WDM latest

[Dr. Dhiman Kakati]

Hello Everyone,
I am looking for some suggestion regarding WDM technologies as I want to work on it, so please anyone suggest what is the trending issue that I can go for implementing WDM and application in present scenario. What I can add from my own to have a good research. I am looking for some best papers regarding this. So I need your suggestion from you who are working in WDM. Also I would like to know about future of WDM or DWDM.

With Regards,
Dhiman Kakati

[umer syed]

hi dhimen,
so far i know about the future for the next genneration optical networks… i think OTDM (optical time domain multiplexing) in combination with the wavelength multiplexing are most important member of all other technologies…these are called as the hybrid networks..

dhimen i think there is tutorial on OTDM on optiwave site , you need to add that for diffferent wavelengths

with regards

[Dr. Dhiman Kakati]

Hello Umer Syed,
Thank you so much for providing with valuable information which I was looking for. I will definitely look for OTDM (Optical time domain multiplexing). Can you suggest me some research paper regarding this topic that you have studied and find it beneficial. Thanking you.

I am also looking for any other suggestion.

Regards,
Dhiman

[umer syed]

hi dhimen
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1284149&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D1284149
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=7184859
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1360239&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D1360239
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4809402&newsearch=true&queryText=hybrid%20pon
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4598384&newsearch=true&queryText=hybrid%20pon
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6507691&newsearch=true&queryText=hybrid%20pon

with regards

[Dr. Dhiman Kakati]

Hello Umer Syed,
Thank you so much for providing so many paper and should benefit my issue, I will definitely go through the links provided. Hope to get a good idea regarding my query.

Regards,
Dhiman

[varinder singh]

hi dhimen,
so far i know about the future for the next genneration optical networks… these papers will help you …in wdm topics…..you can use these papers to get the idea about wdm and itz future in the comming days……
i hope you will be satisfied with my response thanks
with regards

[Dr. Dhiman Kakati]

Hello Varinder Singh,
I am unable to find any more information about the topic, It is been already been given by umer syed.

Regards,
Dhiman

[varinder singh]

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1360239&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D1360239

[Dr. Dhiman Kakati]

Thank you so much varinder for providing the paper

Regards,
Dhiman

[SAHIL SINGH]

Hi Varinder and Umer syed,

Thanks for proviving the useful information.. Will surely try to look into the links posted by both of you… Hope Dhiman got the help needed he was looking for…

Thanks and Regards
Sahil Singh

[varinder singh]

yeah sahil……….i am sure that he will be able to get the idea about his topiv .
thanks sahil………….
with regards

[SAHIL SINGH]

Hi Varinder,

Lets hope that his query is resolved..

Regards
Sahil Singh

[Ranjeet Kumar]

Hi Dhiman,
The latest research in the fields of WDM/DWDM system includes:
1.Effective way to reduce the nonlinearities like Four Wave Mixing and Cross Phase Modulation so that we could achieve the spectral efficiency of 1 b/s/Hz or less, using various modulation formats.
2. We should use the concept of nonuniform channel spacing and nonuniform power assignment between adjacent channels of the DWDM system.
3. We should simulated increase the no. of channels beyond 128 channels.
4. We could reduce the channel spacing upto 25 ghz or smaller and increase the global data rate, to make more spectral efficient.
5. We could use some advanced modulation formats like CSRZ, MDRZ , OFDM.
Hope this will help you.

[Dr. Dhiman Kakati]

Hi Ranjeet Kumar,
Thank you so much for providing me with the answer to my question, this is very much application oriented and specific which I was looking for, Did you try using 25 GHz channel spacing, actually I am trying to put 25 GHz spacing but not getting a good result. So what are the aspects do i need to consider while designing a dense wavelength system, I was suggested to use Distributed feedback laser to use as it has lower sideband. and regarding the modulation scheme (owing to its various advantage such as bit rate and spectral bandwidth) to be implemented it is found to have more side lobes. In this case optical minimum shift keying is most advantageous as it is spectral efficient modulation scheme. but MSK is still lack in optisystem as the decoder is not there in optisystem. so any more suggestion regarding this.

Regards,
Dhiman

[SAHIL SINGH]

Hi Ranjeet Kumar,

Thanks for your response… In your comment you have mentioned about the effective way to reduce the non linearities like Four Wave Mixing… Can you please elaborate on this as to what it means ? Hope to hear from you soon

Regards
Sahil Singh

[Dr. Dhiman Kakati]

Hello Sahil Singh,
Fiber nonlinearity if specifically observed in the case of high launch power to the fiber, at high power the dielectric polarization of the fiber behaves nonlinearly with the electric field of the light. this gives rise to various phenomena such as cross phase modulation, four wave mixing, kerr effect etc. which is already known to you.
for minimization of four wave mixing you may find the following paper useful.

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=645380&abstractAccess=no&userType=inst

http://ieeexplore.ieee.org/Xplore/defdeny.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D1417009%26userType%3Dinst&denyReason=-134&arnumber=1417009&productsMatched=null&userType=inst

regards,
Dhiman

[Ranjeet Kumar]

Hi Dhiman,
To achieve dense wavelength division multiplexing (DWDM) systems with high spectral efficiency, it should operate at bit rates of 40 Gb/s per channel. For DWDM systems in which the data rate is greater than 10 Gb/s/channel, the dnegative effects of dispersion and nonlinearities must be managed. Dispersion management, which utilize DCF fiber, is a key technique that keeps the total accumulated dispersion low while suppressing most nonlinear effects. In dispersion-managed systems utilizing single-mode fiber (SMF) and dispersion compensating fiber (DCF), the positive dispersion of SMF can be compensated by the large negative dispersion of DCF.
You should use :
1. Symmetrical dispersion compensation techniques instsead of pre or post dispersion compensation techniques to reduce the effect of dispersion
2. You should use advanced modulation formats like.. CSRZ, DRZ, MDRZ.

I also have faced problem in designing 25ghz channel spacing DWDM system.

i would like to share the link :
http://www.sciencedirect.com/science/article/pii/S0030402608003276

Hope this may help you.

[Dr. Dhiman Kakati]

Hi Ranjeet Kumar, Thank you so much for providing with some more valuable information, you are suggesting me to increase the bit rate to 40 Gbps, nut want to add that i did simulation with DQPSK modulation format that to with only 10 Gbps for single polarization with direct detection because upto 10 Gbps the system was running properly but when I increase it to some 11 or 12 Gbps the performance degrades drastically and very much inclined to error. so I think there are some limitation for each modulation scheme. Moreover you have mentioned that the DWDM system to set a bit rate of 40 Gbps to have better output, if a system is not giving better how it can give better result at much higher rate such as 40 Gbps, I need some more explanation regarding this.

Thanking you,
regards,
Dhiman

[Ranjeet Kumar]

Hi Dhiman,
Here i am uploading 8 channel DWDM system using symmetrical compensation technique at data rate of 10 gbps.
In this design we have channel spacing of 100 ghz.
I use MDRZ modulation format.
you may change the data rate e.g. 20 gbps, 40 gbps and minimize channel spacing to 50ghz and 25 ghz .
And you will find the difference in results.
As we will decrease the channel spacing, results will degrade.

Seeking your response.

[Dr. Dhiman Kakati]

Hello Ranjeet Kumar,
for the valuable design, using advanced modulation format, it is really good to see some more advanced formats. It still uses 100 GHz band and I will try to modify as suggested by you. Thanks for the tremendus support.

Regards,
Dhiman

[varinder singh]

helo dhiman…..
you may change the data rate e.g. 20 gbps, 40 gbps and minimize channel spacing to 50ghz and 25 ghz .
And you will find the difference in results.i hope you will do it.
with regards

[Dr. Dhiman Kakati]

Hi Varinder Singh,
I tried reducing the channel/frequency spacing from 100 GHz but not getting a clearer output. Did you try any system with 50 GHz channel spacing, So if possible, Please upload the design file here.

Regards,
Dhiman

[Ranjeet Kumar]

Hi Dhiamn,
Yeah, i am suggesting to reduce the channel spacing to first 50ghz and find the results and then compare the Q-factor and BER to the previous one that is 100 ghz.
And finally you should reduce the channel spacing to 25 ghz and compare the results.
You could draw the graph by suing excel.
As i have mentioned earlier different factors which degrade the results namely: Increasing number of channels(users), Global bit rate, reducing Channel spacing and transmission distance by increasing no of fiber loops.
You could also see the difference in results when you will use different dispersion compensation techniques.

So, you will have different parameters by varying these one by one or simultaneously you will get different results.

[Dr. Dhiman Kakati]

Hi Ranjeet Kumar,
I tried to modify the system keeping 50 GHz spacing, but unable to get a better result, and setting a bandwidth of 50 GHz.

Regards,
Dhiman

[SAHIL SINGH]

Hi Dhiman kakati,
Thanks for posting such informative reply… I will surely try to follow the links as suggested by you in the previous posts of yours.. Thanks for your efforts and valuable time..

Regards
Sahil Singh

[Ranjeet Kumar]

Hi Dhiman Kakati,
What was the problem you were facing in the design of 50 ghz, for better results you should decrease data rate and also decrease number of loops so that transmission distance would decrease.
At receiver end you should change the cutoff frequency and filter order, because sometime these parameters create problems.
Try to change the parameters and use the values of parameters that is being used in the paper which i have posted.

[Dr. Dhiman Kakati]

Hello Ranjeet kumar,
firstly I want to say that the output optical spectrum at the WDM mux output is not clear, There is overlapping as the sidelobes have considerable power.

2ndly as suggested by you decreasing the bit rate and increasing the no of channels is same as a whole while total bit rate is concerned. So I think Better to keep the spacing 100 GHz and also same bit rate.

For cut of the Bessel Low pass filer cutoff was previously 50 GHz for 100 GHz WDM spacing, So for 50 GHz channel spacing at the optical domain what should be the cut off of the LPF used in electrical domain.

Regards,
Dhiman

[SAHIL SINGH]

Hi Dhiman Kakati,
Infact a very valid point put forward by Ranjeet about decreasing data rate as well as the number of loops… Try the suggestion of Ranjeet… I hope it will be of help to you…

Regards
Sahil Singh

[Dr. Dhiman Kakati]

Hello Sahil Singh,
Thank you for the response, try to put some information/point from your side that will be beneficial for us.

Regards,
Dhiman

[Rajguru M. Mohan]

Hi Dhiamn,
As we know WDM is the current favorite multiplexing technology for long-haul communications in optical communication
networks since all of the end-user equipment needs to operate only at the bit rate of a WDM channel, which can be chosen
arbitrarily, e.g., peak electronic processing speed. Hence, the major carriers today all devote significant effort to developing
and applying WDM technologies in their businesses.
Recent research interests in WDM networks include network
control and management, fault management, multicasting,
1818 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 18, NO. 10, OCTOBER 2000
physical-layer issues, IP over WDM, traffic grooming, and optical
packet switching, just to name a few.
In a wavelength-routed WDM network, a control mechanism is needed to set up and take down all-optical connections.
Studies have been conducted to examine different approaches to
protect WDM optical networks from single fiber-link failures.

And many issues and challenges in WDM system must be studied.

[Author]

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