A high sensitive multi-component gas sensing system was proposed, in which the slotted photonic crystal waveguide (SPCW) was used as the gas cell and the fiber Fabry–Perot (FFP) was adopted as the wavelength filter By choosing the refractive index that infiltrated in the first and second rows of air holes adjacent to the slot respectively, the working wavelength of SPCW could be tuned to matches with one absorption line of the measured gas, thus, the system could detect different kinds of gases selectively Meanwhile, a very high group index of 150 with flat bandwidth could be achieved and the electric field enhancement factor would reach to 12 Combined with the wavelength modulation techniques (WMS) for signal processing, the minimum detection limit of 156 ppm was achieved

Multi-component gas sensing based on slotted photonic crystal waveguide with liquid infiltration

Estimating nitrogen status of rice canopy using hyperspectral reflectance combined with BPSO-SVR in cold region

A miniature and sensitivity gas sensor based on slotted photonic crystal waveguide (SPCW) was presented, in which the correlation spectroscopy method was applied for signal processing and the SPCW was used for the gas cell. To enhance the system sensitivity, the structure of the SPCW was optimized to possess extremely high group index and very large light confinement in the slot. Simulation results indicated that the measuring resolution of acetylene gas of 1 ppm was achieved with good temperature stability. Additionally, the active region was only 1 mm long, which could be of great advantage in the use of the limited space.

Theoretical research on high sensitivity gas sensor due to slow light in slotted photonic crystal waveguide

Research on demodulation of FBGs sensor network based on PSO-SA algorithm

An optimized strain demodulation method for PZT driven fiber Fabry–Perot tunable filter

A practical mixed-gas sensing system utilizing a fiber Fabry–Perot (FFP) filter and Fiber Bragg Gratings (FBG) was developed. By modulating the transmission wavelength of FFP within the width of one absorption line of the target gas, the system can detect different kinds of gaseous species selectively. A FBG with center wavelength being aligned to the absorption peak of the target gas was employed as wavelength reference to make the transmission wavelength of FFP modulate stably in a required region. The properties of the proposed system were demonstrated experimentally by simultaneous detection of acetylene (C 2 H 2 ) and carbon monoxide (CO). Approximate linear relationships between the system responses and the input gas concentrations were demonstrated by experiments. The minimum detectable C 2 H 2 and CO concentration of ∼15 ppm and ∼300 ppm were also achieved by experiments respectively.

A novel fiber Fabry–Perot filter based mixed-gas sensing system

The invention discloses a spectral absorption type gas-surveying gas chamber The top of a first micro closed cavity is provided with a first gas outlet, the top of a second micro closed cavity is provided with a second gas outlet, and the first gas outlet and the second gas outlet are connected with a micro vacuum pump; monomode optical fiber and first segment hollow-core optical fiber are connected in the first micro closed cavity, and multimode optical fiber and second segment hollow-core optical fiber are connected in the second micro closed cavity; the first segment hollow-core optical fiber is connected with the second segment hollow-core optical fiber; and a detection light source enters the first segment hollow-core optical fiber by the monomode optical fiber and then enters the multimode optical fiber by the second segment hollow-core optical fiber, and is outputted to a photo detector by the multimode optical fiber The invention provides a gas chamber for measuring spectral absorption type gas The gas chamber has the advantages of small volume, easy bending and high coupling efficiency, and optical length absorption of the gas can be increased by increasing the length of the optical fiber; moreover, the diffusion speed and escape speed of the environmental gas in a gas cavity can be improved

Spectral absorption type air-surveying air chamber and method for improving air diffusion speed

In order to improve the measurement accuracy of FBG sensing system, particle swarm optimization (PSO) algorithm combined with reference FBGs array was applied to investigate the nonlinearity and hysteresis character of Fabry-Parot filter (FPF). A method of modeling the wavelength-voltage relationship of FPF online in each FPF scanning cycle was proposed in the present paper. The feature of particle swarm optimization algorithm such as fast convergence and simple implementation makes the process of modeling wavelength-voltage relationship of FPF be completed with low computing cost and high accuracy. With the set-up model, the absolute error in wavelength detection of FBG sensors was demonstrated by experiments to be as low as 0.03 nm. The structure of the system is compact and the proposed modeling approach has important meaning in FBG sensors system when FPF is used as wavelength demodulator.

Application of PSO algorithm in wavelength detection of FBG sensors

Online calibration of PZT driven fiber Fabry-Perot filter nonlinearity using FBG array and PSO algorithm

A tunable optical filter (TOF) based acetylene sensing system is proposed in this paper. By
modulating the wavelength of TOF within the width of one absorption line of acetylene, both the
sensitivity and selective sensing properties of the system for sensing acetylene have been much
improved. Approximate linear calibration curves in sensing acetylene is obtained by experiments. The
minimum detectable acetylene concentration of 5ppm is also achieved by experiments. The proposed
system has great potential in developing mixed-gas sensing system.

Jianqi Liang

Papers

A novel fiber Fabry–Perot filter based mixed-gas sensing system

Spectral absorption type air-surveying air chamber and method for improving air diffusion speed

Application of PSO algorithm in wavelength detection of FBG sensors

Online calibration of PZT driven fiber Fabry-Perot filter nonlinearity using FBG array and PSO algorithm

A novel acetylene sensing system based on tunable optical filter