Multi Frequency Laser Driver for Near Infrared Optical Spectroscopy in Biomedical ApplicationIntroductionSpectroscopySlide 4Slide 5Slide 6Slide 7Noise measurement of DriverSlide 9Slide 10Slide 11Slide 12Slide 13ConclusionMulti Frequency Laser Driver for Near Infrared Optical Spectroscopy in Biomedical ApplicationChenpeng Mu Department of Electrical and Computer Engineering, Drexel Univ, Philadelphia,PA, 19104IntroductionWhat is tissue spectroscopy?Near infrared spectroscopy system introduction.Driver designGain, frequency response, linearity and noiseSystem evaluationOptical property extractionConclusionSpectroscopyAbsorption and scattering parameters of tissue are different with different wavelength of light.Frequency domain photon migration (FDPM) is used to extract optical properties of tissue(absorption and scattering).Photon penetrates tissue and penetration depth depends on modulation frequency.Tissue is multi-layer constructure, so multi-frequency should be used for better spatial resolution.GHzFrequenciesMHzFrequenciesDetector-1 Detector-2Source-1FatMuscle760 850 980Laser Diode SystemBroadBandwidthFrequencyDomainInstrument TURBID MEDIUM Network Analyzer (HP 8753ES)Sample channelRF sourceSP4TRF SwitchLD4980 nmLD1680 nmLD 2780nmLD3830 nm4 X N Optical SwitchSource Fibers…NAmplifierPhotodiodeM X 1 Optical Switch…MDetector FibersTurbid medium(tissue)Optical link driverDesignedActiveLaserDriver:ACsimulationFrequency (MHz) Input current (mA) Output current (mA)100 5.63 453.70200 6.94 453.31300 8.69 452.75400 10.66 451.98500 12.73 450.99600 14.86 449.80700 17.01 448.41800 19.18 446.81900 21.33 445.031000 23.47 443.06•RF current is monitored•RF current = 450mAP_ACPORT3Freq=freqPac=polar(dbmtow(0),0)Z=50 OhmNum=3CC11C=10 pFRR21R=50 OhmI_ProbeI_Probe1V_DCSRC12Vdc=1.5 VRR1R=6.5 OhmLL2R=L=1000 nHLL5R=L=82 nHLL3R=L=82 nHCC4C=100 pFRR8R=3100 OhmRR18R=477 OhmRR2R=500 OhmCC7C=100 pFLL4R=L=82 nHRR12R=130 OhmV_DCSRC9Vdc=12 VI_ProbeI_Probe2CC1C=100 pFCC9C=100 pFV_DCSRC1Vdc=12 VBJ T_NPNBJ T1Mode=nonlinearTemp=Region=Area=Model=BJ TM1DesignedActiveLaserDriver:AmplitudeResponseandPhaseResponseSimulationvs.Measurement(A)(B)0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90.1 1.0369121518020Frequency(GHz)S21(dB)SimulationMeasurementPhase distortion < 1 degreeMagnitude distortion < 1.5 dBNoisemeasurementofDriverCalculation0246810100 300 500 700 900Frequency (MHz)Noise Figure (dB)+3.3VExperimental SetupLaser Diode DriveroutputI_ NoiseRIN_ Nois e1I_NoiseS hot_Nois e1I_ NoiseDark_Nois e1T ermT erm2Z=50 OhmNum=2S 2P _ E qnS 2P 1S [2,2]=0S [2,1]=1S [1,2]=1S [1,1]=0I_ NoiseT hermal_Nois eAmplifierAMP 4S 12=0S 22=polar(0,180)S 11=polar(0,0)S 21=dbpolar(36,0)CC9C=0.45 pFP _ACP ORT 1Freq=freqP ac=polar(dbmtow(-5),0)Z=50 OhmNum=1CCCSS RC4G=Ita_L*Hp*L_ F*Ita_ DCC4C=100 pFI_ P robeR_ j_ current1CC1C=100 pFI_ P robeInput_ currentRR2R=3100 OhmLL2R=L=82 nHRR3R=477 OhmLL1R=L=82 nHRR1R=50 OhmCC2C=1.0 pFV_ DCS RC1Vdc=12 VCC3C=100 pFLL3R=L=82 nHRR4R=500 OhmB J T _NP NB J T 1Mode=nonlinearT emp=Region=Area=Model=B J T M1RR6R=1 OhmLL6R=L=9 nHCC7C=0.6 pFCC6C=1.5 pFLL5R=L=0.7 nHI_P robeDriving_currentV_ DCS RC3Vdc=12 VV_ DCS RC2Vdc=12 VRR5R=130 OhmLL4R=L=82 nHCC5C=390 pFCC8C=1.5 pFLaser DriverLaser Diode ModelPhoto DetectorOptical System Performance: SimulationHamamatsu Amplifier, G=34dBLDAPD (Photodetector)Automated Network Analyzer (ANA)Optical transmitter (driver)TISSUEm1freq=300.0MHzmag(output)=0.116m2freq=300.0MHzoutput.noise=2.215uV0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90.1 1.01E-41E-31E-21E-11E-53E-1freq, GHzmag(output)m1output.noise, Vm2Total Noise 2.215uVThermal Noise 1.809uVRIN Noise 1.183uVShot Noise 0.488uVDark Noise 0.011uVThermal Noise is dominant.0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90.1 1.04555653570freq, GHzVoltage S/N ratio (dB)Optical Link Performance: simulation resultsABPhase distortion < 5 degreesMagnitude distortion < 2 dBOptical Link Performance: Experiment resultPhaseMagnitudeExtractionofOpticalProperties:TransmissionModelFor N number of dipoles one can get the analytical solution for transmittance as:])()(exp()())exp([4),(01mRmikRmRmikRDStrccoNm2))',(,(2))',(,(2phantomPsatheoryPinPphantomAsatheoryAiinACalibration-corrected data are fitted with normalized theoretical transmittance to extract the optical absorption and scattering properties of the tissue.ExtractionofOpticalProperties:ExperimentResultPhantomANAAPDLaser Mountd Phantom ExtractedF (MHz) a (cm-1) s’ (cm-1) a (cm-1) s’ (cm-1)118 0.05 10 0.052 10.1226 0.05 10 0.054 10.5316 0.05 10 0.048 9.8838 0.05 10 0.058 11.0910 0.05 10 0.051 11.2964 0.05 10 0.057 10.6ConclusionAn active laser driver is developed for a broadband operation of four-color sources in near IR. A multi-frequency domain instrument is reported for near infrared light spectroscopy applications. High power (up to 1.2W) and high-speed (up to 1GHz) laser diode driver exhibited a flat frequency response. Extracted optical parameters a and s for phantom resembling breast tissue demonstrates the high accuracy of this measurement technique and extraction