What do the values ​​on the optical power meter mean

An optical power meter measures the optical power of light signals, typically reporting absolute power in dBm or relative power/loss in dB.

Absolute Optical Power

Optical power meters measure the absolute power of light traveling through a fiber or emitted by a source. This is usually expressed in dBm, which is a logarithmic unit relative to 1 milliwatt of optical power. Positive dBm values indicate power above 1 mW, while negative values indicate power below 1 mW . Absolute power measurements are essential for verifying transmitter output, receiver input, or the performance of optical components.

Relative Power and Loss

In addition to absolute power, optical power meters can measure relative power changes or optical loss, expressed in dB. This is a comparative measurement, showing the difference between a reference power level and the measured power. For example, a connection loss of –3 dB means the output power is half of the reference input power . Relative measurements are commonly used to assess fiber link losses, connector losses, or splice losses.

Measurement Units and Ranges

• dBm: Absolute power relative to 1 mW, commonly used for fiber optic transmitters and receivers .
• dB: Relative power or loss compared to a reference, useful for evaluating link performance .
• Typical optical power ranges for fiber optics are from +3 dBm to –50 dBm, with most laser sources in the 0 to –10 dBm range and LEDs in the –10 to –20 dBm range .

Wavelength Dependence

Optical power meters are wavelength-sensitive, meaning the meter must be set to the correct wavelength of the light source to ensure accurate readings. Incorrect wavelength settings can lead to measurement errors .

Summary

In practice, an optical power meter provides:

• Absolute optical power (dBm)
• Relative power or loss (dB)
• Measurements across specific wavelengths relevant to fiber optic systems
• Typical power ranges suitable for lasers and LEDs in communication networks . These measurements are critical for testing, troubleshooting, and maintaining fiber optic networks.