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A lightning strike recently hit a client's cable TV and internet source (a typical RG-6 coax run from the street to the building).

It fried all the networking equipment: modem, router, switches. It even severed some of the CAT-6 cables running through the client's walls. Edit: forgot to mention, it fried DVRs and television sets too.

The client wants to prevent this from ever happening again, and came up with the idea of breaking up the RG-6 coax line with a small segment of fiber.

So my questions are:

1) Can anyone point me to any coax-extending fiber hardware?

2) Would this introduce substantial latency?

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2 Answers 2

up vote 8 down vote accepted

Can anyone point me to any coax-extending fiber hardware?

No, coax is broadband (in the radiological sense, not the marking hype sense). Fiber is baseband. You can not convert from one to the other without something processing every discrete signal separately. This takes immensely expensive and complicated equipment.

Would this introduce substantial latency?

Converting from one medium to another typically introduces a few microseconds of latency. Not worth mentioning in most contexts. But this is largely irrelevant in your case.

Your client will want two things:

  1. One well grounded Coax Ground Block. Typically installed at the point of premise entry. The ground wire should be at least 12ga solid core. Consult an electrician if this is not readily available.

    A Coax Ground Block looks like this and are usually installed by the cable company:

    Coax Ground Block

    This device has a high impediance path to ground, which allows the circuit to dissipate static charge and provides a minor path of least resistance to ground. It does not interrupt the path through to your devices under any circumstances however; so any significant lightning strike will go straight through it.

  2. One F-Type Lightning Protector. Get a few replacement tubes as they can be hard find the right size for older protectors. This too needs to be well grounded, at least as well as the ground block, and must be connected to the same ground source.

    A F-Type Lightning Protector is not commonly installed by the cable company:

    F-Type Lightning Protector

    This device has no link between the signal path and ground. It has a "tube" in the middle with a fusible link (ie, it melts easily upon heavy load and the ends "pull back" from the center making the "jump" through the center harder the hotter it gets - high end models are filled with arc suppression gas, but most are just filled with plain CO2). When the fusible link melts it routes the "incoming" circuit to ground, disconnecting the "outgoing" signal path completely. The one pictured is a cheap ($20-25 USD as of writing) model without a replicable tube.

Typically each piece of grounded equipment has it's own green 12ga+ wire running back to nearby electrical box with a ground bus. If a box is not available nearby then the individual grounds are aggregated to eliminate the potential for ground loops. Any building built in the last few decades will have a good ground system - if in doubt get an electrician to look it over.

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I guess what you said is the best solution, although I'm not quite sure what the difference is between the two items you mentioned. I see the same products showing up in the search results, no matter if I search for "coax ground block" or "f-type lightning protector". –  Lakey Jun 19 at 2:46
    
Thanks for updating the answer with a description and picture of each item! –  Lakey Jun 20 at 2:08

I'm not sure if you'll be able to find appropriate hardware - the DOCSIS the cable modem speaks is unlikely to be supported by the RG6-to-fiber converters you'll find out there. It's just not a common use case - isolating just the cable modem on the far side of some fiber once it's turned the internet connection into good ol' ethernet seems like a better option. (But it won't help the TVs.)

For a lightning strike to take out that much gear, it seems like it might not have had a good path to ground - probably a good idea get an electrician to check out the grounding situation.

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