Generalized Probability Density Function of Polarization-Dependent Loss in Optical Links

In modern optical networks, reconfigurable optical add-drop multiplexers consisting of wavelength selective switches are widely adopted, and they are the major cause of polarization dependent loss (PDL). Link PDL evolves with time due to the time-varying polarization state of propagating light in the optical fiber, and this randomness needs to be considered in the design and operation of optical networks. Therefore, characterizing link PDL using statistical methods is important. It is well known that link PDL in ultra long-haul systems containing a large number of PDL elements is Maxwellian-distributed. However, it is not appropriate when links include a reduced number of PDL elements, or there exist a few dominant PDL elements. In this letter, statistics of link PDL is studied, and a generalized probability density function (PDF) is derived for links including a variety of number of elements. Simulations and experiments are performed, and results show that the generalized PDF fits in a wide scope of realistic scenarios. On the other hand, the conventional Maxwellian distribution exhibits significant discrepancy with the actual one in the studied cases.