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Optical fibre

Lasted edited by Andrew Munsey, updated on June 15, 2016 at 2:02 am.

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Modern power system practice demands rapid and reliable information exchange among Generating Stations, Substations, Load Despatch Centre for efficient Network Management with an ultimate objective to deliver uninterrupted & quality power to consumers. And a dedicated and reliable communication network can meet the demand of modern power system management

An optical fiber is a glass or plastic fiber designed to guide light

along its length. Fiber optics is the overlap of applied science and

engineering concerned with the design and application of optical fibers.

Optical fibers are widely used in fiber-optic communication, which permits

transmission over longer distances and at higher data rates than other forms

of communications. Fibers are used instead of metal wires because signals

travel along them with less loss, and they are immune to electromagnetic

interference. Optical fibers are also used to form sensors, and in a variety of

other applications.

State-of-the-art communication systems are required for voice, data, telemetering, telecontrol, protection, signalling, networking etc.

For voice / data communication as well as signalling, power utilities in State & Central Sector install Power Line Carrier Communication ( PLCC ) links which suffer from the following drawbacks:-

i) Low Bandwidth

ii) Noisy Communication

iii) Shutdown of power line to attend to outdoor accessories.

iv) Frequency approval from PTCC.

Urban utilities used to lay underground pilot cable alongwith EHV & HV power

cables. But underground copper communication links have the following demerits :-

i) High electromagnetic interference

ii) Fall of insulation resistance due to ingress of moisture

iii) Prone to theft & pilferage

iv) Limited bandwidth

v) High cost

Over the years the need for the modern communication facility in power sector is strongly felt and from mid-eighties optical fibre cable started replacing old communication medium.

Optical Fibre was chosen due to following advantages:-

1) Low transmission loss

2) High bandwidth

3) Lighter and less bulky

4) Immune to electromagnetic interference

5) Transmission is secure and private

6) No cross-talk between adjacent channels

7) Can withstand harsh environmental conditions

8) Less cost.


Two types of fibre are available - monomode & multimode and the application of monomode fibre is predominant worldwide.


O.F. routes are to be meticulously planned to interconnect all major stations and premises. Present and future requirements of voice, data, and protection signaling of all the stations are to be considered while determining the fiber count of cables to be laid. The critical locations have to be provided with alternate route.


a) General Broad Band Communication

Optical Line Terminal Equipments equipped with Multiplexers installed at stations are connected through one pair of fibers and carry the following type of traffic :-

i) Voice & Data

ii) Trip transfer signaling

iii) Telemetry & SCADA data

iv) MAN connectivity

b) Fibre Based Protection Signaling

Microprocessor based differential protective relays installed at substations are connected directly through one pair of fiber. Besides providing normal protection to lines, the disturbance in the system caused due to fault, which is cleared by the protective relay, can also be recorded in the memory of the relay. This is of great help in analyzing the cause of disturbance.

c) Substation Control From Remote Location

Here all the bays of the remote substation will have numerical relays which will be connected through OPTICAL LAN to a local server which will be extended to a Central Server at manned station through the pair of fiber.



After laying the pieces of optical cables, splicing of fibers is carried out inside a Straight Joint Closure (SJC) which is compact, air & water tight and rugged. Splice points are protected in sleeves and placed in the grooves of the splice tray.

At substation ends splicing is carried out in Termination Junction Box (TJB). Here the fibers of the main cable are spliced with Pig Tails - a special cable whose one end is connectorised.

Finally the pigtail ends are terminated on to a Fibre Distribution Frame.


The two cut ends of fibers are spliced (joined) by a highly sophisticated machine called “Splicing Machine” which enables a high voltage arc-fusion technology converting the cut ends into a single union. The cutting, rather called cleaving of bare ends of fibers is of immense importance regarding the quality of splice and is done by a high precision Optical Fibre.


Modern fiber cables can contain up to a thousand fibers in a single cable, so

the performance of optical networks easily accommodates even today's

demands for bandwidth on a point-to-point basis. However, unused point-to-

point potential bandwidth does not translate to operating profits, and it is

estimated that no more than 1% of the optical fiber buried in recent years is

actually 'lit'.