Precise timing inside the Pacific Ocean Neutrino Experiment (P-ONE) will be mandatory to allow synchronization of the DAQ systems inside the Precision Optical Modules (P-OMs). The DAQ system is designed to digitize 16 channels of photomultiplier tube waveforms at high speed, with a large buffer and waveform pre-processing capabilities. This requires a fast and reliable data path between P-OMs and shore, as well as sub-nanosecond synchronization amongst P-OMs, while keeping the cable design as light-weight as possible to reduce mechanical stress. To meet these requirements, an optical network based on standard gigabit ethernet on Lattice ECP3/ECP5 FPGAs is presented. It allows syntonous operation of the P-OMs by propagation of a central 125MHz clock in addition to coarse and fine delay measurements on the point-to-point fiber links, and provides Gigabit Ethernet to all endpoints in the network. This allows precise timing and use of commercial off-the-shelf network components inside the P-OMs and the connected mini junction box (mJB), serving as a network hub. This greatly simplifies the design process and makes well-tested, easily integrated network standards available for data transport.
