4. A repeater-less fibre optic communications link is to be 10km long. The LED light source produces 8mW at 0.82μm, has an emitting area of 80μm. and an NA=1. It is closely coupled to short connecting fibre having an NA=0.3. A fibres of 1km length are used having an NA=0.3, core diameter = 50μm and an attenuation of 2dB/km. Connectors having a loss of 2dB from all sources are to be used. The receiver has an anti-reflecting surface, an input diameter of 100μm and an NA of 0.5 Calculate the detected light power. (-47.5dBm)

4. A repeater-less fibre optic communications link is to be 10km long. The LED light source produces 8mW at 0.82μm, has an emitting area of 80μm. and an NA=1. It is closely coupled to short connecting fibre having an NA=0.3. A fibres of 1km length are used having an NA=0.3, core diameter = 50μm and an attenuation of 2dB/km. Connectors having a loss of 2dB from all sources are to be used. The receiver has an anti-reflecting surface, an input diameter of 100μm and an NA of 0.5 Calculate the detected light power. (-47.5dBm)