Time transfer through the optical supervisory channel in wavelength division multiplexing systems.

We present an optical fiber time transfer scheme through the optical supervisory channel (OSC) in wavelength division multiplexing (WDM) systems. A sub-band of the standard OSC band is used to transmit time signals by only adding sub-OSC filters in commercial WDM systems. The transmission of the existing communication data service is not affected. The wavelengths of bidirectional time transmission in the same sub-band can be very close, or even the same, to maximize the bidirectional propagation symmetry and improve the precision of time transfer. Combined time, optical supervisory signal, and communication data transmission is experimentally demonstrated along a single 100 km optical fiber in a WDM system in laboratory.