Optical packet switching lowers next gen IP network costs

As the Internet transitions from a best-effort network to a strategic global IP infrastructure, demands will not only be for higher bandwidth, but also for a wider range of integrated services demanding mission-critical reliability. Service providers will face a "crisis of cost" driven by the complexity and inefficiency of operating multiple, parallel networks.

Service providers are now evolving their complex networks toward a simpler architecture, based on a single, highly available intelligent packet layer residing on an optical transport layer. At the center of this new architecture is the core Internet Protocol/Multi-Protocol Label Switching (IP/MPLS) Routing Platform.

Optical switching has long been proposed as a faster, less expensive, and more efficient alternative to electronic switching. However, it is impractical to evolve the current Internet to one based on optical circuit switches because the Internet requires per packet switching.

Although current routers offer significant advancements over previous generations, they still cannot scale sufficiently to meet projected traffic demands, nor do they provide the very high level of availability required to run mission-critical traffic over IP networks. In addition, electrical switch fabrics have posed physical limitations that prevent routers from scaling sufficiently to avoid premature forklift upgrades.

All of this points to the need for a new kind of scalable router architecture that routes IP/MPLS packets electronically, but switches them optically. This combination of large port count with high speed switching (nanoseconds) is needed realize this next generation IP routing platform. However, all previous optical switching technologies were either large and slow (milliseconds) or small or fast (nanoseconds).

New enabling technologies are required to achieve such a router requires a new approach to optical switches.

Chiaro's optical phased array (OPA) technology is a large, fast optical switch optimized for the next generation high-capacity IP/MPLS routing platforms reducing cost and enabling the networks for business critical services.

The ideal optical switching technology for enabling scalable IP/MPLS routing platforms should deliver high speed (nanosecond switching), hundreds of 10 Gbit/second ports (40 Gbit/sec in the future), scalability from tens to hundreds of ports, and bandwidth independence to support higher date rates per port (further in the future)

In contrast to optical technologies previously proposed for switching — which have been either large and slow (microseconds to milliseconds), as in micro-electro-mechanical systems (MEMS) and acousto-optic devices, or small and fast (e.g., thermo-optics, holographic, and tunable lasers), Chiaro's OPA technology is both large and fast. It has been deployed, as part of the California Institute for Telecommunications and Information Technology's "OptIPuter" Grid Computing Initiative at the University of California at San Diego (UCSD).

The OptIPuter next-generation optical networking Grid represents an entirely new architecture. Traditionally, computer processors have been the fastest part of a supercomputer, while memory and disk storage were bottlenecks. In the OptIPuter, the communications links are the fastest part of the computer and the processors are slower "peripherals." In the OptIPuter installation, the OPA is a scalable, bandwidth-independent, 64 x 64 port module, switching optically in nanoseconds.

How OPA works

In OPA, the switching of light paths takes place through an innovative use of the fundamental optical principle of constructive and destructive interference, controlled through the use of GaAs waveguides. In interference, when coherent light illuminates two narrow slits, the light exiting the slits adds in-phase at some angles and out-of-phase at other angles, thus producing light and dark bands on a surface illuminated by the slits. The light and dark patterns can be varied by increasing the number of slits; as more slits are illuminated, it is possible to produce only one bright light band on the output surface.

In the OPA switch, each input fiber illuminates 128 parallel optical paths, or waveguides. The number of waveguides determines two parameters: the size and resolution of the output spot (more waveguides means smaller and more tightly resolved spots) and the brightness of the undesired partially illuminated bands (more waveguides reduces the stray brightness).

Each group of 128 waveguides is called a beam deflector, and each beam deflector is illuminated by a single optical fiber. OPA technology uses the electro-optic effect of GaAs to "tilt" the light beam and switch from one fiber to another. Chiaro's engineers chose GaAs because the optical properties of the material can be changed using an externally applied electrical field, which controls the material's index of refraction so that the light passing through it is retarded when an electric field is applied. As a result, the light coming out of the beam deflector can be deflected to any desired location.

By harnessing the principles of constructive and destructive interference, the OPA switch achieves both high speed and large port counts. Specifically, the physical delay in establishing the interference patterns is essentially the speed of light. Large port counts are determined by the spatial resolution of the array of 128 waveguides.

OPA technology offers a number of design advantages, including:

• -Reliability: all solid state, no moving parts, the only active device is a reversed-based diode

• -Manufacturability: very few active alignment steps, use of semiconductor manufacturing methods

• -Scalability: provided by the rate and format independence of the optical fabric

• -Low power: optical switch fabrics consume far less power than equally sized electrical switch fabrics

• -Reduced space and weight: optical switch fabrics consume less space than equally sized electrical switch fabrics, an important consideration for carriers trying to optimize limited rack space

• -Reduced and consistent latency: there is no optical-to-electrical conversion

• -Flexibility: multiple control planes can be developed for the switch to allow new network architectures to be deployed over a common core

A large, centralized IP/MPLS Routing Platform based on electronic routing with optical switching will offer a number of important benefits for Internet service providers including a paradigm shift in scalability, significantly reduced costs, increased capital preservation with 10+ year product lifecycles.