Faye Zhang

TiO_2 nanoparticle thin film-coated optical fiber Fabry-Perot sensor

In this paper, a novel TiO(2) nanoparticle thin film coated optical fiber Fabry-Perot (F-P) sensor had been developed for refractive index (RI) sensing by monitoring the shifts of the fringe contrast in the reflectance spectra. Using in situ liquid phase deposition approach, the TiO(2) nanoparticle thin film could be formed on the fiber surface in a controlled fashion. The optical properties of as-prepared F-P sensors were investigated both theoretically and experimentally. The results indicated that the RI sensitivity of F-P sensors could be effectively improved after the deposition of nanoparticle thin-films. It was about 69.38 dB/RIU, which was 2.6 times higher than that of uncoated one. The linear RI measurement range was also extended from 1.333~1.457 to 1.333~1.8423. More importantly, its optical properties exhibited the unique temperature-independent performance. Therefore, owing to these special optical properties, the TiO(2) nanoparticle thin film coated F-P sensors have great potentials in medical diagnostics, food quality testing, environmental monitoring, biohazard detection and homeland security, even at elevated temperature.

Optical Response of Fiber-Optic Fabry-Perot Refractive-Index Tip Sensor Coated With Polyelectrolyte Multilayer Ultra-Thin Films

The polyelectrolyte multilayer (PEM) thin film-coated Fabry-Perot (F-P) optical fiber tip sensors had been developed for in situ refractive index (RI) measurement. Using the simple layer-by-layer (LBL) approach, the sensor surfaces had been successfully coated with PEM thin films of poly(diallyldimethyl- ammonium choloride)/poly(styrenesulfonate sodium salt) (PDDA/PSS)n (n is number of bilayers). Their optical response to the changes of external RI had been investigated and evaluated. The results demonstrated that after coated with PEM thin films, the inflection point of as-formed F-P tip sensor would shift from 1.457 to 1.4623 but its RI sensitivity was slightly reduced from 39 dB/RI to 25 dB/RI. In addition, their fringe contrast exhibited the unique temperature-independent performance. Therefore, owing to these special optical properties, simple operation and easy miniaturization, these novel PEM thin film coated F-P tip sensors have great potential in the detection and sensing of chemical and biological molecules, even at elevated temperature.

Transmission Characteristics of High Frequency Signal in Low Voltage Power Lines

Power line carrier communication using 1MHz ~ 30MHz as carrier signal can improve the bandwidth of data transmission. Using the high frequency signal as a carrier signal, with the increase of signal frequency, the attenuation range of low voltage power line channel is also increased. On the basis of the structure of low voltage power grid, the transmission attenuation model of high frequency signal in low voltage power line channel is established by using transmission line theory. The attenuation in different locations and loads is measured by experiments. Analytical results show that the attenuation of the signal increases with frequency in the 1~30MHz band. The attenuation of the signal is time varying to a certain extent. The attenuation of the signal is also impacted by the load. As the load increases, the attenuation of the signal increases.

Acoustic emission source linear localization based on an ultra-short FBGs sensing system

An acoustic emission (AE) linear location system is proposed, which employs fiber Bragg gratings (FBGs) as AE sensors. It is demonstrated that the FBG wavelength can be modulated as static case when the grating length is much shorter than the AE wavelength. In addition, an improved AE location method based on Gabor wavelet transform (WT) and threshold analysis is represented. The method is testified through AE linear location experiments based on a tunable narrow-band laser interrogation system using ultra-short FBG sensors as AE sensors. Results of the experiments show that 86% of the linear location errors are less than 10mm.