Typical power levels measured by an optical power meter: Telecom transmitters: 0 to +10 dBm (1 to 10 milliwatts), Receivers: -30 dBm (1 microwatt) DWDM systems with fiber amplifiers: +10 to +20 dBm (10 to 100 milliwatts), Receivers: -20 to -30 dBm (1-10 microwatt). Typical power levels measured by an optical power meter: Telecom transmitters: 0 to +10 dBm (1 to 10 milliwatts), Receivers: -30 dBm (1 microwatt) DWDM systems with fiber amplifiers: +10 to +20 dBm (10 to 100 milliwatts), Receivers: -20 to -30 dBm (1-10 microwatt). A decibel (dB) is a unit used to express relative differences in signal strength. A decibel is expressed as the base 10 logarithm of the ratio of the power of two signals, as shown here: 10 is the base 10 logarithm, and P1 and P2 are the powers to be compared. 10 is different from the Neparian. Fiber Optic Measurement Units: "dB" and "dBm" Whenever tests are performed on fiber optic networks, the results are displayed on a power meter, OLTS or OTDR readout in units of “dB. ” Optical loss is measured in “dB” which is a relative measurement, while absolute optical power is measured in “dBm,”. In the figure above, the transmitted optical power of the optical module is -3. 55 dBm, which is within the warning range of -3 dBm to -9. Extinction ratio is one of the important parameters used to measure the quality of optical modules. 023%) resolution may be occasionally useful in carefully controlled laboratory conditions, with an expert user.