How to figure out the residual dispersion?

[QIAN Tianwen]

Hi Optiwave Team,

I’ve been using optisystem for my graduation project these days, which is about dispersion management and compensation. When I was reading your Tutorials, which named “Dispersion Compensation Schemes – A System Perspective” (https://optiwave.com/resources/applications-resources/optical-system-dispersion-compensation-schemes-a-system-perspective/), the figure which is at the bottom of the article (see attachments) troubles me a lot. The residual dispersion is a key point in my project, so I want to know how to measure it and draw a figure like that. Thank you!

With regards
QIAN Tianwen

[Damian Marek]

The residual dispersion is calculated from the dispersion present in the fiber and the dispersion caused by introducing the grating. The figure is simply demonstrating that using a FBG to account for the total fiber dispersion gives maximum performance.

However! You could conceive a simulation that would attempt to find the amount of dispersion experienced by a pulse. You would not be able to separate the dispersion from nonlinearity, unless you disabled that part of the fiber model, but you could use the optical time domain visualizer to view the chirp/phase for a pulse and from that value calculate the residual dispersion, assuming an input pulse without chirp.

Regards

[QIAN Tianwen]

Thank you for your reply!
Could you tell me the method to calculate the residual dispersion by the chirp/phase? I think it’s very helpful for me. Then I could figure the total residual dispersion by calculating the dispersion experienced by the single pulse.

[Damian Marek]

There is a relation between the chirp of a gaussian pulse and the amount of dispersion it has experienced from propagation in a fiber. There should be plenty of references out there that describe it, but I got it from Govind Agrawal’s book on Fiber Optic Communication Systems.

Regards

[QIAN Tianwen]

Thank you for your suggestion! I’am going to find it out! Thank you!

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