Robust design of all-optical PSK regenerator based on phase sensitive amplification

More compact, stable, and efficient configuration of a recently-developed regenerator is presented. The regenerator is assessed at data rates up to 56 Gbit/s using white phase noise for the first time

QPSK phase and amplitude regeneration at 56 Gbaud in a novel idler-free non-degenerate phase sensitive amplifier

We introduce a novel input-idler-free non-degenerate phase sensitive amplifier (PSA) configuration and use it for simultaneous phase and amplitude regeneration of quadrature phase shift keyed (QPSK) signals demonstrated at symbol rates up to 56 Gbaud

40-Gbaud 16-QAM transmitter using tandem IQ modulators with binary driving electronic signals

We propose a novel 16-quadrature amplitude modulation (QAM) transmitter based on two cascaded IQ modulators driven by four separate binary electrical signals. The proposed 16-QAM transmitter features scalable configuration and stable performance with simple bias-control. Generation of 16-QAM signals at 40 Gbaud is experimentally demonstrated for the first time and visualized with a high speed constellation analyzer. The proposed modulator is also compared to two other schemes. We investigate the modulator bandwidth requirements and tolerance to accumulated chromatic dispersion through numerical simulations, and the minimum theoretical insertion attenuation is calculated analytically

Cortical thickness and resting-state cardiac function across the lifespan: a cross-sectional pooled mega analysis

Understanding the association between autonomic nervous system [ANS] function and brain morphology across the lifespan provides important insights into neurovisceral mechanisms underlying health and disease. Resting state ANS activity, indexed by measures of heart rate [HR] and its variability [HRV] has been associated with brain morphology, particularly cortical thickness [CT]. While findings have been mixed regarding the anatomical distribution and direction of the associations, these inconsistencies may be due to sex and age differences in HR/HRV and CT. Previous studies have been limited by small sample sizes, which impede the assessment of sex differences and aging effects on the association between ANS function and CT. To overcome these limitations, 20 groups worldwide contributed data collected under similar protocols of CT assessment and HR/HRV recording to be pooled in a mega-analysis (N = 1,218 (50.5% female), mean age 36.7 years (range: 12-87)). Findings suggest a decline in HRV as well as CT with increasing age. CT, particularly in the orbitofrontal cortex, explained additional variance in HRV, beyond the effects of aging. This pattern of results may suggest that the decline in HRV with increasing age is related to a decline in orbitofrontal CT. These effects were independent of sex and specific to HRV; with no significant association between CT and HR. Greater CT across the adult lifespan may be vital for the maintenance of healthy cardiac regulation via the ANS – or greater cardiac vagal activity as indirectly reflected in HRV may slow brain atrophy. Findings reveal an important association between cortical thickness and cardiac parasympathetic activity with implications for healthy aging and longevity that should be studied further in longitudinal research

Fiber-based all-optical sampling for ultrafast waveform monitoring

Digital sampling is a technique to visualize a time-varying waveform by capturing quasi-instantaneous snapshots of a signal via a sampling gate. The gate is opened and closed by narrow pulses in a pulse train having a well defined repetitive behaviour such that all parts of the waveform are measured. Sub-picosecond temporal resolution sampling can be achieved with all-optical techniques that utilize the ultrafast response of nonlinear materials in order to implement the required gating functionality. In this thesis, the focus is on the performance of a fiber four-wavemixing (FWM) based all-optical sampling oscilloscope (OSO) in terms of a trade-off between temporal resolution, signal optical bandwidth and signal sensitivity. This work also addresses the fact that the nonlinear processes utilized to implement all-optical sampling gates are inherently strongly dependent on the relative state of polarization (SOP) between the sampling pulses, used to open the sampling gate, and the signal being monitored. A very simple technique is described that completely removes the problem with signal polarization dependence of a fiber FWM-based OSO. All digital sampling schemes require a precise time-base in order to position the acquired samples correctly in time. The time-base is usually dependent on a hardware generated trigger signal, which is normally extracted from the monitored signal. We demonstrate a novel technique to achieve the required time-base by means of a software algorithm applied on the acquired samples. As a result, we can avoid clock-recovery from the signal, and hence, the OSO becomes independent of the waveform repetition frequency. The detrimental polarization dependence of the FWM process can be utilized to implement novel functionality to an OSO. By rotating the state of polarization (SOP) of the sampling pulses during the sampling process, a time-resolved measurement of the SOP of the monitored signal was demonstrated with picosecond temporal resolution. Finally, we used the OSO as a tool to monitor the transmission quality of a 160 Gb/s RZ data signal subjected to polarization mode dispersion (PMD) and third-order dispersion (TOD). Techniques to compensate for PMD and TOD are presented and a large improvement of the transmission quality was achieved