Usually when we buy SFP transceivers, we will have options with its DDM functions, so what is DDM? Obviously a SFP with DDM is high-ender than one which without DDM functions. What the DDM use for?
What’s DDM/DDM?
DDM is Digital-diagnostic-monitoring (this feature is also known as digital optical monitoring (DOM)) which provides a user with critical information concerning the status of the transmitted and received signals. This approach allows for better fault isolation and error detection.
Digital diagnostics monitor the SFP module’s temperature, receiver power, transmitter bias current, and transmitter power. Usually, the output of the physical value of each parameter is an analog voltage or current from the Trans impedance amplifier, the laser driver, or the post amplifier. Engineers use ADCs to digitize those physical values. With the digitized value, a microcontroller can then either process data as part of a control loop, trigger an alarm, or just record the data into a register.
The features of Digital Diagnostic Monitoring:
1. Monitoring module operating temperature
2. Monitoring module operating voltage
3. Monitoring module operating current
4. Display module factory version.
Through real-time monitoring the module internal operating voltage and temperature, allowing the system administrators to find out some potential problems :
1) If Vcc voltage is too high, it will breakdown CMOS device; If Vcc voltage is too low, the laser does not work.
2) If received power is too high, it will damage the receiver module
3) If Working temperature is too high, it will accelerate the aging of the device.
What’s more, it can monitor the circuit and the performance of the remote transmitters by monitoring the received optical power meter.
Digital diagnostics monitor the SFP module’s temperature, receiver power, transmitter bias current, and transmitter power. Usually, the output of the physical value of each parameter is an analog voltage or current from the Trans impedance amplifier, the laser driver, or the post amplifier. Engineers use ADCs to digitize those physical values. With the digitized value, a microcontroller can then either process data as part of a control loop, trigger an alarm, or just record the data into a register.
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