Temperature-independent measurement of displacement based on the chirp tuning of a fiber grating

We report the temperature-independent measurement of displacement based on the chirp tuning of a fiber grating and a specially designed cantilever. The 3-dB bandwidth of the chirped grating changes linearly with displacement and is independent of the temperature. The displacement can be monitored directly by measuring the reflected light from the chirp grating. A linear displacement response of 37.063 mV/mm was obtained. The fluctuation of the output signal is less than 5% for a temperature range from 20 to 60°C without any temperature compensation technique. The sensor has potentially low cost due to its simple structure.