Download OFC Part 1

Essentials of
Fiber Optic Communications
Part-I: Introduction to Optical Communications
Prerequisite
Basics of Telecom Networks
Physics/Chemistry (BS Level)
Course Objectives
At the completion of the course the participants shall
be able to:
1 - Have the contemporary knowledge of optical
fibers in telecommunications perspectives.
2 - Take more advanced courses in Optical
Communication Networks.
Main Uses in Telecom
In Telecom, Optical Fiber Networks are used for communication of
data (mostly digital) of voice, video, internet, and other broadband
systems.
Exchange to Exchange Connectivity (Core Transmission Network)
LE – LE
LE = Local Exchange
LE – TE
TE = Transit Exchange
TE – TE
TE – GE
GE = Gateway Exchange
GW – GE
(e.g. SEA-ME-WE-3, SEA-ME-WE-4 etc)
Router – Router
Internet Connectivity and Internal
Router: Edge-, Subscriber Edge-,
Inter-Provider Border-, Core- ROUTERS
Enterprise Router: Access-, Distribution-,
Core- ROUTERS
Switch – Switch
Main Uses in Telecom
Exchange to User Connectivity (Access Network)
OLT – ONU
OLT = Optical Line Terminator
ONU – User
ONU = Optical Network Unit
Besides Telecom Applications, Optical Fibers have a number of
other applications in Domestic, Commercial, Industrial, and Military
setups.
General Communication System
Information Source
Transmitter
Transmission Medium
Receiver
Information Destination
Optical Communication System
Optical Communication System
Functional Elements of Optical Fiber Systems
Services
Path-Termination Equipment (PTE)
Line-Termination Equipment (LTE)
Section-Termination Equipment (STE)
Photonics
Role of Functional Elements of Optical Fiber Systems
Encoding
Carrier Modulation
Multiplexing
System Administration
Physical Elements
Modulator/Demodulator
Mutliplexer/Demultiplexer
Encoder/Decoder
Optical Transmitter
Optical Receiver
Repeater or Regenerator
Drop/Insert Repeater
Optical Link
Optical Communication Signal/Spectrum
Different Regions in Infrared
• Near Infrared
750 nm – 1400 nm in wavelength
Used in Optical Fiber Telecommunication because of
low attenuation losses in the Silica glass Fiber
• Short Wavelength IR (or shortwave-IR)
1400 – 3000 nm
• Mid Wavelength IR (or intermediate-IR)
3ooo – 8000 nm
• Long Wavelength IR
8000 – 15000 nm
• Far Infrared
15000 – 1,000000 nm
Telecommunication bands in Infrared
Optical telecommunication in the near infrared is
technically often separated to different frequency bands
because of availability of light sources, transmitting
/absorbing materials (fibers) and detectors.
–
–
–
–
–
–
O-band 1,260–1,360 nm
E-band 1,360–1,460 nm
S-band 1,460–1,530 nm
C-band 1,530–1,565 nm
L-band 1,565–1,625 nm
U-band 1,625–1,675 nm
Optical Windows and Bands
Optical Fiber Cable
Optical Fiber Material

Silica Glass
Silica-Rich Glass Optical Fiber
Multicomponent Glass Optical Fiber
Silica-Halide Glass Optical Fiber
 used for high-speed data applications

Plastics
 used for low-speed data / voice applications

Composite Constructions
 used for low-speed and specialized applications
Structure of Optical Fiber
Within the same thin cylindrical structure of a fiber, there
are two optically different concentric cylinder; the inner
one is more optical density (higher refractive index).
This optical density variation is obtained by suitably
doping the pure silica glass structure during optical fiber
fabrication:
Core Optical Density Increased
Cladding Optical Density Decreased
Both of Above
N.B:
Refractive Index of a material is the ratio of speed
of light in vacuum to speed of light in that material; more
the refractive index of a material is, the more light is
refracted or bent while being transmitted out of that
material to air or lower refractive index material.
Structure of Optical Fiber/Cable
Secondary Buffer 900
Primary Buffer 250
Cladding 125
Core (62.5)
All measurements are in micrometer
Signal Transmission in Optical Fibers
Bending of light ray:
Light traveling in optically denser medium (Higher Refractive Index) shall
bend away from normal to the optical media boundary at media interface,
whereas
Light traveling in optically rarer medium (Lower Refractive Index) shall bend
away from normal to the optical media boundary at media interface.
Details of this theory shall be discussed in Part-III.
Signal Transmission in Optical Fibers
Total Internal Reflection
Transmission of Optical Signals in Optical Fibers
So, Optical Signals in Optical Fibers travel from
one end to the other by Total Internal Reflection