11 September 2015 Spectral response of long-period fiber gratings to cladding refractive index perturbation
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The spectral response of long-period fiber gratings can be tailored by the cladding index perturbation (C-LPFGs) induced by written methods. Here, we investigate theoretically the effects of radial dependence and the magnitude of the cladding index modulation on the transmission spectra of C-LPFGs. Simple analytical expressions that describe the dispersion characteristics of the guided core mode and cladding modes are derived from a multilayer cylindrical waveguide. As the radial depth increases, we demonstrate that transition points exist for the resonances of lower cladding modes, i.e., LP06 and LP15 modes, by comparing the mode-coupling phase to the value π/2. In addition, we show that resonant wavelength shifts of all cladding modes follow the same trend. For the LPνj (ν≠0) modes with two polarizations, the cross talk weakens the power exchanges between core mode LP01 and LPνj (ν≠0) modes. Moreover, the coupling mechanism relating to cladding index modulation is explained by the presence of the interaction between the evanescent field of the core mode and cladding modes. This work is promising in terms of providing sufficient guidelines to understand and explore design and application of LPFGs.
© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Zhihong Li, Tao Chen, Zhaogang Zhang, Yanming Zhou, Dan Li, Zhong Xie, "Spectral response of long-period fiber gratings to cladding refractive index perturbation," Optical Engineering 54(9), 096105 (11 September 2015). https://doi.org/10.1117/1.OE.54.9.096105 . Submission:

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