Microwave Photonics Applications of Stimulated Brillouin Scattering Dr
Microwave Photonics Applications of Stimulated Brillouin Scattering Dr. Avi Zadok, School of Engineering, Bar-Ilan University +972 -3 -5318882 Together with: zadoka@eng. biu. ac. il www. eng. biu. ac. il/~zadoka/ Prof. Moshe Tur, Prof. Avishay Eyal, Dr. Oded Raz, Elad Zilka, and Yair Peled, School of Electrical Engineering, Tel-Aviv University
Outline Ø Broadband Stimulated Brillouin Scattering Processes in Optical Fibers Ø Variable (“slow light”) group delay of waveforms l Data pulses l Analog, radar waveforms Ø Single-sideband modulation format Ø Ultra-wideband noise-based transmission BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 2
Stimulated Brillouin Scattering Strict phase matching conditions: p - s = B (~2 11 GHz) BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 3
Characteristics of SBS Ø Low threshold in standard fibers (few m. W) Ø Simple and robust Ø Detrimental effect in optical communication: restricts the transmitted power Ø Gain coefficient is of Lorenzian lineshape: Ø Ultra-narrow linewidth for CW pump: ~ 30 MHz only! Ø Objective: utilize SBS for all-optical signal processing BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 4
SBS with Broadened Pump BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 5
SBS with Broadened Pump Ø Broadened Pump: Magnitude gain is proportional to the pump spectrum Ø Phase response related to the magnitude gain through the Kramers – Kronig Relations: Ø Calculation of SBS response for arbitrary pump BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 6
Pump Broadening Via Direct Modulation Adiabatic chirp Thermal chirp Shalom et. al, JQE, Vol. 34 pp. 1816 -1824, 1998 BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 7
Pump spectrum measurement Synthesized pump Modulation: Simulation Heterodyne measurement BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 8
“Slow Light” Ø Ø Ø Optically-controlled, variable group delay Sharp phase delay variations, often associated with narrow-band gain / absorption Control through non-linear interactions Spectral gain BIU – UV workshop, 13 -14/4/2010 Spectral phase delay Dr. Avi Zadok 9
Pump spectrum synthesis Ø Sharp spectral edges of pump spectrum: enhancement of delay–bandwidth product. BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 10
Measurement of SBS gain and phase response Loayssa et. al, IEE Proc. Optoelectron. , Vol. 148 pp. 143 -148, 2001 BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 11
SBS Slow and Fast Light Ø 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 12
Delay of Isolated Pulses Ø 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 13
Delay of 5 Gb/s PRBS Output NRZ eye diagram: Synthesized modulation, 22 d. Bm, 120 ps delay BER for 80, 100, 120 ps delay: <10 -9, 10 -8, 4 10 -6 First demonstration of high-rate PRBS delay using SBS Zadok et. al, Opt. Express, Vol. 14 pp. 8498 -8505, 2006 BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 14
5 Gb/s PRBS: Delay Enhancement Synthesized Mod. Random Mod. Synthesized pump modulation: 25 -40% longer delays BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 15
True Time Delay (TTD) in phased array antennas D D D D True Time Delay Ø Ø Ø 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 16
LFM “impulse response” metrics PSL BIU – UV workshop, 13 -14/4/2010 Main lobe width ~ 1/B Dr. Avi Zadok 17
Delay of LFM signals ‘+’: VNA ‘ ’: LFM 20 km DSF 3. 5 km HNLF: Zadok et. al, IEEE PTL, Vol. 19, pp. 462 -464, 2007 50 GHz system: ~ 10 elements, 90° BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 18
Measured impulse response Pump power: 20 d. Bm Width broad: <1% PSL: < -26 d. B ISLR: > 21 d. B Delay: 230 ps BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 19
SSB modulation - noise Heterodyne spectral measurement of LFM-modulated signal: One side band amplified by SBS. No harmonics. NF ~ 150*. Pump off Pump on Noise Pump 20 d. Bm *: Olsson et. al, JLT, Vol. 5 pp. 147 -153, 1987 A. Zadok et al. J. Lightwave Technol. 25, 2168 -2174 (2007) BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 20
Impulse response of SSB modulated LFM signal BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 21
Ultra-wideband waveform generation UWB impulse radio: several GHz-wide, no sine-wave carriers, low power spectral density Ø Applications: indoor wireless communication, imaging systems, vehicular radar systems. Ø BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 22
UWB noise-based communication Slow-rate modulation of broadband noise with carefully controlled power spectral density Ø Alternative to tailored, short pulses. Ø BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 23
Experimental results Brillouin pump spectrum: Ø Generated noise spectrum: 1. 1 GHz bandwidth Y. Peled, M. Tur and A. Zadok, Paper NTu. C 16, Nonlinear Photonics 2010 BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 24
Experimental results Cntd. 8 Mb/s transmission (no reference) Ø Correlation properties Q = 10 Y. Peled, M. Tur and A. Zadok, Paper NTu. C 16, Nonlinear Photonics 2010 BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 25
Experimental results Cntd. 4 Mb/s transmission (with reference) Ø Decoded waveform Q=5 Y. Peled, M. Tur and A. Zadok, Paper NTu. C 16, Nonlinear Photonics 2010 BIU – UV workshop, 13 -14/4/2010 Dr. Avi Zadok 26
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