3.1.5 Fiber Optic Cable Facts

Fiber-optic Cable Components

A fiber-optic cable, also called an optical-fiber cable, is composed of the following components:

  • The central core carries the signal. It is made of plastic or glass.

  • The cladding maintains the signal in the center of the core as the cable bends.

  • The protective layer provides a stiff structure to prevent the cladding and central core from breaking.

  • The plastic sheath encases everything and protects the cable.

Comparison

Fiber-optic cabling offers the following advantages and disadvantages as compared to other cable types:

AdvantagesDisadvantages

Advantages of fiber-optic cable:

  • Completely immune to EMI

  • Highly resistant to eavesdropping

  • Fastest available transmission rates

  • Greater cable distances without a repeater

Disadvantages of fiber-optic cable:

  • Very expensive

  • Difficult to work with

  • Special training required to attach connectors to cables

Mode

Multi-mode and single-mode fiber cables are distinct from each other and not interchangeable. The following table describes multi-mode and single-mode fiber cables.

ModeDescription

Single-mode

Single-mode fiber-optic cable:

  • Transfers data through the core using a single light ray (the ray is also called a mode).

  • Has a core diameter of around 10 microns.

  • Supports a large amount of data.

  • Allows cable lengths to extend a great distance.

Multi-mode

Multi-mode fiber-optic cable:

  • Transfers data through the core using multiple light rays.

  • Has a core diameter of around 50 to 100 microns.

  • Limits the distance of cable lengths.

Connectors

To connect computers using fiber optic cables, you need two fiber strands: one for transmitting and the other for receiving. Fiber optic cabling uses the following connectors:

ConnectorDescription

ST Connector

Fiber optic ST connector

An ST connector:

  • Is used with single mode and multi-mode cabling.

  • Is a keyed, bayonet-type connector.

  • Is also called a push in and twist connector.

  • Has a separate connector for each wire.

  • Is nickel plated with a ceramic ferrule to ensure proper core alignment and prevent light ray deflection.

  • Requires the exposed fiber tip to be polished as part of the assembly process. This ensures that light is passed from one cable to the next with no dispersion.

SC Connector

Fiber optic SC connector

An SC connector:

  • Is used with single-mode and multi-mode cabling.

  • Is a push on, pull off connector type that uses a locking tab to maintain connection.

  • Has a separate connector for each wire.

  • Uses a ceramic ferrule to ensure proper core alignment and prevent light ray deflection.

  • Requires the exposed fiber tip to be polished as part of the assembly process.

LC Connector

Fiber optic LC connector

An LC connector:

  • Is used with single-mode and multi-mode cabling.

  • Is composed of a plastic connector with a locking tab, similar to an RJ45 connector.

  • Is a single connector with two ends to keep the two cables in place.

  • Uses a ceramic ferrule to ensure proper core alignment and prevent light ray deflection.

  • Is half the size of other fiber optic connectors.

MT-RJ Connector

Fiber optic MT-RJ connector

An MT-RJ connector:

  • Is used with single mode and multi-mode cabling.

  • Is composed of a plastic connector with a locking tab.

  • Uses metal guide pins to ensure it is properly aligned.

  • Is a single connector with one end that holds both cables.

  • Uses a ceramic ferrule to ensure proper core alignment and prevent light ray deflection.