Non-scanning demodulation system based on optical fiber Fabry-Perot sensor

Abstract

The invention relates to a non-scanning demodulation system based on an optical fiber Fabry-Perot sensor, whichbelongs to the technical field of optical fiber sensing. The system comprises a positivelens, a first free-form surface reflector, a second free-form surface reflector, an optical wedge, a plano-convex cylindrical lens, a linear array CCD and a data processor. The positive lens is used for receiving light with cavity length information obtained from the optical fiber Fabry-Perot sensor, and the light is emitted to the positive lens through the optical fiber and is diffused into parallel light; the first free-form surface reflector is used for receiving the parallel light diverged by the positive lens and converting the parallel light into flat-topped light; the second free-form surface reflector is used for collimating the emergent direction of the flat-topped light to ensure that the signal light incident to the optical wedge is perpendicular to the surface of the second free-form surface reflector; the plano-convex cylindrical lens is used for converting the rectangular light spot transmitted by the optical wedge into one-dimensional linear light; and the linear array CCD is used for detecting the one-dimensional linear light passing through the plano-convex cylindrical lens and outputting a voltage signal. The signal contrast can be effectively demodulated, and thedemodulation precision of a demodulation system can be improved.

Description

Technical field [0001] The invention belongs to the technical field of optical fiber sensing, and relates to a non-scanning demodulation system based on an optical fiber Fabry Perot sensor. Background technique [0002] Optical Fiber Fabry-Perot Sensor (Optical Fiber Fabry-Perot Sensor, referred to as optical fiber Fabry-Perot sensor) is a mature technology and widely used interference optical fiber sensor. It has the advantages of simple structure, good stability, small size, light weight, high sensitivity, and strong anti-electromagnetic interference ability. It is widely used in bridge structure health monitoring, civil engineering, large-scale civil building safety monitoring and other fields. [0003] The core of the optical fiber Fabry-Perot sensor is the fiber-optic Fabry-Perot cavity, which is to fix two lengths of optical fiber in the capillary, and ensure that the two ends are flat and parallel to each other, thereby forming a microcavity with a cavity length of L. figure...

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Problems solved by technology

[0006] The above two systems use optical wedges to realize hardware-related demodulation, without moving parts, and have good stability; but in the demodulation module, there are only concave cylindrical mirrors or cylindrical lenses to shape the outgoing light of the sensor, and the incident light on the surface of the optical wedge The signal light energy distribution is uneven and the angle is not vertical, which has a certain impact on the contrast of the demodulated signal. The specific problems are:

[0009] To sum up, for the demodulation system, the incident light whose angle is perpendicular to the surface of the optical wedge can generate interference fringes on the surface of the optical wedge, which increases the effective contrast of the demodulated signal, while the light whose incident angle is not perpendicular to the optical wedge is received by the CCD , will only increase the DC component in the demodulated signal, that is, the noise floor, and will not help the cavity length demodulation

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