The introduction of digital coherent optics has permitted carriers to maintain a profit and a flat capital expenditure despite the constant traffic increase and the stagnant pool of subscribers over the last years. Nowadays, all these coherent devices are capable of transmitting at 400 Gb/s. The two categories available are the standard interfaces (400ZR/OpenZR+) and the proprietary interfaces (Multi-haul). These 400 Gb/s devices are classified by considering their properties and scope, and allow full coverage in the network. Moreover, due to their size, power consumption, and heat dissipation, such devices may be integrated within IP routers enabling a technological convergence toward IP-optical (IPoDWDM) networking.