step 2. calibrates the receiving link time delay between the optical fiber two-way time comparison device Poor, specifically include the following steps; Step 2-1, the timing information output by the first time-frequency reference (H ₁ ) is divided into two paths: one path of timing information is input to the first high-precision time delay testing equipment (M ₁ ) through the cable (1-1); the other path The timing information is input to the first optical fiber two-way time comparison and calibration device (C ₁ ) through the cable (1-2), and the optical signal carrying the timing information output by the first optical fiber two-way time comparison and calibration device (C ₁ ) passes through the optical fiber ( 1-3) input to the optical fiber two-way time comparison device i (i=A, B) to be calibrated, the timing information output by the optical fiber two-way time comparison device i to be calibrated is input to the first High-precision delay test equipment (M ₁ ); Step 2-2. When the optical fiber bidirectional time comparison device i to be calibrated is the first device to be calibrated (A): The first high-precision delay test equipment (M ₁ ) measures the transmission of the timing information output by the first time-frequency reference (H ₁ ) through the cable (1-2) and the first optical fiber two-way time comparison and calibration equipment (C ₁ ). The timing of the one-way time transfer link composed of the link, the optical fiber (1-3), the receiving link of the first equipment to be calibrated (A) and the cable (1-4) and the output of the first time-frequency reference (H ₁ ) The delay difference of information input to the first high-precision delay test equipment (M ₁ ) through the cable (1-1) Step 2-3, when the optical fiber bidirectional time comparison device i to be calibrated is the second device to be calibrated (B): The first high-precision delay test equipment (M ₁ ) measures the transmission of the timing information output by the first time-frequency reference (H ₁ ) through the cable (1-2) and the first optical fiber two-way time comparison and calibration equipment (C ₁ ). The timing of the one-way time transfer link composed of the link, the optical fiber (1-3), the receiving link of the second equipment to be calibrated (B) and the cable (1-4) and the output of the first time-frequency reference (H ₁ ) The delay difference of information input to the first high-precision delay test equipment (M ₁ ) through the cable (1-1) Step 2-4. Calculate the receiving link delay difference between optical fiber two-way time comparison devices The formula is as follows: ${\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; .</span>$ 3. The high-precision optical fiber two-way time comparison device delay asymmetry calibration method according to claim 1, characterized in that, described step 3. calibrates the transmission link time delay between the optical fiber two-way time comparison devices Poor, including the following steps: Step 3-1, the timing information output by the second time-frequency reference (H ₂ ) is divided into two paths: one path of timing information is input to the second high-precision time delay testing equipment (M ₂ ) through the cable (2-1), and the other path The timing information is input to the optical fiber two-way time comparison device i (i=A, B) to be calibrated through the cable (2-2), and the optical signal carrying the timing information output by the optical fiber two-way time comparison device i to be calibrated passes through the optical fiber ( 2-3) input to the second optical fiber two-way time comparison and calibration device (C ₂ ), the timing information output by the second optical fiber two-way time comparison and calibration device (C ₂ ) is input to the second high-precision Latency test equipment (M ₂ ); Step 3-2. When the optical fiber bidirectional time comparison device i to be calibrated is the first device to be calibrated (A): The second high-precision time delay testing device (M ₂ ) measures the timing information output by the second time-frequency reference (H ₂ ) through the cable (2-2), the transmission link of the first equipment to be calibrated (A), and the optical fiber ( 2-3), the receiving link and cable (2-4) of the second optical fiber two-way time comparison and calibration device (C ₂ ) constitute a one-way time transfer link and the timing signal output by the second time-frequency reference (H ₂ ) The delay difference input to the second high-precision delay test equipment (M ₂ ) through the cable (2-1) Step 3-3. When the optical fiber bidirectional time comparison device i to be calibrated is the first device to be calibrated (B): The second high-precision time delay testing device (M ₂ ) measures the timing information output by the second time-frequency reference (H ₂ ) through the cable (2-2), the transmission link of the second equipment to be calibrated (B), and the optical fiber ( 2-3), the receiving link and cable (2-4) of the second optical fiber two-way time comparison and calibration device (C ₂ ) constitute a one-way time transfer link and the timing signal output by the second time-frequency reference (H ₂ ) The delay difference input to the second high-precision delay test equipment (M ₂ ) through the cable (2-1) Step 3-4. Calculate the transmission link delay difference between optical fiber two-way time comparison devices The formula is as follows: ${\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; .</span>$ 4. The method for calibrating time delay asymmetry of high-precision optical fiber two-way time comparison equipment according to claim 1, characterized in that, described step ④ calibrates the time delay asymmetry between optical fiber two-way time comparison equipment Δτ _AB , the formula is as follows ${\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}$ in, is the delay difference of the sending link, is the delay difference of the receiving link.