High-resolution temperature sensor based on intracavity sensing of fiber ring laser

The principle and design of high-resolution sensors are of great significance in the development of fiber-optic sensors. In this paper, a general method based on intracavity sensing of fiber ring laser (FRL) is proposed for high-resolution measurement and a high-resolution temperature sensing system is experimentally demonstrated. The theoretical model for intracavity sensing of FRL is presented. In the sensing system, a fiber-optic Sagnac loop is inserted into an FRL for temperature measurement, which performs as the filter and sensing head simultaneously. Because the filter characteristics of the Sagnac loop is modulated by temperature, the intracavity intensity-modulated temperature sensing is induced for the output power of the FRL. With the method based on intracavity sensing, the resolution level of the sensing system has been improved from ${\rm{10^{-3}\ \degree C}}$ to ${\rm{10^{-6}\ \degree C}}$ . The stability and measurement errors are also measured. The proposed method can be extensible to similar fiber-optic sensors to improve measurement resolution.