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The problem of high temperature on MUX or DEMUX ICTEMP due to working functioning principle of AWG module

Publication Date:  2012-07-25 Views:  117 Downloads:  0
Issue Description
Customer use a network based on OSN 6800 and noticed that all M40/D40 boards report performance parameter ICTEMP at the range 70-85 degrees. So he was affraid that high temperature can damage eqiupment and raised fan speed to cool down boards but no changes obtained. So corresponding service request was created.

Alarm Information
No alarm.

Handling Process
The optical arrayed waveguide grating module (AWG) is used to MUX/DEMUX signal and it is greatly dependent on the temperature: the changes of the temp. on 1 degree results in a wavelenght shift on 0.05 nm. So at the production stage the module is calibrated: the working temperature is fixed when optical spectrum satisfy WDM standart. The working deviation of the temperature is +/-5 deg. from the working temperature and it is written to the board software. Temp. range can be checked using command :cfg-get-almth:bid,1,1,module_tmp.
At the normal working stage the AWG module is heated on board, so external temperature changes (environment or fan cooling mode) do not affect on module stability.
If the module temperature exceeds ranges the wavelenght shift exceeds 0.25 nm and the service will be affected. So the alarm MODULE_TEMP_OVER generated.

Root Cause
During SR troubleshooting it was found that there are no temperature alarm on equipment, the temperature of all board (BDTEMP) is at 25-45 degrees range, and environment temperature are within 20-25 degrees. At the same time only ICTEMP performance was relatively high.

Usually the temperature of AWG is high (60-85 degrees), so if there is no MODULE_TEMP_OVER alarm the board is working normally. Every board has its own ICTEMP working ranges that can be checked by :cfg-get-almth:bid,1,1,module_tmp command.