A fiber optic relative humidity (RH) sensor based on the tilted fiber Bragg grating (TFBG) coated with graphene oxide (GO) film was presented. Amplitudes of the cladding mode resonances of the TFGB varies with the water sorption and desorption processes of the GO film, because of the strong interactions between the excited backward propagating cladding modes and the GO film. By detecting the transmission intensity changes of the cladding mode resonant dips at the wavelength of 1557 nm, the maximum sensitivity of 0.129 dB/%RH with a linear correlation coefficient of 99% under the RH range of 10–80% was obtained. The Bragg mode of TFBG can be used as power or wavelength references, since it is inherently insensitive to RH changes. In addition, the proposed humidity sensor shows a good performance in repeatability and stability.

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A "plane cathode micro-hollow anode discharge (PCHAD)" is studied in comparison with micro-hollow cathode discharge (MHCD). A new triode-configuration discharge device is also designed for large-volume, high-pressure glow discharges plasma without glow-to-arc transitions, as well as with an anode metal needle, and a cathode of PCHAD. It has a "needle-hole" sustained glow discharge. Its discharge circuit employs only one power supply circuit with a variable resistor. The discharge experiments have been carried out in the air. The electrical properties and the photoimages in PCHAD, multi-PCHAD and "needle-hole" sustained discharge have been investigated. The electrical and the optical measurements show that this triode-configuration discharge device can operate stably at high-pressure, in parallel without individual ballasting resistance. And the electron density of the plasma is estimated to be up to 10~'cm-~. Compared with the twosupply circuit system, this electrode configuration is very simple with lower cost in generating large-volume plasma at high pressures.

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