What is Fiber Optics Communication? A Fiber
Optics refers to the Transmision and reception of information using
light frequency (1014 – 1015) carrier through a low-loss optical waveguide
Why Fiber Optics Instead of wires? Lightweight and noncorrosive
handles as many voice channel as a 1500 pair cables can!
low attenuation
high data rate
immune to
EMI, RFI, lightning and cross talk
no danger of electric shock!
The Fiber Cable Classifications Index Classification
Step Index – Abrupt index change from core to cladding
Graded Index – core index increase parabolically outward from the center.
Propagation Modes
Multimode – Step-index fiber – lightwaves propagates in many paths
Multimode – Graded index fiber – lightwave rays propagates slower at the center
Single or Monomode step – index fiber – lightwave rays has only one path
Losses in Optical Fiber Cables: Absorption Losses – Due to the heating of low impurities ultraviolet, Infrared, and Ion resonance Absorption
material or Rayleigh Scattering loss – Cause by imperfection in the fiber, such as tiny bubbles it has different effect on different wavelengths: 2.3dB at 820 nm, 0.24 at 1300 nm and 0.012 dB at 1550nm
Chromatic or Wavelength dispersion
Radiation Losses – caused by small bends and kinks in the fiber microbends – result of difference in the thermal contraction rates between core and cladding
Macrobends or Constant Radius bend – occur during handling or installation of cable
Modal Dispersion or Pulse Spreading – due to the difference in propagation time of light rays that takes different paths
Coupling or Connectors Losses – occur in every connection
Axial Misallignment – Transverse
displacement Angular displacement
End Separation or Gap Displacement
Surface Finish
Splice Loss – occur when two fibers are joined together without the use of connectors
Light Sources: LED – Light Emitting diode
ILD – Injection Laser Diode
Advantages of
ILD over
LED -More direct or focus radiation pattern (low NA)
-Greater radiation output power
-Higher Speed
-Generate Monocromatic Light
Disadvantages
-Expensive
-Shorter Life
-Temperature dependent
Light Detectors:
Photoconductors
Pin Diode – P intrinsic – N
APD - Avalanche Photodiode