Dispersion Shifted Fiber

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Optical Fiber Design Software

Dispersion Shifted Fiber (Optical Fiber)

In this example, we will show you how to simulate optical fiber that has a triangular
with annular ring profile. In addition, we will show you how to optimize given fiber
profile to have zero dispersion at 1550 nm by the powerful parameter scan routines
of OptiFiber.

You can find this example as the DSF.fcd file in the Samples directory.

Defining fiber profile

To define a fiber profile, follow these steps:

StepAction
1From the “File” menu click “New” to open a new project.
2Click the Fiber Profile icon in the “Navigator” pane.
3In the Fiber Profile dialog box, add four regions: “Region 0” through “Region 3”For “Region 0”, enter the following data:
Width: 3.1
Profile: function
Function: linear
Refr. Index: Define: Start = 1.4615, End = 1.44692
Steps: 100
Click ApplyFor “Region 1”, enter the following data:
Width: 0.6
Profile: constant
Index: 1.44692
Click ApplyFor “Region 2”, enter the following data:
Width: 1.5
Profile: constant
Index: 1.45
Click ApplyFor “Region 3”, enter the following data:
Width: 57.
Profile: constant
Index: 1. 44692
Click ApplyEnter the wavelength value 1.3 microns.

Your fiber should look like the one below:

Optical Fiber - Fiber Profile

4Click “OK” to close the “Fiber profile” dialog box.

Finding the zero dispersion wavelength

To find the zero dispersion wavelength, follow these steps:

StepAction
1Click the “Modes” icon in the “Navigator” pane
2Select the “LP Modes (Matrix Method)” option
3Press “Recalculate ”. The program provides the modal index at the given wavelength and shows a preview of the modal field.
4Click “OK” to leave the “Modes” dialog box.
5Click the “Scan Fundamental Mode” icon in the “Navigator” pane.
6In the “Properties of Fundamental Mode” dialog box, click “Calculate” to scan “Wavelength” from 1.4 to 1.6 in 50 steps.
7Go to “Dispersion” view tab. The zero dispersion wavelength is located in the vicinity of 1513 nm.

Your “Dispersion” view tab should look like this:

Optical Fiber - Dispersion view tab

Optimizing profile for a required zero dispersion wavelength

Now, we can use the powerful capability of OptiFiber to scan over our design
parameters. Let’s define, as a design goal, to achieve zero dispersion at a certain
wavelength, say 1550 nm. As we will see, we can accomplish that by changing, for
example, the distance between the triangular core and the annular ring, i.e. the width
of “Region 1”.

When we find the optimal width we can use it to calculate the global dispersion
characteristics vs. wavelength.

StepAction
1Now, go back to the “Properties of Fundamental Mode” dialog box by
selecting “Scan Fundamental Mode” in the “Navigator” pane.
2In the “Properties of Fundamental Mode” dialog box, select “Region 1” from the “Scan” upper list, then select “Width” from the “Scan” lower list.
3In the “Parameters” section, enter the following values: From 0.1, To 3.1, Steps 30.

Optical Fiber - Properties of Fundamental Mode

4Click “Calculate”.
5Go to “Dispersion” view tab. The dispersion vs. the width of the intermediate layer is shown there:

Optical Fiber - Dispersion view tab

66. From the previous dispersion vs. wavelength picture we know that we need ~ 3 [ps/nm/km] reduction of the total dispersion at 1550 nm. With the left mouse button, click-and-drag over the “Total dispersion” curve to find the point, whose dispersion is 3 [ps/nm/km] less than the dispersion,
corresponding to the current width of 0.6 ìm. One can see that the 3
[ps/nm/km] reduction falls between the widths of 1.3 and 1.4 ìm.
7Go back to the “Fiber Profile”, select “Region 1”, and change its width to 1.32 ìm.
8Go to the “Properties of Fundamental Mode” dialog box and scan over the
wavelength from 1.4 to 1.6 ìm in 50 steps.
9Go to “Dispersion” view tab. The zero dispersion wavelength is 1550 nm.

You just optimized the fiber design to obtain the zero-dispersion wavelength close to
1.55 microns.

Your “Dispersion” view tab should look like this:

Optical Fiber - Dispersion view tab

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