Optical fiber is a fiber made of glass or plastic, and the fiber itself is very fragile and breaks easily. Encapsulating the tiny fiber in a plastic sheath allows it to be bent without breaking. The cable with the optical fiber wrapped in the protective sheath is called an optical cable. Can an optical cable be bent at will?
Since fiber is sensitive to strain, bending it can cause the optical signal to leak through the fiber cladding, and as the bend becomes more pronounced, the optical signal will leak even more. Bending can also cause microcracks that can permanently damage the fiber. Besides the problem itself, microbending points are difficult to locate and require expensive testing equipment; at the very least, the jumpers must be cleaned or replaced. Fiber bending can cause fiber attenuation. The amount of attenuation due to fiber bending increases as the bend radius decreases. Attenuation due to bending is greater at 1550 nm than at 1310 nm, and even greater at 1625 nm. Therefore, when installing fiber jumpers, especially in a high-density cabling environment, the jumper should not be bent beyond its acceptable bend radius. So, what is the appropriate bend radius?
The bend radius of a fiber is the angle at which the fiber can be safely bent at any given point. Fiber bend radii differ for all cables and patch cords and can vary depending on the cable type and manufacturing process. The minimum bend radius depends on the diameter and type of optical cable; the formula typically used is: minimum bend radius = outer diameter of optical cable x multiple of the optical cable diameter.
The new ANSI/TIA/EIA-568B.3 standard defines minimum bend radius and maximum tensile strength standards for 50/125 micron and 62.5/125 micron fiber optic cables. The minimum bend radius depends on the specific fiber optic cable. Under no tension, the bend radius of the fiber optic cable should generally not be less than ten times the outer diameter (OD) of the fiber optic cable. Under tensile load, the bend radius is 15 times the outer diameter of the fiber optic cable. Industry standards for traditional single-mode patch cables typically specify a minimum bend radius of ten times the outer diameter of the jacketed cable or 1.5 inches (38 mm), whichever is greater. The commonly used G652 fiber has a minimum bend radius of 30 mm.
G657, which has been implemented in recent years, has a smaller bend radius, including G657A1, G657A2, and G657B3. The minimum bend radius for G657A1 is 10 mm, for G657A2 it is 7.5 mm, and for G657B3 it is 5 mm. This type of fiber is based on G652D fiber, which improves bend attenuation characteristics and the fiber's geometric features, thus enhancing its connection characteristics. It is also known as bend attenuation-insensitive fiber. Primarily used in FTTx and FTTH, it is suitable for use in small indoor spaces or corners.
Both fiber breaks and increased attenuation can significantly impact long-term network reliability, network operating costs, and the ability to maintain and grow a customer base. Therefore, we need to clearly understand the minimum fiber bend radius to keep the cable or patch cord in good working condition.
Post time: Nov-11-2022
