A fully distributed optical fiber strain and vibration sensing method and device based on orthogonal polarization state switching

Abstract

A fully-distributed optical fiber strain and vibration sensing device based on cross-polarization state changeover comprises a laser device (1), a polarization-maintaining coupler (2), a polarization-maintaining optical fiber, a pulse modulation module (3), an optical amplifier (4), a circulator (5), a sensing optical fiber (6), a polarization state changeover device (7), a coupler (8), a balancing photoelectric detector (9), a microwave source (10), a frequency mixer (11), a band-pass filter (12) and a signal acquiring and processing unit (13). Continuous light output by the laser device is divided into two paths through the polarization-maintaining coupler (2). All of connecting optical fibers in a first path output by the polarization-maintaining coupler (2) are polarization-maintaining optical fibers, pass through the polarization state changeover device and then are input into a first input end of the coupler (8). The polarization state changeover device has two states and respectively enables the polarization direction of output linearly polarized light to correspond to fast axes and slow axes of the polarization-maintaining optical fibers. The output end of the band-pass filter is connected to the signal acquiring and processing unit.

Description

technical field [0001] The invention relates to an optical fiber sensing device for fully distributed monitoring of strain and vibration, especially a combination of Brillouin Optical Time Domain Reflectometry (BOTDR) technology and Polarized Optical Time Domain Reflectometry (POTDR) technology, and adopts polarization Fully distributed optical fiber strain and vibration sensing technology with state switching device and coherent heterodyne detection. Background technique [0002] When the optical fiber is affected by the external environment (such as temperature, pressure, vibration, etc.), the parameters such as the intensity, phase, frequency, and polarization state of the transmitted light in the optical fiber will change accordingly. By measuring these parameters of the transmitted light, it can be obtained Corresponding physical quantity, this technology is called fiber optic sensing technology. [0003] Compared with traditional electrical sensors, optical fiber sens...

AI Technical Summary

Problems solved by technology

However, since the polarization state of light waves in ordinary single-mode optical fibers is difficult to keep constant for a long time, and the strain on the optical fiber is not in one-to-one correspondence with the change of polarization state, it is difficult for POTDR technology to detect quasi-static strain and large strain

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