Polarization-mode dispersion of a circulating loop

We derive an analytic expression for the evolution of the differential group delay (DGD) in a fiber-optic circulating loop. We distill a simple analytic solution for the average DGD and show that it accumulates approximately linearly with transmission distance. The scaling of this linear function is confirmed experimentally using a long-haul fiber-optic transmission test-bed. This result is contrasted with DGD accumulation in a long straight-line transmission system, where the average DGD accumulates as a square root of the system's length. (C) 2004 Optical Society of America.