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spectrumhead

join:2009-05-03

1 edit
reply to warwick

Re: SFP module for 100km

There is a -32db loss on the path.

We have tried now HP SFP J4860C but it didint link up.

Prices for transition SFPs varies too much on the internet. IS there any site where we can have reasonable prices ?

GLC-ZX-SM-RGD is also a Cisco SFP. We dont have Ciscos there.

Anyone ?



Rhaas
Premium
join:2005-12-19
Bernie, MO

1 recommendation

That seems high to me, I assume that there may be some connectors (not splices) in there?

For us, we always estimate .3db loss per KM, +.1 per splice. We are always under the calculated loss.

Dont look at the advertised distance, that is just a rule of thumb. Look at the specs of the SFP.

The one you said you tried would obviously not work:

MAX Output power: +5 dbm
Minimum Recieve Sensitivity: -23

So that gives you ~28dbm of link loss, subtract 3 dbm for fade and you have 25dbm.

The JD103A May work (couldn't find HP's specs only a compatible)
MAX Output power: +5 dbm
Minimum Recieve sesnitivity: -32 dbm

So you should have ~35dbm to work with. *If the TX power is outputting at +5*

I gotta run, but that should be enough info to get you started in the right direction.
--
I survived Hale-Bopp!


spectrumhead

join:2009-05-03

Rhaas ;

According to the above info,

I found TN-SFP-LXB162 to have 37dbm link budget.

This is the most powerful that I could find.

Do you think it may work ?



Rhaas
Premium
join:2005-12-19
Bernie, MO

Based upon the numbers you posted above, then yes. That should give you ~5db of margin and should function without error.

I would add the caution of contacting the SFP manufacturer and getting their recomendation.

When testing the fiber you will want to shoot it with the same wavelength that you plan on using to light the path.
Just like wireless at different frequencies, different wavelengths will have different losses. Also, the fiber can be manufactured so that certain freqencies and will perform better at 1550nm rather than 1310nm or 1590nm. So if you didn't shoot the fiber, you need to know what wavelength they shot the fiber at.
--
I survived Hale-Bopp!



54067323

join:2012-09-25
Tuscaloosa, AL

1 recommendation

said by Rhaas:

When testing the fiber you will want to shoot it with the same wavelength that you plan on using to light the path.

I would add to that, with dark fiber, never trust the as-built, enough crap happens with lit fiber (which gets noticed) in the day to day maintenance and changes of the plant.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to Rhaas

said by Rhaas:

Just like wireless at different frequencies, different wavelengths will have different losses.

I just wanted to comment that typical single mode optical fibers are good for both 1300nm and 1500nm range.

This spec for some really old SM fiber. I drew the loss curve just to show loss gets lower from 1300nm towards 1500nm but there is a water absorption peak in the middle.

spectrumhead

join:2009-05-03

You guys are very helpful. thanks for all the great comments.

So while checking I found out that I might be wrong considering the wrong transition network SFP.

Instead of TN-SFP-LXB162 WDM , we should consider TN-SFP-LX16.
I think LX161 and 162 are used in pairs as they have different wavelengths per transmit/receive. Instead we have to consider LX16.

Datasheet :
For LX16
»www.transition.com/TransitionNet···plex.pdf

Am I right ? Could you please help me a bit more to finalize this problem.


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

Yes, you can use a single LX16 module on each side of the fiber since it has duplex LC connectors.



54067323

join:2012-09-25
Tuscaloosa, AL

1 edit
reply to Rhaas

Delete duplicate



54067323

join:2012-09-25
Tuscaloosa, AL
reply to Rhaas

said by Rhaas:

That seems high to me, I assume that there may be some connectors (not splices) in there?

That link is long for sure, is it a bs splice or a connector(s) who knows, heck there could be a couple of biconic's in that span.

Personally I would (if possible) kick it back to the who ever placed the fiber to begin with and an OTDR to locate the loss(s) and clear them, lacking that I would push for a larger light budget, that is if the SFP’s can handle those levels.

spectrumhead

join:2009-05-03

@MatrixHDV
LX16 has a linkbudget of 37db and manufacturer states that these values are with %10 over performance to secure the specifications.

Do you think that we should consider a higher link budget than LX16 ?


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

1 edit
reply to spectrumhead

said by spectrumhead:

There is a -32db loss on the path.

We have tried now HP SFP J4860C but it didint link up.

I found basic specs for the HP and it says max 70km, so it was not suitable to begin with for your 90km link.
»h30094.www3.hp.com/product/sku/3673147

*** I am curious what tool/method you used to determine that the path has -32dB total loss. Anyway, assume that the contribution to this number from the actual 90km fiber run stays exactly the same and is out of your control.

But you do a very good job splicing the two endpoints and you also have newer design SFP modules with lower losses ... you can easily deduce that you WILL end up with a bit more system margin.

So in my opinion there is no need to buy the most expensive 200km/41dB LX20 module. The 160km/37dB LX16 you chose should be OK. Just to be safe, work out a 30-day return/exchange privilege before you buy.


spectrumhead

join:2009-05-03

@lutful
32 dbi loss was measured by the owner of the fiber pair recently. Actually the enginner told me that it is around -30 but it will be better for me to consider it like it is -32 for some reason i dont know.

The price I have got from a reseller is 1250$ per SFP. Is it too expensive or are there any cheaper options out there that I may consider ?



54067323

join:2012-09-25
Tuscaloosa, AL
reply to spectrumhead

said by spectrumhead:

We have tried now HP SFP J4860C but it didint link up. Anyone ?

By any chance do you have a light meter, the reason I ask is you might have an open fiber or two and not an SFP problem and since you have working SFP's you could shoot light down the fiber and measure it at the other end and compare what you are transmitting versus what you are receiving and if it is about 32 down you know the fibers are good, but if you are receiving nothing then your chasing the wrong dog for now going the SFP route.


54067323

join:2012-09-25
Tuscaloosa, AL

1 edit
reply to spectrumhead

said by spectrumhead:

Do you think that we should consider a higher link budget than LX16 ?

Guess that depends on the cost as you can always pad the receive down, but if the fibers come up long you cannot gain up...

switchman

join:1999-11-06

1 edit
reply to spectrumhead

said by spectrumhead:

@lutful
32 dbi loss was measured by the owner of the fiber pair recently. Actually the engineer told me that it is around -30 but it will be better for me to consider it like it is -32 for some reason i don't know.

The price I have got from a reseller is 1250$ per SFP. Is it too expensive or are there any cheaper options out there that I may consider ?

37 db is plenty of budget. I would be a lot more comfortable if they gave the specs for the SFP. If you look at the finisar site, you can see an example of what I am talking about for specs.

You could also get an amp use it. Something like this, »www.finisar.com/products/optical···cro-EDFA, in their 1RU package. Then pair it up with a DWDM sfp in you switches. This way if the SFP fails, you have a wide source to select from.

What wavelength did they shoot the fiber with, 1310 or 1550. If it was 1550, then that is not very good fiber or it has a lot of splices or connectors in the path.

When you look at optics you look at the Min TX launch power. That in combination with the min rx sensitivity gives you you link budget. The actual TX power of your SFP will be between the Min and Max value there is no guarentee as tothe actual launch power. It will probably be around+2 or +3, but you can't count on it.

JDSU also makes good stuff.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

1 edit

Finisar is an excellent brand.

I also agree that OP needs to get official specs for the chosen 160km SFP to make sure (minimum TX power - RX sensitivity) comes out a few dB higher than the 30-32dB loss on this fiber.

OK, I was looking at marketing spec for Transition TN-SFP-LX modules.

TN-SFP-LX5 [50 km/31.1 mi.] Link Budget: 19.0 dB
TN-SFP-LX8 [80 km/49.7 mi.] Link Budget: 24.0 dB
TN-SFP-LX12 [120 km/74.6 mi.] Link Budget: 32.0 dB
TN-SFP-LX16 [160 km/99.4 mi.] Link Budget: 37.0 dB
TN-SFP-LX20 [200 km/124.3 mi.] Link Budget: 41.0 dB

My hunch is that the RX sensitivity is the same for all modules and they are only increasing TX power for the increased range and link budget guarantee. If RX sensitivity was -30dBm across the modules, minimum TX power would have to be +7dBm for LX16 and +11dBm for LX20 ... which boggle my mind. Definitely worth asking for their complete technical specs.