Two 1-km fibers are spliced together. Each fiber has a 5-dB loss, and the splice adds 1 dB of loss. If the power entering is 2mW, then how much power is delivered to the end of this combined transmission line?

Ouput power = 0.159 mW

Step-by-step explanation

• First thing to do is  to calcculate the total loss in dB. It was stated in the problem that every 1 km of fiber has a 5dB loss, since we have 2 fibers with each of them has a lenght of 1km, therefore we have 10dB loss on it plus the addtiinal 1dB loss due to splicing.

total loss = (-5 dB) + (-5 dB) + (-1 dB) = -11 dB

 • The ngative sign signifies that it is loss.

•  To calculate the output power, ise the formula

10log(Pi?Po??)=dB

where:

Po = output power

Pi = input power = 2mW (given)

dB = -11dB

• Substitute all given values in the formula and derive to solve for output power (Po)

10log(2mWPo??)=−11dB

• divide both side of equation by 10 to eliminate 10 from left side of equation

1010log(2Po??)?=10−11?

log(2Po??)=−1.1

Po?=(2)(10)−11

Po?=0.159mW