Lesson 16: Graded Index Fiber Modes

Introduction

Optical fiber is an important component of any device used for making fiber directional couplers and for launching and receiving light from an integrated optical waveguide In a device where a small length of fiber is used, the only characteristics needed to simulate for a fiber are the effective mode indices and mode field profiles.…

Graded Index – Core Fiber

Graded Index Core fibers with α – refractive index profile in the core are often desired for several applications in telecommunications, such as shifting zero dispersion wavelength to 1.55 microns.We will demonstrate the design for a triangular core fiber ( α = 1 ). We will also compare the results of the 3D Mode Solver with the Finite Difference Method…

Fiber Parameters and Refractive Index Profile of Triangular Core Fiber

Core radius: 3.00μm Refractive index of core: 1.48 Refractive index of cladding: 1.444 Wavelength: 1.55μm Figure 1: Refractive index profile of a triangular core fiber The procedures are: •     Creating the material •     Defining user variables •     Defining user functions •     Defining the User defined profile •     Defining the layout settings •     Creating the linear…

User Function Profile

The Triangular core fiber can be defined as: To implement the above equation in User Function Profile, we will first explain the User Variables and User Functions (see Table 12). Table 12: User Variables and User Functions Therefore, Triangular Core Fiber equation can be defined as follows: with the limits as follows:

Developing the User Defined Profile

In order to define the profile, perform the following procedures. Creating the material Step Action 1 From the File menu, select New.The Initial Properties dialog box appears. 2 Click Profiles and Materials.The Profile Designer opens. 3 In the Materials folder, right-click the Dielectric folder and select New.The Dielectric dialog box appears. 4 Create the following…

Defining User Functions

To define the user functions identified within Table 12 and in Equation 1 and Equation 2, perform the following procedure. Step Action 1 In the Profile Designer, select Tools > Edit Variables and Functions. The Variables and Functions dialog box appears. 2 On the User Function tab, type the following: Function specification: Delta(n_core,n_cl)Expression: (n_core*n_core-n_cl*n_cl)/ 2/…

Defining the User Defined Profile

Step Action 1 In the Profile Designer, right-click the Profiles folder, and select User Function Profile > New. The User Function Profile dialog box appears. 2 Type/select the following: Profile name: GradedFibre Function specification: fgr(x,y) Function body: n_core*sqrt(1-2*Delta(n_core,n_cl)*(pow((r(x,y)/radius),1))) 3 Select Use limits and type the following: Use limits: x*x+(y-y0)*(y-y0)<radius*radius 4 Make the following associations on the…

Defining the Layout Settings

Step Action 1 In the Layout Designer, select Edit > Wafer Properties. 2 Type/select the following: Wafer Dimensions tab Length (μm): 100 Width (μm): 30 2D Wafer Properties tab Material: cladding 3D Wafer Properties tab Cladding Material: cladding Thickness: 0.1 Substrate Material: cladding Thickness: 30 3 Click OK to apply the layout settings.

Creating the Linear Waveguide Fiber

To create the linear waveguide fiber, perform the following procedure. Step Action 1 In the layout, draw a linear waveguide. 2 To open the properties dialog box for the waveguide, double-click on the waveguide. The Linear Waveguide Properties dialog box appears. 3 In the Linear Waveguide Properties dialog box, type/enter the following: Start offset: Horizontal:…

Setting Simulation Parameters

To set the simulation parameters, perform the following procedure. Step Action 1 In the Simulation Parameters dialog box, click the 3D Isotropic tab. 2 Type/select the following: Number of points in mesh Number of points/ μ m X: 10 Y: 10 View cut X Mesh Pt: 151 Y Mesh Pt: 151 3 Click OK.