Which fibre-optic cable for which router? LC/APC, SC/APC & FTTH explained simply

The type of fibre-optic cable required between the fibre-optic junction box, GF-TA, ONT and router depends primarily on where the fibre-optic cable terminates and what types of connectors are present at both ends of the cable.

OS2 single-mode cables (9/125 µm) are used for typical FTTH and FTTB connections. Many directly connected fibre routers or fibre modules have an LC/APC connector on the router side. The fibre-optic junction box, on the other hand, may have, for example, LC/APC or SC/APC connectors.

This MAG guide takes you step by step to finding the right DINIC connection cable.

The most important rule: do not order based solely on the router model. Always check both ends of the connection: the router or fibre module on one side and the GF-TA or fibre optic junction box on the other.

Quick guide: Which fibre-optic cable do I need?

Router connected directly to fibre Router/fibre module: LC/APC Fibre connection socket: LC/APC Required: OS2 Simplex LC/APC → LC/APC
Router connected directly to fibre Router/fibre module: LC/APC Fibre junction box: SC/APC Required: OS2 Simplex LC/APC → SC/APC
Separate ONT present: Fibre ends at the ONT Router: WAN / Ethernet Required: normally a network cable from ONT → Router
Is there an ONT? If so, the router is not usually connected directly to the fibre optic cable. The optical cable runs to the ONT or fibre optic modem. An Ethernet cable is then usually used from the ONT to the router’s WAN port.

LC/APC or SC/APC – which connector do I have?

LC Stecker für Glasfaserkabel

LC – compact

LC has a 1.25 mm ferrule and a compact locking mechanism. LC is used on the device side of various fibre-optic routers and fibre modules.

SC Stecker für Glasfaserkabel

SC – larger and easy to grip

SC has a 2.5 mm ferrule and a push-pull mechanism. SC/APC is frequently found on fibre-optic connection sockets, GF-TA units, handover points and other FTTH components.

Key point: LC and SC refer to the connector type. APC, on the other hand, refers to the angled polish of the optical contact surface. This is why, for example, LC/APC and LC/UPC are not technically the same, despite both having the same LC connector type.

Which cable combination is suitable for my fibre-optic connection?

CASE 1

LC/APC → LC/APC

The router or fibre module and the GF-TA or fibre optic socket both have an LC/APC connection.

Typical solution:
OS2 · Simplex · LC/APC 8° to LC/APC 8°

View LC/APC → LC/APC »
CASE 2

LC/APC → SC/APC

The router or fibre module has an LC/APC connector, whereas the existing fibre optic socket or GF-TA has an SC/APC connector.

Typical solution:
OS2 · Simplex · LC/APC 8° to SC/APC 8°

View LC/APC → SC/APC »
CASE 3

Adapter or coupler

Suitable APC adaptors and couplers can be used for existing installations, extensions or specific connection combinations.

Examples:
LC/APC–LC/APC or LC/APC–SC/APC

View APC adapters »

Router, GF-TA or ONT – where does the fibre end?

Installation Router page Fibre-optic side Typical connection
Direct fibre-optic router LC/APC GF-TA LC/APC OS2 LC/APC → LC/APC
Direct fibre-optic router LC/APC GF-TA SC/APC OS2 LC/APC → SC/APC
Router behind ONT Ethernet WAN Fibre ends at the ONT ONT → Router, usually via Ethernet
Extend the existing APC cable depending on the connection depending on the connection Check for a suitable APC coupler
UPC/PC connection available Check individually UPC / PC Do not automatically use APC
Do not connect APC and UPC directly to one another. The contact surfaces have different geometries. The plug shape and cut must therefore be checked at both ends of the connection.

Which fibre-optic cable for the FRITZ!Box Fiber?

For FRITZ!Box Fiber models with the corresponding FRITZ!SFP modules, LC/APC is used on the module side. The type of cable required at the other end depends on the existing fibre-optic connection box.

FRITZ!Box 5530 Fiber

The fibre SFP modules have an LC/APC socket on the fibre side.

  • GF-TA LC/APC → LC/APC to LC/APC
  • GF-TA SC/APC → LC/APC to SC/APC

FRITZ!Box 5590 Fiber

The fibre SFP modules designed for the FRITZ!Box 5590 Fiber also use LC/APC.

  • Fibre-optic socket LC/APC → LC/APC to LC/APC
  • Fibre optic socket SC/APC → LC/APC to SC/APC
The router model alone is not enough: even if the router side uses LC/APC, the GF-TA may have a different connector type depending on the network operator and installation. Therefore, always check both the router side and the fibre optic socket.

Other fibre-optic routers

Even with other routers, gateways, SFP-ONTs and media converters, you should not select a device based solely on the product name. Check the actual optical socket or the fibre module used.

In addition, the device must support the optical access technology used by the network operator.

AON, GPON and XGS-PON – are these the same as LC or SC?

No. These terms describe two different things:

AON (Active Optical Network) – an optical network architecture or transmission technology.
GPON / XGS-PON – passive optical network technologies for fibre-optic access networks.
LC / SC / APC: mechanical connector design or the polish of the optical contact surface.
Mechanical compatibility does not automatically mean technical compatibility. An LC/APC cable may fit perfectly into a router and fibre-optic socket – but the router or fibre module must still support the fibre-optic technology used by the network operator.

Direct fibre-optic router or router behind an ONT?

Router connected directly to the fibre-optic network

A router with an integrated fibre-optic modem or a suitable fibre module is connected directly to a GF-TA or fibre-optic connection socket.

This requires an OS2 single-mode connection cable with suitable connectors at both ends.

Router behind an ONT

With a separate ONT, the optical connection ends at the Optical Network Terminal.

An Ethernet network cable then usually runs from the ONT to the router’s WAN port.

Why use OS2 single-mode for FTTH and fibre routers?

FTTH and FTTB connections are typically based on single-mode fibre. DINIC connection cables for fibre routers therefore use OS2 9/125 µm.

OM3 and OM4, on the other hand, are multimode fibre classes intended for other network and data centre applications and should not be used as a substitute for an OS2 FTTH patch cable.

When is a fibre optic adapter useful?

Adapters and couplers can complement existing fibre-optic installations. They are useful, for example, for:

  • Extending an existing LC/APC connection cable
  • Connecting two suitable pre-terminated cables
  • Adapting existing connection or handover points
  • LC/APC-to-SC/APC connections using a suitable adapter
  • Servicing and upgrading existing FTTH/FTTB installations
Where possible, use a cable that fits directly: a single continuous cable with the correct connectors at both ends avoids additional optical connection points and usually results in a neater installation.

View DINIC APC adaptors & couplers »

What cable length do I need between the fibre-optic terminal box and the router?

The length depends on the actual cable route between the fibre-optic junction box or GF-TA and the router or ONT. DINIC router connection cables are available in various lengths up to 50 m, depending on the series.

  • Measure the entire route
  • Take into account the router’s position and cable routing
  • Allow for a reasonable margin
  • Do not kink the fibre-optic cable
  • Avoid tight bending radii
  • Do not apply tensile stress to the connectors
  • Avoid unnecessary adaptors and couplings
For the FRITZ!Box Fiber: FRITZ! points out that, due to the comparatively low attenuation, the cable length within a standard home connection is usually of secondary importance. More important are undamaged cables, correct connectors and neat installation.

Before ordering: check these four points

1 Direct router or ONT?
Check whether the fibre optic cable actually leads to the router or terminates at the ONT.
2 Determine
the router side Which connector is on the router or fibre module – for example, LC/APC?
3 Identify
the fibre terminal (GF-TA) / fibre socket Check whether it is LC or SC, and also whether it is APC or UPC/PC.
4 Check
network technology The router or fibre module must support AON, GPON, XGS-PON or the specific technology used by your network operator.

Frequently asked questions about fibre-optic cables for routers

Which fibre-optic cable do I need for the FRITZ!Box 5590 Fiber?

The FRITZ!SFP fibre module uses LC/APC. If the fibre optic socket also has LC/APC, an LC/APC to LC/APC connection is typically required. If the fibre socket is SC/APC, an LC/APC to SC/APC cable is used. In addition, the fibre module must be compatible with the provider’s network technology.

Which fibre-optic cable do I need for the FRITZ!Box 5530 Fiber?

Here, too, the fibre SFP module has an LC/APC socket. The type of connector required at the other end of the cable is determined by the existing fibre-optic connection socket.

LC/APC to LC/APC or LC/APC to SC/APC?

This is determined by the connection on the fibre-optic junction box or the GF-TA. If both ends are LC/APC, an LC/APC to LC/APC connector is used. If the router has an LC/APC connector and the GF-TA has an SC/APC connector, an LC/APC to SC/APC connector is required.

How can I tell the difference between LC and SC?

LC is smaller and has a compact latching mechanism. SC is larger and uses a push-pull design. The images above show a direct comparison of both connectors.

What does APC stand for?

APC stands for Angled Physical Contact and refers to an angled polish on the fibre end face. APC connectors are usually marked in green and are frequently used in single-mode FTTH connections.

Can I connect APC and UPC together?

APC and UPC should not be connected directly to one another. The fibre end faces have different geometries and are not optically designed to be used together.

Is a green connector automatically APC?

Green is usually used to indicate APC. When ordering, however, you should always check the technical designation of the connector and not base your decision solely on the colour.

Can I use OM4 for my fibre-optic router?

OS2 single-mode fibre is used for typical FTTH/FTTB connections. OM4 is a multimode fibre for other network applications and should not simply be used in place of an OS2 router connection cable.

Do I need a fibre-optic cable if I have an ONT?

The optical connection is required up to the ONT. The router itself is usually connected behind a separate ONT via Ethernet using its WAN port.

Can I extend the fibre-optic cable to the router?

Yes, provided the fibre type, connector and end face match. Suitable couplers can be used for this purpose. However, a single, sufficiently long cable is usually neater and avoids additional optical connection points.

Is every fibre-optic router compatible with every FTTH connection?

No. In addition to a mechanically compatible cable, the router or the fibre module used must also support the optical access technology employed by the network operator.

Can I position the router further away from the fibre-optic socket?

In principle, a suitably longer OS2 connection cable can be used. It is important to ensure the cable is routed correctly without kinks, to use suitable connectors, and to follow the specifications provided by the router and network operator.

Selecting the right DINIC fibre-optic cable for routers and FTTH

OS2 simplex connection cables with LC/APC and SC/APC connectors, as well as suitable APC adaptors for fibre-optic routers, ONTs, GF-TAs and professional FTTH/FTTB installations.