You can check an optical module's bandwidth by querying its type, speed, and DDM diagnostics using CLI commands on your network device.

Using CLI Commands

Huawei Devices

On Huawei switches, you can use the following commands:

• display transceiver [interface interface-type interface-number | slot slot-id] – shows detailed information about the optical module, including type, speed, and operational parameters .
• display transceiver diagnosis interface [interface-type interface-number] – provides Digital Diagnostic Monitoring (DDM) data such as optical power, temperature, and voltage, which helps verify module performance and bandwidth capability .

Cisco Devices

For Cisco switches and routers:

• show inventory – lists all installed SFPs with Product ID, Version ID, and serial number .
• show interface <interface-name> transceiver detail – displays full DDM metrics including transmit/receive power, temperature, voltage, and module type, which indicates supported bandwidth .
• show interfaces status – shows port speed and duplex settings, confirming the module's operational bandwidth .

Aruba Devices

On Aruba switches:

• show interfaces <interface-name> – displays interface configuration, transceiver type, link status, and speed (e.g., 25G, 10G), .
• Real-time DDM diagnostics can be checked to monitor TX/RX optical power and ensure the module operates within its rated bandwidth .

Fortinet Devices

For Fortinet switches:

• get switch modules detail – reads EEPROM data including transceiver type, transmission distance, and manufacturer details .
• get switch modules status – shows real-time DDM values and alarm thresholds, helping verify that the module is performing at its rated bandwidth .

Key Points to Verify Bandwidth

1. Module Type and Speed – The module's type (e.g., SFP, SFP+, QSFP28) usually indicates its maximum supported bandwidth.
2. Port Speed – Check the interface speed in the CLI to confirm the module is operating at its rated bandwidth.
3. DDM Diagnostics – Monitor TX/RX optical power, temperature, and voltage to ensure the module is functioning correctly and can sustain the expected data rate.
4. Certification and Compatibility – Using certified modules ensures accurate bandwidth reporting and reliable performance . By combining these commands and diagnostics, you can accurately determine the bandwidth capability and operational status of any optical module in your network.