Brief flow of presentation

1. What are Optical Fibers?

2. Introduction

3. Evolution of optical fiber

4. Structure of optical fiber

5. Workings principle of optical fiber

6. Classification of optical fiber

7. Optical fiber communication system

8. Advantages / Disadvantages of Optical fiber

9. Applications of Optical fiber

10. Conclusion

what is optical fiBer? An optical fiber is a hair thin cylindrical fiber of glass or any

transparent dielectric medium.

The fiber which are used for optical communication are wave guides made of transparent dielectrics.

Its function is to guide visible and infrared light over long distances.

worKinG principle Total Internal Reflection

When a ray of light travels from a denser to a rarer medium such that the angle of incidence is greater than the critical angle, the ray reflects back into the same medium this phenomena is called total internal reflection.

In the optical fiber the rays undergo repeated total number of reflections until it emerges out of the other end of the fiber, even if the fiber is bent.

History 1880 Alexander Graham Bell

- Photo phone, transmit sound waves over beam of light

1930: TV image through uncoated fiber cables 1951: Flexible fiberscope: Medical applications

(endoscope).

camera

LIGHT

History Cont’d

1960: Laser invented 1967: New Communications medium: cladded fiber 1960s: Extremely lossy fiber:

More than 1000 dB /km 1970: Corning Glass Work NY, Fiber with loss of less

than 2 dB/km 70s & 80s : High quality sources and detectors Late 80s : Loss as low as 0.16 dB/km 1990: Deployment of SONET systems

Optical Fiber: Advantages

Capacity: much wider bandwidth (10 GHz)

Long lyf of fibres compared to copper.

Unaffected by interference of Lightening Magnetic fields Florescent light

Higher environment immunity Weather, temperature, etc.

FREQ DISTRIBUTION

Optical Fiber: Advantages

• Attenuation is lower than coaxial cable or twisted pair

• As it does not radiates energy any antenna or detector cannot detects it hence provides signal security

• There is no necessity of additional equipment for protecting against grounding and voltage problems.

ATTENUATION IN COMMUNICATIONS

• More information carrying capacity fibers can handle much higher data rates than copper. More information can be sent in a second

Disadvantages

Higher initial cost in installation Only point to point communication Strength

Lower tensile strength

Remote electric power More expensive to repair/maintain

Tools: Specialized and sophisticated Staff : skilled and specialized

Optical Fiber Architecture

Transmitter

InputSignal

Coder orConverter

LightSource

Source-to-FiberInterface

Fiber-to-lightInterface

LightDetector

Amplifier/ShaperDecoder

Output

Fiber-optic Cable

Receiver

Optical Fiber Architecture –Components

Light source Two common types:

LED (Light Emitting Diode)

ILD (Injection Laser Diode)

Source–to-fiber-coupler (similar to a lens):

A mechanical interface to couple the light emitted by the source into the optical fiber

InputSignal

Coder orConverter

LightSource

Source-to-FiberInterface

Fiber-to-lightInterface

LightDetector

Amplifier/ShaperDecoder

Output

Fiber-optic Cable

Receiver

Light detector: PIN (p-type-intrinsic-n-type) APD (avalanche photo diode) Both convert light energy into

current

ILD versus LeD

Advantages: more focused radiation pattern; smaller Fiber much higher radiant power; longer span faster ON, OFF time; higher bit rates possible monochromatic light; reduces dispersion

Disadvantages: much more expensive higher temperature; shorter lifespan

OptIcaL FIber cOnstructIOn Core – thin glass center of the

fiber where light travels.

Cladding – outer optical material surrounding the core(lower R.index)

Buffer Coating – plastic coating that protects the fiber.

FIber types

Plastic core and cladding Glass core with plastic cladding PCS (Plastic-Clad

Silicon) Glass core and glass cladding SCS: Silica-clad silica Under research: non silicate: Zinc-chloride

1000 time as efficient as glass

Classification of optical fiber

• Optical fiber is classified into two categories based on :-

1)The number of modesA.SINGLE MODEB.MULTIMODE2) The refractive indexA.STEP INDEXB.GRADED INDEX

types OF OptIcaL FIber

Single-mode Fiber

step-index Fiber

graded-index Fiber

n1 coren2 cladding

no air

n2 cladding

n1 core

Variablen

no air

Lightray

Index profile

sIngLe-mODe FIber

Advantages: Minimum dispersion: all rays take same path, same time to

travel down the cable. A pulse can be reproduced at the receiver very accurately.

Less attenuation, can run over longer distance without repeaters.

Larger bandwidth and higher information rate

Disadvantages: Difficult to couple light in and out of the tiny core

Highly directive light source (laser) is required

Interfacing modules are more expensive

muLtI mODe Multimode step-index Fibers:

inexpensive

easy to couple light into Fiber

result in higher signal distortion

lower TX rate

Multimode graded-index Fiber: intermediate between the other two types of Fibers

Losses In optIcaL FIber cabLes

The predominant losses in optic Fibers are: absorption losses due to impurities in the Fiber

material material or Rayleigh scattering losses due to

microscopic irregularities in the Fiber chromatic or wavelength dispersion because of

the use of a non-monochromatic source radiation losses caused by bends and kinks in the

Fiber pulse spreading or modal dispersion due to rays

taking different paths down the Fiber (µs/km) coupling losses caused by misalignment &

imperfect surface finishes

Fiber Alignment Impairments

Axial displacement Gap displacement

Angular displacement Imperfect surface finish

Causes of power loss as the light travels through the fiber!

WaveLength-DIvIsIon MuLtIpLexIng

WDM sends information through a single optical Fiber using lightsof different wavelengths simultaneously.

LaserOptical sources

λ1

λ2

λn

λn-1

λ3

λ1

λ2

λn

λn-1

λ3

LaserOptical detectors

Opticalamplifier

Multiplexer demultiplexer

• Medical

• Military

• Electronics

Telecommunications Computer applications Local Area Networks (LAN) Cable TV CCTV Optical Fiber Sensors

thanK You

- ROHIT THAKUR ECE SEC D IPEC