What is the Difference Between dB and dBm?
🆚 Go to Comparative Table 🆚The main difference between dB and dBm lies in their units and what they measure.
- dB (Decibel):
- It is a logarithmic unit of measurement used to express the ratio or difference between two power levels.
- It is a relative measurement and does not have an absolute value.
- In the context of fiber optics, dB represents the difference between two dBm values.
- dBm (Decibel Milliwatt):
- It is a unit used to express the absolute power level.
- It is an absolute unit that can be converted into watts.
- In fiber optics, dBm measurements are used to measure absolute power (e.g., signal strength or power level).
- 0 dBm is defined as 1 milliwatt (mW) of power into a power meter.
In summary:
- dB quantifies the ratio between two values (relative measurement).
- dBm expresses the absolute power level (absolute unit).
- dB is a dimensionless unit, while dBm is always relative to 1 milliwatt.
- dBm values can be converted into watts, but dB values cannot be.
Comparative Table: dB vs dBm
The difference between dB and dBm can be summarized in the following table:
Feature | dB (Decibel) | dBm (Decibel-milliwatt) |
---|---|---|
Unit Type | Dimensionless | Absolute unit |
Reference | Ratios between two values | Power level relative to 1mW |
Usage | Measures relative power | Measures absolute power level |
Conversion | Cannot be converted into watts | Can be converted into watts |
Application | Used for various purposes, including power measurements in the laboratory or field | Often used to determine cell phone signal strength at a site |
dB is a dimensionless unit that quantifies the ratio between two values, while dBm is an absolute unit that expresses the power level relative to 1 milliwatt (mW). dBc is used for various purposes, including power measurements in the laboratory or field, while dBm is often used to determine cell phone signal strength at a site. A strong cell phone signal is around -70 dBm or higher, while a weak signal is around -100 dBm or lower.
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