Dark field detection based optical-fiber macrobending coupling structure liquid-level probe

Abstract

The invention discloses a dark field detection based optical-fiber macrobending coupling structure liquid-level probe. The liquid level sensing principle based on 'CMFTIR (cladding mode frustrated total internal reflection) effect' is proposed for the first time and applied successfully. By means of macrobending, mode field distribution in optical fibers is changed, ratio of cladding mode energy in the optical fibers is increased, and the CMFTIR effect is enhanced; meanwhile, due to macrobending radiation effect, macrobending coupling between the two optical fibers is realized; by means of macrobending coupling, a sensing signal is transferred to a dark field, modulation depth is increased during coupling, higher cladding mode energy ratio can be obtained in the passive optical fiber, and the CMFTIR effect is further enhanced; meanwhile, stability of the coupling structure and consistency of sensors are guaranteed, signal to noise ratio of increased by detection of effectiveness of dark field signals, the liquid-level probe is low in cost and power consumption and high in performance, and discrimination is higher than 4dB.

Description

technical field The invention relates to a liquid level probe, in particular to an optical fiber macrobend coupling structure liquid level probe based on dark field detection. Background technique In the field of petroleum, chemical and chemical production, the automatic detection of the liquid level of liquid chemicals is an important guarantee for safe operation; the monitoring of the fuel level during the operation of aircraft and ships also has a wide range of demands. At present, the traditional liquid level detection methods mainly include: mechanical float type, capacitive type, ultrasonic type, etc. Among them, mechanical float electronics have defects in automation and precision; capacitive sensors have certain safety hazards in flammable and explosive environments due to the introduction of electrical signals, and a large number of signal connection lines are very susceptible to electromagnetic interference; ultrasonic liquid Position sensors often have problems ...

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