| 摘要 |
A flame-retardant optical fiber cable tubing (10) bundle which can be vertically mounted in the shaft of a building comprised of a plurality of tubes (10); a first thermoplastic layer (14) surrounding the tubes (10); and, a tape (16) wrapped spirally along the longitudinal axis of the first thermoplastic layer (14). A second thermoplastic layer (18 ) surrounds the tape. A method for complying with the UL 1666 fire test procedure for a cable tubing bundle intended for vertical installation includes the steps of liquefying a cross-sectional area of a thermoplastic layer (14) of the cable tubing bundle; forcing the flow of the liquified thermoplastic inwardly to the center of the cable tubing bundle; and, charring the liquified thermoplastic to form a cross-sectional area of solid material in the interior of the cable tubing bundle.
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