Microwave Photonics Applications of Stimulated Brillouin Scattering Dr. Avi Zadok, School of Engineering, Bar-Ilan University Together with: Prof. Moshe Tur, Prof. Avishay Eyal, Dr. Oded Raz, Elad Zilka, and Yair Peled, School of Electrical Engineering, Tel-Aviv University

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 2 Outline  Broadband Stimulated Brillouin Scattering Processes in Optical Fibers  Variable (“slow light”) group delay of waveforms Data pulses Data pulses Analog, radar waveforms Analog, radar waveforms  Single-sideband modulation format  Ultra-wideband noise-based transmission

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 3 Stimulated Brillouin Scattering Strict phase matching conditions:  p -  s =   B (~2  11 GHz)

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 4 Characteristics of SBS  Low threshold in standard fibers (few mW)  Simple and robust  Detrimental effect in optical communication: restricts the transmitted power  Gain coefficient is of Lorenzian lineshape:  Ultra-narrow linewidth for CW pump: ~ 30 MHz only!  Objective: utilize SBS for all-optical signal processing

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 5 SBS with Broadened Pump

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 6 SBS with Broadened Pump  Broadened Pump: Magnitude gain is proportional to the pump spectrum  Phase response related to the magnitude gain through the Kramers – Kronig Relations:  Calculation of SBS response for arbitrary pump

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 7 Pump Broadening Via Direct Modulation Shalom et. al, JQE, Vol. 34 pp , 1998 Thermal chirp Adiabatic chirp

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 8 Pump spectrum measurement SimulationHeterodyne measurement Synthesized pump Modulation:

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 9 “Slow Light”  Optically-controlled, variable group delay  Sharp phase delay variations, often associated with narrow-band gain / absorption  Control through non-linear interactions Spectral gainSpectral phase delay

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 10 Pump spectrum synthesis  Sharp spectral edges of pump spectrum: enhancement of delay–bandwidth product.

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 11 Measurement of SBS gain and phase response Loayssa et. al, IEE Proc. Optoelectron., Vol. 148 pp , 2001

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 12 SBS Slow and Fast Light  SBS amplification accompanied by steep gradients of the signal phase as a function of frequency – group delay

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 13 Delay of Isolated Pulses  SBS amplification accompanied by steep gradients of the signal phase as a function of frequency – group delay A. Zadok et al., Opt. Express 14, 8498, 2006

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 14 Delay of 5Gb/s PRBS Output NRZ eye diagram: Synthesized modulation, 22dBm, 120ps delay First demonstration of high-rate PRBS delay using SBS BER for 80, 100, 120ps delay: <10 -9, 10 -8, 4  Zadok et. al, Opt. Express, Vol. 14 pp , 2006

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 15 5Gb/s PRBS: Delay Enhancement Synthesized pump modulation: 25-40% longer delays Synthesized Mod. Random Mod.

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 16 True Time Delay (TTD) in phased array antennas True Time Delay DDDDDDDD  Beam-stirring using variable delay between elements  Large bandwidth: group delay instead of phase delay  Low distortion necessary

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 17 LFM “impulse response” metrics PSL Main lobe width ~ 1/B

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 18 Delay of LFM signals 20km DSF 3.5km HNLF: ‘+’: VNA ‘  ’: LFM Zadok et. al, IEEE PTL, Vol. 19, pp , GHz system: ~ 10 elements, 90°

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 19 Measured impulse response Pump power: 20dBm Width broad: <1% PSL: < -26dB ISLR: > 21dB Delay: 230ps

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 20 SSB modulation - noise Heterodyne spectral measurement of LFM-modulated signal: One side band amplified by SBS. No harmonics. NF ~ 150*. Pump off Pump on Pump 20dBm Noise *: Olsson et. al, JLT, Vol. 5 pp , 1987 A. Zadok et al. J. Lightwave Technol. 25, (2007)

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 21 Impulse response of SSB modulated LFM signal

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 22 Ultra-wideband waveform generation  UWB impulse radio: several GHz-wide, no sine-wave carriers, low power spectral density  Applications: indoor wireless communication, imaging systems, vehicular radar systems.

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 23 UWB noise-based communication  Slow-rate modulation of broadband noise with carefully controlled power spectral density  Alternative to tailored, short pulses.

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 24 Experimental results Brillouin pump spectrum: Generated noise spectrum:  1.1 GHz bandwidth Y. Peled, M. Tur and A. Zadok, Paper NTuC16, Nonlinear Photonics 2010

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 25 Experimental results Cntd. 8 Mb/s transmission (no reference) Correlation properties  Q = 10 Y. Peled, M. Tur and A. Zadok, Paper NTuC16, Nonlinear Photonics 2010

BIU – UV workshop, 13-14/4/2010 Dr. Avi Zadok 26 Experimental results Cntd. 4 Mb/s transmission (with reference) Decoded waveform  Q = 5 Y. Peled, M. Tur and A. Zadok, Paper NTuC16, Nonlinear Photonics 2010