physical foundations of telecommunication

A fiber optic data network at 2.5Gb/s is designed for parallel processed 100 cluster of computers, where data from each computer is being shared with others for performing finite element method based radar cross section calculation of AEGIS cruiser. Direct modulation of semiconductor laser diodes with equivalent circuit model of series resistance of Rs=3? and bond wire inductance of LB=0.1nH followed with shunt RC circuit of Rs=5? and Cj=0.2pF at 1550nm. The relaxation oscillation frequency of this laser is above 10GHz. The ECL digital bit stream of 1V P-P is efficiently provided to laser using a combination of Bias T and resistive matching to 50?? source impedance. Laser is biased above threshold (Ib=1.05Ith) and has responsivity of ?L =0.7mW/mA with light coupling of KL =70% to single mode fiber. Broadcasted optical digital on-off keying bit streams is received by optical receiver of each computer after suffering excess loss of 3dB in combination of optical connector and fiber loss in addition to 100x100 star coupling loss. Optical intensity demodulated optical transceivers are implemented at each cluster. Broadband optical receiver is a combination of PIN photodiode with optical coupling loss of KD =50% and photon responsivity of ?D =0.35mA/mW. Photocurrent is amplified using TZA with flat gain of 35dB? into a 50??load over bandwidth of 10GHz. (4 pts) (a) Justify why a resistor of 42? is suitable for broadband matching of optical transmitter; (4 pts) (b) Find P-P value of digital pulse current through laser junction; (4 pts) (c) Find P-P value of photocurrent detected by PIN photodiode and output voltage across 50? load; (3 pts) (d) How much is the shot noise received at output load?