Hello Guys,
So, i was reading some post on reddit and i got to know something about single mode fiber. Is it true that if i use single mode fiber (typically, with LR transceiver) but at a shorter distance, (instead of using Multimode) will the transceiver get burn due to laser?
I’m aware of the fact that for shorter distance, MM is preferred and for longer distances, SM is preferred. But i was curious and wanted to know whether i can use SM fiber for short distance using LR modules.
Thanks
You would need to verify that the power is within the specified operating limits for the modules in question. You can use an attenuator handle cases where you have equipment originally intended for longer distances, if you absolutely must.
Edit: I’ll add that it should be fine if we’re just talking LR here, but doesn’t hurt to doublecheck the actual numbers.
Okay, i understand but i’m asking in general.
In general LR is made such that it’s fine. This example supports 2m to 10km:
It depends on the power of the SFP+ module. There are attenuators available for this purpose:
It’s recommended to have a fiber power meter and the datasheets for the transceivers at hand. Otherwise just use MM and short range modules and save your time for more important things.
Short is not so short though. When they say this, I thin like 50’. I consider 300 meters pretty far. I realize it’s way shorter than single mode though.
I used multimode in my house. Cheaper and potentially faster as network capabilites change.
On the old forum, @etorix suggested me to get the LR optics if it has a nice price one cannot refuse. If not, SR would be fine.
So, my question is would be there any risk if i use LR optics? My NIC supports both, SR and LR.
My rule has to always use LR modules. I am not a fan of MMF for several reasons. So my go to is LR BiDi modules. That way you only have to use a single fiber instead of duplex, and you can get them in any flavor, sfp, sfp+, qsfp+. That last one is kind of rare and expensive. Most qsfp+ uses mtp for 40gb+ or qsfp+ 28 100gb.
Now using LR modules in the SR since SHOULD not and WILL not hurt the modules unless they are cheap crap. I use LR 10 Gtek modules off of amazon and they are pretty solid, only had one issue out of hundreds.
My BiDi modules are usally 1270/1310 or 1310/1490, the latter being slightly better. I will also use a 2 meter patch cable and they work just fine. The transceivers, should attenuate the output power from the gate. The way they start is, is turn on low power and ramp up, as not to over power the connection. That is not so much for burning out the lasers or optical receivers, but to prevent over modulation and attenutation of the light signal. That is the primary reason I use single mode fiber 6/125 or LR units instead of multi mode fiber SR like om3 50/125.
Another option you can use if you DONT want to use a fiber trans module, but have sfp/sfp+ ports you would like to use is a DAC cable. They come in various lengths, and workg great. I am currently using several 10g sfp+ DAC’s and 2 qsfp+ 40g DAC cables.
DAC cables are the preferred option for short length up to 3m. I’ve had problems with a 5m DAC connection on a 10G connection.
For me there is nothing wrong with MM fiber and SR modules within a building. Just works fine.
My employer has got some machines with Singlemode Bidi 1G modules and cable lengths up to 10m. I just wouldn’t use the 30km modules but modules with lower output power. They do exist but you need to know what you buy. MM is easier in this way.
The question Bidi modules yes/no is a matter of cabling costs and other mechanical circumstances. In normal buildings using duplex cabling is no problem, so it’s just acost problem and a matter of dealing with two kinds of modules. Inside of that special machinery of my employer using duplex fiber would be impractical for mechanical reasons.
I have several clients that have 10m 10g DAC jumping from rack to rack with zero issues. Again depends on maker of switch and cable.
They generaly dont make “short range” bidi modules, as I said above, there is NO minimum on them. The way they ramp light is designed for this. I chose BiDi because of the spread sprectrum usage and not having to have duplex cables, but duplex modules are fine. I like them primarly for the 6/125 fiber. That size of fiber has less light scatter which allows the longer range connections, but that also make the cable being routed around racks, have less potential problems because of the tighter core and longer wave length. Will most people see an issue, probably not, but how you do anything is how you do everything, so I choose to use a better product. In this day and age, SM is not as cost prohibitive as it use to be.
OM3/OM4 are ok, I just prefer single mode. I have been installing fiber for 15 years, and the most of it was doing ONT installs, and we primarily used BiDi comms which is where I got the respect for it.
