Modeling Ultra-Dense, Ultra-High Speed WDM Fiber Networks
Project Award Date: 01-01-2002
The rapid evolution of WDM terminal equipment presents unprecedented challenges to network planners. This is because the overall performance of these ultra-dense, ultra-high-speed WDM systems may depend very heavily on the distribution of the fiber parameters throughout the link. Because of the small performance margins of these systems, small changes in link parameters (such as amplifier spacings) could lead to catastrophic system performance. Although it is theoretically possible to predict system performance using experimental results, such experiments are costly, time consuming, and prone to error. A more attractive way to predict the system performance of high-speed, dense WDM fiber networks is using numerical modeling. Such models can be used to determine the performance envelopes of networks, since a wide range of network parameters can be changed easily.
The KU/ITTC Lightwave Communication Systems Laboratory has been developing fiber modeling software for a number of years. The majority of this effort has been towards developing a full-wave capability for WDM systems. The first codes were designed for small numbers of wavelengths as a research tool, in order to study various fiber transmission anomaly. Like most other present-generation modeling codes, this code was limited in terms of numbers of wavelengths and bit-rates.
Most recently, a robust version of this code has been developed that is capable of modeling larger systems with greater numerical and user flexibility. This code is capable of modeling WDM networks with hundreds of optical carriers at data rates of upwards of 40 GB/s and can be used on both Windows and Alpha computing platforms. All of the major fiber signal degradation mechanisms are included in this model, including self- and cross-phase modulation, first- and second-order dispersion, loss, Raman scattering, four-wave mixing (FWM), modulation instability, birefringence, and polarization mode dispersion. An alpha version of this code was delivered to Sprint in early 2001.
The goal of this new effort is to expand the functionality and operability of this code, to rigorously test it, and to use it to model dense WDM situations of interest to Sprint TP&I. The functionality and operability of the code will be expanded to allow the greatest possible flexibility in modeling the widest possible range of WDM networks with the least possible operator expertise. We will work closely with Sprint TP&I as they evaluate the alpha version of the code. We will also continue to increase the number and range of the devices and system options available to the modeler.
The code has already undergone extensive testing for numerical accuracy, and this process will continue throughout the next phase of this work. This testing is essential, since the performance margins of dense WDM networks are generally so slim. In addition, an exact knowledge of the performance envelope of this code is needed in order to make it as numerically efficient as possible, which will allow it to model the largest possible WDM networks.
Throughout this effort, we will use the code to model the performance of various network configurations of interest to TP&I. With this in mind, we will enable the code to model the performance of higher-level modulation schemes in a WDM environment. In particular, we will model QPSK modulation for 10Gbps streams and compare this against Prof. Ron Hui's SCM scheme, all in the C band.
Primary Sponsor(s): Sprint