OutlineHistory of lightwave undersea cable systemsOptical amplifier technologiesExamples of lightwave undersea cable networks

� TPC-5CN� APCN� FLAG� JIH

Future technologies� WDM� Optical Soliton

Transmission capacity of the underseacable systems in the Pacific ocean

.

20102005200019951990198519801975197019651960RFS Year

N u m b e r o f v o i c e c h a n n e l s

10

100

1K

10K

100K

1M

10M

TPC-1(Coaxial)

TPC-2(Coaxial)

TPC-3(Lightwave)

TPC-4(Lightwave)

TPC-5CN(Optical amplifier)

TPC-6(WDM or Soliton)

10 times capacity increase for every 10 years!

Lightwave undersea cable systemsin the Pacific ocean

TPC-5CNTPC-4

TPC-3

Major system parameters ofTPC-3 and TPC-4 system

TPC-3 TPC-4

Signal wavelength 1.3m 1.55m

Bit-rate 280Mbit/s 560Mbit/s

Modulation scheme IM-DD IM-DD

Repeater spacing 50km 120km

Light source FP-LD DFB-LD

Photo detector Ge APD InGaAs APD

Power supply current DC 1.6A DC 1.6A

Transmission loss characteristics of the SiO2 based optical fiber

.

1.71.61.51.41.31.21.11.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Wavelength (m)

T r a n s m i s s i o n L o s s ( d B / k m )

1.3mwindow

1.55mwindow

Basic system configuration of the lightwave undersea cable system

.

Term

inal

Equ

ipm

ent

Term

inal

Equ

ipm

ent

TerrestrialLinks

TerrestrialLinks

Powerfeeding

equipment

Rep.-1 Rep.-2 Rep.-n

System length

Opticalfibers

Powerfeeding

line Powerfeeding

equipment

Oceanground

Oceanground

Block diagrams of the repeater circuits.

PD LD

LD(STB)

EQLAMP

Decision

Timing

LDDriver

LDDriver(STB)

Cou

pler

SV1(OOS)

SV2(IS)

Inputfiber

Outputfiber

PDLD

LD(STB)

EQLAMPDecision

Timing

LDDriver

LDDriver(STB)

Cou

pler

SV1(OOS)

SV2(IS)

Inputfiber

Outputfiber

Downstream link

Upstream link

Reliability issues of the optical repeater

Component Target FIT Numbers Total FIT APD module 1.0 1 1.0 Optical switch 1.0 1 1.0 MIC(3R) 0.5 3 1.5 MIC(SV) 1.0 2 2.0 Transistor 0.2 2 0.4 Diode 0.2 5.5 1.1 L,C,R 0.01-0.05 320 5.8 SAW 0.5 1 0.5 Others 1.6 Total 14.9FITs

LD module less than 28 2(act&sb) 0.8

Design target : not more than 3 ship repair during the life-time (life-time = 25years) MTBF 10years less than 16FITs per one repeater (FIT = 109 hours / MTBF)

OutlineHistory of lightwave undersea cable systemsOptical amplifier technologiesExamples of lightwave undersea cable networks

� TPC-5CN� APCN� FLAG� JIH

Future technologies� WDM� Optical Soliton

Principle of the Erbium-doped fiber optical amplifier (EDFA)

Er3+ Er3+

electronGroundlevel

Excitationlevel

photonabsorption

Er3+

non-light emissiontransient

Er3+

stimulated emissionto amplify signal

thermal equilibriumstate

Basic configuration of the EDFA

WDMcoupler

Pump LD

Er-dopedfiber

Optical isolatorOutputInput

Example of electro-optic repeater and EDFA

LD(STB)

Supervisory

LD driver(STB)

LD(ACT)

PD(Inside)

LD driver(ACT)

Erbium-doped fiber

WDM coupler Optical isolator

Pump LD

Electro-optic repeater EDFA

Technical difficulties of the lightwave undersea systems using EDFA repeater

Optical noise (ASE) accumulationChromatic dispersion of the transmission fiberNonlinearity of the transmission fiberPolarization dependent factors

� Polarization dependent loss (PDL)

� Polarization hole burning (PHB)

� Polarization mode dispersion (PMD)

Test bed of the lightwave undersea systems using EDFA repeater

OutlineHistory of lightwave undersea cable systemsOptical amplifier technologiesExamples of lightwave undersea cable networks

� TPC-5CN� APCN� FLAG� JIH

Future technologies� WDM� Optical Soliton

TPC-5CN Cable Route(Trans-Pacific Cable 5 Network)

NinomiyaJapanMiyazaki

Japan

Tumon BayGuam

KeawaulaHawaii

BandonOregon

San Louis ObispoCalifornia

APCN Cable Route(Asia-Pacific Cable Network)

MiyazakiJapan

PusanKorea

TouchengTaiwanLantau

Hong Kong

BatangasPhilippines

PetchaburiThailand

AncolIndonesia

ChangiSingapore

MersingMalaysia

FLAG Cable Route(Fiberoptic Link Around the Globe)

PorthcurnoU.K.

EsteponaSpain

PalermoItaly

Port SaidAlexandria

SuezEgypt

FujairahU.A.E.

BombayIndia

PenangMalaysia

Satun & SongkhlaThailand

LantauHong Kong

ShanghaiChina

KojeKorea

MiuraJapan

Major system parameters of OS-A system

Line bit rate 5Gbit/sSignal wavelength 1558.5nmInput signal level -20dBm to 0dBm

Repeater gain 7dB to 20dBNoise figure 5dB to 6dB

Optical amplifier Erbium doped fiberPump laser InGaAsP/InP diode

Pump wavelength around 1475nmPower feed current DC 0.92A

Reliability less than 10FIT/fiber pair

JIH Cable Route(Japan Information Highway)

To USA

To Russia

To Korea

To China

To Asiaand Europe

Major system parameters of JIH cable(tentative)

Line bit rate 100Gbit/sSignal wavelength 1530nm to 1570nm

Noise figure 5dB to 6dBOptical amplifier Erbium doped fiber

Pump laser InGaAsP/InP diodePump wavelength around 1475nm

Key technologyWavelength division multiplexing (WDM)100Gbit/s = N wavelength 10 or 5 or 2.5Gbit/s

OutlineHistory of lightwave undersea cable systemsOptical amplifier technologiesExamples of lightwave undersea cable networks

� TPC-5CN� APCN� FLAG� JIH

Future technologies� WDM� Optical Soliton

Explanation of Wavelength Division Multiplexing (WDM) technology

wavelength wavelength

Conventional systemOnly 1 signal wavelength

WDM systemMultiple signal wavelength

Transmission capacity per fiber is multiplied by the number of signal wavelength.

Technological difficulties - Signal multiplex/demultiplex - Optical amplifier bandwidth limitation - Inter-channel interaction due to optical fiber nonlinearity (so called four-wave mixing and cross-phase modulation)

Explanation of optical soliton technology

Conventional NRZ pulse(broad, pulse width = 1/bit-rate)

Optical soliton pulse(short, pulse width < 1/bit-rate)

Transmission bit-rate per signal wavelength can be expanded.

Technological difficulties - Optical short pulse generation - Inter-symbol interference (so called Gordon-Haus timing jitter)

Principle of recirculating loop experiment

Transmitter Receiver

SWON

SWOFF

SWON

SWOFF

1loop 1loop

2loops

3loops

Time

(1) Load the optical signal intothe fiber loop

(2) Optical signal runs throughthe fiber loop repeatedly

(3) Number of recirculation canbe determined by the timing

Experimental setup of 5Gbit/s, 22WDM,9500km recirculating loop experiment

.

DFB-LDs

5Gbit/sOptical

Receiver

OpticalBandpass

FilterSMF or DCFEDFA

3dBFibre

Coupler

Optical Switch

Span 1(DSF)

Span 2(DSF)

Span 3(DSF)

Rep. 2

Rep. 3

Rep. 18

Span 18(SMF)

BoosterEDFA

LN mod.

1

2

22

Sta

r C

oupl

er

Rep. 19

PolarizationScrambler1548.9nm

Optical Switch

1549.3nm

1557.3nm

if required Rep. 1

~40km

~40km~40km

~40kmLoop length = 732kmZero dispersion wavelength = 1555nmRepeater output power = +8dBm Fabry-Perot

etalon

Span 8(DSF)

Span 9(SMF)

Rep. 9~40km ~40kmSpan 17

(DSF)~40km

Snap shot of the WDM experiments

Transmission performance of 5Gbit/s, 22WDM,9500km recirculating loop experiment

.

1558155715561555155415531552155115501549154815.0

15.5

16.0

16.5

17.0

17.5

18.0

Signal Wavelength (nm)

M e a s u r e d Q - f a c t o r ( d B )

BER = 10-9

Experimental setup of 20Gbit/s, 8100km straight line optical soliton transmission

DFB-LD EA-MOD

10GHz CLOCK

Transmitter

8123km transmission line

O/E PLL

DEMUX 10Gbit/sOR

EDFA

Receiver

rep-240 rep-1DCFOBPF

10GHzCLOCK

10Gbit/sDATA

20Gbit/s

LN-MOD

10Gbit/s DATA

MUX

Q

polarisationscrambler

pulsecompressor

Q

Transmission performance of 20Gbit/s, 8100km straight line optical soliton transmission

.

10000100015

20

25

30

loopstraight

distance (km)

Q-f

acto

r (d

B)

5000

20 Gbit/s

BER = 10-9

ConclusionTechnologies of the global lightwave undersea

cable networks are reviewed.

WDM and soliton are two key technologies of future undersea cable networks.

100Gbit/s class lightwave communication system is already available under the laboratory condition, and will be available for the commercial use in early 21st century.