Fiber Cable Manufacturer
1-288 cores GYFTY non-metallic Optical Fiber Cable
Central strength member
Vary from 7 to 14mm
aerial or pipeline cable networking system
1/2/3/4/5km km each exporting wooden drums
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Optical Fiber Testing - Loss and Attenuation Coefficient
For optical fiber, testing includes fiber geometry, attenuation and bandwidth. The most fundamental parameter for optical fiber is geometry, since the dimensions of the fiber determine its ability to be spliced and terminated to other fibers. The core diameter, cladding diameter and concentricity are the most important factors on how well one can connect or splice two fibers. Thus manufacturers work very hard to control these parameters, including continuous testing throughout the manufacturing process.
While testing diameter and concentricity may sound simple, measurements must be made to submicron precision. The process is complicated by the fact that the material is transparent and the dimensions are small enough to reach the limits of optical measurements.
Fiber Types and Typical Specifications
Fiber Type Core/Cladding Diameter Attenuation Coefficient
850 nm 1300 nm 1550 nm
POF 1 mm 0.2-1 dB/meter @650 nm
Step Index 200/240 microns 6 dB/km
Graded Index Multimode 50/125 microns 3 dB/km 1 dB/km
62.5/125 microns 3 dB/km 1 dB/km
85/125 microns* 3 dB/km 1 dB/km
100/140 microns* 3 dB/km 1 dB/km
Singlemode 9/125 microns
0.4-0.5 dB/km 0.2-0.3 dB/km
* obsolete designs
The attenuation of the optical fiber is a result of two factors, absorption and scattering. The absorption is caused by the absorption of the light and conversion to heat by molecules in the glass. Primary absorbers are residual OH+ and dopants used to modify the refractive index of the glass. This absorption occurs at discrete wavelengths, determined by the elements absorbing the light. The OH+ absorption is predominant, and occurs most strongly around 1000 nm, 1400 nm and above1600 nm.
The largest cause of attenuation is scattering.Scattering occurs when light collides with individual atoms in the glass and is anisotrophic. Light that is scattered at angles outside the numerical aperture of the fiber will be absorbed into the cladding or transmitted back toward the source Scattering is also a function of wavelength, proportional to the inverse fourth power of the wavelength of the light. Thus if you double the wavelength of the light, you reduce the scattering losses by 2 to the 4th power or 16 times. Therefore , for long distance transmission, it is advantageous to use the longest practical wavelength for minimal attenuation and maximum distance between repeaters. Together, absorption and scattering produce the attenuation curve for a typical glass optical fiber shown above.
Fiber optic systems transmit in the "windows" created between the absorption bands at 850 nm, 1300 nm and 1550 nm, where physics also allows one to fabricate lasers and detectors easily. Plastic fiber has a more limited wavelength band, that limits practical use to 660 nm LED sources.