COMMERCIAL–IN-CONFIDENCE Submarine Cable System Functions & Repair.

COMMERCIAL–IN-CONFIDENCECOMMERCIAL–IN-CONFIDENCE

Submarine Cable SystemFunctions & Repair

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IP Cloud


World Submarine NW Map


DWDM

WDM (Wavelength Division Multiplexing), it uses different wavelengths on the same fibre & is totally protocol independent (SDH, ATM, Ethernet…)

It is known as Dense Wavelength Division Multiplex (DWDM) when the wavelengths are close (a few nm.)For a DWDM Transmission system, 40/80 or at present 160 or more wavelengths in Optical C-Band (1530nm to 1565nm wavelength spectrum) can be carried on one fibre.


Why DWDM

a) Overcome fiber exhaust / lack of fiber availability problems (better utilization of available fiber)

d) Cost effective transmission

e) No O-E-O conversion delays

f) Wave length leasing instead of Bandwidth leasing

b) Space and Power savings at intermediate stations

c) Easier capacity expansion


Evolution of Submarine Transmission Technology

SDH & DWDM combined

SDH and DWDM are complementary.

SDH provides:• flexibility• resilience in case of failure

DWDM provides:• very high bandwidth

So For higher bandwidth transmission over a longer distance on the International network across continents/countries, SDH & DWDM combinely evolves to Submarine Transmission network


Submarine Fiber Optic Network system

Fully integrated Undersea SystemUsing with -

CablesRepeatersBranching UnitsTerminal Equipment

SLTE, PFE, LME, NMS and DCN

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What makes a Submarine Cable Network

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Cablestation

TerminalEquipment

Cable RepeaterPower FeedingEquipment

Branching unit

Network Management


Undersea Cables


Double Armoured Cable – For Deep & Rocky Seabed for double protection


Functions of Submarine Network


Functions & Terminologies


Submarine Wetplant & components

Wet plant comprises the following equipment/components:

Undersea Cable Land Cable Optical Fiber Cable joints Undersea Repeaters Gain equalizers Branching Units


Major Components of Submarine system

WTE+

TLA

LME

N Channels

PFEOGPP

TRPDR l 1

TRPDR l 2

TRPDR l 3STM-16/ STM-64Ÿ

ŸŸ

RL Cable

HV Power

BuildingGround

OceanGround

Ground

BeachJoint

SL-17Undersea

Cable

TRPDR l n

Cable Station

LTE #1

CTE

TRPDR Transponder

HV : High Voltage

LME : Line Monitoring Equipment

OGPP : Ocean Ground Protection Panel

PFE : Power Feed Equipment

RL : Rodent Lightning

TLA : Terminal Line Amplifier

WTE: Wavelength Termination Equipment

PLINB

HV ShieldUnderseaRepeater

Full Fiber DropBranching Unit

N Channels

TRPDR l 1

TRPDR l 2

TRPDR l 3

ŸŸŸ

TRPDR l n

LTE #2

ADM

STM-16/ STM-64

ADM

COTDR

NMS

SLTE & Wetplant

NMS


Submarine Transmission Line Terminating Equipment

15

(optional) ILE

Line Monitoring Wavelengths(only for repeatered systems)Line Monitoring Wavelengths(only for repeatered systems)

10 Gbps (S-64.2) Interface

IP

OXC

ADMADM

ATM

WTEl1

l2

lN-1

lN

11

TRPDR

22

N-1N-1

NN

Note: Any module of the LTE may not be included depending on the specificrequirements of the system (distance, bit rate, SDH or SONET equipment, etc.)

Line Amp

Submarine Cable

OneFiber-Pair

N x 10Gbps


UnderSea Repeaters

Repeaters use state-of-the-art optical amplifier technology to achieve high performance and reliability in the transmission of multiple wavelength channel signals on multiple fiber pairs which normally use 980nm Pump for boosting up optical signal


Inside Repeater & different types

Amplifier Pair Chassis

Pump UnitControl Circuit

Erbium Amplifiers

Supervisory

Heat Transfer Plate

Locking Plate

Power Supply

1/2/3/4 up-to 8 Amplifier pairs per Repeater Low/High Gain Repeaters. Low noise & Wide BW Repeaters 980 nm Pumps used in Repeaters.


Gain Equalisers

Gain Equalizer function is needed for every 5-10 spans depending on the total length of system. It is required because of non-flat nature of EDFA amplifier to compensate the gain which results with wider range of wavelength for traffic.


Branching Unit

Branching units (BUs) are designed for use in systems having three or more landing sites. Optical signals are routed among the three cables that connect to the BUs.There are different types of BU’s. These BU can be controlled for electrical connections relay from the landing station SLTE equipment using commands on the same Optical channel.


Types of BU

1. Passive BU – The Electrical connections/branches can’t be switched or controlled from Station & it is electrically passive & doesn’t consume any electrical power. Also it is optically passive, means no Adding/Dropping of Wavelengths among three legs.

2. Power Switched BU – This type BU provides controllable electrical connections among the three cable legs, as well as to the sea-ground electrode built into the trunk leg cable termination. The electrical connectivity within the 34A-Type BU is controlled

on a powered system by means of an optical command signal & it will have a command receiver.

3. Power Switched OADM BU – It is similar to Power switched BU, but having optical add/drop functionality using a OADM inside the BU, which makes it optically & electrically controllable among three legs.

4. Non-power switched BU – It is similar to Passive BU, but having OADM functionality.


PFE

Under Sea Repeaters requires power for operation of Electronics circuit & the Power Feed Equipment (PFE) provides power to the these repeaters & Power switched BU.

These PFEs supply the power to undersea equipment in redundant arrangements called as dual end feed, for continuous operation even in the event of one PFE converter failure.

Different types of PFE from all SubSea suppliers available, depending on the power supply capability to feed the system, like 10Kv, 5Kv etc.


PFE – Submarine System powering overview

Example of a Trunk Point to Point Powering System

PSBU 1 PSBU 2

Example of a Normal Powering scenario for a Trunk and Branch Configuration

Current

Station A

PFE+

Station B

PFE-

Station A

PFE+

Station B

PFE-

Station C

PFE-

Station D

PFE-

Current

Virtual Ground


Fault Isolation & Repair in Wetplant

4 Detection and localization of Subsea faults

Two categories - Optical - Electrical

Electrical and optical faults can occur simultaneously (cable break) and separately (damaged or broken fibers with the power path intact, and insulation fault between the power path and the sea, commonly known as shunt fault, with fibers intact.


Types of SubSea Fault

Type 1 fault - Cable break for the cable being cut, with a break in the electrical insulation between seawater and the power-feeding conductor.

Type 2 fault - Open fault for the cable being cut, without breaking the electrical insulation between seawater and the power-feeding conductor. Type 3 fault - Shunt fault for a break in the electrical insulation between seawater and the power-feeding conductor, without this conductor itself been cut.

Type 4 fault - damage in the optical path without significant electrical alteration of the power-feeding conductor continuity and insulation.

Fiber

HV conductorOuter Cable

Outer Cable


Fault Localization techniques

Single-end DC measurements Type 1- Cable Break Type 3 – Shunt Fault Only accurate if you precisely remove contribution of repeaters and fault. Capacitive Method Type 2 - Open fault Conjugate Method (current-balance) Type 3 – Shunt Fault Accurate but also requires removal of contribution of the repeaters.

Optical Path (OTDR/COTDR) Type 4 - Optical Fault only OTDR only good to first repeater.

Electrical Path fault - Power Feed (output variation/ohms law) - PEFL (impedance mismatch) - DC Testing (IR, IC and CR) - Electroding (detection of a magnetic field due to applied tone)


Optical Fault Localization

Optical Time Domain Reflectometer - also known as an OTDR, is a hardware device used for measurement of the elapsed time and intensity of light reflected on optical fiber.How it works?The reflectometer can compute the distance to problems on the fiber such as attenuation and breaks, making it a useful tool in optical network troubleshooting.The intensity of the return pulses is measured and integrated as a function of time, and is plotted as a function of fiber length.

What is a COTDR?Coherent Optical Time Domain Reflectometer - also known as a COTDR, An instrument that is used to perform out of service backscattered light measurements on optically amplified line systems.How it works?

What is a OTDR?

A fiber pair is tested by launching a test signal into the out going fiber and receiving the scattered light on the in-coming fiber. Light scattered in the transmission fiber is coupled to the incoming fiber in the loop-back couplers in each amplifier pair in a repeater.


OTDR Vs COTDR

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Light Pulse

OTDR

Repeater

HLLB

Repeater

HLLB

Repeater

HLLBBackscatter

Light Pulse

COTDR

Repeater

HLLB

Repeater

HLLB

Repeater

HLLB

Backscatter

OTDR can only measure up-to first repeater

OTDR can cross the repeaters & can measure till opposite end terminal


COTDR Measurement plot


Electrical path Fault Localization

29

Subsea cable Electrical path fault (Shunt Fault) localization is a manual process & no automatic measuring equipment/testers are available. This requires tedious calculations from PFE voltage & cable properties, before & after fault occurs. Below are some of the techniques used for this.

1. Power Feed (output variation/ohms law) – Using the simple ohms law formula for voltage/Impedance calculation, approx. fault location to be calculated. This is called power budget calculation.

Total PFE voltage(Segment voltage) = Cable voltage drop + BU drop + Repeater drop + earth resistance

2. PEFL (impedance mismatch)

3. DC Testing (IR, IC and CR) – This is normally done from cable repair ship for checking the cable continuity & post repair checks.

4. Electroding (detection of a magnetic field due to applied tone) from Terminal PFE.


Electroding

XElectroding Signal Low frequency A.C tone 4Hz to 50Hz

Fault Detected at Tone leakage point

Electroding is used for different purpose.1. To identify the exact location of fault in a suspected span,

either shunt or cable break from ship.2. To identify & pickup the exact cable system, out of many

cables laid on Seabed, during a repair activity from ship.

Electroding technique is sending low-frequency AC tone from Terminal PFE, using the capabilities of the PFE coupled & with special detection equipmenthaving low-current dc and low-frequency resistance and capacitance measurements which can be used in repair ship to find out the exact fault.


Subsea Cable repair

•The damaged Under Sea part of cable is repaired by specially equipped cable ships•A number of Cable ships are strategically located in different regions•Damaged portion of the cable will be lifted and removed by the cable ship and join again with a new piece of cable•The operation will take usually 10-15 days depending upon the distance of cable fault, Nature of the fault, spare availability in the ship and weather conditions.

ASN Cable Repairing.exe


A Shunt Fault

Shunt Fault –Single end Feed, Service affecting

Shunt Fault –Dual end PFE Feed, Not Service affecting


Cable Joints

Cable joints connect similar types of cable on land and at sea during initial cable laying & during a repair operation.

Sea Cable Joints


Sub Marine cable System visual tour

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Sub Marine cable system Video


CABLES AROUND AFRICA

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COMMERCIAL–IN-CONFIDENCE Submarine Cable System Functions & Repair.

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Transcript of COMMERCIAL–IN-CONFIDENCE Submarine Cable System Functions & Repair.