Full-distributed optical fiber strain and vibration sensor based on coherent heterodyne detection

Abstract

The invention relates to a full-distributed optical fiber strain and vibration sensor based on coherent heterodyne detection, which comprises a laser (1), a coupler, a pulse modulation module, a programming gain amplifier (4), an optical amplifier, a circulator (6), a sensing fiber (7), a polarization-preserving fiber (8), the coupler, a balancing photoelectric detector (10), a reversal switch, a mixer, a microwave source, a band-pass filter, and a signal processing unit, wherein the continuous light output by the laser (1) is divided into two paths after passing through the coupler (2); an output end of the balancing photoelectric detector is connected to the reversal switch; the reversal switch is switched to a channel 1 and a channel 2; when the channel 1 is switched on, the system utilizes the Brillouin optical fiber time domain reflection to measure; and when the programming gain amplifier (4) is closed and the channel 2 is switched on, the system utilizes the polarization optical time-domain reflection to measure. By using the full-distributed optical fiber strain and vibration sensor provided by the invention, the full-distributed measurement for strain as well as the weak vibration and the full-distributed measurement for vibration can be performed on a single optical fiber.

Description

technical field [0001] The present invention is an optical fiber sensing method and equipment 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 Fully distributed optical fiber strain and vibration sensing technology using 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 sensors have the advantages of high ...

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Problems solved by technology

However, since the strain on the optical fiber is not in a one-to-one correspondence with the change of the polarization state, and the POTDR technology mostly uses the method of comparing with the previous measurement to judge the state of the optical fiber, it is difficult for the POTDR technology to accurately measure the static strain and the larger strain. detection

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