Patent ID: 6633709
Filing Date: 2003-10-14
Classification: G02B

Abstract:
An optical fiber loose tube cable, comprising:(a) a plurality of stacked fiber optic ribbons or subunits; (b) a plurality of water blocking yarns extending generally along the length of said stack of fiber optic ribbons and positioned around at least a portion of the circumference of said stack of fiber optic ribbons, said plurality of water blocking yarns possessing water swellable characteristics; (c) a buffer tube having an interior channel larger than said stack of fiber optic ribbons, with said stack of fiber optic ribbons and said plurality of water blocking yarns loosely disposed in said buffer tube; (d) wherein the swell capacity (Mcapacity) of said plurality of water blocking yarns exceeds the critical mass of water (Mcritical) that could enter said buffer tube by a factor of 2.0 or more, said swell capacity being determined by the formula: Mcapacity=(N)(d)(B) â€ƒwherein N=number of water blocking yarns d=yarn denier B=absorbency and said critical mass of water being determined by the formula:Mcritical=(Atubeopen)(&rgr;water) wherein Atubeopen=open area of buffer tube &rgr;water=density of water.