3.3 - DEFINITIONS Flashcards
Amplitude?
a wave’s maximum displacement from its equilibrium position
antinode
a position of maximum displacement in a stationary wave
cladding
a protective layer on an optical fibre
coherent waves
waves which have the same wavelength and frequency and a fixed phase difference
diffraction grating
a grating with hundreds of slits per millimetre which results in sharper interference patterns
diffraction
the spreading of waves as they pass through a gap of similar magnitude to their wavelength
electromagnetic waves
waves which consist of perpendicular electric and magnetic oscillations
frequency
the number of waves that pass a point in a unit time period
fringe spacing
the distance between two adjacent bright fringes or two adjacent dark fringes
interference
the superposition of waves which occurs when two waves meet; either constructive or destructive
laser
a coherent light source
longitudinal wave
a wave with oscillations that are parallel to the direction of energy propagation
material dispersion
waves of different wavelengths travel at slightly different speeds through an optical fibre and so reach the end of the fibre at slightly different times
modal dispersion
waves enter an optical fibre at slightly different angles, so the distance each beam has to travel is slightly different; this leads to pulse broadening
node
a position of minimum displacement in a stationary wave
optical fibre
a thin glass fibre with a surrounding layer of cladding through which signals are passed
path difference
a measure of how far ahead a wave is compared to another wave; terms of the wavelength
phase difference
the difference in phase between two points on a wave; radians
Phase
a measure of how far through the wave’s cycle a given point on the wave is
polarisation
the restriction of a wave so that it can only oscillate in a single plane; only for transverse waves
pulse broadening
the elongation of a signal passed down an optical fibre, due to modal/material dispersion
refractive index
a material property; the ratio of speed of light in a vacuum to the speed of light in a given material
stationary wave
a wave that stores, but does not transfer, energy
total internal reflection
an effect that occurs in optical fibres, where full reflection occurs at the inside boundary of the fibre, meaning that no radiation passes out
