*****IMPORTANT Q2 & Q4*******
(MODEL EXAMPLES WILL BE GIVEN FOR EASIER SOLVING)
1. A silica multimode step-index fiber has core and cladding refractive indices of 1.48 and 1.46, respectively. The equilibrium length of the fiber is 2 km. The light source emits at 820 nm and has a spectral width of 120nm. Compute the electrical 3-dB bandwidth of a 5-km length of this fiber and the maximum RZ and NRZ data rates.
Repeat the problem for a Graded-index fiber when the spectral width of the
light source is reduced to 20 nm.
2. 20 SI fibers, 2 km long each, are spliced together for a 40 km link. Each fiber has a loss rate of 1-dB/km and a numerical aperture of 0.24. Each splice adds 0.5 dB of loss. A laser diode has a threshold current of 10 mA and emits at 3 mW/mA rate. A diode current of 15 + 3sin t (mA) produces an optical signal, which is coupled into this 40 km SI fiber. After 20-km propagation length, an erbium-doped fiber amplifier having a gain of 15 dB amplifies the signal before the signal is recorded by a photodetector at the end of this link. This photodector has a responsivity = 0.5 A/W and a load resistance of 100 . Two connectors are used and each one has 1 dB loss.
Compute the signal voltage at the detector’s output.
3. An analog system has a bandwidth of 10 MHz, a photodetector of = 0.5 A/W and ID = 1 nA, and a signal to noise ratio (SNR) of 30 dB. The receiver’s temperature is 270 C and the load resistance is 50 .
(a) How much optic power must reach the receiver?
(b) Complete the system design if the fiber length is 5 km.
4. Design a digital system transmitting a 1-Gbps RZ signal over a 50-km path without the use of repeaters. The error rate must be 10 or better.
(Please list the components in the summary of each design )