The customers always ask what the Exact Compensation and Pre-compensation are and how they compensate the dispersion.
1. Firstly, there are some basic principles for Dispersion compensation.
(a) Distributed compensation, the residual dispersion should be kept in the dispersion tolerance range of
transponders with a certain margin.
(b) Residual dispersion (km) = Transmission distance (km) - DCM (km)
(c) The requirement of the Residual dispersion for different bit rate and coding signal is listed as follow:
2.What are the configuration rules for the Exact compensation?
(a) 100% compensation.
(b) Residual dispersion of each OMS: -10km ~ +10km.
3.What are the configuration rules for the Pre-compensation?
(a) Configure 20km DCM (DCM A) at the transmitting point of OMS to get pre-compensation.
(b) In the downstream spans, configure full dispersion compensation.
(c) At the receiving point of OMS, the residual dispersion should meet the requirement of OTUs.
4. The difference between Exact Compensation and Pre-compensation
(a) Compared with Exact Compensation, Pre-compensation can decrease OSNR requirement by 1~2dB.
(b) Compared with Exact Compensation, Pre-compensation can save the power budget.
Compared with Exact Compensation, Pre-compensation can save the power budget and decrease OSNR requirement by 1~2dB.