Lightwave Communications LDX-3232 manual Photodiode Connections, Setting the PD Bias

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O P E R A T I O N

Connecting to the Laser

Photodiode Connections

C H A P T E R 2

Many laser diode modules contain an internal photodiode that monitors the back- facet emission of the laser. Usually, this photodiode is internally connected to either the laser anode or cathode.

The photodiode and laser connections to the LDX-3232 are electrically isolated from ground and each other. So, if a 4 pin connection is made (no common connections), no additional jumpers are required. Figures 2.1 - 2.4 show the recommended connections and shielding for 3-pin lasers (where the common connection is internal to the device). A 4-pin laser should be connected with the same shielding as shown in Figure 2.1, but the common connection (between the photodiode and the laser) is optional.

Setting the PD Bias

The LDX-3232 provides an adjustable reverse bias of 0-5 VDC for the photodiode. To set the photodiode bias to 5 V reverse bias, turn the back panel PD BIAS ADJUST fully clockwise. To set the photodiode bias to 0 V reverse bias, turn the back panel PD BIAS ADJUST fully counter-clockwise.

Grounding Considerations

The LASER outputs of the LDX-3232 High Compliance Current Source are isolated from chassis ground, allowing either output terminal to be grounded at the user's option. Figures 2.1 - 2.4 show the proper earth-ground shielding for laser diode/photodiode connections.

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LDX-3232

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Contents User’s Guide Page Table of Contents Remote Operation Command Reference Iv LDX-3232 List of Figures Vi LDX-3232 List of Tables Viii LDX-3232 General Safety Considerations Safety Information and the ManualSafety Marking Symbols Safety SymbolsWarranty Claims for Shipping Damage Model Number Serial Number End-User Name Company Phone Fax Comments, Suggestions, and ProblemsDescription of the problem Xiv LDX-3232 Product Overview Introduction and SpecificationsAC Line Power Requirements Installing Your LDX-3232 High Compliance Current SourceInitial Inspection Grounding RequirementsTilt-Foot Adjustment Gpib ConnectorGpib Address Operating the LDX-3232 Precision Current SourceLDX-3232 Front View Maintenance Specifications 13 µs 12 ms Type Pulse Width DelayTTL Description Model Number Available Options and AccessoriesPower On Sequence Applying Power to Your LDX-3232Power On State Connecting to the LaserCommon Laser Cathode Photodiode Anode Interlock Connections Back Panel LD ConnectorGrounding Considerations Setting the PD BiasPhotodiode Connections Display Operating a Laser in Constant Current I ModeFront Panel Operation Setting Up the Precision Current Source E R a T I O N Entering Photodiode Responsivity Values Operating a Laser in Constant Power P ModeMethod to calculate the responsivity is suggested below LDX-3232 Error Indicators Error IndicatorsError Indicators LDX-3232 Changing the Gpib Address Reading the Gpib AddressChanging Operation from Local to Remote LDX-3232 Current Source Command SetCommand Syntax OFF OLD NEW True False SET Reset LASLDI? LDX-3232 Command Path Structure Command PathsIEEE488.2 Command Commands LIM LDX-3232 Frequently Used CommandsNone Operation Complete Definition Status ReportingEvent and Condition Registers LDX-3232 Status Reporting Schematic Diagram Output Off Register Disabled 10 N/A Enabled 11 N/A 12 N/A 13 N/A 14 N/A 15 N/ALASerENABleOUTOFF nrf LASerENABleOUTOFF? Error Messages Command Timing and CompletionResponse Message Error Code ClassificationsMode Commands Used to create a delay in the execution of furtherUsed to enter the laser current calibration mode Used to enter the laser voltage calibration modeEnables Laser display to show parameter values Returns status of photodiode monitor power displaySets the enable register for Laser conditions Returns the value of the LAS conditions enable registerUsed to set the constant optical power setpoint, if Used to return the optical power from monitorUsed to enable/disable the front panel modulation input Or P optical powerPowered up Returns the status of the Term commandReturns the elapsed time since the timer was last reset Used to return the Laser setpoint tolerance valueCommand Description Format LDX-3232 Device-Dependent CommandsDelay LDX-3232 Device-Dependent Command ReferenceCalmd LAS Calpd ERRors?LASerCALMD LASerCALMD? Responsivity CAL PD parameter setting Syntax DiagramCalibration for that bandwidth Selected. This procedure is outlined in ChapterLASerCALLDI LASerCALLDV LASerCALLDI?LDI LAS CAL LAS CAL LDVLASerCALMDI True measured value. This procedure is outlined in ChapterLASerCALLDV? LASerCOND? LASerCALMDI?MDI LAS CAL IPDLASerDEC LASerDISplay? LASerDISplayLAS DIS LASDIS?LASerDISplayLDI? LASerDISplayLDILasdisldi LDILASerDISplayLDV Voltage measurement Syntax DiagramLASerDISplayLDV? LASDISLDV?LASerDISplayMDI? LASerDISplayMDILAS DIS MDI LAS DIS IPDLASerDISplayMDP? LASerDISplayMDPPPD LAS DIS MDPLASerDISplaySET LASerDISplayPARAMLAS DIS Param LAS DIS SETLASDISPLAYSET? LASerENABleCONDLASerDISplaySET? LAS Enab Cond LASerENABleCOND?Bit An nrf value whose sum represents the bits that are enabled LASerENABleEVEntAction enables the Laser status event register so that LasenabeventLAS Enab EVE LASerENABleEVEnt?LASerENABleOUTOFF LAS Enab Outoff LASerENABleOUTOFF?Command while the condition status is constantly changing LASerENABleEVEnt commandLASerEVEnt? LAS EVEFunction for the Laser output LASerINCLASerLDI This measurement is updated approximately once every 600 msLASerLDI? LAS LDILASerLDV? LASerLDVFor LDV calibration LAS LDVLASerLIMitI2? LASerLIMitI2Limit in use depends on the Laser output range selection LAS LIMLASerLIMitI4 Displayed, and then releasing the SET switchLASerLIMitI4? LASLIMI4?MDP LAS LIM LASerLIMitMDPLASerLIMitMDP? LASerLIMitV? LASerLIMitVLASerMDI? LASerMDIMDI LAS IPD MDP P PD setpoint would be usedLAS Mdln LASerMDLNLASerMDLN? MDP LAS LASerMDPLASerMDP? LAS Mode Ihbw LAS ModeLASerMODE? LASerMODEIHBWLASerMODEILBW LAS Mode MDPLASerMODEMDP LasmodeilbwLAS OUT LASerOUTputLASerOUTput? LASerRANge? LASerRANgeLAS RAN LASRAN?30 µA, for use in constant P mode with Calpd = Where the response is the constant I setpoint value, in mALASerSETLDI? LASerSETMDI?LASerSETMDP? Where the response is the constand PPD setpoint, in mWLASerSTEP 100 µALASerSTEP? LASerTOLerance commandLASerTOLerance LAS TOLMESsage LASerTOLerance?Second is the time window, in seconds MESRADix MESsage?RADix? Term 0 command is sent or the LDX-3232 is powered offRAD Means hexadecimal, and OCT means octalTime LDX-3232 was last powered upTime clock is independent of the Timer clock Timer Since the last TIMER? query was issuedLast TIMER? query is returned Seconds since the last TIMER? query was issuedSaving and Recalling from the Front Panel Functions and FeaturesSaving and Recalling Under Remote Operation Using the Laser Compliance Voltage AdjustmentLDX-3232 Rear Panel Using the LDX-3232 Current Source’s Trigger FunctionBNC Interlock Usage Example Modulating the Laser Current SourceModulating the Laser Current Source Functions and Features Calibration Overview Calibration and TroubleshootingDMM Description Manufacturer/Model SpecificationRecommended Equipment Current Source Calibration Local Calibration of the LDX-3232 Current SourceRange Current LimitIPD Current Calibration CAL PD Constant powerSet equal to zero IPD SetpointLaser Forward Voltage Measurement Calibration Laser Mode2000 mA Set to FS full scale of rangeLimit Gpib CommandRemote Calibration of the LDX-3232 Current Source Lasldi nrf value command IPD Setpoint Function State Gpib Command General Troubleshooting GuideEEPROM, Lllll will be displayed on the display the laser Current source must be recalibratedCommand Feature can be defeated via the Lasenableoutoff101 Response Message