Optical Fiber Cabling
The optical fiber cabling used for network applications consists of a transparent core surrounded by a cladding material with a lower index of refraction that contains the reflections in the core.
Types of Fiber
Fibers that support many propagation paths are called multi-mode fibers (MMF). Multi-mode fibers are generally a wider core diameter and are used for shorter distance links or high power signals.
Fibers that support a single propagation path are called single-mode fibers (SMF). Single-mode fibers are used for longer distance links (more than 1,000 meters).
Advantages vs Copper
The advantages over typical copper cabling are:
- Bandwidth – a single optical fiber can carry 3,000,000 full-duplex voice calls
- Interference – signals traveling over optical fiber are immune to electro magnetic interference
- Attenuation – attenuation is extremely low permitting transmission over long distances
- Electrical – optical fiber does not have ground loop problems or lightning vulnerability
- Theft – copper is a theft target due to the value of copper on the scrap market
Single Mode Fiber
Single mode fiber is used for external long distance applications up to 80km without optical amplifiers. Using state of the art optical amplifiers and dispersion compensation devices the distance can be extended to thousands of kilometers at 10Gbps. The cable is referred to as OS1 or OS2.
Single mode fiber commonly uses two types of connectors; Subscriber Connector (SC) and Lucent Connector (LC).
Single Mode Fiber SC Connector
Single Mode Fiber LC Connector
Single mode fiber is commonly yellow but polarization maintaining single mode fiber is blue.
This is the most common optical fiber used for short distances within a building or campus. Typical applications support data rates of 10Mbps to 10Gbps over distances of up to 600 meters.
Multi-mode fibers are described by their core and cladding diameters but are more commonly referenced by classes based on their modal bandwidths (OM1, OM2, OM3, and OM4). For many years OM1 and OM2 fiber was used for premises based applications. Newer installations now use OM3 and OM4 as higher speeds become more common. Distances for each type of fiber are shown below:
|OM1||275 meters||33 meters||N/A||N/A|
|OM2||500 meters||82 meters||N/A||N/A|
|OM3||550 meters||300 meters||100 meters
330 meters QSFP+ eSR4
|OM4||1000 meters||550 meters||150 meters
550 meters QSFP+ eSR4
Although ST connectors were previously common, SC and LC connectors are now prevalent with OM3 and OM4 multi-mode fiber.
OM3 cables are commonly orange or aqua. OM4 cables are most commonly aqua.
Multi-mode Fiber SC Connector
Multi-mode Fiber LC Connector