A Parallel Algorithm for Numerical Simulations of WDM Optical Fiber Communication Systems Thiab R. Taha Computer Science Department University of Georgia Athens, GA,USA ABSTRACT Optical fiber communication systems have experienced tremendous growth in the last twenty years. In the past year alone researchers have announced transmission rates in excess of one tera bit per second. At the same time, the growing use of the Internet and the World Wide Web has quickly contributed to make this area one of the key technological sectors in the global economy, and has generated an unprecedented demand for even higher transmission capacities in order to offer a good Quality of Service (QoS).

A Parallel Algorithm for Numerical Simulation of WDM Optical Fiber Communication Systems Thiab R. Taha Computer Science Department University of Georgia Athens, GA,USA ABSTRACT Optical fiber communication systems have experienced tremendous growth in the last twenty years. The recent growth is mainly due to the introduction of wavelength division multiplexing(WDM) and dispersion management(DM) technology. WDM allows the simultaneous transmission of multiple optical channels, operating at their own frequencies, through the same optical

In WDM systems, different channel pulses propagate at different velocities and, as a result, collide with each other. This leads to signal deteriorations. Another problem for WDM systems is the presence of resonant four wave mixing (FWM) terms due to the interaction between the different channels. This serious problem is partially solved by the introduction of dispersion management(DM) in optical systems.

In this talk, we introduce a parallel numerical algorithm based on the spilt step method and the FFT to study the interactions of WDM dispersion-managed solitons. Also, other related issues including the polarization effects on soliton systems will be addressed. The implementation of the algorithm will be carried out on the SGI origin 2000 parallel system.

With the current technology, fiber capacity can be as high as 40 Gbps on a bit stream. As many as 80 bit streams using WDM can accommodated on a single glass fiber. Suppose a fiber optic has 24 strands where we allow 4 spares and 10 in each direction. The total cable capacity is 40x10x80 = 32,000 Gbps.

The growing use of the Internet and the World Wide Web has quickly contributed to make this area one of the key technological sectors in the global economy, and has generated an unprecedented demand for even higher transmission capacities in order to offer a good Quality of Service (QoS).

The new services that are emerging in the market are mainly: Video on Demand, High Speed Internet, Videoconferencing, Telemedicine, Gaming, Telelearning, …

Optical Fiber has many advantages over conventional techniques such as: 1. low loss and attenuation. 2. high bandwidth 3. Its immunity to the electromagnetic interferences. 4. Thin and lightweight, so it is easy to operate. 5. They are more secure against wiretapping. 6. Can extend over longer distances before a repeater is needed. 7. They are more immune to crosstalk within a cable than other ordinary wires.

Problems with the use of WDM: 1. Due to the periodic distribution of amplifiers, a resonant instability created by the nonlinear terms (four-wave mixing (FWM) interactions) can seriously degrade the signal. The proper use of Dispersion management(DM) can alleviate the negative effects of FWM. 2. The frequency shifts and the associated displacement in pulse arrival times created by the interaction of the solitons with amplifier noise. This can be reduced by the introduction of guiding filters.

An optical transmission system consists of three components: 1. the optical transmitter 2. the transmission medium 3. the optical receiver The transmitter uses a pulse of light to indicate the ‘1’ bit and the absence of light to represents the ‘0’ bit. The receiver can generate an electrical pulse once light is detected.

Two types of fiber: 1. A single mode fiber: this requires the light to propagate in a straight line along the center of the fiber. It is used for long distance transmission. It has a good quality signal. 2. A multimode fiber: a light ray might enter the fiber at a particular angle and go through the fiber through internal reflections.

Because of the capacity growth, optical fiber systems are increasingly being limited by the following transmission effects : Chromatic dispersion, Nonlinearity, Polarization effects, Amplifier noise and others. In order to design a transmission system, it is crucial to accurately model and calculate the impairments due to these effect.

One approach for studying the various physical effects is to model transmission systems numerically. Full numerical modeling of real systems is still beyond the capability of current computational resources in most cases. As a consequence, there is a critical need for developing parallel numerical techniques to model these systems. In this talk I will discuss some of these techniques.

High Performance Computers 1. In early1980’s computers perform 10 6 Floating point operations per second(Mflop/s) Scalar based systems 2. In 1990’s computers perform 10 9 Floating point operations per second(Gflop/s) Vector and shared memory computers 3. Today computers perform Floating point operations per second (Tflop/s) Highly Parallel Computers, distributed processing, message passing

4. In 2010 we expect computers to perform Floating point operations per second(Pflop/s) Shared/distributed memory processors, many more levels of memory hierarchy, more adaptive techniques, extended precision.

Top 500 Most powerful Computers in the world This list is available from

The National Science Foundation selects Compaq Computer Corporation and the Pittsburg Supercomputer Center to build and manage the world largest supercomputer for scientific applications. The first delivery of this system is expected by November This supercomputer is expected to deliver 5 Teraflops of peak performance.

Also, the French Atomic Energy Commission is building the largest supercomputer in Europe to simulate nuclear testing. On March 7 th., 2003 Scientists at Stanford University used fiber-Optic cables to transfer 6.7 Gigabytes of data- the equivalent of 2 DVD movies- across 6,800 miles in less than a minute. The data was sent from California to Amsterdam.