Multi-modes Fiber Ring Laser Sensor Combining One Fiber Bragg Grating Reflector

A multi-longitudinal-mode fiber ring laser sensor is firstly proposed and experimentally demonstrated. Beat frequencies between any two longitudinal modes are used as sensing signal. The core component of the system is a multi-longitudinal-mode fiber ring cavity laser sensor based on beat frequency demodulation method. The theory of beat signal generation and strain measurement are discussed in detail. The beat frequency shift caused by the strain applied on the cavity is demodulated using spectrum analyze. Experimental results shown the strain accuracy of the laser sensor is 1.3 με and the resolution of the strain is 1.6 kHz/με at measuring frequency of 2019 MHz. The noise effect of self-heating in the cavity is 0.149 kHz/mW. The SNR of the sensor system is higher than 61 dB. The simple laser sensor has ultra-stable signal. The usage of only one fiber laser and one demodulation system makes the system simple, cost-effective and portable. Copyright © 2014 IFSA Publishing, S. L.