MCFBG curvature sensor using two-photon absorption process in Si-APD and its application to medical use

We have developed a fiber optic curvature sensor based on a multicore fiber Bragg grating (MCFBG) and an optical signal intensity correlation processing that uses two-photon absorption (TPA) process in a silicon avalanche photodiode (Si-APD). The developed sensor can use a relatively low cost MCFBG in which all the inscribed gratings have basically the same Bragg wavelength. The overlapped reflection spectra of the gratings are simultaneously obtained and discriminated by using intensity correlation measurement based on TPA photocurrent from a single Si-APD without using optical switches or multiple photodetectors. Our MCFBG curvature sensor can be applied to medical use such as bending, force, or shape sensors for a medical catheter and body plethysmography.