Active Time-domain Addressing Technique For Fiber Bragg Grating Sensor System

The paper combined the wavelength selectable technique of fiber ring-laser which use fiber Bragg grating as reflector, and real-time multi-channel outputting analog electrical switch technique, for real-time active interrogation a wavelength -division-multiplexed FBG sensor array and outputting the sensed information in multi-channel according to the corresponding relationship between the sensor and output channel. The work was concentrate on four aspects below.1. The design and realization of the drive power of diode laser, according to the performance characteristics of semiconductor laser diode, such as the high stability requirement to driving current and the weak endure ability to electric shock; drive power for pump laser module was designed. Concretely for 980nm pump laser, using negative power analog circuit technology, a novel laser drive with Slow Turn-On and Optic Power Steady Circuit has been realized.2. The adjustment of optical route of system, after the theory analysis for optical route of the active addressing system, lots of experiment has been done, and then a suitable optical route with low optical noise and threshold has been fond.3. Preparing for the real-time multi-channel outputting analog electrical switch, considering the output signals'characteristic of the active system, multiple output analog electrical switch controlled by MCU was designed. The transmit time of each channel was determined. by experiment, then the switch makes one sensor correspond to one output channel while signal outputting in a multiple real-time way.4. The experiment of the active addressing sensor system. for 4 element FBG array, the analog electrical switch was employed for processing the output signal of active addressing system, and output signal of one channel was demodulated by unbalanced Michelson interfere-meter, which converts the wavelength shifts to phase changes with high resolution, and phase shift detection was done by lock phase amplifier, then the strain can be count. The obtained sensitivity of the system worked at 1555nm was demonstrated to be: 1.630°/μ(?), which agree with the theoretical value of 1.674°/με.