Advances in integrated photonic circuits for packet-switched interconnection

Abstract

Sustained increases in capacity and connectivity are needed to overcome congestion in a range of broadband communication network nodes. Packet routing and switching in the electronic domain are leading to unsustainable energy-and bandwidth-densities, motivating research into hybrid solutions: optical switching engines are introduced for massive-bandwidth data transport while the electronic domain is clocked at more modest GHz rates to manage routing. Commercially-deployed optical switching engines using MEMS technologies are unwieldy and too slow to reconfigure for future packet-based networking. Optoelectronic packet-compliant switch technologies have been demonstrated as laboratory prototypes, but they have so far mostly used discretely pigtailed components, which are impractical for control plane development and product assembly.Integrated photonics has long held the promise of reduced hardware complexity and may be the critical step towards packet-compliant optical switching engines. Recently a number of laboratories world-wide have prototyped optical switching circuits using monolithic integration technology with up to several hundreds of integrated optical components per chip. Our own work has focused on multi-input to multi-output switching matrices. Recently we have demonstrated 8×8×8λ space and wavelength selective switches using gated cyclic routers and 16×16 broadband switching chips using monolithic multi-stage networks. We now operate these advanced circuits with custom control planes implemented with FPGAs to explore real time packet routing in multi-wavelength, multi-port test-beds. We review our contributions in the context of state of the art photonic integrated circuit technology and packet optical switching hardware demonstrations. INTEGRATED PHOTONIC PACKET SWITCHESPhotonics switching technologies can be broadly classed in terms of wavelength operations. Photonic space switches route massive bandwidth signals independently of signal wavelength and number of multiplexed wavelength channels. Wavelength selective switches operate on multiplexed data streams to re-route fine granularity streams at the wavelength scale. The third class of photonic switch technologies enables the changing of carrier wavelengths at the photonic layer, offering considerable system level flexibility. Photonic and wavelength selective switches are already deployed in telecommunications networks, offering network flexibility advantage within tight cost and energy constraints [1][2][3][4]. Performing these functions at the photonic layer avoids the high energy costs and delays associated with opto-electronic conversions and electronic de/serialisations. The highest connectivity circuits have been based on low loss and high connectivity 3-D MEMS switching engines, but these are inherently free-space systems and require complex, precision assembly. Connectivity can already extend to many hundreds and thousands of connections, but there are concerns about the scaling properties in term of equipment cost, modularity and size....

Towards Large-Scale Fast Reprogrammable SOA-Based Photonic Integrated Switch Circuits

“…This scenario, however, is not sustainable through packet routing and switching in the electronic domain only. Hybrid solutions have been proposed for decades now [4]: photonic hardware is introduced for massive-bandwidth data transport and switching, while routing is handled at more modest GHz rates in the electronic domain.…”