Real/True FIOS uses FIber Optics all the way to the home
Anything that is called FIOS that does not use Fiber Optics all the way to the home, is not real/true FIOS.
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A cellular wireless solution might require an antenna to route the signal through the metal encased motor home. The Verizon Wireless Community forum might be place to start if you are wanting to stay with Verizon for the service. https://community.verizonwireless.com/
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FiOS pulls a Fiber cable to your residence. If you're typically roaming from location to location on a frequent basis, Verizon Wireless service may be suitable for the RV. Just keep in mind, Verizon Wireless does not sell 4G LTE / Satellite service with pure unlimited usage right now, so be mindful of data usage if you plan to be using it for video streaming - video eats up data quickly. 5G service (With unlimited usage for now) is on the horizon but right now has only been tested in and made available in limited markets, until the network is built out more and the technology matures. IF you go with Verizon Wireless, you might want to get an external antenna paired with a 4G LTE Booster for automotive and recreational vehicles to ensure you get a good signal inside. This helps if you're using a Jetpack or Cell Phone for Internet. The Verizon Wireless forums (As someone linked to above) is a better place to ask for help.
Now if you're truly asking about FiOS (as in, the service which offers TV, Internet, and Home Phone over a Fiber Optic cable), Verizon will actually install what is called an ONT, or Optical Network Terminal, somewhere on your property. It likely won't be attached to or installed inside of the RV just because, well, the point of an RV is to be able to drive it somewhere from time to time. So the ONT will be a device which will live likely where your electric, cable, and telephone (landline) hookups live in a weatherproof box with power hook-up available. Then the cable coming into the RV would be an Ethernet (CAT5e) connection or in some cases, Coaxial cable that is already inside of many RVs today. It'll work similar to your power, sewer and water hook-ups, and cable if you happen to have a cable company providing service to you currently.
Another possibility is DSL-based setup which is Internet only. Verizon is trying to phase these out. But if they sell DSL service or sell "FiOS" over DSL, this would ride over the phone lines at your lot.
Now, if you're just trying to access Wi-FI that the campground / park is providing, this really depends on how well the Wi-Fi system was designed. I've been in RV parks where there is no problem getting a signal because the campground installed high powered, highly directional equipment that work similar to those you'd find on a cell phone tower, which can penetrate right through the RV, and is sensitive enough to let your device talk back to the network. The only time you'd need an Antenna outside of your RV to access the Wi-Fi network is if you're in a dead spot, or live in a section where the network was poorly built.
This is probably the best answer I can give you right now. If you have more information on what you're asking about, we can clarify it further.
Another option which I use in two autos (not an RV) is internet in the vehicle. I know verizon is entering that non dogle phase of it now. They presently use something called HUM for internet but is also metered and has other features.
as in my unlimited data ‘connected car from AT&T” I have the use of unlimited data for $20 a month for 8 devices. Like i said verizon wireless is starting to get new vehicles which can give you internet but alas not fios