Proceedings Article | 8 January 2008
Proc. SPIE. 6801, Photonics: Design, Technology, and Packaging III
KEYWORDS: Fiber Bragg gratings, Sensors, Signal detection, Edge detection, Optical filters, Photodetectors, Data acquisition, Temperature metrology, Tunable lasers, Electronic filtering
Traditional Fibre Bragg Grating (FBG) sensing systems acquire data about the measurand via the spectral response of the
FBG. Edge filter methods are also used in the acquisition of data from FBGs. In edge filter systems, the spectral shift in
the FBG due to the measurand is converted into an optical power change. This optical power change can then be easily
measured using conventional optoelectronic devices. We demonstrate the use of a Transmit Reflect Detection System
(TRDS) for Fibre Bragg Grating (FBG) sensors. The TRDS is in essence a dual edge filter detection method. In
conventional edge filter detection schemes, the reflected portion of the incident spectrum is monitored to determine the
change in the measurand. In the TRDS, both the transmitted and reflected portions of the input spectrum, from a narrow
band light source, are utilised. The optical power of the transmitted and reflected signals are measured via two separate
photoreceivers, where each generates a single edge filter signal. As the spectral response of the FBG shifts due to the
measurand, the transmitted power will increase, and the reflected power will decrease, or vice versa. By differentially
amplifying the transmitted and reflected components, the overall signal is increased. This results in improved sensitivity
and efficiency of the photonic sensor. In this work, the FBG sensor and TRDS are used in the measuring and monitoring
of temperature, force and strain. As such, results are presented for the FBG TRDS for all of the measurands.
