Highly practical fiber squeezer polarization controller

The authors developed a fiber squeezer polarization controller satisfying these requirements: (1) stable endless operation, (2) high response speed in the endless operation, and (3) protection from fiber break, a particular problem in a fiber squeezer polarization controller. The developed controller realized a stable endless operation with less than 0.1-dB power penalty under 40°C fiber squeezer temperature change. In addition, a practically sufficient response speed of 15 π rad/s was obtained in an endless operation. A metal-coated fiber used in the fiber squeezers was confirmed to be effective in preventing fiber break by a repetitive load application test (5-10 kg, one million times) to the metal-coated fiber. These techniques could realize a practical and high performance polarization controller for a coherent transmission system