fibre optics Flashcards
optic fibre
a thin tube in which light can propagate through successive total internal reflections
critical angle
the angle of incidence at which the angle of refraction is 90 degrees
total internal reflection
for an angle of incidence greater than the critical angle, no refraction takes place and the ray is reflected back into the medium from which it came
material dispersion
the dependence of the refractive index on wavelength in an optic fibre, which leads to different travel times for different wavelengths
high-order-mode path
a path of a ray entering an optical fibre that follows different paths and undergoes many internal reflections over a given distance
low-order-mode path
a path of a ray entering an optical fibre that suffers fewer reflections
waveguide dispersion
rays entering the fibre at different angles follow different paths and hence, have different travel times
step-index fibre
an optic fibre in which the refractive index changes abruptly between core and cladding
cladding
the concept describing the inner glass fibre in an optic cable being surrounded by another layer of different glass, in this way the core is protected and prevented from contacting with different cores
graded-index fibre
an optic fibre in which the refractive index of the core decreases gradually away from the core centre
attenuation
the loss of energy as radiation passes through matter
how attenuation is caused in an optical fibre?
attenuation in an optical fibre is caused by the scattering of light and the impurities in the glass core, the amount of it depends on the wavelength of light being transmitted
how do we define the power loss?
we define the power loss in decibels
what are the advantages of optical fibres?
low attenuation, no interference from stray electromagnetic signals, greater capacity, security against tapping
