Salil A. Parikh

A wideband all-optical WDM network

We describe some of the results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks in developing architectures, technology components, and applications for the realization of scaleable, wideband, and transparent optical wavelength-division multiplexing (WDM) networks. Our architecture addresses all-optical transport over the wide, metropolitan, and local areas. It utilizes wavelength partitioning, routing, and active multiwavelength cross-connect switches to achieve a network that is scaleable in the number of users, data rates, and geographic span. The network supports two services which can be point-to-multipoint or multipoint-to-multipoint simplex or duplex connections. The A service is a transparent physically circuit-switched service and the B-service is a scheduled time-slotted circuit which is transparent within its time slots. We have developed a 20-channel local and metropolitan area WDM testbed deployed in the Boston area, now undergoing characterization and experimental applications.

Ultrafast cryptography using optical logic in reconfigurable feedback shift registers

High speed optical communications systems are evolving rapidly. Commercial systems achieve high aggregate data rates utilizing wavelength division multiplexing, where multiple wavelength channels carry information at electronic rates, typically 2.5 Gb/s. Data encryption in these systems will most likely be implemented electronically. However, future system may also utilize time division multiple access (TDMA) schemes and technologies for 100 Gb/s, single stream TDMA networks are currently being developed. These high speed TDMA networks will rely on all-optical switches and processors to interface the high-speed electronics in the users nodes to the ultra-high-speed optical data bus. Data encryption in these networks may need to be implemented using optical logic gates. Straightforward duplication of electronic encryption circuits using optical logic gates is not feasible because optical logic gates have low fan-out, require high optical powers, are difficult to synchronize and have high latency. In this paper, we propose a high- speed electro-optic scheme for reconfigurable feedback shift registers (RFSRs) that relies upon electronic encryption circuits to reconfigure a sequence of optical logic gates and which makes use of the latency in the optical gates as memory. We show that, for linear RFSRs, the low number of optical gates is not a drawback and that the period of the sequences is generally very large. Non-linear feedforward functions, such as all-optical bit swapping, many also be introduced to improve the pseudo-random properties of the sequences.

Transmission modes, cross talk requirements, and performance of the circuit-switched A-service in the all-optical network

In summary, we have demonstrated uniform performance of the all optical network (AON) A-Service under Level-O broadcast and Level-1 routed, multicast and broadcast operation. We have demonstrated multihop operation with conventional wavelength changing. Finally, we presented measurements on the potential impairments of optical beat noise cross talk in transparent optical networks and showed how the AON manages such potential effects.

Control and interfaces for an all-optical network testbed

We describe some of the control and interface techniques employed in the construction of an all-optical network testbed fielded in the Boston metropolitan area. The network was developed by a consortium of AT&T Bell Laboratories, Digital Equipment Corporation, and the Massachusetts Institute of Technology under a grant from ARPA. The network testbed contains local, and metropolitan area nodes that support optical broadcast and routing modes. Electronic access is provided through optical terminals that support multiple services having data rates between 10 Mbps/user and 10 Gbps/user. Applications include video, support for ATM traffic, and telemedicine applications.

Description of all-optical network test bed and applications

We describe an all-optical network testbed deployed in the Boston metropolitan area, and some of the experimental applications running over the network. The network was developed by a consortium of AT&T Bell Laboratories, Digital Equipment Corporation, and Massachusetts Institute of Technology under a grant from ARPA. The network is an optical WDM system organized as a hierarchy consisting of local, metropolitan, and wide area nodes that support optical broadcast and routing modes. Frequencies are shared and reused to enhance network scalability. Electronic access is provided through optical terminals that support multiple services having data rates between 10 Mbps/user and 10 Gbps/user. Novel components used to implement the network include fast-tuning 1.5 micrometers distributed Bragg reflector lasers, passive wavelength routers, and broadband optical frequency converters. An overlay control network implemented at 1.3 micrometers allows reliable out-of-band control and standardized network management of all network nodes. We have created interfaces between the AON and commercially available electronic circuit-switched and packet-switched networks. We will report on network applications that can dynamically allocate optical bandwidth between electronic packet-switches based on the offered load presented by users, without requiring interfaces between users and the AON control system. We will also describe video and telemedicine applications running over the network. We have demonstrated an audio/video codec that is directly interfaced to the optical network, and is capable of transmitting high-rate digitized video signals for broadcast or videoconferencing applications. We have also demonstrated a state-of-the-art radiological workstation that uses the AON to transport 2000 X 2000 X 16 bit images from a remote image server.

Demonstration of multigigabit/per second services over a 20-channel WDM wavelength-routed all-optical metropolitan-area network

An experimental all-optical, wavelength-routed network testbed has been constructed in the Boston metropolitan area. The network has 20 optical channels, space by 50 GHz and provides dedicated circuit-switched wide-band service at user defined modulation formats and rates up to 10 Gbps, and time-slotted WDM services for medium and low-rate users. We are now characterizing the deployed network which spans over 87 km interconnecting four all-optical local-area networks in Littleton, Lexington, and Cambridge Massachusetts. We discuss wavelength sharing and reuse, local broadcast, routing, multi-cast and multi-hop connections at 1.244, 2.488, and 10 Gbps. We present the system design and the performance (e.g. BER and cross-talk) of local-broadcast, metropolitan-area-routed and broadcast transmission modes.