Research On Intra-cavity Gas Sensor Based On HC-PCF And Its Network

Monitoring pollutant and harmful gases such as methane,acetylene,hydrogen sulfide,ammonia is quite important in modern industrial production and environmental protection.The devices and methods of optical fiber gas sensor have lots of outstanding characteristics such as strong immunity to electromagnetic interference,based on optical communication technology,small in size,easy network organization,automatic detection,etc,which makes it a significant research subject at home and abroad nowadays.So far,the field of optical fiber gas sensor has made a lot of achievements.And how to build up multiplexed gas sensor network using optical fiber gas sensor has become a hot field of research directions.This paper is mainly about the theme of intra-cavity gas sensor based on hollow-core photonic crystal fiber(HC-PCF)and its networking technology.The main research work and major innovations are as below:1)We have designed a new erbium-doped fiber ring laser(EDFRL)intra-cavity sensor.HC-PCF used as the gas absorption chamber is introduced into the laser cavity.We combine the theory of output power of EDFRL and the Beer-Lambert law.Absorption peaks of acetylene and some other data are got from the Hitran database.We have theoretically investigated the relationship of some significant system parameters such as concentrations of acetylene,coupling ratios,pump power and output power.Different spectra are also simulated with different concentrations of acetylene.The simulated results prove that this sensing system can be used for acetylene detection and has the ability of high sensitivity.2)The designed EDFRL intra-cavity sensor is set up.We use a modular NI PXI platform equipped with a programmable voltage and current source to generate driving voltage for the tunable optical filter(TOF)to ensure high precision.Simulating results are validated by the experimental results and good consistency is achieved.A minimum detectable acetylene concentration(MDAC)of 5.4 ppmv has been experimentally achieved,which proves that this gas sensing system has the ability of high sensitivity.3)Based on the research work of the EDFRL intra-cavity sensor,we expand it to multiplexed gas sensor network.We report the system design and experimental verification of this sensor network with HC-PCF and dense wavelength division multiplexing(DWDM)filters.Compared with fiber Bragg grating(FBG),it is easier for the DWDM to accomplish a stable output.We realize the concentration detection of three gas cells filled with acetylene.The sensitivity is up to 100 ppmv at 1536.71 nm.Voltage gradient is firstly used to optimize the intra-cavity sensor network enhancing the detection efficiency up to 5.5 times.