Detection of tilted fiber bragg grating fiber-optic sensors with short-term KLT: Towards low-cost biosensors

Tilted Fiber Bragg Grating (TFBG) optical fiber sensors can be employed as refractive index sensors, and functionalized as biosensors. The TFBG cladding modes exhibit a small yet detectable sensitivity to the refractive index in the surrounding of the sensing region. One of the weaknesses of TFBG is that classical interrogation methods require narrow wavelength resolution to analyze these spectral features which can be achieved only through a bulky setup. In this work, we propose a demodulation method, namely the short term Karhunen-Loeve Transform (ST-KLT) that can be applied to a low-cost spectrometer that detects the TFBG reflection spectrum. The method is capable of detecting refractive index variations in the order of 10 _-3 - 10 _-4 refractive index units (RIU), and is this a potential pillar towards low-cost TFBG biosensors.