Topic: Optoelectronics
For a single mode optical cable with $0.25~dB/km$ loss, the optical power 100 km from a 0.1 mW source will be
- A. -30 dBm
- B. -35 dBm
- C. -40 dBm
- D. -45 dBm
Answer: B. -35 dBm
Explanation: Power input $= -10~dBm$ (since $0.1~mW = 10 \log_{10}(0.1) = -10~dBm$). Path loss $(L_{p})=0.25\frac{dBm}{km}\times100~km = 25~dB$. Power output $=-10-25=-35~dBm$.