In optical fibers, there are techniques to suppress some modes like for example coiling or bending the fiber which introduce higher losses for a particular set of higher order modes. The question is: after this coil, when the fiber becomes straight can the suppressed modes reappear and re-establish themselves?
If yes, what are the conditions for this recovery process and how much time is needed to see this phenomenon.
Hello Saddam,
Bending of optical fiber attenuates all the modes including the fundamental mode. But by choosing optimum bend diameter, it is possible to remove higher order modes with least effect on fundamental mode. And yes the modes should reappear if the fiber becomes straight.
Hope this helps.
Thank you for your reply sir. How much distance of straight fiber does this recovery take? Do you have any ref about that?
Hello Saddam,
I would like to correct my answer as I understood your initial question differently.
Pls find my revised answer below.
Fiber bend acts like a mode filter..so once the higher order mode is filtered by bend, it should not reappear in the remaining portion even if it is straight.
It is a common practice in telecom fiber testing to give a small bend at the start of the fiber sample ( 60 mm dia) to filter the LP11 mode.
I will see if I can get ref.
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