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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 components
FDL Delay devices Optical buffers
DWDM Technical challenges Synchronizations Current system developments Spacing and TDM maximum rates it can handle Coarse WDM
Wavelength converters Availability
Optical switching technology Bubbles Mirrors
Fiber technology ADM and multiplexers Amplifiers 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
Next generation networks [19,20,7]
OADM (point-to-point with no
switch)
OADM (with switch)
OXC (Layers approach – no WLC)
OXC with WLC
Topology P2P WDM WDM Ring Mesh/Ring Mesh
Path Control Static - Dynamic Packet-based Dynamic
Capacity - 100 Gb/s – Tb/s 100 Tb/s Pb/s
Types: Network/Switch
Opaque Opaque Opaque Transparent
Opaque Opaque Transparent Transparent
Generation/ Availability
First Second Third Fourth
Now 1999-2005 2005-2010 2010+
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 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 and
Switching technology
Optical Cross-connects
Types and Capabilities Basic components Architecture [2,4,6] Commercially available systems Reported experimental systems
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 Bit rate
Cost of O
-e-O
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 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 Fabric
Optical FabricWith standard
interface (1.3 or 1.5 um)
Optical transport System (L,C, S, etc.)
Electrical Fabric
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
Bit rate
Cost
MEMS-based Fabric
Electronic Fabric
Optical Switching TechnologyMEMS 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
Applications 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)
Availability AT&T offers 1000 or more mirrors Lucent offers 1024 ports in their LambdaRouter
MEM 2D
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
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]
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
WDM System
CLK EXT
BPF(x)
PreAMp
BPF(y)
DispCompen
Filter(DCF)
AWG
EA RXERRDET
AWG
AWG
AWG
AM
PA
MP
MON PROCESSOR
MOD AMP
NRZ PRBS
COMP
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 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
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)
References1. Opaque and Transparent Networking (Optical Networks Magazine, Tutorial Corner, May/June 2003) 2. Role of Optical Network in ResilientIP Backbone Architecture (Optical Networks Magazine, Tutorial Corner, Sep./Oct. 2003) 3. 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 20034. Architectures, Technology, and Strategies for Gracefully Evolving Optical Packet Switching Networks Alexandros Stavdas, National Technical
University of Athens, Greece Optical Networks Magazine, May/June 20035. 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 6. 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
7. N. Ghani, K. Sivalingam (Editors), Optical Networks, Special Issue on Topics in Optical Communications, to appear Spring 2004 8. Volume: 41, Issue: 9, Year: Sept. 2003 DWDM: Networks, Devices, and Technology Jajszczyk, A. Page(s): 29- 33 Communications Magazine,
IEEE 9. D. Bishop, C. Giles, and G. Austin, "The Lucent LambdaRouter: MEMS technology of the future here today," Volume: 40, Issue: 3, Year: March.
2002 Communications Magazine, 10. P. B Chu, S. Lee, and S. Park, ?MEMS: The Path to Large Optical Crossconnects” Volume: 40, Issue: 3, Year: March. 2002
Communications Magazine, 11. P. Dobbelaere, K. Falta, L. Fan, S. Patra, “Digital MEMS for optical switching” Volume: 40, Issue: 3, Year: March. 2002 Communications
Magazine, 12. 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. 13. 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.
14. 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.
15. 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
16. Jajszczyk A., Automatically Switched Optical Networks (ASON), 2003 Workshop on High Performance Switching and Routing HPSR 2003, Torino, Italy, June 24-27, 2003
17. Page 1178 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 20, NO. 2, FEBRUARY 2002 Architectural Design for Multistage 2-D MEMS Optical Switches Gangxiang Shen, Member, IEEE, Tee Hiang Cheng, Member, IEEE, Sanjay K. Bose
18. R. Ramaswami and KN sivarajan, “Optical Networks: A PracticalProspective”, San Francisco, CA, Morgan Kaufmann Publishers, Inc. 1998 19. 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.
20. 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
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_0
7_18_02.htm http://www.spie.org/web/oer/november/nov00/wdm.
html http://www2.rad.com/networks/1999/wdm/
wdm.htm#Figure15
Questions
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
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?