Optical Amplification for BTDM-SFSW-Based Time Transfer

Optical amplification, which is necessary for extending the distance of fiber-optic time transfer, has significant impacts on the time transfer performance. In this paper, we investigate and optimize the optical amplification for the time transfer based on bidirectional time division multiplexing transmission over a single fiber with the same wavelength (BTDM-SFSW). Three optical amplification schemes, namely single fiber bidirectional amplifier (SFBA), single fiber bidirectional amplifier with magneto-optical switch (SFBA-MOS), and single-fiber bidirectional-transmission unidirectional optical amplifier (SFBT-UOA) are considered. For each optical amplification scheme over different fiber links, the timing jitter and uncertainty of time transfer are theoretically and experimentally analyzed. A simple timing jitter optimization method for the BTDM-SFSW links is proposed. Further evaluations are performed from the point of view of system complexity, operation cost, and compatibility with telecom optical networks. Results show that SFBA is more suitable over shorter fiber links for its lower complexity and cost, while SFBA-MOS or SFBT-UOA should be employed for longer fiber links to achieve the accepted time transfer performance.