Orthogonal Full-Field Optical Sampling

Abstract

Sampling is the first step to convert analogue into digital signals and one of the basic concepts for information handling. All practical sampling systems, however, are accompanied with errors. Bandwidth-limited signals can be seen as a superposition of time-shifted sinc pulses, weighted with the sampling values. Thus, due to orthogonality, bandlimited signals can be perfectly sampled by a corresponding sinc pulse with the correct time shift. But, sinc pulses are just a mathematical construct. Sinc pulse sequences, instead, can simply be generated by a rectangular, phase-locked frequency comb. For a high repetition-time to pulsewidth ratio, or a low duty cycle, the pulses of such a sequence come close to single sinc pulses, and thus, the sampling with them might lead to an almost ideal sampling. Here, we present the full-field optical sampling with a repetition-time to pulsewidth ratio of up to 153, or a duty cycle of around 0.65%. Since it enables amplitude and phase sampling, ultrahigh sampling rates should be possible.

Nonlinearity- and dispersion- less integrated optical time magnifier based on a high-Q SiN microring resonator

“…The sampled values are the integral of the sinc pulse sequence over its repetition rate, which is again Δ f s and if a coherent receiver is used, the full field can be sampled 33 . Consequently, the amplitude and phase values can be extracted by low bandwidth photodiodes and electronics.…”

“…It can be shown that the presented convolution in the two cascaded modulators can be used to retrieve the phase of the sampling point by comparison with the phase of a local oscillator 33 . So if instead of a simple photodiode a coherent receiver will be used to integrate the sampling points, a full-field sampling can be accomplished.…”

“…With integrated 100 GHz modulators 34,38 , integrated devices with effective compressed sampling rates of 400 GSa/s are possible. Since the whole field (amplitude and phase) can be sampled 33 , much higher measurement bandwidths can be achieved by spectrum slicing 8 . Since bandwidths of 100 GHz can be characterized with standard silicon photonic CMOS compatible devices and low bandwidth electronics (12 GHz), a 100 GHz wavelength division multiplexer combined with the described method, spectrum slicing and co-integrated electronics could enable the single shot measurement of very short events with THz bandwidths in integrated, low bandwidth CMOS compatible devices.…”

Analysis of Non-Idealities in the Generation of Reconfigurable Sinc-Shaped Optical Nyquist Pulses

“…As shown mathematically [1], an unlimited sinc pulse sequence is the inter-symbol interference-free superposition of equal ideal sinc pulses. Pulse sequences can be generated by filtering the frequency comb of a mode-locked laser [7], [8], by a Nyquist laser [4], by the generation of frequency combs with parametric effects [9], [10], or by one or two coupled intensity modulators that are driven with one or multiple radio frequencies [1], [13] - [23]. Especially the last method offers the possibility for integrated Nyquist pulse sources [15], [16], [19], and [20].…”

“…Besides communications, the temporal and spectral features of the pulse sequences like multi-wavelength operation and tunable repetition rate make them suitable to be used as a sampling source in photonic analog-to-digital (ADC) and digital-to-analog conversion (DAC) [16] - [18], [21] - [23] and as sampling pulses for the demultiplexing of Nyquist optical time-division multiplexing (OTDM) signals [24].…”