Tight buffered and loose tube fiber are the two styles of constructions Fiber optic cables offered. Between them, there are several common denominators, like the fact that both have in their interior a strengthening member of sorts that can be made of stainless steel in the form of wire strands, aramid yarn or gel-filled sleeves.
Even though they might have similarities of construction between them, they are each designed for specific environments.
Loose Tube Fiber
This type of cable is designed for the outdoors. Cables that are on the outside are continuously stressed by a plurality of environmental conditions that could affect their integrity and performance.
Temperature changes, ice and wind loading, thermal shock, moisture, and humidity are some of the environmental conditions to which a cable can be subject. It’s no wonder it must be resistant to the very core, in order to preserve and protect the optical properties of the fibers within.
The fiber core, coating, and cladding are all very well protected by being enclosed in semi-flexible tubes that function as protective sleeves.
These cables tend to hold several optical fibers at a time, loosely bundling them up in an outer jacket that encompasses everything inside.
Notice the following:
Loose tube cables con also be found filled with a water-resistant gel that surrounds every fiber it contains.
This gel’s main purpose is to protect the fibers from moisture which makes them the ideal choice if you happen to live in a harsh environment with high humidity where H2O and water condensation can be a major problem.
If drastic temperature changes also affect your environment, loose tube, gel-filled cables will do the trick since they also have the ability to expand and contract when the temperature fluctuates.
If the cable will have to be submerged in water or cover a plurality of bends, then perhaps you might want to consider other options. The strain and pressure from water or recurrent bending just might impel the fibers to protrude from within the get and be left exposed which definitely isn´t good.
These cables differ from loose tube ones in several aspects. For starters, the fiber core isn´t protected by a gel layer nor any sort of sleeve.
the core is protected by a two-layer or double coating, consisting the first of plastic and the second of waterproof acrylate.
Moisture is barred from entering the cable and affecting the core thanks to the acrylate coating much like the gel that fills the sleeve of loose-tube cables protects the core from humidity and moisture.
The difference lies in that the acrylate coating never allows the core to be exposed when it’s bent or compressed underwater since it tightly wraps the plastic fiber layer that covers it.
Tight-buffered cables are mostly used for indoor applications and their sturdiness makes them the ideal choice for LAN/WAN connections of moderate length, long indoor runs or even ones that need to be directly buried as well as applications that are under water.
These cables are a lot easier to install than their loose-tube counterparts since they don’t need any sort of gel (which can be quite messy and a nuisance to clean up) for their installment.
Another perk is that there’s no need for a fan-out kit for splicing or termination. The connectors can be crimped directly to each fiber. Yeah!
Fiber cable termination
Adding a connector to each and every optical fiber in a cable is of what fiber cable termination consists. Without it, the fibers wouldn’t be able to be attached to any other equipment thus defeating their purpose of transmitting data and information.
The most popular solutions in terms of fiber cable termination are breakout kits, pigtails, and splicing.
Fiber optic terminations (where cables end) are made two ways:
Using connectors that marry two fibers creating a temporary joint and/or connect the fiber to a piece of network gear.
Splicing which creates a permanent joint between two fibers.
Whether connecting or splicing a fiber optic cable, either one must have both of the following:
High mechanical strength.
Great optical performance which entails low data loss and minimal reflectance.
Bear in mind that all terminations must be compatible with the equipment to which they will be connected and must also be protected against environmental issues or hazards that are present at the place of installment.
The most common connectors for fiber optic cables are male connectors (also known as plugs) that have a protruding ferrule which holds the fibers and aligns two cables for mating.
A mating adapter is used to concatenate the two connectors that must fit the securing mechanism they use (bayonet, screw-on or snap-in.) If you want to connect the cable directly to active devices like LEDs, VCSELs, and detectors, the ferrule design is your best bet.
Single-mode and multi-mode fibers each use different connectors and termination procedures.
The easiest to terminate are multimode fibers which are usually done by installing connectors directly on it whereas single-mode terminations are most likely made by splicing a pigtail onto the installed cable instead of terminating the fiber directly as you would usually find on multimode fiber.
Terminations used on single-mode cables demand extreme care while assembling in order to ensure the best performance possible. That’s why they are usually done in an industrial facility with an epoxy that has been heat-cured along with some machine polishing.
When faced with the task of choosing a connector type, take into consideration the following aspects:
Make sure the connector is compatible with the systems that are being used.
Do some research about the entire installation process if you are not familiar with it.
Be sure to investigate the pros and cons of each possible connector type before committing to a specific one.
A breakout kit is basically a set of empty jackets that have been designed to offer protection to tight-buffered strands of fiber from a cable that is fragile. This method of termination requires no splicing nor does it demand the use of a splicebox which is basically a protective enclosure for the cable ends.
When using fiber distribution cable, loose-buffer and/or ribbon cable, this is the most common termination choice because these types of cable contain multiple strands that are designed for it to be permanent.
This is a single, short, usually tight-buffered, optical fiber that boasts having an optical connector previously installed on one end and a length of exposed fiber at the other, which basically means it only has one connector on one end of the cable.
The end of the pigtail is stripped and then fusion spliced to a single fiber of a multi-fiber trunk. The pigtails are then spliced to each fiber in the trunk which ultimately "breaks out" the multi-fiber cable into the fibers that compose it for connection to the end equipment.
Pigtails can have either male or female connectors. Male connectors can be directly plugged into an optical transceiver whilst female connectors can be mounted bay two and two in a patch panel. If in pairs doesn’t work for you, they can also be mounted in single-fiber solutions that offer the possibility of connecting them to endpoints or fiber runs that use patch fibers.
Splicing two fiber optic cables together offers a permanent or semi-permanent connection between them. There does exist fiber optic splicing solutions that can be disconnected but this connecting method was not intended for connecting/disconnecting on a regular basis.
Fiber optic splicing is used when a more permanent solution is needed to fix a connection problem. For example, if you need to run a 10km length cable. Most fiber optic cables are made in maximum lengths of 5km so you´ll probably need to splice to cables together in order to achieve the desired run. In such cases, connectors are not an option.
There are two ways fiber optic splicing can be done:
Mechanical splices: this kind of splicing is normally used when a quick solution is needed.
You just need to strip back the protective layer that surrounds the fiber optic cable, clean it making sure there are no pieces of plastic or dust and the cut the fiber with precision and a firm hand, making sure that the angle of the cut has the same angle regarding the axis of the fiber. Something to bear in mind: this type of slicing can cause up to a 10% light loss.
Fusion splices: as the name indicates, this type of splicing is made by fusing (or melting) two fiber optic cable ends together. In order to obtain this type of connection, an electric arc is needed to weld the two ends together. It also requires that you know exactly what you are doing. If you don´t, leave it to the professionals since specialized equipment will be needed.
You can check the whole process of a loose tube fiber preparation for termination here: