DCF compensation

[Khadija Omran]

Hi ..
Are there limitation for length of DCF ( dispersion compensating fiber) ?
Means what’s the max length and min length of DCF ?

And Why when use it must the SMF length is 5 times the length of DCF ?

Thanks 🙂

[Dr. Dhiman Kakati]

Hi Khadija,
Where did you find “SMF length is 5 times the length of DCF” I am not sure about these. I am attaching here with a paper that calculates BER and q-Factor and finds best result for 90 km SMF with 12 km DCF. Please have a look.

regards,
Dhiman

Attachments:

1. IJEIT1412201206_25.pdf

[jyoti raina]

Hello Khadija mam..
i think its up to our requirement.. you should check some standard paper for the standard maximum and minimum values of the dispersion compensation techniques..
It should basically depend on the application of system.. I suppose cost will be the factor that will decide the maximum value..minimum can be anything i suppose..
With Regards
jyoti raina

[Dr. Dhiman Kakati]

Jyoti has mentioned one useful point that the implementation length of DCF is application Specific.

Regards,
Dhiman

[jyoti raina]

Hello Dhiman Sir..
Thanks for your appreciation.

With Regards
JyotimRaina

[SAHIL SINGH]

Hi Khadija,

I agree with both Jyoti Raina and Dhiman that the implementation length of Dispersion Compensating Fiber is application Specific… Also it has been rightly pointed out that cost will be an important factor.. Hope this helps

Regards
Sahil Singh

[burhan num mina llah]

Hi Khadija

I agree with Dhiman that there is no restriction like length of SMF is 5times that of length of DCF.. And the minimum and maximum length of DCF should be application specific.. For your reference i am attaching a link for a paper that has optimized the length of DCF for minimum BER and respective Q-factor..

http://www.ijeit.com/vol%201/Issue%206/IJEIT1412201206_25.pdf

Regards

Burhan

[syed fareed]

Hi khadiji
i think it application dependent.
with regards
syed fareed

[Remo De Suza]

Hello Khadija Omran.

I agree with what all other forum members have said so far. I agree with Dhiman saying that there is no restriction like length of SMF is 5times that of length of DCF. I also agree with Jyoti raina and Burhan num mina saying that the minimum and maximum length of DCF should be application specific and should be dependent on the design characteristics. I hope this will help you for better understanding.

With regards
Remo De’Suza

[burhan num mina llah]

Hello Remo

Thanks for appreciating.. I hope it helps khadhija to some extent to get through the issue..

Regards

Burhan

[Remo De Suza]

Hello Burhan Num Mina.

You are welcome. It has been my pleasure discussing things with you people here. I am really thankful to optiwave forum indeed it has been helpful.

With Regards
Remo De’Suza

[Khadija Omran]

Dhiman , jyoti raina , Sahil Singh , Burhan , syed , and Remo
Thank you for all , I agree with you in theory .. but in the optisystem program when use the length of DCF 24km , must the length of the SMF is 120 km .. Or SMF = 150 km must DCF =30 km , and so on .. Otherwise the the signal is distorted ..

[Dr. Dhiman Kakati]

Hi Khadija Omran,
I would suggest you not to use so long fiber in either cases but try to use loop control and pur SMF of 20-30 km and respective DCF this should give you best results. Further you can use optical amplifier for attenuation compensation.

Regards,
Dhiman

[jyoti raina]

Hi mam..You are welcome..

[SAHIL SINGH]

Hi Khadija,

You are welcome and i thank you for your appreciation… I think you are clear on theoretical aspect …. Further try to look into the suggestions of Dhiman in the previous post.. It surely will be of help.. Also thanks Dhiman for providing the useful information..

Regards
Sahil Singh

[love kumar]

hi… i think length of DCF is depend upon the dispersion amount due to SMF .. basically it is calculated with relation L1D1+ L2D2= 0
where L1= length of SMF
D1= dispersion slope in SMF
L2= length of DCF
D2 = dispersion slope in DCF

and i am agree with dihman that avoid to use long DCF .. instead loop concept give better results

[Ranjeet Kumar]

Hi Khadija Omran,
As we know that during the propagation of a pulse through the fiber, the group velocity dispersion (GVD) changes the frequency across the pulse referred to as frequency chirp. The chirp depends on the sign of the dispersion parameter. And the frequency chirp is negative, the frequency decreases across the pulse from the leading to the trailing edge if the dispersion coefficient parameter is positive.
The relation between dispersion parameter of SMF and DCF and their length is given by:
D1*L1 + D2*L2 = 0.
D1 and D2 are dispersion parameters of SMF and DCF respectively and L1 and L2 are their length.
From above equation D2 will be always negative as D1 is positive.

[jyoti raina]

Hi Ranjeet Sir..
Thanks for sharing this important info on the concept of the relation between SMF and DCF.. I feel it should be very helpful to everyone working with DCF.
As Dhiman Sir mentioned about using loop control for DCF i also think that it is a good option as i have myself used loop control option. The performance is good.. As Khadija mam said that if we take DCF not equal to 5 times SMf distortion appears i think loop control may help her to overcome that distortion.. I hope it will be helpful for all. Thanking you

With Regards
Jyoti Sharma

[Ubaid Bhat]

hi ranjeet kumar….
indeed a very good explanation of the relation between dispersion parameter of SMF and DCF and their length.it is very helpful.
but i am confused with the explanation of the Khadija omran for taking the length of SMF as 5 times than that of DCF.Anyone please explain that if it is correct.But i think it is not necessary.
with regards
ubaid bhat

[Ranjeet Kumar]

Hi Khadija Omran,
As you have also pointed that “And Why when use it must the SMF length is 5 times the length of DCF “.
I think from above explanations you should understand that condition of SMF length is 5 times than that of DCF is not necessary.
It will vary according to dispersion parameters and length of fiber both.
Hope this will help you.
seeking your quick response.

[Khadija Omran]

Thank you very much 🙂

[SAHIL SINGH]

hi ranjeet kumar….

No doubt a very good explanation on the relation between dispersion parameter of SMF and DCF and their length.. Also very nicely pointed out that condition of SMF length is 5 times than that of DCF is not necessary… thanks for the information..

Regards
Sahil Singh

[rahul kumar]

Hi Khadija Omran,
I think there is no limitation of length of DCF. It is proportional to length of SMF.
That is when length of SMF increases we have to increase the length of DCF.
Seeking your response.

[rahul kumar]

Hi Khadija Omran,
The relation between the length of SMF and DCF and also between Dispersion coefficient of both is given as:
D1*L1 + D2*L2 =0, where D1 and D2 are Dispersion coefficient of SMF and DCF RESPECTIVELY, while L1 and L2 are length of SMF and DCF respectively. This means D2 will be always negative.

Thanks and regards,
Ranjeet

[rahul kumar]

Hi,
If the dispersion coefficient parameter of the fiber is negative, the frequency increases across the pulse from the leading to the trailing edge that is referred to as the positive frequency chirp. On the other hand, the frequency chirp is negative, i.e., the frequency decreases across the pulse from the leading to the trailing edge if the dispersion coefficient parameter is positive. Therefore, the rate of pulse broadening in the fiber with negative dispersion coefficient parameter compared to that expected from the GVD alone. However, the broadening rate decreases during propagation in the fiber with positive dispersion coefficient parameter, as the two chirp contributions cancel each other.

[Manoj Kumar]

Hello Khadija Omran.

I agree with what all other forum members have said so far. I agree with Dhiman saying that there is no restriction like length of SMF is 5times that of length of DCF. I also agree with Jyoti raina and Burhan num mina saying that the minimum and maximum length of DCF should be application specific and should be dependent on the design characteristics. I hope this will help you for better understanding.

With regards

[Author]

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