Theoretical Design of Band Pass Filter Utilizing Long Period Fiber Grating Having Cladding Refractive Index Perturbation
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In this work, theoretical design of a novel band pass filter based on the turning-around-point long period fiber grating (TAP-LPFG) having cladding index modulation is proposed and demonstrated. Cladding modes are excited by introducing the incident light into the fiber cladding of the input end of the TAP-LPFG. At the grating region, only those cladding modes that satisfy the phase matching condition couple back to the fiber core to obtain the band pass transmission. It is shown that a band pass filter with –3 dB width of from ~115 to ~198 nm with the center wavelength of ~1554.4 nm can be obtained, and the suppression of more than 10 dB for the side-lobes is achieved in a wide wavelength range. This novel TAP-LPFG based device can find applications in optical communications for wide band pass filter.
Keywords:band pass filter long period fiber grating (LPFG) turning around point (TAP) cladding refractive index modulation
This work was supported by Natural Science Foundation of China (nos. 61377021 and 61671329) and Science and Technology Plan Project of Wenzhou of China (no. H20110003).
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