Papers by Author: Yue Yi Kang

Abstract: ion: In gas difference absorption detecting system, the output electric signal is very faint and submerged in the background noise. In order to extract the faint signal covered by the background noise, we design the detective circuit aiming at how to restrain the noise and improve SNR of the system. In this paper, the detection circuit centering lock-in amplifier which reference signal frequency is automaticly followed is designed. The circuit adopts synchronization cumulating and locked loop technic, carries out frequency and phase aotomatic follow to the measuring signal by a locked loop circuit. The circuit not only avoids the tache taking reference signai from the modulator then adjusting the phase shif, but also improving signal-to-noise ratio more by synchronization cumulation.

Abstract: In this paper, based on analysis of the near infrared spectral absorption of methane molecule and considering factors such as compatibility with the transmission characteristics of silica optical fiber and the price, using Fiber Bragg Grating (FBG) filters to replace the the traditional interference filter, a novel kind of all-fiber remote sensor utilizing FBG filters and 1.33μm high power light-emitting diode (LED) was developed for real time measurement of methane gas concentration. FBG has a low insert loss and can be produced easily compared with dielectric interference filters. Theory and experiment proved that the system has simple construct and high sensibility.