3-8
IM AQ1200-01EN
Distance Range
Specify a distance range that matches the cable length. The distance range that you can select
varies depending on the wavelength. Specify a distance range value that is greater than the length
of the optical fiber that you will measure. If you specify a shorter value, the Instrument will not
be able to perform measurements properly. The longer the distance that you specify, the more
time measurements will take. When you specify the distance range, the optimum pulse width and
attenuation values are set automatically.
Cable Length
Distance Range
Unknown
Automatic
0 m to 400 m
500 m
400 m to 800 m
1 km
800 m to 1.6 km
2 km
1.6 km to 4 km
5 km
4 km to 8 km
10 km
8 km to 16 km
20 km
16 km to 40 km
50 km
40 km to 80 km
100 km
80 km to 160 km
200 km
160 km to 240 km
300 km
240 km to 320 km
400 km
320 km to 410 km
512 km
Pulse Width
The pulse width has the following characteristics.
• A short pulse width enables you to measure with a high resolution, but you cannot measure long
distances.
• A long pulse width enables you to measure long distances, but you cannot measure with a high
resolution. Also, dead zones are larger with long pulse widths.
The pulse widths that you can select vary depending on the distance range, as shown in the following
table.
Distance Range
Selectable Pulse Widths
500 m
3 ns, 10 ns, 20 ns, 50 ns, 100 ns, 200 ns, 500 ns
1 km
3 ns, 10 ns, 20 ns, 50 ns, 100 ns, 200 ns, 500 ns, 1 μs
2 km
3 ns, 10 ns, 20 ns, 50 ns, 100 ns, 200 ns, 500 ns, 1 μs
5 km
3 ns, 10 ns, 20 ns, 50 ns, 100 ns, 200 ns, 500 ns, 1 μs
10 km or 20 km
3 ns, 10 ns, 20 ns, 50 ns, 100 ns, 200 ns, 500 ns, 1 μs
50 km or greater
3 ns, 10 ns, 20 ns, 50 ns, 100 ns, 200 ns, 500 ns, 1 μs, 2 μ, 5 μs, 10 μs, 20 μs
• When the distance range is set automatically, you cannot select the pulse width.
• When you specify the pulse width, the attenuation is automatically set to the optimum value.
Attenuation
If large reflections are caused by optical connectors or by breaks in the optical fiber, the waveform may
be saturated. Specify attenuation to prevent the waveform from being saturated.
The attenuations that you can select vary depending on the pulse width, as shown in the following
table.
Pulse Width
Selectable Attenuations
3 ns to 50 ns
0 dB, 2.50 dB, 5.00 dB, 7.50 dB, 10.00 dB, 12.50 dB, 15.00 dB
100 ns to 1 μs
0 dB, 2.50 dB, 5.00 dB, 7.50 dB, 10.00 dB, 12.50 dB, 15.00 dB, 17.50 dB, 20.00 dB
2 μs to 5 μs
0 dB, 2.50 dB, 5.00 dB, 7.50 dB, 10.00 dB, 12.50 dB, 15.00 dB, 17.50 dB, 20.00 dB,
22.50 dB, 25.00 dB
10 μs, 20 μs
0 dB, 2.50 dB, 5.00 dB, 7.50 dB, 10.00 dB, 12.50 dB, 15.00 dB, 17.50 dB, 20.00 dB,
22.50 dB, 25.00 dB, 27.50 dB, 30.00 dB
• If the distance range or pulse width is set automatically, or if the average method is set to high
reflection, you cannot select the attenuation.
• If the waveform is saturated, you cannot perform measurements with high sensitivity, so specify a
large value.
3.5 Setting Measurement Conditions
