SNR S2989G-48TX [114/553] Brief introduction to ddm

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S2989G-24TX Operation Manual Chapter 2 Layer 2 services

Configuration

2.12.1.1 Brief Introduction to DDM

DDM (Digital Diagnostic Monitor) makes the detailed digital diagnostic function

standard in SFF-8472 MSA. It set that the parameter signal is monitored and make it to

digitize on the circuit board of the inner module. After that, providing the demarcated result

or the digitize measure result and the demarcate parameter which are saved in the

standard memory framework, so as to expediently read by serial interface with double

cables.

Normally, intelligent fiber modules support Digital Diagnostic function. Network

management units is able to monitor the parameters (temperature, voltage, bias current,

tx power and rx power) of the fiber module to obtain theirs thresholds and the real-time

state of the current fiber module by the inner MCU of the fiber module. That is able to help

the network management units to locate the fault in the fiber link, reduce the maintenance

workload and enhance the system reliability.

DDM applications are shown in the following:

1. Module lifetime forecast

Monitoring the bias current is able to forecast the laser lifetime. Administrator is able

to find some potential problems by monitoring voltage and temperature of the module.

（1） High Vcc voltage will result in the breakdown CMOS, low Vcc voltage will result in

the abnormity work.

（2） High rx power will damage the receiving module, low rx power will result that the

receiving module cannot work normally.

（3） High temperature will result in the fast aging of the hardware.

（4） Monitoring the received fiber power to monitor the capability of the link and the

remote switch.

2. Fault location

In fiber link, locating the fault is important to the fast overload of the service, fault

isolation is able to help administrator to fast locate the location of the link fault within the

module (local module or remote module) or on the link, it also reduce the time for restoring

the fault of the system.

Analyzing warning and alarm status of real-time parameters (temperature, voltage,

bias current, tx power and rx power) can fast locate the fault through Digital Diagnostic

function. Besides, the state of Tx Fault and Rx LOS is important for analyzing the fault.

3. Compatibility verification

Compatibility verification is used to analyze whether the environment of the module

accords the data manual or it is compatible with the corresponding standard, because the

module capability is able to be ensured only in the compatible environment. Sometimes,

environment parameters exceed the data manual or the corresponding standard, it will