Multiple-Node Time Transfer Over Star Fiber Network Without Requiring Link Calibration

In this letter, we proposed a point-to-multipoint fiber-optic time transfer scheme over a star-shaped fiber network based on bidirectional frequency division multiplexing without requiring link calibration. The time signals at the local station and remote stations are encoded into time-varying signals within in different spectral passbands, respectively. The optical carriers with the same wavelength are employed to transfer the two time-varying signals in both directions over a single fiber. The backscattering noises from fiber links can be effectively suppressed by simply electrical filtering due to the non-overlapping on spectrum between the forward and backward time-varying signals. The local station broadcasts the time signal of the reference clock to all remote stations based on space division multiplexing to support point-to-multipoint fiber-optic time transfer. The proposed scheme is demonstrated over a star-shaped fiber network with two remote stations. The results show that the measured mean clock difference can be less than -1.03 ps and 4.99 ps without link calibration, respectively. The measured time stability in terms of time deviation is better than 19.93 ps@1s, 0.50 ps@1000s and 25.35 ps@1s, 0.65 ps@1000s.