Time interleaved optical sampling for ultra-high speed A/D conversion

Abstract

A scheme is proposed for increasing the sampling rate of analogue-to-digital conversion by more than an order of magnitude by combining state-of-the-art A/D converters with photonic technology. Ultra-high speed sampling is performed optically by a multiwavelength pulse train. Wavelength demultiplexers convert the high repetition rate data stream of samples into parallel data streams that can be handled by available electronic A/D converters.

Photonic ADC: overcoming the bottleneck of electronic jitter

“…Wavelengthdemultiplexing scheme was proposed by Frankel et al [24], preceded by a work of Valdmanis, who discussed a similar concept to improve time resolution of oscilloscopes [23]. Wavelength-demultiplexing based on discrete time-to-wavelength mapping -the approach adopted in this work -was proposed by Yariv [21] and Kang [22]. A time-demultiplexing approach [26] was adopted by Juodawlkis et al [27], who analyzed the performance of optically-demultiplexed ADCs and developed calibration techniques which helped to demonstrate 9.8 ENOB for a 733 MHz signal sampled at 505 MSa/s in an 8-channel system in a work by Williamson et al [28].…”

“…This operation establishes a discrete time-to-wavelength mapping within the pulse train, i.e. pulses separated in time are also separated in wavelength [21,22]. A continuous version of time-to-wavelength mapping can be established with a dispersive fiber [23,24].…”

Silicon photonics devices for integrated analog signal processing and sampling

“…To avoid this limitation, a mode locked-laser is used to sample a signal with much lower jitter than most electronic timing sources. In addition, a wavelength division multiplexing method, as done by Yariv [50] and Kang [51], is used to divide the sampled signals among multiple electronic ADCs to sample the signal at a slower rate. Figure 14 schematically shows the method used for the optical sampling.…”

Progress in Photonic Analog-to-Digital Conversion

“…A mode-locked laser, that may or may not be integrated, generates an ultra-low-jitter optical pulse train with repetition period T. This train is split into N trains at different center wavelengths with a wavelength demultiplexer, which are passed through a set of delay lines which introduce incremental time delays of T/N between them. The trains are then recombined into a single path, forming a train of pulses at N-fold primary repetition rate and chirped center wavelength repeating periodically every N pulses [15,16]. This pulse train passes an electrooptic modulator with the RF signal to be sampled applied to its input; at the output, the energies of the modulated pulses represent the samples of the RF signal taken at the corresponding sampling times.…”

“…In the photonic approach, the problem of aperture jitter is addressed by sampling the RF signal optically with ultra-stable pulse trains available from mode-locked lasers; the timing jitter of such pulse trains can approach few attoseconds [9][10][11][12], which is over four orders of magnitude less than the jitter in state-of-the-art electronic ADCs [8]. The second challengecomparator ambiguity -is completely eliminated by separating the fast RF signal into multiple slower channels, using a time- [13] or a wavelength-demultiplexing [14][15][16] scheme. With the photonic time-stretch approach [17], the bandwidth of the time-division multiplexed channels is reduced, enabling sampling rates as high as 10 TSa/s [18].…”