View optical module DDM

DDM (Digital Diagnostics Monitoring) allows real-time monitoring of optical module parameters such as temperature, voltage, transmit/receive power, and laser bias current, accessible via CLI, SNMP, or vendor-specific tools.

Understanding DDM

DDM, also known as Digital Optical Monitoring (DOM), is a standardized feature defined by SFF-8472 that enables network devices to monitor the operational status of optical transceivers, including SFP, SFP+, QSFP, and QSFP+ modules. It provides real-time data on key parameters such as temperature, supply voltage, optical transmit power, optical receive power, and laser bias current, helping network administrators detect degradation or potential failures early . DDM data is typically accessed via the module's I2C interface and is interoperable across vendors .

Viewing DDM via Command-Line Interface (CLI)

For network devices like Huawei switches, you can use CLI commands to access DDM information:

1. Display basic transceiver information: display transceiver [interface-type interface-number | slot slot-id] This shows general module details .

2. View diagnostic DDM information: display transceiver diagnosis interface [interface-type interface-number] This command provides real-time DDM parameters, including temperature, voltage, and optical power .

For F5 BIG-IP systems, DDM can be enabled and viewed using the Traffic Management Shell (tmsh):

• Connect via SSH or serial console with root access.
• Enable DDM if disabled.
• Use tmsh commands to view DDM data for each interface, which includes transmit and receive power levels in mW or dBm .

Viewing DDM via SNMP

DDM information can also be accessed remotely using SNMP, which is useful for network monitoring tools:

1. Enable DDM on the optical module (usually enabled by default).
2. Discover the module using its IP or MAC address with an SNMP discovery tool.
3. Configure SNMP on the host device, including community strings for authentication.
4. Query DDM parameters using SNMP OIDs defined in SFF-8472. For example, to read the temperature of an SFP+ module: snmpwalk -v2c -c [community string] [module IP] .1.3.6.1.4.1.9.9.91.1.1.1.1.10 This returns the temperature in Celsius .

Key Parameters Monitored by DDM

• Temperature: Module operating temperature.
• Supply Voltage: Power supplied to the transceiver.
• Transmit Power (Tx): Optical output power.
• Receive Power (Rx): Optical input power.
• Laser Bias Current: Current driving the laser diode.

These parameters often include alarm and warning flags to alert when values exceed factory-set thresholds .

Summary

To view DDM information, you can use:

• CLI commands on the network device (vendor-specific).
• SNMP queries for remote monitoring.
• Vendor tools like tmsh for F5 or equivalent management interfaces.

DDM provides critical visibility into optical module health, enabling proactive maintenance and troubleshooting in modern optical networks .