Fiber Optic Cables Information

Fiber optic cables are composed of one or more transparent fibers enclosed in protective coverings and strength members. Cable types can include simplex, duplex, multifiber, patch cord, and bare fiber.  Simplex cables are fiber optic cable with a single optical fiber.  Duplex cables are fiber optic cable with two optical fibers.  Multifiber cable is a fiber optic cable with several optical fibers.  Patch cords are short lengths of fiber optic cable with connectors.  Bare fiber refers to a fiber optic core and cladding only.  Fiber types can be single mode or multimode.  Single mode describes a fiber with a small core, only a few times the wavelength of light transmitted, that only allows one mode of light to propagate. It is commonly used with laser sources for high speed, long distance links.  Multimode describes a fiber with core diameter much larger than the wavelength of light transmitted that allows many modes of light to propagate. Commonly used with LED sources for lower speed, short distance links.

Common connector types for fiber optic cable include biconic, D4, ESCON, FC, FDDI, LC, loopback, MTP, MT-RJ, MU, SC, SMA, and ST.  Some fiber optic cable comes without connectors.  Important parameters to consider when searching for fiber optic cable include fiber core size, cable diameter, and cable weight.  Fiber core size is the size of the light-conducting central portion of an optical fiber, composed of material with a higher index of refraction than the cladding. The core size is smaller for single mode and larger for multimode fibers.  Cable diameter refers to the diameter of the fiber optic cable including jacket. 

Cable performance specifications to consider when searching for fiber optic cable include wavelength, numerical aperture, maximum attenuation, and bending radius.  The wavelength refers to the wavelength that the cable was designed for.  Numerical aperture is the light-gathering ability of a fiber; the maximum angle to the fiber axis at which light will be accepted and propagated through the fiber. The measure of the light-acceptance angle of an optical fiber, NA = sin a, where A is the acceptance angle. NA is also used to describe the angular spread of light from a central axis, as in exiting a fiber, emitting from a source, or entering a detector.  Maximum attenuation is the decrease in signal strength along a fiber optic waveguide caused by absorption and scattering. Attenuation is usually expressed in dB/km.  Bending radius is the smallest radius an optical fiber or fiber cable can bend before increased attenuation or breakage occurs.  Common features for fiber optic cable include polarization maintaining, graded index, and metallized.  A polarization maintaining cable has fiber that maintains the polarization of light that enters it.  A graded index fiber optic cable has optical fiber in which the refractive index of the core is in the form of a parabolic curve, decreasing toward the cladding.  Metallized fibers are coated with metals for increased temperature resistance, soldering, and harsh environments.  An important environmental parameter to consider is the operating temperature.

• Multimode Fiber Optic Cable
  of coverage in any fiber optic cable guide. Why? Because multimode is still the fiber of choice for many applications....
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• Hermetically Sealing a Fiber Optic Cable in a Kovar Ferrule (.pdf)
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