1.1 Brief Evolution of Optical Networks

While the basic function of a network is quite simple enabling communications between the desired endpoints the underlying properties of a network can greatly affect its value. Network capacity, reliability, cost, scalability, and operational simplicity are some of the key benchmarks on which a network is evaluated. Network designers are often faced with tradeoffs among these factors, and are continually looking for technological advances that have the power to improve networking on a multitude of fronts.

One such watershed development came in the 1980s as the telecommunications industry began migrating much of the physical layer of their inter-city networks to fiber-optic cable. Optical fiber is a lightweight cable that provides low-loss transmission; but clearly its most significant benefit is its tremendous potential networking capacity. Not only did fiber optics open the possibilities of a huge vista for transmission, it also gave rise to optical networks and the field of optical networking.

An optical network is composed of the fiber-optic cables that carry channels of light, combined with the equipment deployed along the fiber to process the light. The capabilities of an optical network are necessarily tied to the physics of light and the technologies for manipulating lightstreams. As such, the evolution of optical networks has been marked with major paradigm shifts as exciting break-through technologies are developed.

One of the earliest technological advances was the ability to carry multiple channels of light on a single fiber-optic cable. Each lightstream, or wavelength ^[1], is...