Various examples relate to a concept for generating and using a preamble for transmissions in a point-to-multipoint network, such as a Passive Optical Network (PON). A preamble generation apparatus for generating a preamble for a communication over an optical network comprises circuitry that is configured to generate a first subsection of the preamble, the first subsection of the preamble comprising a repetitive signal pattern. The preamble generation apparatus is configured to generate a second subsection of the preamble subsequent to the first subsection, the second subsection comprising a pseudorandom signal sequence.

A baseline difference is determined between a slave line card time stamp corresponding to a slave line card frame sync signal and a master line card time stamp corresponding to a master line card frame sync signal. The slave line card generates subsequent slave line card time stamps for subsequent slave line card frame sync signals and the master line card generates subsequent master line card time stamps for subsequent master line card frame sync signals. Current differences are determined between subsequent slave line card time stamps and the subsequent master line card time stamps and the current differences are compared to the baseline difference. When a mismatch difference occurs (current difference differs from the baseline difference), the mismatch difference causes a phase-locked loop in the master line card to be adjusted or an offset to be provided to the master line card time of day counter.

Disclosed are a time synchronization method, a time synchronization device, a time synchronization apparatus and a storage medium. The method includes: periodically generating, by a local device, a synchronization request signal, and determining a first reference ID of the local device; sending the synchronization request signal and the first reference ID to peer devices; receiving a second reference ID and time information sent from each peer device through a communication link; and updating time of the local device according to the time information transmitted from a calibration link, the calibration link being a corresponding communication link of a target reference ID in second reference IDs sent from the peer devices.