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At the lowest layer of today's communication networks is an optical line system (OLS), a physical network of equipment, which carries high-frequency analog light signals over thousands of kilometers. Traditionally, an OLS was delivered as a turn-key solution by a single vendor. Within an OLS, reconfigurable optical add/drop multiplexers (ROADMs) are active devices responsible for routing spectral chunks between input and output ports. ROADMs are arguably the most complex physical component of an OLS. In this paper, we describe an open design of a Czech Light ROADM, including the optical hardware, electronics, software, and the northbound communication interface. The performance of the ROADMs is evaluated in two test scenarios.

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Abstract. The infrastructure essentialities for accurate time and stable frequency distribution are presented. Our solution is based on sharing fibers for a research and educational network carrying live data traffic with time and frequency transfer in parallel. Accurate time and stable frequency transmission uses mainly dark channels amplified by dedicated bidirectional amplifiers with the same propagation path for both directions of transmission. This paper targets challenges related to bidirectional transmission, particularly, directional nonreciprocities. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

The performance of future ultra-long haul communication systems exploiting phase-encoded signals is likely to be compromised by noise generated during signal transmission. One potential way to mitigate such noise is to use Phase Sensitive Amplifiers (PSAs) which have been demonstrated to help remove phase as well as amplitude noise from phaseencoded signals. Recently, we showed that a PSA-based signal regenerator based on degenerate four-wave mixing can be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). The developed regenerator was also able to perform simultaneous wavelength conversion and multicasting, details/analysis of which are presented herein. However, this scheme was tested only with artificial noise generated in the laboratory and with the regenerator placed in front of the receiver, rather than in-line where even greater performance benefits are to be expected. Here, we address both theoretically and experimentally the important issue of how such a regenerator, operating for convenience in a multicasting mode, performs as an in-line device in an installed transmission fiber link. We also investigate the dispersion tolerance of the approach.