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NeoScan Manual Part B: Measurement Preparations

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/* NeoScan Optimization Utility Program */

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ï¾ Remote: 50 ~~Ω~~ Î© external source, Figure 3.13(f).

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[[Image:neoscanfig_3_13.png|thumb|center|600px|Figure 3.13: Stanford Research Systems SR844 RF Lock-In Amplifier: (a) Time constant: 24 dB/oct, (b) Signal Input: 50 Î© Low noise, (c) Sensitivity: Low noise, (d) X display: R(dBm), e) Y display: Î¸, (f) Remote: 50 Î© external source.]]

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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 Î¼V (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.

Optimization parameters are stored in C:\ProgramData\[[NeoScan]]\OptimizationParameters folder.

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|+ Table 3.1: Default values for the main parameters used in the optimization process.

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Â [[Image:neoscanfig_3_14.png|thumb|center|600px|Figure 3.14</pb> ~~â~~: Optimization parameters settings in Optimization Settings Page.]]<p/center>Â

If the optical signal is low, check to make sure:

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==== 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>Move the probe around the CPW slot using the X or Y Miniature Translation Stages. </li><li>2. Position the probe right above the CPW slot.</li><li>Using the Z Miniature Translation Stage and lower the probe down close to the surface of CPW as much as possible.</li></ol>

~~3. Using the Z Miniature Translation Stage and lower the probe down close to the surface of CPW as much as possible.~~==== [[NeoScan]] Optimization Utility Program ====

[[Image:neoscanfig_3_15.png|thumb|right|300px|Figure 3.15: Dialog window for initiating the optimization process.]] In order to initiate an optimization, it is assumed:

<ul><li>~~3.3.2 [[NeoScan]] Optimization Utility Program~~Â Â ~~In order to initiate an optimization, it is assumed:~~ ~~â¢~~ The channel number and the Probe ID No. of the probe you want to optimize are selected.</li><li>~~â¢~~ 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).</li><li>~~â¢~~ Press âApplyâ button to start new probe optimization (Figure 3.7).</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.

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.

Â <center>[[Image:neoscanfig_3_16.png|thumb|center|600px|Figure 3.16: NeoScan Optimization Utility program.]] [[Image:neoscanfig_3_17.png|thumb|center|600px|Figure 3.17: 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)]]</center>Â 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>When you attach the fiber connectors to the fiber ports of the [[NeoScan]] front panel,</li><li>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.</li><li>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%).</li><li>When there is an abrupt and sharp change in temperature.</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.~~Â ~~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%).~~Â ~~iv. When there is an abrupt and sharp change in temperature.~~<ul><li>~~â¢~~ 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. </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.

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