there is a fiber coupled EOM setup after the double pass AOM setup. the intensity of light is constant(checked with power meter) before the input of EOM but there is a 10% fluctuations in the power just after the EOM, due to which I am unable to lock to a signal that i see in the oscilloscope. This signal is fluctuating up and down on the screen. Is there any solution or could I be doing wrong somewhere, although I have realigned all optical elements numerous times to get it done correctly, but still facing the problem.
Have you checked the polarization state of the input light after the AOM? Maybe there is a problem with your bias controller.
for the polarization, i placed a half wave plate just before the fiber coupled EOM, still it didn't matter much.
Is it possible that the problem may be because of the current applied (bias voltage), or polarization state is changing at random inside the EOM?
Maybe you can try a polarization controller, I once faced a similar problem with my IQ modulator when I input a non-PM light. The signal in the oscilloscope also fluctuates and the bias voltage is changing all the time (scanning). I solved this problem by replacing my setup with PM components, hope it works for you.
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