To increase the sensitivity of biosensor a new approach using an optical fiber Bragg grating (FBG) coated with a suitable\nnanostructured metal oxide (NMO) is proposed which is costly effective compared to other biosensors. Bragg grating was written\non a D-shaped optical fiber by phasemask method using a 248 nmKrF excimer laser for a 5 min exposure time producing a grating\nwith a period of 528 nm. Titaniumdioxide (TiO2) nanostructured metal oxide was coated over the fiber for the purpose of increasing\nits sensing area. The etched D-shaped FBG was then coated with 312nm thick TiO2 nanostructured layer to ensure propagating\nthe radiation modes within the core. The final structure was used to sense deionized water and saline.The etched D-shaped FBG\noriginal sensitivity before coating to air-deionized water and to air-saline was 0.314 nm/riu and 0.142 nm/riu, respectively. After\ncoating the sensitivity became 1.257 nm/riu for air-deionized water and 0.857 nm/riu for air-saline.
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