Precision Time Protocol at Picosecond Scale Over Asynchronous Ethernet

Precise time-distribution is an important prerequisite for many applications in navigation and sensing. The IEEE-1588 Precision Time Protocol (PTP) allows time-distribution over wired computer networks. State-of-the-art PTP implementations such as the White Rabbit Project can achieve picosecond-scale clock synchronization over Ethernet networks spanning many kilometers, but require the use of Synchronous Ethernet (SyncE) and other specialized technology that precludes mobile applications. This paper describes an alternative PTP implementation using a novel digital timestamping circuit that can operate with multiple asynchronous clocks, eliminating the need for SyncE. Under laboratory conditions, a prototype using this approach has demonstrated end-to-end time-transfer precision of ±31 ps-rms over an asynchronous Ethernet fiber-optic link.