SFP With DDM Function, What Is DDM?

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?
DDM is Digital-diagnostic-monitoring 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.