Date Added: Feb 2010
In WDM optical networks, the Physical Layer Impairments (PLIs) and their significance depend on network type - opaque, translucent, or transparent; the reach - access, metro, or core/long-haul; the number and type of network elements - fiber, wavelengths, amplifiers, switching elements, etc.; and the type of applications - real-time, non-real time, mission-critical, etc. In transparent optical networks, PLIs incurred by non-ideal optical transmission media accumulate along an optical path, and the overall effect determines the feasibility of the lightpaths. If the received signal quality is not within the receiver sensitivity threshold, the receiver may not be able to correctly detect the optical signal and this may result in high bit-error rates.