A distributed optical fiber sensing system and sensing method based on multi-frequency conversion ofdr

Abstract

The embodiment of the invention discloses a distributed optical fiber sensing system and method based on a multi-variable frequency OFDR. A narrow linewidth variable frequency laser generates continuous variable frequency light which is divided into detection light and reference light through a coupler, the detection light is subjected to secondary frequency modulation through an electrooptical modulator, through control of a computer and change of secondary frequency modulation rate, the detection light enters a sensing optical fiber after being amplification by an EDFA, a calibration part isarranged at the tail portion of the sensing optical fiber, the reference light generates interference with Rayleigh scattering light at a back direction to form a detection result having a pluralityof variable frequency carriers, and the detection result is detected by a balance detector and is converted to digital signals. The digital signals are subjected to sectional and time-frequency analysis to obtain an oblique line boundary frequency spectrum, the frequency domain is converted to a space domain, the reflection peak features of the calibration part is employed to perform realignment of the space sub domains so as to obtain the scattering light intensity distribution of the whole sensing range. The secondary frequency modulation and the method for solving the oblique line boundaryfrequency spectrum are employed to achieve separation of the overlapping space signals and exponentially enlarge the sensing range.

Description

technical field [0001] The invention relates to the field of optical fiber sensing, in particular to a distributed optical fiber sensing system and sensing method based on multi-frequency conversion OFDR. Background technique [0002] Distributed optical fiber sensing uses the backscattered light in the optical fiber to realize the measurement of the physical quantity of the optical fiber. It has the characteristics of accurate positioning, high reliability, and multi-point simultaneous detection. It has a wide range of applications in optical cable status monitoring and long-distance stress temperature detection. application. [0003] Distributed optical fiber sensing can be divided into optical time domain reflectometry (OTDR) and optical frequency domain reflectometry (OFDR) according to the difference of detected light. Among them, OTDR technology injects a pulsed detection light into the optical fiber, and the photodetector at the head end of the optical fiber will rec...

AI Technical Summary

Problems solved by technology

[0004] In summary, in the existing technical solutions, OFDR technology has higher spatial resolution, but its sensing distance is short, and its application is limited

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