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Multi Frequency Laser Driver for Near Infrared Optical Spectroscopy in Biomedical Application. Chenpeng Mu Department of Electrical and Computer Engineering, Drexel Univ, Philadelphia,PA, 19104. Introduction. What is tissue spectroscopy? Near infrared spectroscopy system introduction. - PowerPoint PPT Presentation
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Multi Frequency Laser Driver for Near Infrared Optical
Spectroscopy in Biomedical Application
Chenpeng Mu
Department of Electrical and Computer Engineering, Drexel Univ, Philadelphia,PA, 19104
IntroductionWhat is tissue spectroscopy?Near infrared spectroscopy system introduction.Driver design
Gain, frequency response, linearity and noise
System evaluationOptical property extractionConclusion
SpectroscopyAbsorption 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.
GHzFrequencies
MHzFrequencies
Detector-1 Detector-2Source-1
Fat
Muscle
760 850 980
Laser Diode System
Broad Bandwidth Frequency Domain Instrument
TURBID MEDIUM
Network Analyzer (HP 8753ES)Sample channelRF source
SP4TRF Switch
LD4980 nm
LD1680 nm
LD 2780nm
LD3830 nm
4 X N Optical Switch
Source Fibers …
N
Amplifier
Photodiode
M X 1 Optical Switch
…M Detector Fibers
Turbid medium(tissue)
Optical link driver
Designed Active Laser Driver : AC simulation
Frequency (MHz) Input current (mA) Output current (mA)
100 5.63 453.70
200 6.94 453.31
300 8.69 452.75
400 10.66 451.98
500 12.73 450.99
600 14.86 449.80
700 17.01 448.41
800 19.18 446.81
900 21.33 445.03
1000 23.47 443.06
•RF current is monitored•RF current = 450mA
P_ACPORT3
Freq=freqPac=polar(dbmtow(0),0)Z=50 OhmNum=3
CC11C=10 pF
RR21R=50 Ohm
I_ProbeI_Probe1 V_DC
SRC12Vdc=1.5 V
RR1R=6.5 Ohm
LL2
R=L=1000 nH
LL5
R=L=82 nH
LL3
R=L=82 nH
CC4C=100 pF
RR8R=3100 Ohm
RR18R=477 Ohm
RR2R=500 Ohm
CC7C=100 pF
LL4
R=L=82 nH
RR12R=130 Ohm
V_DCSRC9Vdc=12 V
I_ProbeI_Probe2
CC1C=100 pF
CC9C=100 pF
V_DCSRC1Vdc=12 V
BJ T_NPNBJ T1
Mode=nonlinearTemp=Region=Area=Model=BJ TM1
Designed Active Laser Driver : Amplitude Response and Phase Response
Simulation vs. Measurement
(A)
(B)
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90.1 1.0
3
6
9
12
15
18
0
20
Frequency(GHz)
S21(
dB)
SimulationMeasurementPhase distortion < 1 degreeMagnitude distortion < 1.5 dB
Noise measurement of Driver
Calculation
0
2
4
6
8
10
100 300 500 700 900
Frequency (MHz)
Noi
se F
igur
e (d
B)
+3.3V
Experimental Setup
Laser Diode Driver
outputI_NoiseRIN_Noise1
I_NoiseShot_Noise1
I_NoiseDark_Noise1
T ermT erm2
Z=50 OhmNum=2 S2P _Eqn
S2P 1
S[2,2]=0S[2,1]=1S[1,2]=1S[1,1]=0
I_NoiseT hermal_Noise
AmplifierAMP 4
S12=0S22=polar(0,180)S11=polar(0,0)S21=dbpolar(36,0)
CC9C=0.45 pF
P _ACP ORT 1
Freq=freqP ac=polar(dbmtow(-5),0)Z=50 OhmNum=1
CCCSSRC4G=Ita_L*Hp*L_F*Ita_D
CC4C=100 pF
I_P robeR_j_current1
CC1C=100 pF
I_P robeInput_current
RR2R=3100 Ohm
LL2
R=L=82 nH
RR3R=477 Ohm
LL1
R=L=82 nH
RR1R=50 Ohm
CC2C=1.0 pF
V_DCSRC1Vdc=12 V
CC3C=100 pF
LL3
R=L=82 nH
RR4R=500 Ohm
BJ T _NP NBJ T 1
Mode=nonlinearT emp=Region=Area=Model=BJ T M1
RR6R=1 Ohm
LL6
R=L=9 nH
CC7C=0.6 pF
CC6C=1.5 pF
LL5
R=L=0.7 nH
I_P robeDriving_current
V_DCSRC3Vdc=12 V
V_DCSRC2Vdc=12 V
RR5R=130 Ohm
LL4
R=L=82 nH
CC5C=390 pF
CC8C=1.5 pF
Laser Driver
Laser Diode Model
Photo Detector
Optical System Performance: Simulation
Hamamatsu Amplifier, G=34dB
LD APD (Photodetector)
Automated Network Analyzer (ANA)
Optical transmitter
(driver)
TISSUE
m1freq=300.0MHzmag(output)=0.116
m2freq=300.0MHzoutput.noise=2.215uV
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90.1 1.0
1E-4
1E-3
1E-2
1E-1
1E-5
3E-1
freq, GHz
mag(o
utp
ut)
m1
outp
ut.nois
e, V
m2
Total Noise 2.215uV
Thermal Noise 1.809uV
RIN Noise 1.183uV
Shot Noise 0.488uV
Dark Noise 0.011uV
Thermal Noise is dominant.
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90.1 1.0
45
55
65
35
70
freq, GHz
Vol
t age
S/ N
rat
i o (
dB)
Optical Link Performance: simulation results
A
B
Phase distortion < 5 degreesMagnitude distortion < 2 dB
Optical Link Performance: Experiment result
Phase
Magnitude
Extraction of Optical Properties: Transmission Model
For N number of dipoles one can get the analytical solution for transmittance as:
])(
)(exp(
)(
))exp([
4),( 0
1 mR
mikR
mR
mikR
D
Str
c
c
o
N
m
2))',(
,(2))',(
,(2
phantomP
satheoryPinP
phantomAsatheoryA
iinA
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
Phantom
ANA
APDLaser
Mount
d Phantom Extracted
F (MHz) a (cm-1) s’ (cm-1) a (cm-1) s’ (cm-1)
118 0.05 10 0.052 10.1
226 0.05 10 0.054 10.5
316 0.05 10 0.048 9.8
838 0.05 10 0.058 11.0
910 0.05 10 0.051 11.2
964 0.05 10 0.057 10.6
ConclusionAn 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 method.