Assignment 2 (Transmission characteristics of optical fiber)
1- An Optical power of 100  W is fed into an optical fiber of length 10 km. the
output power is found to be 5  W. Calculate:
i)
The overall loss in dB assuming no connectors or splices.
ii)
The overall loss in dB/km.
iii)
The overall signal attenuation for a 20 km optical link using the same fiber
with splices at 1 km intervals, each of 1 dB attenuation.
2- A certain optical fiber has an attenuation of 0.6 dB/km at 1300 nm and 0.3
dB/km at 1550 nm. Suppose the following two optical signals are lunched
simultaneously into the fiber: an optical power of 150  W at 1300 nm and an
optical power of 100  W at 1550 nm. What are the power levels in  W of
these two signals at a) 8 km and b) 20 km.
3- A continues 12-km-long optical fiber link has a loss of 1.5 dB/km.
a) What is the minimum optical power level that must be launched into
fiber to maintain an optical power level of 0.3  W at the receiving
end ?
b) What is the required input power if the fiber has a loss of 2.5 dB/km?
4- A) An LED with a spectral width of 17 nm is used as an optical source. The
optical fiber is of 20 km length. Due to material dispersion, the pulse spreads
at the output at 1.76 ns/km. calculate the amount of material dispersion.
b) Compare the threshold optical powers of simulated Brillouin and Raman
scattering within the fiber at an operating wavelength of 1.25  m. The single
mode fiber has a core diameter of 5  m with an attenuation of 0.5 dB/km. The
source is a laser diode with a bandwidth of 500 MHz.
PB= 4.4  10 3 d 2 2
PR= 5.9  10 2 d 2 