Narrowband optical filtering for background-limited photon-counting free-space optical communications

K. Shtyrkova; I. Gaschits; D. O. Caplan

doi:10.1117/12.2510642

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4 March 2019 Narrowband optical filtering for background-limited photon-counting free-space optical communications

K. Shtyrkova, I. Gaschits, D. O. Caplan

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Proceedings Volume 10910, Free-Space Laser Communications XXXI; 109100F (2019) https://doi.org/10.1117/12.2510642
Event: SPIE LASE, 2019, San Francisco, California, United States

Abstract

For free-space optical (FSO) communications through the turbulent atmospheric channel, multi-spatial-mode photoncounting detectors can provide an attractive high-sensitivity receiver solution. However, multi-mode detection also increases optical background noise, which can degrade the overall system performance. Narrow band optical filtering becomes an important background rejection tool that can enable good performance in background-limited conditions. Here, we report the development of low-insertion-loss high-contrast-ratio optical filters at 1.55μm that are well suited for FSO communications. The filter has less than 0.7 dB insertion loss, 46 dB contrast ratio, 2.9 GHz 3-dB bandwidth, and 3.5 GHz noise-equivalent bandwidth, which is well matched to 1 GHz return-to-zero (RZ) pulsed waveforms. Other factors that influence filter performance and stability such as angular and temperature dependencies are characterized. Additional theoretical analysis and experimental results highlighting the trade-offs between spectral bandwidth, spatial bandwidth, filter insertion loss, and temperature-induced performance changes are presented. When coupled with photon-counting detection, these filtering techniques can enable sensitive FSO receiver operation, even in the presence of significant background.

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K. Shtyrkova, I. Gaschits, and D. O. Caplan "Narrowband optical filtering for background-limited photon-counting free-space optical communications", Proc. SPIE 10910, Free-Space Laser Communications XXXI, 109100F (4 March 2019); https://doi.org/10.1117/12.2510642

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