2. Introduction
• An optical fiber is essentially a waveguide for light
• It consists of a core and cladding that surrounds the core
• The index of refraction of the cladding is less than that of the
core, causing rays of light leaving the core to be refracted back
into the core
• A light-emitting diode (LED) or laser diode (LD) can be used
for the source
• Advantages of optical fiber include:
• Greater bandwidth than copper
• Lower loss
• Immunity to crosstalk
• No electrical hazard
4. Total Internal Reflection
• Optical fibers work on the principle of total
internal reflection
• The angle of refraction at the interface between
two media is governed by Snell’s law:
n1 sin1 n2 sin2
6. Types of Fiber
• SStep-index fibers has the index of refraction changing radically between the
core and the cladding
• Graded-index fiber is a compromise multimode fiber, but the index of
refraction gradually decreases away from the center of the core
• Graded-index fiber has less dispersion than a multimode step-index fiber
9. • Wavelength
It is a characteristic of light that is emitted from the
light source and is measured in nanometers(nm).
In the Visible spectrum , wavelength can be described
as the colour of the light.
• Frequency
It is a number of pulse per second emitted from a light
source.
Frequency is measured in units of hertz (Hz)
1Hz= 1pulse/sec
10. • Window
A narrow window is defined as the range of
wavelengths at which a fiber best operates .
Window Operational Wavelength
800nm-900nm 850nm
1250nm-1350nm 1300nm
1500nm-1600nm 1550nm
11. • Attenuation
It is defined as a loss of optical power over a set distance, a fibre
with lower attenuation will allow more power to reach a receiver
• Example:
• Absorption
• Scattering
• Bandwidth
It is defined as the amount of information that a system can
carry such that each pulse of light is distinguishable by receiver.
12. • Numerical Aperture :
Numerical aperture(NA) is the “light- gathering
ability” of a fibre.
Light injected into the fibre at angles greater than the
critical angle will be propagated .
NA= n1
2 - n2
2
where n1 and n2 are refractive indices of Core and
Cladding resp..
13. Communication Systems
Basic Blocks
• Three basic components
1. Source and Transmitter
2. Destinations and
Receiver
3. Communication channel
(medium)
• Communication channel
• Wired
• Wireless
• Glass
• Water and or materials
Coverage and Topology
• Coverage (public
network)
• LAN
• MAN
• WAN
• Topology
• Bus
• Ring
• Mesh
• Star
18. Overview of WDM
• A characteristic of WDM is that the discrete wavelengths form an
orthogonal set of carriers that can be separated, routed, and
switched without interfering with each other.
• WDM networks require a variety of passive and active devices to
combine, distribute, isolate, and amplify optical power at different
wavelengths.
22. ROADM
• Reconfigurable Optical Add-Drop Multiplexer
• A reconfigurable optical add-drop multiplexer (ROADM) is a device
that can add, block, pass or redirect modulated infrared (IR) and
visible light beams of various wavelengths in a fiber optic network.
• ROADMs are used in systems that employ wavelength division
multiplexing.
24. GNPy: Optical Route Planning Library
• GNPy is an open-source, community-developed library for building route
planning and optimization tools in real-world mesh optical networks.
• It is based on the Gaussian Noise Model.
• Simulations are driven by a set of JSON or XLS files.
• the network topology, which describes how the network looks like, what are
the fiber lengths, what amplifiers are used, etc.,
• the equipment library, which holds machine-readable datasheets of the
equipment used in the network,
• the simulation options holding instructions about what to simulate, and
under which conditions.
