Do fiber modem is a modem or A fiber to ethernet conveter

[AMPLECONCH]

Do fiber modem is a modem or A fiber to ethernet conveter 

[Oshino Shinobu]

If we're talking full fibre internet, where the fibre runs directly into your property, then the device it plugs into from your ISP is not a modem, it's a media converter. Modems convert between digital and analogue signals, but as fibre internet is already digital, there is no conversion to take pace.

 

Most ISPs call them modems still to avoid confusing consumers, as if they start calling them GPON, ONT etc. media converters, people would no doubt get confused. As far as most are concerent and really as far as it matters for the majority of people, it performs the same role for the user as a modem so it's easier to keep calling it one.

[manikyath]

"modem" implies it is a device converting a stream of data to an analog signal to be transmitted over an analog medium. (phone line, coax, RF, ...)

 

so no, a fiber modem is not a "modem", but for (home?) fiber internet a "fiber modem" is a device that performs the same role as a classic "modem" would for twisted pair or coax based internet, so to avoid confusion it is just called a "modem".

[Kisai]

1 hour ago, AMPLECONCH said:

Do fiber modem is a modem or A fiber to ethernet conveter 

It's not a "modem"

 

Usually how it works is ISP fiber has a fiber transceiver on both sides. The same make and model, typically. That plugs into a SFP port on each side that kinda looks like a weird ethernet connector from the outside. But it actually fits a "SFP" which allows the ISP to replace that with whatever they want to connect.

 

Say you had a condo building that was wired for fiber in the 90's, and they decide to upgrade you to 10Gbit. Well 10Gbit internet wasn't a thing in 1999. So they swap the transceivers on each side, and there you go, now it's 10Gbit*

 

Now the question tends to get into "what does the ISP actually lease/rent/sell me?"

 

In a general sense, you're given an "internet router", a real one, not the kind that's in cable and dsl "modems". This router can pretty much be replaced with anything provided it has a SFP port and you know the configuration of the port. For example, the local ISP here just gives you a fixed or dynamic ip address, no matter what. So that fiber box gets terminated with a small "deck of cards" sized box the SFP plugged into, that speaks 10Gbit ethernet on the other side. That's all. If you need anything fancier, up to you.

 

Consumer/residential tend to give users a router on top because plugging a computer in to the internet naked is usually a recipe for hacking or abuse. Hence the ISP's want control over the WiFi router they give you. You don't need it if you don't want it. Just be prepared for a lot of futzing around if you don't take it. It's not like DSL and Cable where the protocols (DSL (PPPoE) and DOCSIS) require some kind of RF conversion, and hence are a "MODEM".  Fiber is usually already speaking the same protocol (Ethernet) on both sides.

 

The same fiber installed in 2009 at 15Mbits can do 40Tbits in 2022 if the SFP's were upgraded. Chances are you would never be able to use such bandwidth even if you wanted to, hence why ISP's want full fiber networks. It's basically future-proof provided there's low damage to the fiber over time.

 

 

[Chiyawa]

Modem (MOdulator and DEModulator) basically convert digital signals to analogue signals and vice versa.

[Ralphred]

3 hours ago, Oshino Shinobu said:

Modems convert between digital and analogue signals

 

3 hours ago, manikyath said:

analog signal to be transmitted over an analog medium

 

3 hours ago, Chiyawa said:

convert digital signals to analogue

All, and I mean ALL, digital signals sent over copper are analogue and just a facsimile of a digital signal, if they weren't you'd have radiation issues. By these standards a fibre modem is more of a MODEM than that which is traditionally labelled as such.

It's the analogue nature of electrical conductors that makes light based tx/rx such an attractive proposition for long distance communication.

[Chiyawa]

12 hours ago, Ralphred said:

*Snip

Ah, sorry, I mixed up. But basically, a modem is to modulate and demodulate signals. Meaning it combines the real signal to the carrier signal (Modulating) before it transmit over a medium and split the real signal from the carrier signal (Demodulating) of incoming transmission (more like a radio).