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

Design of a large effective-area nonzero-dispersion fiber for DWDM systems

In this paper, we analyze and propose an optimum index profile which can give a larger core effective area with nonzero-dispersion characteristics. The index profile is modeled by an exponentially modulated linear chirp profile function. A linear finite-element method (LFEM) is used for computing the transmission characteristics of an optical fiber having an arbitrary refractive-index profile. The optimum index profile can give a core effective area of 117 mum(2). The dispersion varies linearly from 2.5 to 4.5 ps / nm . km with a dispersion slope of 0.065 ps / nm(2) . km over the 1.53-1.56 mum wavelength range. Sensitivity analysis for the designed fiber characteristics is also studied. The bend loss is about 0.001 dB / m for a bend radius of 100 mm. (C) 2001 , Inc

Dispersion characteristics of an optical fiber having linear chirp refractive index profile

We analyze the dispersion characteristics of an optical fiber having linear chirp type refractive index profile. The chirp type profile is general in nature and by controlling the profile parameters, one can obtain a wide range of profiles from simple step index to complex multiple cladded type. The problem is treated as an optimization problem in the profile parameter space. It is shown that a variety of dispersion characteristics can be realized with proper optimization of the profile parameters. Linear finite element method (LFEM) is employed for computing the modal fields and propagation constants. Tolerance analysis of the fiber dispersion characteristics and bending loss calculation are also carried outIEE

Design of subpicosecond dispersion-flattened fibers

Dispersion flattened (DF) fibers are required for wide-band WDM systems. The DF fibers designed in the past have dispersion in the range of 2.0-3.0 ps/km-nm. In this letter, we define a generalized refractive index profile that can be characterized by few controlling parameters. An optimum refractive index profile is obtained by minimizing the maximum dispersion over the wavelength range of 1300-1600 nm with respect to profile parameters. The designed fiber gives dispersion less than 1.0 ps/km-nm over 1350-1590 nm wavelength range. Sensitivity of the dispersion performance to the profile parameters is also discussed.IEE

Analysis of cascaded dispersion compensation system

In this paper, a pulse propagation analysis of cascaded compensation scheme using higher order mode propagation is carried out. The output of the cascaded system consists of compensated and uncompensated components. A generalized expression for the compensated and uncompensated components has been derived. Results show that for a broadband efficient mode converter only previous one or two sections contributes to the pulse broadening of the uncompensated components. For 50 sections (2000 km), the ratio of uncompensated to the compensated power is 24 dB for a mode converter efficiency of 100%.© IEE