It would be a great help, if someone can help me out in this topic:
I have a Bragg grating structure fabricated on a waveguide. In the transmission spectrum, a notch was obtained. How can I get the reflection spectra from it? In short, How can I differentiate loss from reflection, (experimentally or theoretically) ?
I tried measuring the reflection spectrum directly (using a circulator) by coupling light into the waveguiding structure. But the fluctuations in the reflections due to uncoupled light is much larger than the power I expect from the reflection.
Dear Harish, from what I understand you have signal to noise problems, so that different strategies can be implemented. First of all I have some concerns:
1. Is the waveguide single mode? Otherwise, the notch in the transmission spectrum may be due to intermodal interference.
2. If you are sure you have a Bragg grating into the waveguide, perform a simple test: see the notch spectral shift with temperature. Losses in waveguide do not have that behavior.
3. In either of the above two cases, i.e., intermodal interference or Bragg grating, you can see the notch spectral shift with temperature. In that case, just check thermo optic coefficient of the material that made the waveguide and perform some computer simulations to distinguish which effect is present.
Dear Pedro Torres.. Thanks a lot for your suggestions.. I will definitely try the temperature dependence of the spectrum..
Yes, my waveguide is single mode, but is of rib structure. Hence, I think there is a possibility of fundamental mode coupling into slab mode.
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