What Are DOM and DDM? Monitoring Your Optical Transceivers
DOM/DDM reads live TX/RX power, temperature and voltage out of every modern transceiver. What the numbers mean, the commands to read them on major platforms, and how to use them for preventive maintenance.
Two names, one interface
DOM (digital optical monitoring) and DDM (digital diagnostics monitoring) are the same feature under two names: the real-time telemetry channel defined by the SFF-8472 management interface for SFP-class modules. Every modern transceiver — including everything in the Fibertrixa catalog — carries a digital diagnostics memory that the switch polls over I²C. The names DOM and DDM are used interchangeably by Cisco, Huawei, MikroTik and others — the interface and the readout are identical either way.
What the numbers mean
A DOM readout reports five live values plus the module's alarm and warning thresholds for each: transmitted power (dBm), received power (dBm), laser bias current (mA), internal temperature (°C) and supply voltage (V). Received power is the workhorse: it tells you instantly whether the far end is transmitting, how much the fiber is attenuating, and whether the signal lands inside the receiver's rated window.
Reading DOM on major platforms
Every major network OS exposes the same data through one command:
| Platform | Command | Notes |
|---|---|---|
| Cisco IOS/IOS-XE | show interfaces transceiver detail | Per-port DOM table with thresholds |
| Huawei VRP | display transceiver interface <port> verbose | Includes diagnosis info section |
| MikroTik RouterOS | /interface ethernet monitor <port> once-sfp | One-shot DOM readout per port (recent RouterOS v7 releases) |
| Linux (any vendor) | ethtool -m <iface> | Dumps the full SFF-8472 diagnostic page |
Using DOM for preventive maintenance
Three patterns catch most field failures before they take the link down. A slow RX power decline over weeks means a degrading connector or splice — clean and re-mate before it crosses the alarm threshold. A sudden 3–5 dB drop usually means a dirty or damaged ferrule; check the patch cord first. Rising bias current on the TX side signals an aging laser — plan replacement before it hits the alarm. Logging DOM values monthly turns these from emergencies into scheduled work orders.
DOM on our modules
Every optical module in the Fibertrixa catalog implements the SFF-8472 diagnostics interface and works with the commands above on compatible platforms. If you are standardizing monitoring across a mixed-vendor estate, send us the platform list — we confirm diagnostics behavior per model before you order. See also our quality and compatibility process.