Speckle-based fiber sensor for temperature measurement

The applications of specklegram analysis techniques have been developed recently. In this paper, we represent a fiber-optic method to measure the temperature through the analysis of output specklegrams. The proposed all-fiber device excites higher-order modes through splicing a multimode fiber (MMF) to a single-mode fiber (SMF) with a core offset. The basic principle of the sensor is based on determining the change occurring to a speckle pattern when the fiber is heated under different temperature. This change in the speckle pattern is computed by comparing it with a reference speckle pattern recorded at a known temperature and therefore can be related to the temperature change. The experiments manifest the approximately linear relation between correlation coefficient and temperature. Furthermore, we also demonstrate the effects of other related parameters to the sensor.