| 单词 | bend diameter |
| 释义 | bend diameter The diameter of the bend in a wire, fiber, or cable.Too severe a bend will cause a crimp, crack, or break in a wire or fiber, in the shielding or insulation surrounding it or the cable in which it resides, or otherwise will compromise the integrity of the physical medium or cabling system. Cable specifications include bend tolerances, generally stated in terms of minimum bend diameter. Absent those specifications, there are rules of thumb that guide in cable installation. • Fiber optic cable: The dynamic bend, i.e., the bend in a cable under short-term physical load while being installed, should be no less than 20–15 times the outside diameter of a fiber optic cable at the point that the pulling load (i.e., tension in the cable sheath) approaches the maximum tensile strength of the cable. Dynamic bend minimums are intended to protect the cable from physical damage during installation.The static bend, i.e., the long-term bend in a cable at rest, should be no less than 10 times the outside diameter (OD) of a fiber optic cable. Static bend minimums are intended primarily to avoid bending loss, which is the loss of optical energy into the fiber cladding. If the bend is too severe, the angle of incidence, i.e., the angle at which the optical signal strikes the core/cladding interface, is too severe and the signal is not reflected back into the core. Rather, it penetrates the core/cladding interface and is lost in the cladding, or escapes the fiber altogether. • Unshielded twisted pair (UTP): Manufacturers typically recommend a minimum bend radius of one (1) inch for a four-pair Category 5 UTP cable.The rule of thumb is four (4) times the outside diameter of the cable. A tighter bend can disturb the critical geometry of the twists, affecting the local impedance and balance, and reducing performance through increased sensitivity to external noise and increased near-end cross talk (NEXT) within the cable. Also, long-term damage to the cable jacketing and insulating material can result from bending stress. • Coaxial cable: The rule of thumb is bend diameter no less than 6 times the outside diameter of the cable. A tighter bend can cause long-term damage to the cable jacketing, outer shield or conductor, and insulating material. Some specifications state bend tolerance in terms of the bend radius, which is half the bend diameter. See also angle of incidence, NEXT, rule of thumb, and tensile strength. |
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