Demand for network bandwidth is growing at unprecedented rates, placing growing demands on switching and transmission technologies. Wavelength division multiplexing will soon make it possible to combine hundreds of gigabit channels on a single fiber. This paper presents an architecture for Burst Switching Systems designed to switch data among WDM links, treating each link as a shared resource rather than just a collection of independent channels. The proposed network architecture separates burst level data and control, allowing major simplifications in the data path in order to facilitate all-optical implementations. To handle short data bursts efficiently, the burst level control mechanisms in burst switching systems must keep track of future resource availability when assigning arriving data bursts to channels or storage locations. The resulting Lookahead Resource Management problems raise new issues and require the invention of completely new types of high speed control mechanisms. This paper introduces these problems and describes approaches to burst level resource management that attempt to strike an appropriate balance between high speed operation and efficiency of resource usage.

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Terabit burst switching

We address the issue of how to provide basic quality of service (QoS) in optical burst-switched WDM networks with limited fiber delay lines (FDLs). Unlike existing buffer-based QoS schemes, the novel offset-time-based QoS scheme we study in this paper does not mandate any buffer for traffic isolation, but nevertheless can take advantage of FDLs to improve the QoS. This makes the proposed QoS scheme suitable for the next generation optical Internet. The offset times required for class isolation when making wavelength and FDL reservations are quantified, and the upper and lower bounds on the burst loss probability are analyzed. Simulations are also conducted to evaluate the QoS performance in terms of burst loss probability and queuing delay. We show that with limited FDLs, the offset-time-based QoS scheme can be very efficient in supporting basic QoS.

QoS performance of optical burst switching in IP-over-WDM networks

Since the first deployments of fiber-optic com- munication systems three decades ago, the capacity carried by a single-mode optical fiber has increased by a staggering 10 000 times. Most of the growth occurred in the first two decades with growth slowing to ten times in the last decade. Over the same three decades, network traffic has increased by a much smaller factor of 100, but with most of the growth occurring in the last few years, when data started dominating network traffic. At the current growth rate, the next factor of 100 in network traffic growth will occur within a decade. The large difference in growth rates between the delivered fiber capacity and the traffic demand is expected to create a capacity shortage within a decade. The first part of the paper recounts the history of traffic and capacity growth and extrapolations for the future. The second part looks into the technological chal- lenges of growing the capacity of single-mode fibers by pre- senting a capacity limit estimate of standard and advanced single-mode optical fibers. The third part presents elementary capacity considerations for transmission over multiple trans- mission modes and how it compares to a single-mode trans- mission. Finally, the last part of the paper discusses fibers supporting multiple spatial modes, including multimode and multicore fibers, and the role of digital processing techniques. Spatial multiplexing in fibers is expected to enable system capacity growth to match traffic growth in the next decades.

https://www.icg.isy.liu.se/courses/optical/Capacity_Trends.pdf

Capacity Trends and Limits of Optical Communication Networks Discussed in this paper are: optical communication network traffic evolution trends, required capacity and challenges to reaching it, and basic limits to capacity.

Since the first deployments of fiber-optic communication systems three decades ago, the capacity carried by a single-mode optical fiber has increased by a staggering 10 000 times. Most of the growth occurred in the first two decades with growth slowing to ten times in the last decade. Over the same three decades, network traffic has increased by a much smaller factor of 100, but with most of the growth occurring in the last few years, when data started dominating network traffic. At the current growth rate, the next factor of 100 in network traffic growth will occur within a decade. The large difference in growth rates between the delivered fiber capacity and the traffic demand is expected to create a capacity shortage within a decade. The first part of the paper recounts the history of traffic and capacity growth and extrapolations for the future. The second part looks into the technological challenges of growing the capacity of single-mode fibers by presenting a capacity limit estimate of standard and advanced single-mode optical fibers. The third part presents elementary capacity considerations for transmission over multiple transmission modes and how it compares to a single-mode transmission. Finally, the last part of the paper discusses fibers supporting multiple spatial modes, including multimode and multicore fibers, and the role of digital processing techniques. Spatial multiplexing in fibers is expected to enable system capacity growth to match traffic growth in the next decades.

Capacity Trends and Limits of Optical Communication Networks

Progress in optical networking has stimulated interest in optical performance monitoring (OPM), particularly regarding signal quality measures such as optical signal-to-noise ratio (SNR), Q-factor, and dispersion. These advanced monitoring methods have the potential to extend fault management and quality-of-service (QoS) monitoring into the optical domain. This paper reviews OPM applications and techniques, while examining the role of OPM as an enabling technology for advances in high-speed and optically switched networks.

Optical performance monitoring

The authors demonstrate a two band architecture for an ultrawideband erbium-doped silica fibre amplifier with a record optical bandwidth of 80 nm. To obtain a low noise figure and high output power, the two bands share a common first gain section and have distinct second gain sections.

80 nm ultra-wideband erbium-doped silica fibre amplifier

Power transients arising from cross-saturation in erbium-doped fibre amplifiers (EDFAs) are generally thought to be slower than 100 /spl mu/s due to the slow gain dynamics. This is a key advantage of EDFAs. The authors report on power transients of 1 dB in <3 /spl mu/s in a chain of five EDFAs. These fast power variations result from the collective behaviour of the amplifier chain.

Fast power transients in WDM optical networks with cascaded EDFAs

A 1-Tb/s aggregate capacity (50 channels each at 20 Gb/s) was transmitted through 55 km of nonzero-dispersion fiber. Fifty channels were generated by polarization multiplexing 25 wavelengths.

1-Tb/s transmission experiment

One Tb/s aggregate capacity (50 channels each at 20 Gb/s) was transmitted through 55 km of non-zero-dispersion fiber. The fifty channels were generated by polarization multiplexing 25 wavelengths.

One Terabit/s Transmission Experiment

Link control, a new technique for protecting surviving channels on a per-link basis from fast power transients resulting from network reconfigurations or line failures, is demonstrated in a 560-km eight-amplifier wavelength division multiplexed link carrying seven 2.5-Gb/s channels plus the link control channel.

C. Wolf

Papers

80 nm ultra-wideband erbium-doped silica fibre amplifier

Fast power transients in WDM optical networks with cascaded EDFAs

1-Tb/s transmission experiment

One Terabit/s Transmission Experiment

Fast-link control protection of surviving channels in multiwavelength optical networks