MIL-PRF-49291D
6.4 Definitions. Definitions of terms are in accordance with TIA-440.
6.4.1 Cladding ovality. The cladding ovality is the measure of the degree of roundness of the cladding.
It is expressed as the difference between the largest cladding diameter and the cladding diameter
measured at right angles to it, all divided by the average of the two values.
6.4.2 Core/cladding offset. The core/cladding offset is the distance between the central axis of the core
and the central axis of the cladding.
6.4.3 Core ovality. The core ovality is the measure of roundness of the core. It is expressed as the
difference between the largest core diameter and the core diameter measured at right angles to it, all
divided by the average of the two values.
6.4.4 Overall coating concentricity error. Overall coating concentricity error (previously called overall
coating concentricity ratio) is determined by measuring the minimum wall thickness (min) and the
maximum wall thickness (max) and dividing the minimum by the maximum value. This error is expressed
in microns.
6.4.5 Transient attenuation. Transient attenuation, in Type I fiber, is the increase (or decrease) in
attenuation from the steady-state attenuation because of the over (or under) excitation of the lossy high
order propagating modes compared with the steady-state distribution. The steady-state distribution is the
condition in which the relative power distribution among the propagating modes is independent of
longitudinal distance.
6.5 Environmentally preferable material. Environmentally preferable materials should be used to the
maximum extent possible to meet the requirements of this specification. As of the dating of this
document, the U.S. Environmentally Protection Agency (EPA) is focusing efforts on reducing 31 priority
chemicals. The list of chemicals is available on their website at
https://www.epa.gov/epaoswer/hazwaste/minimize/chemlist.htm. Further information is available at the
following EPA site: https://www.epa.gov/epaoswer /hazwaste/minimize/. Included in the EPA list of 31
priority chemicals are cadmium, lead, and mercury. Use of the materials on the list should be minimized
or eliminated unless needed to meet the requirements specified herein (see section 3).
6.6 Subject term (key word) listing.
Aperture, numerical
Attenuation, optical
Bandwidth, fiber
Coating material
Coating, fiber
Cladding
Core
Diameter, cladding
Diameter, core
Distortion, pulse
Fiber, optical
Fiber optics
Fiber, plastic clad silica
Graded index profile
Inclusion
Microbending
Microbend loss
Profile, index
Profile, refractive index
Refraction, index of
Volume, mode
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