Loose-tube 250um Fiber Cable vs. Tight-buffered 900um Fiber Cable

Posted on April 9, 2020
August 3, 2020

Loose-tube 250um fiber cable and tight-buffered 900um fiber cable are categorized as two fiber cable types. Both of them have the same 250um bare fiber and featuring the same-sized fiber core. However, their differences still exist and lie in the cable construction, features, cons, and pros, etc., which brings about the different applications. This article will lead you to clarify the two different types of fiber cables.

A Comparison Between 250um Loose Tube Fiber and 900um Tight Buffer Fiber

For a loose-tube construction design, the fiber is laid helically into semi-rigid tubes, allowing the cable to extend without stretching the fiber itself. A 250um loose tube fiber or 250um bare fiber contains a fiber core, 125um cladding and 250um coating (soft plastic). In a 250um loose-tube fiber cable, the number of the contained fibers typically range from 6 to 144. Except for the 6-fiber cable type, the fibers are normally grouped into sets of 12 for maximum density.


Distinct from the previous loose-tube fiber type, the 900um tight-buffered fiber adds an additional layer of hard plastic over the 250um fibers for protection. A 900um tight-buffered fiber also contains a fiber core and 125um cladding, but with the 250um coating for soft plastic and 900um tight buffer for hard plastic. The two-layer coating—plastic and waterproof acrylate helps to keep moisture away from the fiber, protecting the core from being exposed when bent or compressed underwater. The internal fiber counts ranging from 2 to 144, with larger fiber counts featuring fiber subunits of 6 or 12 fibers within the tight-buffered 900um fiber cables.

Here is a specification table that makes a comparison of the parameters of these two types of fibers.

Loose-tube 250um Fiber Tight-buffered 900um Fiber
Core I9um, SMF; 50um or 62.5um, MMF 9um, SMF; 50um or 62.5um, MMF
Cladding 125um 125um
Coating Soft plastic: 250um Soft plastic: 250um
Tight Buffer / Hard plastic: 900um

How to Choose From Loose-tube 250um Fiber Cable and Tight-buffered 900um Fiber Cable?

The above mentioned two fiber types are in forms of loose-tube 250um fiber cables and tight-buffered 900um fiber cables, which are applied in different situations on account of different features.

Loose-tube 250um Fiber Cable Tight-buffered 900um Fiber Cable

High Density

Low Shrinkage & High Tensile Strength

Mechanical Forces Resistance


UV Protection

Extreme Temperature Resistance

E-retardant LSZH polymer

Enhances system performance

High Flexibility

High Tensile Strength

Good Mechanical & Temperature Performance


Anti-ultraviolet Performance

Higher Survivability Standard

Glass Yarn Strength Members

Ease of Termination

The tight-buffered 900um fiber cable is ideally suited for indoor applications. Featuring with sturdier natures than loose-tube cable, the tight-buffered cable is more available for moderate-length LAN/WAN connections or long indoor runs, and even direct burial. The following reasons will illustrate why the tight-buffer 900um fiber cables are optimal for indoor environments.

  • No Need for Gel—indoor applications don't require to use protective gel, allowing them suitable for installing vertically through building risers.

  • Flexibility—No stiff strength member is needed, making the cable more flexible. Besides, it is allowed to be pulled around multiple bends or hung vertically without worrying about the "fiber axial migration" issue.

  • Easy Splicing—The 900um jacket makes the handling of each core easier, which is less fragile than 250um at the same time. No messy gel to clean up and no fan-out kit for splicing or termination requirements, just crimp connectors directly to each fiber.

  • Designed for harsh environments particularly, the loose-tube 250um fiber cables are widely accepted for armored outdoor applications. That is because the loose-tube fiber cable has a higher tensile strength than a tight buffer one, fitting for the temperature changes and high-humidity environments. However, excess cable strain will force fibers to emerge from the gel. When the cables need to be routed around multiple bends, this may not provide a good choice. Here are the reasons that explain the outdoor applications of loose-tube 250um fiber cables:

    • Water Resistant—By utilizing gel-filled tubes and water swelling tapes, the cables can provide maximum protection against water penetration and migration.

    • UV Resistant—Outer jacket contains carbon black, which provides UV protection for applications involving exposure to direct sunlight.

    • Mechanical Resistant—To provide additional robustness, an armored layer can be provided.

    • Duct Space—Due to the cable construction, loose tube cables are nearly half the size of the tight-buffered cable so that it will take less duct space than tight-buffered cables especially for higher fiber counts contributing to overall lower installation costs.

    • Brief Summary

      After figuring out the construction differences between loose-tube 250um fiber cables and tight-buffered 900um fiber cables, the applications for these two types of fiber cables are based on their distinctiveness. Before installing, make sure that what kind of fiber cables you need for your specific deployment.