New phase stable optical fibre

Linden Photonics offers a standard single mode fiber with a special liquid crystal polymer (LCP) coating. This material has a negative coefficient of thermal expansion, which significantly reduces the change of signal delay due to temperature change. Other than with normal fiber cables, the thermal coefficient of delay (TCD) is not in the range from 40 to 130 ps/km/K, but below 7 ps/km/K. Thus it is nearly as good as the phase stabilized optical fiber (PSOF) by Furukawa (specification < 5 ps/km/K). The TCD of Linden Photonic cables have been measured at DESY. In order to make this comparable, the PSOF by Furukawa and furthermore three standard optical fiber cables were measured, too. As a result, a complete picture of the TCDs of different fibers will be presented. This information is very useful in order to design optical synchronization systems in general. It is planned to use Linden Photonics cables for the long links (fiber lengths in a range from 0.4 to 3.5 km) of the laser based synchronization system at XFEL.