Certified Fiber Optics Practice Exam

A loss of 3 dBm indicates what percentage of power loss?

1. 25%

2. 50%

3. 75%

4. 10%

The correct answer is: 50%

A loss of 3 dBm corresponds to a specific percentage of power loss that can be determined using logarithmic and exponential relationships in power measurements. In the context of dBm, 0 dBm is defined as 1 milliwatt (mW) of power. Each 10 dBm increase represents a tenfold increase in power, while each decrease represents a tenfold reduction. The formula to convert dBm to a linear power ratio involves calculating the power ratio in terms of mW. When we have a loss of 3 dBm, it means that we are looking at a decrease of power from the original level. A loss of 3 dBm can be calculated as follows: 1. The linear power ratio corresponding to a -3 dBm loss is determined by the formula: \[ P_{\text{new}} = P_{\text{original}} \times 10^{\left(\frac{-3}{10}\right)}. \] 2. This results in approximately: \[ P_{\text{new}} = P_{\text{original}} \times 0.707. \] This indicates that the new power level is about 70.7% of the original