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Signals Could Not Be Amplified by a PA Module Because the Default Wavelength of a Line Board Was Incorrect

Publication Date:  2012-07-25 Views:  45 Downloads:  0
Issue Description
When an SSN1SF64A board worked with a BPA board, signals could not be amplified by the BPA's PA module. That problem also occurred when an SF64A board substituted for the SSN1SF64A board. That problem, however, did not occur when an SL64 board of the V64.2b type was used.
Alarm Information
None.
Handling Process

1. Tested the output wavelength of the SSN1SF64A/SF64A board with an optical spectrometer. The measurement value was approximately 1560 nm, instead of the required 1550.12 nm.

2. Tests showed that the default wavelength of a line board could be changed even when the board software remained unchanged. The following conclusions were reached:

a. Set a correct wavelength for the SSN1SF64A/SF64A board through the debugging interface and found that the SSN1SF64A/SF64A board output a correct wavelength. The output wavelength of the board remained correct even after the board was reseated or a cold/warm reset was performed on the board.

b. Re-set an incorrect wavelength for the SSN1SF64A/SF64A board that had already output a correct wavelength, and found that the SSN1SF64A/SF64A board always output an incorrect wavelength even after the board was reseated or coldly reset.

c. Found that the SSN1SF64A/SF64A board output a correct wavelength if a warm reset was performed on the board.

Based on the preceding conclusions, it is suspected that I2C communication is not reliable during the power-on or cold-resetting process of a line board, resulting in the output of an incorrect wavelength due to an initialization failure. If a correct wavelength is set for a line board, the line board outputs a correct wavelength even when re-initialization due to power-off fails, because the optical module of the line board can remember a preset wavelength.

After a line board starts up, initializing an output wavelength is successful after a warm reset is performed on the line board, because I2C communication is normal in this case. 
Root Cause
The wavelength information of the line boards involved was incorrect.
Suggestions
None.

END