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Communication
via optical fibres |
THIRD
YEAR LABORATORY
SYNOPSIS
OF EXPERIMENTS
PHYS3770/3780
Laser
and Spectroscopy and Photonics Laboratory
Acousto Optics
Light diffraction by acoustic waves in transparent media.
Two commercial acousto optic modulators/deflectors (flint
glass, lead molybdate) are used to gain an insight into
the similarities and differences between Bragg and Raman
Nath diffraction.
Fourier
Optics
An introduction to optical image processing, employing
a CCD camera and a frame grabber to capture images:
lenses as optical Fourier transform computers, spatial
frequencies and resolution, effect of filters in the
diffraction plane on the final image, manufacture of
simple blocking filters, frequency doubling and tripling.
Fourier
Transform Spectrometry
The Michelson interferometer as a spectrometer; Fourier
transform pair relationship between the interferogram
and the incident spectral distribution. Spectra of various
light sources, effect of colour filters and detectors
with different spectral responses. Limitations: resolution,
noise, aliasing.
Holography
Introduction to the principles and techniques of holography.
Transmission and white-light reflection holograms of
suitable objects, as well as a simple holographic transmission
interferogram, are produced.
Injection
Laser Diodes
The spectra, and light output as a function of injection
current, are measured for various kinds of laser diodes
and compared with the light emission from a red LED.
The
Neodymium YAG Laser
A Neodymium YAG laser, pumped by a semiconductor laser
diode, is set up on an optical table, using discrete
optical components; the properties of the light emitted
by both the laser diode and the YAG laser are studied
using a PC based fibre optic spectrometer.
Optical
Fibres
The fundamental properties of multimode and single mode
fibres are studied. Cleaving of fibre ends, coupling
of laser light into fibres, measurement of numerical
aperture and attenuation coefficient of a multimode
fibre, investigation of the far-field power distribution
of a single mode fibre as a function of angle.
Optical Fibre Communication
Optical characteristics of semiconductor sources (ILDs
and LEDs), fibre coupling components (both mateable-demateable
connectors and permanent splices), wavelength division
multiplexing and demultiplexing. A fibre optic communication
link with two analog inputs is constructed.
Optical
Fibre Sensors
Several intensity sensors, which exploit the optical
properties of multimode fibres, and a single mode interferometric
phase sensor are constructed. The sensitivity and resolution
of these devices are studied.
Optical
Spectroscopy
To understand the optical system and operation of a
commercial UV-visible spectrometer. Application to the
measurement of the transmission characteristics of thin
films, optical filters, sunglasses and commercial sunscreen
lotions.
Optical
Time Domain Reflectometry
An optical time-domain reflectometer is set up, using
discrete optical components on an optical table, and
is used to measure attenuation and splicing losses in
an optical fibre.
Photo
Detector and Light Source Characteristics
A 0.22 m spectrometer, coupled to a computer, is used
to study the spectra of different light sources. The
spectral output of a tungsten filament lamp is measured
with a thermopile and the relative spectral responses
of several photo-detectors are then measured and compared.
Polarisation
of Light
A photodiode detector is used to quantitatively study
linearly, circularly and elliptically polarised laser
light produced by: scattering in suspensions, linear
polarisers, quarter wave plates, circular polarisers,
reflection from dielectrics (Fresnel's laws) and reflection
from metals.
Properties
of HeNe Laser Light
Some properties of a HeNe laser and its light are studied
including: output stability, polarisation, longitudinal
modes, wavelengths emitted, spatial and temporal coherence,
use of a pinhole spatial filter, speckle phenomena.
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