View optical module receive power information

You can view the receive (RX) power of an optical module using device-specific commands that display real-time transceiver diagnostics.

General Concept

Optical modules transmit and receive data using light signals. RX Power indicates the strength of light received from the remote device, measured in dBm. Monitoring RX Power is critical because low values can cause intermittent link issues, packet loss, or interface flapping, even if the link appears up. Most modern SFP or QSFP modules support Digital Optical Monitoring (DOM) or Digital Diagnostic Monitoring (DDM), which provides real-time RX and TX power, temperature, voltage, and bias current readings .

Huawei Devices

On Huawei switches or routers, you can use the following command:

display transceiver verbose

or for a specific interface:

display interface transceiver verbose

The output includes:

• Current RX Power (dBm) – the received optical power
• Current TX Power (dBm) – the transmitted optical power
• Additional info: transceiver type, wavelength, vendor, temperature, voltage, and alarm thresholds .

Example snippet:

Current RX Power (dBm): -3.07Current TX Power (dBm): 0.12Temperature (°C): 30.9Voltage (V): 3.28

This allows you to verify whether the RX Power is within the acceptable range defined by the module's specifications.

Cisco Devices

On Cisco switches, you can check optical power using:

show interface

or for all interfaces:

show interface status

The output displays:

• Transmit (TX) power – light leaving the switch
• Receive (RX) power – light arriving from the remote device
• Link status and traffic statistics for troubleshooting .

Extreme Networks Devices

For Extreme switches, you can view RX Power and other module diagnostics using the DDM information:

• Query the port or omit the port number to see all ports.
• The output includes real-time TX/RX optical power, temperature, voltage, and alarm thresholds. A status of "Normal" indicates all parameters are within valid ranges .

Best Practices

• Regularly monitor RX Power to detect degrading fiber links or failing transceivers.
• Compare RX Power against the module's low/high thresholds to ensure proper operation.
• Use device-specific commands to automate monitoring or integrate with network management systems.
• Be aware that RX Power can fluctuate due to fiber length, connector quality, or environmental factors.

By following these procedures, you can effectively monitor and maintain optical link quality, ensuring stable network performance.