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Loose Tube or Tight Buffered Fiber Optic Cable?

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Fiber optic cable is available in many physical variations, such as single and multiple conductor constructions, aerial and direct burial styles, plenum and riser cables, etc. But there are two basic styles of fiber optic cable construction: loose tube fiber and tight buffered fiber. From the picture below, we can see that loose tube fiber holds more than one optical fiber, each individually sleeved core is bundled loosely within an all-encompassing outer jacket. However, in tight buffered cables, there are not so many cables as loose tube fibers.

loose tube fiber
Loose Tube Fiber

Loose tube fibers are designed for harsh environmental conditions in the outdoors. In loose tube cables, the coated fiber “floats” within a rugged, abrasion resistant, oversized tube which is filled with optical gel. Since the tube does not have direct contact with the fiber, any cable material expansion or contraction will not cause stress on the fiber. This gel also helps protect the fibers from moisture, making the cables ideal for high humidity environments. Cable containing loose buffer-tube fiber is generally very tolerant of axial forces of the type encountered when pulling through conduits or where constant mechanical stress is present such as cables employed for aerial use. Since the fiber is not under any significant strain, loose buffer-tube cables exhibit low optical attenuation losses. Although loose-tube gel-filled fiber optic cables are used for high-fiber-count, long-distance telco applications, they are an inferior design for the Local Area Network applications where reliability, attenuation stability over a wide temperature range and low installed cost are the priorities.

Tight Buffered Cable

Tight buffered cables, in contrast, are optimized for indoor applications. In the tight buffer construction, instead of using the gel layer loose tube cable has, it uses a two-layer coating. One is plastic and the other is waterproof acrylate. So tight buffered cables may be easier to install, because there is no gel to clean up and it does not require a fan out kit for splicing or termination. Because the fiber is not free to “float” however, tensile strength is not as great. Tight buffer cable is normally lighter in weight and more flexible than loose-tube cable and is usually employed for less severe applications. Such applications include moderate distance transmission for telco local loop, LAN, SAN, and point-to-point links in cities, buildings, factories, office parks and on campuses. Tight-buffered cables offer the flexibility, direct connectability and design versatility necessary to satisfy the diverse requirements existing in high performance fiber optic applications.

Each construction has inherent advantages. The loose buffer tube offers lower cable attenuation from microbending in any given fiber, plus a high level of isolation from external forces. Under continuous mechanical stress, the loose tube permits more stable transmission characteristics. The tight buffer construction permits smaller, lighter weight designs for similar fiber configuration, and generally yields a more flexible, crush resistant cable. So, you should choose the appropriate cable for your applications. Fiberstore offers both loose tube and tight buffer cables with high quality and low price. It may be your optimal choice to buy optic products.

Related article:

Tight-Buffered Distribution Cable Basis

Tight-Buffered Cable vs. Loose-Tube Gel-Filled Cable

What Are the Most Popular Fiber Optic Cable Types?

Recently, as the fiber optic cable is used more and more widely than earlier years, people also know more about the fiber optic cables than before. Usually, we learn that the fiber optic cables are divided into two basic types: single mode fiber and multimode fiber. However, according to the fiber optic cable is used for indoor or outdoor, there are many other fiber types too. These fiber optic cable types are all the popular ones which are available in the current market. Then I will introduce these various fiber types to you in this article.

Fiber Optic Cable Types: Indoor Fiber Optic Cables

In terms of indoor fiber optic cables, distribution cable, breakout cable, ribbon cable and LSZH cable are some popular types. Distribution cable and breakout cable all contain several jacketed simplex optical fibers packaged together inside an outer jacket, but in distribution fiber optic cable, tight buffered fibers are bundled together, with only the outer cable jacket of the cable protecting them. Besides, buffered fiber in distribution cable is 900 µm, which is smaller in size and costs less than breakout cable. Distribution cable is usually installed in intra-building backbone and inter-building campus locations. And breakout fiber optic cable is suitable for short riser and plenum applications. Ribbon cable includes up to 12 fibers contained side by side within a single jacket and is often used for network applications and data centers. LSZH cables are offered as an alternative for halogen-free applications. They are less toxic and slower to ignite which makes them a good choice for many internal installations.

breakout fiber optic cable types

Fiber Optic Cable Types: Outdoor Fiber Optic Cables

In terms of indoor fiber optic cables, however, tight buffered cables, loose tube cables, armored cables and submarine cables are some common popular fiber cable types. Among them, submarine fiber optic cables become more and more popular in recent years. These cables are used in fresh or salt water. To protect them from damage by fishing trawlers and boat anchors they have elaborately designed structures and armors. Other cable has armors is armored cable. Armored fiber optic cable includes an outer armor layer for mechanical protection and to prevent damage. They can be installed in ducts or aerially, or directly buried underground. Armor is surrounded by a polyethylene jacket. Tight buffered cable and loose tube cable are two early common outdoor fiber cables. Tight buffered cables have riser and plenum rated versions. These cables are flexible, easy to handle and simple to install. In loose tube cables, tube encloses multiple coated fibers that are surrounded by a gel compound that protects the cable from moisture in outside environments. This cable is restricted from indoor use, typically allowing entry not to exceed 50 feet.

Armored Fiber Optic Cable Types

All these indoor and outdoor fiber optic cables play an important role in optical network. As they have different characteristics, they have different applications too. For this reason, when you choose fiber optic cables, you must take their usability into consideration. For more information, you can visit Fiberstore, which designs and manufactures all these popular fiber optic cables.

Related Article: Fiber Optic Cable vs Twisted Pair Cable vs Coaxial Cable

Two Basic Types Of Fiber Optic Cable Construction

Based on 900um tight buffered fiber and 250um coated fiber there are two basic types of fiber optic cable constructions – Tight Buffered Cable and Loose Tube Cable.

Loose Buffer

A loose buffer’s inner diameter is much larger than a fiber’s outer diameter. Two major advantages from this design are perfect fiber isolation from mechanical forces (within given range) and protection from moisture. The first advantage is due to mechanical dead zone. A force imposed on a buffer does not affect the fiber until this force becomes large enough to straighten the fiber inside the buffer. A loose buffer can be easily filled with a water-blocking gel, which provides its second advantage. In addition, a loose buffer can accommodate several fibers, thus reducing the cost of the cable. On the other hand, this type of cable cannot be installed vertiacally and its end preparation for connectorization (splicing and termination) is labour-intensive. Conseuqently, the loose buffer type of cable is used mostly in outdoor installations because it provides stable and reliable transmission over a wide range of temperatures, mechanical stress, and other environment conditions.

Loose tube structure isolates the fibers from the cable structure. This is a big advantage in handling thermal and other stresses encountered outdoors, which is why most loose tube fiber optic cables are built for outdoor applications. In outside application, ADSS Cable is the special loose tube cable.

Loose-tube cables typically are used for outside-plant installation in aerial, duct and direct-buried applications.

loose tube cable

Structure of a Loose Tube Cable

Elements in a loose tube fiber optic cable:

1. Multiple 250um coated bare fibers (in loose tube)
2. One or more loose tubes holding 250um bare fibers. Loose tubes strand around the central strength member.
3. Moisture blocking gel in each loose tube for water blocking and protection of 250um fibers
4. Central strength member (in the center of the cable and is stranded around by loose tubes)
5. Aramid Yarn as strength member
6. Ripcord (for easy removal of outer jacket)
7. Outer jacket (Polyethylene is most common for outdoor cables because of its moisture resistant, abrasion resistant and stable over wide temperature range characteristics. )

Tight Buffer

A tight buffer’s inner diameter is equal to the fiber’s coating diameter, as illustrated in Figure 2.33. Its primary advantage is ists ability to keep the cable operational despite a break in the fiber. Since a buffer holds a fiber firmly, a small separation of the fiber ends won’t interrupt the service completely, althought it will definitely degrade signal quality. That is why the military was the first customer and still is the largest for this type of fiber cable. A tight buffer is rugeed, allowing a smaller bend radius. Since each buffer contains only one fiber and there is no gel to be removed, it is easy to prepare this cable for connectorization. Cables having a tight buffer can be installed vertically. In general, tight buffer cables are more sensitive to temperature, mechanical and water impacts than the loose buffer cables; hence, they are recommended mostly for indoor applications. On the other hand, tight buffer cables designed for special applications (such as military and undersea are the strongest cable available.

Tight buffered cables are mostly built for indoor applications, although some tight buffered cables have been built for outdoor applications too. Here we recommend you a good site to buy fiber optic cable, fiberstore is a fantastic selection of fiber optic cable, including simplex,duplex,tight buffered,breakout, breakout,  plastic fiber optic  cable etc. More information want to know, search fiberstore on Google.

Structure of a Tight Buffered Cable

outdoor cable

Elements in a tight buffered fiber optic cable

1. Multiple 900um tight buffered fibers (stranded around the central strength member)
2. Central strength member (in the center of the cable)
3. Aramid Yarn (trade name Kevlar, Kevlar was developed by Dupont) (wrapped around the fibers, for physical protection and cable pulling)
4. Ripcord (for easy removal of outer jacket)
5. Outer jacket (also called sheath, PVC is most common for indoor cables because of its flexible, fire-retardant and easy extrusion characteristics. )

Fiberstore specializes in fiber optic cable assemblies and fiber optic network devices manufacturing, we are known as the fiber optic cable manufacturer for the excellent products quality, competitive prices, fast delivery and good service. We not only offer bulk fiber optic cable assemblies to some world leading companies in this industry, but we also cooperate with many other companies from all over the world and support these partners to win in the market. We are professional China fiber optic company.

Loose-tube vs Tight-buffered Cable

Choosing the right fiber-optic cable has become more challenging than ever. The advent of new cable designs, many suppliers, changes in fiber specifications, and the many claims of cable performance can confuse even the most seasoned designers.The selection of the basic cable design is most dependent on the application and installation environment. The main objective in the cable design is to protect the fiber from stress and other environmental forces during installation and over the life of the product. From a technical standpoint, more than one type of cable may fit the bill for many applications. In that case, other factors such as ease of use, size, and cost will be added to the evaluation and selection process.

Let`s begin outside. The outdoor environment subjects a cable to the most extreme range of environmental condi- tions. These conditions include a wide operation-temperature range, thermal shock, wind loading, ice loading, moisture, and lightning. Therefore, protecting and preserving the optical properties of the fiber is a design priority.

The most proven fiber-optic cable technology for long-term reliability outdoors is the loose-tube, gel-filled design. This type of cable protects the fiber from stresses caused by the environment, namely moisture and temperature. Loose-tube cables, whether flooded under the jacket or water-blocked with dry, swellable materials, protect the fibers from moisture and the long-term degradation moisture can cause. As we all know, Fiberstore is the largest bulk fiber optic cable supplier, we provides a wide range of quality optical fiber cables with detailed specifications displayed for your convenient selecting.

The gel within the loose-tube construction stops the penetration of water and keeps it away from the fiber. In cold temperatures, the protection keeps water from freezing near the fiber–eliminating possible stress fractures. Since the fibers are able to move within the tube, the expansion or contraction that temperature fluctuations can produce in other materials does not transmit stress to the fibers.

Overall, loose-tube cables offer the best protection in an outdoor environment, especially in the less-sheltered applications involving aerial or direct-buried installations. The loose-tube design isolates the fibers from outside environmental and mechanical stresses. The optical performance is virtually unchanged as the cable is exposed to the elements. Telcordia Technologies, BICSI, RUS (Rural Utility Service), and the telco and cable-TV markets support this design.

Loose-tube cores are best-suited for armored applications, double-jacketing for more severe environments, and in figure-eight and all-dielectric self-supporting designs. Tight-buffered designs often do not have anti-buckling elements and do not decouple the fiber from extreme stresses, such as the material contractions that are experienced at extremely cold temperatures. This is why loose-tube cables are so widely accepted for use in outdoor environments. Talk too much about loose-tube cable, now we introduce you one of the loose tube cable for you, it is Loose Tube Type ADSS Cable. As shown following picture:

ADSS Cable

This Loose Tube Type ADSS Cable from Fiberstore is ideal for installation in distribution as well as transmission environments, even when live-line installations are required . As its name indicates, there is no support or messenger wire required, so installation is achieved in a single pass, making ADSS an economical and simple means of achieving a fiber optic network .

Moving indoors

At the other extreme is cable suitable only for indoor use. The indoor environment is less hostile and not subject to the extremes seen outdoors. Indoor cables traditionally have been a tight-buffered design with either a riser or plenum rating. These cables must conform to National Electric Code requirements for riser or plenum applications.

Tight-buffered cable designs typically offer a smaller package and more flexible cable. The 900-micron buffered fiber is easier to connectorize, and the cable is generally easier to prepare for termination. These cables do not typically provide protection from water migration and do not isolate fibers well from the expansion and contraction of other materials due to temperature extremes. Tight-buffered cables, often called premise or distribution cables, are ideally suited for indoor-cable runs. OM4 fiber optic cable is tight-buffered cable we often see in many applications such as Local Area Networks (LAN) backbones, Storage Area Networks (SAN), Data Centers and Central Offices.

Now you`re wondering, “What do I do if I need to go in and out? Do I need to buy two types of cables and splice them at building entry?” Actually, until a few years ago, that is exactly what you had to do. Fortunately, design and materials have evolved to meet the needs of indoor/outdoor applications with a variety of cable choices. The most prevalent choice today is a loose-tube, gel-filled, riser-rated cable. This design offers all the proper outdoor protection, and the riser rating allows it to be run within the building (except in the horizontal). There are also loose-tube plenum-rated cables available.