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Outline. Basic components Optical network evolution Next generation AON WDM systems Components Architecture Commercially existing systems Developing systems Optical Cross-connects Components Architecture Commercially existing systems Developing systems

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  • Basic components
  • Optical network evolution
  • Next generation AON
  • WDM systems
    • Components
    • Architecture
    • Commercially existing systems
    • Developing systems
  • Optical Cross-connects
    • Components
    • Architecture
    • Commercially existing systems
    • Developing systems
  • Other related optical components
  • References
  • Questions
optical technology recent advances

Optical Technology – Recent Advances


Farid Farahmand

optical components

Delay devices

Optical buffers


Technical challenges


Current system developments

Spacing and TDM maximum rates it can handle

Coarse WDM

Wavelength converters


Optical switching technology



Fiber technology

ADM and multiplexers


Synchronization issues

Switching related issues

Optical phase locked loops

Optical transmitters and receivers

Cost of optical devices

Cost of fiber installation

Optical devices

Electronic devices

Optical system infrastructure

How many miles of fiber

SONET applications

Typical system capacity

Available networks

Optical attenuators

Operating range

Receivers and transmitters

Wavelength range

Operating band (L,S, etc.)

Sensitivity and output power

Bit error rate

What is expected traffic growth?

What are they saying?

Useful references and web pages

Optical components
next generation optical networks characteristics
Next generation optical networks Characteristics
  • The core architecture must be independent of signal format and bit rate
  • The edge must be flexible to handle variety of signal types
  • Provides various services (easily provisionable)
  • Have reasonable cost, high scalability
    • Network and node
  • Supports performance monitoring
technological challenges for the ngn
Technological challengesfor the NGN
  • Innovation in devices
    • Small and low-cost optical interfaces
    • VLSI, Fast programmable devices
    • Fast clock and data recovery devices (CDR)
    • High pin-count, low power
    • Hybrid designs (photonic and electronic integration)
  • Transmission technology
    • High efficiency (high spectral efficiency)
    • Use all bands
    • Cost per bit
    • Long haul transmission
  • Node technology
    • WL conversion capacity
    • Small footprint
    • Less heat and power
  • Network software
    • More intelligent networks
    • Considering the physical layer limitations
    • Developing autonomous systems

WDM technology


Switching technology

optical cross connects
Optical Cross-connects
  • Types and Capabilities
  • Basic components
  • Architecture [2,4,6]
  • Commercially available systems
  • Reported experimental systems
optical switching technology
Cost of O-e-O

Bit rate

Optical Switching Technology
  • A critical component in all-optical networks
  • Eliminates O-e-O converters
    • Reducing the cost
  • Key component in many optical devices:
    • Wavelength monitoring devices
    • Protection switching and restoration
    • OADM and OXC
    • Power limiters and variable attenuators
  • Basic issues
    • Categories (device types)
    • Architectures [2,4,6]
    • Technological limitations
    • Mechanisms
optical switching technology categories
Optical Switching TechnologyCategories
  • Opto-mechanical optical switches
  • Wave guide solid state optical switches
    • Electro-optical [18]
    • Thermal-optical
    • Acousto-optical
    • Liquid-crystal [3]
  • Micro-electromechanical optical switches
    • MEMS (2D and 3D) [5, 9,10,11,12,16]
  • Bubble optical switches [5,16]
optical switching technology categories characteristics 18
Optical Switching TechnologyCategories – Characteristics [18]
  • Opto-mechanical optical switches
    • Good performance; slow switching time; low cost; large size (IEEE march 2002 page 89)
    • Very low insertion (< 1dB); 1x2 or 2x2 switches; low port count
  • Wave guide solid state optical switches
    • Thermally changing the refractive index of the waveguide
    • Fast switching time; high cost; poor insertion loss
    • liquid crystal (changing polarization of incident light)–good insertion loss
    • Lithium niobate technology (changing the refractive index changes)
  • Micro-electromechanical optical switches
    • High performance; low loss; small size; reasonable price; moderate switching time
  • Bubble optical switches
    • High performance; low loss; small size; reasonable price; slow switching time
switching 16 1 oxc capacities types
Optical transport

System (L,C, S, etc.)

Optical Fabric

Optical Fabric

With standard


(1.3 or 1.5 um)



Switching [16,1] OXC Capacities Types
optical switching technology mems technology an introduction 9 10 11 12



Electronic Fabric

Bit rate

Optical Switching TechnologyMEMS technology – An introduction [9,10,11,12]
  • Micro-electromechanical switches
  • Fabricated on silicon substrate
    • Mature technology – similar to silicon integrated circuits
      • Starting with silicon wafer
      • At the end of the process a part of it is etched away – leaving pieces free to move
    • Small in size (few hundred microns)
    • Proven to be robust, long lived, and reliable
  • The basic idea is that the incoming light is reflected to outlet port
    • Micro mirrors (free space)
    • Independent of the data rate
    • Operating over the entire 1.3-1.6 u optical communication band
    • Very low optical losses (about 1.25 dB)
    • MEMS mirror arrays can have 256-1024 mirrors (Lucent)
  • MEMS technology
    • 2D (digital – standup and lie down positions – 45 degree position)
    • 3D (analog – two-axis motion)
  • Compared to other technologies
    • Provides a small footprint
    • Reliable
    • Full movement range
optical switching technology mems technology basic operation
Performance parameters: [9,10,11]

Path length dependent

Loss due to angular mirror

Loss due to clipping of light at the mirror boundaries


Protection and monitoring

Optical add/drop operations

Main issue:

Port count (NxN mirrors)

High loss for large port counts (path length grows linearly with N)


AT&T offers 1000 or more mirrors

Lucent offers 1024 ports in their LambdaRouter


Optical Switching TechnologyMEMS technology – Basic Operation
optical switching technology mems technology 3d mems
Optical Switching TechnologyMEMS technology – 3D MEMS
  • 3D MEMS
    • More complex
    • The mirror tilts freely
    • path length grows with squre(N) thus resulting in less loss
  • Research areas
    • Packaging and physical layer issues [9,10,11]
    • Algorithms to reduce the number of mirrors as port count increases [12]
    • Multi-stage switches [17]
available high capacity systems
Available High-capacity Systems
  • The Aurora Optical Switch
    • offers carriers of telecommunications services the flexibility of supporting up to 512 OC-48c/STM-16 ports or 128 OC-192c/STM-64 ports to a total of 1.28 Tbpsbi directional traffic.
  • NEC's ultra-dense DWDM system (SpectralWave)
    • It supports up to 160 2.5G and 10G wavelengths on a single fiber. The system's advanced feature set includes 4:1 multiplexing to carry four OC-48/STS-16 signals to be carried on a single 10G wavelength,
  • Astral Point (Alcatel) - OA 500 Modular Optical System
    • With a switch fabric that scales from 320Gb/s to 1.28 terabits, and interfaces that scale from DS1 to OC768, the ON 7000 SONET node meets carrier metro and regional inter-office transport needs for years to come. The node incorporates the highest port densities per bay of any announced product in the metro optical network equipment market. It can transport 576 DS3's, 864 OC3's, 288 OC12's, 72 OC48's and 36 OC192's per 45u bay.
  • Lucent (LambdaXtreme)
    • It carries up to 2.56 Terabits per second at 40G wavelengths as far as 1,000km (625mi) — and 1.28Tbps at 10G wavelengths for 4,000km (2,500mi)
  • Lucent (WaveStar OLS)
    • provides a 1.6 Tbps (up to 160 x 10Gbps wavelength) capacity over a single fiber
wdm system 13 14 15
WDM System [13,14,15]
  • A critical component to the high-speed high-capacity AON
  • Critical factor: capacity x distance product and the number of spans required
  • Capacity: TDM technology x WDM spacing
  • Spacing: Physical limitations, number of bands utilized
  • Distance: Physical limitations, SNR, Dispersion, Transmission lines, etc.
  • Critical components: TX, RX, Transmission line, Amplifiers
  • Discussion
    • Types and Capabilities
    • Basic components
    • Architecture
    • Commercially available systems
    • Reported experimental systems
testing wdm systems
Testing WDM Systems
  • Eye Diagram
  • Bit error rate
    • In presence of random noise:
      • Inter Symbol Interference (ISI) penalty
      • CDR Jitter tolerance
  • Receiver sensitivity
    • Minimum amount of power required to operate
    • Bit error rate vs. input power (dBm)
    • -21 dBm give about 10^-9 error rate
wdm experimental systems
WDM Experimental Systems
  • 320 Gbps System: 32 Channels; 10 Gbps / channel; 100 GHZ spacing; 500 Km; 125 Km per span – 1998 [13]
    • Using dual-stage flat-gain EDFA amplifiers
    • Single band [1-16 and 17-32]
    • 1532-1562 nm range
  • 10.92 Tbps System: 273 Channels; 40 Gbps / channel; 50 GHZ spacing; 250 Km; 2 spans – 2001 [14]
    • Triple band: S,C, L; separating even and odd channels
      • S Band: 1476.81 – 1508.01 nm (85 Channels)
      • C Band: 1526.83 – 1563.05 nm (92 channels)
      • L Band: 1570.01 – 1620.06 nm (96 channels)
    • Using gain shifted thulium doped fiber amplifier
  • 2.56 Tbps System: 64 Channels; 40 Gbps / channel; 100 GHZ spacing; 6000 Km; (used for submarine systems) – 2003 [15]
    • Diving single BW to two parts: 1540 – 1565 nm and 1570 – 1595 nm each having 32 channels; separating even and odd channels (band dividing)
    • Used a feedback mechanism to lower the transmission line non-liearity impact
other optical components
Other optical components
  • Power monitor www.protodel.com
    • No tapping
    • Non-invasive
  • Tunable lasers www.agilent.com
    • Ranges of 1260-1640 nm (E,S,C, L)
    • Used for CWDM (coarse WDM)
  • Opaque and Transparent Networking (Optical Networks Magazine, Tutorial Corner, May/June 2003)
  • RoleofOpticalNetwork in ResilientIP Backbone Architecture (Optical Networks Magazine, Tutorial Corner, Sep./Oct. 2003)
  • All-Optical Liquid-Crystal Signal Processing Technologies for WDM Networks Jung-Chih Chiao, Kuang-Yi Wu, Jian-Yu Liu, Chorum Technologies, USA 0 Optical Networks Magazine, May/June 2003
  • Architectures, Technology, and Strategies for Gracefully Evolving Optical Packet Switching Networks Alexandros Stavdas, National Technical University of Athens, Greece Optical Networks Magazine, May/June 2003
  • All-Optical Switching for High Bandwidth Optical Networks M. J. Potasek, New York University, USA Optical Networks Magazine Vol. 3, Issue 6 November/December 2002
  • Design and Performance of Optical Cross-Connect Architectures with Converter Sharing Teck Yoong Chai, Tee Hiang Cheng, and Gangxiang Shen, Nanyang Technological University, Sanjay K. Bose, Indian Institute of Technology, and Chao Lu, Nanyang Technological University Optical Networks Magazine Vol. 3, Issue 4 July/August 2002
  • N. Ghani, K. Sivalingam (Editors), Optical Networks, Special Issue on Topics in Optical Communications, to appear Spring 2004
  • Volume: 41,   Issue: 9,   Year: Sept. 2003 DWDM: Networks, Devices, and Technology Jajszczyk, A. Page(s): 29- 33 Communications Magazine, IEEE
  • D. Bishop, C. Giles, and G. Austin, "TheLucent LambdaRouter: MEMS technology of the future here today," Volume: 40,   Issue: 3,   Year: March. 2002 Communications Magazine,
  • P. B Chu, S. Lee, and S. Park, ?MEMS: The Path to Large Optical Crossconnects” Volume: 40,   Issue: 3,   Year: March. 2002 Communications Magazine,
  • P. Dobbelaere, K. Falta, L. Fan, S. Patra, “Digital MEMS for optical switching” Volume: 40,   Issue: 3,   Year: March. 2002 Communications Magazine,
  • Gangxiang Shen, Sanjay K. Bose, Tee Hiang Cheng, Chao Lu, and Teck Yoong Chai, "A Novel rearrangeable Non-Blocking Architecture for MEMS Optical Space Switch," Optical Network Magazine,vol. 3, no. 6, November/December 2002, pp. 70-79.
  • S. Bigo, A. Bertaina, M. W. Chbat, S. Gurib, J. Da Loura, J.-C. Jacquinot, J. Hervo, P. Bousselet, S. Borne, D. Bayart, L. Gasca, and J.-L. Beylat, “320-Gb/s (32 10 Gb/s WDM) transmission over 500 km of conven-tional single-mode fiber with 125-km amplifier spacing,” IEEE Photon. Technol. Lett., vol. 10, pp. 1045–1047, July 1998.
  • K. Fukuchi et al., "10.92 Tb/s (273 x 40 Gb/s) Triple-band/ultra-dense WDM Optical-Repeatered Transmission Experiment," OFC 2001 Technical Digest, 2001, pp. PD24/1–3.
  • 2.56-Tb/s (64/spl times/42.7 Gb/s) WDM transmission over 6000 km using all-Raman amplified inverse double-hybrid spans Morisaki, M.; Sugahara, H.; Ito, T.; Ono, T.; Photonics Technology Letters, IEEE  ,Volume: 15 , Issue: 11 , Nov. 2003 Pages:1615 - 1617
  • Jajszczyk A., Automatically Switched Optical Networks (ASON), 2003 Workshop on High Performance Switching and Routing HPSR 2003, Torino, Italy, June 24-27, 2003
  • Page 1178 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 20, NO. 2, FEBRUARY 2002 ArchitecturalDesignforMultistage 2-D MEMS Optical Switches Gangxiang Shen, Member, IEEE, Tee Hiang Cheng, Member, IEEE, Sanjay K. Bose
  • R. Ramaswami and KN sivarajan, “OpticalNetworks: APracticalProspective”, San Francisco, CA, Morgan Kaufmann Publishers, Inc. 1998
  • Shigeki Aisawa, Atsushi Watanabe, Takashi Goh, Yoshihiro Takigawa, Moasafumi Koga and Hiroshi Takahashi, Advances in Optical Path Crossconnect Systems Using Planar-Lightwave Circuit-Switching Technologies, IEEE Communications Magazine, vol. 41, no. 9, September 2003, pp.
  • Botaro Hirosaki, Katsumi Emura, Shin-Ichiro Hayano, Hiroyuki Tsutsumi, "Next-generation optical networks as a value creation platfom", IEEE Communications Magazine, no. 9, Sep 2003 pp. 65-71
wdm technology references
WDM Technology References
  • Rajiv Ramaswami Optical Fiber Communication: From Transmission to Networking http://www.comsoc.org/livepubs/ci1/public/anniv/rama.html
  • http://www.telcite.fr/nwdmen.htm
  • http://www.ngk.co.jp/english/new_rele/2000/2000_07_18_02.htm
  • http://www.spie.org/web/oer/november/nov00/wdm.html
  • http://www2.rad.com/networks/1999/wdm/wdm.htm#Figure15
  • When an optical signal is dropped on a node (receiver) how much power do we need? That is the minimum receiver sensitivity? This is useful for determining how practical tap-and-continue devices are
  • Impact of synchronization in WDM system, should WL be synchronized? To what degree?
  • WLC, how practical are they where are the recent developments?
what is next
What is next
  • Answer the questions
  • Present a better view of the network and its needs
  • More on proposed switch architecture [2,4,6] and the difference with the planar lightwave circuit switching [19,20]
  • We talk about optical amplitiers
    • What is the difference between the optical and electrical amplifiers requiring 3R? Both costwise and size wise
    • Is the size an issue?
    • What about the delay? So optical amplifiers are very critical in all-optical network design?In case of OeO is the amplifier format/rate dependent? I am sure it is because it does some kind of B1 error checking, as is the case for SONET
  • About wavelength conversions and their technological advances
    • The main issue is that current WLC are big and bulky, design wise they are very bulky. So it have 1024 of them …you can imagine the problem
    • So what can be done? Make them smaller?
    • Can you find a module from Alcatel?
  • More on optical devices: filtering devices, tap-and-continue devices
  • What is Autonomous Switched Optical Networks (ASON) and why are they useful [16]
  • Some basic information on the difference between the SOA and EDFA amplifiers – their BW, output power, gain, etc.
  • So what are the regeneration techniques? What is the problem if you convert the incoming WL into electrical signals?