All-optical fiber filter based on an FBG inscribed in a silica/silicone composite fiber

An all-optical tunable filter based on a fiber Bragg grating (FBG) inscribed in a self-heated silica/silicone composite fiber is demonstrated. A thin silicone film is coated inside the suspended core fiber), which acts as the silicone cladding. A periodic refractive index modulation is inscribed in the silicone cladding by UV irradiation. Silicone is an organic material whose optical properties are different than silica, which leads to interesting applications. The high thermo-optic properties are studied and applied here. A 1550 nm pump laser is utilized to heat the silicone grating where a wavelength shift is observed for the gratings when subjected to different pump powers. Experimental results indicate a wavelength tuning coefficient of -0.128nm/mW with a response time of 0.5 s to obtain a wavelength shift of 1 nm under periodic pump light. The new design of this miniature all-optical filter is cost-effective and can potentially be adhered in optical fiber sensing and communication systems.