Abstract
Integrated optical sigma-delta (??) analog-to-digital converters (ADCs) use a pulsed laser to oversample an input signal at two Mach-Zehnder interferometers. A fiber-lattice accumulator is embedded within a feedback loop around a single-bit quantizer to spectrally shape the quantization noise to fall outside the signal band of interest. Decimation filtering is applied to the quantizer output to construct the input signal with high resolution. Applications of integrated optical ?? ADCs include digitizing wideband radio-frequency signals directly at an antenna (digital antenna). In this paper, a novel fiber-lattice accumulator design is presented, and a coherent simulation of an integrated optical first-order, single-bit ?? ADC is reported. The accumulator leakage resulting from a mismatch in the optical circuit parameters is quantified. A time-domain analysis is presented, and the simulation results from an all-electronic ?? ADC are presented for comparison. A frequency-domain analysis of a ten times oversampling (n = 4 bits) simulation is used to compare the dynamic performance parameters, including the spurious-free dynamic range, signal-to-noise-plus-distortion ratio, and effective number of bits. The formation of image frequencies when the accumulator is overloaded (i.e., the optical amplifier gain is too large) is also investigated.
Published Version
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