Intrinsic crosstalk analysis of a serial TDM FGB sensor array by using a tunable laser

Fiber Bragg gratings (FBGs), with their wavelength-encoded nature and their capacity for been demonstrated for a number of sensing applications, especially for strain measurements in smart structures. Recently, there has been interest in using tunable lasers for interrogating FBG sensors in serial topology for improving signal to noise ratio and for multiplexing a large number of sensors using TDM or a combination of WDM and TDM techniques in a single optical fiber. However, there are some drawbacks in using a serial topology because the reflected light signals from FBGs separated in time but overlapping in wavelength can experience crosstalk, termed "spectral shadowing" and "multiple reflection". These kinds of crosstalks are intrinsic and would limit the accuracy of the wavelength detection and the number of sensors in the array. We report the results of our recent theoretical investigation and computer simulations.