Wavelength-swept laser technique is an active demodulation method which integrates laser source and detecting circuit together to achieve compact size. The method also has the advantages such as large demodulation range, high accuracy, and comparatively high speed. In this paper, we present a FBG interrogation method based on wavelength-swept Laser, in which an erbium-doped fiber is used as gain medium and connected by a WDM to form a ring cavity, a fiber FP tunable filter is inserted in the loop for choosing the laser frequency and a gas absorption cell is adopted as a frequency reference. The laser wavelength is swept by driving the FP filter. If the laser wavelength matches with that of FBG sensors, there will be some strong reflection peak signals. Detecting such signals with the transmittance signal after the gas absorption cell synchronously and analyzing them, the center wavelengths of the FBG sensors are calculated out at last. Here, we discuss the data processing method based on the frequency reference, and experimentally study the swept laser characteristics. Finally, we adopt this interrogator to demodulate FBG stress sensors. The results show that, the demodulation range almost covers C+L band, the resolution and accuracy can reach about 1pm or less and 5pm respectively. So it is very suitable for most FBG measurements.
We present and experimentally analyze the applications of tilted fiber Bragg grating (TFBG) for the measurement of
liquid parameters, including the concentration (or refractive index), liquid-level and dynamic concentration change. On
the basis of analyzing the measurement principle of refractive index using TFBG, its spectral variations with the glycerol
concentration and liquid-level are obtained. Meanwhile, a fast demodulation technique monitoring the small variation of
TFBG transmission power in a strong background is employed to measure dynamic change in the liquid concentration.
The results show that the method is easy to achieve fast, cost-effective measurement of the change process of liquid
The spectrum of Gauss apodized fiber Bragg grating (FBG) is analyzed by using transfer matrix method, and the basic
principles of sub-pixel curve fitting algorithms including mass center, Gauss and full-width-at-half-maximum (FWHM)
are discussed. Based on this, simulation and experimental results are given to compare the three curve fitting algorithms.
The results reveal that in simulation, mass center fitting method with an accuracy of 13pm while in experiment, FWHM
fitting method with an accuracy of 23pm provides a better match to the actual curve. The research achievements have
been applied on the prototype of linear-array detector grating spectrometer and have potential market in portable FBG