This application relates to clock synchronization methods optical head ends, and optical terminals. In an example method, the optical head end receives a first packet from a controller. The first packet includes service data to be transmitted to a plurality of slave stations. The optical head end generates a second packet based on the first packet. The second packet includes the service data and time information. The time information indicates an execution time point at which the plurality of slave stations perform an operation based on the service data. The optical head end further sends the second packet to the plurality of optical terminals to request the plurality of optical terminals to control the plurality of slave stations to perform the operation at the execution time point based on the service data.

A control system, includes a master control device configured to control a first controlled object based on time information output from a first clock unit, and a slave control device connected to the master control device via a network and configured to control a second controlled object different from the first controlled object based on control information transmitted from the master control device and time information output from a second clock unit. The time information of the first clock unit and the time information of the second clock unit are time-synchronized.