An Optical Fiber Bragg Grating Temperature Sensor using Microwave Photonic Filtering Technique

An optical fiber Bragg grating (FBG) temperature sensor based on microwave photonic filtering technique is proposed and demonstrated. A single bandpass microwave photonic filter (MPF) which mainly contains a tunable laser source (TLS), a phase modulator (PM) and a uniform temperature sensing FBG is demonstrated. When the uniform temperature sensing FBG is experiencing a temperature variation, the notch frequency in its reflection spectrum is shifted, leading to a large passband frequency change of the single bandpass MPF. Hence, by measuring the passband frequency, the temperature can be deduced. In this scheme, a high sensitivity temperature sensing with a sensitivity of 1.7641 GHz/°C is achieved. Since a small wavelength variation can induce a large passband frequency change, the performance with respect to the resolution is dramatically increased. In addition, the measurement error of the proposed optical FBG temperature sensor is less than 0.3 °C.