Optical cross connects for optical networking

As the transmission line rate supported by optical fibers increased from 45 Mb/s to 2.5 Gb/s during the 1980s, interexchange carrier networks introduced various digital cross connects to provision, groom, and restore DS0 (64-kb/s), DS1 (1.5-Mb/s), and DS3 (45-Mb/s) traffic. With the recent release of its WaveStar™ Optical Line System (OLS) 400G, Lucent Technologies has increased the fiber transmission capacity more than one-hundred-fold using dense wavelength division multiplexed (DWDM) 2.5- and 10-Gb/s signals. To meet the challenge of managing the bandwidth within emerging “terabit offices” enabled by DWDM, Lucent and other vendors are aggressively pursuing research and development of optical cross connects capable of directing traffic on a per-wavelength basis. In this paper we explore the role of an optical cross connect (OXC) in evolving wavelength division multiplexed (WDM) optical networks. We also examine various OXC architectures and address the technological challenges and practical tradeoffs that affect their port count (size), functionality, and cost.