When it comes to land-based high-speed broadband connections, there are currently two competing technologies: Coaxial Cable vs Fiber-optic, or Cable vs Fiber, for short.
This post will briefly explain the two and offer tips for handling their broadband terminal devices: the Cable modem vs the Fiber-optic ONT. You'll walk away confident about what equipment to get the next time you upgrade or change your Internet service.
If you live in areas where Cable and Fiber are available, you can use them simultaneously in a Dual-WAN setup, which is helpful for those working from home.
There's no such thing as "best" routers for a particular Internet service provider or type -- Fiber-optic, Cable, or whatnot.
If you run into that type of information somewhere on the Interweb, it's likely nonsense content written for SEO purposes.
Any standard router, including the primary unit of a mesh Wi-Fi system, will work, at its full potential, with any standard Internet broadband terminal device -- modem, Fiber-optic ONT, or others. That's true as long as the two can connect via a network cable, which is almost always the case.
Compatibility is generally applicable only between a terminal device and the ISP. For example, certain modems work with Comcast Xfinity while others might not. This is also the case for any gateway unit.
In relatively rare non-standard cases, some Fiber-optic lines might require a router that supports VLAN tagging (a.k.a IPTV). The majority of Wi-Fi 6 and newer routers support this.
Dong's note: I first published this piece on December 28, 2021, and updated it on March 21, 2023, to add relevant, up-to-date information, including DOCSIS 4.0.
Fiber vs Cable Internet, or ONT vs modem
Before continuing, though, let's address the elephant in the room: your beloved DSL. Yes, I'm aware of it.
Short for digital subscriber line, DSL uses the existing phone line -- that same wire we once used for the good old Dial-up connection -- to deliver modest broadband connections.
DSL has declined significantly due to slow speeds and unreliability in recent years. Most DSL providers have been slowly moving to Fiber as the replacement.
But in a way, as far as the Internet net is concerned, DSL is similar to Cable.
As the name suggests, Cable Internet is the broadband connection via the coaxial copper wires used originally for Television or Cable TV.
Since the coaxial Cable was initially made for TV signals, there needs to be a modem to make it work for the Internet, which is data signals -- similar to the case of DSL that uses the telephone line.
What is a modem?
A modem is a device that works as a modulator and a demodulator. It converts service signals into computer data signals and vice versa. Since the service in question is cable TV, we have the Cable modem.
Cable modems use a standard DOCSIS to carry data signals, an acronym for data over cable service interface specifications. And that's the only acronym you need to know in the world of Cable Internet.
DOCSIS helps make broadband affordable since it leverages the existing copper wiring for cable TV -- the infrastructure is already there.
And since coaxial wiring works like a cobweb, DOCSIS is resilient. When a cable breaks, that affects only a few families, if at all. (In return, Cable can also be hard to maintain since it can take a long time to locate and fix a broken line.)
The biggest shortcoming of DOCSIS is that it has lopsided connection speeds -- the upload tends to be one-tenth (or even lower) of the download -- known as asynchronous Internet. That's the case with all cable connections.
The curious case of Cable Internet’s fast download vs slow upload speeds
If you're wondering why Cable Internet's upload speed is always much slower than download, the reason is quite simple.
Initially, the network of coaxial copper wires was built to deliver a ton of data -- the video and audio signals of Cable TV -- to each household without needing anything in return. For the most part, TV viewers don't send anything back to the provider.
When provisioned to deliver data, the same concept applies to the wiring, but this time that's because the provider can lower the investment and maintenance costs by not providing fast upload speeds. So only lopsided modems are manufactured, and the rest is history.
And that has generally worked out fine since, in practice, consumers receive much more data (download) than they send (upload). Still, Cable Internet has gradually offered faster upload speed, and eventually, it'll deliver the same speed both ways.
Presently, there are two main versions of DOCSIS in use, including DOCSIS 3.0 and DOCSIS 3.1.
With DOCSIS 4.0 slated to be available as soon as late 2023, DOCSIS 3.0 is slowly being phased out.
In any case, picking a suitable modem can be quite a task, especially when you're on a budget -- more on that below.
Let's continue with Fiber.
Fiber-optic has a ton of confusing terms.
Technically, the name is GPON, short for Gigabit passive optical networks. GPON is part of the Fiber to the Premises (FTTP), a.k.a Fiber to the Homes (FTTH), broadband delivery approach.
Nowadays, it's more often called PON since it can deliver Multi-Gig broadband.
Since the optical wiring is designed for data connections, Fiber doesn't require a modem. Instead, it uses an ONT at each endpoint, short for Optical Network Terminal. An ONT converts the optical signals into the common Ethernet standard via a Base-T or SFP/SFP+ port.
Base-T vs SFP
Ethernet port types in brief
This type is known via a misnomer called Registered Jack 45 or RJ45. So we'll keep calling it RJ45.
On the other hand, the SFP or SFP+ (plus) port type is used for telecommunication and data communication, mostly in enterprise applications. SFP stands for small form-factor pluggable and is the technical name for what is often referred to as Fiber Channel or Fiber.
For data communication, an SFP+ port has speed grades of either 1Gbps or 10Gbps. The older version, SFP, can only do 1Gbps, though it shares the same port type as SFP+. This type of port standard is more strict in compatibility and more reliable in performance.
While physically different, BASE-T and SFP/+ are parts of the Ethernet family, sharing the same networking principles and Ethernet naming convention -- Gigabit Ethernet (1Gbps) or 10 Gigabit Ethernet (a.k.a 10GE, 10GbE, or 10 GigE).
Generally, you can get an adapter to connect a BASE-T device to an SFP or SFP+ port. Still, in this case, compatibility can be an issue -- a particular adapter might only work (well) with the SFP/+ port of certain hardware vendors.
The BASE-T wiring is more popular thanks to its simple design and flexibility in speed support. Some routers and switches have an RJ45/SFP+ combo which includes two physical ports of each type, but you can use one at a time.
In other words, an ONT is an Internet outlet that links to an Internet service provider (ISP) to deliver Internet to a home or an office. Each ONT has (at least) a network port to connect to a router's WAN port.
ONT vs Cable Modem in a nutshell
Though different in technologies, an ONT to a Fiber-optic service is similar to a modem to a Cable Internet plan.
They are both terminal devices that bring the Internet into a particular location -- a home or an office. Specifically, they're designed to be the endpoint to which you can connect a router's WAN port.
A modem converts the signals between those of the service line and data. An ONT sends and receives infrared light pulses to the ISP's server to transmit data.
Both get you connected at high speeds. How high? That depends on the Internet plan you have.
But the two share one thing in common: They need to be supported by the provider to work. Each ONT or modem might work with multiple ISPs, but an ISP can dictate which modems or ONTs it supports.
The point is that if you want to get your own terminal device, get one your Internet service provider supports.
The messy acronyms aside, Fiber-optic gives you "high-quality" Internet thanks to the fact that the modern optical data line runs (almost) directly from the provider to your home.
Among other things, this type of broadband delivers high speeds in both directions (upload and download) -- that's synchronous Internet -- currently up to 10Gbps and even faster.
On the downside, Fiber requires new wiring which is an expensive investment on the provider's side -- it's not ubiquitous. It also has a single point of failure. The Internet can be down for a large population if a single line is cut or broken. But it's also much faster to repair -- the provider can locate and fix a broken line relatively easily.
Fiber vs Cable Internet: The future is in the former
Generally, Fiber is the way of the future. It's clean, fast, versatile, and built purposely for a high-speed data network. It's simply far superior to the old copper wiring of Cable.
On top of that, with TV services moving slowly to streaming, there's no longer a need for new coaxial development.
Cable Internet is just a matter of leveraging existing infrastructure until it's no longer suitable or worth the maintenance, which is still far in the future.
That said, Fiber is the only, and preferred, wiring needed for new real-estate and technology developments. In other words, if your area doesn't have Cable or Fiber right now, it'll get the latter, if at all.
Another thing to note is that many Cable providers use Fiber as their primary data line connecting existing segments of Cable networks.
In this case, users still use a Cable Internet service — a modem is required — but will get faster and better quality broadband, though not at the same level as genuine Fiber-optic. In return, they can sometimes have Cable Internet outages in large areas if a main Fiber line is broken.
Tips on getting Fiber-optic hardware
When you order Fiber Internet, you'll get an ONT. Your provider will install one in your home, generally for free.
The ONT is a relatively simple device similar to a network port though it requires plugging into power. There are two ONT speeds -- Gigabit and 10Gbps. So, pick the appropriate one for your connection plan. Some ONTs come with both Gigabit and 10Gbps ports.
An ONT is generally available as a standalone unit, like the one in the pictures you see here, or inside a combo device, a Wi-Fi router with a built-in ONT (often called an ONR or Optical Network Router.)
For flexibility, it's always best to get just a standalone ONT when possible. That gives you the freedom to get a Wi-Fi solution of your choosing. What terminal device you can use depends on the provider; some are more flexible than others.
If you get a combo device, just like the case of a Cable gateway, you will likely have to do some tweaking to avoid double NAT.
Some Fiber-optic provider installs an ONT and then offers a separate rental Wi-Fi router or mesh system. In this case, it's best to say no and get your own Wi-Fi solution.
In some cases, in the US, certain Fiber-optic providers require VLAN tagging (a.k.a IPTV.) In this case, you need a router that supports this requirement -- most do.
And that's the only thing you need to remember when getting Fiber. On the other hand, getting a Cable modem can be pretty complicated.
Cable modem (further) explained: DOCSIS 3.0 vs DOCSIS 3.1 vs DOCSIS 4.0
Currently, the world uses versions 3.0 and 3.1 of the DOCSIS standard. (There's no need to worry about the earlier revisions -- thank goodness!). However, with DOSIS 4.0 expected to arrive soon -- In the US, Comcast plans to deploy it nationwide by 2025 -- so it's safe to say DOCSIS 3.0 is on its way out.
DOCSIS's specifications can be very confusing. For one, it changes depending on the region. For example, a set of particular modem specs might mean different speeds in the US than in the EU.
Also, it involves many technicalities, like channels, streams, QAM, etc. I'm not getting into the details, nor should you care about them. Instead, let's focus on the three latest standards and what they mean.
DOCSIS 3.0: Stream channels matter
In a simplified way, with DOCSIS 3.0, you can grade a cable modem's speeds via the number of stream channels it can handle.
There are downstream channels (for download) and upstream channels (for upload). More stream channels, or channels for short, translate into faster speeds.
Each modem comes with an indicator of the number of channels it can handle via a pair of digits. For example, the Netgear CM600 is a 24x8 modem. It has 24 downstream channels and 8 upstream channels.
In the US, the DOCSIS 3.0 standard delivers about 40Mbps per channel for download and 4Mbps for upload -- again, these are ballpark numbers that vary from provider to provider. As a result, the CM600 caps at 960Mbps download and 32Mbps upload.
Generally, DOCSIS 3.0's number of channels max out at 32x8. So a top-notch modem of this standard has cap speeds of up to 1.3Gbps download. And that's DOCSIS 3.0's maximum bandwidth.
It's important to note that just because a modem supports a specific performance grade (represented by the number of stream channels) doesn't mean it will work at that grade. That depends on the service provider's end (and the Internet plan you pay for).
And a provider generally loves to use as few channels as possible. The more stream channels, the more expensive equipment they need.
And that brings us to DOCSIS 3.1. This standard delivers a higher speed per stream channel. This version needs fewer channels to provide the same bandwidth and now has the cap of some 10Gbps in theory -- that's some 10x of version 3.0.
DOCSIS 3.1: Multi-Gigabit-capable on top of top-tier DOCSIS 3.0
Though the speed varies from vendor to vendor, a low-end DOCSIS 3.1 modem can generally deliver at least the same download speed as a top-tier 32x8 DOCSIS 3.0 counterpart.
DOCSIS 3.1 is so fast that vendors now omit the stream channel numbers. Instead, they call the modem DOCSIS 3.1 and its cap speed, Gigabit or Multi-Gig. The Netgear CM2000, for example, is a DOCSIS 3.1 2.5Gbps modem.
In other words, the stream channel numbers, such as 32x8 or 24x8, are only relevant in DOCSIS 3.0, where most modems cannot deliver Gigabit Internet. Starting with 3.1, Gigabit is the minimum, and Multi-Gig is a new norm.
Or you can safely assume that DOCSIS 3.1 starts at the place where DOCSIS 3.0 maxes out. And generally, most, if not all, DOCSIS 3.1 modems can function as 32x8 DOCSIS 3.0 ones. But the Internet provider ultimately decides which modem works and at what speed.
Realistically, 2.5Gbps of download speed is generally the fastest Internet speed we can expect from DOCSIS 3.1. Chances are you won't find a DOCSIS 3.1 modem with a 5Gbps or 10Gbps LAN port.
And that brings us to DOCSIS 4.0.
DOCSIS 4.0: The future of Cable as a real alternative to Fiber-optic
When I published this post, DOCSIS 4.0 was not yet available, so its details are still sketchy.
But it's safe to say it retains the principle of the DOCSIS standard and up the connection speed to up to 10Gbps. Most importantly, it will simultaneously deliver the same speeds for download and upload.
Currently, there's no DOCSIS 4.0 modem on the market, and the first ones will likely be available only from the provider. In the US, DOCSIS 4.0 will start with broadband speeds of around 4Gbps -- likely from Comcast Xfinity as early as late 2023 in certain parts of the country -- which is the next big step from DOCSIS 3.1.
In any case, the availability of DOCSIS 4.0 shows the commitment of Cable providers to stay relevant in the face of Fiber-optic.
While predicted to be much superior to DOCIS 3.1, DOCSIS 4.0 will likely be still inferior to Fiber-optic, which generally has lower latency and can easily go beyond 10Gbps.
Tips on getting a Cable modem: Which DOCSIS version to use?
With DOCSIS 3.0 on its way out and DOCIS 4.0 on the horizon, the safest right now is getting a DOCSIS 3.1 modem.
In this case, get one with a Gigabit port if you have a sub-Gigabit or slower broadband plan; or one with a 2.5Gbps port if you have Gigabit or faster plan. Not knowing which to get between two modems of the same specs? Pick the one that costs less.
When working with a supported router, a modem with two or more LAN ports can combine two into a 2Gbps Link Aggregation connection.
However, in areas where DOCIS 3.0 is still supported, getting a modem that can deliver the speed you pay for makes the most sense. A faster modem, in this case, won't give you any extra value for your money.
Here's my simple rule to determine which type of modem to get based on your Internet download speed where both DOCSIS 3.0 and DOCSIS 3.1 are supported:
- 500Mbps or slower: Get a DOCSIS 3.0 modem. A DOCSIS 3.1 one is not necessary and might not work.
- 500Mbps to sub-Gigabit: Either will do, but it's better to go with DOCSIS 3.1.
- Gigabit for faster (Gig+, Multi-Gig): DOCSIS 3.1.
No matter which DOCSIS standard you go with, what's most important is, when possible, to get just the modem itself instead of a combo device which is a Wi-Fi router with a Cable modem built-in.
The former gives you the flexibility in handling the hardware -- you're not stuck with a combo that's lacking in either the modem or the Wi-Fi portion or both.
Your real-world Internet (download) speeds
No matter how fast an ONT's or a Cable modem's advertised speed is, its actual ceiling speed is always its LAN port -- the one you connect to a router's WAN port.
That said, all terminal devices with a Gigabit LAN port will cap at sub-1Gbps or lower -- the port can't deliver full Gigabit after overhead.
To deliver true Gigabit Internet or faster (Gig+ or Multi-Gig), the terminal device must have a faster-than-Gigabit port. For an ONT, that's a 10GbE port and for a Cable modem, that's a Multi-Gig port (2.5Gbps, 5Gbps, or 10Gbps).
That said, to have a true Gigabit or faster Internet connection delivered to your home network, you need the following:
- A Gigabit for faster broadband connection.
- A Multi-Gig terminal device with a 2.5Gbps or faster LAN port.
- A Multi-Gig router with at least a Multi-Gig WAN port.
The actual speed you'll get is the slowest among the three above.
Either Cable or Fiber will be able to give you faster broadband than any current application would ever need, provided you don't mind paying.
But in more ways than one, Fiber is the way of the future. It has a much higher ceiling speed, especially the upload, much lower latency, and might be the only choice for many regions.
In the meantime, those with an existing Cable TV cable can benefit from the evolution of coaxial copper wiring. This infrastructure is still more than enough for anyone's broadband needs for the foreseeable future, especially with the upcoming DOCSIS 4.0.
Again, no matter which you opt for, get only the bare necessities from the Internet provider, namely the terminal device (modem or ONT). When possible, avoid getting the gateway -- a combo device with a Wi-Fi router and the modem/ONT built-in -- or any Wi-Fi equipment from the provider.
Besides not having to pay for equipment rent, faster performance, and more features, you'll have much better control over your privacy.