New Self-Compensated Optoelectronic Circuit for Highly Reliable Read-Out of FBG Sensor Arrays

This article reports the description and functional tests of a novel wavelength-encoded fiber-optic sensors (FOSs) read-out circuit. The proposed design can transduce the optical signal reflected by the FOS under test into a voltage or current output, suitable for the industrial environment. It is based on two fully analog boards, designed to provide the ratio between the FOS-related analog signal and a reference signal thereby enhancing its ability to reject source fluctuations and possible losses in the optical transmission channel. After a theoretical analysis, the circuit was validated both in static and dynamic conditions using a fiber Bragg grating (FBG) sensor, which was subjected to temperature variations for static testing and high-speed strain variations for dynamic testing. The circuit was designed to display different output values based on its working state (e.g., normal operation or a broken sensor), enhancing fault analysis and paving the way for the adoption of FOS technology in environments where digital processing is prohibited. Finally, compared with the state-of-the-art interrogator, the proposed fully analog self-compensated circuit is more robust, rejecting the unwanted signal on the output line, as demonstrated experimentally.