Theory and measurements of speed-of-light effects in long cavity fiber Fabry-Perot scanning interferometers

Analytical and experimental results for high-resolution, long-cavity, fiber Fabry-Perot scanning interferometers show an inverse square-root dependence of bandwidth on cavity length when the scan time per fringe approaches the inverse bandwidth of the interferometer. In this regime transmission fringe distortions due to the finite speed of light occur even at moderate scanning rates of 2 to 10 ms per free spectral range for cavity lengths of 5 to 25 m, respectively. A numerical model incorporating propagation and mirror losses in a Fabry-Perot cavity demonstrates good agreement with experimentally observed rise-time increase, fall-time ringing, and overall attenuation of the bandpass function for very long cavity interferometers.<
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