d2:offset_phase_lock_servo
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d2:offset_phase_lock_servo [2020/03/06 01:51] – [Right Side Panel] Michael Radunsky | — | ||
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- | <WRAP right round box 260px> | ||
- | [{{ d2: | ||
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- | ======Offset Phase Lock Servo ====== | ||
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- | Model No. D2-135-SMA / D2-135-FC | ||
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- | Document Revision: 2 | ||
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- | Document Last Updated on ~~LASTMOD~~ | ||
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- | Please read [[: | ||
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- | [[d2: | ||
- | [[https:// | ||
- | =====Description===== | ||
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- | The D2-135 Offset Phase Lock Servo (OPLS) locks the frequency and phase of the input beat-note to a (multiple of the) reference frequency. The beat-note is typically generated by overlapping two lasers (a master laser and a slave laser), whose interference forms a beat-note, which is a measurement of the frequency difference (or offset) between the two lasers. The beat-note is either input as an electrical signal via an SMA electrical connector (D2-135-SMA) or as an optical signal via a fiber (D2-135-FC; obsolete). | ||
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- | The beat-note input to the OPLS can be divided by //N// = 8, 16, 32, or 64 -- as set by the user -- before its frequency and phase is compared to the reference frequency. | ||
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- | **'' | ||
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- | By adjusting either the reference frequency or N, the frequency difference between the lasers can be precisely adjusted. The offset frequency is adjustable from 250 MHz to ≥9.5 GHz. | ||
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- | < | ||
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- | A schematic of the OPLS, along with the [[d2: | ||
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- | The loop filter has user-adjustable proportional-integral-differential (PID) feedback and an additional high-frequency roll-off frequency. Tuning the values of the PID loop filter allows the user to optimize the feedback to the laser for best offset locks. This is further discussed below. | ||
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- | The OPLS can be controlled via the front-panel, | ||
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- | The D2-150 Heterodyne Module is designed for use the with D2-160 Beat Note Detector and D2-135-SMA or just the D2-135-FC (obsolete). | ||
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- | =====Purchase Includes===== | ||
- | * D2-135 Offset Phase Lock Servo | ||
- | * VPN00465 BNC cable (1ft) | ||
- | * VPN00TBD SMA cable (1ft) | ||
- | * VPN00457 Trimpot tweaker (large) | ||
- | * VPN00458 Trimpot tweaker (small) | ||
- | * VPN00456 DB9 Power Cable (1ft) | ||
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- | =====Options===== | ||
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- | The D2-135 comes in two different versions: | ||
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- | *// | ||
- | *// | ||
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- | The D2-135-SMA requires an electrical signal input between 10 and -10 dBm of power. | ||
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- | The D2-135-FC-800 is no longer available, but information regarding it is retained for those users who have purchased this model. | ||
- | ===== Absolute Maximum Ratings ===== | ||
- | Note: All modules designed to be operated in laboratory environment | ||
- | <WRAP center round box 60%> | ||
- | | **Parameter** | **Rating** | | ||
- | |Environmental Temperature | >15°C and <30°C| | ||
- | |Environmental Humidity | <60% | | ||
- | |Environmental Dew Points | <15°C | | ||
- | </ | ||
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- | =====Specifications===== | ||
- | <WRAP center round box 550px> | ||
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- | | **Min Offset Frequency**(( Low frequency beat-notes are in principle possible with the D2-135-SMA provided the low-frequency beat-note is a square-wave and not sine-wave input and that the loop bandwidth ~10 times lower than your reference frequency. | ||
- | | **Max Offset Frequency** | ||
- | | **VCO drift** | ||
- | | **PFD Noise**(( See [[# | ||
- | | **ƒ**< | ||
- | | **ƒ**< | ||
- | | **ƒ**< | ||
- | | **Servo Output Range** | ||
- | | **Electronics Input / Output Impedance** | ||
- | | **User Adjustable Gain**(( Not including internal gain compensation for N divider. See [[# | ||
- | | **Max Electronic Beat-Note Input \\ (D2-135-SMA)** | ||
- | | **Min Electronic Beat-Note Input \\ (D2-135-SMA)** | ||
- | | **Min Electronic Beat-Note S/N \\ (D2-135-SMA)** | ||
- | | **Max Optical Beat-Note Input \\ (D2-135-FC; obsolete)** | ||
- | | **Min Optical Beat-Note Input \\ (D2-135-FC; obsolete)**((Approximate value as exact value depends on wavelength of the light and spatial overlap between the lasers.)) | ||
- | | **Front-panel Input Connection\\ (D2-135-FC; obsolete)((D2-135-FC was shipped with an FC to SC multimode patch cord))** | ||
- | | **Front-panel Input Connection\\ (D2-135-SMA)** | ||
- | | **External Reference Input Range** | ||
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- | </ | ||
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- | =====Modes===== | ||
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- | The OPLS operates in 12 different modes, controlled by the front-panel knob or with external inputs to the back-panel. These 12 modes select the value of the divide-by-N (N=8, 16, 32, or 64) and select between three states for the reference frequency (external input, internal VCO High, internal VCO Low). The table below shows the offset frequency ranges for these 12 different modes. | ||
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- | <WRAP center round box 70%> | ||
- | < | ||
- | ^ ^^ Divide-by-N settings | ||
- | ^ ^^ N=8 ^ N=16 ^ N=32 ^ N=64 ^ | ||
- | ^ Reference \\ Frequency \\ Setting | ||
- | ^::: | ||
- | ^::: | ||
- | ^::: | ||
- | </ | ||
- | </ | ||
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- | =====Inputs, | ||
- | < | ||
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- | ====Monitor Section==== | ||
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- | Located at the top of the front panel, the monitor section contains 6 BNC outputs for monitoring various signals used by the OPLS. | ||
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- | ===Error Signal (DC)=== | ||
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- | This is a heavily filtered monitor of the charge pump (CP) output. When the laser is phase-locked, | ||
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- | ===Error Signal (AC)=== | ||
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- | This is an unfiltered version of Error Signal (DC) that is four times smaller, and has a DC offset. | ||
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- | ===Ref Freq=== | ||
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- | REF FREQ provides an AC coupled, buffered monitor of the reference frequency going into the PFD. Signal should be terminated with 50Ω. | ||
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- | ===Servo Out=== | ||
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- | The SERVO OUT monitors the output signal that is fed back to the laser. | ||
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- | ===Ramp=== | ||
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- | RAMP is a monitor for the ramp signal sent to the SERVO OUTPUT when the laser is in RAMP mode. | ||
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- | ===Ramp TTL=== | ||
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- | The RAMP TTL is a trigger synchronous with the ramp. Typically it is used to trigger an oscilloscope while sweeping the SERVO OUTPUT. The RAMP TTL signal is also available on the back panel as a dedicated trigger output. | ||
- | ====Front Panel==== | ||
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- | **Power (LED indicator)** | ||
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- | All electronic modules have a blue LED power indicator on the top right side of the front panel control section. | ||
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- | **Offset Mode Selector** | ||
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- | This 12 position rotary switch selects the value of N (N=8,16,32, or 64) and the reference oscilator mode (External, VCO Low, VCO High). The mode selected can be overridden with the computer control. | ||
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- | **VCO Tune (10-turn potentiometer)** | ||
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- | <WRAP center round alert 60%> | ||
- | Internal VCO can drift by ~200 ppm/°C. Ex: 1 MHz/°C drift for a 5 GHz offset. For higher stability, use an external reference.</ | ||
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- | VCO TUNE adjusts the control voltage of the internal VCO, thereby adjusting the frequency of the VCO. The frequency of the VCO can be monitored with the REF FREQ Monitor when the D2-135 is in a mode that uses the internal VCO. | ||
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- | **Ramp Amp (1-turn knob)** | ||
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- | The RAMP AMP sets the amplitude of the internal ramp generator. | ||
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- | **Optical Input (SC Fiber Input; obsolete) ** - // | ||
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- | ** **Optical beat-note input for the D2-135-FC. | ||
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- | **Beat-note Input (SMA Electrical Input) - **// | ||
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- | // | ||
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- | **Gain Sign (two-position switch)** | ||
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- | The GAIN SIGN reverses the sign of the charge pump (CP) output. Effectively this selects whether the OPLS locks the slave laser to a frequency above or below the master laser frequency. | ||
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- | **Laser State (three-position switch)** | ||
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- | The lock switch has three positions. | ||
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- | **Fine Gain (1-turn knob)** | ||
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- | The FINE GAIN control adjusts the loop filter' | ||
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- | **Coarse Gain (eight-position switch)** | ||
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- | The COARSE GAIN sets the overall proportional gain of the circuit without changing the location of any corners or poles in the loop filter transfer function. The coarse gain adjusts in steps of 6 dB from 0 dB to -76 dB. | ||
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- | **Servo Output** | ||
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- | The SERVO OUTPUT is a voltage output to control the frequency of (typically) the slave laser. When the OPLS is used with the D2-105 Laser Controller, the SERVO OUTPUT is connected to the CURRENT SERVO INPUT on the Laser Controller. | ||
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- | **Feed Forward Input** | ||
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- | FEED FORWARD INPUT is a high impedance input that gets summed in with the SERVO OUTPUT. It is designed to provide feed forward when jumping the offset frequency of the laser. | ||
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- | ====Right Side Panel ==== | ||
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- | < | ||
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- | The feedback loop is defined by the Gain vs. Frequency plot shown above. ƒ< | ||
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- | **Integrator (****ƒ**< | ||
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- | Sets the frequency of the integrator (ƒ< | ||
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- | **Differential (****ƒ**< | ||
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- | Sets the frequency of the differentiator (ƒ< | ||
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- | **Differential Gain (25-turn trimpot) ** | ||
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- | Sets the maximum differential gain. 25-turn trimpot adjusts the gain from 5 dB to 15 dB. | ||
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- | **Integrator (****ƒ**< | ||
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- | Sets the frequency of the high-frequency roll-off (ƒ< | ||
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- | **Ramp Master / Slave (Not Shown)** | ||
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- | This jumper is only accessible by removing the right side panel and sets whether the ramp input is in master or slave mode. It is factory set to be in MASTER MODE. In SLAVE MODE (jumper off) the RAMP signal is generated externally and input through the back panel RAMP I/O port. In MASTER MODE (jumper on) the ramp is generated internally and is sent out to the RAMP I/O port for driving other D2-135 OPLS or D2-125 Laser Servos configured in SLAVE MODE. | ||
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- | ====Back-panel Section==== | ||
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- | == Power I/O == | ||
- | **(9-pin D-sub)** | ||
- | <WRAP center round important 60%> | ||
- | Never connect this device to a power supply that is switched on and supplying power. Always turn off the power supply, make connections to this device, and then re-energize the power supply. | ||
- | </ | ||
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- | Each electronics module is powered through a 9-pin D-sub connector through either a power bridge unit or a serial cable with 9-pin D-sub connectors, which is convenient when the unit must be moved for access to the side panels. | ||
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- | {{ : | ||
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- | **Computer Control (9-pin D-sub)** | ||
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- | The 9 pin COMPUTER CONTROL signals allows an external computer to override the front-panel and set the mode of the OPLS. All signal pins float high and can be driven by a open drain or open collector. The pin definitions are shown below: | ||
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- | {{ : | ||
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- | Pin 1 must be pulled to ground to enable computer control. Otherwise, all other pins on this cable are ignored and the OPLS state is set by the front-panel rotary switch. Pin 2 controls whether the gain sign is positive (pin 2 high) or negative (pin 2 low). For pins 3 through 6, refer to the tables below. | ||
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- | <WRAP half column> | ||
- | < | ||
- | ^ ^^ VCO External (pin 3) ^^ | ||
- | ^ ^^ Low ^ High ^ | ||
- | ^ VCO High Range (pin 4) ^Low |VCO Low |External| | ||
- | ^ ::: ^High |VCO High |External| | ||
- | </ | ||
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- | </ | ||
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- | <WRAP half column> | ||
- | < | ||
- | ^ ^^ N2 (pin 6) ^^ | ||
- | ^ ^^ Low ^ High ^ | ||
- | ^ N1 (pin 5) ^Low | N=8 | N=32 | | ||
- | ^ ::: ^High | N=16 | N=64 | | ||
- | </ | ||
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- | </ | ||
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- | <WRAP clear></ | ||
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- | **Ref. Freq. In** | ||
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- | When the OPLS uses an external frequency reference, this input is used to supply the frequency reference. | ||
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- | **Beat-note Monitor (÷2)** | ||
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- | This is a 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. | ||
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- | **Ramp TTL** | ||
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- | Same as the front panel signal. | ||
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- | **Ramp IN / OUT ** | ||
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- | The OPLS is shipped with the RAMP in MASTER MODE. In this configuration, | ||
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- | **VCO Freq. Adjust** | ||
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- | This input is summed in with the VCO TUNE potentiometer to set the voltage to the VCO, and thus the reference frequency when the OPLS is using the internal VCO. The impedance to this input in 1 kΩ and can accept voltages from -10V to +10V and should tune over entire VCO range, provided that the VCO TUNE potentiometer is set in the middle of the VCO range. | ||
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- | =====Understanding Gain in the OPLS===== | ||
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- | As described above in the [[Offset Phase Lock Servo# | ||
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- | =====Understanding the Transfer Function===== | ||
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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 opls_side_panel> | ||
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- | =====Calculating Phase Noise ===== | ||
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- | The phase-noise specified in the [[d2: | ||
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- | '' | ||
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- | where N is the value of the divider and F< | ||
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- | =====Help ===== | ||
- | [[d2: | ||
- | +1(303) 296-6766 or \\ | ||
- | < | ||
d2/offset_phase_lock_servo.txt · Last modified: 2023/11/16 00:02 by 127.0.0.1