Conical optical fiber flow velocity sensor based on femtosecond laser inscribing FBG

Abstract

The invention provides a conical optical fiber flow velocity sensor based on femtosecond laser inscribing FBG. A sensing head is manufactured by inscribing FBG on a conical optical fiber through femtosecond laser in a point-by-point method. The sensor is characterized in that the diameter of the cone waist is 9-11 [mu] m, the length of the cone waist is 5-10 mm, the inclination angle of the tail end of the cone waist is 7.5-8.5 degrees, the length of the FBG is 2-5 mm, and the Bragg wavelength is 1450-1560 nm. An optical signal is converted into an electric signal by using an intensity demodulation method, a function 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 that the sensing measurement of the flow velocity is achieved. The sensor has the advantages of being simple in structure, small in size, resistant to electromagnetic interference, corrosion and high temperature, high insensitivity, capable of being used for distributed sensing and the like, and can be applied to flow velocity measurement of micro-flow 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 flow rate sensor used was a mechanical rotor type. Although its technology is relatively mature, its 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 susceptible to electromagnetic wave interference. [0003] In recent years, fiber optic sensors have provided a new development direction for flow velocity measurement due to their advantages of high sensitivity, small size ...

AI Technical Summary

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

Images