4-6
IM AQ6376-01EN
Measurement Sensitivity and Vertical Axis Effective Range
When the measurement sensitivity is set to NORMAL HOLD, the internal amplifier has
a fixed gain. Five different gains are set automatically according to the reference (REF)
level setting. However, the effective range of measurement data is limited to the following
range, using the reference (REF) level (dBm) as a reference.
REF-20 dBm < (effective range) < REF+10 dBm
If the level scale is set to 10 dB/DIV, the display would exceed the effective range, so the
areas at 10 dB from the screen stop and 20 dB from the bottom are inaccurate.
When measurement sensitivity is set to NORMAL HOLD, we recommend setting the
level scale to 5 dB/DIV or less.
Under the measurement sensitivity settings NORMAL AUTO, MID, and HIGH 1–3, an
automatic gain is used, permitting measurements over a wide level range through a
single sweep. Select the appropriate sensitivity level based on the light reception level
required for the particular measurement application.
LIN SCALE
This key is used to set the main scale to linear scale.
Settings per 1 DIV are set in the reference level.
LIN BASE LEVEL **.*mW
Value when the vertical axis is linear scale, you can set the level scale low-end. This is
not available when using a log scale.
The setting range is 0.0 to REF level x 0.9. Settings can be adjusted in steps of 0.1. The
value changes in steps of 1 if you press the COARSE key. Values can only be set in the
instrument set for the REF level.
When the setting is changed, the displayed waveform is redrawn according to the
changed scale.
The scale display in the upper left part of the waveform is 1/10 the value (*W/D) of the
reference (REF) level minus the low-end (BASE) level.
For information on the REF level setting, see section 4.4, "Setting the Reference Level."
LEVEL UNIT dBm dBm/nm
When the vertical axis is log scale, the display toggles between dBm and dBm/nm.
dBm: Power per resolution (absolute power)
dBm/nm: Power per 1 nm (power spectral density)
For information on the use of dBm and dBm/nm, see “Power spectral density Display” in
section 1.2, “Measurement.”
This soft key is disabled if the unit of the horizontal axis is wavenumber.
LEVEL UNIT mW mW/nm
When the level axis uses a linear scale, the display switches between nW, μW, mW, or
pW (absolute power), and nW/nm, μW/nm, mW/nm or pW/nm (power spectral density).
4.2 Horizontal/Vertical Axis Settings