Experimental Assessments of Physical Clock Distribution-Enabled Picoseconds Time Synchronization for Optical Switching Networks

The rapid development of artificial intelligence training traffic has fueled significant interest in optical switching network deployment in intelligent computing and data centers with high switching capacity and low power consumption. Considering flexibility and switching efficiency, the time-slotted optical packet switches are broadly deployed for flexible transmission. However, these implements are facing two key challenges in improving bandwidth utilization. Firstly, the time synchronization accuracy directly affects the time-slots alignment, where coarse alignment results in a longer protection gap between optical packets. Such extensions deteriorate the bandwidth utilization. Secondly, the precision of the time synchronization affects time-slot alignment accuracy variation. The alignment uncertainty lengthens the protection gap to guarantee the correct data transmission. To overcome limitations in accuracy and precision inherent in conventional Precise Time Protocol deployments, this paper proposed a precise and stable time synchronization scheme for optical time-slotted switching networks characterized by a physically simplified clock distribution and syntonization network, reusing the existing network connections. With the proposed synchronization method executed, the system achieves a significant accuracy at 1.48E-10 s of root-mean-square. Moreover, the time synchronization process achieves a stable performance with a variation at 3.01 E-12 s over a 10000 s observation window in the long-term examination. Furthermore, experimental results demonstrate the enhanced time-slot alignment performance with a 1.07E-7 s protection gap achieving zero packet loss in a 25 Gbps optical switching network.