An optical cable router is disclosed. The optical cable router is to couple to rocker-arm plenums of a modular computing system. The optical cable router includes a crossbar that includes an optical cable cavity. The optical cable cavity has a plurality of optical cables and an access panel. The optical cable router further includes optical connectors, each of which is coupled to a respective optical cable of the plurality of optical cables. Each optical connector is also coupled to a respective optical connector of a respective modular computing device retained in the modular computing system.