Research On Optical Fiber Gas Sensor Based On HC-PCF And Its Networking Technology

In environment protection and modern industrial production, monitoring lowgas concentration is essential, moreover, modern industry is in badly need of asensing network for multipoint gas detection. There are a lot of advantages in fiberoptical gas sensing methods and devices, such as anti-interference and intrinsicsafe, small in size, easy to build up networks, easy to make use of the state-of-artoptical communication technologies, smart and multi-parameters monitoring.These outstanding features make it a main investigation object at home and abroad.Nevertheless, optical spectroscopic systems are used more and more often in gassensing area as they provide high sensitivity, fast response time, specificmolecular absorption spectrum and immunity to electromagnetic fields.Research of gas sensors based on PCF has been widely done the se years, whilewe seldom see research about the networking of gas sensors. Around these twothesis, the main contents of this paper are:1）We deeply learnt the application of HC-PCF in gas sensing and introduced anovel absorption spectroscopy gas sensor using HC-PCF as gas cell. Thetransmission spectrum of13band of acetylene (C2H2) was obtained. And weestimated a minimum detective sensitivity of143ppmv for the system while thedetecting wavelength is1531.58nm.2）The four current optical gas sensing networking methods are discussed inthis paper. We analyzed these four methods in system loss, SNR（signal to noiseratio）and other aspects, thus, according to the conditions of our laboratory, wechose an optical acetylene gas sensing networking system based on wavelengthdivision. In this system, the wide band beam from the SLED source is splitted intothree narrow band beams by three DWDMs (Dense Wavelength DivisionMultiplexing), which included only one of the acetylene absorption peaksrespectively. Each wavelength stands for a detecting point, and finally a systemfor multipoint detecting is formed.3) Practically we set up a three-point detecting acetylene gas sensing network,aimed to demonstrate for the system we have chosen. We use three absorptionpeaks of acetylene gas:1530.371nm,1532.830nm and1536.712nm to detect theabsorption spectrum of this gas in gas cells G1, G2and G3. From the absorptionspectrums we calculated that the minimum detecting sensitivity is94ppmv.