You can check a switch's optical port power by viewing the TX (transmit) and RX (receive) optical power using CLI commands or Digital Optical Monitoring (DOM/DDM) features.

Understanding Optical Power

Optical power is measured in dBm and indicates the strength of light signals in fiber links:

• TX Power (Transmit): Light leaving the switch. Weak TX may indicate a failing SFP laser.
• RX Power (Receive): Light arriving from the remote device. Low RX is a common cause of intermittent link issues. Monitoring these values helps detect degradation before connectivity problems occur, even if the interface appears up .

Checking Optical Power on Cisco Switches

1. Verify SFP Recognition: Ensure the SFP module supports DOM/DDM and is recognized by the switch.
2. Use CLI Commands: Common commands include:
   • show interface <interface-id> transceiver detail – displays TX/RX power, temperature, voltage, and vendor info.
   • show hw-module subslot <slot> transceiver <port> status – shows optical power for specific modules on IOS-XR or NX-OS platforms .
3. Interpret Values: Typical TX/RX optical power ranges vary by module type, but negative dBm values (e.g., TX -5.7 dBm, RX -7.3 dBm) are common for short-range optics .

Checking Optical Power on Huawei Switches

1. Display Transceiver Info: Use commands like:
   • display transceiver interface <interface-type> <interface-number> – shows optical module details including TX/RX power, wavelength, and diagnostics.
   • display transceiver diagnosis interface <interface-type> <interface-number> – provides DMM information for troubleshooting .
2. Verify Link and Fiber: Ensure fiber connectors are clean, undamaged, and the local and remote modules have matching wavelengths.

Best Practices

• Periodically check SFP health to prevent unexpected link drops.
• Compare TX/RX readings against the module's specifications to detect degradation.
• If RX power is low, inspect fiber length, connectors, and cleanliness before replacing hardware.
• Ensure both ends of the fiber link use compatible SFPs with the same wavelength . By following these steps, you can accurately monitor and maintain the optical power of your switch ports, ensuring stable and reliable fiber connections.