Dispersion characteristics of novel class multi-clad dispersion shifted hollow core fibers for WDM optical systems

The design and analysis of multiple-clad hollow core dispersion-shifted fibers have been presented in this paper. Fiber profiles have been designed consisting of a central core that is hollow and outer cladding is silica. The novel refractive index profile has multi-clad for enhanced optical characteristics. Optical fibers with two or more claddings are required for dispersion shifting, dispersion flattening, and other specialized applications. Thus, the hollow core fiber shows the zero dispersion at 1550 nm wavelength. These hollow core fibers have potential application in WDM optical systems

Modelling of simply supported circular diaphragm for touch mode capacitive sensors

This paper describes the power series solution for modelling of the simply supported circular diaphragm deflection under uniform load. The parameters such as touch point pressure and touch radius are defined. Moreover, these parameters are also computed by the algorithm proposed in the paper. Therefore, the power series solution can be applied for touch mode operation

Finite element method analysis of propagation in a non magnetic coupled waveguide structure having α-power refractive index profile

The work presented in the paper is a numerical study of a waveguiding component. The structure studied is a coupler consisting of three closely-coupled weakly-guiding one-dimensional waveguides. The refractive index profile of the coupler has been allowed to vary arbitrarily. The scalar finite element method (FEM) has been used to separately extract the TE and TM modes supported by this coupler and propagate them along the structure using a beam propagation method (BPM). We excite structure with Eigen mode profile which can be well approximated by Gaussian shape pulse. The effect of waveguide separation has been well demonstrated by using an example. The Crank-Nicolson (CN) scheme has been used to stabilize the propagation and transparent boundary conditions (TBC) which have been used to absorb energy leaked by the waveguides to the outer boundaries. The work’s main finding is that the coupling period of the structure can be changed by altering the index profile of the middle waveguide; step-, parabolic- and triangular-profile distributions have been studied and compared. In FEM analysis we have used the variable discretization step (δ) for the better accuracy of the results

Asymmetric Group Velocity Dispersion and Pulse Distortion in a Uniform Fiber Bragg Grating

In a uniform fiber Bragg grating, if the input signal is a Gaussian pulse the dispersion is zero near center wavelength and becomes appreciable only near the band edges and side lobes of the reflection spectrum. However for chirped Gaussian pulses, group velocity dispersion and the reflected light must become asymmetric. Here the chirped Gaussian pulses can be treated as a symmetric but nonuniform input signal. The present paper describes that for the case of symmetric Gaussian pulse, the group velocity dispersion and pulse distortion remain symmetric however strong the grating may be. On the other hand both tend to be more asymmetric for the case of strong grating while the input signal is symmetric with nonuniform shape

Modeling of single mode optical fiber having a complicated refractive index profile by using modified scalar finite element method

A numerical method based on modified scalar finite element method (SC-FEM) is presented and programmed on MATLAB platform for optical fiber modeling purpose. We have estimated the dispersion graph, mode cut off condition, and group delay and waveguide dispersion for highly complicated chirped type refractive index profile fiber. The convergence study of our FEM formulation is carried out with respect to the number of division in core. It has been found that the numerical error becomes less than 2 % when the number of divisions in the core is more then 30. To predict the accurate waveguide dispersion characteristics, we need to compute expression (d^2 (Vb))/(dV^2 ) numerically by the FEM method. For that the normalized propagation constant b (in terms of β) should be an accurate enough up to around 6 decimal points. To achieve this target, we have used 1 million sampling points in our FEM simulations. Further to validate our results we have derived the higher order polynomial expression for each case. Comparison with other methods in calculation of normalized propagation constant is found to be satisfactory. In traditional FEM analysis a spurious solution is generated because the functional does not satisfy the boundary conditions in the original waveguide problem, However in our analysis a new term that compensate the missing boundary condition has been added in the functional to eliminate the spurious solutions. Our study will be useful for the analysis of optical fiber having varying refractive index profile

Dispersion characteristics of novel class multi-clad dispersion shifted hollow core fibers for WDM optical systems

76-79The design and analysis of multiple-clad hollow core dispersion-shifted fibers have been presented in this paper. Fiber profiles have been designed consisting of a central core that is hollow and outer cladding is silica. The novel refractive index profile has multi-clad for enhanced optical characteristics. Optical fibers with two or more claddings are required for dispersion shifting, dispersion flattening, and other specialized applications. Thus, the hollow core fiber shows the zero dispersion at 1550 nm wavelength. These hollow core fibers have potential application in WDM optical systems