Solution:

To be useful in an optical link, a light source needs the following characteristics:

• 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 the transmission windows for the fiber type used.

• To couple large amounts of power into an optical fiber, the emitting area should be small.

• To reduce material dispersion in an optical fiber link, the output spectrum should be narrow.

• The power requirement for its operation must be low.

• The light source must be compatible with modern solid-state devices.

• The optical output power must be directly modulated by varying the input current to the device.

• High optical output power.