Next Generation Networking Systems Laboratory
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OPTICAL ARBITRARY WAVEFORM GENERATION ($9.5M DARPA OAWG project: with MIT, Multiplex, KTH, Inphi, and Inplane)

Extending upon the O-CDMA concept, it is possible to achieve ultra-high capacity all-optical arbitrary waveform generation covering an optical bandwidth of ~100 THz. Possible applications include ultra-wideband secure communications in phase and amplitude modulation, optical signal synthesis, ultra-high resolution remote sensing and LADARs. The new $9.5 M project awarded to MIT and UCDavis pursues ultrahigh capacity and precision optical arbitrary waveform generation. Fig 1 shows the schematic. Starting with a high-precision optical comb generator from MIT producing accurate optical comb lines from a stabilized mode locked laser, the optical arbitrary waveform generation encoder from UC Davis will modulate the phase and amplitude of each comb line. The modulation bandwidth of the phase and amplitude modulations will be equal to the comb spacing so that the arbitrary waveform generation covering the entire optical spectrum is possible. The optical arbitrary waveform generation device includes monolithically integrated amplitude and phase modulators and arrayed waveguide gratings. Fig 2 shows a layout with 32 channel * 40 GHz spacing for 1.28 THz optical arbitrary waveform generation on a monolithically integrated InP device. Efficient high-speed modulations on each spectral element on the InP waveguide requires careful RF-photonic design of phase and amplitude modulators with velocity and impedance matching. Future devices will include photonic crystal based optical comb generators and optical arbitrary waveform generators. Edit

Optical Arbitrary Waveform Generation Methods

Simply put, optical arbitrary waveform generation (OAWG) would be the generation of any optical waveform with a certain bandwidth without any other constraints. Several schemes exist to generate arbitrary waveforms. Those include direct time-domain modulation, Fourier domain synthesis, and a hybrid approach combining the time and frequency domain.
150 GHz Repetitive OAWG. Quadratic spectral phase waveform (a) Spectrum (b) Time-Domain (c) X-FROG (1)  Trace. Transform limited phase waveform (c) Spectrum (d) Time-Domain (e)X-FROG Trace (1) .

150 GHz Repetitive OAWG. Quadratic spectral phase waveform (a) Spectrum (b) Time-Domain (c) X-FROG(1) Trace. Transform limited phase waveform (c) Spectrum (d) Time-Domain (e)X-FROG Trace(1).

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10, 20, 40 GHz OAWG using Silica AWGs

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Publications

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1. XFROG

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