Optical fiber time delay measurement method and device based on single optical frequency comb interference

Abstract

The invention discloses an optical fiber time delay measurement method based on single optical frequency comb interference, which divides the optical carrier output by a narrow linewidth laser into two paths, wherein one optical carrier is modulated into an optical frequency comb signal by an optical frequency comb modulator , sent to the interferometer connected to the optical fiber to be tested, and another optical carrier for frequency shift processing; after the frequency shifted optical carrier is coupled with the optical signal output by the interferometer, photoelectric detection is performed to obtain a microwave signal carrying time delay information ; Extract the spectrum information of the microwave signal, and then extract the free spectrum range of the interference spectrum, and calculate the time delay of the optical fiber to be tested according to the free spectrum range of the interference spectrum. The invention also discloses an optical fiber time delay measurement device based on single optical frequency comb interference. Compared with the prior art, the invention has the advantages of high measurement stability, fast measurement speed, simple structure and low implementation cost.

Description

technical field [0001] The invention relates to a method for measuring optical fiber time delay, which belongs to the technical field of optical measurement. Background technique [0002] Delay is a basic parameter in signal generation, transmission, control and processing. With the rapid development of optical fiber electronic information systems, the rapid and stable measurement and control of time delay in optical fiber links has become an optically controlled phased array, distributed The key to the research and application of high-performance information systems such as radar networks and optical fiber time-frequency transmission. [0003] There are three commonly used optical fiber delay measurement methods: pulse method, phase push method, and frequency-sweeping interferometry. The pulse method is also called the time-domain method. The time delay of the optical fiber to be tested is obtained by directly recording the time interval between the transmitted optical pul...

AI Technical Summary

Problems solved by technology

This type of measurement method needs to lock the two optical combs to avoid drift caused by environmental influences, the structure is complex and the cost is high, and it can only be applied to the absolute distance measurement of space light, and the measurement range is relatively small

The single optical comb also shows a good advantage in space ranging. The Korea Institute of Science and Technology (KAIST) uses a Sagnac interferometer structure combined with phase-locked feedback, and uses a mode-locked laser to generate an optical frequency comb signal to measure the microwave The time delay difference between the signal and the optical frequency comb signal has achieved sub-femtosecond delay measurement accuracy (Na Y, Jeon C-G, Ahn C, et al. Ultrafast, sub-nanometre-precision and multifunctional time-of-flight detection [J].Nature Photonics,2020,14(6):355-360.) Due to the periodicity of optical frequency comb signals and microwave signals, the measurement range of this type of measurement method is relatively small, only at the millimeter level

In addition, due to the adoption of a feedback mechanism, a glass slide and a Faraday rotating mirror need to be added to the Sagnac interference loop to achieve a π / 2 phase difference. The position of the slide is easy to change, and the calibration of the slide needs to be adjusted before measurement, which is difficult to operate; the interference ring The high-cost polarization-maintaining fiber must also be used in the path; in addition, in order to achieve stable measurement results, the solution also needs to use high-quality voltage-controlled oscillators and mode-locked lasers

In summary, the single-comb delay measurement system has a complex structure, high equipment requirements, difficult operation, and small measurement range. Currently, it can only be used for spatial light measurement, and is not suitable for delay measurement in optical fibers.

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