Long-Distance Gigabit Ethernet

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Apr 22nd, 2010
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I have a 400 km long fiber optic network to design in order to connect two remote sites in the desert. The existing fiber optic cable between the two sites is ITU-T G.652 compliant single-mode fiber. Furthermore, there are stations along the 400 km stretch, every 50 km (that makes approximately 8 stations).


What I've thought of so far is to connect the two sites using 1000BASE-ZX transceivers, then install an EDFA and dispesrion compensation module at each of the stations along the way. Is this feasible? More importantly, would it work? I read a lot about EDFA's being used in DWDM systems, but nothing about them being used in regular ethernet connections.


Does anyone have any other suggestions of what the best approach would be in such a case?

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viyuan700 Thu, 04/22/2010 - 22:39
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What I've thought of so far is to connect the two sites using 1000BASE-ZX transceivers, then install an EDFA and dispesrion compensation module at each of the stations along the way. Is this feasible?


Yes, It is feasible technically but You need to buy (atleast you would need 3-4 depending on link loss)15454 where you want to use EDFA and Dispersion module as these modules go into that box plus some more cards depending on you want pure DWDM or SONET/DWDM. Cost is going to be too much for just 1Gig line.


More importantly, would it work


Solution will work if it has right cards but as mentioned above the cost would be much more.


Does anyone have any other suggestions of what the best approach would be in such a case


Maybe if it is ONLY 1 Gig link, then leasing a wavelngth or circuit from a service provider would be a feasible solution (Capex + Opex both)


Let us know if you have any other question.

jean.laham Thu, 04/22/2010 - 23:16
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Hi viyuan, just a couple of points:

1) This is not a DWDM or SONET/DWDM system, just a pure ethernet connection.

2) The fiber cable that is installed is a 24-core SMF (i.e. 12 connections). And some of these fibers are interlinking some of the stations along this transmission system. These other fibers will need to run through EDFA's as well. I just didn't mentionen these earlier, because I am more worried about the functionality of the system right now.


I attached a simple layout of the intended network. The 400 km stretch is between CORE-1 and CORE-2 and all the ST's are the stations along the way.


As you can see, the stations and the cores are interconnected, so the cost issue may be tackled; I am just concerned about installing an EDFA with a simple (single-wavelength) ethernet connection @ 1550nm, not DWDM.


Another thing is the fact that ethernet is bidirectional (one fiber for transmission and one fiber for reception, per connection). How is this tackled when installing an EDFA? Aren't EDFA's unidirectional amplifiers?

viyuan700 Fri, 04/23/2010 - 00:48
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I know that your is pure ethernet connection but i didnot know you have some boxes already there (I was thinking why you will own 400Km of fiber).


I attached a simple layout of the intended network. The 400 km stretch is between CORE-1 and CORE-2 and all the ST's are the stations along the way.


Can you tell what these boxes are ST 1 to ST5. If they are SONET/SDH boxes then you can add an Ethernet over SONET/SDH card to them (If they are not too old / or buy some boxes like in this link http://www.rad.com/10/Gigabit_Ethernet_STM_4_OC_12_NTU/5259/. You need ONLY 2 but you need 2 STM 4/OC 12 port on your SONET/SDH box .


I am just concerned about installing an EDFA with a simple (single-wavelength) ethernet connection @ 1550nm, not DWDM.

You cannot use EDFA with your Ethernet connection, But 2 solutions mentioned above are right fit for you situation if you have SONET/SDH boxes already.



Another thing is the fact that ethernet is bidirectional (one fiber for transmission and one fiber for reception, per connection). How is this tackled when installing an EDFA? Aren't EDFA's unidirectional amplifiers?


You are right EDFA are unidirectional but we can use one per direction right. But DWDM doesnot make sense for your situation

jean.laham Fri, 04/23/2010 - 01:22
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Can you tell what these boxes are ST 1 to ST5. If they are SONET/SDH boxes then you can add an Ethernet over SONET/SDH card to them (If they are not too old / or buy some boxes like in this link http://www.rad.com/10/Gigabit_Ethernet_STM_4_OC_12_NTU/5259/. You need ONLY 2 but you need 2 STM 4/OC 12 port on your SONET/SDH box.


Unfortunately I am not too well-versed with SONET/SDH architectures; I am a lot more familiar with Ethernet networks. Furthermore, I am kind of bound by contract to stick to pure Ethernet.


You cannot use EDFA with your Ethernet connection, But 2 solutions mentioned above are right fit for you situation if you have SONET/SDH boxes already.


I found single-channel EDFA's; can't I just connect each fiber to a single-channel EDFA? That way I would have tackled the issue of the direction of transmission, as I would have full control over that by connecting the proper fiber into the corresponding input/output of each single-channel EDFA. Is there another dimension of this architecture that I am not aware of for this approach not to work?



P.S. thank you so much for your help so far, it's being really helpful.

viyuan700 Fri, 04/23/2010 - 02:03
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Can you paste a link or the spec of single channel EDFA .


Is there another dimension of this architecture that I am not aware of for this approach not to work?

There is no problem with the approach but i thought if you have SONET/SDH infrastrucutre already then you can use it.


I am not aware of single channel EDFA but if they are something like this.

http://www.ornets.com/Products/measurement/single_channel_edfa.html

Then technically there is no problem with this approach few points to consider,


1. Just ask the vendor from whom you are buying EDFA that can it take Etherent signal (Through Optical amplifier are protocol independent but better to ask).

2. Are you going to buy Dispersion module too? As i doubt the signal will go that far without dispersion module.


3. Look for EDFA & Dispersion Module by the time i have to check whether you need to regenerate your signal. You are taking care of Optical Power & Its shape but there is one more thing to look it timing (If you have heard about 3 R regeneration). In that case maybe you can use a media converter (or anything which take Gig E and gives Gig E)to regenerate the signal.

jean.laham Fri, 04/23/2010 - 02:41
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I am not aware of single channel EDFA but if they are something like  this.

http://www.ornets.com/Products/measurement/single_channel_edfa.html

Then  technically there is no problem with this approach few points to  consider,


Yeah, that's what I was talking about earlier.



In that case maybe you can use a media converter (or anything which take  Gig E and gives Gig E)to regenerate the signal.


I was actually considering using such media converters only, and thus eliminate the need for EDFA's and compensation modules. Would make things a lot easier, they would be guaranteed to work, I wouldn't have to worry about 3R regeneration and they are even low on power consumption (2W to 5W).


I actually don't see why I shouldn't do that, what do you think?

Tom Randstrom Fri, 04/23/2010 - 08:41
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To add on to the comments provided by VIYUAN700…


The Cisco ONS 15216 EDFA3 can be used in single channel applications (most EDFAs can be used). 


15216-EDFA3

<http://www.cisco.com/en/US/products/hw/optical/ps1996/products_installation_and_configuration_guide_book09186a008064dd16.html>


The problem with using an optical amplifier for this application is they each add noise to the link.  In addition, as the signal moves through the fiber, the shape of the optical pulse changes and will look radically different than the original; requiring the addition of dispersion compensation (as you mentioned).  Thus, when the signal reaches the far end of your 400km link, you may have enough light but the noise and the pulse shape may result in the receiver being unable to decipher (read) the signal.   

The use of a media converter solution might be the best (simple & cost effective) for your application.  I noticed that Transition Networks has long-distance GigE solutions that will provide link lengths of up to 160km (99 miles).  This extra distance might allow you to skip some of your intermediate sites and reduce the amount of regeneration equipment and power costs.     


Transition Networks

<http://www.transition.com/TransitionNetworks/Newsletter/google_tn.aspx?gclid=CO_djvqKnaECFSVI5wodhWElww>


Depending on your future growth and the other services that will be transported across these fibers, you may need to look into deploying a DWDM system.  This will provide many benefits including:

  • Increased bandwidth capabilities – Your current 12 fibers will limit you to 6 services using one service per fiber pair. DWDM will allow you add many more services per fiber pair (too many to count).
  • Improved network visibility – With the use of OTN, you gain additional link statistics and error reporting for proactive response.
  • Other – There are other benefits such as improved reach, performance, service flexibility, etc.


Hope this helps!


Tom

viyuan700 Fri, 04/23/2010 - 11:12
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I actually don't see why I shouldn't do that, what do you think?


The solution is fine it is fits to your requirement and you are the best person to know it. Every solution have the cost and benefits related to it. Like if there is any downtime how much is fine with you? Is media converter fits in that solution .

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