<ol>
<li>
<p>
Gently unwind the fiber and deploy the sensor head(s) at measurement location or on the probe fixture.
</p>
</p>
</li>
</ol>â
=== [[NeoScan]] Optical Bench Manager Program ===
<center>
[[Image:neoscanfig_3_7.png|thumb|center|600px|<i><b>Figure 3.7</b>: NeoScan Optical Bench Manager Program.</i>]]
<br>
[[Image:neoscanfig_3_8.png|thumb|center|600px|<i><b>Figure 3.8</b>: The total return power and the polarization power of delivered beam to the optical probe with Probe ID No. 1505 in channel 1.</i>]]
</center>
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 âProbe Detectedâ 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>
<ol>
<li>
<p>
Select the channel number you want to use for the measurement using the dropdown list labeled âSelect Channelâ (Figure 3.9). âCh nâ denotes channel n where n = 1, 2, ⦠... [[NeoScan]] Optical Bench Manager program opens up with the âCh 1â as the default working channel.
</p>
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<center>[[Image:neoscanfig_3_9.png|thumb|center|650px|<i><b>Figure 3.9</b>: Selecting the working channel from NeoScan Optical Bench Manager window.</i>]]</center>
</li>
<li>
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, âOptimization Indicator LEDâ becomes green. Otherwise, it start blinking and the information panel indicates: âPolarization is not maintained: Optimization is required.â A user can change the threshold from the box labeled âAuto Trigger Marginâ (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 âNo.â
â
â<p>The âStopâ button stops the application. To close (kill) the [[NeoScan]] window click on exit button [[Image:icon_Exit.png]] on the top far right in the LabView user interface. To re-start running the program press the start button [[Image:icon_Start.png]] located on the top left in the LabView window as shown in Figure 3.10. During the run, the start button will disappear. Keep [[NeoScan]] Optical Bench Manager program running until the end of the measurement. </p>
The âStopâ button stops the application. To close (kill) the <center>[[NeoScan]] window click on exit button on the top far right in the LabView user interfaceImage:neoscanfig_3_10. To re-start running the program press the start button located on the top left in the LabView window as shown in png|thumb|center|600px|<i><b>Figure 3.10. During the run, the start button will disappear. Keep [[</b>: Start and Stop buttons for NeoScan]] Optical Bench Manager program running until the end of the measurement. </i>]]</center>
⢠<ul><li><p>The message box in âInformation Panelâ displays messages of warnings, actions and results.⢠</p></li><li><p>âSave Plotsâ saves in folder C:\ProgramData\[[NeoScan]]\OpticalBenchHistory.⢠</p></li><li><p>A user can reset the graphs by pressing âReset Plotsâ button. The updated start time will be displayed under the power graph after âStarted atâ and in the information panel. ⢠</p></li><li><p>There are two options to display power plots: The âEntire Historyâ option displays the power plots from the time Optical Bench Manager program started (numerically is displayed as Start Project Time in information panel). The âUpdatedâ option displays the power plots after resetting the plots (pressing âReset Plotsâ button), see Figure 3.11. </p> <center>[[Image:neoscanfig_3_11.png|thumb|center|600px|<i><b>Figure 3.10</b>: Resetting the power plots and displaying them with the Entire History and Updated options.</i>]]</center></li></ul>
â
3.2.2 ==== Optimization Settings Page====
To set the optimization parameters, press âOptimization Settingsâ 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.
1<center>[[Image:neoscanfig_3_11b. Set Lock-in amplifier from âLock-in Amplifier Settingsâ section (png|thumb|center|600px|<i><b>Figure 3.12). Put down the Visa menu and select the appropriate GPIB address for Lock-11</b>: Optimization Settings page in amplifier Visa. The default is GPIB0::8::INSTNeoScan Optical Bench Manager program.</i>]]</center>
2<ol><li><p>Set Lock-in amplifier from âLock-in Amplifier Settingsâ section (Figure 3. If you change any value, press âSet Valuesâ button to update12).Put down the Visa menu and select the appropriate GPIB address for Lock-in amplifier Visa. The default is GPIB0::8::INST.</p>
<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 âSet Valuesâ 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 âTime Constantâ 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 âSet Valuesâ button to update.</p></li>
Other parameters that should be directly set on SR844 RF Lock-in amplifier â since they are not controlled:
<ul><li>ï¾ Time constant: 24 dB/oct, Figure 3.13(a). </li><li>
ï¾ Signal Input: 50 ï Low noise, Figure 3.13(b).
</li>
<li>
ï¾ Sensitivity: Low noise, Figure 3.13(c).
</li>
<li>
ï¾ X display: R(dBm), Figure 3.13(d).
</li>
<li>
ï¾ Y display: θ, Figure 3.13(e).
</li><li>ï¾ Remote: 50 ï Ω external source, Figure 3.13(f).</li></ul> <center>[[Image:neoscanfig_3_13.png|thumb|center|600px|<i><b>Figure 3.13</b>: Stanford Research Systems SR844 RF Lock-In Amplifier: (a) Time constant: 24 dB/oct, (b) Signal Input: 50 Ω Low noise, (c) Sensitivity: Low noise, (d) X display: R(dBm), e) Y display: θ, (f) Remote: 50 Ω external source.</i>]]</center>Â
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.
⢠<ul><li><p>If the largest tolerable noise signal (at the input) exceeds the full scale signal, the red LED OVLD indicators in lock-in indicate that the readings may be invalid due to an overload condition. In this situation, you many try increasing the time constant or to use a larger full scale sensitivity.</p></li></ul>
5. </li><li><p>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.</p></li><li><p>Optimization parameters are stored in C:\ProgramData\[[NeoScan]]\OptimizationParameters folder. </p></li></ol><center><div class="noprint" style="float:center;margin-right:10px">{| border="1" class="wikitable"|+ <i><b>Table 3.1</b>: Default values for the main parameters used in the optimization process.</i>|-! <b>Parameter</b>| <b>Description</b>| <b>Default Value</b>|-! Lock-in Amplifier Visa| Lock-in Amplifier GPIB address| GPIB0::8::INSTR|-! Sensitivity| Lock-in Amplifier Sensitivity| 100 uV / -67 dBm|-! Time Constant| Lock-in Amplifier Time Constant| 10 ms|-! No. Averaging Points| Number of points used to find the peak value| 5|-! Variation Limit| Maximum variation from the nominal value| 1.00 dBm|-! PC Voltage| Maximum voltage applied to the polarization controllers during the optimization process.| 3.0 V|-! Voltage Steps| Voltage steps applied to the polarization controllers during the optimization process| 0.01 V|-! Wait Time| Interval delay time| 1000 ms|}</div>
6[[Image:neoscanfig_3_14. png|thumb|center|600px|<i><b>Figure 3.14</b>: Optimization parameters are stored settings in C:\ProgramData\[[NeoScanOptimization Settings Page.</i>]]\OptimizationParameters folder. </center>
If the optical signal is low, check to make sure:
<ul>
<li>
<p>
The probe and the crystal on its tip is fine.
</p>
</li>
<li>
<p>
The operating frequency is correct.
</p>
</li>
<li>
<p>
All the components are connected correctly and appropriately.
</p>
</li>
<li>
<p>
All instruments are functioning properly.
</p>
</li>
<li>
<p>
All cables and the PM fiber are fine.
</p>
</li>
<li>
<p>
All connectors are in good conditions â make sure they are not loose.
</p>
</li>
<li>
<p>
CPW is functioning properly.
</p>
</li>
<li>
<p>
Lower the probe down close to the surface of CPW and make sure the probe positions right above the CPW slot and move it around the slot.
</p>
</li>
</ul>
=== Probe Optimization ===
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Parameter Description Default Value
Lock-in Amplifier Visa Lock-in Amplifier GPIB address GPIB0::8::INSTR
Sensitivity Lock-in Amplifier Sensitivity 100 uV / -67 dBm
Time Constant Lock-in Amplifier Time Constant 10 ms
No. Averaging Points Number of points used to find the peak value 5
Variation Limit Maximum variation from the nominal value 1.00 dBm
PC Voltage Maximum voltage applied to the polarization controllers during the optimization process. 3.0 V
Voltage Steps Voltage steps applied to the polarization controllers during the optimization process 0.01 V
Wait Time Interval delay time 1000 ms
Table 3.1: Default values for the main parameters used in the optimization process.
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If the optical signal is low, check to make sure:
⢠The probe and the crystal on its tip is fine.
⢠The operating frequency is correct.
⢠All the components are connected correctly and appropriately.
⢠All instruments are functioning properly.
⢠All cables and the PM fiber are fine.
⢠All connectors are in good conditions â make sure they are not loose.
⢠CPW is functioning properly.
⢠Lower the probe down close to the surface of CPW and make sure the probe positions right above the CPW slot and move it around the slot.
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3.3 Probe Optimization
The [[NeoScan]] software monitors and controls the polarization of the optical beam in the system. The optimization status for each probe at each channel needs be maintained for an extended period of time. Not only an initial optimization process for each probe at each channel is needed, but also additional optimization processes are needed if the status is not maintained. In general, you have to perform optimization whenever you detach the fiber connectors from the fiber ports of the [[NeoScan]] system or when the fluctuation in the total return optical power and the polarization power are varied more than 20%. After the optimization procedure, the system is ready for real-time measurement or scan.
3.3.1 ==== Optimization Setup and Procedure ====Â
It is assumed that [[NeoScan]] optical mainframe is already on. The setup for the optimization procedure is similar to Signal Strength Check setup as described in section 3.1.2.
To get the maximum EO signal:
1. <ol><li><p>Move the probe around the CPW slot using the X or Y Miniature Translation Stages. </p></li><li><p>2. Position the probe right above the CPW slot.</p></li><li><p>3. Using the Z Miniature Translation Stage and lower the probe down close to the surface of CPW as much as possible.</p></li></ol>
==== [[NeoScan]] Optimization Utility Program ====
[[Image:neoscanfig_3_15.png|thumb|right|300px|<i><b>Figure 3.15</b>: Dialog window for initiating the optimization process.</i>]] In order to initiate an optimization, it is assumed:
<ul>3.3.2 [[NeoScan]] Optimization Utility Program  In order to initiate an optimization, it is assumed: <li><p>⢠The channel number and the Probe ID No. of the probe you want to optimize are selected.</p></li><li><p>⢠The steps described in section 3.2.2 in âOptimization Settings Pageâ have been done (GPIB address of the Lock-in Amplifier, Time Constant, and the Sensitivity, have been already chosen).</p></li><li><p>⢠Press âApplyâ button to start new probe optimization (Figure 3.7).</p></li></ul>
A user is presented with a dialog window shown in Figure 3.15, giving an option to initiates the optimization process â which will take about 20 minutes to be completed â or skip the optimization by choosing âNo.â Click on âYesâ for optimization. The system will remind a user to prepare an optimization structure. Align crystal field sensitivity direction to optimization structure field properly and press âContinueâ.
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When the optimization process starts, [[NeoScan]] Optimization Utility window will pop up, and the detailed optimization parameters are displayed to a user (Figure 3.16): Table 3.1 lists the main parameters used in optimization process with their default values.
The change of the return power and the EO signal are plotted during the optimization process as shown in Figure 3.17, and their values are displayed in the boxes labeled âPD Powerâ and âEO Signalâ, respectively. a user can monitor âPolarization Controller Parametersâ through the information panel shown in Figure 3.18.
 <center>[[Image:neoscanfig_3_16.png|thumb|center|600px|<i><b>Figure 3.16</b>: NeoScan Optimization Utility program.</i>]]<br>[[Image:neoscanfig_3_17.png|thumb|center|600px|<i><b>Figure 3.17</b>: Change of the return power and the electro-optic signal graphs during the optimization process (left to right direction indicates the start to the end of the process)</i>]]</center> The optimization process takes about 20 minutes. It can be used to diagnose hardware failures. When the phase optimization has completed, the optimization window will prompt a user to perform a probe stability test through a red blinking âStart Stability Testâ button at the bottom of the Window (Figure 3.19). To perform the probe fiber stability test, press the âStart Stability Testâ button shown in Figure 3.19. An information dialog box will pop up and explains the procedure for the test. Press âCloseâ button in dialog box and then lift the middle of the fiber at least 2 m from either the probe head or the optical connector. Move it up and down, and/or left and right several times. The program will record variations in return power on the screen. Be sure not to pull the fiber at the connector or the probe ends. After performing this for approximately 30 seconds, press âEnd Stability Testâ on the window. If signal fluctuations during the motion remains within the variation limit (default value is 1 dBm), the optimization is considered to be valid, otherwise, the program will repeat optimization (see Figure 3.20).
At the completion of the signal optimization process, the optimization window will disappear and the display will return to [[NeoScan]] Optical Bench Manager window. The optimized parameters will be written in files in ProgramData\NeoSca\OptimizationParameters.
You have to perform an optimization:
<ol type="i. "><li><p>When you attach the fiber connectors to the fiber ports of the [[NeoScan]] front panel,</p></li><li><p>Whenever you detach a fiber connector from to the fiber ports of the [[NeoScan]] front panel and re-attach it to the same or the any other port.</p></li><li><p>When the fluctuation in the total return optical power or the polarization power are varied more than the defined threshold value (default value is 20%).</p></li><li><p>When there is an abrupt and sharp change in temperature.</p></li></ol>
ii. Whenever you detach a fiber connector from to the fiber ports of the [[NeoScan]] front panel and re-attach it to the same or the any other port. iii. When the fluctuation in the total return optical power or the polarization power are varied more than the defined threshold value (default value is 20%). iv. When there is an abrupt and sharp change in temperature.<ul><li><p>⢠If the Probe ID No. is not correct, [[NeoScan]] Optical Bench Manager cannot find the files for optimization parameters, therefore, a user will be prompted with a warning dialog window shown in Figure 3.21. </p></li></ul>
When the voltages to the polarization controllers for a channel are set to the correct optimized values, you âmayâ observe a sharp change in the polarization power as shown in Figure 3.22. You can save the power plots by pressing âSave Figuresâ button.
<center>[[Image:neoscanfig_3_18.png|thumb|center|600px|<i><b>Figure 3.18</b>: Information Panel in NeoScan Optimization Utility program.</i>]]<br> [[Image:neoscanfig_3_19. png|thumb|center|600px|<i><b>Figure 3.19</b>: Stability Test in NeoScan Optimization Utility.</i>]]<br>[[Image:neoscanfig_3_20.png|thumb|center|600px|<i><b>Figure 3.20</b>: Comparison of a completed optimization process with a failed one in NeoScan Optimization Utility program.</i>]]â    <br>[[Image:neoscanfig_3_21.png|thumb|center|300px|<i><b>Figure 3.21</b>: Warning dialog window when the files for optimization parameters are not found.</i>]]<br>[[Image:neoscanfig_3_22.png|thumb|center|600px|<i><b>Figure 3.22</b>: The change in the polarization power after applying the optimization voltages to the polarization controllers.</i>]]â</center>