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250μm loose-buffered optical cables and 900μm tight-buffered optical cables are two different types of optical cables, sharing the same core diameter, cladding, and coating. However, there are still differences between the two, reflected in their structure, function, advantages, and disadvantages, which also lead to differences in their applications. This article will explain these two different types of optical cables.
Comparison Between 250μm Bare Fiber and 900μm Tight-Buffered Optical Fiber Cable
Loose-tube optical fiber structures spirally place the fibers within a semi-rigid tube, allowing cable extension without stretching the fibers themselves. As shown in the figure below, a 250μm loose-tube optical fiber consists of a core, a 125μm cladding, and a 250μm coating. Generally speaking, the number of cores in a 250μm loose-tube cable ranges from 6 to 144. Except for 6-core loose-tube cables, other cables are typically constructed with 12 cores as the base unit.
Unlike the loose-tube structure mentioned above, 900μm tight-buffered optical fiber adds a hard plastic jacket over the 250μm loose-tube structure for added protection. As shown in the figure above, 900μm tight-buffered optical fiber consists of a core, a 125μm cladding, a 250μm coating (soft plastic), and a hard plastic jacket. The coating and jacket help isolate moisture from the fiber core and prevent core exposure due to bending or compression when the cable is laid underwater. The number of fiber cores in a 900μm tight-buffered optical cable typically ranges from 2 to 144, with cables with larger core counts typically constructed in units of 6 or 12 cores.
The following specification table provides detailed parameters for 250μm loose tube optical fiber and 900μm tight tube optical fiber.
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250μm loose tube optical fiber
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900μm tight-sleeved optical fiber
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fiber core
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9μm, single mode; 50μm or 62.5μm, multimode;
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9μm, single mode; 50μm or 62.5μm, multimode;
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cladding
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125μm
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125μm
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coating
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Soft plastic; 250μm
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Soft plastic; 250μm
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Layer
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——
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Hard plastic, 900μm
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How to Choose Between 250μm Loose-Buffered Fiber Cable and 900μm Tight-Buffered Fiber Cable?
Due to the different functional characteristics of 250μm loose-buffered optical cables and 900μm tight-buffered optical cables, their usage situations are also different, as follows.
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250μm loose tube optical cable
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900μm tight buffer optical cable
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High density; low shrinkage and high tensile strength; mechanical strength; moisture resistance; UV protection; high temperature resistance; flame retardant LSZH polymer; enhance system performance.
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High flexibility; high tensile strength; good mechanical and temperature properties; water blocking; UV protection; higher survivability standards; glass fiber reinforcement; easy termination.
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250μm loose-tube fiber optic cables are suitable for harsh environments and are widely used outdoors. Compared to 900μm tight-buffered fiber optic cables, 250μm loose-tube cables offer higher tensile strength, moisture resistance, and high-temperature resistance, making them suitable for environments with fluctuating temperatures and high humidity. However, excessive stretching can pull the fiber core out of the gel. Furthermore, when cabling requires multiple bends, 250μm loose-tube cables may not be a good choice. The following highlights why 250μm loose-tube fiber optic cables are suitable for outdoor environments.
- Waterproof - By using gel to fill the internal structure of the optical cable, the optical cable is protected as much as possible and can effectively prevent water penetration.
- Anti-UV – The outer sheath contains carbon black, which can effectively protect against UV rays.
- Mechanical resistance – This type of optical cable has an armored layer that can withstand greater mechanical forces and improve durability.
- Pipe space - From the above, we can see that the structures of 250μm loose tube optical cable and 900μm tight buffer optical cable are different, and the size of 250μm loose tube optical cable is almost one-third of 900μm tight buffer optical cable. Therefore, compared with 900μm tight buffer optical cable, 250μm loose tube optical cable occupies less pipe space, especially when the number of optical fibers is large, which can effectively reduce the total installation cost.
900μm tight-buffered optical fiber cables are ideal for indoor applications. Compared to 250μm loose-buffered cables, 900μm tight-buffered cables offer greater robustness, making them more suitable for medium-distance LAN/WAN connections or longer-distance indoor installations, even underground. The following sections will focus on why 900μm tight-buffered optical cables are preferred for indoor environments.
- No gel required - Indoor applications do not require the use of protective gel, so it is more suitable for installation in risers perpendicular to the building.
- Flexibility - The absence of reinforcement members makes the cable more flexible. In addition, it can be pulled around multiple bends or hung vertically without worrying about the fiber core axis moving.
- Easy to splice - Compared with 250μm loose-tube cable, 900μm tight-buffered cable is less fragile and its individual fiber cores are easier to handle. No messy gel to clean up, no fan-out kits for splicing or termination, just crimp the connector directly to each fiber.
Summarize
After understanding the structural and functional differences between 250μm loose-buffered and 900μm tight-buffered cables, it's easy to distinguish their applications. Before installation, be sure to select the appropriate cable based on the application environment.
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