The transmission characteristics of a nonuniform photonic fiber Bragg grating (PFBG) are studied in detail by FEM
furnished with 1<sup>st</sup> - order BGT - like TBC and transfer matrix method. The effects of the air hole size on PFBG's
transmission properties such as effective index, Bragg reflective wavelength, normalized bandwidth and centre
wavelength shift are investigated. It is believed the study can provide useful information for PFBG's design and
optimization with a more effective and accurate method.
The design criteria of the Panda-type erbium-doped polarization-maintaining fiber (EDPMF) are presented, which take into account the cutoff wavelength, mode field diameter, modal birefringence and background loss. The structural parameters are optimized in terms of the design criteria. A Panda-type EDPMF has been manufactured. The fabrication process and the parameter control of the Panda-type EDPMF are in detail described. Its refractive index profile, birefringence and absorption spectra are experimentally investigated.
The finite element method with 2<sup>nd</sup>-order transparent boundary conditions is proposed to analysis the modes of photonic crystal fibers. These boundary conditions preserve the sparse matrix and offering accuracy of O(r<sup>-9/2</sup>), here r denoting the position of the computational boundary with respect to a chosen origin of the structure. The effective mode-index, the mode distribution, the confinement loss and the dispersion properties of the total internal reflection photonic crystal fibers (TIR-PCF) with triangle lattices and rectangle lattices are calculated in this method respectively. The results agree with the published results. At the same time the finite element method in the paper lessens the computation domain remarkably. It offers an easy and credibility approach in the study on the PCF and other fibers with irregular cross-section index distribution, even fibers with anisotropy materials.
A improved train real-time tracing system based on distributed Fiber Bragg Grating sensors is introduced in this paper. Without delicate sensing head, the system can realize the real-time detection of the railway condition and trains' running behavior such as the position, velocity, acceleration, load on axle, number of the axles and so on. To some extent, the system can also implement warning of the train accidents. The system will be significant to the railroad transport.
In this paper, the pump absorption efficiency and the optimum length of DCOFs with several kinds of inner cladding shapes have been studied through the ray trace method. The DCOFs with circular, rectangular, triangular, hexagonal inner cladding have been studied in this paper. Expect for the DCOF with circular inner cladding. The maximum pump absorption efficiency of the DCOFs above exceed 0.9. It is found that the triangle shape has the highest absorption and there is only little difference among the polygon DCOF. The ray trace method is a more simple and quick method and it is competent for DCOFs with more kinds of inner cladding.