Optica Communicatio
Operating range > 10^13 Hz to 10^16 Hz
Modal Bandwidth(Mhz-km)
The capacity of an optical fiber measured in MHz-km (megahertz over one kilometer). One MHz-km equals
approximately . 7 to . 8 Mbps.
Coaxial cable : 100 MHz km
Optical Fiber : 5000 GHz km
Advantages of Optical Fibre
●Enormous potential bandwidth 5000 GHzkm
●Small size and light weight: Diameter comparable to human hair
●Electrical isolation :Fabricated from glass or plastic polymers thus electrical insulators, Suited in electrically
hazardous environment as fiber produces no arcing or short circuits
●Immunity to interference and crosstalk: Free from electromagnetic and radio frequency interference, no EMI
shielding required, Thus many fibers can be bundled together
●Signal security: Light is confined to optical fiber, No radiation outside fiber hence data is secured
●Low transmission loss: Loss as low as 0.15 dB/km
●System reliability and ease of maintenance: Lifetime of 20 to 30 years
●Low cost: Glass is not a scarce resource compared to copper, Optical equipments may be costly but overall cost of
optical system is less than coaxial system due to advantages offered by fiber
Refractive Index(RI)
n = c / v dimensionless
Where, cis the speed of light in vacuum and
vis the phase velocity of light in the medium.
refractive index of water is 1.333
Snell's law: n1*sinθ1 = n2*sin θ2
Or ( sinθ1 / sinθ2 ) = n2 / n1
Numerical Aperture
Relative Refractive Index
n1=RI of core
