Physical Layer scalability of WDM optical packet interconnection networks

Abstract

Abstract-The physical layer scalability of a packet-switched optical interconnection network utilizing semiconductor optical amplifier (SOA) switch elements is investigated experimentally and with numerical modeling. Optical packets containing payloads of multiple wavelength-division-multiplexing (WDM) channels are propagated through cascaded SOA-based switching nodes in a recirculating test-bed environment. Experiments show that bit-error rates (BERs) below 10 −9 can be maintained through 58 switching nodes for the entire eight-channel 10-Gb/s-per-channel payload distributed over 24.2 nm of the C-band. When the packet payload consists of a single 10-Gb/s channel, 98 node hops can be traversed before a BER of 10 −9 is exceeded. In conjunction with the experiments, a novel phenomenological modeling technique is developed in order to forecast the scalability of SOA-based WDM packet interconnection networks. This technique is shown to yield results that correlate well with the experimental data. These investigations are presented as predictors of the physical limitations of large-scale WDM packet-switched networks.Index Terms-Interconnection networks (multiprocessor), optical interconnections, packet switching, semiconductor optical amplifiers.

A Modular, Scalable, Extensible, and Transparent Optical Packet Buffer

“…From this selection of routing options, it can be deduced that each SOA hop introduces approximately 0.4 dB of power penalty on average. This result is similar to those for other simplistic SOA-based OPS nodes and modules [11], [15], [17], [23], [24]. Also, in order to demonstrate the wideband transparency of the buffer implementation, eye diagrams for different payload wavelengths are presented as well (Fig.…”

“…Because these losses depend on which branches are required for a particular module implementation, the SOAs are set to deliver between 6 and 11 dB of gain, which requires between 45 and 75 mA of drive current. The net gain or loss incurred on each packet payload can be kept to less than about 0.5 dB, as in [15], [16], and [24].…”

“…The 90-ns packets, which are spaced in 102-ns timeslots, contain a 10-Gb/s payload in addition to a unique 7-bit packet label, so that individual packets can easily be identified during the experiment. Incoming packets have a total average power of approximately −10 dBm; this keeps the SOAs well within the linear operating regime [24]. The implemented two-module buffer also includes internal packet and read request signal monitoring for troubleshooting and verification.…”

Polarization-Dependent Gain in SOA-Based Optical Multistage Interconnection Networks

“…The inherent polarization-dependent gain (PDG) of the SOA, albeit very small in modern devices [11], [12], accumulates as the packets propagate through a cascade of SOA-based nodes and affects the overall system performance. In fact, we observed, in our previous studies of optical packets propagation carrying eight 10-Gb/s WDM channel payloads, that packet polarization influences the node cascadability even when using commercial SOAs with very low PDG [10]. The origin of PDG in SOAs is the fact that bulk active material has much larger transverse electric (TE) amplification than transverse magnetic (TM), which is due to the different confinement factors [11].…”

“…Aside from acting as a gating switch, the SOA compensates for the optical power losses from the passive optical components of the node structure (e.g., couplers, delay lines, and connectors). The performance and scalability of SOA-based OPS networks have been investigated for a range of architectures [7], [9], [10], without necessarily considering the effect of the component's polarization dependence. The inherent polarization-dependent gain (PDG) of the SOA, albeit very small in modern devices [11], [12], accumulates as the packets propagate through a cascade of SOA-based nodes and affects the overall system performance.…”