Systems, methods, and computer-readable media are described for performing link training to enable optical pass-through (OPT) capabilities of a network node. OPT capabilities may refer to on-chip wavelength routing for a multi-wavelength data input, whereby an intermediate node detects wavelengths that are intended for OPT and transparently passes the wavelengths through to downstream nodes. When executed at an intermediate network node, an OPT link training algorithm can result in the creation of one or more wavelength routing maps that associate wavelengths received on particular inputs to the node with particular outputs of the node. An intermediate node may generate a respective wavelength routing map for each transmit node from which it receives input data. The wavelength routing maps may together implement OPT capabilities at the intermediate node as each wavelength routing map may indicate the manner in which wavelengths are passed through the intermediate node for a given transmit node.