Stable radio frequency dissemination by simple hybrid frequency modulation scheme

Fiber-Optic UTC(k) Timescale Distribution With Automated Link Delay Cancelation

In this paper, we describe the idea and practical realization of an automated calibrator of fiber-optic UTC(k) distribution system, along with a high-resolution shifter of 1 PPS signal, which allows us to cancel the propagation delay and, thus, to produce the 1 PPS at the remote system output with practically zero offset. The solution was experimentally verified with 10 different optical paths, up to 300 km long. The rms offset of the output timescale in our experiments was 7.1 ps, and maximum absolute value did not exceed 15 ps.

Stable frequency dissemination over multi-access fiber loop link with optical comb

An optical comb based stable frequency dissemination system is proposed and experimentally demonstrated over a multi-access optical fiber loop link. In the system, a new technique based on optical-microwave phase locking loop is designed for phase compensation. In the experiment, a mode-locked fiber laser at a repetition rate of 100 MHz is used to provide an optical source at local site, then it transmits along a 150 km fiber loop link. To testify the proposed system, two accessing nodes are measured in the loop link. The dissemination frequency instability is measured at 3.65 × 10^-15/1 s and 7.8 × 10^-18/1000 s at the intermediate node. The similar performance is shown at the other node. Hence, the system has the potential application in high-precision frequency transmission system via a long-haul multi-access loop link.

Fiber-optic radio frequency transfer based on active phase noise compensation using a carrier suppressed double-sideband signal

In this Letter, we propose a fiber-optic radio frequency (RF) transfer based on active phase noise compensation adopting a carrier suppressed double-sideband (CSDSB) signal. The forward CSDSB signal is generated based on the transmitted RF signal at the local site to discriminate from the backward RF signal. The forward and backward signals are transmitted over the same fiber with the same wavelength to guarantee the bidirectional propagation symmetry. The impact of backscattering is efficiently suppressed by electrical filtering at the sites. A 1 GHz signal transfer over a 40 km optical link is performed in a laboratory. The results show that the proposed scheme can improve the short-term stability from 1.9  e-13/s to 3.9  e-14/s in contrast to the scheme with backscattering while reaching a long-term stability of 2.0  e-16/10000 s.

GVD-insensitive stable radio frequency phase dissemination for arbitrary-access loop link

We propose and experimentally demonstrate a stable radio frequency (RF) phase dissemination scheme for a long-haul optical fiber loop link based on frequency mixing. Using a single optical source in both directions of the loop link, additional timing jitter caused by group velocity dispersion (GVD) can be eliminated. Impressive scalability provided by the optical link ensures that arbitrary-access node can obtain an RF signal with a stabilized phase to meet the requirements of multiple users. In our experiment, a 2.4 GHz RF signal is distributed to arbitrary points along a 100 km fiber-optic loop link steadily. Stabilities of the recovered signals from two accessing nodes are recorded. The root-mean-square (RMS) phase jitter of the received signal at either accessing node is reduced from 1.87 rad to no more than 0.027 rad during 1800-second measuring time.

Fiber-optic radio frequency transfer based on passive phase noise compensation with frequency dividing and filtering

In this Letter, a passive phase noise compensation-based fiber-optic frequency transfer scheme with frequency dividing and filtering is proposed. The probe signal is divided at the remote site and effectively discriminated from the backscattering noises by electrical bandpass filtering at the local site. By combining the bidirectional transmission with the same wavelength on a single fiber, the scheme can reach the maximum bidirectional propagation symmetry and effectively suppress the effect of backscattering at the same time. The proposed scheme is experimentally demonstrated and compared with the scheme with backscattering. The relative frequency stabilities of 3.9×10(-14)/s and 1.2×10(-16)/10(4) s are reached for 40 km transfer, which obviously outperform the scheme with backscattering, especially in terms of short-term stability, and are closed to the floor of the back-to-back experimental system.

WDM-based radio frequency dissemination in a tree-topology fiber optic network

In this paper, we propose and demonstrate a scheme to achieve point-to-multipoint dissemination of radio frequency (RF) signals in a local area fiber optic network with tree topology based on wavelength-division multiplexing (WDM) technique. The phase changes caused by the fluctuations of the transfer links are passively canceled at remote end instead of at local end, which makes it feasible to flexibly build a tree-topology local area dissemination network with great cost-effectiveness. For the first time, we study the limit of long-term performance which is caused by temperature-induced variation of group velocity dispersion (TIVGVD) in dissemination networks using WDM techniques. In the proof-of-concept experiments, 38.5 km and 50 km fiber links are established to disseminate a 1 GHz frequency signal with fractional instability of 10(-17) order after 10(4) s averaging time. Then 17.4 nm wavelength spacing is introduced between local carrier and user carrier to verify the theoretical analysis. Under a controlled fiber temperature variation of about 21 °C, the obtained overlapping Allan deviation (ADEV) agrees well with the simulation results after 10(4) s time scales, which proves the validity of our theory. The theory has practical values in predicting and optimizing the capacity and performance of a WDM-based local area RF dissemination network.