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How to read optical module information on a network card on Linux systems

Time: 2023-04-19
        In addition to independent devices such as switches and routers, optical modules can also work on network adapters (commonly known as network cards). For optical modules used on switches, we read their information via brand-specific terminal commands. This guide introduces how to read optical module information when it is installed on a network card in a Linux system.
        This example uses the Moduletek SFP-10G-LR module connected to an Intel X520 network card.
Schematic diagram of the optical module connected to the server NIC
Figure 1: Schematic Diagram of Optical Module Connected to Server Network Card
1. Check Optical Module Status
        Execute the command ethtool devname to view detailed interface and optical module status:
        The output includes interface rate, module rate, module link status (Link detected: yes is a prerequisite for the optical module to work normally), and interface configuration information.
        Note:  devname refers to the network card/port name, usually expressed as ethX (e.g., eth0) or pXpX (e.g., p4p1). You can view it via the ip addr or ifconfig command.  It can also be determined by the slot number on the server panel. For example, p4p1 indicates the first interface of the fourth slot. 
2. View Module Identification and DDM Monitoring Data
        Execute the command ethtool -m devname to read optical module information on the target network card interface. Note that some network cards do not support this command.
        The output is divided into two categories:
    • Optical Module Identification Information: Includes module type, wavelength, transmission distance, serial number, vendor name, etc., derived from pre-written encoded data in the module.
    • DDM (Digital Diagnostic Monitoring) Data: Covers real-time diagnostic metrics and their threshold ranges. Focus on key parameters such as transmit optical power, receive optical power, temperature, and current to verify whether the optical module operates normally on both ends of the link.
        Moduletek provides optical modules compatible with various brands of network cards. Welcome to place your orders!
        If you have any questions about the above content, please contact us via email: sales@moduletek.com
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