An investigation of the OSNR penalty for overcoming the impairments of distributed PDL*

Using SVD, we derived OSNR penalty is weakly correlated with PDL distribution. The relationship between OSNR penalty and average PDL value is quadratic function for the both polarization tributaries and linear function for the worst.

I. Introduction

Polarization Dependent Loss (PDL) is considered to have a strong impact on the performance of next-generation optical fiber transmission systems. The PDL of the elements in fiber link such as optical amplifiers and reconfigurable optical add-drop multiplexers induces polarization dependent optical power gain and attenuation, with the result of an inequality of received signal powers between two orthogonal polarization tributaries and imbalance of optical signal-to-noise ratio (OSNR) [1, 2]. Up to now, the practical and economical solution for a commercial system to overcome PDL impairments is by the addition of SNR margin, or equivalent OSNR penalty. However, underestimation of OSNR penalty results in an excessive outage probability, while overestimation leads to extra-power consumption. Therefore, it is most important for us to estimate an exact OSNR penalty for a distributed PDL fiber link although it is a troublesome and difficult issue.