Selecting the right type of fiber optic cable boils down to the applications and the installation. This post will introduce and compare two fiber optic cable types based on different cable constructions—loose-tube and tight-buffered fiber optic cable.

1. WHITE PAPER
FS.COM White Paper | Loose-Tube VS. Tight-Buffered Fiber Optic Cable
It is known that fiber optic cable has been the preferred medium for the data center backbone due
to channel capacity and scalability, total immunity to electromagnetic interference (EMI) and radio
frequency interference (RFI), elimination of the crosstalk inherent in copper cabling (like twinax
cable), smaller diameter, and ease of installation, particularly when using pre-terminated modular
trunk cables. Selecting the right type of fiber optic cable boils down to the applications and the
installation. This post will introduce and compare two fiber optic cable types based on different
cable constructions—loose-tube and tight-buffered fiber optic cable.
Loose-Tube Fiber Optic Cable Overview
In loose-tube construction, the fiber is laid helically into semi-rigid tubes, allowing the cable to
stretch without stretching the fiber itself, which can protect the fiber from tension during laying and
due to temperature changes. Loose-tube fiber may be “dry block” or gel-filled. Dry block offers less
protection to the fiber than gel-filled, but costs considerably less. Loose-tube fiber cable comes in
various fiber counts that typically range from 6 to 144, with some manufacturers offering higher
counts up to 216 fibers. Except a 6-fiber cable, the fibers are grouped into sets of 12 for maximum
density.
 Structure of Loose-Tube Cable
The figure 1 shows the main components used to construct a Loose-tube cable.
Figure 1 Structure of Loose-Tube Cable
Loose-Tube VS.
Tight-Buffered Fiber
Optic Cable

2. WHITE PAPER
FS.COM White Paper | Loose-Tube VS. Tight-Buffered Fiber Optic Cable
Multiple 250um coated bare fibers in loose tube.
One or more loose tubes holding 250um bare fibers. Loose tube stranded around the central
strength member.
Moisture blocking gel in each loose tube for water blocking and protection of 250um fibers.
Central strength member in the center of the cable and is stranded around by loose tubes.
Aramid Yarn as strength member.
Ripcord for easy removal of outer jacket.
Outer jacket(PVC is most common for outdoor cables because of its moisture resistant, abrasion
resistant and stable over wide temperature range characteristics).
 Advantages of Loose-Tube Cable
Extreme Temperature Resistant: Loose-tube cable establishes a strain-free environment for the
optical fiber by mitigating the influence of external effects, which makes it perform well at extreme
temperatures. Besides, this characteristic also enhances the performance of the loose-tube cable
design under a variety of mechanical forces, such as tensile, flexure, twisting, crush, etc.
Water-blocking Characteristic: As we all know, the core fiber of loose-tube cable is surrounded with
a dry water-swellable tape and yarns, or with a gel, which can effectively stop the entry and
migration of water.
UV Protection: The outer jacket of loose-tube cable consists of carbon black, which can provide
maximum ultraviolet protection, making the cable able to withstand direct exposure to ultraviolet
sunlight in aerial installations.
Tight-Buffered Fiber Optic Cable Overview
Instead of a loose tube, the fiber may be embedded in a heavy polymer jacket, commonly called
“tight buffer” construction. Tight-buffered cables are offered for a variety of applications, but the
two most common are “breakout” and “distribution”. Tight-buffered cable comes in fiber counts
ranging from 2 to 144 fibers, with larger fiber counts featuring fiber subunits of 6 or 12 fibers within
the cable. For example, a 144-fiber cable usually has twelve 12-fiber subunits while a 36-fiber cable
could have six 6-fiber subunits or three 12-fiber subunits.
 Structure of Tight-Buffered Cable
The figure 2 shows the structure of tight-buffered cable.
Figure 2. Structure of Tight-Buffered Cable

3. WHITE PAPER
FS.COM White Paper | Loose-Tube VS. Tight-Buffered Fiber Optic Cable
Multiple 900um tight-buffered fibers stranded around the central strength member.
Central strength member in the center of the cable.
Aramid Yarn(trade name Kevlar) wrapped around the fibers for physical protection and cable
pulling.
Ripcord for easy removal of outer jacket.
Outer jacket or sheath(usually PVC).
 Advantages of Tight-Buffered Cable
Easy to Install: Tight-buffered cables are easier to install, because there is no messy gel to clean up
and they don’t require a fan-out kit for splicing or termination. You can crimp connections directly
to each fiber.
Higher Survivability Standard: Based on military technology for survival under mechanical and
environmental stresses.
Flexibility: No stiff strength member is needed, making the cable more flexible. The cable is also
“tight bound” allowing it to be pulled around multiple bends or hung vertically without causing
“fiber axial migration”.
Which One to Choose—Loose-Tube or Tight-Buffered?
After we have introduced these two types of fiber optic cables, people may wonder which one is
the best for their project. Actually, these two cable types are deployed in different applications.
Loose-tube cable is specifically designed for harsh environments. It has a water-resistant gel that
surrounds the fibers, which helps the fibers from moisture, making the cable ideal for harsh,
high-humidity environments where water or condensation can be a problem. The gel-filled tubes
can also expand and contract with temperature changes. Loose-tube cable has a higher tensile
strength than tight-buffered cable. But it is not the best choice when cable needs to be routed
around multiple bends, which is often true in indoor applications. Excess cable strain can force
fibers to emerge from the gel.
Tight-buffered cable is optimized for indoor applications. Because it’s sturdier than loose-tube cable,
it is more available for moderate-length LAN/WAN connections or long indoor runs, and even direct
burial. Tight-buffered cable is also recommended for underwater applications.
Summary
Choose the right cable types for your applications can effectively improve network performance and
ensure the life span of the whole project. FS.COM offers a wide range of loose-tube and
tight-buffered cables in different fiber counts and with single-mode fiber or multimode fiber. For
more detailed information, please visit FS.COM.

4. WHITE PAPER
FS.COM White Paper | Loose-Tube VS. Tight-Buffered Fiber Optic Cable
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Notice: This document is for informational purposes only and does not set forth any warranty, expressed or
implied, concerning any equipment, equipment features, or service offered or to be offered by FS.COM.
FS.COM reserves the right to make changes to this document at any time, without notice, and assumes no
responsibility for its use. This information document describes features that may not be currently available.
Contact a FS.COM sales team for information on feature and product availability.
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