Fiber Optic Cables
Fiber optic cable is the newer, faster way to transmit data. These send data signals using light (lasers) instead of electricity. Light signals can travel faster for higher bandwidth, suffer from less signal loss, and degrade less from electrical interference. Fiber optic cables come in a few different varieties with multiple types of cable as well as multiple connectors.
Types of cable include:
Types of connectors include:
Single-mode fiber optic contains a very thin core, making it ideal for long-range transmissions. These cables can be incredibly long, with a single line potentially running for miles. The light transmitted by single-mode cable is between 1,300 and 1,550 μm, a frequency range that almost puts it into the infrared wavelength. This version of fiber optic cable is mainly used for telecommunications.
The name “single-mode” comes from the cable only transmitting a single mode of light down the cable. Typically, single-mode fiber optic is color coded yellow. The downside of single-mode is that their long range means they require very powerful lasers to operate at those extreme distances. The equipment needed to make lasers that powerful tends to be very expensive.
Multi-mode fiber optic has a thicker core than single-mode, with the exact thickness depending on which type of multi-mode you are referring to. The thicker core allows multiple light signals to bounce through the cable, which can provide better signal speeds. These are the types of fiber optic cables you will usually see in a building, generally being rated for distances under one kilometer. If you are unsure whether you have single-mode or multi-mode cable, you can generally tell by the color of the cable and it should be written on the cable jacket as well.
OM1 is usually colored orange and rated for runs up to 300 meters. They maintain a 1GB transfer rate and are most commonly used for computer networks within buildings.
OM2 shares its color with OM1 but covers double the length with maximum runs of 600 meters. Beyond the greater distance limit, it has specs matching OM1. OM2 is used in areas where 1GB speeds are satisfactory but greater distance is needed.
OM3 is aqua colored and provides speeds of 10GB for up to 300 meters. At shorter distances, it is possible to get better speeds out of OM3. Using an MPO connector, a distance of under 100 meters can achieve 40 or even 100 GB speeds. OM3 provides a speed upgrade to OM1, making it ideal for networks that will receive a high volume of traffic.
OM4 is a distance upgrade to OM3 (similar to how OM2 upgrades from OM1). OM4 carries 10GB signals up to 550 meters and 100GB signals up to 150 meters (still using an MPO connector for the latter). These tend to be used for large facilities with high-speed networks, such as data centers and financial institutions.
Fiber optic cables have a fair number of different connectors available. There are simplex and duplex versions of each connector. Simplex will have a single connector while duplex has a pair. Fiber optic signals are one-way; duplex connectors are used when you need to send signals back and forth instead of just one direction.
FC (ferrule core connector) is an older type of fiber optic connector that is starting to phase out. It is a threaded, screw-on connector that takes more time to plug/unplug than newer fiber optic connectors. Additionally, FC connectors cost more to make than the newer connectors while providing the same level of signal quality. The advantage of keeping FC on the market is that their threads allow them to stay in place while in motion, such as on moving or vibrating machinery.
LC (Lucent connector) fiber optic uses a push-pull design with a latch to keep themselves in place. The biggest advantage of LC is its small size, being about half the size of other fiber optic connections. This small stature allows devices that would otherwise have no space for a fiber optic port to use LC.
SC (standard connector) is a commonly used variant of fiber optic connectors. Simple and inexpensive, SC also uses a push-pull system but with a locking tab instead of a latch like LC. This cost-effectiveness has made SC popular with telecom companies, although it also sees use with datacom applications.
ST is similar in appearance to FC, but it uses a locking mechanism similar to a BNC coax connector instead of threads. Like FC it is also starting to be phased out, mainly because it is only usable for single-mode cables. As multi-mode becomes more popular and better implemented, more ST connectors will continue to be replaced by LC and SC.
Multi-fiber connectors (both MTP and MPO) are larger than other fiber connectors but have the ability to support up to 24 fibers single-handedly. These cables are used for systems that use many connections, such as data centers. MTP/MPO is difficult to make and their fibers cannot be readjusted after the cable is terminated, so a cable will often be MTP/MPO on one side and branch out to other types of connections like LC.
MTRJ (mechanical transfer registered jack) is a new, small connector about the size of a phone jack. Their small size allows for two ports where something like an SC duplex would take up one spot, doubling the connections you can include. While still too new to see widespread use, this is an up-and-coming connector that may become a new standard in the future.
Some versions of fiber optic cable are classified as UPC or APC. For example, a UPC rated SC cable would be labeled SC-UPC. UPC (Ultra Physical Contact) uses a polishing technique that diminishes signal loss compared to a standard fiber optic connector. The downside is that they deteriorate faster, especially when the cable is plugged/unplugged frequently. APC (Angled Physical Contact) corrects UPC’s issue by making the connectors at a small 8° angle. This angled position allows for tighter, more secure fits but does cause rotation issues if the connector is inserted upside-down or sideways.
FC (left), LC (middle-left), SC (middle-right), and ST (right) duplex connectors