Optical path delay rapid measurement apparatus based on frequency domain standing wave method

Abstract

The present invention discloses an optical path delay rapid measurement apparatus based on a frequency domain standing wave method. The apparatus modulates the repeat frequency of an optical frequencycomb signal, and the optical frequency comb signal passes through an optical path to be measured and a reference optical path so as to pass through an optical combining path, and the apparatus realizes high-precision and fast detection of an optical path delay by using the frequency domain standing wave method. The present invention adopts a repetitive-frequency rapid tunable optical frequency comb signal generator, which transmits an optical frequency comb signal with low phase noise and extremely low clock jitter, so that measurement accuracy is improved, and rapid measurement is implemented. At the same time, the present invention adopts the optical frequency comb signal as a carrier signal that occupies a certain spectral width in the optical domain. When an optical path difference between the reference optical path and the optical path to be measured satisfies a certain minimum value, two optical signals are non-coherent in the optical domain after being synthesized by a 3dB coupler. Therefore, the strength of the signal synthesized by the coupler is not affected by two random phase shifts, and a system anti-interference ability is strong.

Description

technical field [0001] The invention belongs to the technical field of optical time delay measurement, and in particular relates to a fast measuring device for optical time delay based on a frequency domain standing wave method. Background technique [0002] In optical communication, when a signal passes through a certain transmission system, delay will inevitably occur; because the delay characteristic of the system determines the distortion of the signal, the communication system has stricter requirements on delay. Many methods of measuring distance also rely on the measurement of time delay, so the accurate measurement of optical time delay has become a research hotspot. [0003] The current methods for measuring the time delay of optical signals in the transmission link are time domain pulse method, PGC (phase generated carrier technology) homodyne detection method, optical interferometry, optical frequency domain reflectometry (OFDR), microwave interference based on opt...

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Problems solved by technology

[0007] In OFDR technology, the linear sweep optical signal output by the light source is divided into two channels. One optical signal is reflected after passing through the reference optical path, and the other optical signal passes through the optical path to be tested. By using the Rayleigh scattering and Fresnel reflection existing in the optical path to be measured, if the propagation length If the coherence condition of light is satisfied, the signal light and reference light will be mixed on the photosensitive surface of the photodetector; the frequency of the photocurrent corresponding to the Rayleigh backscattering signal at any point on the optical fiber to be tested is proportional to at the location of the scattering point, that is, the propagation time delay of the optical path; the photodetector will output the photocurrent of the corresponding frequency, and its amplitude is proportional to the backscattering coefficient and the optical power at the fiber x, so as to obtain the scattering along the optical fiber to be measured Attenuation characteristics, at the same time, the time delay in the optical path to be tested can be deduced through the maximum value of the test frequency; this method has high measurement accuracy, but its measurement range is very small

[0008] OCMI technology uses a vector network analyzer to perform Fourier transform and cross-correlation operations on the radio frequency signal modulated on the optical carrier, and determines the time delay difference between the input signal and the output signal by the peak position of the correlation value; this method has high measurement accuracy and measurement The range is large, but its technical structure is complex and the measurement speed is slow

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