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Injection Locked Oscillators Optoelectronic Applications

Injection Locked Oscillators Optoelectronic Applications. Q 1, ω 1. Q 2 , ω 2. E. Shumakher, J. Lasri, B. Sheinman, G. Eisenstein, D. Ritter Electrical Engineering Dept. TECHNION Haifa ISRAEL. General Concept. Single oscillator. Interlocked oscillators. Fundamental Locking.

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Injection Locked Oscillators Optoelectronic Applications

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  1. Injection Locked Oscillators Optoelectronic Applications Q1, ω1 Q2, ω2 E. Shumakher, J. Lasri, B. Sheinman, G. Eisenstein, D. Ritter Electrical Engineering Dept. TECHNION Haifa ISRAEL

  2. General Concept Single oscillator Interlocked oscillators

  3. Fundamental Locking First formulated by R. Adler (1946) Principal locking criteria Given a master oscillator, coupled uni- directionally to a slave oscillator with Locking takes place within the locking range

  4. Harmonic Locking • Two possible configurations • Sub-harmonic injection locking : • Super-harmonic injection locking : • Consequences • Injected signal does not satisfy • Lifetime is very short inside the oscillating loop • Dynamics of the loop can not be altered

  5. Harmonic Locking Locking requires mediation by a non-linearity • Harmonics generation – • Mixing with harmonics and creates a component at which locks the slave oscillator

  6. Unidirectional Locking • Improved signal quality • Superharmonic IL – further improvement • or • Synchronization – Timing extraction • Harmonic IL – Multirate timing extraction

  7. dBc Hz Phase Noise 3rd Harmonic Unidirectional Locking -20 1stQ2 free • Coupled oscillators : • 1st harmonic of Q2 exhibits a lower noise than the 1st harmonic of the higher quality injected signal by • Explainable through correlated noise considerations 3rdQ2 free -40 1stQ2 locked 3rdQ2 locked 1stQ1 -60 -80 -100 -120 2 3 4 5 6 7 10 10 10 10 10 10 Offset Frequency Hz

  8. 3rd Harmonic Unidirectional Locking 1st harmonics of Q1 at Correlated signals Initially uncorrelated signals Signals turn into correlated 1st – 4th harmonics of Q2 at ω2

  9. -40 1st harmonics IL : 3rd harmonics IL : -60 -80 -100 -120 -140 2 3 4 5 6 10 10 10 10 10 dBc Hz Phase Noise Unidirectional Coupling Experiment • Injected frequency is followed by the corresponding harmonics 1stQ2 free 1stQ1 injected 1stQ2 locked 3rdQ2 locked Offset Frequency Hz

  10. Unidirectional Coupling Multi Rate Timing Extraction

  11. Multi Rate Timing Extraction Extracted electrical clock Frequency GHz RZ signal or optically processed NRZ signal Lasri et. al 2002

  12. 10 Gb/s and 40 Gb/s modulated RZ signals Pulse compression Mod. ~ Transmitter Schematic 10 Gb/s – 40 Gb/s Multiplexer DBR 40 Gbit/s 10 Gbit/s 10 GHz BER Transmitter Data Out Phase shifter Modulated RZ signal toward the photo – HBT based oscillator (231-1 @ 10 Gb/s) Lasri et. al 2002

  13. Clock recovery of RZ data by direct optical IL of Photo-HBT based oscillator Recovered Clock Lasri et. al 2002

  14. -40 -40 -50 -50 0 0 -60 -60 -20 -20 -70 -70 -40 -40 -60 -60 -70 -70 Clock Recovery Results 10 GHz Locking 40 GHz Locking injected signal injected signal 4th harmonic signal Free running signal 10 kHz/div 40 9.9998 10.0004 10.0012 Detected Power dBm Detected Power dBm Injection locked signal Injection locked signal 10 kHz/div 10.0002 10.0006 10.001 40 Frequency GHz Frequency GHz Lasri et. al 2002

  15. -26 -25 -24 -23 -22 -21 -20 -19 -18 BER performance for 10 GHz Locking Direct Clock -1 Recovered Clock -3 -5 Log ( BER ) -7 -9 Optical Power dBm Lasri et. al 2002

  16. Coupled oscillators : Injections strength is inversely relative to the quality factor 3rd Harmonic Bidirectional Locking Generalized Van der Pol

  17. -65 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 1stQ1 free 3rdQ1 free -70 1stQ2 free -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 1stQ1 lock 3rdQ2 free -75 3rdQ1 lock -60 -60 -60 -60 -60 -60 -60 -60 -60 -60 -60 1stQ2 lock -80 3rdQ2 lock free -80 -80 -80 -80 -80 -80 -80 -80 -80 -80 -80 -85 -90 -100 -100 -100 -100 -100 -100 -100 -100 -100 -100 -100 -95 -120 -120 -120 -120 -120 -120 -120 -120 -120 -120 -120 0.1 1 10 100 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 7 7 7 7 7 7 7 7 7 7 7 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 dBc Hz Phase Noise 3rd Harmonic Bidirectional Locking Phase noise at offset Power Spectral Density 1stQ2 free 10:1 25:1 7:1 5:1 2:1 1stQ1 free 1:1.5 2:1 1.5:1 10:1 1:1 25:1 1:5 5:1 7:1 1:2 1.5:1 1:1.5 1:5 1:1 1:2 Injection Ratio P2 / P1 Offset Frequency Hz

  18. Bidirectional CouplingExperimental Setup

  19. -20 1st harmonics IL : 3rd harmonics IL : -40 -60 -80 -100 -120 -140 2 3 4 5 6 10 10 10 10 10 2 3 4 5 6 10 10 10 10 10 dBc Hz Phase Noise Bidirectional CouplingExperimental Results 1stQ2 free 1stQ2 free 1stQ1 free 1stQ1 free 1stQ2 locked 1stQ2 locked 3rdQ2 locked 3rdQ2 locked 1stQ1 locked 1stQ1 locked Offset Frequency Hz Offset Frequency Hz

  20. Ultra Low Jitter Pulse Sources • Active mode-locking of fiber/diode lasers : • Clark et al. ( NRL Labs ) : • Ng et al. ( HRL Labs ) : • Jiang et al. ( MIT ) : • In all cases, ultra low phase-noise microwave source employed • Self starting approach – Coupled OEO’s ( Yao and Maleki ) :

  21. Self-Starting Ultra Low Jitter Optical Pulse Source 10 GHz RF signal 10 GHz optical pulse-train • Actively mode-locked diode laser • Photo-HBT based oscillator • Extended cavity optoelectronic oscillator Lasri et. al 2002

  22. Bidirectional Coupling Pulse Source Experimental Setup

  23. -40 -60 -80 -100 -120 3 4 5 6 10 10 10 10 2 10 dBc Hz Phase Noise Bidirectional Coupling Pulsed SourceExperimental Results • Pulsed Source • Mode locked diode laser • Modulated at it’s 6th harmonics ( ) • Driven by 3rd harmonics of the EO ( ) • Repetition rate • Resulting locked signal has better phase noise then the free running OEO Electrical Signal 1stQ2 free 1stQ1 free 1stQ2 locked 3rdQ2 locked -140 Offset Frequency Hz

  24. 0.35 -5 -15 0.25 -25 0.15 -35 -45 0.05 -55 -65 0.35 -75 0.25 -85 0.15 0.05 Self-Starting Ultra Low Jitter Optical Pulse Source Electrical 10 GHz signal Optical Spectrum Open Loop Power mW Open loop Power dBm Closed loop 1542.5 1543 1543.5 1544 1544.5 Wavelength nm Closed Loop DtDn ~ 0.47 10 GHz 5 kHz/div Power mW Phase noise at 10 kHz offset: Open loop: -98 dBc/Hz Close loop: -108 dBc/Hz 1544.5 1542.5 1543 1543.5 1544 Wavelength nm

  25. Power spectrum 1 0 2 3 4 5 Harmonic number Lasri et. al 2002 Jitter Measurements Harmonic spectral analysis (van der Linde technique): Amplitude noise contribution Jitter contribution 0 0 Open loop Closed loop -20 -20 Harmonic number Harmonic number Power dBm Power dBm -40 -40 5 5 -60 -60 1 1 -80 -80 10-50 GHz 10-50 GHz 5 kHz/div 5 kHz/div

  26. 0.35 -60 0.3 -80 0.25 0.2 -100 0.15 0.1 -120 0.05 0 5 0 1 2 3 4 Frequency range 500 Hz – 15 kHz 500 Hz –1 MHz 100 Hz –1 MHz dBc Hz 6 2 3 4 5 10 10 10 10 10 Amplitude noise 0.15 % 0.2 % 0.1 % Phase Noise RMS Jitter 57 fS 43 fS 40 fS Lasri et. al 2002 Jitter Measurements Closed Loop 100 Hz – 1 MHz 500 Hz – 1 MHz 500 Hz – 15 kHz Curve fit to RMS Noise mW Harmonic number 4 1 Harmonic Number Offset Frequency Hz 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.

  27. Conclusion • Photo HBT based oscillator – versatile multi functional system • Accurate numerical model • Fundamental and Harmonic injection locking • Uni and bi-directional locking • Improved noise performance due to correlated noise interaction in Harmonically locked oscillators • Multi rate timing extraction • Bi-directional locking – characteristics determined by mutual locking efficiency and relevant Q factors • Self starting low jitter mode locked diode laser

  28. Fundamental Locking The locking mechanism • Injected signal x1 (t) saturates the gain • Loop lifetime is long • Free running dynamics are overwritten by x1 (t) for

  29. 1stQ1 free 3rdQ1 free 1stQ2 free 3rdQ2 free free -20 -20 -20 -20 -40 -40 -40 -40 -60 -60 -60 -60 -80 -80 -80 -80 1stQ1 lock 3rdQ1 lock 1stQ2 lock -100 -100 -100 -100 3rdQ2 lock -120 -120 -120 -120 2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5 6 6 6 6 7 7 7 7 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 1:2 1stQ1 lock 3rdQ1 lock 1stQ2 lock 3rdQ2 lock 1:1 1stQ1 lock 3rdQ1 lock 1stQ2 lock 3rdQ2 lock 2:1

  30. 1stQ1 lock 3rdQ1 lock 1stQ2 lock 3rdQ2 lock -20 -20 -20 -20 1:5 -40 -40 -40 -40 -60 -60 -60 -60 -80 -80 -80 -80 -100 -100 -100 -100 -120 -120 -120 -120 2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5 6 6 6 6 7 7 7 7 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 1stQ1 lock 3rdQ1 lock 1stQ2 lock 3rdQ2 lock 5:1 1stQ1 lock 1stQ1 lock 3rdQ1 lock 3rdQ1 lock 1stQ2 lock 1stQ2 lock 3rdQ2 lock 3rdQ2 lock 7:1 10:1

  31. -20 -20 -20 -40 -40 -40 -60 -60 -60 -80 -80 -80 -100 -100 -100 -120 -120 -120 2 2 2 3 3 3 4 4 4 5 5 5 6 6 6 7 7 7 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 1stQ1 lock 1stQ1 lock 3rdQ1 lock 3rdQ1 lock 1stQ2 lock 1stQ2 lock 3rdQ2 lock 3rdQ2 lock 1.5:1 1:1.5 1stQ1 lock 3rdQ1 lock 1stQ2 lock 3rdQ2 lock 25:1

  32. Feedback Model • Phenomenological model • Self starting from noise • Easy injection modeling • Polynomial Non-Linear Gain function • BPF implemented as IIR filter • Time domain simulation • Transmission line – like propagation • Decimation in time incorporating long FIR filter • Ensemble averaged PSD

  33. 8 Simulated 7 6 5 4 Analytical 3 Simulated 2 1 0 0 20 40 60 80 dBc Hz Phase Noise Numerical Results – Single Oscillator -20 1st harmonics Linear fit -30 • Noise parameter c derived for • Resulting PSDs agree perfectly • PSD has a single pole functional form • Indicates Gaussian statistics • CAN NOT be predicted by small signal analysis 2nd harmonics 3rd harmonics -40 4th harmonics -50 Period Time Variance s2 -60 -70 -80 -90 -100 2 3 4 5 6 10 10 10 10 10 Time μS Offset Frequency Hz

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