Optoelectronic Oscillators for High Speed and High Resolution Optical Sensing

An optoelectronic oscillator (OEO) can be employed to perform high speed and ultra-high resolution optical sensing. The fundamental concept is to convert a measurand-dependent wavelength change in the optical domain to a frequency change of an OEO-generated microwave signal in the microwave domain. Since the frequency of a microwave signal can be measured by a digital signal processor at a high speed and high resolution, an OEO-based optical sensor is able to provide optical interrogation at a high speed and ultra-high resolution. In this paper, OEO-based optical sensors proposed for strain, temperature, or transverse load sensing are discussed. The key to implement an OEO-based optical sensor is to implement a microwave photonic filter with a passband having a center frequency that is a function of the optical wavelength change. In this paper, techniques to implement microwave photonic filter for OEO-based optical sensing are discussed.