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Waveguide loss measurement- endfire coupling

  1. Jan 8, 2009 #1
    Hi, I am doing an experiment to investigate the propagation loss in some nanophotonics structures.

    The laser light is coupled to the input of the DUT chip via a tapered lensed fiber and the output of the chip is go through a objective then a photodetector.

    The chip is design for telecommunication propose, so wavelenght of interest is around 1550nm.

    I did a spectrum scan for 1500 - 1600 nm and obtained the spectrum as below..


    Unfortunately , the spectrum is with the fabry perot effect.. (the oscillation), i try to calculated the path from the spectrum , but the calculated dimension doesnot match the fiber-chip facet or both end facet of chip .

    So if you gurus outthere can help _?
  2. jcsd
  3. Jan 10, 2009 #2
    I'm not quite sure what your question is exactly.

    There are some things that you should clear up:
    - What wavelength laser are you putting into your chip? Is it broadband?
    - The fabry-perot effect is arising from the reflections within the chip?
    - If the chip is designed for 1550nm, why are you trying to measure spectral losses? Why can't you use a 1550nm source and just measure the total average power at the output?
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