Fiber-optic time-frequency transfer in gigabit ethernet networks over urban fiber links.

We demonstrate a new optical pulse amplitude modulation (PAM) scheme where joint ultrastable time-frequency and gigabit ethernet data transfer with the same laser wavelength is realized. Time transmission is compatible with the White Rabbit (WR) based on gigabit ethernet networks, and frequency transmission is achieved by using 100MHz radio frequency (RF) modulation and the round-trip compensation methods. The laser is on-off keying (OOK) modulated by the WR signal, the RF and WR signal are modulated by optical PAM in a Mach-Zehnder interferometer modulator (MZM), and the local and remote site are connected by 96km urban fiber in Shanghai. The experimental results demonstrate that the frequency instabilities are 5.7E-14/1 s and 5.9E-17/10s, and the time interval transfer of 1 pulse per second (PPS) signal with less than 300fs stability after 10 s are obtained. This novel scheme can transmit frequency signals at hydrogen-maser-level stability in the gigabit ethernet network.