F. Zhang

Reconfigurable free-space optical cores for storage area networks

The role of the optical storage area network is becoming increasingly important in computer network architectures, with the amount of information being presented and requested on the Internet ever increasing. One of the key questions is what is the role of, and how do we control, an optical switch core within a SAN to optimize its performance. In this article we review two potential optical switch technologies and assess their performance as a SAN optical switch core.

Implementation of a 6

A shutter-based free-space optical switching architecture capable of multicast transmission functionality has been proposed as a promising switching technology for storage area network applications. The main idea behind this type of switching architecture is that the system performance can be enhanced with a new electro-optical material, used for the shutters to increase switching speed. It can be distinguished from previous shutter-based optical switches which have been based on single channel to single channel switching, as we present a reconfigurable design of a 6 × 6 72-channel shutter-based optical switching core based on multimode fiber ribbon to multimode fiber ribbon switching. The design and implementation of a prototype 6 × 6 72-channel multi-mode fiber ribbon switch demonstrator utilizing a submicrosecond PLZT-based spatial light modulator as a shutter is reported. The light loss, crosstalk, and data switching characteristics of the implemented fiber ribbon switch from the evaluation tests were measured and are presented.

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Optical switches based on liquid crystal SLM (Spatial Light Modulators) have traditionally been considered unsuitable for packet switching due to slow reconfiguration speed. In this paper we investigate the constraint of reconfiguration time in an optically interconnected packet switch. A system architecture based on the established knockout principle and input/output buffers is simulated with self-similar traffic patterns and packet length statistics obtained from NLANR. Analysis includes packet delay distribution, queue length growth. A physical realisation of the system will use VCSEL arrays, detector arrays and multi-mode ribbon fibre. Data granularity of the system is chosen to match the specification of modern line cards used in routers. It is found that a reconfiguration time in the order of micro seconds is sufficient for an acceptable delay and loss rate. Relationships between required reconfiguration time and system parameters are established.

6 Free-Space Optical Fiber Ribbon Switch for Storage Area Networks

Storage Area Network (SAN) has gradually developed as the demand for storage capacity and fast access has increased. The traditional way of attaching storage directly to the servers over a SCSI bus has limited scalability. Several drawbacks and limitations have turned up. Switched Fibre Channel SAN resolves all of these issues. In this paper, the architecture of the switch fabric for the SAN is discussed. The complete design of the free-space optical switching core based on the diffractive element and the PLZT shutter is proposed.

SLM reconfiguration time in optically interconnected packet switch

With increasing demands on storage devices in the modern communication environment, the storage area network (SAN) has evolved to provide a direct connection allowing these storage devices to be accessed efficiently. To optimize the performance of a SAN, a three-stage hybrid electronic/optical switching node architecture based on the concept of a MPLS label switching mechanism, aimed at serving as a multi-protocol label switching (MPLS) ingress label edge router (LER) for a SAN-enabled application, has been designed. New shutter-based free-space multi-channel optical switching cores are employed as the core switch fabric to solve the packet contention and switching path conflict problems. The system-level node architecture design constraints are evaluated through self-similar traffic sourced from real gigabit Ethernet network traces and storage systems. The extension performance of a SAN over a proposed WDM ring network, aimed at serving as an MPLS-enabled transport network, is also presented and demonstrated.

Free-space optical switching core for storage area network

Reconfigurable shutter-based free-space optical switching technologies using fiber ribbon and multiple wavelengths per fiber for Storage Area Networks (SANs) application are presented and demonstrated.

Free-space optoelectronic switching cores with MPLS for SANs over WDM ring networks

A shutter-based free-space optical switching core has been proposed as a promising technology for constructing Storage Area Networks (SANs) over an optical network. A vital component of this switch architecture is the use of a spatial light modulator (SLM) which can enhance the SANs performance. New optical materials are utilized to raise the switching speed and ferroelectric liquid crystals (FLCs) or transparent lanthanum-modified lead zirconate titanate (PLZT) used as an SLM have been compared. Both are capable of reaching the 3 usec target, by either raising the temperature or switching voltage, which is acceptable for SANs since the performance is dominated, not so much by switching speed, but more by reliable robust switching throughput. A six-by-six free-space 12-channel multi-mode fiber ribbon switch system using one fixed wavelength has been implemented. The objective of this paper is to demonstrate that multiwavelength operation based on the CWDM band in each fiber can be implemented on the same shutter-based free-space optical switching architecture using a FLC SLM.

Reconfigurable free-space optical switching technologies for Storage Area Networks

Passive optical interconnection is being used in large packet switches to allow size scale up and more efficient heat dissipation from the electronic processors. The line card is the electronic island whose size is determined by thermal dissipation technology. We have selected an optical interconnection technology that is low cost, fiber ribbon, and we are working on the shutter arrays, which allow active routing. This will reduce the demands on the electronic processors. Progress on a 180 Gbps switch will be reported.