Sensing interrogation system with Michelson interferometer incorporating an optoelectronic oscillator

Abstract

Optical fiber sensors based on Michelson interferometers (MIs) have potential applications in condition monitoring and measurement systems. We propose an optoelectronic oscillator (OEO)-based interrogation system with MI. The interrogation system has a high interrogation resolution and large measurement scale. The sinusoidal nature of the MI spectrum results in a single-passband microwave photonic filter (MPF), whose central frequency is determined by the dispersion parameters of the employed dispersive element and the free spectral range (FSR) of the MI. When the external environmental or physical factors change, the FSR of the MI varies and leads to the frequency shift o f the MPF, ultimately contributing to the frequency shift of the OEO-generated signal. We verify that the variation of temperature and strain can be demodulated by tracking the frequency of the OEO. We also employ an infinite impulse response (IIR)- MPF based on a fiber ring resonator (FRR) for fine oscillation mode selection and evaluate the interrogation resolution and the measurement accuracy of the interrogation system. Different from conventional interrogation systems tracking the wavelength shift of the MI spectrum, our scheme demodulates the sensing information in the electrical domain utilizing an OEO, providing a potential way to implement high-resolution sensing for conventional optical fiber sensors. Moreover, thanks to the wavelength-to-frequency mapping and the wide frequency tunable range of the OEO, our scheme would support large-scale sensing because it can avoid the overlap of MI periodic spectrum in wavelength demodulation.