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IM AQ7280-01EN
1.4 Optical Pulse Analysis
Waveform Analysis
You can use cursors and markers to measure values such as the distance, splice loss, and return loss
between two points.
Measuring Distance
The AQ 7280 measures the time that it takes for an incident optical pulse to be reflected and return to
the device. It uses this information and the following equation to calculate the distance (L).
L=C×T/(2N) [m]
C : The speed of light in a vacuum 2.99792×10
8
[m/s]
T : The time measured from when the incident optical pulse was generated to when the
reflected light was received [s]
N : Index of refraction
In the above equation, the division by two accounts for the fact that the measured time represents the
total time taken by the optical pulse to reach the reflection point and to return from it.
If the correct index of refraction is not specified, there will be errors in the distance measurement.
Setting the Index of Refraction
The AQ7280 has preset indices of refraction that correspond to each wavelength. For details on the
settings, see section 4.1. Contact the optical fiber manufacturer for the optical fiber cable’s correct
index of refraction.
Distance Range
You must select a distance range that is longer than the cable length of the optical fiber cable that
you want to measure. As the distance becomes greater, the measurement time also increases. For
details on the setting range, see section 2.1.
Pulse Width
The following features are available depending on the length of the pulse width. The pulse width
that you can select varies depending on the distance range that you have specified. For details on
the settings, see section 2.1.
• Short Pulse Width
You can separate and measure adjacent events (reflection points and losses). However, you
cannot measure long distances.
• Long Pulse Width
You can measure long distances. However, multiple adjacent events may be seen as one single
event.
Pulse width
