An optoelectronic oscillator-based strain sensor with extended measurement range

ABSTRACT An optoelectronic oscillator (OEO)‐based strain sensor with extended measurement range is proposed and demonstrated. The OEO is embedded with an electrical phase shifter (EPS) to cancel out the strain‐induced phase shift real‐timely via a phase‐locked loop scheme. Theoretically, the control voltage of the EPS is linear to the strain applied on the sensing fiber, leading to a simple and straightforward frequency demodulation. Thanks to the real‐time close‐loop interrogation, the mode‐hopping‐free frequency shift range can exceed one free spectrum range, thus, the measurement range of the sensor is extended. The obtained strain measurement range is up to 2762 με. The achieved strain resolution is 0.86 με. The root‐mean‐square deviation of more than 2‐h test for a fixed strain is 1.1 με. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2336–2339, 2015