D-Shaped Fiber

[Juliana Carvalho]

Dears,

Is it possible to simulate a D-shaped fiber with Optiwave?

Best regards,

Juliana

[Damian Marek]

Hi Juliana,

If you are looking at the modes of such a fiber then yes OptiMode (which comes with either OptiFDTD or OptiBPM) can solve for arbitrary geometries.

Depending on if you would to perform some different simulation bending, coupling etc. that would determine whether OptiFDTD or OptiBPM would be better suited for the job.

Regards

[Juliana Carvalho]

Dear,

Do you have any example about D-Shaped fiber design, that I could see? I don’t know how to design this because the layers are concentrics.

Thanks again.

Best regards,

Juliana.

[Damian Marek]

Hello,

I could make one pretty easily. Do you have an article or diagram of the fiber, just so I have a pertinent example.

Damian

[Juliana Carvalho]

Dear Damian,

It is attached a figure that is an example about what I want to do.
Thanks very much!

Juliana

Attachments:

1. 

   D-shaped-fiber.png
   

[Damian Marek]

Hi Juliana,

I made a template for a D Shaped Fiber in the attached OptiMode file. You can modify the existing geometry or refractive indices to more accurately portray your project.

Regards

Attachments:

1. 

   DShapedFiber.png
   

1. DShapedFiber.mxd

[Juliana Carvalho]

Dear Damian,

Thank you very much!!! But, I can’t open the file because I don’t have the new software version. Please, could you send me with the 11 version?

Thanks again!!!

Best regards,

Juliana.

[Damian Marek]

Hi Juliana,

Unfortunately I don’t have access to older versions of the software. It should not be too hard to build using circular profiles and two rectangle profiles thought. Let me know if you run into any problems.

Regards,
Damian

[Juliana Carvalho]

Hi Damian,

I tried to develope the same project and fortunately I get the software idea. So, I have now other doubts:
Is it possible evaluate the power signal propagation (in any lenght, like 1m, for example) in Optimode design?
In design profile, in channel option have an option to insert “width” value (fx). But, when I changes this value, I didn’t saw any modification in the design. What is the meaning of this parameter?
I have a lot of others doubts, but, in this moment, please, I need to know these to continuos with my work.

Thanks again!

Regards,

Juliana

[Damian Marek]

Hey Juliana,

Yes you can include a imaginary part of the index of refraction of your profile materials. When the mode solver finds the modes it will give the complex effective index which can be converted to a loss or dB/km.

When setting the width in the Profile Manager you are setting the default waveguide parameters, so it will not change the profiles already placed in your project. Any new waveguide using that profile will reflect the different width. Instead double clicking the feature and changing the width directly will change the width immediately.

Regards

[Juliana Carvalho]

Dear Damian,

Thanks for your informations!
I didn’t understand very well the meaning of calculate the loss through the effective index… Anyway, I have other doubts:
-Before the simulation, I have a warning, like is attached. But, after that is possible to see the result. But, I don’t know if is it bad or not.
-In this case of design (d-shaped fiber), the analyzes have to be anisotropic?

Best regards,

Juliana.

[Damian Marek]

Hi Juliana,

Which version(s) of which product(s) are you using? OptiMode comes with both OptiFDTD and/or OptiBPM, it might help diagnose this error. Have you tried uninstalling and reinstalling?

The analysis does not need to be anisotropic unless the material you are using is.

[Juliana Carvalho]

The warning.

Attachments:

1. 

   warning.png
   

[Juliana Carvalho]

Dear Damian,

About the template for a D-Shaped Fiber, I didn’t understand why do you use the channel “AirFill”?

Others doubts about Optimode:

– A fiber SMF-28 presents attenuation equal 0.2 dB/km> But, when I simulate it, in the results (Modal index, attenuation) I didn’t see any attenuation (zero). Why?

– In Default waveguide (layout window), what have to be the inserted parameter correspondent?

Thanks again!

I am waiting a help.

Regards,

Juliana.

[Damian Marek]

The AirFill channel was used to create the straight edge of the “D”. I overlapped an index of refraction of 1 with the fiber material, so that you could have different widths of the Nm material. If the width would be very narrow the circular profile underneath might appear again above the square Nm material.

To calculate the loss of the mode you need to do a simple calculation by hand. The mode solver will give you the modal index, which can have an imaginary component. If you are unfamiliar with the calculation I would suggest taking a look at Agrawal’s Optical Fiber Communication textbook, which explains the attenuation coefficient. In any case to convert the imaginary part of the modal index into a loss (dB/km) you can use the following equation:

Loss = (-2*(Nimag)*2*PI/lambda*4.34)

the length units will be the same as the wavelength units.

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