A tapered optical fiber flow velocity sensor based on fbg written by femtosecond laser

Abstract

The invention provides a tapered optical fiber flow velocity sensor based on femtosecond laser writing FBG, wherein the sensing head is made of femtosecond laser writing FBG on the tapered optical fiber by a point-by-point method. It is characterized in that: the diameter of the cone waist is 9-11 μm, the length of the cone waist is 5-10mm, the inclination angle of the end of the cone waist is 7.5°-8.5°, the length of the FBG is 2-5mm, and the Bragg wavelength is 1450-1560nm. Using the method of intensity demodulation, the optical signal is converted into an electrical signal, the functional relationship between the flow velocity and the voltage is established, and the flow velocity is inverted by monitoring the change of the output voltage, so as to achieve the sensing measurement of the flow velocity. The invention has the advantages of simple structure, small volume, anti-electromagnetic interference, corrosion resistance, high temperature resistance, high sensitivity and can be used for distributed sensing, etc., and can be applied to flow velocity measurement of microfluidic liquid and air.

Description

technical field [0001] The invention provides a tapered optical fiber flow velocity sensor based on femtosecond laser writing FBG, which belongs to the technical field of optical fiber sensing. Background technique [0002] Flow velocity describes the displacement of liquid or gas per unit time, which is an important parameter in practical applications such as energy and metering, industrial production, and medical treatment. The earliest used flow rate sensor is the mechanical rotor type, although its technology is relatively mature, but the measurement accuracy is low. Ultrasonic flow meters, electromagnetic flow meters and laser Doppler flow meters have good measurement accuracy, but the equipment is expensive, the measurement range is small, and they are easily interfered by electromagnetic waves. [0003] In recent years, fiber optic sensors have provided a new development direction for flow velocity measurement by virtue of their advantages of high sensitivity, small ...

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Problems solved by technology

For example, Fan Jiancheng and others proposed an optical fiber through-hole flow rate propeller sensor, which has a low starting flow rate, but the structure is complex and the measurement range is small; Li Yijun et al. designed a reflective intensity modulation optical fiber sensor by using a micro-pressure probe and a diaphragm. The flow velocity measurement in the range of 0-0.8m / s is well realized, but the design of the sensor micro-probe is not ideal, and the temperature compensation is poor; Chen Jianjun and others have designed a fiber Bragg grating (FBG) and a Venturi tube. High-sensitivity flow rate sensor, this sensor has high sensitivity, but the dynamic sensing range is narrow; the flow rate sensor designed by Yang Shulian et al. based on the double FBG cantilever beam structure of equal strength can realize temperature compensation well, but the sensor is based on the Venturi tube design, the structure Complicated, it is not easy to measure the fluid velocity in underground fractures

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