Wavelength Interrogator Based on Closed-Loop Piezo-Electrically Scanned Space-to-Wavelength Mapping of an Arrayed Waveguide Grating

We demonstrate a novel technique for the interrogation of grating-based fiber optic sensors. The proposed technique is based on space-to-wavelength mapping using an arrayed waveguide grating (AWG). The beam position along the AWG input coupler is controlled by a closed-loop piezoelectric motor. By employing a real-time position feedback encoder, the absolute position of the input light beam can be accurately obtained, which would yield a precise interrogation of the wavelength due to a fixed relationship between the beam position and the transmission wavelength of the AWG channel. The proposed system for the interrogation of fiber Bragg grating (FBG) sensors and a tilted-FBG sensor is experimented. An interrogation resolution of 3 pm and an interrogation range of 18 nm are demonstrated as well as the multichannel measurement capability. Initial results show that the proposed interrogation system has the potential of being packaged into a compact, light weight, and cost-effective interrogator with good performance.