PSY-201 User Guide
GP-UM-PSY-201-11
Page 81 of 105
Note that the sampling rate is not necessarily the same as the data capture rate. The data
capture rate is the rate at which SOPs are written to a file or displayed on-screen. Since, under
some circumstances, not every sampled point is recorded,
Data capture rate
≤
SOP sampling rate.
In sphere mode, the data capture rate is dynamic. It can vary between the base rate of
100 points/s and the SOP sampling rate, depending on the SOP variation rate and the trace
sensitivity setting.
In oscilloscope mode, the data capture rate is equal to the SOP sampling rate.
Detector Integration Time:
The integration time can be set for either automatic or manual control. In automatic
control, the integration time is dynamic, with its value determined by the gain, which can change
with input power level.
Gain
3dB bandwidth
Average samples
Integration time
0-5 1MHz
4 1µs
6,7,8 600kHz
8
2µs
9,10,11 100kHz 40
10µs
12-18 10kHz 400 100µs
In manual control mode, the user can set a fixed integration time between 0.25µs and 180
s. The minimum integration time is 0.25
μ
s, which corresponds to the highest sampling bandwidth
of the instrument (4M SOP samples/second). If manual control is used, the value should be
chosen such that
integration time
≤
1/ sampling rate
DOP Average Number:
The number of SOP samples averaged to calculate the DOP. This setting can be used to
characterize polarization scrambler performance, for example.
Trace Sensitivity (Sphere mode only):
The SOP change threshold level that triggers capture of a new data point for the sphere
display or “stream to file” functions. Effectively, it is the minimum resolution for the recorded
data.
In sphere mode, the data capture rate is dynamic; it depends on both the trace sensitivity
setting and the rate of change of the input SOP. The baseline data capture rate is 100 points/s. If
ε
is the trace sensitivity, as long as the input SOP does not change at a rate faster than 100
ε
/s,
data is captured at the baseline rate. As the rate of change of input SOP increases, the data
capture rate varies dynamically such that there is a separation of no more than
ε
between
consecutive collected SOPs, up to an upper limit of the SOP sampling rate setting (see Figure 33).
