Lightwave Communications LDX-3232 manual Modulating the Laser Current Source

Page 103

FUNCTIONS AND FEATURES

Modulating the Laser Current Source

C H A P T E R 5

Setting up the Current Source for a modulated laser injection current is easy. The (MOD) EXTERNAL connector (BNC) on the front panel is the input for the modulated signal. Connect a modulating voltage signal from a standard function generator, for example, to this connector. The modulation port input impedance is 1 kΩ. The transfer function for the low and high current ranges of the LDX-3232 are 200 mA/V and 400 mA/V.

Set the LDX-3232 in Constant Current High Bandwidth Mode by selecting IHBW in the MODE section of the front panel. Do this by toggling the (MODE) SELECT push button until the IHBW indicator is illuminated. Repeatedly pressing the (MODE) SELECT switch cycles through the current (I), optical power (P), or high bandwidth current (IHBW) control modes.

Next, set the current source range by selecting the

2000 mA range indicated by the accompanying LED. You will need to press the select push button twice to change the range. It must be pressed twice quickly (within less than one second) to switch between modes, and the current source output must be off (MODE ON indicator unlit) in order to change ranges.

The limit clamp function for DC output current applies to the modulated current as well protecting your laser in any mode. To accomplish setting the current source limit, use the (PARAMETER) SELECT push button LIM I. Press the (PARAMETER) SET push button and rotate the adjust knob. Set the limit to 1750 mA. Once the (PARAMETER) SET push button is released, the new parameter value is stored in non-volatile memory.

When the laser current limit is reached, the CURRENT LIMIT error indicator flashes. The current limit setting is independent of the voltage drop of the device connected to the laser output, and therefore, no dummy load is required for precise adjustment of the current limit. Furthermore, since the current limit circuitry is fully independent of the main current control, the current limit can be adjusted safely, even while the current source output is active.

Now you are ready to modulate the laser injection current. To enable the Current Source output, press the push button labeled (MODE) OUTPUT. The accompanying LED labeled ON will illuminate indicating that the laser current source's output is enabled. The instrument will drive the current source to the value set by the corresponding MODE setpoint. Turn on the function generator (modulation source) to inject the modulation signal.

04_06

LDX-3232

87

Page 102 Page 104
Image 103
Page 102 Page 104
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 Description of the problem Comments, Suggestions, and ProblemsModel Number Serial Number End-User Name Company Phone Fax Xiv LDX-3232 Product Overview Introduction and SpecificationsGrounding Requirements Installing Your LDX-3232 High Compliance Current SourceAC Line Power Requirements Initial InspectionOperating the LDX-3232 Precision Current Source Gpib ConnectorTilt-Foot Adjustment Gpib AddressLDX-3232 Front View Maintenance Specifications TTL Type Pulse Width Delay13 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 ConnectorPhotodiode Connections Setting the PD BiasGrounding Considerations Front Panel Operation Operating a Laser in Constant Current I ModeDisplay 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 AddressCommand Syntax LDX-3232 Current Source Command SetChanging Operation from Local to Remote OFF OLD NEW True False SET Reset LASLDI? LDX-3232 Command Path Structure Command PathsIEEE488.2 Command Commands None LDX-3232 Frequently Used CommandsLIM Event and Condition Registers Status ReportingOperation 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 Used to enter the laser voltage calibration mode Used to create a delay in the execution of furtherCommands Used to enter the laser current calibration modeReturns the value of the LAS conditions enable register Returns status of photodiode monitor power displayEnables Laser display to show parameter values Sets the enable register for Laser conditionsOr P optical power Used to return the optical power from monitorUsed to set the constant optical power setpoint, if Used to enable/disable the front panel modulation inputUsed to return the Laser setpoint tolerance value Returns the status of the Term commandPowered up Returns the elapsed time since the timer was last resetCommand Description Format LDX-3232 Device-Dependent CommandsDelay LDX-3232 Device-Dependent Command ReferenceLASerCALMD ERRors?Calmd LAS Calpd LASerCALMD? Responsivity CAL PD parameter setting Syntax DiagramLASerCALLDI Selected. This procedure is outlined in ChapterCalibration for that bandwidth LAS CAL LDV LASerCALLDI?LASerCALLDV LDI LAS CALLASerCALLDV? True measured value. This procedure is outlined in ChapterLASerCALMDI LAS CAL IPD LASerCALMDI?LASerCOND? MDILASerDEC LASDIS? LASerDISplayLASerDISplay? LAS DISLDI LASerDISplayLDILASerDISplayLDI? LasdisldiLASDISLDV? Voltage measurement Syntax DiagramLASerDISplayLDV LASerDISplayLDV?LAS DIS IPD LASerDISplayMDILASerDISplayMDI? LAS DIS MDILAS DIS MDP LASerDISplayMDPLASerDISplayMDP? PPDLAS DIS SET LASerDISplayPARAMLASerDISplaySET LAS DIS ParamLASerDISplaySET? LASerENABleCONDLASDISPLAYSET? Bit LASerENABleCOND?LAS Enab Cond Lasenabevent LASerENABleEVEntAn nrf value whose sum represents the bits that are enabled Action enables the Laser status event register so thatLAS Enab EVE LASerENABleEVEnt?LASerENABleOUTOFF LAS Enab Outoff LASerENABleOUTOFF?LAS EVE LASerENABleEVEnt commandCommand while the condition status is constantly changing LASerEVEnt?Function for the Laser output LASerINCLAS LDI This measurement is updated approximately once every 600 msLASerLDI LASerLDI?LAS LDV LASerLDVLASerLDV? For LDV calibrationLAS LIM LASerLIMitI2LASerLIMitI2? Limit in use depends on the Laser output range selectionLASLIMI4? Displayed, and then releasing the SET switchLASerLIMitI4 LASerLIMitI4?LASerLIMitMDP? LASerLIMitMDPMDP LAS LIM LASerLIMitV? LASerLIMitVMDP P PD setpoint would be used LASerMDILASerMDI? MDI LAS IPDLASerMDLN? LASerMDLNLAS Mdln LASerMDP? LASerMDPMDP LAS LASerMODEIHBW LAS ModeLAS Mode Ihbw LASerMODE?Lasmodeilbw LAS Mode MDPLASerMODEILBW LASerMODEMDPLASerOUTput? LASerOUTputLAS OUT LASRAN? LASerRANgeLASerRANge? LAS RANLASerSETMDI? Where the response is the constant I setpoint value, in mA30 µA, for use in constant P mode with Calpd = LASerSETLDI?100 µA Where the response is the constand PPD setpoint, in mWLASerSETMDP? LASerSTEPLAS TOL LASerTOLerance commandLASerSTEP? LASerTOLeranceMES LASerTOLerance?MESsage Second is the time window, in secondsRADix MESsage?Means hexadecimal, and OCT means octal Term 0 command is sent or the LDX-3232 is powered offRADix? RADTime clock is independent of the Timer clock LDX-3232 was last powered upTime Seconds since the last TIMER? query was issued Since the last TIMER? query was issuedTimer Last TIMER? query is returnedSaving 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 TroubleshootingRecommended Equipment Description Manufacturer/Model SpecificationDMM Current Limit Local Calibration of the LDX-3232 Current SourceCurrent Source Calibration RangeIPD Current Calibration IPD Setpoint Constant powerCAL PD Set equal to zeroSet to FS full scale of range Laser ModeLaser Forward Voltage Measurement Calibration 2000 mARemote Calibration of the LDX-3232 Current Source Gpib CommandLimit Lasldi nrf value command IPD Setpoint Function State Gpib Command Current source must be recalibrated Troubleshooting GuideGeneral EEPROM, Lllll will be displayed on the display the laserCommand Feature can be defeated via the Lasenableoutoff101 Response Message
Top Page Image Contents