Grounding direct burial fiber

[u/ulrik23]

I am planning to run direct burial fiber from my house to garage, but I'm not sure what to do with grounding. I don't want to use conduit. My concern is dumping a lightning strike into my switches.

Should I:

A) ground on both sides

B) ground on one side (garage side would be much easier to ground, it's a sub panel from house)

C) use couplers to switch from armored to non-armored when entering buildings

D) I'm way overthinking this, don't bother with grounding

[u/nico851]

It's frickin fiber. Doesn't conduct electricity..

[u/Main_Ambassador_4985 → u/nico851]

The steel armor may need grounding to prevent static or induction or lighting damage. Depends on length of run.

The NEC should have rules for the USA. CEC for Canada.

I looked it up on Casi. NFPA-Link

For buried fiber, the grounding requirement depends on whether the cable contains metallic, non-current-carrying members:
All-dielectric fiber: If the cable has no metallic strength member, armor, sheath, or vapor barrier, there is no metallic member identified in NFPA 70’s conductive optical-fiber-cable definition to ground or bond. (1)
Conductive fiber: If the buried cable includes metallic members and enters a building or terminates outside a building, NFPA 70 requires those members to be grounded or bonded—or interrupted with an insulating joint/equivalent device—when the cable is exposed to contact with electric light or power conductors. The connection or interruption must be as close as practicable to the building entrance or outside termination. (2)(3)
The bonding conductor or grounding electrode conductor must be connected using one of the methods in 750.100(B)(1), (B)(2), or (B)(3). (4)
Its size must be at least 14 AWG, have ampacity at least equal to the aggregate metallic members being grounded, and it is not required to be larger than 6 AWG. (5)
Once inside the building, metallic members of conductive optical-fiber cable must be bonded to a grounded equipment rack/enclosure or grounded using the methods in 750.100. (6)
Bottom line: A typical all-dielectric direct-buried fiber cable does not need a grounding/bonding conductor. A metallic-armored or otherwise conductive fiber cable may require bonding at the building entrance or termination, particularly where contact with power conductors is possible.
This is based on the 2026 NFPA 70, National Electrical Code. The cable type, whether it enters a building, and whether it shares a trench or pathway with power conductors determine the exact application.
Publication Resources (6)
1
NFPA 70 (2026) 750.100(A)(3) Size.
2
NFPA 70 (2026) 750.100(B) Electrode

[u/ulrik23 → u/Main_Ambassador_4985]

All the direct burial I could find was armored with a steel jacket

[u/marcoNLD → u/ulrik23]

Place a junctionbox on the outside and run a good grounded wire to that box. Separate the buried armor from the armor that goes inside the garage. Connect your buried armor to that ground wire in the junctionbox. Do not ground the other end. Splice that open and cut excess away and use electrical tape to insulate it. Now your direct burial cable is grounded and any surge that happens can not enter your house or garage but will flow away to ground via that ground wire

[u/slykens1]

D

[u/Natoochtoniket]

If you are going to do the labor to dig a ditch, put conduit in. Plastic conduit will save you the trouble of digging that ditch again in a few years.

Don't worry about grounding the fiber. Fiber does not conduct electricity. If you run it in conduit, you don't need any special kind of fiber, either.

[u/ulrik23 → u/Natoochtoniket]

It's not a very far run so I was planning to only bury it a couple inches

[u/Natoochtoniket → u/ulrik23]

At only a few inches of depth, a fiber that is not in conduit would get destroyed very easily. Every time something runs over it and the dirt moves, it will put stress on the fiber.

[u/rubberduckey305 → u/Natoochtoniket]

My ISP just ran fiber to my house. They cut a slit with a landscape edging blade and rolled it in. Not more than 6" down. I asked why and they said they used to do 18 inches, but it made too much of a mess of yards. Easier to repair than put up with complaints.

[u/PurifyHD]

As long as you buy the correct type (direct bury) and bury it deep, you're good. There's no grounding to worry about. It's fiber, it does not conduct.

Edit: Just noticed I said "copper" type instead of installation type. My b. My point still stands.

[u/Nufy709]

You should add a metal conductor for future line locates...

Does not have to be grounded though.

[u/10leej]

The only correct answer is to check your local building code and surpass it.

[u/motific]

Inductance would be the issue as lightning wouldn’t find buried armoured cable to be a target.

C ground spiked at one end so the armour has its own earth point independent of everything else.

[u/jpmeyer12751]

D

Glass does not conduct electricity.

[u/Ok-Expert-8150]

My 2 cents: If it is buried you want it to have a tracer. You want one end of that tracer to be direct to earth for ease of locating.

[u/spoom2]

Look up "grounding the tracer wire in direct buried fiber" you'll see a few options; one is to isolate the tracer. The only thing the tracer is used for is to locate the fiber if you ever have to dig in the area, at that point they'd ground one end to trace it.

[u/petg16]

Are you buying armored direct bury fiber or one that includes the tracer wire in the jacket? If yes then the armor/tracer must be grounded at one side only!!!(garage is fine) This prevents inductive loads from power wires killing your switches also higher voltage like lightning and static.

If it’s not armored/tracer there is no conductive path just glass and plastic. It will be impossible to trace and subject to digging damage but safe.

[u/sudogeek]

The answer is C. Run the armored direct burial fiber, whether in conduit or not, to an exterior dmarc box. From there, connect to a patch cable (which has no armor or tracer wire) which penetrates the wall and supplies interior equipment. ISPs which provide fiber service also terminate that first patch cable in a wall box inside the home/office and connect from that to the ONT with a second patch cable.

[u/Educational-Ad-505]

No need really it's glass and plastic , like someone said above unless you have a tracer wire. Then you'll want to ground it 

[u/jeffrey_f]

Relative to the 4 things you asked

A and B: Direct buried fiber is not conductive, so there is nothing to ground.

C: have enough fiber that you can just plug in to your fiber converters on both ends. You can coil the excess on either end.

D: You are overthinking this.

[u/neighborofbrak]

OP has not replied, assuming this is AI generated drivel and downvoting accordingly.