Coherent terabit communications with microresonator Kerr frequency combs

Optical frequency combs enable coherent data transmission on hundreds of wavelength channels and have the potential to revolutionize terabit communications. Generation of Kerr combs in nonlinear integrated microcavities represents a particularly promising option enabling line spacings of tens of GHz, compliant with wavelength-division multiplexing (WDM) grids. However, Kerr combs may exhibit strong phase noise and multiplet spectral lines, and this has made high-speed data transmission impossible up to now. Recent work has shown that systematic adjustment of pump conditions enables low phase-noise Kerr combs with singlet spectral lines. Here we demonstrate that Kerr combs are suited for coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the optical source. In a first experiment, we encode a data stream of 392 Gbit/s on subsequent lines of a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature amplitude modulation (16QAM). A second experiment shows feedback-stabilization of a Kerr comb and transmission of a 1.44 Tbit/s data stream over a distance of up to 300 km. The results demonstrate that Kerr combs can meet the highly demanding requirements of multi-terabit/s coherent communications and thus offer a solution towards chip-scale terabit/s transceivers

A shock to the (health) system: Experiences of adults with rare disorders during the first COVID-19 wave

BackgroundBefore COVID-19, people with rare diseases (RD) experienced numerous disparities in quality of life and healthcare access and quality, yet little is known about the experiences of this underserved group during the pandemic.ResultsDuring the first wave of the COVID-19 pandemic in the United States, spring and summer of 2020, 759 participants representing 231 unique RDs responded to open-ended questions about the impact of the pandemic on life with a RD, healthcare access, and coping. Qualitative conventional content analysis was used to analyze responses. Identified themes represented positive and negative dimensions of change, including a shock to the (health) system, coping with uncertainty, and the value of social support while isolated.ConclusionsLimitations in healthcare access and quality were the most frequently described as impacts of COVID-19. Other major negative impacts included exacerbation of symptoms, psychological distress, and a lack of usual social support and reliable information. However, participants also noted silver linings, especially in healthcare. For some, expanded telehealth enhanced their ability to access medical and mental health providers and RD specialists. Finally, many participants hoped that, by highlighting social and health inequities faced by people with RDs and other minorities, the pandemic would prompt greater understanding and policies that could improve the quality of life of the RD community