Adaptive PrePostCompensation of Cascade Filters in Coherent Optical Transponders We propose an adaptive joint pre and post compensation to correct the filtering effects caused by cascading reconfigurable optical add drop multiplexers (ROADMs). The improvement is achieved without using additional hardware (HW) on the link or within the signal processor in the transponders. Using Monte Carlo simulations, the gradientdescent based method shows an improvement of 0.6 dB and 1.1 dB in the required optical signaltonoise ratio (ROSNR) at the threshold predecoder bit error rate (BER) of 0.02 versus precompensation only in the linear and nonlinear operating region of fiber respectively. We experimentally verified the method with lab measurements in the presence of heavy filtering and optical impairments. We observed a gain up to 0.4 dB compared to typically used precompensation only. Additionally, other tangible system benefits of our method are listed and discussed.

Probabilistic Analysis of Cyclic Packet Transmission Scheduling in WDM Optical Networks We study the packet transmission scheduling problem with tuning delay in wavelengthdivision multiplexed (WDM) optical communication networks with tunable transmitters and fixedtuned receivers. By treating the numbers of packets as random variables, we conduct probabilistic analysis of the averagecase performance ratio for the cyclic packet transmission scheduling algorithm. Our numerical data as well as simulation results demonstrate that the averagecase performance ratio of cyclic schedules is very close to one for reasonable system configurations and probability distributions of the numbers of packets. In particular, when the number of receivers that share a channel andor the granularity of packet transmission are large, the averagecase performance ratio approaches one. Better performance can be achieved by overlapping tuning delays with packet transmission. We derive a bound for the normalized tuning delay xcex94 such that tuning delay can be completely masked with high probability. Our study implies that by using currently available tunable optical transceivers, it is possible to build singlehop WDM networks that efficiently utilize all the wavelengths.