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The low-frequency optical-signal phase noise induced by mechanical vibration of the base occurs in field-deployed fibers. Typical telecommunication data transfer is insensitive to this type of noise but the phenomenon may influence links dedicated to precise Time and Frequency (T&F) fiber-optic transfer that exploit the idea of stabilization of phase or propagation delay of the link. To measure effectiveness of suppression of acoustic noise in such a link, a dedicated measurement setup is necessary. The setup should enable to introduce a low-frequency phase corruption to the optical signal in a controllable way. In the paper, a concept of a setup in which the mechanically induced acoustic-band optical signal phase corruption is described and its own features and measured parameters are presented. Next, the experimental measurement results of the T&F transfer TFTS-2 system’s immunity as a function of the fibre-optic length vs. the acoustic-band noise are presented. Then, the dependency of the system immunity on the location of a noise source along the link is also pointed out.

In this paper, we present the experimental result for the fiber optic frequency transfer link with optical regenerators exploiting the same Er-doped fiber for amplifying the signals in both directions. The measurements performed at the distance of 124 km with one amplifier and 224 km with three amplifiers showed that the presented solution is adequate for transferring the frequency signals generated by cesium clocks, hydrogen masers, and cesium fountain clocks. The Allan deviation around 9 \cdot 10^-18 and 5.5 \cdot 10^-17 was found for the averaging time of 10^5\ \s for 124- and 224-km-long links, respectively. [ABSTRACT FROM PUBLISHER]

In this paper, we present the novel method of stabilizing the propagation delay in the fiber-optic link using two matched electronic delay lines. For this purpose, we developed a dedicated integrated circuit using Austria Mikro Systeme 0.35-\mu\m CMOS process. Two transmission links were tested at two independent laboratories, operating at different distances (20 and 60 km, respectively) and using slightly different setups. Both links show the Allan deviation of about 2 \times 10^-17 after 1-d averaging and residual fluctuations of the propagation delay of around 12 ps peak to peak. The obtained results show that such systems are suitable for distributing the signals from hydrogen masers or cesium clocks at the distances spanning tens of kilometers. [ABSTRACT FROM PUBLISHER]

Filtering of the chirped signal from a directly modulated laser with the narrowband optical filter with a high roll-off allows to in-crease the dispersion tolerance of the transmitter substantially. In the paper, the influence of the parameters of the filter on the performance of the fibre link is analysed. Investigations are carried out for both band-pass and band-stop filters. Basing on the numerical modelling of the fibre link, the parameters of the filter are searched that give the smallest dispersion penalty. Theoretical investigations are supported by hardware experiments confirming correctness of applied methods and models. [ABSTRACT FROM AUTHOR]

In the paper we present a solution for controlling the chain of bidirectional optical amplifiers, intended for long-haul fiber links used to distribute signals produced by optical atomic clocks. The solution is based on a dedicated two-channel noise detector, which allows independent measurement of the noise contributions related to interferometric signal fading and additive wideband noise. New signal quality metrics, based on two-dimensional noise detector, allows to distribute properly the needed gain among the chained amplifiers. Experimental results performed both in laboratory conditions and on a real 600 km-long link, confirming proper operation of proposed solutions, are presented.

In this paper, we present the concept of accessing the signal at some midpoint of a frequency dissemination system with stabilized propagation delay, which allows building the point-to-multipoint frequency dissemination network. In the first experiments with a 160 km-long fiber link composed of a field-deployed optical cable and fibers spooled in the lab, exposed to both diurnal and seasonal temperature variations, in the access node, we obtained the Allan deviation of a 10- MHz frequency signal of about 3 × 10(-17) and the time deviation not greater than 2 ps for 10(5) s averaging.