Fiber Optic Cabling: Characteristics, Cable Types and Connectors

The fiber optic connection cable, normally called fiber cable, is a glass fiber cable of different lengths, and with which we can use different types of connectors. Normally we will have the LC and SC connectors mainly, depending on the use that is going to be given to the optical fiber. For example, in the case of connecting a fiber cable with an ONT, we will use the SC connector type which is the popular one we use at home with ONTs. LC connectors allow us to interconnect switches, making use of transceivers that will be connected to the SFP ports of a switch.

The fiber cable is a fundamental element in data centers, where we want to connect routers and switches between them, or directly a server that incorporates an SFP or SFP + port among others, in this way, we can interconnect the equipment at the maximum possible speed, and with a far greater distance than that allowed by the copper Ethernet network cable (100 meters maximum).

Fiber optic types and connections

Currently there are different types of fiber optics, the mode of transmission of the fiber, the types of protections that the fiber cable has, and even the type of connector used.

There are two types of optical fiber, single-mode optical fiber (SMF) and also multimode optical fiber (MMF). Depending on our needs, we will choose one type of optical fiber or another.

Singlemode and multimode fiber optics

The main characteristics of single-mode optical fiber is that it has a very small diameter, approximately 9 µm, in addition, it only allows one transmission mode, and allows the signal to be transported at much higher speeds and at a greater distance. This type of optical fiber is ideal for covering long distances, ideal for interconnecting switches or network equipment between different rooms, and being able to go much further without having too much attenuation. This optical fiber is somewhat more expensive than multimode optical fiber. Other features are that a laser diode should always be used. This type of fiber allows the downloading and uploading of data in the same cable, performing wave division multiplexing, in this way, we will have a specific wavelength for downloading and another for uploading.

On the other hand, multimode optical fiber has a larger diameter, usually 62.5 µm, as it has a larger diameter, the signal can be transported in more than one transmission mode. It is usually used for short distances, they are somewhat cheaper than single mode, and you can use a laser diode or LED that are cheaper. This type of fiber also allows wave division multiplexing, to provide Full-Duplex (download and upload simultaneously).

Transmission Mode

Depending on the fiber optic usage environment, Duplex or Full-Duplex communication can be achieved using wave division multiplexing. In the case of fiber optics, we will have a specific wavelength for uploading data, and another wavelength for downloading data, in this way, we can upload and download data simultaneously.

In the case of fiber optics with which to interconnect switches, communication is simplex, that is, in one direction only. Each fiber cable in simplex mode will have a connector on each side, but we will only have download or upload communication. To achieve Duplex communication, what is done is to have two fiber cables and a connector for each cable, in this way, we will have bidirectional communication. Normally these fiber cables are marked as “A” and “B” as they appear in the previous photo, in addition, they can use different colored covers to differentiate them easily.

Fiber connector types

There are different types of fiber connectors, in some cases we have LC-LC and SC-SC fiber connectors, but in other cases we have different types of connectors on both sides, this will depend on which devices we want to interconnect, but the most normal thing is that be the same type of connector at both ends of the cable. In the following image you can see the most common types of connectors:

• The SC (Subscriber Connector) connector is the cheapest type of connector, it is press fit, it is compact and it is commonly used in FTTH networks connecting the ONT to the PTRO of our home. It is compatible with singlemode and multimode fiber, it has a signal loss of around 0.25dB.
• The LC (Lucent Connector) connector is the type of connector most used in SFP transceivers of professional switches, it is push and pull type, it is very compact and allows a higher density of connectors in racks. It is compatible with singlemode and multimode fiber, it has a signal loss of around 0.10dB.
• The FC connector (Ferrule Connector) was also widely used years ago, but is now falling into disuse in favor of SC and LC connectors. This connector is threaded and has a vibration resistant attachment. It is compatible with single mode fiber and has a signal loss of around 0.30dB.
• The ST (Straight Tip) connector has been used in professional environments and military networks, it is quite similar to the FC connector, but it is used in multimode fibers and the loss is 0.25dB.

Fiber optic coating

We currently have different types of fiber optic cables, some of them with a higher coating to be suitable for outdoor environments. Depending on the environment where we are going to install the optical fiber, it will be necessary to buy one type of fiber cable (the coating) or another.

• Armored fiber cable: this fiber cable is mainly oriented to outdoor environments, it allows it to be walked on by a person and it is anti-rodents, although it is very hard, it has great flexibility.
• Fiber optic cable that allows bending : Normally fiber optic cables cannot be bent. This type of cable is resistant to damage and loss related to light reflection. Thanks to the design of the core, we can bend it without breaking or having problems. Thanks to this feature, it can be rolled up and perfectly adapted to the needs of the rack where we install it.
• Singlemode and multimode fiber cable: this cable is hybrid, in the first part and the last one has a diameter corresponding to singlemode fibers, this allows to go further in the fiber cabling, as well as to improve the quality of the data signal.
• Low insertion loss fiber cable : the end connectors are made so that the signal loss from inserting the fiber into the connector is minimal, reducing to 0.2dB for the LC and SC connectors that we usually use. In installations where the signal is very at the limit, this type of fiber cables will be necessary.
• Switchable fiber cable : allows you to change the direction of the fiber easily, without performing complicated operations, this is ideal for high-density environments where we have to change many fibers. No need for special tools, or change the entire fiber connector. This type of fiber is commonly used in networks with continuous changes, because it has great versatility.
• Uniboot connection cable : this type of cable integrates two fibers in a single cable, with LC connectors. This is ideal in high-density cable environments such as a datacenter rack, where we have hundreds of ports to use. Reduces the number of cables by 50%, because we have 2 fibers in a single cable, ideal for tight spaces.

What type of fiber cable should I choose?

The first thing we must take into account is to choose the type of optical fiber, whether single mode (SMF) or multimode (MMF), then we must take into account the communication mode, whether simplex or duplex, in addition, we will also have to choose the type of connector (SC or LC mainly) and also the fiber cable that we have explained above. For example, FTTH installations make use of single-mode fiber optics with SC connector, but in professional environments to interconnect switches, multimode fiber-optics with LC connector are usually used mainly, so, depending on your needs and use, you will have to choose a type of fiber optic, fiber cable and connector or other.

Thanks to fiber optics, today we can enjoy high speeds and low latency in our homes thanks to fiber optics to the home. Nowadays, no other type of fixed connection is being considered, since copper cabling installations (ADSL and VDSL) are suffering continuous closures, passing all their clients to FTTH connections that are faster, easier to maintain, and with much less incidents due to the wiring that reaches our home. Fiber has proven to outperform copper facilities in all areas, thanks to the fact that every day that passes, it is cheaper to manufacture and install fiber optics, its continuous deployment in all corners will make it the one that will serve us for many More years.