In optical networking, dBm (decibel-milliwatts) is the standard unit for measuring optical power in transceivers like the QSFP28 LR4. It represents the signal strength relative to 1 milliwatt of power. In QSFP28 LR4 modules, which use four lanes to transmit data, monitoring power in dBm ensures stable performance across the network.

Why dBm Matters in QSFP28 LR4:

Each of the 4 lanes in a QSFP28 LR4 module transmits optical power, and monitoring the power in dBm ensures that all lanes are operating within the acceptable range. For the QSFP28 LR4, transmit power typically ranges from -4.3 to +4.5 dBm, while receive power ranges from -10.6 to +2.8 dBm. If one lane shows significantly lower or higher power in dBm than the others, it could signal a problem with the fiber, connectors, or transceiver itself.

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