You can check an optical module's size, type, and specifications using device commands, diagnostic tools, or physical inspection.

Using Network Device Commands

For switches and routers, especially Cisco devices, you can use CLI commands to view detailed SFP or optical module information:

• Show inventory: Lists all installed modules with Product ID, Version ID, and serial number. Switch# show inventory
• Show transceiver details: Displays Digital Diagnostic Monitoring (DDM) metrics such as temperature, voltage, transmit (Tx) and receive (Rx) power, wavelength, and vendor information. Switch# show interface GigabitEthernet1/0/1 transceiver detail
• Show interface status: Confirms whether the port is up and the media type (SFP, fiber, copper). Switch# show interfaces status These commands help determine the module's operational parameters, including supported distances and optical power levels, which are critical for verifying the module's “size” in terms of reach and performance . For Huawei devices, the command is similar: display transceiver [interface | slot] This shows optical power, wavelength, transmission distance, and module type .

Using Operating System Tools

On Linux systems, you can use ethtool to query SFP modules:

ethtool -m eth0

This command provides detailed information such as:

• Connector type (e.g., LC)
• Transceiver type (e.g., 10GBase-SR)
• Supported fiber lengths for single-mode (SMF) and multimode (MMF)
• Laser wavelength
• Vendor name and part number

Physical Inspection

You can also check the module type and size by examining the module itself:

• Label markings: Single-mode modules are often labeled "SM" and multimode as "MM"
• Connector color: Yellow for single-mode, orange or aqua for multimode
• Manufacturer datasheet: Confirms maximum transmission distance and supported fiber type

Summary

To check the size and specifications of an optical module:

1. Use device CLI commands to read DDM/DOM data and interface status.
2. On Linux, use ethtool -m to get detailed module information.
3. Inspect the module physically for mode type and labeling.
4. Refer to the manufacturer datasheet for exact transmission distance and wavelength. These steps ensure you can verify the module's compatibility, operational health, and optical reach accurately.