Certified Fiber Optics Practice Exam

How much power is equivalent to 1mW in terms of decibels?

1. -3 dBm

2. 0 dBm

3. 3 dBm

4. 1 dBm

The correct answer is: 0 dBm

The correct answer to the question regarding how much power is equivalent to 1mW in terms of decibels is 0 dBm. In fiber optics and telecommunications, decibels (dB) are often used to express power levels. The dBm scale specifically references 1 mW as the standard 0 dBm level. It is calculated using the formula: \[ \text{Power in dBm} = 10 \cdot \log_{10}\left(\frac{\text{Power in mW}}{1 \text{ mW}}\right) \] When the power is exactly 1 mW, the equation simplifies to: \[ \text{Power in dBm} = 10 \cdot \log_{10}(1) = 10 \cdot 0 = 0 \] Thus, 1 mW is expressed as 0 dBm, indicating that this is the reference level for the dBm scale. Understanding this reference point is fundamental for working with fiber optics as it helps in converting power levels measured in milliwatts to a logarithmic scale that can ease comparisons and calculations in communication systems.