Lightwave Communications LDX-3232 manual Operating a Laser in Constant Power P Mode

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O P E R A T I O N

Operating a Laser in Constant Power (P) Mode

C H A P T E R 2

Conditions That Will Automatically Shut Off the LASER OUTPUT

The following conditions will automatically cause the instrument to disable the current source output:

•LASER High Power Limit

•LASER Interlock / Key Lock Turned Off

•LASER Open Circuit or Voltage Limit

Operating a Laser in Constant Power (P) Mode

Suppose you want to operate a 3 mW laser at constant 1mW level. The LDX-3232 allows you to operate the laser current source driver in a Constant Power mode. In this mode, the LDX-3232 drives current to the laser to reach a setpoint power value (in mW). The control loop feedback parameter is photodiode current that the LDX-3232 converts to optical power via a user-defined photodiode responsivity number. If laser power changes due to internal or environmental conditions, the LDX-3232 will increase/decrease the current to the laser to maintain the power setpoint. The following paragraphs detail the instrument configuration in Constant Power Mode.

To set the LDX-3232 in Constant Power mode, select P in the MODE section of the front panel by toggling the SELECT push button. Repeatedly pressing the (MODE) SELECT switch cycles through the current (I), light power (P), or high bandwidth current (IHBW) control modes. The LED indicator shows the selected mode.

Entering Photodiode Responsivity Values

The photodiode responsivity, CAL photodiode, is used to convert between photodiode current and optical power of the laser diode. To enter the CAL photodiode parameter, select CAL PD with the (PARAMETER) SELECT push button by toggling down past LIM P. The indicator becomes lit when CAL PD is selected and the display indicates the responsivity parameter in µA/mW (not an- nunciated). Rotate the adjust knob while holding the (PARAMETER) SET push button to enter a new value for responsivity. When the correct value is displayed, store the number by releasing the (PARAMETER) SET pushbutton.

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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 Comments, Suggestions, and Problems Description of the problemModel Number Serial Number End-User Name Company Phone Fax 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 Type Pulse Width Delay TTL13 µs 12 ms 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 ConnectorSetting the PD Bias Photodiode ConnectionsGrounding Considerations Operating a Laser in Constant Current I Mode Front Panel Operation Display 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 AddressLDX-3232 Current Source Command Set Command SyntaxChanging Operation from Local to Remote OFF OLD NEW True False SET Reset LASLDI? LDX-3232 Command Path Structure Command PathsIEEE488.2 Command Commands LDX-3232 Frequently Used Commands NoneLIM Status Reporting Event and Condition RegistersOperation Complete Definition 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 ReferenceERRors? LASerCALMDCalmd LAS Calpd LASerCALMD? Responsivity CAL PD parameter setting Syntax DiagramSelected. This procedure is outlined in Chapter LASerCALLDICalibration for that bandwidth LASerCALLDV LASerCALLDI?LDI LAS CAL LAS CAL LDVTrue measured value. This procedure is outlined in Chapter LASerCALLDV?LASerCALMDI 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 SETLASerENABleCOND LASerDISplaySET?LASDISPLAYSET? LASerENABleCOND? BitLAS Enab Cond 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?LASerLIMitMDP LASerLIMitMDP?MDP LAS LIM LASerLIMitV? LASerLIMitVLASerMDI? LASerMDIMDI LAS IPD MDP P PD setpoint would be usedLASerMDLN LASerMDLN?LAS Mdln LASerMDP LASerMDP?MDP LAS LAS Mode Ihbw LAS ModeLASerMODE? LASerMODEIHBWLASerMODEILBW LAS Mode MDPLASerMODEMDP LasmodeilbwLASerOUTput LASerOUTput?LAS OUT 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 octalLDX-3232 was last powered up Time clock is independent of the Timer clockTime 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 TroubleshootingDescription Manufacturer/Model Specification Recommended EquipmentDMM 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 rangeGpib Command Remote Calibration of the LDX-3232 Current SourceLimit 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