Transparent Optical Switches: Technology Issues and Challenges

Increased traffic volume due to the introduction of new broadband services is driving carriersto the deployment of an optical transport layer based on Wavelength Division Multiplexing(WDM) [1]. The network infrastructure of existing core networks is currently undergoing atransformation from rings using SONET Add/Drop Multiplexers (ADMs) to mesh topologiesusing Optical Cross-connects (OXCs). A core optical network architecture can be opaque ortransparent. An opaque architecture means that the optical signal carrying traffic undergoesan Optical to Electronic to Optical (OEO) conversion at different places in the network. Atransparent architecture means that the optical signal carrying traffic stays in the opticaldomain from the time it is generated at the edge of the network until it leaves the network.Even though the applications driving thelarge scaledeployment of transparent optical switches are notcurrently in place (niche applications in today’s networks onlyuse a very small number of transparent switches), and the trafficdemand does notcurrently justify theuse of transparentswitches that are cost effective at very high bit rates,it is possible that atsome point in the futuretransparent switches may be deployed in the network. Based on thisassumption, this paper explores the technology issues and challenges that are associated with3D MEMS-based switch fabrics. These fabrics offer the most viable approach to makesingle-stage switch fabrics with large portcounts that can be used for thedeployment of transparent switches in the network.Figure illustrates the four different node architectures that can comprise a core optical1network. The first architecture shows a fixed patch panel. Fixed patch panels located betweenWDM systems with transponders are currently being replaced by opaque (OEO) switchingnodes (with electrical switch fabrics) as shown in architectureof Figure (b). This is an1 opaque network architecture, as the optical signal undergoes OEO conversions [2]. The thirdarchitecture shows a transparent (OOO) switch between WDM systems with transpondersthat iscomplemented by an OEO switch for drop traffic. This is once again an opaquenetwork architecture, as the optical signal undergoes OEO conversions at the WDM

[1]  Angela Chiu,et al.  Issues for routing in the optical layer , 2001, IEEE Commun. Mag..

[2]  Chung-Sheng Li,et al.  Gain equalization in metropolitan and wide area optical networks using optical amplifiers , 1994, Proceedings of INFOCOM '94 Conference on Computer Communications.

[3]  G. Keiser.  Optical Fiber Communications , 1983 .

[4]  David J. Bishop,et al.  Challenges of packaging MEMS components for the all-optical networks of the future , 2001, Symposium on Design, Test, Integration, and Packaging of MEMS/MOEMS.

[5]  Byrav Ramamurthy,et al.  Optimizing amplifier placements in a multiwavelength optical LAN/MAN: the equally powered-wavelengths case , 1998 .

[6]  H. Laor.  MEM mirrors application in optical cross-connects , 1998, 1998 IEEE/LEOS Summer Topical Meeting. Digest. Broadband Optical Networks and Technologies: An Emerging Reality. Optical MEMS. Smart Pixels. Organic Optics and Optoelectronics (Cat. No.98TH8369).

[7]  J. A. Walker,et al.  Dynamic spectral power equalization using micro-opto-mechanics , 1998, IEEE Photonics Technology Letters.

[8]  Biswanath Mukherjee,et al.  WDM optical communication networks: progress and challenges , 2000, IEEE Journal on Selected Areas in Communications.

[9]  S. Pannu,et al.  Closed-loop feedback-control system for improved tracking in magnetically actuated micromirrors , 2000, 2000 IEEE/LEOS International Conference on Optical MEMS (Cat. No.00EX399).

[10]  Lih Y. Lin,et al.  Free-space micromachined optical switches with submillisecond switching time for large-scale optical crossconnects , 1998, IEEE Photonics Technology Letters.

[11]  Byrav Ramamurthy.  Impact of Transmission Impairments on Network Performance , 2001 .

[12]  Thomas E. Stern,et al.  Multiwavelength Optical Networks: A Layered Approach , 1999 .

[13]  J.P. Heritage,et al.  Transparent vs. opaque vs. translucent wavelength-routed optical networks , 1999, OFC/IOOC . Technical Digest. Optical Fiber Communication Conference, 1999, and the International Conference on Integrated Optics and Optical Fiber Communication.

[14]  M. Wu.  A low voltage micromachined optical switch by stress-induced bending , 1999, Technical Digest. IEEE International MEMS 99 Conference. Twelfth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.99CH36291).

[15]  S. Chaudhuri,et al.  Addressing transparency in DWDM mesh survivable networks , 2001, OFC 2001. Optical Fiber Communication Conference and Exhibit. Technical Digest Postconference Edition (IEEE Cat. 01CH37171).

[16]  Eric Bouillet,et al.  Invited: Routing Strategies for Capacity-Efficient and Fast-Restorable Mesh Optical Networks , 2004, Photonic Network Communications.

[17]  R. R. Cordell,et al.  The Case for Opaque Multiwavelength Optical Networks , 1995, IEEE/LEOS 1995 Digest of the LEOS Summer Topical Meetings. Flat Panel Display Technology.

[18]  Debasish Datta,et al.  Impact of transmission impairments on the teletraffic performance of wavelength-routed optical networks , 1999 .