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Submarine Cable System
Functions & Repair
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IP Cloud
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World Submarine NW Map
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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.
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Why DWDM
a) Overcome fiber exhaust / lack of fiber availability
problems (better utilization of available fiber)
b) Space and Power savings at intermediate stations
c) Easier capacity expansion
d) Cost effective transmission
e) No O-E-O conversion delays
f) Wave length leasing instead of Bandwidth leasing
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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
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Submarine Fiber Optic Network system
SLTE, PFE, LME,
NMS and DCN
Fully integrated Undersea System
Using with -
Cables
Repeaters
Branching Units
Terminal Equipment
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What makes a Submarine Cable Network
Terminal Power Feeding
Equipment
Equipment
Cable
station
Network Management
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Cable
Branching unit
Repeater
Undersea Cables
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Double Armoured Cable – For Deep & Rocky Seabed for double protection
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Functions of Submarine Network
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Functions & Terminologies
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Submarine Wetplant & components
Wet plant comprises the following equipment/components:
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Undersea Cable
Land Cable
Optical Fiber
Cable joints
Undersea Repeaters
Gain equalizers
Branching Units
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Major Components of Submarine system
SLTE &
Wetplant
NMS
SL-17
Undersea
Cable
Full Fiber Drop
Branching Unit
CTE
Beach
Joint
Cable Station
TRPDR l 1
RL Cable
WTE
+
TLA
HV Power
HV Shield
Undersea
Repeater
NMS
N Channels
TRPDR l 3

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
PLINB
Ocean
Ground
TRPDR l 2
ADM
STM-16/
STM-64
TRPDR l n
Ground
LTE #1
TRPDR l 1
OGPP
PFE
N Channels
TRPDR Transponder
OGPP : Ocean Ground Protection Panel
PFE : Power Feed Equipment
RL : Rodent Lightning
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Building
Ground
COTDR
LME
TRPDR l n
LTE #2
TLA : Terminal Line Amplifier
WTE: Wavelength Termination Equipment
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ADM
TRPDR l 3
HV : High Voltage
LME : Line Monitoring Equipment
TRPDR l 2
STM-16/
STM-64
Submarine Transmission Line Terminating Equipment
TRPDR
l1
1
IP
l2
WTE
Note: Any module of the LTE may not be
included depending on the specific
requirements of the system (distance, bit
rate, SDH or SONET equipment, etc.)
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ADM
10 Gbps
(S-64.2)
Interface
One
Fiber-Pair
lN-1
OXC
N-1
lN
ATM
N
(optional) ILE
Line Monitoring Wavelengths
(only for repeatered systems)
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Line Amp
N x 10Gbps
Submarine
Cable
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
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Inside Repeater & different types
Am plifier Pair Chass is
Locking Plate
Heat Transfer Plate
Supervisory
Erbium Am plifiers
Power Supply
Pum p Unit
Control Circuit
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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.
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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.
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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.
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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.
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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.
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PFE – Submarine System powering overview
Current
PFE
-
PFE
+
Virtual Ground
Station B
Station A
Example of a Trunk Point to Point Powering System
PSBU 1
PSBU 2
Current
PFE
+
PFE
-
Station A
Station B
PFE
-
PFE
-
Station C
Station D
Example of a Normal Powering scenario for a Trunk and Branch Configuration
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Fault Isolation & Repair in Wetplant
 Detection and localization of Subsea faults
 Two categories
- Optical
- Electrical
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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.
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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.
Outer Cable
HV conductor
Fiber
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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.
Outer Cable
 Type 4 fault - damage in the optical path without significant electrical alteration of
the power-feeding conductor continuity and insulation.
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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)
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Optical Fault Localization
What is a OTDR?
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?
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.
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OTDR Vs COTDR
Repeater
Repeater
Repeater
HLLB
HLLB
HLLB
Light Pulse
OTDR
Backscatter
OTDR can only measure
up-to first repeater
Repeater
Repeater
Repeater
HLLB
HLLB
HLLB
Light Pulse
COTDR
Backscatter
OTDR can cross the repeaters & can
measure till opposite end terminal
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COTDR Measurement plot
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Electrical path Fault Localization
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.
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Electroding
Electroding technique is sending low-frequency AC tone from Terminal PFE,
using the capabilities of the PFE coupled & with special detection equipment
having low-current dc and low-frequency resistance and capacitance
measurements which can be used in repair ship to find out the exact fault.
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.
Fault Detected at
Tone leakage point
X
Electroding Signal Low frequency A.C tone
4Hz to 50Hz
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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.
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A Shunt Fault
Shunt Fault –
Shunt Fault –
Dual end PFE Feed,
Not Service affecting
Single end Feed,
Service affecting
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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
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Sub Marine cable System visual tour
Sub Marine cable system Video
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CABLES AROUND AFRICA
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Thank You!
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