8 • Operation
Calibration Data (Model 2103 Only)
To correct for wavelength response of the photodiode,
calibration information is provided on a sheet of paper
found in the back of the manual. These are the offsets
(in volts) which must be subtracted from measured
values in order for a 0-dBm input to produce 0 V at the
output. Input optical power is then given by
P(dBm) = 20 x (Vmeas – Vcal)
Warm-up Time
Active temperature stabilization of the photodiode
and critical circuit components requires a warm-up
time of about five minutes for full accuracy. Within
this period, the status light (for Model 2103) changes
from red to green and the output varies by several dB
as the temperature stabilizes. Failure of the status light
to turn green indicates the ambient temperature is
outside the operating range, and Model 2103 may not
give accurate readings. Model 2101 has no status light.
Output Signal
The output of the Models 2101 and 2103 is an analog
voltage with a gain of 50 mV per dB of input light. For
Model 2101, a 3.5-V output corresponds to
approximately 2 dBm of input power at 920 nm; the
accuracy degrades for signals outside the specified
range of 0.4 V to 3.7 V (-60 dBm to +6 dBm). For the
Model 2103, a 3.5-V output corresponds to
approximately 0 dBm of input power at 1550 nm.
While the output range is about -0.2 V to 3.75 V
(-74 dBm to +5 dBm), accuracy degrades for signals
outside the specified range of 0.4 V to 3.7 V (-62 dBm
to +4 dBm). The unit must be connected to a high-
impedance load; it cannot drive a 50-ohm load.
