High-resolution distributed optical fiber system for spectrophotometric analysis of liquids (Conference Presentation)

A high resolution distributed optical fiber system for spectrophotometric analysis of liquids is proposed. The sensor is based on a light diffusing fiber (LDF) that acts as a continuous distributed detector. The fiber is illuminated by a high-density addressable LED strip is placed parallel to the LDF. The light emitted by a single LED of the strip passes through the liquid sample, couples to the LDF and is detected at the end of the fiber by a mini spectrometer. By sequentially turning on each LEDs of the strip, distributed spectroscopic analysis of the liquid sample can be performed along the entire fiber length. Optical absorption spectroscopy in the whole visible range by white emitting LED has been implemented. The proposed approach enables a continuous spatial localization and quantification of analytes in liquids, like azo dyes, along a sensing length of 1m with a spatial resolution of 12mm and a limit of detection lower than 1ppm.