Sat 12 Nov: LED for Fibre Optics Info (1)

LED for Fibre Optics - by John MacDonald


Notes

Light from LED quickly modulated for use in fiber optics

Low maintenance

Energy efficient

Most common optical transmitter

Produces incoherent light

These semi-conductor transmitters are compact, efficient, reliable, operate at optical wavelength range, directly modulated at higher frequencies

LED is simply forward based p-n junction, emitting light through spontaneous emission (electroluminescence)

Emitted light has a relatively wide spectral width 30-60nm.

LED light transmission is, itself, inefficient – 1% of power is converted to launched power.

LED is relatively simple device, so cost effective

Most commonly made from Gallium Arsenide Phosphide (GaAsP) or Gallium Arsenide (GaAs)

GaAsP works at a larger wavelength (1.3 micrometers vs. 0.81-0.87 micrometers) output spectrum is wide by a factor of 1.7

Larger spectrum width = higher fiber dispersion, limits bit-rate distance product

To Do:

Find LED for operation at, or above, 1300nm (most likely fall in range of 30db+ and 10W+)

Find minimum transmission power for LED based on needs

Should generate 12.5MHz+