Cost Considerations in 40G Networks

Off late, optical backbones and metro core networks are predominantly 10G, on the verge of moving to 40G. But the challenges in the previous move from 2.5G to 10G are minor compared to those of moving from 10G to 40G, and the challenges moving on to 100G are even more daunting. Increasing the line rate 4x (by moving from 10G to 40G) or 10x (10G to 100G) causes nasty problems - impairments - due to the physical properties of light passing through glass fiber. These changes create a higher baud rate (symbol rate), which has effects, including reducing light signal strength, shortening reach, increasing sensitivities to Chromatic Dispersion (CD) and Polarization Mode Dispersions (PMD).