Power Coupling Coefficient in Spatial VCSEL

[Sushank Chaudhary]

Why the power coupling coefficient values are the same regardless different power ratio in Spatial VCSEL at MMF ? Any idea ?

[Damian Marek]

The power coupling coefficient is relative. Changing the absolute input power will not change the percentage of power coupled into a particular mode barring some kind of nonlinear effect.

[Yousef Fazea]

Thank you very much, Mr. Damian and Mr. Sushank

Will designing a new Multimode fiber will help to have a different power coupling coefficient at the MMF.

[Yousef A. Faza]

Hello Mr. Damian and Mr. Sushank

Even if i design a new Multimode fiber, will that help to change the values of the power coupling coefficient? or it the result will always be the same

[Damian Marek]

Changing the multimode fiber will of course change the coupling coefficients, because the modes it supports will differ from the original fiber.

[Yousef Fazea]

Thank you very much Mr. Damian for your prompt responses. It seems that I failed to draw a complete picture regarding my previous question, and I apologize for that.

If I design a new MMF, of course the power coupling coefficient will differ compared to the ready MMF component, because as you kindly stated that each fiber support different modes. However, and this is my question, if i repeat the same scenario again on the “newly designed MMF” whereby if I excite 2 modes (LG00 and LG01) then I did the following:

-First run will divide the power ratio between those two modes equally as (0.5 0.5) and record the power coupling coefficient.
-Second run will divide the power ratio between them, but this time unequally as (0.7 0.3) and record the power coupling coefficient.

Will I have again the same power coupling coefficient or Not?

Much appreciation in advance for your efforts.

[Damian Marek]

The multimode fiber calculates the coupling coefficient individually for each input mode and signal. If your input modes differ in relative power then the modes excited will have different powers as well. You will end up having different power in different modes but the individual power coupling will not change for each input mode.

[Yousef Fazea]

Thank you very much, Mr. Damian

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