Theoretical Assessment of an All-Optical Temporal Low-Pass Filter for Dynamic Fiber Bragg Grating Signals

Fiber Bragg grating (FBG) sensors are used in numerous applications. Currently, the assessment of dynamic loads with FBGs is of increasing interest. Those applications include vibration analysis, acceleration, or dynamic strain estimation. The acquisition of dynamic signals usually incorporates the application of signal low-pass filtering before signal quantization. FBG interrogators based on spectrometers or scanning lasers inherently have a limited antialiasing capability for dynamic FBG signals. We present a theoretical analysis of an all optical low-pass filter for spectrometer-based interrogators. The low-pass filter is based on the application of a luminescent material onto the detector. Light absorption and continuous light reemission lead to an advanced attenuation of high FBG signal frequencies. An analytic derivation of the system transfer function and numerical signal simulations are presented.