How to Test Optical Power with a dBm Meter: Wavelengths (1310, 1490, 1550 nm)

Wavelength Mapping in Telecom & Cable Networks

1310 nm: Upstream data from customer ONT to the central OLT.

1490 nm: Downstream broadband data from the OLT to customer ONTs.

1550 nm: Broadcast digital cable TV (CATV RF overlay) and long-distance trunks.

The Difference Between dB and dBm

dBm is an absolute measurement of power referenced to 1 milliwatt (0 dBm = 1 mW, +10 dBm = 10 mW, -20 dBm = 0.01 mW).

dB is a relative ratio representing optical loss or gain. For example, a 1:2 splitter introduces roughly 3.7 dB of loss.