34 FUJITSU Sci. Tech. J.,35,1,pp.34-45(July 1999)

UDC 621.315.28:621.391.6

WDM Optical Submarine Network Systems

VMasuo Suyama VMasato Nagayama VHaruki WatanabeVHaruo Fujiwara VColin Anderson

(Manuscript received April 15, 1999)

This paper describes optical submarine network systems that support 160 Gb/scapacity (10 Gb/s ××××× 16λλλλλ) per fiber. These advanced systems enable practical and cost-effective deployment of networks with 4 fiber pair optical submarine cables, and totalcapacity of 640 Gb/s. A typical network configuration and the relevant equipment forsuch networks are outlined. The equipment includes submersible wide-band repeat-ers, optical ADM branching units and line terminal equipment, which we have developedmaking full use of our advanced optical technology. Our ultra-large capacity(10.7 Gb/s ××××× 66λλλλλ) transmission experiment, and enabling technologies for futureTera-bit transmission systems are also summarized. New network configurations usingOADM or Internet Protocol (IP) routers are proposed for next generation WDM subma-rine networks.

1. IntroductionWe have already developed and supplied sub-

marine WDM systems for projects such as theSEA-ME-WE 3 cable system, which features 40Gb/s capacity (2.5 Gb/s 8λ 2 fiber pairs). Dueprimarily to the explosive expansion of Internetuse, demand for international traffic is currentlygrowing at a high rate, and capacities per fiberpair of 10 Gb/s 16 or more are now required. Inorder to meet this demand, we have developed thesystems outlined in this paper.

2. Overview of 640 Gb/s submarinenetwork utilizing 10 Gb/s ××××× 16λλλλλ WDMTable 1 summarizes major parameters of 640

Gb/s (10 Gb/s 16λ 4 fiber pair) system. The sys-tem features the following technical advantages:• Minimized system cost

Forward Error Correction (FEC) has beenemployed, using the Reed Solomon 255/239code, in order to improve system performance.We have developed dedicated IC chip sets for

this FEC using the Reed Solomon code (255/239) at data rates of 10 Gb/s (SDH STM-64),based on advanced hardware and softwaretechnology. This FEC, together with the in-creased output power and lower noise figureof the submersible repeaters, has enabled usto minimize the number of repeaters requiredfor the system, thus minimizing the cost.

• Wide optical gain bandwidthAn optical gain bandwidth of at least 12 nmis required for the 16λ system with channelspacing of 0.8 nm. This is almost twice thebandwidth required for the previous 8λ sys-tems. We realized the required broad gainbandwidth by employing an Erbium DopedFiber (EDF) with optimized dopant concen-trations, and a fiber-based gain equalizeroptimized to compensate for the EDF gaincharacteristic.

• Enhanced supervisory functionsMonitoring the status of each repeater in thenetwork is important for the maintenance of

35FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

Capacity per fiber

Bit rate per channel

Modulation scheme

Signal wavelength

Forward error correction

Maximum system length 10000 km for one hop between SLTE and SLTE

Repeater span 40 km ~ 90 km depends upon total hop length

Optical fiber type NZ-DSF + DCForLCF + DCF

NZ-DSF: Non Zero Dispersion Shifted FiberLCF: Large Core FiberDCF: Dispersion Compensating Fiber

Item

equivalent to 1935360 telephony voice channels

Note

STM-64 16

10.664 Gb/s

Return to Zero (RZ) code

1548 nm ~ 1560 nm

Reliability

Error performamce After error correction

System life = 25 years

Repeater supervisory

less than 2 ship repairs

Line powering current DC1A

BER < 1 10-11

• Input power• Output power• Pump laser diode bias• C-OTDR

Reed Solomon code(255/239) FEC

Parameter

Table 1Major parameters of 640 Gb/s (10 Gb/s ××××× 16λλλλλ ××××× 4 fiber pair) system.

SIESIE

SIESIE

SLTE

CTB PFE

PFE

SLTE

CTB

SSENME

SIESIE

SIESIE

SLTE

CTB PFE

PFE

SLTE CTB

SSENME

REP

SIESIE

SIESIE

SLTE

CTBPFE

PFE

SLTE

CTB

SSENME

PFE

PFESSENME

Station A

Station D

REP REP

REP

Station B

REP

Station C

SIESIE

SIE

PFE

SSENME

Station E

BU

BUCTBNMEPFEREPSIESLTESSE

::::::::

Branching UnitCable Termination BoxNetwork Management EquipmentPower Feeding EquipmentSubmarine REPeaterSDH Interconnection EquipmentSubmarine Line Terminating EquipmentSystem Supervisory Equipment

SLTE

CTB

SIE

CTB SIE

SIESIE

SIE

SLTE

SLTE

CTB

Figure 1Example network configuration.

36 FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

large capacity submarine networks. Our su-pervisory system monitors and reportsrepeater status including parameters suchas optical input power and output power, aswell as pump-laser power and bias current.In addition, a coherent OTDR path is pro-vided in each repeater, enabling preciseremote fault localization as far as 10000 kmfrom the terminal equipment.

Figure 1 is an example network configura-tion. An overview of the network function of eachtype of equipment is given below. A more detaileddescription of some of the equipment includingrepeaters, OADM and SLTE follows in subsequentsections.

2.1 Submarine line terminalequipment (SLTE)The submarine line terminal equipment

(SLTE) provides the necessary interface betweenthe 9.95 Gb/s signal from the SDH Interconnec-tion multiplex Equipment (SIE) and the 10.66 Gb/ssignal (including the FEC overhead), as well asthe wavelength division multiplex and de-multi-plex functions in optical domain.

2.2 WDM submarine repeater (REP)WDM submarine repeaters are essential to

realize long-distance high-capacity optical fibersubmarine transmissions. The repeater span istypically 40 to 90 km depending on total systemlength. The repeater includes wide-band opticalamplifiers equipped with a gain-flattening filter.Typical repeaters are designed for two, three orfour fiber pair submarine cable. A repeater for afour fiber pair submarine cable includes 8 EDFoptical amplifiers, which are powered by DCcurrent from the PFE, fed through the center con-ductor of the submarine cable.

2.3 Submarine optical branching unit(BU)Submersible optical branching units provide

for some fiber pairs to terrestrial terminal sta-tions, while passing the other fibers through.Optical Add/Drop Multiplexing BU can add/dropparticular wavelengths in one fiber pair.

2.4 Power feeding equipment (PFE)The PFE equipment provides power to the

repeaters by applying a DC current of typically1.0 amp through the center conductor of the sub-marine cable.

2.5 System supervisory equipment(SSE)The SSE is an element manager which per-

forms all necessary submarine system supervisoryfunctions including the element management forthe SLTE, the PFE and the repeaters. Surveil-lance and control of submarine repeaters isachieved by modulation of the main opticalsignal applied at each SLTE.

2.6 Network management equipment(NME)The SSE and the SIE element manager

communicate to the overall Network ManagementEquipment (NME), which is comprised of dedicat-ed software running on a UNIX workstation. ThisNME has the possibility to up-link to other high-er network management systems by the ITU-TQ3 protocol.

2.7 Cable termination box (CTB)The CTB facilitates the connection between

the optical fibers of the submarine cable and theoptical patch cables to the station ODF (opticaldistribution frame), as well as providing the in-terface to the center DC power-feed conductor ofthe submarine cable. Submarine cables with upto 4 fiber pairs (8 optical fibers) per cable are typ-ically deployed.

2.8 Network protection & SDHinterconnection equipment (SIE)The SDH SIE equipment allows application

37FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

of the 4-Fiber MS-SPRing (Multiplex SectionShared Protection Ring) protection scheme to N 10 Gb/s submarine networks, and includes thespecial requirements for trans-oceanic submarinenetworks. In addition, the SIE allows full accessto the protection channel (PCA) for un-protectedtraffic (which may be lost in case the protectionscheme acts to protect the main traffic in event ofa cable or hardware failure).

3. Equipment for 10 Gb/s ××××× 16λλλλλ WDMsubmarine linksThis chapter describes details of the equip-

ment developed specifically for 10 Gb/s 16λλλλλsubmarine networks. The equipment includes theWDM submarine repeater, the OADM branchingunit (BU) and the WDM submarine line terminalequipment (SLTE).

3.1 WDM submarine repeaterFigure 2 shows the block diagram of the

repeater for one sub-system (one fiber pair).Table 2 shows the major parameters of the wide-band WDM repeater.

3.1.1 Repeater configurationA length of optical fibre, whose core is doped

with the rare earth element Erbium, provides op-tical amplification. Optical energy is supplied tothe Erbium doped fibre (EDF) by pump laser di-odes (LD) operating at a wavelength of 1.48 µm,which excites the Erbium ions to a higher energy

level and provides optical gain. Since the gaindepends on the wavelength of an input signal, theEDF limits the transmission wavelength window.A long-period fiber grating (LPG) with an appro-priate loss characteristic is employed to compen-sate for the gain profile of EDF. Furthermore, ahigh concentration of aluminium is co-doped inthe EDF core, which contributes to a flattened gainprofile.1) Thus, a wide gain bandwidth (12 nm)was achieved, making it suitable for transmissionof 16 wavelengths.

Pump LD’s are duplicated, and supply theEDF’s for both transmit and receive via a coupler(CPL5). Passive wavelength division multiplex-ing couplers (WDM) are used to combine the inputline signals at around 1.55 µm with the pumplaser signal at 1.48 µm. Dielectric filter technolo-gy was chosen for the WDM coupler, in order toachieve a flat pass-band characteristic. An opti-cal isolator (ISO) was designed to ensure very lowlevels of polarization dependent loss (PDL) andpolarization mode dispersion (PMD) in the repeat-er. The WDM filter and isolator were integratedinto compact module by making full use of ourmicro-optics technology.

3.1.2 Repeater supervisory systemIt is a requirement of the system to be able

to locate faults to within one repeater section. Allhardware faults involving the loss of transmissioncan be located using the input and output moni-tors of the repeater.

Input 1

Output 2 Input 2

Output 1CPL1 CPL2

CPL4 CPL3

CPL5

EDF1

EDF2

WDM1 ISO1

ISO2 WDM2

PD4 PD3

PD1 PD2

LD1

LPG1

LPG2

LD2

Figure 2Configuration of wide-band WDM repeater (sub-systemfor one fiber pair).

Optical output power

Noise figure

Transmission window(optical bandwidth)

Remote supervision

Operating temperature range

System design Iifetime

+10 dBm

< 6 dB

Parameter

> 12 nm

Optical input power monitorOptical output power monitorPump laser drive current monitor

0°C to +35°C

25 years

Value

Table 2Major parameters of wideband WDM repeater.

38 FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

Monitoring of the input and output opticalsignal level is achieved by using photo diodes (PD)and couplers (CPL). The pump laser diodes’ con-dition can be monitored by remotely monitoringtheir drive current.

3.2 Optical add/drop submarinebranching unitAn Optical ADM branching unit (OADM-BU)

was developed, which can add or drop any wave-lengths to or from the main trunk WDM signal.Figure 3 shows the optical circuit diagram of theOADM-BU. It utilizes fiber Bragg gratings, opti-cal circulators and an optical isolator. The fibergrating reflects the specified wavelength, andtransmits other wavelengths. The required opti-cal add/drop function is achieved by the combina-tion of the fiber grating and the optical circulatoras shown in Figure 3. The fiber grating is incor-porated into a temperature-compensated package

Operating temperature range

Signal wavelength

Insertion loss

Insertion loss between "Through"wavelength and "Add/Drop" wavelength

Return loss

PDL

0°C to +35°C

1550 nm to 1560 nm

Parameter

"In" to "Out": 5.8 dB"In" to "Drop": 4.0 dB"Add" to "Out": 4.0 dB

> 36 dB

> 35 dB

< 0.3 dB

Typical value

Table 3Major parameters of optical ADM branching unit.

1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 15604540

35

30

25

20

15

10

50

Wavelength (nm)

Loss

(dB

)

(a) "In" to "Out" characteristic

1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 15604540

35

30

25

20

15

10

50

Wavelength (nm)

Loss

(dB

)

(b) "In" to "Drop" characteristic

dropλ

Figure 4Example characteristics of optical ADM branching unit(Two wavelengths Add and Drop).

in order to eliminate any shift of the center wave-length due to temperature variations. A perfectcirculated 3-port optical circulator is used in or-der to still enable fault localization from theremote terminals, using coherent optical time do-main reflectometry (OTDR). The optical isolatoris used to suppress coherent cross-talk, whichmight otherwise degrade the transmission perfor-mance.

Table 3 summarizes the major parametersof the OADM-BU. Figure 4 shows a typical char-acteristic of the OADM-BU. It can be seen thatgood in-band amplitude flatness and sharp rejec-tion characteristics were achieved.

3.3 WDM submarine line terminalequipment (SLTE) for 10 Gb/s ××××× 16λλλλλThe 10 Gb/s 16λ WDM SLTE is high-speed

transmission equipment used for transporting a

Opticalcirculator

INλl ~ λn

DROPλdrop

Note: λdrop = λadd

ADDλadd

OUTλl ~ λn

Opticalisolator

Fibergrating

Fibergrating

Opticalcirculator

Figure 3Optical circuit diagram of optical ADM branching unit.

39FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

maximum of sixteen STM-64 signals. Figures 5and 6 are block diagrams of main transmissionpath of the 10 Gb/s 16λ WDM SLTE. To estab-lish higher transmission performance, ReedSolomon (255/239) Forward Error Correction(FEC) is implemented in the transmission signalfor each wavelength. Thus, the STM-64 signal isconverted to a 10.66 Gb/s signal before being mul-tiplexed into WDM optical line signal and

transmitted to the far end via the submarine re-peaters. The received optical line signal isde-multiplexed to each wavelength signal by theSLTE, and then converted to an electrical signal.The functions of the SLTE are as follows:1) Conversion between the 9953.28 Mb/s

(STM-64) SDH data signal and the subma-rine line signal (10664.22857 Mb/s includingthe FEC processing)

STM-64TRIB (λ1) subrack WDM-S rack

AWG AMP

AMP

AMP To Line

CPL

AMP

AMP

AWG

AWG

AWG

DCF subrack WDM-S rack

TRIB (λ13) subrack

TRIB (λ16) subrack

Same as TRIB (λ1) subrack

Same as TRIB (λ1) subrack

λ1

λ4

λ5

λ9

λ12

λ13

λ16

λ8

O/E

TX&LDunits E/O

FEC-S NRZ/RZ1

13

16

Figure 5SLTE block diagram (transmit side).

STM-64

1

13

16

TRIB (λ1) subrack

TRIB (λ13) subrack

TRIB (λ16) subrack

Same as TRIB (λ1) subrack

Same as TRIB (λ1) subrack

λ1

λ4

λ5

λ8

λ9

λ12

λ13

λ16

DCF subrack WDM-R rack

AWG

AWG

CPLAMP From Line

AWG

AWG

E/O

RXunit

O/E

FEC-R

Figure 6SLTE block diagram (receive side).

40 FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

2) Optical amplification of the transmit andreceive signals

3) Wavelength division multiplexing and de-multiplexing of the signal

4) Dispersion compensation using dispersioncompensating fiber, for both transmit andreceive

5) Monitoring and displaying of relevant alarms6) Provision of line supervisory interface.

In the transmit side of the SLTE, theSTM-64 SDH signal is converted to an electricalsignal, and is multiplexed with redundant bits forFEC, thus producing the 10.66 Gb/s signal. Thisis converted to an optical signal with appropriatewavelength in TRIB sub-rack of the SLTE. Amaximum 16 channels are multiplexed into oneoptical line signal using the arrayed waveguidegrating (AWG) and CPL blocks in the WDM-S rackof the SLTE.

In the receive side of the SLTE, the line sig-nal is amplified and de-multiplexed into separatewavelength signals in WDM-R rack. After decod-ing the FEC bits, each signal is converted to anSTM-64 SDH signal in the TRIB sub-rack of theSLTE.

In order to minimize waveform distortion dueto chromatic dispersion, dispersion compensationat both transmit and receive side is necessary.2)

The necessary dispersion compensating fibers(DCF) to accomplish this are accommodated in theDCF sub-rack of the SLTE.

Overhead bytes in the FEC frame are alsoused for provision auxiliary plesiochronous datachannels (2.048 Mb/s), 64 kb/s data channels, andvoice channels for engineering orderwire.

The SLTE equipment also performs surveil-lance and control of submarine repeater and hasthe alarm and supervisory capability. This equip-ment has a display interface to indicate relevantalarms and status, which involves receiving andsending data from or to the System SupervisoryEquipment (SSE).

3.4 Current network protectionarchitecturesSDH MS-SPRing network protection config-

uration (similar to the BLSR (Bi-directional LineSwitched Ring) configuration in SONET net-works) is currently the most attractive for largehigh-capacity submarine networks. MS-SPRingis already widely used in terrestrial networks, andis preferred over unidirectional Path SwitchedRing protection schemes, since it allows the re-use of circuit capacity on a node-to-node basis andaccess to the protection channel is possible withappropriate SIE equipment. Some specific adap-tations to the usual MS-SPRing protocol arerequired for submarine network applications, toprevent hairpin protection over trans-oceanicroutes. The SDH protection scheme is providedby the SIE equipment.

4. Technologies for future submarinenetwork systemsTo meet the increasing demand for network

capacity, which is mainly driven by the growth inInternet services, new and advanced technologiesare required for end-to-end transmission capaci-ty and also for network protection architecture.This chapter discusses some of the enabling tech-nologies for Tera-bit transmission and futurenetwork configurations.

4.1 Enabling technologies for tera-bittransmission in real networksMajor limiting factors for the realization of

Tera-bit transmission include SNR degradation,gain bandwidth, and waveform distortion due tochromatic dispersion and non-linear optical ef-fects. Various technologies seem to hold promisein addressing these limitations:• Improved SNR achieved by using lower noise

repeaters, such as achieved by utilizing 980nm pump lasers

• Broad bandwidth achieved by accurate gainequalization and by exploiting L-band EDFAoptical amplifiers

41FUJITSU Sci. Tech. J.,35, 1,(July 1999)

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• Reduced power density and chromatic disper-sion compensation achieved by utilizing newtypes of optical fiber.

We have already successfully demonstratedtransmission of 10.7 Gb/s 66λ (= 0.7 Tb/s) over2212 km by employing some of the above technol-

ogies.3) Figure 7 shows the configuration of therelevant transmission experiment. The noise fig-ure of the optical amplifiers was as low as 4.9 dBwith +13 dBm output power, which was realizedby efficient pumping at 1.48 µm using a pump re-flector. We compensated for the asymmetric gainprofile by using GEQs with different free spectral

1535 1545 1555 1565

Wavelength (nm)

Rel

ativ

e in

tens

ity(1

0 dB

/div

)

26 nm

Figure 8Optical spectrum after 2212 km.

Transmitter (1537.1 nm to 1563.1 nm)

8GEQ

Receiver

Odd ch. LDs

Even ch. LDs

IM

IMCPL

SW

SW

FilterPost-DCF

OR

3-dB CPL

5 4 3 GEQ 2 1

6 7 9 GEQ 10

11121314 GEQ15

16 GEQ17 18 19

ASE cut FG DSF 50 km

DCF 25 km

ASE cutFG

DSF 25 km

DSF 25 km

DCF10 km

DCF50 km

ASE cutFG

ASE cutFG

Pre-DCF

Loop length : 737.6 km

Figure 7Experiment setup.

1 17 33 49 6610

12

14

16

18 18

20

22

OSNRs

Q-factors

1.1 dB

5 dBBER = 10-9 without FEC

BER = 10-11 with FEC

Channel

Q-f

acto

r (d

B)

OS

NR

(dB

)

Figure 9Transmission performance (Optical SNR and Q factor).

42 FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

ranges, resulting in a bandwidth of 26 nm aftertransmission over 2212 km (Figure 8). A goodtransmission performance was confirmed in termsof optical SNR and Q factor (Figure 9).

These technologies combined with the newoptical fiber featuring large effective area, and dis-persion compensation up to the third order,4) willenable the practical realization of Tera-bit trans-mission in networks over transoceanic distances.

4.2 Future high capacity networkarchitecturesTelecommunication backbone networks will

in the near future evolve into data networks whichaccommodate voice, video, IP and other telecom-munications services. A submarine networksystem which can satisfy the requirements of thisevolution, and also features more economical andflexible configuration is described.

4.2.1 Network configurationsusing OADM and OPSW

Figure 10 shows a ring-configuration sub-marine network configuration using an OpticalAdd / Drop Multiplexer (OADM) at the terminals.The OADM can add or drop and pass through anydesired wavelength signals in optical layer, by us-ing appropriate optical filters. The OADM sendsthe wavelength multiplexed signal on to the SLTE.For protection against possible line or equipmentfailure, the optical protection switch (OPSW) withTransoceanic Ring Protection mode, is supportedin this configuration.

The special features in this configuration areas follows:1) Transparency to any digital hierarchy2) High reliability by using the OPSW3) Add/Drop and Through any wavelength in

the optical layer4) Effective use of the wavelength in the ring

network.

This configuration can exclusively assignwavelengths for various telecommunicationservices and signals in the optical layer. In addi-

tion, an Optical ADM developed for use in terres-trial networks can easily be deployed in submarinenetworks using this configuration.

4.2.2 Network configurationsusing OPSW without OADM

In case of the fixed connection of the wave-lengths in the optical layer, it is possible to connectthe OPSW to the SLTE directly, without using theOADM (Figure 11). This configuration allows thedeployment of systems at a lower cost, while stillmaintaining the high network reliability offeredby the OPSW.

4.2.3 Network configurationsusing an IP router

Recently, telecommunication services usingInternet protocol (IP) are developing very quick-ly. It is now important to apply the IP technologyto the submarine cable networks, as the interna-tional backbone network also shifts towards anIP based network. Figure 12 shows a possiblenetwork configuration using IP routers, where ahigh capacity IP router is connected directly tothe SLTE. In the event of a network failure, traf-fic can be restored by the routing protocol of theIP router. The system has the following features:1) Efficient transportation of IP traffic2) Lower cost for network equipment3) Easy integration with other networks using

IP protocols4) Simplified network architecture and protection5) The possibility to protect the network using

the routing protocol.

Therefore, this configuration seems promis-ing for future submarine networks.

5. ConclusionsWe have described a practical and cost-effec-

tive 640 Gb/s (10 Gb/s 16λ 4 fiber pair) opticalsubmarine network system, together with the net-work configuration and relevant equipment. Inparticular, the new submersible wide-bandwidthoptical repeater, optical ADM branching unit, andsubmarine line terminal equipment were detailed.

43FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

SLTE

Through

Fixed wirning

: Working: Protection

Add

Drop

Through

Through

SLTE

SLTE

SLTE

OPSWλλ

Figure 11Connection configuration between SLTE and OPSW.

SLTE

CTB PFE

PFE

SLTE

SSENME

SLTE

CTB PFE

PFE

SLTE

SSENME

REP

SLTE

SLTE

SSENME

SLTE

CTBPFE

PFE

SLTE

SSENME

Station A

Station D

REP REP

REPStation B

REP

Station C

SLTE

CTB PFE

SSENME

Station E

BU

OADM/ PSW C

TB

OADM/ PSW C

TB

CT

B OADM/ PSW

OADM/ PSW

PFE

CT

B

CTBPFE

OADM/ PSW

SLTE

SLTE

SLTE

SLTE

OADM

O-Filter

O-Filter

O-Filter

O-Filter

O-Filter

O-Filter

WORKING

PROTECTION

OPSW

λ λ

O-Filter : Optical Filter

BUCTBNMEOADMPFEPSWREPSLTE

::::::::

Branching UnitCable Termination BoxNetwork Management EquipmentOptical Add Drop MultiplexerPower Feeding EquipmentProtection SwitchSubmarine REPeaterSubmarine Line Terminating Equipment

Figure 10Ring submarine network configuration using OADM.

44 FUJITSU Sci. Tech. J.,35, 1,(July 1999)

M. Suyama et al.: WDM Optical Submarine Network Systems

Enabling technologies for future Tera-bit trans-mission networks were discussed, referring to our0.7 Tb/s (10.7 Gb/s 16 66λ) transmissionexperiment, and new network configurationsusing OADM or IP routers were proposed for next-generation of WDM submarine networks.

References1) T. Naito, N. Shimojo, T. Terahara, T. Tanaka,

T. Chikama, and M. Suyama: Long-haulWDM transmission system by use of highAluminum codoped EDFAs and gain-equal-izers. GLOBECOM’98, Sydney, pp.993-997,November, 1998.

2) T. Naito, T. Terahara, T. Chikama, and M.Suyama: Four 5-Gb/s WDM transmission

over 4,760 km straight line using pre- andpost-dispersion compensation and FWMcross talk reduction. OFC’96, San Jose, WM3,February, 1996.

3) T. Terahara, T. Naito, N. Shimojo, T. Tanaka,T. Chikama, and M. Suyama: 0.7 Tbit/s (66 10.66 Gbit/s) WDM transmission over 2,212km using broadband, high-power EDFAswith pump reflector. Electron. Lett. 34, 10,pp.1001-1002 (May 1998).

4) M. Murakami, H. Maeda, and T. Imai: Long-haul 16 10 WDM transmission experimentusing higher order fiber dispersion manage-ment technique. ECOC’98, Madrid, TuC28,September, 1998.

SLTE

CTB PFE

PFE

SLTE

SSENME

SLTE

CTB PFE

PFE

SLTE

SSENME

REP

SLTE

SLTE

SSENME

SLTE

CTBPFE

PFE

SLTE

SSENME

Station A

Station D

REP REP

REPStation B

REP

Station C

SLTE

CTB PFE

SSENME

Station E

BU

BUCTBNMEPFEREPROUTERSLTESSE

::::::::

Branching UnitCable Termination BoxNetwork Management EquipmentPower Feeding EquipmentSubmarine REPeaterIP ROUTERSubmarine Line Terminating EquipmentSystem Superviously Equipment

ROUTER

CT

B

ROUTER CT

B

CT

B ROUTER

ROUTER

PFE

CT

B

CTBPFE

ROUTER

Figure 12Ring submarine network configuration using the IP Router.

45FUJITSU Sci. Tech. J.,35, 1,(July 1999)

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Colin Anderson received a B.Sc.degree, majoring in Physics fromVictoria University, Wellington, NewZealand in 1975. In 1988 he receivedan MBA degree from the Victoria Uni-versity Graduate School of Businessand Government. After 12 years withPhilips NZ Ltd., in both engineering andmarketing roles, he joined Fujitsu NZLtd. in 1986. In 1992 he moved to TokyoJapan, to take up a position in the Inter-

national Telecommunications Business Group of Fujitsu Limit-ed. He is currently Business Development Manager for SubmarineNetworks Sales & Marketing in the International Telecommuni-cations Business Group. He is a member of the IEEE Commu-nications Society.

Masuo Suyama received B.E. and M.E.degrees in Applied Physics from theUniversity of Tokyo, Tokyo, Japan, in1980 and 1982, respectively. He joinedFujitsu Laboratories Ltd., Kawasaki in1983 and was engaged in research anddevelopment of optical amplifiers andtheir system applications. Since 1994,he has been with submarine telecom-munications division of Fujitsu Ltd.,working on system design. He is a mem-

ber of the Institute of Electronics, Information and Communica-tion Engineers (IEICE) of Japan.

Haruo Fujiwara received B.S. and M.S.degrees in Electrical Engineering fromOsaka University, Osaka, Japan in 1973and 1975, respectively. He joinedFujitsu Laboratories Ltd., Kawasaki in1975 and transferred to Fujitsu Ltd. in1985. He has been engaged in thedevelopment of optical submarine re-peaters and branching units. He is amember of the Institute of Electronics,Information and Communication Engi-

neers (IEICE) of Japan.

Haruki Watanabe received B.E. andM.E. degrees in Electronics Engineer-ing from Nihon University, Tokyo, Japanin 1980 and 1982, respectively. Hejoined Fujitsu Ltd., Kawasaki in 1982,where he was engaged in research anddevelopment of submarine line terminalequipment. He joined Fujitsu KyushuDigital Technology Ltd., Fukuoka in1999. He is a member of the Instituteof Electronics, Information and Commu-

nication Engineers (IEICE) of Japan.

Masato Nagayama received a B.E. de-gree in Electrical Engineering from theScience University of Tokyo, Tokyo,Japan in 1989. He joined Fujitsu Ltd.,Kawasaki, in 1989 and has been en-gaged in the research and developmentof data communication network sys-tems for 9 years. Since 1998 he hasbeen engaged in the research and de-velopment of submarine cable networksystems.