Photonic analog-to-digital conversion with electronic-photonic integrated circuits

Abstract

Photonic Analog-to-Digital Conversion (ADC) has a long history. The premise is that the superior noise performance of femtosecond lasers working at optical frequencies enables us to overcome the bottleneck set by jitter and bandwidth of electronic systems and components. We discuss and demonstrate strategies and devices that enable the implementation of photonic ADC systems with emerging electronic-photonic integrated circuits based on silicon photonics. Devices include 2-GHz repetition rate low noise femtosecond fiber lasers, Si-Modulators with up to 20 GHz modulation speed, 20 channel SiN-filter banks, and Ge-photodetectors. Results towards a 40GSa/sec sampling system with 8bits resolution are presented.

CMOS-Compatible Wideband Silicon Modulator

“…This type of output-coupler provides low loss, broadband functionality, and two complementary outputs (channels 1 and 2) from the modulator. The two complementary outputs can be used in analog applications to linearize the transfer function of the modulator and compensate for fluctuations external to the modulator [3,4]. To provide efficient coupling on and off the wafer, reverse taper couplers combined with lower index oxynitride waveguides [5] are used.…”

High speed analog-to-digital conversion with silicon photonics

“…In this paper, we demonstrate photonic technologies, such as femtosecond lasers, optical integration and multiplexing enabling the miniaturization of high repetition rate mode-locked lasers, electro-optic conversion, filter and detector technologies that can be combined to overcome the electronic bottleneck in ADC [2,3,4,5]. Femtosecond lasers provide a stream of sampling pulses with much reduced timing jitter, when compared to integrated microwave oscillators, approaching attosecond jitter levels over milliseconds of measurement time [6].…”

“…Femtosecond lasers provide a stream of sampling pulses with much reduced timing jitter, when compared to integrated microwave oscillators, approaching attosecond jitter levels over milliseconds of measurement time [6]. The approach taken here towards a photonic ADC is based on wavelength division multiplexing to parallelize and demultiplex the stream of sampling pulses into lower rate channels, that can then be digitized with conventional electronic ADCs [5]. Although microwave sources with much better timing jitter performance than 70 fs exist, those sources are typically bulky, because of the necessary high quality microwave cavities involved, which makes them difficult to integrate in a sampling system.…”

“…3 and is based on wavelength-demultiplexing to down scale the overall sampling rate to parallel channels operating at lower rates [5]. A low-jitter pulse train with repetition rate f R generated by a mode-locked laser passes through a dispersive fiber, such that there is continuous coverage of the time axis.…”

CMOS-compatible dual-output silicon modulator for analog signal processing

“…There are additional considerations for the design of a modulator which may depend on the application. For analog applications, a modulator with two complementary outputs can be used to linearize the transfer function of the modulator and compensate for fluctuations external to the modulator [7,8], such as variations in the laser output. The design described here uses a balanced Mach-Zehnder interferometer with broadband 3 dB couplers.…”