Testing Time and Frequency Fiber-Optic Link Transfer by Hardware Emulation of Acoustic-Band Optical Noise

Abstract

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.

Metrology and Measurement Systems

“…The core problem of optical time-frequency transfer over fibre is the compensation of phase noise. At present, the research teams in France [11,12], Germany [13], Poland [14,15], China [16][17][18][19][20] and other countries [21][22][23][24] have adopted the active phase noise compensation method to achieve high-precision optical frequency transfer over fibre.…”

Metrology and Measurement Systems

“…Fibre optic transfer of time and frequency (T&F) signals is nowadays considered as a technique offering the highest potential concerning accuracy and stability [1][2][3][4]. This is because the bi-directional transmission in a single fibre, thanks to the inherent symmetry of propagation conditions in opposite directions, enables efficient elimination of noise generated in the fibre due to temperature fluctuations and mechanical vibration [5][6]. When it has become apparent that satellite signals might be easily jammed or spoofed, the fibre optic distribution is also acknowledged to be a real alternative to ubiquitous satellite transfer techniques [7].…”