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/* NeoScan Optical Bench Manager Program */
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[[Image:neoscanfig_3_7.png|thumb|center|600px|<i><b>Figure 3.7</b>: NeoScan Optical Bench Manager Program.</i>]]
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When the program starts, the system detects the total return power and the polarization power in the channel, plots their variations over time and displays their numerical values in mW. Figure 3.8 indicates that channel 1 is selected to deliver the beam to optical probe with Probe ID No. 1505. The Probe ID No. is a four-digit integer number provided by EMAG Technologies Inc. The green “Probe Detected” indicator indicates that the probe is connected to the correct channel.
<center>[[Image:neoscanfig_3_9neoscanfig_3_8.png|thumb|center|600px|<i><b>Figure 3.98</b>: Selecting The total return power and the working polarization power of delivered beam to the optical probe with Probe ID No. 1505 in channel from NeoScan Optical Bench Manager window1.</i>]]</center>
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Select the channel number you want to use for the measurement using the dropdown list labeled “Select Channel” (Figure 3.9). “Ch n” denotes channel n where n = 1, 2, … [[NeoScan]] Optical Bench Manager program opens up with the “Ch 1” as the default working channel.
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<center>[[Image:neoscanfig_3_9.png|thumb|center|600px|<i><b>Figure 3.9</b>: Selecting the working channel from NeoScan Optical Bench Manager window.</i>]]</center>
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If the polarization is maintained, the total return power and the polarization power will lie within the specified optimized range (the default value is ±20%). In this case, “Optimization Indicator LED” becomes green. Otherwise, it start blinking and the information panel indicates: “Polarization is not maintained: Optimization is required.” A user can change the threshold from the box labeled “Auto Trigger Margin” (see Figures 3.7 and 3.8). If the power difference is greater than 20%, the polarization state is found not to be maintained, therefore, the user will be prompted with a dialog window giving an opportunity to initiates the optimization process or skip the optimization by choosing “No.”
To set the optimization parameters, press “Optimization Settings” tab in [[NeoScan]] Optical Bench Manager program (Figure 3.11): Make sure the GPIB-USB cable from the back panel of Lock-in amplifier is connected to the [[NeoScan]] USB Hub.
<center>[[Image:neoscanfig_3_12.png|thumb|center|500px|<i><b>Figure 3. 12</b>: Lock-in Amplifier Settings in Optimization Settings Page.</i>]]</center>></li><li><p>If you change any value, press “Set Values” button to update.</p></li><li><p>Set Lock-in amplifier parameters:</p><ol type="a. "><li><p>Set Lock-in amplifier sensitivity. The sensitivity of Lock-in amplifier is the rms amplitude of an input sine (at the reference frequency) which results in a full scale DC output (10Vdc).</p></li><li><p>b. Select “Time Constant” from the dropdown lists. The default for time constant of the output low-pass filter that determines the bandwidth of Lock-in amplifier in 10 ms.</p></li></ol></li><li><p>4. Press “Set Values” button to update.</p></li>
Other parameters that should be directly set on SR844 RF Lock-in amplifier – since they are not controlled:
<ol><li> Time constant: 24 dB/oct, Figure 3.13(a). </li><li>
Signal Input: 50 Low noise, Figure 3.13(b).
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Sensitivity: Low noise, Figure 3.13(c).
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X display: R(dBm), Figure 3.13(d).
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Y display: θ, Figure 3.13(e).
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Remote: 50 external source, Figure 3.13(f).
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The signal levels at the Signal In port on the Lock-in amplifier are in the range of -100 dBm to -40 dBm or higher, depending on device one measures. It is important to set the sensitivity of the Lock-in amplifier greater than the expected input signal amplitude at the Signal Input port (from the IF Out of the optical mainframe). For example, if you expect a signal less than -67 dBm but greater than -87 dBm, set the sensitivity to -67 dBm and 100 μV (rms) setting. If the input signal is greater than the input signal setting, an OVERLOAD condition will occur and the red LED OVERLOAD indicators on the Lock-in amplifier will flash.
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Keep the default values for other parameters. Table 3.1 lists the default values for the main parameters used in the optimization process, see Figure 3.14.
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Optimization parameters are stored in C:\ProgramData\[[NeoScan]]\OptimizationParameters folder.
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