Optically sampled analog-to-digital converters

Abstract

Optically sampled analog-to-digital converters (ADCs) combine optical sampling with electronic quantization to enhance the performance of electronic ADCs. In this paper, we review the prior and current work in this field, and then describe our efforts to develop and extend the bandwidth of a linearized sampling technique referred to as phase-encoded optical sampling. The technique uses a dual-output electrooptic sampling transducer to achieve both high linearity and 60-dB suppression of laser amplitude noise. The bandwidth of the technique is extended by optically distributing the post-sampling pulses to an array of time-interleaved electronic quantizers. We report on the performance of a 505-MS/s (megasample per second) optically sampled ADC that includes high-extinction LiNbO 3 1-to-8 optical time-division demultiplexers. Initial characterization of the 505-MS/s system reveals a maximum signal-to-noise ratio of 51 dB (8.2 bits) and a spur-free dynamic range of 61 dB. The performance of the present system is limited by electronic quantizer noise, photodiode saturation, and preliminary calibration procedures. None of these fundamentally limit this sampling approach, which should enable multigigahertz converters with 12-b resolution. A signal-to-noise analysis of the phase-encoded sampling technique shows good agreement with measured data from the 505-MS/s system.

Attosecond‐precision ultrafast photonics

“…After sampling, the encoded pulses are demultiplexed into multiple parallel lower-rate streams, either by time-division multiplexing (TDM) [113] or by wavelength-division multiplexing (WDM) [114]. A fully operating photonic ADC with 9.8 ENOB at 505 MSamples/s was demonstrated using the TDM approach [113]. We are currently pursuing a 20-channel WDM-based timeinterleaving ADC with a targeted performance of 40 GSamples/s and 8-bit resolution.…”

“…The timeinterleaving techniques use a stream of optical pulses or chirped optical pulses for the electro-optic sampling of electronic signals. After sampling, the encoded pulses are demultiplexed into multiple parallel lower-rate streams, either by time-division multiplexing (TDM) [113] or by wavelength-division multiplexing (WDM) [114]. A fully operating photonic ADC with 9.8 ENOB at 505 MSamples/s was demonstrated using the TDM approach [113].…”

“…Among many different approaches in photonic ADCs [107], two standard architectures for higher sampling rates have been established: (a) the time-stretching technique [111,112] and (b) the time-interleaving technique [113,114]. The time-stretching technique uses a spectrally chirped optical pulse as a means for temporal magnification of a segment of an electronic signal to be sampled.…”

Integrated Coherent Receivers for High-Linearity Microwave Photonic Links

“…The delayed limited bandwidth of the loop is 4 GHz. In order to port the link to a much higher carrier frequency, we are exploring the idea of optical sampling [17]- [21]. Additionally, the PLL bandwidth of 1.45 GHz demonstrated here would be sufficiently large to track the phase noise of standard semiconductor lasers with low phase error.…”

An Optical-Electrical Sub-Sampling Receiver Employing Continuous-Time ΔΣ Modulation

“…OPTICAL-ELECTRICAL CONTINUOUS-TIME ARCHITECTURE A photodiode converts the optical information (photons) into electrical information (charge), and the question now becomes how to efficiently digitize this information. Previous implementations of optical-electrical ADC's [6,9,10] adopted what can best be described as a charge compartmentalization approach (see Fig. 4a).…”