This case describes how to determine the factors that affect the OSNR by using the ANT30 tester.
Symptom
During a test of one OptiX BWS 1600G project, the ANT30 tester is used to test the optical power and OSNR of each channel. It is found that the frequency spacing based on which the OSNR is tested for different sites is different, and it keeps changing (it may be 112.5 GHz, 50 GHz, 75 GHz or other values at different time). As a result, the OSNR value is affected. But in fact the standard frequency spacing is 50 GHz in this network. Therefore, in this case, the settings of the ANT30 tester are adjusted so that the frequency spacing is always 50 GHz. After the settings are adjusted, however, the OSNR performance is still unstable, and the frequency spacing still fails to meet the specification requirement.
Cause Analysis
The reason why the OSNR performance is not improved after the settings of the ANT30 tester are adjusted is that the ANT30 tester uses the default values of a single station and the default values keep unchanged even if an attempt to change them is made.
The procedure for handling the problem is as follows:
Procedure
- Adjust the settings of the ANT30 tester to ensure that the frequency spacing is 50 GHz. Then, select Configuration from the menu in the screen of the ANT30 tester, and then double-click Average Value and increase the value by four points, so that the optical power and OSNR of each channel are optimal.
- Select Table to query the results.
- Click
and wait until ANT30 test finishes scanning the wavelengths to obtain the correct OSNR value. Do not click 
because this button is used to query the default values of a station and you will lost all existing settings of the ANT30 tester. - The number of the scanned wavelengths is displayed on the left of the ANT30 tester screen. The number depends on the Average Value set through the Configuration menu. For example, if the Average Value is 5, the scanning stops after five wavelengths are scanned.
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