High-precision thermal-insensitive strain sensor based on optoelectronic oscillator.

A high-precision and thermal-insensitive strain sensor based on two self-starting optoelectronic oscillators (OEOs) is proposed and experimentally demonstrated. Two OEOs are grouped into a cross-referencing structure by dense wavelength division multiplexing (DWDM); the two OEOs have the same characters and they are placed in the same environment. In this frequency encoded strain sensor, it converts the strain information of the single mode fiber to the frequency information, and the frequency information is acquired by measuring the intermediate frequency (IF) mixed by the two OEOs. The accumulative magnification effect at high-order resonant frequency modes makes the strain sensor achieve high sensitivity, which significantly improves the precision of the measurement strain. The cross-referencing structure of the two OEOs makes the influence of the environment, such as temperature, greatly reduced. In the experiments, measurement errors less than ± 0.3 με at a measurement range of 600 με have been realized, including a drift error due to a variation in the environment such as temperature. Furthermore, a quasi-distributed strain measurement system based on the proposed strain sensor has been designed.