MIL-PRF-49291D
3.5.1.1 Splices. Unless otherwise specified (see 3.1 and 6.2), the fibers shall be splice-free. When
specified, spliced fibers shall meet all dimensional, mechanical, and environmental requirements as
unspliced fiber. The coating of spliced fibers shall be reconstituted in such a manner as to not change the
diameter of the coating by more than the percentage specified (see 3.1). When specified, splice loss
shall be as specified in the applicable specification sheet (see 3.1).
3.5.1.2 Geometry (fiber). The fiber geometry shall be as specified below.
3.5.1.2.1 Core diameter (Type I fiber only). When tested in accordance with 4.7.2.1.1, the core
diameter shall be as specified (see 3.1).
3.5.1.2.2 Mode field diameter (Type II fiber only). When tested in accordance with 4.7.2.1.2, the
nominal mode field diameter and mode field diameter tolerance for Type II fiber shall be as specified (see
3.1).
3.5.1.2.3 Core ovality (core noncircularity) (Type I fiber only). When tested in accordance with
3.5.1.2.4 Cladding diameter. When tested in accordance with 4.7.2.1.4, the cladding diameter shall be
as specified (see 3.1).
3.5.1.2.5 Cladding ovality (cladding noncircularity). When tested in accordance with 4.7.2.1.5, the
cladding ovality shall be as specified (see 3.1).
3.5.1.2.6 Core-to-cladding offset (core/cladding concentricity). When tested in accordance with
3.5.1.2.7 Coating diameter. When tested in accordance with 4.7.2.1.7, the coating diameter shall be
as specified (see 3.1).
3.5.1.2.8 Overall coating concentricity error. When tested in accordance with 4.7.2.1.8, the overall
coating concentricity error shall be as specified (see 3.1).
3.5.1.3 Fiber mass/unit length (kg/km). When tested in accordance with 4.7.2.2, the fiber mass/unit
length expressed as kilograms/kilometer shall be as specified (see 3.1).
3.5.2 Tensile proof. When tested in accordance with 4.7.2.3, the proof tested tensile strength of the
fiber shall be as specified (see 3.1).
3.5.3 Mechanical strippability. When tested in accordance with 4.7.2.4, the fiber coating shall be
mechanically strippable with commercially available stripping tools. There shall be no scratches, nicks, or
inclusions in the stripped fibers or residual coating material on the stripped fiber which cannot be easily
removed with a cotton pad or a wipe moistened with a fiber optic grade cleaning solution. For 250 µm
coating, the maximum strip force shall be not less than 1.8 N and not greater than 13.2 N. For 500 µm
coatings, the maximum strip force shall be not less than 1.8 N and not greater than 20 N.
3.5.4 Continuous lengths. Unless otherwise specified (see 3.1), the individual continuous lengths of
finished fiber in each unit of product shall be 1100 meters minimum. A spool shall contain no more than
one continuous length of fiber.
3.6 Optical performance.
3.6.1 Change in optical transmittance. When tested in accordance with 4.7.3.1, the change in optical
transmittance for the specified sample due to exposure of fiber to mechanical and environmental tests
shall be not greater than 0.5 decibel (dB) for Type I fibers and 0.3 dB for Type II fibers.
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