High-precision strain-insensitive temperature sensor based on an optoelectronic oscillator

We have proposed and experimentally demonstrated a high-precision and strain-insensitive temperature sensor based on an optoelectronic oscillator (OEO). The oscillation frequency of the OEO is determined by the single passband microwave photonic filter (MPF) by using stimulated Brillouin scattering (SBS). The sensing fiber, which acts as the SBS gain medium, is exposed to temperature variations. The Brillouin frequency shift (BFS) changes along with the temperature. Since the central frequency of the MPF is a function of the BFS, the oscillation frequency of the OEO is varied. Besides, due to the mode competition in the OEO, the influence of the strain is eliminated. Thus, the temperature variations can be estimated through measuring the oscillation frequency. We carry out a proof-to-concept experiment. Temperature sensing with a high sensitivity of 1.00745 MHz/°C is achieved. The maximum measurement error of temperature obtained is within ± 0.5 °C. The proposed scheme has merits of simplicity and compact configuration. In addition, the proposed temperature sensor can realize quasi-distributed measurement by utilizing wavelength division multiplexing (WDM).