don’t be overexposed with your naked cable · don’t be overexposed with your naked cable...
TRANSCRIPT
Don’t Be Overexposed With Your Naked Cable Mark Enright, Managing Director Customer Solu7ons
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Open Cables • Open cables are undersea telecommunica7ons infrastructure without any transmission equipment
• Included are cable, repeaters, branching units, OADM nodes, power feed equipment, line monitoring equipment, command response equipment, maintenance controller, etc.
• Not included are line cards.
• Why open cables? • Coherent transmission equipment is becoming commodi7zed • Easy integra7on with the terrestrial network • To provide a more flexible solu7on for some Customers
• What’s the holdup? • Cable acceptance criteria are based on Q-‐factor measurements • Q-‐factor fully describes the performance of an undersea cable • Q-‐factor is 7ed to the line card used for the measurement • Gain shape and OSNR are necessary but not sufficient to characterize a new cable
• Define a Figure of Merit that fully characterizes cable performance independent of any line card 27/1/15 2
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Other product and /or company names might be trademarks of their respective owners.
Basic Undersea Network Architecture
Open Cables do require some Dry Plant equipment • PFE Power Feed Equipment
• Powers the cable
• LME Line Monitoring Equipment • Monitors the undersea plant (cable, and repeaters)
• CRE Command Response Equipment • Controls branching units and ROADM
• MC Maintenance Controller • Element management system
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Terrestrial Network
BU
ROADM
Terrestrial Network
LTE
PFE CRE LME
Cable Sta7on
MC
LTE
PFE CRE LME
Cable Sta7on
MC
LTE
PFE
CRE
LME
MC
Terrestrial Network ? ?
? Open Cables do not have • LTE Line Termina7ng Equipment
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Other product and /or company names might be trademarks of their respective owners.
The Challenge of a Dark/Dim Fiber
• Op7cal Signal to Noise Ra7o (OSNR) is necessary but not sufficient for good transmission performance
• High performance fiber, short repeater spacing
• Low performance fiber, large repeater spacing
• Same OSNR, very different performance!
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OSNR Pe
rformance
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Modern Coherent Transmission
• No op7cal chroma7c dispersion management • Large accumulated dispersion values lead to noise-‐like nonlinear impairment – Gaussian Noise Model
• D = 20 ps/nm/km • L = 6,000 km • Δλ = 0.4 nm (50 GHz) • 100G: 30 GBd, Δt = 33 ps • D x L x Δλ / Δt = 1440 symbols overlap
• All coherent transmission formats experience the same nonlinear impairment! (assumes near Nyquist transmission)
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• Op7mum power is the same for all coherent modula7on formats
• System op7mized for one modula7on format is s7ll op7mal for any other
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4
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-6 -4 -2 0 2 4 6Pre-Emphasis [dB]
Q-F
acto
r [dB
] Ch76, 23 Loops, 3/4SPC QPSKCh76, 17 Loops, 9/12SPC 16QAMCh76, 13 Loops, 15/16SPC 16QAMCh76, 3 Loops, 5/6SPC 64QAM
Same Optimum Power for all Coherent Formats
J.-X. Cai et al., OFC/NFOEC 2014, Paper M2C.3
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Wet Plant Figure of Merit: SNRtot
• A coherent receiver cannot dis7nguish between linear noise PASE and nonlinear interference noise PNL (ignoring nonlinearity compensa7on)
• A back-‐to-‐back measurement (where PNL = 0) uniquely determines the rela7onship between Q-‐factor and SNR for any line card
• A system Q-‐factor measurement with that line card then determines the total system SNRtot at that wavelength including nonlinear impairments
• Knowledge of SNRtot allows performance predic7on of any other line card with known back-‐to-‐back performance
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𝑆𝑁𝑅↓𝑡𝑜𝑡 = 𝑃↓𝑐ℎ /𝑃↓𝐴𝑆𝐸 + 𝑃↓𝑁𝐿 Linear Noise Performance -‐ OSNR
Nonlinear Interference Noise See for example: P. Poggiolini, JLT, Vol. 30, No. 24, 2012, pp. 3857.
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Back-to-Back Noise Loaded Performance
• Transmiler is connected to the receiver
• Noise is added to vary the SNR
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RxTx
ASE
B2B
SNR
Q-‐Factor
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• Measuring Q-‐factor with line cards from Vendor 1 determines SNRtot
• Knowledge of SNRtot allows predic7on of Q-‐factor for line cards from Vendor 2
System Q-‐factor Vendor 1 System margin Vendor 1 System Q-‐factor for Vendor 2 System margin Vendor 2
Vendor 1
Vendor 2
System Margin for Different Vendors
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SNR
FEC 2
FEC 1
System SNRtot
Q-‐Factor
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Conclusions
• SNRtot uniquely determines wet plant performance and wet plant capacity for +D systems
• SNRtot is independent of line card performance • SNRtot can be used as acceptance criterion enabling truly open cables
• Open cables provide greater choice and flexibility • Ability to defer the LTE decision to later • Benefit from latest technology
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EVERY CONNECTION COUNTS
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Thank you!
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