Question

(TCO 6) A cable company is running a fiber-optic link between the head end and a neighborhood five miles away. The signal applied to the fiber goes through an optical connector having 3dB LOSS at the head end, the fiber has a LOSS of 1 dB, and the connector at the end of the fiber has a LOSS of 3 dB before being applied to an amplifier used to make up for the losses. The desired signal at the output of the amplifier is 10 dBm, and the signal level applied to the fiber connector at the head end is 10 dBm. What should the gain of the amplifier be to have 10 dBm at the output of the neighborhood amplifier

Answer 1

7 dB

Step-by-step explanation:

• The total loss from the headend to the amplifier input is the sum of the losses along the fiber, that we simply add as they are in dBs:
• Total Loss = 3 dB + 1 dB + 3 dB = 7 dB
• The signal at the amplifier input is just +10 dBm- 7 dB = +3 dBm
• So as the output level at the Headend and the one at the output of the neighborhood amplifier must be equal each other (compensating all losses in the path), the amplifier gain must be equal to the cumulative loss, i.e. , 7 dB, so that the amplifier output level be + 10 dBm.