  It is highly desired to operate a joint time and frequency transfer over the
exiting fiber-optic telecom networks with the commercial data transmission.
Previously, we proposed a time transfer scheme based on bidirectional time
division multiplexing transmission over a single fiber with the same wavelength
(BTDM-SFSW), and an optical amplification scheme of single-fiber
bidirectional-transmission unidirectional optical amplifier (SFBT-UOA). The
effects of excess noises like Rayleigh backscattering etc. on the received time
signals can be efficiently suppressed for an accepted timing jitter.
Simultaneously, the bidirectional propagation delay symmetry can be guaranteed
for an expected uncertainty without requiring complicated and expensive link
calibration. In this paper, we propose a high-precision joint BTDM-SFSW based
time and unidirectional frequency transfer over conventional telecom networks.
A stable frequency signal is achieved by compensating the fiber temperature
dependent phase variation according to the time transfer. The proposed joint
transfer scheme is demonstrated over a 320 km fiber-optic telecom testbed with
two 10 Gb/s data transmission channels. The time transfer stabilities (time
deviation, TDEV) of 23.2 ps/s and 5.4 ps/10^5 s, respectively, and the
frequency transfer stabilities (Allan deviation, ADEV) of 5.4X10^(-13)/s and
9.5X10^(-17)/10^5 s, respectively, are reached. The measured bit error rates
(BER) of the 10 Gb/s communication data are well below 10^(-13).
