Multi-channel FBG sensing system using a dense wavelength division demultiplexing module

Fiber Bragg grating (FBG) sensing is gaining attention in both scientific research areas and engineering applications thanks to its distinguishing advantages including wavelength multiplexing capability, miniature size, high sensitivity, immunity from electro-magnetic interference, etc. FBG sensing is based on the detection of the shifted Bragg wavelength of the light reflected by a fiber grating which is sensitive to various physical parameters such as strain and temperature. One of the challenging tasks in FBG sensing is to determine the Bragg wavelength shift, which can be done by using an optical spectrum analyzer (OSA). An OSA is suitable for laboratory tests, but not an ideal solution for field applications in term of cost and convenience. Different wavelength demodulation methods have been developed for FBG sensing purpose. One of them is employing a bulk linear edge filter to convert the wavelength shifts to intensity variations. This method offers several obvious advantages including low cost and ability for dynamic measurements. However, most of the edge-filter based FBG sensing systems are designed for single-channel measurement. In this study, we propose and develop a multi-channel FBG sensing system based on the edge-filtering technique. In order to demodulate multi-channel signal from FBG sensors, we propose to use a dense wavelength division multiplexing (DWDM) module. The light signals coming from wavelength-multiplexed FBG sensors are demultiplexed into individual channels and demodulated by the pass-band edges. In the present study, a four-channel FBG sensing system has been demonstrated.