Will it be easy for the telecom carriers to deploy
40Gb/s transmission systems?

Pavel Mamyshev
Mintera Corporation

The capacity of fiber-optic communication systems has been growing tremendously over the past years. In this process, the telecommunication carriers have gone through major changes in the network design such as the introduction of in-line optical amplifiers and the transition from single-wavelength transmission to multi-wavelength transmission (also called wavelength division multiplexing, WDM). At the same time, the per-channel electrical time-division multiplexing (ETDM) data rate of commercially deployed transmission systems has been increasing approximately by a factor of four every five years. During the last transition of ETDM rates from 2.5Gb/s to 10Gb/s, the service providers furthermore had to adopt another new concept in their optical networks: in-line dispersion compensation. This required placement of bulky spools of dispersion compensating fiber (DCF) at each in-line amplifier site and major modifications of the design of in-line amplifiers to accommodate the loss of the DCF. Even though these changes required forklift upgrades of installed systems and a new approach to the network planning, the result was better and -very important! - less expensive networks.

For example, increasing ETDM rates by a factor of four historically reduced the equipment cost for the transmission of a unit bandwidth by a factor of two (in addition to the savings in operation cost such as network management and power consumption). Extrapolating the historical evolution of ETDM rates of commercially deployed systems, and taking into account that 10Gb/s systems started to be deployed in 1995-1996, one can expect to see deployment of 40Gb/s systems in 2002-2003. In this paper, we will
discuss the following question: what will it take for the carriers to introduce the 40Gb/s technology in their fiber-optic networks? Does this transition require major changes in the networks, similar to the previous technological changes? This question is especially important in the current economic situation where service providers are cutting their capital expenses since major changes require major capital spending. As it will be shown in the paper, from the carrier’s perspective, the transition to 40Gb/s systems is expected to be painless and trivial in comparison with the previous technological changes.

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