MIL-PRF-49291D
3.6.2 Attenuation rate. When tested in accordance with 4.7.3.2, the fiber attenuation rate at the
wavelengths of operation shall be as specified (see 3.1).
3.6.2.1 Attenuation uniformity. When tested in accordance with 4.7.3.2.3, there shall be no
discontinuities in attenuation along the length of the Type I fiber greater than 0.2 dB and no discontinuities
in attenuation along the length of the Type II fiber greater than 0.1 dB, for the specified wavelength.
3.6.3 Numerical aperture (for Type I fiber only). When applicable (see 3.1) and when tested in
accordance with 4.7.3.3, the numerical aperture shall be as specified.
3.6.4 Bandwidth (for Type I fiber only). When tested in accordance with 4.7.3.4, the fiber bandwidth at
the wavelengths of operation shall be as specified (see 3.1).
3.6.5 Macrobend attenuation. When tested in accordance with 4.7.3.5, the macrobend attenuation
shall be not greater than 0.5 dB for Type I fibers and the macrobend attenuation shall be not greater than
0.1 dB at 1300 ± 20 nm or 1.0 dB at 1550 ± 25 nm for Type II fibers unless otherwise specified (see 3.1).
The mandrel radius shall be 3.8 ± 0.05 centimeters and the number of turns shall be 100.
3.6.6 Chromatic dispersion. When tested in accordance with 4.7.3.6, unless otherwise specified, the
zero dispersion wavelength of dispersion-unshifted Type II fibers shall be 1310 ± 15 nm with a maximum
dispersion value of 3.5 picoseconds per nanometer-kilometer (ps/nm-km) from 1290 to 1330 nm. When
specified, the dispersion at other wavelengths shall be as specified (see 3.1). The value of the dispersion
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slope at the zero dispersion wavelength shall be not greater than 0.1 ps/nm -km. The dispersion
characteristics for all other Type II fibers shall be as specified (see 3.1). When specified, the Type I fiber
zero dispersion wavelength and the dispersion slope at the zero dispersion wavelength shall be as
specified (see 3.1).
3.6.7 Cut-off wavelength (for Type II fiber only). When tested in accordance with 4.7.3.7, unless
otherwise specified (see 3.1), the cut-off wavelength of dispersion unshifted Type II fibers shall be
between 1130 and 1330 nm. The cutoff wavelength for all other Type II fibers shall be as specified (see
3.1).
3.6.8 Transient attenuation (for Type I fiber only). When specified and when tested in accordance with
4.7.3.8, the transient attenuation for Type I fibers shall be as specified (see 3.1).
3.7 Environmental performance.
3.7.1 Thermal shock. When tested in accordance with 4.8.1, there shall be no cracking or melting of
the fiber coating material and the change in optical transmittance shall not exceed the requirements of
3.7.2 Temperature humidity cycling. When tested in accordance with 4.8.2, there shall be no swelling
or softening of the coating material which causes the fiber diameter or length to exceed the specified
dimensional tolerances (see 3.1). The change in optical transmittance shall not exceed the requirements
3.7.3 Temperature cycling. When tested in accordance with 4.8.3, there shall be no cracking or
melting of the fiber coating material and the change in optical transmittance shall not exceed the
requirements of 3.6.1.
3.7.4 Life aging. When tested in accordance with 4.8.4, the change in optical transmittance shall not
exceed the requirements of 3.6.1. When returned to ambient temperature, visual inspection in
accordance with 4.7.2 shall reveal no cracking or melting of the fiber coatings and the fiber coatings shall
meet the mechanical strippability requirements of 3.5.3.
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