Abstract

The considerable advantages of transparent optical transmission in order to reduce network costs have been discussed intensely. An analysis of deployed WDM networks has shown that 50% to 75% of the investments are concentrated on o/e/o transponders, depending on link rate and node degree.¹ Several approaches to reduce the number of o/e/o converters have been proposed, like the introduction of transparent transmission domains, ² or the application of selective regeneration.³ It is a general problem of optical networks to combine the potential cost reduction due to transparent transmission and the physical requirements of switching and network flexibility. The difficulty is not only given by the fact that long distance (>>600 km) transparent transmission requires a sophisticated physical link-design. Beyond that a flexible optical node should be able to switch a channel from any incoming link to any exit link (Fig. 1) independently of the lengths of the connected links with sufficient and predictable transmission quality of the transported data. Ignoring the problem of wavelength blocking, which is discussed in several papers, the question how to switch channels with different propagation-history (as depicted in Fig. 1) through chains of transparent links is still unsolved. One promising approach to design reliable and stable optical networks is to compose optical links by pre-optimized, standardized sections, the so-called normalized transmission sections.^4,5 The paper illustrates the application of normalized sections in a real field environment and demonstrates flexible switching of 10 Gbit/s-wavelength-channels.

© 2002 Optical Society of America