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Fiber, 62.5 vs. 50
- Thread starter EgWeb
- Start date
62.5 micron fiber has more signal loss than 50 if I'm not mistaken, because of the larger diameter -- the light bounces around more and therefore loses more with distance. That being said, as long as your connectors are the same... you should be fine.
daronwilson
Vendor
I'm looking for clarification on this as well. As I remember, there is a particular loss for the signal when it goes from 62.5um fiber to 50um fiber, and a different loss when the signal goes from 50um up to 62.5um fiber. I would think that loss would need to be taken into account in your loss budget.
Along those lines, my light source and meter have 62.5um ST fittings, so, assuming I put 50um launch cables on there, zero it out, I should be able to test the 50um fiber and get a valid result I think. This should allow me to somewhat accurately test a new installation of 50um.
However, if I have a devices for 62.5 and I hook them together with 50, is there loss at each end that I need to consider in addition to my connector and fiber length loss? I would think so.
I'll see what I can find as well, just haven't taken the time to do the research.
Good Luck!
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com
Along those lines, my light source and meter have 62.5um ST fittings, so, assuming I put 50um launch cables on there, zero it out, I should be able to test the 50um fiber and get a valid result I think. This should allow me to somewhat accurately test a new installation of 50um.
However, if I have a devices for 62.5 and I hook them together with 50, is there loss at each end that I need to consider in addition to my connector and fiber length loss? I would think so.
I'll see what I can find as well, just haven't taken the time to do the research.
Good Luck!
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com
I'm trying to understand what you mean by "if I have a devices for 62.5 and I hook them together with 50, is there loss at each end that I need to consider in addition to my connector and fiber length loss?"
Why would there be any loss on top of line loss and connector loss?
The line loss for 50 is going to be more than 62.5, which is why I don't think it should be a problem.
Why would there be any loss on top of line loss and connector loss?
The line loss for 50 is going to be more than 62.5, which is why I don't think it should be a problem.
daronwilson
Vendor
Yes, the attenuation is less for 50 micron, more importantly the bandwidth is about 3 times greater for 50 micron (500Mhz/km at 850nm vs. 160Mhz/km at 850nm for 62.5).
My point is that anytime you convert the signal from 62.5 down to 50 there is some loss. This core size mismatch results in some coupling loss. As I read more, apparently if you are using VSCELs for the light source, the loss is very low and not of concern. LED sources are a bit more lossy, but still very functional.
Corning found that a mix and match of 50 and 62.5 can function very well at 1300nm, and may have a small amount of error potential at 850nm. They also found that the small coupling loss is easily overcome with excess power loss budget and insertion loss budget that all designed systems have.
Always fun to research....
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com
My point is that anytime you convert the signal from 62.5 down to 50 there is some loss. This core size mismatch results in some coupling loss. As I read more, apparently if you are using VSCELs for the light source, the loss is very low and not of concern. LED sources are a bit more lossy, but still very functional.
Corning found that a mix and match of 50 and 62.5 can function very well at 1300nm, and may have a small amount of error potential at 850nm. They also found that the small coupling loss is easily overcome with excess power loss budget and insertion loss budget that all designed systems have.
Always fun to research....
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com
- Thread starter
- #7
I'm pretty sure I'm thinking correctly on this... but I want to verify.
Take for example this RAD modem for extending a T1 via fiber. It says:
"It can operate over single mode or multimode fiber using 850nm or 1300nm LEDs, 1300 nm laser diode or 1550 nm laser diode"
Link:
I don't think it matters if the fiber is 62.5 micron or 50 micron fiber.
I know with the cisco GBIC's I can go 1800ft with 50 micron vs. 750ft with 62.5 micron (numbers vary based on modal bw)
Any thoughts?
Thanks,
Andy
Take for example this RAD modem for extending a T1 via fiber. It says:
"It can operate over single mode or multimode fiber using 850nm or 1300nm LEDs, 1300 nm laser diode or 1550 nm laser diode"
Link:
I don't think it matters if the fiber is 62.5 micron or 50 micron fiber.
I know with the cisco GBIC's I can go 1800ft with 50 micron vs. 750ft with 62.5 micron (numbers vary based on modal bw)
Any thoughts?
Thanks,
Andy
daronwilson
Vendor
The data sheet shows that if you spec 85 in the model number, you get a 850nm VCSEL for your power source. The distance table on the data sheet only shows single mode and 62.5um multimode, with a distance of 5 km. Fortunately they have provided the transmitter power (-18db) and the receiver sensitivity (-38db) so you can build your loss budget. It appears from what I read from Corning that you could use 50um fiber with not noticable loss (since you are using a VCSEL instead of an LED). Also the Corning folks say that you have more loss at 850 than at 1330nm, but you don't get that choice with this product for multimode.
I suspect you would have no problems in this with 50um, though it would be prudent to do the budget calculations with the length of fiber you plan on installing.
Good Luck!
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com
I suspect you would have no problems in this with 50um, though it would be prudent to do the budget calculations with the length of fiber you plan on installing.
Good Luck!
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com
The VCSEL lasers are inteded to be used with 50 micron fiber, so there better not be an issue of extra loss. As for mixing 50 micorn fiber with LED equipment, you get an over-launch situation. More light than the pipe can hold. So not all of it goes in, but the strength of the light that does go in is not diminished (attenuated).
Now, if you are using 62.5 patch cords and 50 cable, there will be more appriciable loss. Not enough to kill your link, but some. Board line losses may be pushed over the edge.
Having said that, again, it probably won't kill you link. Unless you're pushing 1gig+
Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay
Now, if you are using 62.5 patch cords and 50 cable, there will be more appriciable loss. Not enough to kill your link, but some. Board line losses may be pushed over the edge.
Having said that, again, it probably won't kill you link. Unless you're pushing 1gig+
Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay
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