Laser Raman Optical Sensor for Monitoring Gas Mixtures Using Photomultiplier Tube Detector

摘要

A Photomultiplier Tube (PMT) based optical fiber Raman sensor was developed for online monitoring of nitrogen/oxygen concentration ratios in gaseous mixtures. The sensor employed a frequency doubled 532 nm continuous wave (CW) Nd:YAG laser and a modified In-Photonics fiber optic state-of-art miniaturized Raman Probe. The gaseous mixture was enclosed in a high pressure cell and subjected to varying degrees of pressure. Raman signal of gaseous nitrogen and oxygen were first analyzed with a miniature spectrometer. The detection system was then replacing by a Labview interfaced PMT module for fast data acquisition and real time monitoring of relative Raman signals of nitrogen and oxygen. Instrumentation features and sensor performances with different detection systems (i.e. spectrometer and PMT) is presented in the paper.