WDM

[Fadil Paloi]

Hi I am doing simple WDM for 18 channels and when I change bitrate from 10 to 20Gbit/s after a certain length some of the cannels usually the last ones showing very low Q factor, so difference is very High two to three times lower can anyone tell me what I have to do to get similar Q factor for all the output channels.

[Aabid Baba]

Hello fadii,
Can you please upload your osd file or brief us about other parameters apart from bit rate ??
At the moment i would suggest you to use an optical amplifier with output gain. or you can increase the bandwidth of WDM MUX/Demux.
You can also try increasing the symbol rate. and for that matter you can also increase power of the system. It would be convenient if you upload your osd file.
Regards

[Fadil Paloi]

It is a simple WDM with 18 channels compensated with DCF and amplified with EDFA, depends on the bitrate starting from 50km up to 100km space between amplifiers, I have change all what you suggest but no results, for example for the length of 100km, Bitrate of 40Gbi/s, I can achieve Q factor of Q=16.5 for first output, Q=23 for the fifth output Q=19, for the ninth output Q=10.5 and the last one Q=6.8. Bandwidth of the Mux/Demux I have tried from 3*Bitrate, 2*Bitrate 1.5*Bitrate and same as bitrate to when I use it for the single user Q factor goes up to Q=80 but when it comes to multi users such as 18 channels I do not know what I can say. So please I need answer.

[FAYIQA NAQSHBANDI]

Hi Fadil

Does the 18 channel WDM system you have designed work well for a short distance and for 10 Gb/s data rate ?

The performance of the system is expected to change if you are increasing your data rate to 20 Gb/s and simulating it for long transmission reach.You will have to change different system parameters at the transmitter,reciever and in the fiber connecting the two.
Try increasing the launch power of all the 18 sources.
Check if you have properly defined the channels for your WDM MUX and DEMUX.
Use a spectrum analyser to check the power level of all the signals at different points in your design.

These are a few points you can use to trouble shoot your system

see if it helps

Regards

[Naazira Badar]

Hi Fadil..

Well yeah, that seems to happen especially when more than 4 channels are being used.
I believe changing the bandwidth of the WDM MUX/DEMUX can change the Q.F. of the channels you have an issue with.
Try reducing the bandwidth by a small value and check if anything improves. If an improvement is achieved, then you can decide the final acceptable bandwidth of your MUX/DEMUX.

Regards.

[Ranjeet Kumar]

Hi Fadil,
Here i am uploading osd file 32 channel wdm system with advanced modulation format of CSRZ using symmetric compensation technique and bit rate of 40 gbps for transmission distance varies from 60 km to 1500 km by just increasing the no of loops, upto 1200 km or more you will get good q-factor and Min. BER. use this as reference you can design for MDRZ AND DRZ modulation formats too.
it is very good design and complex one.

[Fadil Paloi]

THANK YOU

[Aabid Baba]

Hello Fadil,
You are welcome. Hope it would have helped you.
Regards

[Rajguru M. Mohan]

Hi Fadil Paloi,
First of all i suggest you to use symmetrical no. of channels like- 2,
4, 8, 16, 32, 64 and so on.
Because in all the design i have seen suggest to use symmetrical
number of channels.
As we also know that non-linearities effects increases as data rate increases.
Also dispersion and other losses increases.
So, lowering of q-factor and increament of BER is expected to occur.

I suggest you to use some advanced modulation formats like csrz, drz, mdrz and dpsk,
because it supports high data rate and long haul transmission.

Here i am uploading 32 channel CSRZ wdm system at data rate of 40 gbps.
Also use dispersion compensation techniques namely pre, post or symmetrical.
According to me i symmetrical dispersion compensation techniques is best of all three.

[umer ashraf wani]

this occurs because of power transfer among the different channels. the same effect can be witnessed by just analyzing the power at different frequencys.this effect occurs because of four wave fixing problem (FWM), scattering. this effect can be decreased by changing the refractive index which will give different delays(which leads to different group velocity) to different channels.
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj5ianNncDMAhWLVI4KHX-lClYQFggkMAA&url=http%3A%2F%2Fjpier.org%2FPIER%2Fpier73%2F13.07040201.Singh.S.pdf&usg=AFQjCNF1l4JThMdRAAkt3e1rYPVE2tAO_w&sig2=sPkUMHP0ZhnbO7MwgKZPjQ
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwj5ianNncDMAhWLVI4KHX-lClYQFggtMAE&url=http%3A%2F%2Fwww.optics.rochester.edu%2Fusers%2Fgpa%2Fnlfo_1h.pdf&usg=AFQjCNFXkkAAQUWVVUnHKmWTLnDJNfQvCg&sig2=Ak_Po2R3jUlk-VkqyjNbYQ
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwj5ianNncDMAhWLVI4KHX-lClYQFgg2MAI&url=http%3A%2F%2Fwww.ifsc.usp.br%2F~dispoptic%2FAulas2013%2FAgrawal-internet%2FPhotonics%2520West%2520Tutorial%2520-SPIE.pdf&usg=AFQjCNGOcTCbt-P84iotkmbPeNX3ukDH1w&sig2=-KTFVYuttRXjSmehbUx0lQ

[Hamza Ali Abbas Khan]

Hello Fady,
I would suggest you few things:
Use single mode fiber (SMF) with small cross section of light carrying area that may lead to increased power intensity inside the fiber.
Use of in-line optical amplifiers will result in a substantial increase in the absolute value of the power carried by a fiber.
The deployment of multi wavelength systems together with optical amplifier may help.
I hope this information is helpful to you.
Thanks

[Karan Ahuja]

Hi fady,
I agree with umer it is because of power transfer among the different channels. the same effect can be witnessed by just analyzing the power at different frequencies.
This effect occurs because of four wave fixing problem (FWM), scattering. this effect can be decreased by changing the refractive index which will give different delays(which leads to different group velocity) to different channels. I hope this will be of good help.
Regards

[Author]

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