The present invention relates to an optical fiber transmission line having a structure offering superior connection loss characteristics at the fusion-spliced position between optical fibers. This optical fiber transmission line has at least first and second optical fibers that are fusion-spliced. Each of these first and second optical fibers has a core region doped with 10 mol % or more of Ge and has a mode field diameter with a minimum value of 7 μm or less at the wavelength of 1550 nm. The difference between the minimum mode diameter of the first optical fiber and that of the second optical fiber is 1 μm or less.

Optical fiber transmission line

We report here a scalable, multichassis, 6.3 terabit core router, which utilizes our proprietary optical switch. The router is commercially available and deployed in several customer sites. Our solution combines optical switching with electronic routing. An internal optical packet switching network interconnects the router’s electronic line cards, where routing and buffering functions take place electronically. The system architecture and performance will be described.

The optical switch is based on Optical Phased Array (OPA) technology. It is a 64 x 64, fully non-blocking, optical crossbar switch, capable of switching in a fraction of a nanosecond. The basic principles of operation will be explained. Loss and crosstalk results will be presented, as well as the results of BER measurements of a 160 Gbps transmission through one channel.
Basic principles of operation and measured results will be presented for the burst-mode-receivers, arbitration algorithm and synchronization.

Finally, we will present some of our current research work on a next-generation optical switch. 

The technological issues we have solved in our internal optical packet network can have broad applicability to any global optical packet network.

Optical packet switching

This chapter provides an outline of the main concepts and issues related to optical packet switching (OPS). The basic network functions required by this paradigm are discussed and references to past and current research on the topic are provided. Optical packet switching is a transport technique that assumes information to be organized in packets formed by a payload and a header both encoded as optical signals. The payload is transferred through the network without any optical to electronic conversion. The header is processed in the early phase in the electronic domain. Optical packet switching may be considered as a long-term and more flexible alternative to the circuit-switched optical networks currently being deployed by operators. This innovative paradigm aims at optimizing the utilization of the dense wavelength division multiplexing (DWDM) channels by means of fast and highly dynamic resource allocation, overcoming the inefficiency typical of the circuit transfer modes. Traditionally, packet transfer modes have proved to be very flexible by nature, with respect to bandwidth exploitation. In fact, link capacity is shared in time by means of statistical multiplexing, while contentions occurring at each node are solved by storing packets as long as the required resources become available again. Therefore, network links are in general used more efficiently in OPS than in circuit-switching.

Optical Packet Switching

This paper presents a technique to transmit large optical bursts over several wavelength channels in a parallel manner, which we refer to as optical burst switching with channel bonding (OBS-CB). It uses switching in the time domain only, while the wavelength domain is used to increase the transport rate, and thus to decrease the time required for transmission of a data burst. Different structures of the transceiver unit for edge nodes as well as methods for burst assembly and transmission are proposed and discussed. Three architectures of core nodes are described and studied with respect of their cascadability. The most important system parameters and limitations are discussed.

Optical burst-switched WDM networks with channel bonding

All optical bit parallel transmission systems are discussed and two different schemes for bit skew compensation are presented, based on dispersion managed fibers (DMF) and a fiber grating based scheme. An experimental system with two wavelengths is employed in order to measure the bit skew in a single mode fiber. Results show that DMF can virtually cancel the differential group delay as different wavelengths travel in the same fiber. A 10 Gword/s signal over 40-km of DMF is proposed and an aggregate bit-rate /spl times/ distance product of 160 Gbit/s /spl times/ 40-km is obtained.

All optical bit parallel transmission systems

This paper demonstrates the feasibility of a bit parallel WDM (BP-WDM) system using dispersion managed fibers. An expression for the total bit skew as a function of the fiber dispersion and system bandwidth is derived and compared with experimental results. A 4 bit/spl times/10 Gbit/s-per bit BP-WDM transmission experiment over 30 km DMF is used and an aggregate bite rate/spl times/distance product of 1.2 Tbit/s-km is obtained. The total bit skew of the system is reduced to one half of the bit period. We believe that systems using BPWDM will be useful for computer interconnects in high-speed parallel systems and ring networks.

V. A. Bhagavatula

Papers

Multi Gbit/s bit parallel WDM transmission using dispersion managed fibers