Characteristics of Light Source for Communication

A light source needs the following characteristics is given below :
  • It must be possible to operate the device continuously at a variety of temperatures for many years.
  • It must be possible to modulate the light output over a wide range of modulating frequencies.
  • For fiber links, the wavelength of the output should coincide with one of transmission windows for the fiber type used.
  • To couple large amount of power into an optical fiber device the emitting area should be very small.
  • To reduce material dispersion in an optical fiber link, the output spectrum should be too much narrow.
  • The optical output power must be directly modulated by varying the input current to the device.
  • High coupling efficiency.
  • Low weight and low cost.
  • Better linearity to prevent harmonics and inter-modulation distortion.
  • High optical output power.
  • High reliability.
  • The power requirement for its operation must be low.
  • The light source must be compatible with the modern solid state device.
Two types of light sources used in fiber optics are full form of LEDs and laser
diode (LD).