Opening up ROADMs: Let Us Build a Disaggregated Open Optical Line System

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.