Tm doped fiber laser

[Adrian Grzegorczyk]

Hi everyone,

I would like to ask couple question according to my project, that i have beed given by my professor. I have a problem with creating fiber laser, with resonator that consist of 2 Fiber Bragg Grattings and in between them Thulium doped fiber. The problem is that when i want to attach both ports (2 going in and 2 going out) to make light go through first Bragg gratting, than fiber, to second Bragg gratting, that the part of light go through it and the rest reflects back to the fiber, and loops again, it does not work. Everything works fine (program calculate properly) if i plug in in one way from the right or left side of fiber CW diods, but that makes it one way amplifier. I have tried attach from each side one CW laser path but program does not want to calculate this. In system component library is writen that: Tm doped fiber is bidirectional.
-But does it mean (fiber is bidirectional) that light can go through fiber simultanously both ways or that light can be transmited from one way or the other?
-Does any one has idea, how to make it work?
In attachments i have added project with this fiber system working, but as amplifier.

Please help. Thank You for all replies.

[Mohamed A. A. Abouseif]

Hi Adrian,
A few of points you should know when dealing with bidirectional components and resonators:
1. OptiSystem starts to calculate if there is input signals for any component otherwise not calculation starts. So in bidirectional component you should put Null if you want to make it work as an amplifier or one way system.
2. The resonator is affected by the above point (if it has bidirectional component) beside it needs initializer. this might be satisfied by either initializer component or multiple iteration with delay component. In the former option the initializer pass one input (as initializer) one time then the second input would be passed to the output all the time. while in the later option the delay component send null to the input one time before it passes the input signal to the output to force the oscillator to work.

I hope this introduction helps you to understand how oscillator works in OptiSystem.
I encourage you to start with any example of oscillator and see how it works to go further with yours.

Best of luck
Mohamed Abouseif

[Author]

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