05 Mar 10G SFP Digital Diagnostic Monitor function overview

A modern transceiver, including a 10G SFP transceiver, could not be imaginable without Digital Diagnostic Monitor approach that allows specialists to promtly isolate faults and errors in its operation. DDM monitors SFP module’s temperature, receiver and transmitter power, transmitter bias current and supply voltage as well as detects the threshold values for these parametres. A detailed specification of this approach can be found as SFF-8472 Specification made by SFP Committee.

In real-time monitoring transceiver values firmly relies on their accurancy. A 10G  SFP transceiver parameter accurancy is defined in SFP-8472 Specification:

 

Voltage:±3%;

Bias current: ±10%;

Temperature: ±1.5~3℃;

TX power:±1.5~3db.

RX power:±1.5~3db.

 

Another important matter in DDM function overview is the potencial problems that can be found while monitoring the parameters of the transceiver. Looking on the supply voltage parameter, two major problems can be seen: whether the supply voltage is too high or too low. If the voltage is too high, it will breakdown CMOS device, but if the voltage is too low, the laser will not work properly. Another problem, that can occure the transceiver is if the received power is too high. In this case, it will damage the receiver module. Third parameter that should be taken in notice is the working temperature. If the value is too high, it will accelerate the aging of the device.



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