2016 02 02 - business case for new subsea and terrestrial builds in africa - ngon africa 2016...

© 2016 Xtera Communications, Inc. Proprietary & Confidential 1

Business Case for New SubSea and Terrestrial Builds in Africa

Robert J RichardsonXtera Communications

2-3 February 2016NGON Africa 2016

Cape Town, South Africa


• Submarine system

• Technology evolution

• Can new terrestrial connectivity offer restoration alternatives to subsea cable systems

• Challenges for the future

Business Case for New SubSea and Terrestrial Builds in Africa


Not neededif short enough

• SLTE Submarine Line Terminating EquipmentSpecialised DWDM terminal

• PFE Power Feed EquipmentHigh voltage to feed long spans

• Repeater Protects Amplifier-pairs

• Cable Protects fibersProvides power path

• BU Branching Unit Routes fibers or wavelengths

• Marine Survey, installation, maintenance

What’s in a Submarine System?

Rep Rep Rep BU Rep

SLTESLTE

SLTESLTE

PFE


• More expensive than terrestrial!

• Targets longer spans

• Needs to withstand: water pressurecorrosionanchors, fishing vesselshigh-voltages

• Very high reliability repairs are difficult, expensive, take timeand cause outage on all fiber pairs

• Similar technology to terrestrial, but some important differences

What’s different? Submarine/Terrestrial


1 Command / response– Access one repeater at a time

– Fast response

2 Loopback– Use probe signal and get returns from all

amplifiers

– Signal average to get loop losses

– Simpler, but less information

Terminal Equipment and Submarine monitoring

Rep Rep Rep


• PFEs at each end for security – voltages up to 15,000 V

• Return current flows to ground – dedicated connection

• Tolerates shunt fault – cable insulation broken, fibers intactcreates a local ground connection

• PFE voltage adjusts automatically

• Reliability is critical – failure affects all traffic

Power Feeding

repeaters repeaters

PFE

repeaters

PFE

PFE

PFE


Repeater

CableTermination

Housing

Flexible joint

Buffer

High reliability design with multiple pumps


• Routes fibers

• Routes wavelengths

• Remotebox

FlexibleBettersparing

Branching Unit

Filters

Fibres

Power

BU


• Several variants– LW Light Weight

– LWP Light Weight Protected (includes aluminum tape)

– SA Single Armored

– DA Double Armored (shown below)

– ...

• Fibers protected in central steel tube

• Tensile wires form protective cage

• Seam-welded copper tube blocks hydrogen

• Polyethylene (high-voltage) insulation

• Repeaterless cable uses smaller diameter,carbon-loaded polyethyleneSmaller, slightly cheaper

Cable for Repeatered Systems


• Survey to find best cable route– Desktop

– Marine

• Install with correct vessel– Clear route

– Lay cable

– Post lay inspection

– May include cable burial

– Shore ends

beach trench and manhole

articulated pipes

...

The Marine Element


• Industry standard typical numbers

• Shallow (<1000 m) repairs: 0.5 dB every 20 km

• Deep (>1000 m) repairs: 3.0 dB every 1000 km

• Fiber ageing: 0.005 dB/km

• Pump failures: 1 failure in 5% of amplifiersat End Of Life

Depth Profile / Repairs / Ageing

-6000

-5000

-4000

-3000

-2000

-1000

0

0 200 400 600 800 1000 1200 1400

Depth (m) v. Length (km)Dania Beach GTMO

Depth (m)

A B

Burial limit


• More capacity = more repeaters (or more fiber pairs) = more cost

• Wider bandwidth repeaters = more capacity

• Technology evolution must be considered as alternative to initial CapEx

• System design – Repeater spacing to maximize capacity & enable deployment of new

technology

– Optimize system powering design

– System architecture

• Open Line System (OLS) design

• Unrepeatered or OADM branches, where possible

– Power budget

• Optimize route design to minimize “OpEx”– Direct routes

– Cable protection

– Deep water

Submarine System Cost / Capacity

Optimize capacity vs cost balance to maximize return on “CapEx Investment”


Evolution


SubSea Network Evolution Example

Initial design: 1 x 2.5G

Upgrade with 100G technology: 4 x 100G a 60 increase in capacity

Americas I North & Columbus 2B deployed in 1994


History

• WDM 4 to 100 wavelengths ...

• Line-rate 2.5, 10, 40, 100, 400 Gbit/s per fiber (2 WLs)...

• Networks Point-to-point , festoons, rings, multiple BUs...

Enablers

• Better optical filters

• More bandwidth and power in amplifiers – more fibers?

• Forward Error Correction (FEC)

• Coherent detection + Digital Signal Processing (DSP)– More sensitivity + electronic dispersion compensation

– Support for multiple formats (e.g. QPSK, 8QAM, 16QAM)

• Multi-level modulation schemes

• ... More advanced repeaters?

Evolution (= More Capacity)


Q limit dB

1. No FEC 17

2. Soft decision FEC 5.5 (Second generation)

• Rapid progress, but now nearing the limit set by Shannon’s law

Improved FEC

5 FEC overhead (%)

Hard-decisiontheoretical limit

10 15 20 25 30

5

6

7

8

9

10

11

Net

codin

g g

ain

(dB)

12

13Soft-decision decoding

RS (239,255)


Benefit of Different Modulation Formats

QPSK 16 QAM

7 dB 10 dB

2 bit/symbol

100G

3 bit/symbol

150G/300G

4 bit/symbol

200G/400G

More power / OSNR than BPSK

BPSK

1 bit/symbol

100G

3 dB0 dB

8 QAM

0

1

2

3

4

5

6

7

8

BPSK QPSK 8QAM 16QAM 32QAM 64QAM

Power per bit

Higher line-rates need significantly higher OSNR


• QPSK

• 16QAM +7 dB OSNR2x capacity

• QPSK More bandwidth 2x capacity+3 dB repeater power

• Bandwidth: the better solution for difficult systems

Higher Level Modulation or More Bandwidth?


Terrestrial Systems as Restorations Alternatives for SubSea Systems


• To backhaul traffic to land-locked countriesand inland PoPs / DCs

• To offer restorationalternatives forsubsea cable systems

Need For More Light Into Africa


January 2016:

• Three subsea cable cutsoff Alexandria

• Cuts on two independentterrestrial segmentsacross Egypt

74% of internetconnectivity lost in Gulfcountries, and 100% inSouth Africa for few hours

Need For More Diversity


Direct PoP to PoP

• Traditional

• Better?

• Eliminates two TTEs

• Needs ILAs compatible with submarine amplifiers

• Needs good terrestrial protection scheme

Integrating the Terrestrial Part

SLTE TTE TTE

SLTEAMP


Protected Backhaul

CLS

DC

ROADM

68.2km

68km 83km 70km80km 75km 45km 63km 53km 77km 60km 69km 92km51km

66km

37km80km66km49km91km50km64km74km75km65km70km63km

75km

Working

Protect

ILA

73km

DC


Challenges for Future


OBJECTIVE

• Maximum capacity per fiber80 nm = 25/50T

• Longer spans

• More pairs with modest capacity

• Other features– Environmental sensors

– Turn-down unused pairs

– …

• Anything else?

• Faster implementation

POTENTIAL ISSUE

• Will need extra pumpsMore power

• Lower loss, more Raman gain

• Takes space in housing

– Complex mechanics

– How does one monitor?

SOLUTION

• More compact design

• More efficient poweringPossible scheme

• More modular system design

Next Gen System: Which Technology Will Enable the Next Step?

26

Any Questions?

Thank you for listening