Bandwidth parameter for each component

[Aabid Baba]

I wish to ask that what is the significance of the Bandwidth parameter mentioned in the layout tab of respective components?
I also want to know why is it different for each component used ( say MUX and fiber bragg grating in my case ). if i am transmitting at 193 THz , the default bandwidth of MUX is 10GHz but at the same time the default bandwidth of fiber bragg grating is 125 GHz. Here i am confused because if 10GHz can accommodate 193 THz signal then why fiber bragg grating has 125 GHz. Shall i change the bandwidth of fiber bragg grating of increase bandwidth of Mux.??
Suggestions would be appreciated.
I am also attaching screenshots of the above mentioned two components herewith.

Attachments:

1. 

   fbg.jpg
   

[Aabid Baba]

here is the second screenshot of MUx.

Attachments:

1. 

   mux.jpg
   

[alistu]

Hi Aabid,

The bandwidth of a Multiplexer or a demultiplexer (the one in your second image) refers to the bandwidth of the filters used for each channel of the implemented WDM system, whereas the bandwidth in some other components such as amplifiers is the bandwidth of operation of that specific component.

Regards

[Aabid Baba]

Hi alistu,
Fine i agree that the bandwidth is that of a filter in that component but how can this component support a transmitted wavelength which is of the order of THz when the filter has bandwidth just in GHz. I think to support the transmitted frequencies the bandwidth should be large enough to accommodate all frequencies that lie in that range. This is what is actually confusing me.

Regards

[alistu]

To better explain this, I bring your attention to two parameters you need to set for the filter: The center frequency and the bandwidth. The bandwidth is related only to bandwidth of the signal, whether it is up-converted to 50 THz or 193 THz. The parameter that needs to change when the frequency of up-conversion changes is the “center frequency” of the filter.

[FAYIQA NAQSHBANDI]

Hi Aabid

I suggest you to change the bandwidth of your MUX to the same range at which you are transmitting your signals.Check your performance and compare it with when you were using 10 GHz.MUX is definitly limiting your bandwidth and by increasing the bandwidth of the MUX i believe you will see a good improvement in your performance.

Best Wishes

[alistu]

Hi Fayiqa,

After reading your suggestion I find it worth mentioning that the bandwidth depends on the bit rate and the coding scheme adopted for the system mostly. It is not as if when the center frequency is 50 GHz, bandwidth is 10GHz and when it is 193 THz, bandwidth becomes 192.06 THz for example (sum of the added frequency and the formerly used bandwidth).

Regards

[Aabid Baba]

Hi fayiqa,
Thank you for your suggestion. If you read my above comment you can see that is exactly what i am referring to. To support my transmitted signal’s wavelength i should make the bandwidth of my components such that they support the transmitted signals. If done so , our performance may increase because then every component would fall under same operating frequency and eventually bandwidth.
Regards

[alistu]

Hi aabid,

Please refer to this very simple image I have attached. the axis shows frequency in both figures. In the first figure, the center frequency of the same signal is f1 and in the second, it is f2. Even though f2 is greater than f1 in the image, the bandwidth of the signal in both positions is the same. I hope this is clear.

Regards

Attachments:

1. 

   BW-vs-Center-frequency.jpg
   

[Aabid Baba]

Hello Alistu,
Thanks for the response.Indeed very explained. I implemented a simple design in optisystem and there i checked the same by changing the bandwidth of the above mentioned components. You are very right, It works the way you had explained. Changing bandwidth does not make a point. I agree with you, frequencies may change but bandwidth would remain same.
Thank you so much for clearing my doubts.

With regards

[alistu]

You’re welcome Aabid.

Regards

[Naazira Badar]

Hi Aabid, which are the components whose bandwidth you changed before simulation? The LASER?

Regards.

[Aabid Baba]

Hello naazira,
I changed the bandwidth of MUX and Demux for a simple WDM system. The output i observed on the visualizer was something i had never seen before. I can post the screenshot of the results. It lead me to conclusion that Alistu is right in saying that bandwidth of signal will remain same even though you change its frequency.
Regards

Attachments:

1. 

   Capture111.jpg
   

[Naazira Badar]

Well Aabid..
Did the performance change when you increased the bandwidth of the MUX/DEMUX for the same set of signal frequencies you tested the system for?

Regards

[Aabid Baba]

Naazira, actually the screenshot i posted above is the performance of the system when i changed the bandwidth of MUX and Demux. Before changing the Bandwidth of mux and Demux , the performance was way way better but after changing the Bandwidth i saw something very unusual as you can also notice in the screenshot.
Regards

[Naazira Badar]

Hi Aabid..
Did you keep the test signal frequencies constant for all the values of bandwidth you kept for MUX/DEMUX?
Because when I was trying to understand the effects of changing the BW of MUX/DEMUX, the performance was better when I increased its BW. I think that’s because distortion is reduced by increasing the MUX/DEMUX BW.

Regards.

[Aabid Baba]

Yeah naazira ,
I kept the test signal frequencies constant for all the values of bandwidth for MUX/DEMUX. It was a simple WDM system on which i implemented this logic. I believe Alistu had a point. You can refer to the comment #30857 where he has given a logical statement.
I too believed system performance should increase by doing so but i did not happen.

Regards

[Naazira Badar]

Well in that case, I ‘d like to recheck my observation.

Regards.

[Aabid Baba]

Yeah sure.
You can recheck it on a simpler system. Please share your observations here. May be you observe something different.

Regards

[Naazira Badar]

Aabid, I had checked on a 8 channel WDM system. When I changed MUX /DEMUX bandwidth from 10 GHz to 100Ghz, the performance was seen to be improved. How many channels had to you used?

Regards.

[alistu]

Hi Naazira,

Could you please upload your design if it is possible? The increase in bandwidth may lead to increase in system performance in many cases, but it cannot be concluded that this has to do with carrier frequency, and I believe I can explain it better if your implementation file is available.

Regards

[Aabid Baba]

Hi naazira,
Actually i had a confusion about accommodation of signal frequencies within the bandwidth. I had increased the bandwidth way too much. I was of the opinion that my component bandwidth should be same as transmitted signal frequencies so that it supports their transmission where i was wrong but after Alistu replied the doubt got cleared and the result screenshot was pertaining to that bandwidth.

Regards

[Fadil Paloi]

Hi i am using simple WDM system with all the modulation formats such as NRZ , RZ CSRZ and CRZ allwayes the best MUx/DeMax Bandwidth for the 18 channel system I use 2*Bit-rate which it works perfect

[Aabid Baba]

Hello fadil,
I didn’t understand it. Are you trying to ask or say it??
And we are talking of changing bandwidth of multiplexer and and its effects on the system performance correspondingly. Please suggestions are always welcomed.
Regards

[Ranjeet Kumar]

hi,
I agree with alistu sir that bandwidth of mux is that of its filter.
The reflection bandwidth of a fiber grating, which is typically well below 1 nm, depends on both the length and the strength of the refractive index modulation. The narrowest bandwidth values, as are desirable e.g. for the construction of single-frequency fiber lasers or for certain optical filters, are obtained for long gratings with weak index modulation.

As the wavelength of maximum reflectivity depends not only on the Bragg grating period but also on temperature and mechanical strain, Bragg gratings can be used in temperature and strain sensors.

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6945243

[Aabid Baba]

hello ranjeet,
We are not talking about the fiber bragg grating here but the bandwidth of WDM mux and its effects on the overall performance and performance of the component itself. Please refer to the topic first. I guess you misread the topic but anyway replies and suggestions are always appreciated.

Thanks and regards

[FAYIQA NAQSHBANDI]

Hi all,
I am designing or implementing a TWDM PON system. Now what i want to mention hare is that when i previously had increased the bandwidth of MUX (ideal) and the filters i was using ( fabry parot and low pass bessel) , the performance was better than what i ‘d noticed before. I had kept the value around 100 GHz instead of 10 GHz vch usually is the case in optisystem.
Increasing b.w does affect the performance.
thanks and regards

[Aabid Baba]

Hello fayiqa,
Yeah i agree to some extent the performance does get better on increasing the bandwidth of the mux and corresponding components. We have already discussed it. You may check previous post/comments to get an idea what has been discussed and in what context. i hope ou would understand.
Anyways thanks for the reponse.

Regards

[Author]

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