Cutoff Wavelengths
Click the “Cutoff” icon in the “Navigator” pane. The “Cutoff” dialog box appears. Press “Recalculate” first to obtain the mode list. If the fiber is single-mode, reduce the wavelength value using the edit box with the same name (to 0.5 microns in the picture below). Two types of cutoff calculations are currently supported and respectively…
Birefringence
Click the “Birefringence” icon in the “Navigator” pane. The “Birefringence” dialog box appears. Step Action 1 In the “Birefringence” dialog box, check the “Induced by Perturbation Parameters” option. The “Photoelastic Constants” entries become available. 2 In the “Photoelastic Constants” section, enter: Young Modulus 7750000000, C 3.44e-011, Poisson Ratio 0.164. 3 In the “Induced by Perturbation”…
Polarization Mode Dispersion
Click the “PMD” icon in the “Navigator” pane. The “Polarization Mode Dispersion” dialog box appears. To execute the polarization mode dispersion calculations, leave the defaults and press “OK”. The program calculates the polarization mode dispersion and updates the “PMD” tab in the “Views” window.The “PMD” dialog box appears automatically showing numerical values related to the…
Joints
The “Joints” tool shows the actual calculated points of a curve. Do the following steps: Step Action 1 Select a tab in the “Views” window, for example the “Modal Index” tab. 2 Press the “Joints” button on the “Graph Tools” toolbar or, select the “Joints” item from the floating context menu, accessible by right clicking…
Zoom
“Zoom X”, “Zoom XY” and “Zoom Off” are convenient tools for expanding a portion of the graph. “Zoom X” expands the view only in horizontal direction, “Zoom XY” – in both. Do the following steps: Step Action 1 Select, for example, the “Material Loss” tab in the Views window. 2 Select “Zoom XY” from the…
Measure
The “Measure” tool measures the difference between two points of the curve. Do the following steps: Step Action 1 Select, for example, the “Profile” tab in the Views window. 2 Select “Measure” from the “Graph Tools” floating menu or the “Graph Tools” toolbar. 3 With the left mouse button, click-and-drag to measure the coordinates’ difference.…
Tracking
The “Tracking” tool shows the XY coordinates of a point of a curve. Do the following steps: Step Action 1 Select the “Group Delay” tab in the Views window. 2 Select “Tracking” from the “Graph Tools” floating menu or the “Graph Tools” toolbar. 3 With the left mouse button, click-and-drag to track the coordinates. 4…
Legend
The “Legend” tool shows the short descriptions of the curves in multi-curve graphs. Its use is identical to that of the other graph tools. The legend can be dragged, so the user can position it anywhere on the “Views” tab.
Refractive Index of Fibers
Host materials Optical telecommunication-grade fibers are made usually from silica glasses. The high purity glass is called the host material or substrate. Its bulk refractive index usually defines the refractive index of the fiber cladding. Adding dopant materials to the host material forms the fiber core. Dopant materials To change the refractive index of optical…
Fiber Propagation Modes
Scalar fiber modes The designation of Linearly Polarized (LP) Fiber modes is based on the assumption of weak guidance. Weakly guiding fibers have a small difference between core and cladding refractive index. Two numbers designate the LP (m, n) modes: m – azimuthal number n – orbital number where m = 0, 1, 2, ……
Group Delay and Dispersion Definitions
Material dispersion of the bulk glasses If the refractive index of the fiber material varies with wavelength, thus causing the group velocity to vary, it is classified as material dispersion. The group delay Tg is given by the product of the propagation distance z by the first frequency-derivative of the propagation constant: where n is…
Mode Field Diameter and Mode Area Definitions
Mode field diameter and area importance The Mode Field Diameter (MFD) is an important parameter related to the optical field distribution in the fiber. It has been shown that MFD provides useful information about the cabling performances, such as possible joint, macrobending, and microbending losses. The effective area of the fibers has a direct relation…
Cutoff Wavelengths
The cutoff wavelength for any mode is defined as the maximum wavelength at which that mode will propagate. The cutoff wavelength λc of LP11 is an important specification for a single-mode fiber. The operation wavelength must be greater than the cutoff wavelength of LP11 to operate the fiber in a single mode regime. λc can be determined analytically…
Fiber Loss Models
Fiber propagation loss definition The total fiber loss can be divided into material losses and fiber induced losses. Material losses include Rayleigh scattering, ultraviolet (UV), infrared (IR) absorption, and hydroxyl (OH) absorption losses. Material losses are the limiting losses in fibers. Fiber loss is defined as the ratio of the optical output power Pout from…
Fiber Birefringence Models
Fiber birefringence definition The birefringence is defined by the difference between the propagation constants of the polarization Eigenmodes, that is: The Differential Group Delay (DGD) per unit length is defined by: Intrinsic perturbations birefringence Intrinsic perturbations are accidentally introduced in the manufacturing process and are permanent feature of the fiber. These include a noncircular core…