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Want to connect 3 points with Ethernet at moderate bandwidth (100 Mbs - 200 Mbs is fine) where one total cable length is ~150m and the second leg is ~50m. At each node I plan to have mesh Wifi routers.

More specifically, I'm running cable in a subterranean conduit that will be 90 - 100m long and a second subterranean conduit 20m long. Within the conduit I have no capability of installing any gear nor maintaining it. At conduit ends I can easily install gear (PoE repeaters, etc.) to connect the subterranean runs to interior cabling. On the interior I have some capability of compromising convenience of location of termination points vs. the connecting cable (end of subterranean conduit to interior connection point). Thus, my total (longest) run is ~150m but I could make it 10m or 20m shorter at one end or both if absolutely necessary.

Looks to me like I might get good quality Ethernet cable (5e or 6) to work if I have a PoE extender at each end of the 90-100m conduit cable. But I don't know if I can have confidence in this solution. I don't mind replacing cables and gear at the ends of this 90-100m run in the search for something that will work; but, I really don't want to try to pull a different cable from the 90-100m conduit. I'd like to get this component right the first time.

Looks to me like MoCA is an alternative. Since I have just three nodes the 3 end devices are not cost prohibitive. However, I understand that MoCA will only tolerate a 100m cable run; so, it seems to have no advantage over Ethernet cable.

Nevertheless, perhaps I'm prejudging. Perhaps one or the other is significantly more tolerant of exceeding the nominal 100m maximum length. Or, the terminating devices are more tolerant. E.g., if my Ethernet cable is rated at 100 Mbps if it loses too many packets it throttles down to 10 Mbps; really too slow to tolerate more than occasionally. Perhaps MoCA is more tolerant. Perhaps if my MoCA cable is rated at 1 Gps it will throttle down to 800 Mbps . . . 200 Mbps when it loses too many packets. If such is the case, MoCA may be practical while Ethernet is risky.

Fiber optics is the next alternative I can imagine. However, I haven't found web sites titled "Fiber optics nets for the Complete Idiot". So, I don't know what this looks like. Again, I have just 3 nodes so the cost of the equipment at each of 3 nodes isn't likely prohibitive. I just have know idea what cable and equipment to buy.

My greatest concern is whether I need a single strand of fiber optic cable or a pair of strands. The fiber I see on Amazon is a pair of fibers with a pair of connectors on each end. These connector pairs look too wide to pass through a 1-1/4 - 1-1/2 - 1-3/4" conduit. That implies that I'll have to "crimp" my own fiber optic connector(s) on one end of each cable to pass a bear fiber (pair) through my conduit. I'd rather not have to crimp my own connectors; I'd rather buy a cable a little longer than needed with connectors which is tested and certified by the manufacturer to be a good quality fiber and connectors.

For about 50m I'm running alongside conduit carrying the neighborhood power mains (240V). So, I need to avoid electromagnetic interference from that source.

One thought occurs to me. When I drag my cable I can just as well drag multiple cables simultaneously. I might buy 100m of Ethernet cable and 100m of coax and 100m of fiber. If the Ethernet cable didn't work well enough I could buy the different terminating equipment to try the MoCA technology on the coax. If that didn't work I could buy the different terminating equipment to use the fiber. Does this make any sense?

The thing I'm trying to avoid is discovering that the cable I installed can't be made to work and I need to pull it out and replace it with a different cable. The total cost of the 3 cables isn't so great that I hate to buy and install all three from the outset.

Obviously, I might try point-to-point wireless; but, since I'm installing the conduit now I'd like to try a wired solution before trying the wireless alternative.

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    I think fiber is going to be your best choice (by far), but you're right that it's hard to find a guide to how to do it -- most search results are about ISPs deploying fiber internet connections, not doing your own fiber connection within your home. I'm trying to find something suitable, and if not I may write one myself later. – Nate S. Dec 15 '20 at 18:40
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    Wow that's a lot of words. What's the question, exactly? "Does this make any sense?" is too broad for our Q&A format. Please revise to simplify and focus. – isherwood Dec 15 '20 at 19:11
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    If you want ethernet over more than 100m, it's good to get comfortable with fiber optics. WIth the correct electronics (small form pluggable - SFP - an interface module that slots into a switch port designed for it) you can use a single-strand bi-directionally. LC connectors are nice and small (and also the standard for most SFP interfaces) so you won't be attempting to make your own connections ("crimping" is not the way, normally.) – Ecnerwal Dec 15 '20 at 19:19
  • Things may have changed since the mid-90s, but when our office installed fiber to the desktop, our IT guy had to go to a class for a week to learn how to terminate fiber, then each connector took him 15-20 min to properly connect. Unless you're going to do it for a living, you probably don't want to go through all that. I'd suggest pre-built cables and a larger conduit if necessary. I'll 3rd the response that fiber is probably the way to go. If your conduit is large enough, you could pull all three, but that's probably overkill – FreeMan Dec 15 '20 at 19:29
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    @isherwood, the question seems clear to me -- it's basically the first paragraph + "what's the best way to do this?" Everything else is additional details, plus ideas the OP has thought of that they're not sure about. – Nate S. Dec 15 '20 at 20:16
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The small ISP market offers many products you'll find useful for this project. These are unfamiliar to consumers because these items aren't found on the shelves of the local electronics retailer. Some of them require above-average installation or configuration skills - but as a person who confidently uses terms like Ethernet, MoCA, and PoE you'll do fine.

Long-range Ethernet: There are bridge/repeater devices available with claims of 1 Gbps line rate well beyond 100 m. For example, the Mikrotik GPeR claims up to 210 m per hop, up to 1500 m total length when multiple devices are sprinkled along the length of the line.

Coax and twisted pair: Old, existing coax and twisted pair (or newly-installed..) can be given new life with new electronics. Positron Access Solutions is one vendor selling equipment that would let you effectively set up your own DSL or cable-IP solution. I browsed one data sheet and didn't find claims as to distance, but they're marketing to multiple dwelling unit and other such installations where one would expect distances well over 100m. This is not impossibly expensive, but it does cost more than ethernet repeaters or fiber, so why do it?

Fiber: It sounds fancy, high-tech, expensive, and skills-intensive. It isn't. This is super easy and not costly. You can get pre-terminated fiber cable and pull it through the conduit. Ubiquiti sells a nice outdoor-grade 6-strand cable with LC connectors in 100, 200, 300 ft lengths (this product I've actually used several times). That might be just enough to get through the long conduit but you may have to use couplers to attach another patch cable at each end to actually reach your electronics. Or get made-to-order cable such as FS.com customized OS2 cable assembly.

With the fiber I'd suggest you use single-mode cable (OS2) with LC connectors because it's common, effectively future-proof, and plugs directly to the SFP or SFP+ (10 Gbps) adapters. To get back to Ethernet, by the way, you'd be looking for a "media converter" or else a switch or router with an SFP or SFP+ port.

In SFP modules there are two broad classes: Bi-Di (bi-directional) which use two wavelengths of light to communicate both directions over a single strand, or single-wavelength which use two strands each sending signals one direction. Bi-di cost a little more (but we're talking maybe tens of dollars difference for the FS brand). Don't worry about CWDM, DWDM, and such - those are used for getting many independent connections over a single strand of glass. A generic two-strand 1000BASE-LX or 10GBASE-LR adapter at say 1310 nm will do just fine for you, or bidi 1000BASE-BX. If you go bidi remember to get a matched set: one might transmit at 1490 and receive at 1310; the other would transmit at 1310 and receive at 1490.

If you do go with fiber get a few spare patch cables. Those will enable you to configure and test the equipment with it all sitting on one table, then carry it out into the field to plug into the long cables. It's much easier to test or troubleshoot when you can bring all the parts and interconnect them at one spot.

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    "as a person who confidently uses terms like Ethernet, MoCA, and PoE you'll do fine". You overestimate me; but thank you anyway. I don't use these terms with confidence but rather with trepidation. I got my general class Amateur Radio license at 15 so I understand wire and signaling. Thank you: you have provided the buzz-words that I need to search for. I'm pretty confident that the gear that I need exists at a price-point that serves my needs. I'm pretty sure that I can get it to work. What I lacked is the kinds of seed starting points you provided, Thanks again, – MarkPA Dec 16 '20 at 18:16
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Went throough this recently:

Two reasons against ethernet: That 100m spec is a 'soft' spec with full duplex end points. But you will find that it is very dependent on cable quality and gauge. Do not get the lightweight 26 ga. I think you can get 22 ga. You also will want exterior grade.

But you really don't want ethernet at all. With that kind of distance you have no certainty that ground is at the same potential at both ends. This gives rise to ground current loops. This is the same reason you don't ground a sub panel.

Use fiber. Measure by actually running a string (baling twine is cheap) and order it pre-cut with ends. Ethernet/fiber transceivers are cheap on Amazon.

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    Be sure to look for "inexpensive", not "cheap". There's an important difference! – FreeMan Dec 15 '20 at 19:45
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    Hang on -- you absolutely do ground subpanels; it's a code violation not to. And copper ethernet is transformer-isolated at both ends, so it won't create a ground loop, and running it between buildings is possible (though not ideal). Otherwise, I do agree with the rest of your answer; for this distance between buildings, fiber makes a ton of sense. – Nate S. Dec 15 '20 at 20:13
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    @NateS. -- yeah, the issue with copper Ethernet between buildings isn't a "ground loop" per se, but the need for primary protection to keep lightning-induced voltages from frying your computers (see NEC 800.90(A)). Note that primary protectors are listed to UL497 -- UL497A or 497B listed surge suppression devices won't do here, and many primary protectors aren't rated for a very high TIA/EIA Category either, if they have any such rating to begin with that is. – ThreePhaseEel Dec 16 '20 at 0:25
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I'm going to suggest you look at the wireless option. I have a similar scenario with buildings 600' apart and use a couple of Ubiquiti Nanostations and have been thrilled with their performance. And this is 600' through trees. Not one time have I had a drop - even in heavy rain and snow.

Across this link, I run two constant stream video cameras at 24Mbps each, a VOIP telephone line, as well as a few laptops and mobile devices. The devices lock in creating a 200Mbps link.

I think the nano's were spec'd for up to 12km, so 600' is nothing to them, but for less than $100 per antenna (one at the house, one at the barn), I couldn't be happier.

I originally looked at fiber but didn't have the luxury to bury a conduit because of the terrain.

Just a thought. Hope it helps.

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  • Note that outdoor fiber can be run overhead lashed to a messenger wire, BTW – ThreePhaseEel Dec 16 '20 at 12:44
  • @mikem: Kind of you to comment. On the facts, I suspect that you are correct. I was worried about heavy rains; and, another person told me that he feared the connection via PtP antennas would be unreliable. I had to take that into account. The compelling issue for me was that I had to strike when the iron was hot; i.e., the trench was open and I could drop my conduit for a reasonable price. That day is today. So, I'm paying for the conduit (not much). Next (some day) I'll (almost certainly) drag the fiber optic and buy the hardware. Then, see how it works. – MarkPA Dec 16 '20 at 15:13

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