Optical signal processing device for optical sensors interrogation

This paper presents optical signal processing device for interrogation of fiber optical sensors and signal processing methods to extract the measured parameter from interrogated optical sensors. The system is built with the use of only few components that include tunable laser source, processing unit, photo-detectors and a reference element which is, therefore, simple to construct. All opto-electronic elements are widely used and cost effective, which makes optical signal processing device suitable for many sensing applications. The system has been tested with Fabry-Perot based sensors and Bragg gratings based sensors using Fabry-Perot interferometer as a reference. Before use, every sensor was calibrated in order to obtain the relation between a reference element and optical sensor. Presented interrogation system extracts the peak wavelengh of sensor's spectral characteristic and converts it to the measured parameter. Testing of temperature sensors has shown a resolution better than 0.5 °C for Fabry-Perot based sensor and for Bragg grating strain sensor, the resolution was better than 10 µε.

I. Introduction

Fiber optic sensors are widely used in various fields of the industry such as bio-medical applications and the extreme environments [1]. Their fiber glass structure makes them immune to the electromagnetic interferences, high temperatures, and most of the chemicals. They also have a high sensitivity and can measure wide range of physical parameters. Many interrogation systems and signal processing methods are available today [2]–[3], however, most of them are still complex and expensive. In search for simpler [4] and more cost effective solutions, we propose a sensing system that consists only of few widely used optoelectronic components and can interrogate optical sensors based on Fabry-Perot (FP) interferometer or fiber Bragg gratings (FBG). Interrogation system has been tested by measuring temperature with FP interferometer and strain with FBG.