Fiber Optics Bleg

It’s been some time since I had anything to do with fiber optic cabling, and my experience years ago was with Gigabit Ethernet over good old fashioned OM1 with no run greater than a few hundred feet. Back when I started with that, companies were just getting settled on 100Base-T for their LAN drops and there wasn’t yet any Cat6. Gigabit was something new and exciting.

So here I find myself years later looking to wire up my gun club for cameras, property-wide WiFi, and an access card system.

I know I’ll get people who will say “microwaves!” but we have large berms separating parts of the property, and I’d have to trench a good bit of new cable and clear a good bit of brush to get a clean line of sight to the places I need to go. Plus, I like wires. You can’t jam wires. I don’t have to worry about clearing and maintaining brush with wires. I can also get full GigE speed with wires.

The convention wisdom has been, and if you search the Internet still seems to be: “Multimode for short distances, and single mode for long distances.” Why? Well, cost, and MM is easier to terminate and more tolerant of poor field terminations.

As best as I can tell, the cost difference between a good quality OM3 or OM4 multimode fiber and OS2 single-mode fiber is trivial. Additionally, the SFP transceivers for 1000Base-SX and 1000Base-LX are not terribly different from the vendor I’m looking at. I’m also not planning to do any field terminations: there are plenty of vendors who sell pre-terminated fiber, and I was careful to measure the obsolete or non-functioning copper cables I pulled out of all the runs.

My question to anyone out there who’s well-versed and current with fiber: why would anyone use multi-mode fiber for campus length runs when there’s little price difference? Keep in mind I have a few runs that push the limits of multi-mode fiber at 1Gb/sec (550m) and would be right on the very edge with OM4 multi-mode fiber for 10Gb/sec (400m). So why not use single-mode? I can go 10km with single-mode, and 10Gb/sec is no problem. Am I missing something? It seems that maybe multi-mode has advantages if you’re looking to do field terminations, but the price advantage it might have once had isn’t’ really there anymore.

Addendum question: There are a handful of vendors out there selling pre-terminated cables. Price differences seem to be substantial. Are there any vendors to prefer? To avoid?

25 thoughts on “Fiber Optics Bleg”

  1. Commenting so as to follow, even though I get the bends whenever I go below Layer 3, and I like to have a dive plan for when I go to Layer 3.

    1. The real motivation is a high-definition, and eventually ultra-high-definition (4K) IP cameras. It’s a 1300 person club, and we don’t want any he said / she saids if there’s ever an accident.

      But we’re also trying to get rid of physical keys, so it would also allow us to put a card system on the archery clubhouse.

      And as long as I’m putting in the network for cameras and the access card system, no reason WiFi can’t tag along for the ride.

  2. My organization has 150+ buildings across a campus. We standardized on single mode for everything – both inside and outside plant. Check out – 10G LR optics for $34. At that price, dual connect everything and if one fails, you’ve got time to replace it with another inexpensive spare you’ve got on hand.

    1. That’s a damned good price for LR optics. I assume that’s non-Cisco? :D

      1. I’m sure. I haven’t bought Cisco products for years because I’m not convinced the name is worth it. Most enterprises buy it because it’s what people in the business know. But most network gear these days has a decent enough interface that if you’re not running anything unusual, it should suffice. For a basic VLAN setup like ours, I only need Layer 2 management, and I’m comfortable looking at other, cheaper brands.

        1. We switched to Hilscher for our industrial contracts after we had a bunch of cisco products die at 7 years. To many writes to the parameter save eeprom. Bad design, and usually very overpriced.

          When you pull the fiber, pull a small cord with it. Then if you have to pull another cable, just use the spare cord.

  3. If cost is comparable, the only two issues I can think of are eye safety and reliability.

    SM uses lasers which can blind, where as MM usually uses LED or lower power lasers which are more safe.

    The other issue is that SM needs very clean ends, which could cause issues.

    But really, those are pretty minor.

  4. If you are unsure about MM or SM fibre choice, going for LRM (long range multimode) optics will allow you to use MM or SM strands. They are pricier, obviously, but they could be a good choice.

    As for fibre choice, I would go MM OM4. The lasers are safer with multimode and with OM4 the distance considerations are trivial. You can do 40Gb/sec or 100Gb/sec over OM4 at 150 meters at 850nm (multimode wavelength). You only lose 50 meters from the spec if you go with MM OM3, by the way.

      1. Have to run down the road the parallels our 200 yard range, then get past a wide and tall berm, then get past the 25 yard range that uses that berm from the other side. That’s the road side of the run, and there is another good 100 meters getting from the road to the range and form the road to the clubhouse.

        Strangely this is not the run I’m most worried about, because pulling the dead cat5e cable out of the conduit was a breeze. I’m pretty sure it doesn’t have any bad bends.

        I’m more worried about a 106 meter run to the gate, where the old wire was tough to come out, because I think that conduit makes a few right angles underground. It’s 2″, so I think I can probably get away with it if I use a low-bend radius cable, but If I’m going to have problems, I think it’ll be on that run.

        Fortunately, that’s a much cheaper cable run to learn a lesson than the one that runs 400 meters :)

  5. I have over the years installed both mm & so but no mm in yrs. Sm has room for the future upgrades. I’m not sure about the distance you are running but I wouldn’t mix the two if you have anything close to the limits of mm. The newer sm stuff can be cleved and terminated using a simple razor blade fixture and super glue. I always put in plastic pipe to run the cables through which allows for a cable and a rope pulled through ate the same time, this lets you pull a second cable if it’s ever needed or to easily replace one. The pipe will last fifty yrs in the ground and with an access box at the end of a run you can extend to a new location without having to trench all the way back to the club house.

    1. It’s hard to imagine we’d need 10G out there, but I want to plan for it. Eventually we’ll probably use 4K cameras when they become cheap enough. Right now I only need 4 cameras out there, but I could see adding more in the future. Then there’s the idea that once Archery is wired up, maybe they’ll want Netflix back there eventually. Could be lots of 4K streaming around in a decade.

      1. If you think you’ll want 10Gb then go with the SM on distance alone, yes.

    1. Get safety glasses or goggles rated for all wavelengths that could possibly be aimed down your communication fibre. In other words, is it a diode driven crystal? you have two lasers to worry about.

      Along with that, make sure that this eyewear gives you full coverage. I encountered a situation that had glasses that the side shields would transmit what they were supposed to block. Eye damage resulted. Passing % varied from one set of glasses to another. We were a startup, and I think the vendor was also.

  6. The company I work for runs fiber and does networking. We’re moving toward running singlemode everywhere now, just for simplicity, unless the customer specifies multimode. And since the price for singlemode has come down to a negligible difference versus multimode, that makes the decision easier..

    1. Even for short building inter-closet runs under a few hundred feet? Really?

      1. Based on what I’m seeing, yes. If only so you can have a general rule about what’s used, and don’t have to specify “It’s OM2 between these buildings, but we have OS2 single-mode between these other two. Except on local runs intra-building where it’s all legacy OM1 runs, except for the new building where they installed OM3.” And I get that you can get away with a lot of mixing in places that shouldn’t be mixed, but that’ll eventually have limits as bandwidth keeps pushing. What I’m seeing is that if you did all single mode fiber, you’d get the most flexibility for your buck. Unless you have monkeys doing a lot of field terminations, and have a lot of legacy hardware, in which case you might be better off doing a quality multi-mode fiber.

      2. I want to be able to say ‘Everything at this club is OS2 fiber, so plan accordingly.”

        As best I can tell, that’ll get you to 10GB no problem, and probably beyond.

  7. We stopped doing mm in new buildings. Sm is cheaper and better. Sm optics cost more if you busy 1st party, but approved optics has very good prices. In general you can use mm optics on sm, and vice versa.The one exception is Cisco 40G mm bidir optics, I spent hours fighting with that before realizing that sm won’t work for that. Apparently you need the larger diameter of mm to fit all the lasers.

  8. Single-mode optics used to be stupidly expensive for much of a generation: I remember speccing out some SFP+ modules and seeing order-of-magnitude or two price differences.

    These days, that’s much less of a deal. First-party devices are still stupid-expensive, but third-party manufacturers can get you a pair of optics for <200 USD. Do check that any modules you buy are specifically compatible with your equipment, though: this is a field nearly as bad as USB3.

    That said, I would warn that while I've not seen tremendous variety in cable quality from one vendor to the next as long as you avoid the /really/ cheap stuff, for outdoor runs fibre is very sensitive. Even mid-grade stuff that isn't explicitly rated for outdoor use will decay in UV light within months, buried cables don't just need armor but also to be rated for the local temperature changes, et cetera. Plan ahead and be ready to replace runs without having to get a backhoe out.

    1. Don’t rely on the fibre maker’s claims of UV resistance. Ensure that none of your cables are exposed to ambient light. Use flexible conduit at the terminal locations. This may give you more critter protection. It’s amazing what mice, rats, and squirrels will find attractive.

Comments are closed.