2024-03-06
The translation in English would be: "Fiber optics are fibers made of glass or plastic, which are inherently fragile and prone to breakage. By encapsulating fine optical fibers in plastic sheaths, they can bend without breaking. Cables packaged in this way are known as fiber optic cables. However, can fiber optic cables be bent freely?
Due to the sensitivity of optical fibers to stress, bending the fibers can cause light signals to escape the fiber cladding, especially when the bend becomes sharp, resulting in more leakage. Additionally, bending can lead to microcracks, permanently damaging the fibers. Finding points of microbending is difficult and requires expensive testing equipment, so at least cleaning or replacing fiber optic patch cables is necessary. Bending optical fibers causes attenuation, with the amount of attenuation increasing as the bending radius decreases. At 1550 nm, the attenuation caused by bending is greater than at 1310 nm, and even greater at 1625 nm. Therefore, when installing fiber optic patch cables, especially in high-density wiring environments, it is important to ensure that the bending of the cables does not exceed their tolerable bending radius. So, what is the appropriate bending radius?
The bending radius of a fiber optic cable refers to the angle at which the cable can safely bend within a specific range. The minimum bending radius varies for each type of cable or patch cord and may depend on the cable's type or manufacturing method. Typically, the minimum bending radius is determined by the diameter and type of the cable, calculated using the formula: Minimum Bending Radius = Cable Outer Diameter × Cable Multiple.
The ANSI/TIA/EIA-568B.3 standard defines the minimum bending radius and maximum tensile strength for 50/125 micron and 62.5/125 micron fiber optic cables. The minimum bending radius of a cable depends on its specific type. Under no tension, it generally should not be less than ten times the cable's outer diameter (OD); under tension, it should be fifteen times the cable's outer diameter. Traditional single-mode patch cords typically define the minimum bending radius as ten times the outer diameter of the sheathed cable or 1.5 inches (38mm), whichever is greater. Currently, the minimum bending radius for commonly used G652 fiber optic cable is 30mm.
In recent years, the G657 fiber optic series, which has begun to be widely used, features smaller bending radii, including G657A1, G657A2, and G657B3. The minimum bending radius for G657A1 is 10mm, G657A2 is 7.5mm, and G657B3 is 5mm. These fibers, based on G652D fibers, have improved bending attenuation characteristics and enhanced geometric properties, thus improving fiber connectivity performance. They are also known as bend-insensitive fibers. Primarily used in FTTx and FTTH, they are suitable for indoor narrow spaces or corner applications.
Fiber breakage and increased attenuation can significantly affect long-term network reliability, network operating costs, and the ability to maintain and grow customer base. Therefore, it is important to have a clear understanding of the minimum fiber optic bending radius to ensure that fiber cables or patch cords remain in good working condition.
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