A method and device for fiber delay measurement based on dual optical comb linear optical sampling

Abstract

The application discloses a kind of based on double optical comb linear optical sampling optical fiber time delay measurement method and device, for solving the problem of high-precision optical fiber time delay precision measurement in information science and optical fiber communication, its characteristics are using two optical comb modules with small difference in repetition frequency, the optical comb signals generated by it are divided into a total of 4 optical comb signals after beam splitting;One optical comb signal generated by one optical comb module is divided into one after beam splitting, and the other optical comb module is divided into one after beam splitting to obtain an electrical signal by linear optical sampling;After linear optical sampling, the remaining 2 optical comb signals obtain another electrical signal;The time delay of the two electrical signals amplified by a fixed multiple is measured to calculate the time delay of the optical fiber to be measured.Compared with the prior art, the device has a simple structure, higher measurement accuracy and a large measurement range in theory, and has the prospect of integration and miniaturization, and is expected to have important applications in the fields of optical fiber sensing and precision measurement.

Description

Technical Field

[0001] This invention relates to the field of high-precision fiber optic delay measurement in information science and fiber optic communication, and particularly to a high-precision fiber optic delay measurement method based on dual-comb linear optical sampling. Background Technology

[0002] Optical fiber is one of the cornerstones of modern information science and communication technology. With the rapid development of communication technology, optical fiber networks are increasingly becoming a crucial infrastructure for various countries, inevitably involving the precise measurement of optical fiber length. In fact, since the speed of light in optical fiber is known, measuring the length of a segment of fiber is achieved by measuring the round-trip time of light within that segment. Therefore, accurately measuring the time difference between the emitted optical signal and the received reflected or scattered optical signal—that is, the fiber optic delay—has become a very important task.

[0003] Currently, the most widely used methods for measuring fiber length include optical time-domain reflectometry (OTDR) and optical frequency-domain reflectometry (OFDR). OTDR measures the fiber distance by coupling an optical pulse to one end of the fiber and receiving the Rayleigh, Brillouin, or Raman scattering signals generated during its propagation. The measurement time delay between the two events is then measured in the time or frequency domain. The accuracy of this method depends primarily on the pulse width, typically ranging from millimeters to meters. Another approach to measuring fiber length utilizes a frequency-shifted asymmetric Sagnac interferometer. The basic idea is that light of different frequencies propagating in the same fiber will produce different phase delays, and this phase delay difference, containing information about the fiber length, can be measured using an interferometer.

[0004] However, while the existing solutions can basically meet the needs of general industrial applications, their devices are still relatively complex and their accuracy is limited, making them insufficient for higher-precision scientific applications such as geodesy. Summary of the Invention

[0005] This invention proposes a high-precision fiber optic delay measurement method and apparatus based on dual-comb linear optical sampling. This method and apparatus differ from previous approaches in that they fully utilize the high coherence of the optical comb, achieving amplified measurement of minute fiber delays through linear optical sampling, while maintaining the simplicity of the apparatus and achieving high-precision measurement.

[0006] Optical combs, as frequency- and phase-stable mode-locked lasers, offer advantages such as high coherence and high signal-to-noise ratio, while linear optical sampling boasts high sensitivity and high sampling accuracy. Our proposed fiber optic time delay measurement device cleverly amplifies and measures minute fiber delays using a dual-optical-comb-based linear optical sampling method. Theoretically, amplifying these minute delays can yield higher measurement accuracy. This simple device shows promise for further integration and miniaturization, and its high measurement accuracy is expected to find significant applications in fiber optic sensing, precision measurement, and other fields.

[0007] The technical solution of this invention is as follows:

[0008] A high-precision fiber optic time delay measurement method based on dual-comb linear optical sampling includes the following steps:

[0009] 1) Select two optical combs to form the first optical comb module and the second optical comb module, respectively. The first optical comb module corresponds to a repetition frequency of f. r The second optical comb module corresponds to a repetition frequency of f. r +Δf r These two optical combs have a repetition rate difference Δf r .

[0010] 2) The electrical signal A generated by the clock module is connected to the first signal source module for clock synchronization of the first signal source module;

[0011] 3) The electrical signal B generated by the clock module is connected to the second signal source module for clock synchronization of the second signal source module;

[0012] 4) The electrical signal C generated by the first signal source module is connected to the first optical comb module and used as the repetition rate locking reference for the first optical comb module;

[0013] 5) The electrical signal D generated by the second signal source module is input to the second optical comb module as a reference for the repetition rate locking of the second optical comb module;

[0014] 6) The first optical comb module generates a first optical comb signal based on the electrical signal C and the received repetition frequency locking reference signal, which is then connected to the first beam splitter module to generate the third and fourth optical comb signals.

[0015] 7) The second optical comb module generates a second optical comb signal based on the electrical signal D and the received repetition frequency locking reference signal. This signal is then connected to the second beam splitter module to generate the fifth and seventh optical comb signals.

[0016] 8) The fifth optical comb signal is input to the fiber optic module under test, and after accumulating a time delay τ in the fiber optic module under test, the sixth optical comb signal is generated.

[0017] 9) The third optical comb signal and the sixth optical comb signal are respectively connected to the two input ports of the first linear optical sampling module to perform the linear optical sampling process;

[0018] 10) The fourth optical comb signal and the seventh optical comb signal are respectively connected to the two input ports of the second linear optical sampling module to perform a linear optical sampling process;

[0019] 11) The electrical signal E generated by the first linear optical sampling module and the electrical signal F generated by the second linear optical sampling module are both connected to the data processing module;

[0020] 12) The data processing module calculates the fiber delay τ to be measured; wherein, the data processing module first calculates a delay τ′ based on the received electrical signals E and F, and then calculates the delay τ′ according to the formula... The fiber delay τ is calculated.

[0021] The present invention also provides an optical fiber delay measurement device based on dual optical comb linear optical sampling, characterized in that it includes a clock module, a first signal source module, a second signal source module, a first optical comb module, a second optical comb module, a first beam splitter module, a second beam splitter module, a first linear optical sampling module, a second linear optical sampling module, a fiber under test module, and a data processing module.

[0022] The clock module is used to generate an electrical signal for clock synchronization of the first optical comb module and the second optical comb module, and to connect the electrical signal as electrical signal A to the first signal source module, and to connect the electrical signal as electrical signal B to the second signal source module.

[0023] After clock synchronization, the first signal source module generates an electrical signal C and connects it to the first optical comb module, which is used as the repetition rate locking reference signal of the first optical comb module.

[0024] After clock synchronization, the second signal source module generates an electrical signal D and connects it to the second optical comb module as a repetition rate locking reference signal for the second optical comb module.

[0025] The first optical comb module generates a first optical comb signal based on the electrical signal C and the received repetition frequency locking reference signal, and connects it to the first beam splitter module for beam splitting to generate a third optical comb signal and a fourth optical comb signal;

[0026] The second optical comb module generates a second optical comb signal based on the electrical signal D and the received repetition frequency locking reference signal, and connects it to the second beam splitter module for beam splitting to generate the fifth and seventh optical comb signals; the repetition frequency difference between the first and second optical comb modules is Δf. r ;

[0027] The fifth optical comb signal is used to access the fiber optic module under test, and is used to generate the sixth optical comb signal after time delay accumulation in the fiber optic module under test.

[0028] The first linear optical sampling module is used to perform linear optical sampling on the incoming third and sixth optical comb signals to obtain the fundamental frequency Δf. r The electrical signal E is input into the data processing module;

[0029] The second linear optical sampling module is used to perform linear optical sampling on the incoming fourth and seventh optical comb signals to obtain the fundamental frequency Δf. r The electrical signal F is input into the data processing module;

[0030] The data processing module is used to calculate the fiber delay τ to be measured based on the received electrical signals E and F.

[0031] Furthermore, the repetition frequency corresponding to the first optical comb module is f. r The second optical comb module corresponds to a repetition frequency of f. r +Δf r .

[0032] Furthermore, the data processing module first calculates a time delay τ′ based on the received electrical signals E and F, and then calculates the time delay τ′ according to the formula. The fiber delay τ is calculated.

[0033] Furthermore, frequency f r It has the same frequency as electrical signal C and electrical signal D.

[0034] Furthermore, Δf r =1kHz, f r =100MHz.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] (1) Compared with existing optical time-domain reflectometers and other fiber optic delay measurement schemes, this method adopts a different technical approach and makes full use of the high coherence of the optical comb. At the same time, through a linear optical sampling process, the micro-delay is amplified and measured, which theoretically has higher accuracy and can meet the needs of higher precision fiber optic delay measurement;

[0037] (2) The system is simple and easy to build. At the same time, the system has a compact structure and shows promise for further miniaturization, integration, and commercialization.

[0038] (3) Different optical comb modules with different repetition rates can be used as needed to obtain different amplification factors for fiber delay. The measurement accuracy of the system can be easily adjusted according to the requirements.

[0039] (4) This system has the advantages of high measurement accuracy and wide measurement range in fiber optic delay measurement. In the future, it can theoretically have an unlimited measurement range after being further combined with coarse measurement. Attached Figure Description

[0040] Figure 1 This is a system structure diagram of a high-precision fiber optic delay measurement device based on dual-comb linear optical sampling in this invention.

[0041] Figure 2 This is a schematic diagram of an embodiment of a high-precision fiber optic delay measurement device based on dual-comb linear optical sampling in this invention. Detailed Implementation

[0042] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings.

[0043] See appendix Figure 1 The device of the present invention includes a clock module, a first signal source module, a second signal source module, a first optical comb module, a second optical comb module, a first beam splitter module, a second beam splitter module, a first linear optical sampling module, a second linear optical sampling module, a fiber under test module, and a data processing module.

[0044] See appendix Figure 2 This method includes the following steps:

[0045] 1) The 10MHz sine wave signal generated by the clock module is used as electrical signal A and electrical signal B to be connected to the first signal source module and the second signal source module respectively to achieve clock synchronization;

[0046] 2) After clock synchronization, the first signal source module generates a 100MHz electrical signal C, which is connected to the first optical comb module and used as a reference signal for the repetition frequency locking of the first optical comb module.

[0047] 3) After clock synchronization, the second signal source module generates a 100MHz electrical signal D, which is connected to the second optical comb module and used as a reference signal for the repetition frequency locking of the second optical comb module.

[0048] 4) The repetition frequency of the first optical comb module is locked at f. r =100MHz, the generated first optical comb signal is connected to the first beam splitter module;

[0049] 5) The repetition frequency of the second optical comb module is locked to f. r +Δf r =100MHz+1kHz, and the generated second optical comb signal is connected to the second beam splitter module;

[0050] 6) The first beam splitter module splits the first optical comb signal into a third optical comb signal and a fourth optical comb signal;

[0051] 7) The second beam splitter module splits the second optical comb signal into the fifth optical comb signal and the seventh optical comb signal;

[0052] 8) The signal from the fifth optical comb is connected to the fiber optic module under test;

[0053] 9) The sixth optical comb signal output by the fiber optic module under test has an additional time delay τ compared to the fifth optical comb signal;

[0054] 10) The third optical comb signal and the sixth optical comb signal are input to the first linear optical sampling module to perform a linear optical sampling process;

[0055] 11) The fourth optical comb signal and the seventh optical comb signal are input into the second linear optical sampling module to perform a linear optical sampling process;

[0056] 12) The first linear optical sampling module outputs a linear optical sampling signal with a fundamental frequency of 1kHz, which is the electrical signal E;

[0057] 13) The second linear optical sampling module outputs a linear optical sampling signal with a fundamental frequency of 1kHz, which is the electrical signal F;

[0058] 14) Electrical signals E and F are input to the data processing module. After a linear optical sampling process, the time delays of electrical signals E and F are amplified to...

[0059]

[0060] 15) In the data processing module, select the second pulse of the acquired electrical signal E, perform Hilbert filtering to remove glitches and extract the amplitude, and then obtain the time t1 corresponding to the peak value through Gaussian fitting.

[0061] 16) In the data processing module, select the second pulse of the acquired electrical signal F, perform Hilbert filtering to remove glitches and extract the amplitude, and then obtain the time t2 corresponding to the peak value through Gaussian fitting.

[0062] 17) Within the data processing module, calculate the time delay τ′ of electrical signals E and F, which satisfies...

[0063] τ′=t1-t2;

[0064] 18) Within the data processing module, the time delay τ of the fiber under test is calculated and finally output through τ′, which satisfies...

[0065]

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention. The protection scope of the present invention should be determined by the claims.

Claims

1. A method for measuring the time delay of an optical fiber based on dual optical comb linear optical sampling, comprising the steps of: 1) a clock module generates an electrical signal, which is input into a first signal source module as electrical signal A for clock synchronization of the first signal source module, and which is input into a second signal source module as electrical signal B for clock synchronization of the second signal source module; 2) the first signal source module generates an electrical signal C after clock synchronization and inputs it into a first optical comb module as a repetition frequency locking reference signal for the first optical comb module; the second signal source module generates an electrical signal D after clock synchronization and inputs it into a second optical comb module as a repetition frequency locking reference signal for the second optical comb module; 4) the fifth optical comb signal is input into a to-be-measured optical fiber module to generate a sixth optical comb signal after time delay accumulation in the to-be-measured optical fiber module; 3) the first optical comb module generates a first optical comb signal based on the electrical signal C and the received repetition frequency locked reference signal and applies it to the first beam splitter module for splitting to produce a third optical comb signal and a fourth optical comb signal; the second optical comb module generates a second optical comb signal based on the electrical signal D and the received repetition frequency locked reference signal and applies it to the second beam splitter module for splitting to produce a fifth optical comb signal and a seventh optical comb signal; the repetition frequency difference between the first optical comb module and the second optical comb module is Δf r ; 6) a data processing module calculates the to-be-measured optical fiber time delay τ according to the received electrical signal E and electrical signal F. 5) the third optical comb signal and the sixth optical comb signal are respectively connected to two input ports of the first linear optical sampling module, linear optical sampling is performed, and an electrical signal E with a base frequency of Δf r is obtained and input into the data processing module; the fourth optical comb signal and the seventh optical comb signal are respectively connected to two input ports of the second linear optical sampling module, linear optical sampling is performed, and an electrical signal F with a base frequency of Δf r is obtained and input into the data processing module; The method comprises a clock module, a first signal source module, a second signal source module, a first optical comb module, a second optical comb module, a first beam splitter module, a second beam splitter module, a first linear optical sampling module, a second linear optical sampling module, a to-be-measured optical fiber module, and a data processing module.

2. The method of claim 1, wherein, The first optical comb module corresponds to a repetition frequency of f r The second optical comb module corresponds to a repetition frequency of f r + Δf r .

3. The method of claim 2, wherein, Frequency f r The same as the frequency of the electrical signal C, the electrical signal D.

4. The method of claim 3, wherein, Δf r = 1 kHz, f r = 100 MHz.

5. The method according to claim 2 or 3, characterized in that, The data processing module first calculates a time delay τ' according to the received electric signal E and electric signal F, and then calculates the fiber time delay τ according to the formula ​ 6. An optical fiber time delay measurement apparatus based on dual optical comb linear optical sampling, characterized in that, The clock module is used to generate an electrical signal for clock synchronization of the first optical comb module and the second optical comb module, and input the electrical signal into the first signal source module as electrical signal A and into the second signal source module as electrical signal B. The first signal source module generates an electrical signal C after clock synchronization and inputs it into the first optical comb module as a repetition frequency locking reference signal for the first optical comb module. The second signal source module generates an electrical signal D after clock synchronization and inputs it into the second optical comb module as a repetition frequency locking reference signal for the second optical comb module. The first optical comb module generates a first optical comb signal according to the electrical signal C and the received repetition frequency locking reference signal and inputs it into the first beam splitter module for beam splitting to generate a third optical comb signal and a fourth optical comb signal. The fifth optical comb signal is used to input into the to-be-measured optical fiber module to generate a sixth optical comb signal after time delay accumulation in the to-be-measured optical fiber module. The data processing module is used to calculate the to-be-measured optical fiber time delay τ according to the received electrical signal E and electrical signal F. The second optical comb module generates a second optical comb signal according to the electrical signal D and the received repetitive frequency locking reference signal and inputs the second optical comb signal into the second beam splitter module for beam splitting to generate a fifth optical comb signal and a seventh optical comb signal; the repetition frequency difference between the first optical comb module and the second optical comb module is Δf r ; ​ The first linear optical sampling module is configured to linearly optically sample the accessed third optical comb signal and the sixth optical comb signal to obtain an electrical signal E of the base frequency Δf and input the electrical signal E into the data processing module. r The first linear optical sampling module is configured to linearly optically sample the accessed third optical comb signal and the sixth optical comb signal to obtain an electrical signal E of the base frequency Δf and input the electrical signal E into the data processing module. The second linear optical sampling module is configured to linearly optically sample the accessed fourth optical comb signal and the seventh optical comb signal to obtain a base frequency Δf r telecommunication signal F and input the base frequency Δf telecommunication signal F into the data processing module. ​ 7. The optical fiber time delay measurement apparatus according to claim 6, wherein The first optical comb module corresponds to a repetition frequency of f r The second optical comb module corresponds to a repetition frequency of f r + Δf r .

8. The optical fiber time delay measurement apparatus according to claim 7, wherein, The data processing module first calculates a time delay τ' according to the received electric signal E and electric signal F, and then calculates the fiber time delay τ according to the formula ​ 9. The optical fiber time delay measurement apparatus according to claim 7 or 8, characterized by, Frequency f r The same as the frequency of the electrical signal C, the electrical signal D.

10. The optical fiber time delay measurement apparatus according to claim 9, wherein, Δf r = 1 kHz, f r = 100 MHz.

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