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.