Importance

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Abstract

The inventive multimode fiber has total loss at an operating wavelength of at least about 0.8 db/km, typically not more than 5 db/km. At least 0.3 db/km, preferably 0.5 db/km, of the loss is due to the presence in the fiber of radially nonuniformly distributed attenuation centers, with the concentration of the centers differing by at least about 10% between the concentration minimum and the maximum. The resulting differential mode attenuation can lead to fiber having larger bandwidth than analogous fiber without differential attenuation. Preferred distributions of attenuation centers have the concentration maximum either at or near the fiber axis, or at or near the core/clad interface. Preferred attenuation centers are absorbers, with OH being a preferred absorber. The fiber is produced by a method comprising a procedure designed to result in the above-described distribution of attenuation centers, typically by maintaining the distribution introduced into the preform during preform production, or by deliberate introduction of attenuation centers into the preform during preform production.

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First Claim