60
IM AQ1210-02EN
Terminology
Near-end reflection
Reflection occurs at the gap in the connector connecting the instrument and optical fiber cable. In the section where this reflection is
detected, loss and reflections that occur at connections cannot be detected. This section is called a dead zone.
Backscatter
When light travels through an optical fiber cable, Rayleigh scattering occurs due to inconsistencies in the density and composition
of materials that are smaller than the unit of wavelength. The portion of the scattered light that travels in the direction opposite to the
direction of propagation is known as backscatter.
Splice loss
Splice loss occurs in spliced sections mainly due to the offset axis and angle.
Reflection caused by a connector
Using a connector to connect two optical fibers is different from splicing them together in that a small gap remains between the two
fibers. Because this gap has a different index of refraction, reflection and loss occur.
Fresnel reflection at the far-end of the optical fiber
When light is applied to an optical fiber cable, Fresnel reflection occurs at locations where the cable is broken and at locations where the
index of refraction changes such as at the end of the cable (the interface between glass and air). When the optical fiber cable end face
is vertical, approximately 3.4% of the incident optical power (–14.7 dB) is reflected.
Dynamic range
Dynamic range refers to the difference between the backscatter level at the near-end side and the noise (RMS = 1).
Dead zone
Dead zone refers to areas where measurement is not possible because of the influence from Fresnel reflection, connection points, or
the like.
Background Information on Measurements
