3. A laser emitter sends an optical signal along a fibre optic link to a photodetector. The setup is shown below. Laser Emitted Power = ? Wavelength 950 nm Fibre Optic Link Attenuation = 0.35 dB/km Photodetector ? 50 km P a. If the photodetector can detect 20 nW of optical power, what should be the minimum emitted power of the laser? b. What assumptions did you make for your calculations? For each assumption stated, please reason whether they are acceptable for the given situation.