Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1990-10-10
1992-07-14
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356 731, H01J 516
Patent
active
051305356
ABSTRACT:
Variations in bending loss for relatively small radii bends along a length of optical fiber (26) are determined by using an optical time domain reflectometer (20) to measure the backscattering power as a function of distance along the fiber in one direction along the length of fiber by launching light energy into one end of the fiber. Then the backscattering power is measured as a function of distance along the fiber in the opposite direction from an opposite end by launching light energy into an opposite end of the fiber. Mathematical representations of backscattering forward and reverse signals for corresponding points along the length of the fiber are added to provide a quantity which is related to mode field diameter of the fiber. Variations in the mode field diameter are indicative of variations in the bending loss along the length of fiber. By measuring the bending loss at the end points of the length of fiber, the absolute bending loss along the length of fiber can be estimated from the above quantity.
REFERENCES:
patent: 4741615 (1988-05-01), Calzavara et al.
patent: 4838690 (1989-06-01), Buckland et al.
patent: 4902327 (1990-02-01), Levinson
Kowaliuk and Ferner, "A Technique to Estimate the Cutoff Wavelength Profile in Single Mode Fibers Using A Switchable Dual Wavelength OTDR," Technical Digest, Symposium on Optical Fiber Measurements, 1988, Boulder Colo. NBS Speial Pub. 748 pp. 15-18.
"Backscattering Measurements In Optical Fibers: Separation of Power Decay From Imperfection Contributions," Electronics Letters, Jul. 19, 91979, vol. 15, No. 15, pp. 467-469.
Buckland and Nishimura, "Bidirectional OTDR Measurements Utilizing An Improved Folded-Path Technique", Technical Digest of the Symposium on Optical Fiber Measurements, Boulder Colo. NBS Special Pub. #748, 1988, pp. 123-124.
Kummer Raymond B.
Shute, Sr. Marcus W.
AT&T Bell Laboratories
Nelms David C.
Shami K.
Somers Edward W.
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