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ice:servo-opls [2016/07/22 16:43] – Michael Radunsky | ice:servo-opls [2016/07/22 18:07] – [Calculating Phase Noise] Michael Radunsky |
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=====Understanding the Transfer Function===== | =====Understanding the Transfer Function===== |
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<imgcaption xfer_func center|Schematic of the OPLS right-side panel,showing the configurable transfer function and its user-controls.>{{ :ice:opls-loopfilter-xfer-function.jpg?nolink&700 |}}</imgcaption> | <imgcaption xferfunc|Schematic of the OPLS right-side panel, showing the configurable transfer function and its user-controls.>{{ :ice:opls-loopfilter-xfer-function.jpg?nolink&700 |}}</imgcaption> |
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The charge pump in the OPLS outputs a signal proportional to the phase-error and the transfer function is as shown in <imgref xfer_func >. However, the OPLS will typically be used to control a //frequency//-tunable device (such as a laser). In this configuration, the effective loop filter is not the one shown in <imgref opls_side_panel>, but includes a extra integration corresponding to converting the phase-error input to a frequency error. Thus, ω<sub>I </sub>sets the frequency transition from single-integration to double-integration and ω<sub>I </sub> from single-integration to proportional feedback. It is important to understand this 'hidden' integrator when configuring the loop filter parameters. | The charge pump in the OPLS outputs a signal proportional to the phase-error and the transfer function is as shown in <imgref xferfunc>. However, the OPLS will typically be used to control a //frequency//-tunable device (such as a laser). In this configuration, the effective loop filter is not the one shown in <imgref opls_side_panel>, but includes a extra integration corresponding to converting the phase-error input to a frequency error. Thus, ω<sub>I </sub>sets the frequency transition from single-integration to double-integration and ω<sub>I </sub> from single-integration to proportional feedback. It is important to understand this 'hidden' integrator when configuring the loop filter parameters. |
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=====Calculating Phase Noise ===== | =====Calculating Phase Noise ===== |
<WRAP center round box 450px><html><center></html> **D2-135 Phase-Noise Floor = -213 + 20Log(N) + 10Log(F<sub>REF</sub>)**<html></center></html></WRAP> | <WRAP center round box 450px><html><center></html> **D2-135 Phase-Noise Floor = -213 + 20Log(N) + 10Log(F<sub>REF</sub>)**<html></center></html></WRAP> |
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where N is the value of the divider and F<sub>REF</sub> is the reference frequency as measured in Hz. For more details, please see [[http://www.vescent.com/2012/calculating-phase-noise-from-the-d2-135/|http://www.vescent.com/2012/calculating-phase-noise-from-the-d2-135/]] . | where N is the value of the divider and F<sub>REF</sub> is the reference frequency as measured in Hz. For more details, please see this [[http://www.vescent.com/2012/calculating-phase-noise-from-the-d2-135/|application note]]. |
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</WRAP> | </WRAP> |
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**Beat Note Input ** | **Beat Note Monitor ** |
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| The Front Panel for the ICE-CP1 has four SMA or FC connectors. The second bottom-most connector is an SMA which is the digitized (i.e. square-wave) version of the input beat-note after a divide-by-2. For example, if the input beat note is 6 GHz, the monitor will have a 3 GHz output. The signal is ~0 dBm in power regardless of the strength of the input beat-note signal. |
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The Front Panel for the ICE-CP1 has four SMA or FC connectors. The top connector (SMA for ICE-CP1-SMA, FC for ICE-CP1-FC) is the beat note signal input. When FC, this input should be a <1 mW signal containing overlapped light from both lasers. When an SMA, this input should be an electrical signal, typically the output of the D2-160. | |
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**External Reference Frequency Input ** | **External Reference Frequency Input ** |
The Front Panel for the ICE-CP1 has four SMA or FC connectors. The second top-most connector is an SMA input for the external frequency reference. The input is AC coupled and 50 Ω terminated. Max power is 10 dBm. | The Front Panel for the ICE-CP1 has four SMA or FC connectors. The second top-most connector is an SMA input for the external frequency reference. The input is AC coupled and 50 Ω terminated. Max power is 10 dBm. |
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**Beat Note Monitor ** | **Beat Note Input ** |
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The Front Panel for the ICE-CP1 has four SMA or FC connectors. The second bottom-most connector is an SMA which is the digitized (i.e. square-wave) version of the input beat-note after a divide-by-2. For example, if the input beat note is 6 GHz, the monitor will have a 3 GHz output. The signal is ~0 dBm in power regardless of the strength of the input beat-note signal. | |
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| The Front Panel for the ICE-CP1 has four SMA or FC connectors. The top connector (SMA for ICE-CP1-SMA, FC for ICE-CP1-FC) is the beat note signal input. When FC, this input should be a <1 mW signal containing overlapped light from both lasers. When an SMA, this input should be an electrical signal, typically the output of the D2-160. |
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**Laser Current ** | **Laser Current ** |