Easy fabrication of long-period fiber grating by winding a wire around an optical fiber fixed to cylindrical ROD

Abstract

A new approach is presented for the easy fabrication of wire-winding long-period fiber grating based on the periodic winding of a wire around an optical fiber attached to a cylindrical rod. The periodic pressure of the wire induces change of the refractive index of the optical fiber core, and so the resonance wavelengths of the grating can be easily controlled according to the winding-wire pitch controlled by a microprocessor. At the winding-wire pitch of 500 μm, the spectra show resonance-wavelength dips corresponding to the LP02, LP03, LP04, and LP05cladding modes; the resonance wavelengths go to longer wavelengths at the increased winding pitch of 510 μm; these are in good agreement with theoretical values. The polarization dependence of a resonance wavelength shift of 9 nm and transmission power difference of 2.5 dB was shown at the 520 μm grating pitch. When the diameter of the cylindrical metal rod was smaller, or higher tension by the winding pressure was applied, stronger mode coupling resulted in deeper dips in the transmission spectra according to induced higher index variation. © 2012 Wiley Periodicals, Inc.