Raising dispersion tolerance to increase distance

摘要

When service providers upgrade their metro networks to 10-Gbit/sec transmission speeds, they must overcome the chromatic dispersion (CD) limitations of SONET/SDH single-channel and DWDM systems. Once these limits are reached, optical signals must be regenerated, increasing network equipment expenditures for service providers at a time when cost reductions are a necessity. Several techniques are being developed to extend dispersion limits and eliminate as much expensive regeneration equipment as possible. One approach uses transmit side signal processing to achieve spectral shaping of the optical transmission to make it more tolerant of dispersion. As the signal propagates through fiber, dispersion typically distorts the signal. When the signal reaches beyond a certain distance―typically 80 km for 10-Gbit/sec transmission speeds―the signal becomes so distorted that the receiver has trouble differentiating between the 0s and 1s. At that point, errors result as the equipment tries to determine what was sent.