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Freedom Internet Fibre optic link properties

Note: The stuff below applies to Active optical network or AON.
Freedom internet also uses Passive optical network or PON, such as GPON and XGPON.

The link is a single strand of Single-mode optical fiber, with a different infrared laser wavelength going in each direction. A splitter prism inside each transceiver separates the two wavelengths;


To network (Up)From network (Down)
IEEE 802.3 IEEE 802.3
TX: 1310 nm TX: 1490 nm
RX: 1490 nm RX: 1310 nm

Note that this in fact an IEEE Ethernet standard! PON, on the other hand, is an ITU standard.
And infrared is of course, radio waves with a very short wavelength;

1310 nm229 THz
1490 nm201 THz
1550 nm194 THz


SC/PC connector SC/APC connector

In theory, any fibre-optic media converter which meets the above specs should work.
Note that the SC/PC and SC/APC are incompatible; The APC has a slanted / angled tip;

Straight vs angled fibre optical connectors
AFAIK PC and UPC connectors are compatible. But don't mix blue and green plugs! (other colours are for multi-mode fibre optic cables).

The fibre-optic cable is terminated at a FTU (Fibre Termination Unit); A little spool with some fibre-optic cable and a clamp which holds a fibre-optic connector. Mounted on the FTU is either a NTU (Network Termination Unit) or a patch cover. A NTU is a fibre-optic media converter which is mounted directly on the FTU.

Media converter

At my place, a ZTE ZXHN F3100 fibre-optic media converter is installed (powered by a 12V, 1A DC adaptor);

ZTE ZXHN F3100 fibre optic media converter
Note that there are different versions of this NTU. The older version has a different appearance and fibre-optic connector.

A patch cover has a fibre-optic patch cord.

Patch cover rear Patch cover 566046
Note that the above patch cord has two SC (big) connectors. And a lot of equipment requires a LC (small) connector.

A media converter converts optical to electric and vice versa. For instance to a TP-LINK MC220L media converter;

TP-LINK MC220L media converter

Some routers and media converters, including the MC220L, require a separate Small form-factor pluggable transceiver (SFP), which plugs into the media converter;


There are different SFPs for the various infrared wavelengths.
You may need a SC/PC to LC/PC adaptor cable or a SC/APC to LC/PC adaptor cable in order to connect to a SFP.
There are also SFPs that take a LC/APC fibre-optical connector (small green plug). So there are four types of SC to LC fibre-optic patch cords;

SC to LC Fibre optic patch cords
Big plugSmall plug

And some SFPs take a SC (big) plug. So there are eight varieties of patch cord;

SC to SC Fibre optic patch cords
Big plugBig plug

Big and small are relative. Both plugs are rather small. The ferrule (the ceramic tube which holds the fibre) is 2.5 mm wide in a SC connector and 1.25 mm in a LC connector!
Below a SC/APC to LC/PC cord with an one Euro coin (⌀ 23.25 mm). Note that the ferrules are covered by protective caps:

SC/APC to LC/PC patch cord

Make sure to use the right patch cord!

Terminology confusion


Some people use the phrase 'fibre-optic modem'.
Though a media converter can be considered to be a ca 200 THz ASK (on-off amplitude modulation) modem, it is never clear what people mean by 'fibre-optic modem';
Is it a media converter? A router? An analogue telephone adaptor? Any combination thereof? Or anything (indirectly) connected to a fibre-optic link? In my experience, a lot of people use the word modem, when they actually mean router!
It is best to be clear. So the confusing phrase 'fibre-optic modem' should be avoided. Most fibre-optic links are in fact a type of Ethernet. So to avoid mystification and confusion, it's best to treat it as such.


Equally confusing is the acronym ONT; 'Optical Network Terminal'. ONT can in fact mean many totally different things! Always ask people what exactly they mean by ONT!
AFAIK, Freedom Internet uses the acronym 'ONT' exclusively to mean 'PON media converter'. Nothing more. So no router or ATA (Analogue Telephone Adaptor).
PON uses different downstream wavelengths and time division multiplexing upstream; A PON media converter needs to be registered to the network in order to get a timeslot!