deploying 40gbps wavelengths and beyond
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Deploying 40Gbps Wavelengths and Beyond. Brian Smith. Agenda. What are the future requirements of R&E networks ? What are the options for upgrading capacity on R&E networks Some cost comparisons. Challenges of deploying 40Gb/s wavelengths over 10Gb/s Infrastructure What about 100G+ ?. - PowerPoint PPT PresentationTRANSCRIPT
Deploying 40Gbps Wavelengths and BeyondBrian Smith
Confidential
Agenda
What are the future requirements of R&E networks ?
What are the options for upgrading capacity on R&E networks
Some cost comparisons.
Challenges of deploying 40Gb/s wavelengths over 10Gb/s Infrastructure
What about 100G+ ?
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Requirements for Regional Optical Research
Networks
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Requirements
Transparency Carry any service (Ethernet SONET, SAN) at wire speed from GigE to
10GigE and beyond.
Capacity Growth Seamless and cost effective capacity growth which supports emerging
40G wavelength technologies.
Ability to add wavelengths at any supported data rate without affecting existing traffic.
Dynamic Light-path Control Dynamic control plane (e.g UCLP, GMPLS)
Integration with IP/MPLS control plane for dynamic traffic engineering (e.g HOPI).
Client on-demand light paths.
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Options for Future Capacity Growth
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Capacity Growth in RONs
Continue to add 10G wavelengths in existing infrastructure. Up to 320Gb/s capacity with 100GHz spaced DWDM.
Accelerates fiber exhaust
Upgrade to 50GHz 10Gbps system Up to 640Gb/s capacity with 50GHz spaced DWDM.
Needs new terminal equipment.
Service disrupting
Cost effective in the longer term ????
Overlay 40Gb/s wavelengths in existing 10G infrastructure. No service disruption
Expands system capacity – delays requirement to light new fiber.
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Some Cost Comparisons
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Assumptions
Fully dynamic ‘Any-to-Any’ wavelength optical network.
Optical ROADM using WSS technology available at 100GHz and 50GHz.
No penalty associated with cascaded ROADM
Add 40Gbps wavelengths after 75% capacity reached.
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Continue to Add 10G Wavelengths
10Gbps (100GHz)
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# wavelengths
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Cap
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Cost/Gbps Capacity
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Upgrade to 50GHz 10Gb/s System
10Gbps (50GHz)
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au)
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y(G
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Cost/Gbps Capacity (Gbps)
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Overlay 40Gb/s Wavelengths in Existing 10Gb/s Infrastructure
10Gbps + 40Gbps Overlay (100GHz)
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# wavelengths
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Cost/Gbps Capacity
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Cost Comparison
Overlaying 40Gb/s wavelengths on an existing 10Gb/s infrastructure leads to lower cost per GigE in the long term.
Higher costs in 50GHz 10Gb/s option mainly due to: Higher cost of 50GHz ROADM compared to 100GHz ROADM
Higher cost of wave-locked MSA transponders (compared to XFP based transponders).
Assuming that 40Gbp/s wavelengths can be supported over an existing 10Gb/s network , this is a bandwidth efficient and cost effective way of delaying the requirement to light a new fiber pair.
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Wavelength Switching Trends
4 8 12 16 20 24 28 32Pass-through Channels
Optical ROADM
ElectronicROADM
Optical ROADM
ElectronicROADM
10G
2.5G
ChannelRate
What are the cost sweet spots today ?
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Wavelength Switching Trends
4 8 12 16 20 24 28 32Pass-through Channels
Optical ROADM
ElectronicROADM
Optical ROADM
ElectronicROADM40G
10G
ChannelRate
How will this change as 10G costs go down ?
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40Gb/s Challenges
Tolerance to Chromatic Dispersion (CD)
Tolerance to Polarization Mode Dispersion (PMD)
OSNR Tolerance
Spectral Width
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Tolerance to Chromatic Dispersion – 40G
6 spans x 80km x 26dB SMF-28 : 32 NRZ modulation format, zero chirp, +FEC.
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Net Dispersion (ps/nm)
dB
Q p
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+/- 50 ps/nm
Equivalent to 3km SMF
Dispersion variation with
Temperature (+/- 40 deg)
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Impact of Dispersion Tolerance at 40Gb/s
So what does this mean ?
40Gb/s wavelengths need to have adaptive dispersion compensators.
If you plan to deploy 40Gb/s in the future, consider measuring the net dispersion as accurately as possible
Using other modulation formats (such as Duo-binary) increases the dispersion tolerance window by 3-4 times.
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PMD Tolerance
Some examples
PROTOCOL Max PMD
(1dB penalty)
Average PMD
GigE 220 60
OC48 115 30
10GigE 27 8
40G (NRZ) 7* 2*
* Other non binary modulation techniques can increase the PMD tolerance for 40Gb/s
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PMD Tolerance
So what does this mean ?
Take the 6 spans x 80km SMF-28 example.
Dark Fiber Age Average link DGD (ps)
>1995 2
<1995 10
With older fiber, the 10GigE traffic will see PMD hits on traffic
With new fiber, the 40G traffic can be supported.
Performing a PMD measurement on your fiber plant will define whether 40Gb/s traffic can be supported or not !
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OSNR Tolerance
OSNR required for 40Gb/s is larger than that for 10Gb/s for the same BER.
Reach for 40Gb/s reduced compared to 10Gb/s
CS-RZ modulation format and enhanced FEC coding on the 40Gb/s wavelengths reduces the mismatch in required OSNR.
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Spectral Width
The modulation format used for 40Gb/s will determine the spectral width.
Wavelengths in a fully dynamic network will traverse a cascade of ROADM – Leading to filter pass-band narrowing.
The 40Gb/s modulation format chosen (NRZ, CZ-RZ Duo-binary) must be able to pass through the cascade without distortion.
For this reason, it is likely that the 40Gb/s in a dynamic network will use spectrally efficient modulation formats (Duo-binary, CS-RZ)
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What about 100Gb/s + ?
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100Gb/s
Native 100Gb/s transmission is not likely in the near term Electrical Mux and Demux very challenging at this rate
Availability of optical modulators with sufficient electrical bandwidth
Clock recovery at this rate is extremely difficult
If electro/optic components were available . . . Spectral width ~ 150GHz so wouldn’t fit into a 100GHz pass-band
(<80GHz). Would need >1 bit/symbol coding
Dispersion tolerance ~ ± 10ps/nm.
PMD tolerance < 1ps
OTDM techniques are only approaches currently being developed for ultra high speed transmission.
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100Gbps
Duo-binary, QPSK
Wave-locker
1b/s/Hz
Too many bits/symbol required
Too many bits/symbol required
40Gbps
NRZ/CS-RZ/
Wave-locker
10G overlay
0.4b/s/Hz
Duobinary
Wave-locker
0.8b/s/Hz
Too many bits/symbol required.
No ROADM
1.6b/s/Hz
10Gbps
No issue
NRZ
0.1b/s/Hz
Reduced reach
Wave-locker
NRZ
0.2b/s/Hz
Reduced reach
No ROADMs
Wave-locker
0.4b/s/Hz
100GHz 50GHz 25GHz
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Summary
R&E Regional Optical Networks will require Seamless Capacity Growth and Dynamic Light-path Control.
Deploying 40Gb/s wavelengths in existing 10G networks offers reductions in the cost per GigE as capacity grows.
10G switching will evolve towards Electronic ROADM as component costs continue to fall – Optical ROADM more cost effective for 40G traffic.
If 40Gb/s is to be added to 10Gb/s infrastructure
Need accurate measurements of Dispersion and PMD
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Summary
40Gb/s modulation formats are available that
Improve the OSNR, CD and PMD tolerance
Allow transport through cascaded optical ROADM
The technology for 100Gb/s line rates is under development but not available.
OTDM is the current approach used for single channel ultra high speed transport