Publications (4)6.8 Total impact
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Article: Compressive sensing of sparse radio frequency signals using optical mixing.
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ABSTRACT: We demonstrate an optical mixing system for measuring properties of sparse radio frequency (RF) signals using compressive sensing (CS). Two types of sparse RF signals are investigated: (1) a signal that consists of a few 0.4 ns pulses in a 26.8 ns window and (2) a signal that consists of a few sinusoids at different frequencies. The RF is modulated onto the intensity of a repetitively pulsed, wavelength-chirped optical field, and time-wavelength-space mapping is used to map the optical field onto a 118-pixel, one-dimensional spatial light modulator (SLM). The SLM pixels are programmed with a pseudo-random bit sequence (PRBS) to form one row of the CS measurement matrix, and the optical throughput is integrated with a photodiode to obtain one value of the CS measurement vector. Then the PRBS is changed to form the second row of the mixing matrix and a second value of the measurement vector is obtained. This process is performed 118 times so that we can vary the dimensions of the CS measurement matrix from 1×118 to 118×118 (square). We use the penalized ℓ<sub>1</sub> norm method with stopping parameter λ (also called basis pursuit denoising) to recover pulsed or sinusoidal RF signals as a function of the small dimension of the measurement matrix and stopping parameter. For a square matrix, we also find that penalized ℓ<sub>1</sub> norm recovery performs better than conventional recovery using matrix inversion.Optics Letters 11/2012; 37(22):4675-7. · 3.40 Impact Factor -
Article: Phase ripple correction: theory and application.
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ABSTRACT: Spectral phase ripple associated with novel dispersive devices can distort broadband optical signals. We present a digital postprocessing algorithm to correct for this distortion by exploiting the static deterministic nature of the ripple. This algorithm is demonstrated with empirical data for several systems employing chirped fiber Bragg gratings (CFBGs). We employ this technique in a photonic time-stretch system incorporating CFBGs, improving the signal fidelity by 9 dB. Simulations and experiments show that this algorithm, which can be reduced to a simple interpolation and matrix multiplication, also mitigates additive noise. We see that the act of distortion correction yields signal fidelity superior to that of an ideal dispersive element.Optics Letters 06/2008; 33(10):1108-10. · 3.40 Impact Factor -
Article: Photonic bandwidth compression front end for digital oscilloscopes
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ABSTRACT: Time-stretch photonic analog-to-digital converter technology is used to make an optical front-end that compresses RF bandwidth before input to a digital oscilloscope. To operate a time-stretch ADC in a continuous-time mode for bandwidth compression, the optical signal on which the RF is modulated must be segmented and demultiplexed. We demonstrate both a spectral and a temporal method for overlapping the channels. Using the temporal method we obtain a compression ratio of 3 with 4 channels. Mating this optical front end with a state-of-the-art 4-channel digital oscilloscope with an input bandwidth of 16 GHz and a sampling rate of 50 GS/s gives a digitizer with 150 GS/s and an input bandwidth of 48 GHz. We digitize RF signals up to 45 GHz and obtain effective number of bits (ENOB) ~ 2.8 with single channels and ~2.5 with multiple channels, both measured over the 48 GHz instantaneous bandwidth of our system. Index Terms— Microwave photonics, optical signal processing, optical modulation, photonic assisted ADC, optical analog link, A/D conversion, photonic time stretch. -
Article: Bandwidth compression optical processor using chirped fiber Bragg gratings
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ABSTRACT: Chirped fiber Bragg gratings are used as low-loss, dispersion compensation modules for telecommunications applications. Here we use them to make an optical processor that compresses the bandwidth of electronic signals before digitization by an analog-to-digital converter. OCIS codes: (230.0250) Optoelectronics, (060.2360) Fiber optics and optical communications :Fiber optics links and subsystems.
