Temperature-compensated single-ended twist sensor based on cascaded fiber grating

A temperature-compensated optical fiber twist sensor based on cascaded long-period fiber gratings (LPFG) and fiber Bragg grating (FBG) is proposed and experimentally demonstrated. The LPFG is sensitive to twist and its transmitted light is twist modulated and reflected by the FBG. In this way, a single-ended twist sensor is realized by monitoring the reflection spectrum of the cascade grating. Both the wavelength and amplitude of the reflection spectrum are detected. The wavelength is sensitive to temperature but not to twist, so it is used for temperature compensation in twist measurement. Experimental results show that the proposed sensor improves the twist accuracy by 2 orders of magnitude in the temperature range of 15°C to 35°C. © 2020 Society of Photo-Optical Instrumentation Engineers (SPIE).