problem 1) What are the needs of optical receiver? Describe each block of receiver design.
b) Find the expression for 3dB modulation bandwidth of LED and describe the significance of radiative recombination life time.
problem 2)a) A pin photodiode on average generate one electron hole pair per three incident photons at the wavelength of 0.8μm. Supposing all the electrons are collected, find out
i) Quantum efficiency of the device
ii) Its maximum possible band gap energy
iii) The mean output photocurrent when received optical power is 10–7W.
b) Commonly available single mode fiber have beat length in range 10cm < Lp < 2m. What rate of refractive index does this corresponds to for λ=1300nm?
problem 3)a) Sketch the schematic diagram of high radiance surface emitting LED and describe its working in detail.
b) What are the basic attenuation mechanisms in the optical fiber communication? Describe in brief on what factors this mechanism depends?
problem 4)a) What are the advantages and disadvantages of LED and describe the key process involved in the LASER operation.