Single Mode Fiber

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Optical Fiber Design Software

Single Mode Fiber (Optical Fiber)

In this example, we will show you how to simulate a simple single-mode optical fiber
that is optimized for use in the 1310 nm wavelength region. The main features of
OptiFiber will be addressed in this example. You can find this example as the SMF-
28.fcd file in the Samples directory.

Defining fiber profile

To define a fiber profile, follow these steps:

1From the “File” menu click “New” to open a new project.
22. Click the “Fiber Profile” icon in the “Navigator” pane.
33. In the “Select Profile Type” dialog box click “Refractive Index Profile”
44. In the “Fiber Profile” dialog box add two regions: “Region 0” and “Region 1”For “Region 0”, enter the following data:
Width: 4.15
Profile: constant
Index: 1.45213
Click “Apply”

For “Region 1”, enter the following data:
Width: 58.35
Profile: constant
Index: 1.44692
Click “Apply”

Enter the wavelength value 1.3 microns.

Your fiber profile should look like the one below:

Optical Fiber - fiber profile

Note that both the absolute values of the reference indexes and the normalized
difference Δ are shown.

Defining dispersion models

To define a dispersion model, follow these steps:

1In the “Fiber Profile” dialog box, select “Define” in the “Material Properties” group of controls.
2In the “Material Properties” dialog box, select “Define” in the “Host” section.
3In the “Parameters of Material” dialog box, select “Pure Silica” from the library
and press Get, followed by pressing OK to close the “Parameters of Material” dialog box. You can see in the “Material Properties “ dialog box that the host material is now “Pure Silica”.
4Similarly as in the previous step, define 3.1% germanium-doped silica for the “Dopant+” material
5Similarly as in the previous step, define 1% fluorine-doped silica for the
“Dopant-“ material. Thus you defined two reference materials that will be used to calculate the material dispersion and the profile dispersion of the fiber.
6Press OK in the “Material Properties” dialog box to close it.
7 Press OK in the “Fiber Profile” dialog box to close it.

Your “Material Properties” dialog box looks like this:

Optical Fiber - Material Properties

Calculating fiber modes

To calculate a fiber profile, follow these steps:

1Click the “Modes” icon in the “Navigator” pane
2Select the “LP Modes (Matrix Method)” option
3Press “Recalculate Modes”. The program provides the modal index at the given wavelength and shows a preview of the modal field.
4In the “Views” window, select the “Mode Field” tab to view the modal field.
5From the “Graph Tools” toolbar select “X Cut”, then click-and-drag the cursor over the graph to inspect the mode field normalized “X-section”. The default color for “X Cut” lines is green.
6From the Graph Tools toolbar select “Y Cut”, then click-and-drag the cursor over the graph to inspect the mode field normalized Y-section. The default color for “Y Cut” graph lines is red.

When you click-and-drag the left mouse button inside your “Mode Field” view tab with
“X Cut” and “Y Cut” active, then the view looks like this:

Optical Fiber - Mode Field

Calculating cutoff wavelength

To calculate the cutoff wavelength, follow these steps:

1Click the “Cutoff” icon in the “Navigator” pane.
2Select the “LP Modes (Matrix Method)” option.
3Press “Recalculate”. The program shows guided modes on the list. If only LP01 is supported – decrease the wavelength.
4Select the “LP11” mode on the list.
5Press the Calc. “Cutoff” button. The program shows:
— a “theoretical” cutoff wavelength value of 1.33204 microns.
— a “ITU-T” compliant cutoff value of 1.231 microns.

Calculating properties of fundamental mode

To calculate the properties of the fundamental mode, follow these steps:

1Click the “Scan Fundamental Mode” icon in the “Navigator” pane.
2In the “Properties of Fundamental Mode” dialog box, select all available
“Calculate” options
3Leave the defaults for material, bending, and splice loss parameters
4In the “Scan” section list, select “Wavelength”, which is also the default
option. 68
5In the “Parameter” section, enter “From” = 1.2, “To” = 1.6, “Steps” = 100.
6Click “Calculate”.

Viewing results

You can inspect the output graphs in the Views window by selecting appropriate tabs:

  • “Modal Index” tab: Plot of the modal index vs. the current scanning parameter, i.e. wavelength
  • “Group Delay” tab: Plots the group delay vs. the scanning parameter.
  • “Dispersion” tab: Plots material, waveguide and total dispersion vs. the scanning parameter. The zero dispersion wavelength and the slope are shown on the graph.
  • “Mode Measures” tab: Plots the near-, far-field, effective mode field diameter and the effective mode area vs. the scanning parameter.
  • “Material Loss” tab: Plots the material loss vs. wavelength.
  • “Bending Loss” tab: Plots the micro and macro bending losses vs. the scanning parameter.
  • “Splice Loss” tab: Plots the splice loss vs. the scanning parameter.
  • “Eff. Nonlinear RI” tab: Plots the effective nonlinear refractive index of the fiber vs. the scanning parameter.

Simulating polarization mode dispersion


To simulate the birefringence, follow these steps:

1Click the “Birefringence” icon in the “Navigator” pane
2In the “Birefringence” dialog box, check the “Induced by Perturbation
Parameters” option. The “Photoelastic Constants” entries become available.
3In the “Photoelastic Constants” section, enter: Young Modulus 7750000000, C 3.44e-011, Poisson Ratio 0.164.
4In the “Induced by Perturbation” Parameters section, check “Extrinsic”, “Bending”, and “Fiber Spooled With Tension”.
5Enter the “Bending” value 0.12
6Enter the “Fiber Spooled with Tension” value 0.5.
7In the “Output” section, enter “Spectral Range” 0.4 and “Number of Steps” 51.
8Press OK to close the “Birefringence” dialog box
9Go to the “Birefringence” view tab. The birefringence and Differential Group Delay (DGD) vs. wavelength are plotted there.

Your “Birefringence” view tab should look like this:

Optical Fiber - Birefringence

Polarization mode dispersion

To simulate the polarization mode dispersion, follow these steps:

1Click the “PMD” icon in the “Navigator” pane
2Define the parameters for PMD simulation: Fiber Length 1000, Coupling Length 20. The Birefringence Characteristics are provided for your information and are disabled in this dialog box.
3Choose “Spectral simulation”: Spectral Range 0.1, Number of Steps 201.
4Press “OK” to close the polarization Mode dispersion dialog box and start the simulation.
5Go to the “PMD” graphics tab. The first order and second order PMD vs. wavelength are plotted for spectral simulation. (For Ensemble simulation, the first order PMD vs. Number of Runs would be plotted).

Your “PMD” view tab should look something like this:

Optical Fiber - PMD view tab

Also, you will have the mean value and the root mean square, (RMS value) of the first
and second order PMD displayed in a separate window.

Optical Fiber - PMD

Performance Characterization

Here is the table that compares OptiFiber results with a typical fiber (Corning SMF-

Characterized ParameterCalculated ValueTypical value
Zero dispersion wavelength, λ01.309 μm1.302 μm < λ0 < 1.322 μm
Zero dispersion slope, S00.0856 ps/(nm2 *km)<0.089ps/(nm2 *km)
Eff. MFD at 1310nm8.9 μm9.20 ± 0.4μm
EFF. MFD at 1550nm9.9 μm10.4 ± 0.5μm
Effective group index1.46761.4675
Cut-off wavelength of LP111.23 μm<1.260 μm

The data of SMF-28 were taken from the public-domain specifications at Corning’s

Corning is a registered trademark and SMF-28 is a trademark of Corning
incorporated, Corning, NY, USA.

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