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DWDM System

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(joined June 2015)
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Hi everyone,
I am having problem in designing DWDM system with channel spacing of 25 GHZ or 50 GHZ.
I have designed DWDM system with 100GHZ channel spacing, but find no results when when i decrease Channel spacing to
25 GHZ. I have used symmetrical compensation technique with different advanced modulation formats MDRZ, CSRZ and DRZ.
Following parameters used are 40gbps bit rate, variable transmission length.
We use advanced modulation formats because CSRZ has narrow optical spectrum then the conventional RZ format
and high tolerance to group velocity dispersion (GVP) and mixed effect of self phase modulation (SPM).
DRZ transmitter of their optical modulation bandwidth DRZ format is very
attractive. It can be compressed to the data bit rate B that
is half- bandwidth of NRZ format 2B.
How could i reduce channel spacing.
Suggest me some ways so that i could get the expected results.
Here i am uploading the osd file of DRZ DWDM system.

Seeking your response.

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Responses (30):

    • #37189
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      Remo De Suza
      Participant

      Hello Rajguru
      What is the exact problem you are facing?

      Regards

    • #37203
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      Rajguru M. Mohan
      Participant

      Hi nagesh kuknoor,
      I have used symmetrical dispersion compensation technique in my design.
      Although i have used all three dispersion compensation techniques namely pre, post and symmetrical.
      But Symmetrical dispersion compensation technique provides better results then other too.
      so, i opted this.

      Hope you will understand.

      Regards,
      Rajguru

      • #37237
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        nagesh kuknoor
        Participant

        Hello Rajguru,
        Thanks for sharing your details. I was asking what technique you are using like which dispersion compensation technique are you using.
        Looking for your response.

        Regards

    • #37204
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      Rajguru M. Mohan
      Participant

      Hi all,
      I apologize for you inconvenience in opening the file which i have uploaded.
      But i find any difficulties in opening the osd file, as i am also using optisystem 14.

      Regards,
      Rajguru

    • #37295
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      shafeen al yasin
      Participant

      Hi Rajguru,
      It may be because you have designed that file in optisystem 13 i guess that may be the reason. I hope your issue gets solved.

      Regards
      Shafeen

    • #37315
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      Manoj Kumar
      Participant

      Hi Rajguru and shafeen,

      I believe there is some sort of a compatibility issue between the optisystem versions 13 and 14…..

      Regards

    • #37317
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      Manoj Kumar
      Participant

      Hi Shafeen,

      I believe you are using optisystem 14 as previously mentioned.. then i dont believe compatibility is an issue as Rajguru is also using the same version..

      Regards

    • #37642
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      Rajguru M. Mohan
      Participant

      Hi Manoj,
      A good quality transmission with WDM systems goes with larger channel spacing, to be careful to
      not excessively increase to avoid nonlinear effects and There is a logical increase of the quality factor.
      we increase the channel spacing more the link quality get better and the
      BER decreases.
      Conventional WDM and DWDM uses increased channel spacing to allow less sophisticated and thus cheaper transceiver designs.
      The small channel spacing allows to transmit simultaneously much more information.
      The channel spacing, in GHz, relates to the optical wavelength as follows: A spacing of 200 GHz corresponds to about 1.6 nm, 100 GHz corresponds to about 0.8 nm, and 50 GHz corresponds to about 0.4 nm channels spacing. Most commonly 50 GHz follows 100 GHz, although attempts at 75 GHz and 37.5 GHz show up in literature. While there is nothing magical about any of these numbers, it seems likely that 50 GHz will be the next logical step below 100 GHz. Using a channel spacing of 50 GHz (0.4 nm) allows 45 channels to occupy only 17.5 nm of optical bandwidth. This greatly simplifies the requirement for optical amplifiers in the system. Fiber increases in channels per fiber would likely lead to the use of 25 GHz spacing. Designing the optical demultiplexer to separate the signals at the receive end defines the greatest challenge in closely spaced optical channels.

      Regards,
      Rajguru

      • #37644
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        Domail Singh
        Participant

        Hello Rajguru
        Thank you for the information. It is very encouraging and i highly appreciate your efforts for coming up with these important points.

        Regards
        Domail

      • #37647

        HELLO ALL..

        I agree with Rajguru here..The channel spacing should be minimum as i had told earlier too. I hope this would help you.

        Regards
        FAYIQA

        +1
    • #37648
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      Manoj Kumar
      Participant

      Hi Rajguru,

      Thanks for the information…

      Regards

    • #37689
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      Rahul Tiwari
      Participant

      Hi Rajguru,

      Thanks for so much of useful information…

      Really appreciate your efforts…

    • #38373
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      Rajguru M. Mohan
      Participant

      Hi Fayiqa,
      You have talkrd about non-linearites effect.
      as far as i know,
      With the use of amplifiers the optical power level can rise to point where non-linear effects occur:
      Four wave mixing (FWM): spurious components are created interfering with wanted signals
      Stimulated Raman Scattering (SRS)
      Non-linear effects are dependent on optical power levels, channels spacing etc:
      When channel spacing decreases both Four wave mixing (FWM) and Stimulated Raman Scattering increases.
      While when channel spacing increases both Four wave mixing (FWM) and Stimulated Raman Scattering decreases.

      And Four wave mixing (FWM) causes Interference between wanted signals and hence Power is lost
      from wanted signals into unwanted spurious signals.

      Thanks

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