Injection Locked Injection Locked Oscillators Oscillators Optoelectronic Optoelectronic Applications Applications E. Shumakher, J. Lasri, B. Sheinman, G. Eisenstein, E. Shumakher, J. Lasri, B. Sheinman, G. Eisenstein, D. Ritter D. Ritter Electrical Engineering Dept. TECHNION Electrical Engineering Dept. TECHNION Haifa ISRAEL Haifa ISRAEL Q 1, ω 1 Q 2, ω 2
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Injection Locked Oscillators Optoelectronic Applications E. Shumakher, J. Lasri, B. Sheinman, G. Eisenstein, D. Ritter Electrical Engineering Dept. TECHNION.
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E. Shumakher, J. Lasri, B. Sheinman, G. Eisenstein, D. RitterE. Shumakher, J. Lasri, B. Sheinman, G. Eisenstein, D. RitterElectrical Engineering Dept. TECHNIONElectrical Engineering Dept. TECHNION
Haifa ISRAELHaifa ISRAEL
Q1, ω1 Q2, ω2
1 1Q
Non-LinearGain
satV iVrV
BPF
nsV
nsV
2112 Non-Linear
Gain
satViV
rV
Delay Line
Delay Line
2
BPF
2Q
tx2
12 n
tx1
General ConceptGeneral Concept
Delay Line
nsV Non-LinearGain
tx
injVsatV iV
rV
0
BPF
Q
Single oscillatorSingle oscillator Interlocked oscillatorsInterlocked oscillators
Fundamental LockingFundamental Locking First formulated by R. Adler (1946)First formulated by R. Adler (1946)
Principal locking criteriaPrincipal locking criteria
Given a master oscillator,Given a master oscillator, coupled uni- coupled uni-
directionally to a slave oscillator directionally to a slave oscillator
withwith
Locking takes place within the locking rangeLocking takes place within the locking range
Harmonic LockingHarmonic Locking
Two possible configurationsTwo possible configurations Sub-harmonic injection locking :Sub-harmonic injection locking : Super-harmonic injection locking :Super-harmonic injection locking :
ConsequencesConsequences Injected signal does not satisfyInjected signal does not satisfy Lifetime is very short inside the oscillating loopLifetime is very short inside the oscillating loop Dynamics of the loop can not be alteredDynamics of the loop can not be altered
Locking requires mediation by a non-linearityLocking requires mediation by a non-linearity
Harmonics generation –Harmonics generation –
Mixing with harmonicsMixing with harmonics and and
creates a component at which locks the creates a component at which locks the slave oscillatorslave oscillator
Harmonic LockingHarmonic Locking
Unidirectional LockingUnidirectional Locking
Improved signal qualityImproved signal quality Superharmonic IL – further improvementSuperharmonic IL – further improvement
or or Synchronization – Timing extractionSynchronization – Timing extraction Harmonic IL – Multirate timing extractionHarmonic IL – Multirate timing extraction
33rdrd harmonics IL harmonics IL: : 11stst harmonics IL harmonics IL: :
Unidirectional Coupling Multi Rate Unidirectional Coupling Multi Rate Timing ExtractionTiming Extraction
Transmitter
Detector andAmplifier
Clock RecoveryRe-Timing
DecisionRe-Shaping
Output
Reciever
Multi Rate Timing ExtractionMulti Rate Timing Extraction
10 20 30 40
BV
Bias-T
Bias-T
CV
DirectionalCoupler
0
BPF
Photo-HBT
Frequency GHz
RZ signal or
optically processed NRZ
signal
GHz100
Extracted electrical clock
Lasri et. al 2002Lasri et. al 2002
Modulated RZ signal toward the photo – HBT based oscillator
Transmitter SchematicTransmitter Schematic
10 Gb/s – 40 Gb/sMultiplexer
Mod.
Data OutPhase shifter
DBR
~
Pulse compression
BERTransmitter
(231-1 @ 10 Gb/s)
40 Gbit/s
10 Gbit/s10 GHz
1010 Gb/s and 40 Gb/s modulated RZ signalsGb/s and 40 Gb/s modulated RZ signals
Lasri et. al 2002Lasri et. al 2002
BV
Bias-T
Bia
s-T CV
DirectionalCoupler
Photo-HBT
0
BPF
Agilent PSA E4446A
DirectionalCoupler
CouplerVariable
Attenuator
IncomingRZ stream
ReceiverBERReceiver
DataIn
ClockIn
Recovered ClockRecovered Clock
Clock recovery of RZ data by direct Clock recovery of RZ data by direct optical IL of Photo-HBT based oscillatoroptical IL of Photo-HBT based oscillator
GHzorGHz 40410 00 Lasri et. al 2002Lasri et. al 2002
Det
ecte
d P
ower
dB
m
9.9998 10.0004 10.0012
-70
-60
-40
-20
0 injected signal
10.0002 10.0006 10.001
Free running
signal
Injection locked signal
-70
-60
-40
-20
0
4th harmonic
signal
injected signal
Injection locked
signal
-70
-60
-50
-40
-70
-60
-50
-40
10 kHz/div
40
40
1010 GHz LockingGHz Locking
Frequency GHz
Clock Recovery ResultsClock Recovery Results
4040 GHz LockingGHz Locking
Frequency GHz
Det
ecte
d P
ower
dB
m10 kHz/div
Lasri et. al 2002Lasri et. al 2002
-26 -25 -24 -23 -22 -21 -20 -19 -18
-9
-7
-5
-3
-1
Optical Power dBm
Log
( B
ER
)Direct Clock
Recovered Clock
BER performance for 10 BER performance for 10 GHzGHz Locking Locking
Coupled oscillators :Coupled oscillators : Injections strength is inversely relative to the quality factorInjections strength is inversely relative to the quality factor
Active mode-locking of fiber/diode lasers :Active mode-locking of fiber/diode lasers : Clark et al. ( NRL Labs ) : Clark et al. ( NRL Labs ) : Ng et al. ( HRL Labs ) : Ng et al. ( HRL Labs ) : Jiang et al. ( MIT ) :Jiang et al. ( MIT ) :
In all cases, ultra low phase-noise microwave source employedIn all cases, ultra low phase-noise microwave source employed Self starting approach – Coupled OEO’s ( Yao and Maleki ) :Self starting approach – Coupled OEO’s ( Yao and Maleki ) :
Harmonic spectral analysis (van der Linde technique):Harmonic spectral analysis (van der Linde technique):
0 1 2 3 4 5Harmonic number
Pow
er s
pect
rum 22
0222 nJAn
Amplitude noise contribution
Jitter contribution
high
low
f
f
xnx dfnffS )( 02,
-80
-60
-40
-20
0
10-50 GHz5 kHz/div
Pow
er d
Bm
1
5
Harmonic
number
Open loopOpen loop
Pow
er d
Bm
-80
-60
-40
-20
0
10-50 GHz5 kHz/div
Closed loopClosed loop
1
5
Harmonic
number
Lasri et. al 2002Lasri et. al 2002
Jitter MeasurementsJitter Measurements
10 10 10 10 102 3 4 5 6
-120
-100
-80
-60
1
4
Harmonic
number
Closed Loop
0 1 2 3 4 50
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Harmonic Number
RM
S N
oise
mW
100 Hz – 1 MHz
500 Hz – 1 MHz
500 Hz – 15 kHzCurve fit to 2
202 naan
Frequency range
Amplitude noise
RMS Jitter
500 Hz – 15 kHz 500 Hz –1 MHz 100 Hz –1 MHz
0.1 % 0.15 % 0.2 %
40 fS 43 fS 57 fS
Note that the 40 fs jitter (with a power of – 6 dBm and 10 km fiber) could not be improved with higher powers or longer fibers.
Pha
se N
oise
dBc
Hz
Offset Frequency Hz
Lasri et. al 2002Lasri et. al 2002
Jitter MeasurementsJitter Measurements
ConclusionConclusion Photo HBT based oscillator – versatile multi functional Photo HBT based oscillator – versatile multi functional
systemsystem Accurate numerical modelAccurate numerical model Fundamental and Harmonic injection lockingFundamental and Harmonic injection locking Uni and bi-directional locking Uni and bi-directional locking Improved noise performance due to correlated noise Improved noise performance due to correlated noise
interaction in Harmonically locked oscillatorsinteraction in Harmonically locked oscillators Multi rate timing extractionMulti rate timing extraction Bi-directional locking – characteristics determinedBi-directional locking – characteristics determined
by mutual locking efficiency and relevant Q factorsby mutual locking efficiency and relevant Q factors Self starting low jitter mode locked diode laserSelf starting low jitter mode locked diode laser
The locking mechanismThe locking mechanism
Injected signal Injected signal xx1 1 ((tt)) saturates the gain saturates the gain
Loop lifetime is long Loop lifetime is long
Free running dynamics are overwritten by Free running dynamics are overwritten by
Phenomenological modelPhenomenological model Self starting from noiseSelf starting from noise Easy injection modelingEasy injection modeling Polynomial Non-Linear Gain Polynomial Non-Linear Gain
functionfunction BPF implemented as IIR filterBPF implemented as IIR filter
Delay Line
nsV Non-LinearGain
tx
injVsatV iV
rV
0
BPF
Q
Time domain simulationTime domain simulation Transmission line – like propagationTransmission line – like propagation Decimation in time incorporating long FIR filterDecimation in time incorporating long FIR filter Ensemble averaged PSDEnsemble averaged PSD
Numerical Results – Single OscillatorNumerical Results – Single Oscillator
Noise parameter Noise parameter cc derived for derived for Resulting PSDs agree perfectlyResulting PSDs agree perfectly PSD has a single pole functional formPSD has a single pole functional form
Indicates Gaussian statisticsIndicates Gaussian statistics CAN NOT be predicted by small signal analysisCAN NOT be predicted by small signal analysis