摘要
建立了长周期光纤光栅傅里叶模式耦合理论.在分析同向模式耦合时,发现了同向耦合模式的振幅系数间存在傅里叶变换关系.推导了长周期光纤光栅的同向耦合谱和透射谱的通用表达式.该理论是用傅里叶变换分析得出长周期光纤光栅折射率微扰的空域谱,再对该空域谱进行模式同向耦合分析,从而得到长周期光纤光栅光谱特性的通用表达式.根据该理论模拟分析了长周期光纤光栅在不同长度和微扰幅值时的光谱特性,与传统耦合模理论进行了对比分析.结果表明,该长周期光纤光栅傅里叶模式耦合理论具有简单、精确和高效的特点,与实际长周期光纤光栅的透射谱特性一致.应用该理论可分析无过耦合的任意轴向折射率微扰分布的长周期光纤光栅光谱特性.
A novel theory,namely,Fourier mode coupling（FMC） theory for long-period fiber gratings（LPFGs） is proposed in this paper.During analyzing the co-propagating coupling between the core mode and cladding modes in LPFGs,the Fourier transform relations among the amplitude coefficients of co-propagating coupled-modes are found for the first time,to the best of authors＇knowledge.The general expressions of the coupling and transmission spectra of LPFGs are also deduced from the combination of Fourier transform with the well-known coupled-mode theory.In the proposed FMC theory,the spectral characteristics of the LPFGs without over-coupling are derived from the calculation of co-propagating mode coupling in the spatial domain spectrum,which is the Fourier transform result of refractive index perturbation in the LPFG.According to the FMC theory,the spectra of the LPFGs in different perturbation amplitudes and lengths are numerically simulated here.A measured transmission spectrum is also compared with the calculated transmission spectra based on the FMC theory and the coupled mode theory,respectively.The comparison shows that the FMC theory and the derived spectra for LPFGs are in consistance with the coupled-mode theory and the practical spectra of LPFGs respectively.The FMC has many features,these being simple,fast and accurate,which could be employed for spectrum analysis of any LPFG with an arbitrary distribution of refractive index perturbation along the fiber axis.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2010年第12期8607-8614,共8页
Acta Physica Sinica
关键词
光纤器件
长周期光纤光栅
傅里叶模式耦合
透射光谱
fiber-optic component
long-period fiber grating
Fourier mode coupling
transmission spectrum
