MONTEREY, CA–The market focus in optical networking has shifted from capacity expansion to cost-effective network management, according to Mark Krol of Corning Inc. (Corning, NY). And about 40% of the cost of optical networking lies in unnecessary optical-to-electrical-to-optical (OEO) conversions.
Krol and other speakers at a joint symposium on optical crossconnects held last month in Monterey, CA, by the Optical Society of America (OSA) generally agreed that the solution to this problem, based on current technology, lies in separating network traffic into an OEO-free transport layer and an OEO-dependent service layer. Although speakers differed on the means, the various solutions tended to follow the lines of the component technologies chosen by various equipment vendors.
At a typical optical-network node in the USA, about 80% of the traffic can be routed with transparent optical switches. The substantial cost of optical transducer components can be limited to the remaining 20% of signal traffic that requires some sort of opaque provisioning, packet switching or signal processing, according to John Bowers, chief technical officer at Calient Networks (Santa Barbara, CA). “hotonic switches save cost by eliminating many transponders,” he said.
Presenters from Calient and Lucent (Holmdel, NJ) discussed microelectromechanical-systems (MEMS) technology for three-dimensional (3-D) switch fabrics in which optical signals are routed in free space between a 2-D array of input ports and a 2-D array of output ports by mirrors with two degrees of rotational freedom. Primary advantages of 3-D MEMS over 2-D switch fabrics are the ability to scale up in port count with capacity expansion, relatively low path-dependent loss, and the availability of semiconductor methods for high-volume manufacturing, Bowers said in describing the commercially available Calient product based on bulk electrostatic MEMS. To have a large number of ports in a single stage, a switch fabric must use 3-D MEMS, he said, which also provides a highly parallel architecture in the high port-count environment to compensate for the speed advantages of 2-D switch fabrics.
While 3-D MEMS switch-fabric enables high-port-count applications, Krol emphasized that a broad range of switch fabric technologies will be needed in any comprehensive solution. The range of design considerations for optical-crossconnect modules includes fiber management, collimators, mirror arrays, servo controls, and packaging. Krol described development efforts at Corning in several areas, focusing primarily on a wavelength-selective crossconnect that is optically transparent only at a designated wavelength, but that can be cascaded to build broadband switching modules.
Johnathan Lacey of Agilent Technologies (Santa Clara, CA) emphasized current market demand and the need for multiple-technology solutions even more strongly in his talk. He argued that overwhelming market demand is primarily for 2-D switch fabrics. Due to factors such as a lack of cross-vendor interfacing standards, the need for electronic signal regeneration, monitoring and wavelength conversion, as well as improving electronics, Lacey projected a future optical-network architecture in which “slands of transparency” are likely to be interconnected by opaque OEO nodes. Agilent�s 2-D modular technology for optical switching is based on a combination of silicon planar waveguides and inkjet-printer technology.
In a panel discussion after the main presentations, Daniel Blumenthal from the University of California-Santa Barbara, on behalf of Calient, said that generalized mulitprotocol label switching allows crosscommunication between all-optical crossconnect products from different vendors. Lacey also mentioned that the Agilent switching fabric is being developed and demonstrated in cooperation with Alcatel and other vendors. Representatives of Ciena and Tellium in the audience said that their companies are working with the Corning switch fabric.
Hassaun Jones-Bey, senior editor, Laser Focus World
Source: Optoelectronics Report, 7/1/01