Hi,

I suggest to discuss one more interesting subject:

With development of the coherent optical channel and methods of phase shift keyings (for example, QPSK and QAM) in the equipment WDM the question of the analysis of parameters acquires new features.

Former methods of the analysis (the optical spectrum analyzer and spectrograms) cant look at phase statuses. On spectrograms such channels look as one channel. It can be done up to an eye diagram which receives the special analyzer.

How it seems to you, in practice telecom operators will need acquisition of such instruments for maintenance? In addition it is required also training of staff. Or such instruments will be used only in laboratories, and telecom operators dont need to know about influence of phase statuses at each other?

It is interesting to hear judgement of employees of telecom operators and judgement of Huawei.

Example of the common impairments (EXFO):

Hi,

After checked it with Huawei system engineer,  that engineers in employees of telecom operators only need to check the BER.

Hope it will help. If you have different opinion or more questions, keep on replying in this topic.

Thank you ~!

 

Usually, for maintenance, such special instruments does not need. Its really enough to check FEC before and after correction. And received optical power also. :)

Thanks for comments (#2, #3)! ! !
Instead of can be any hidden deteriorations between phases which wont give FEC or BER deterioration right now, but in the future can affect operability of the channel potentially?
That is internal influence of phases at each other can be read stationary process to which in case of maintenance it is possible not to pay attentions?

Hi,

An EXFO meter can measure only phase deterioration of each signal before the oDSP chip equalization in a coherent system. However, such deterioration does not indicate the actual receive performance, because the oDSP chip will mitigate or eliminate the amplitude and phase deterioration of each signal to achieve better performance. The better performance will be indicated by the BER.
The following draws an analogy. The transmission effect is similar to a distorting mirror, and the oDSP chip equalization is similar to an image restoration process. After being distorted by the distorting mirror and restored by the oDSP chip, the normal image will be received at the end. The EXFO meter measures only the image distorted by the distorting mirror, and this image is different from the normal image at the receive end.
Therefore, you are advised to pay more attention to the BER rather than the intermediate process. The intermediate process may represent system performance in a certain way, but does not indicate the final result.

 

Hi,

Well, very thanks for the detailed explanation!!!