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

Flexible terabit/s Nyquist-WDM super-channels using a gain-switched comb source

Terabit/s super-channels are likely to become the standard for next-generation optical networks and optical interconnects. A particularly promising approach exploits optical frequency combs for super-channel generation. We show that injection locking of a gain-switched laser diode can be used to generate frequency combs that are particularly well suited for terabit/s super-channel transmission. This approach stands out due to its extraordinary stability and flexibility in tuning both center wavelength and line spacing. We perform a series of transmission experiments using different comb line spacings and modulation formats. Using 9 comb lines and 16QAM signaling, an aggregate line rate (net data rate) of 1.296 Tbit/s (1.109 Tbit/s) is achieved for transmission over 150 km of standard single mode fiber (SSMF) using a spectral bandwidth of 166.5 GHz, which corresponds to a (net) spectral efficiency of 7.8 bit/s/Hz (6.7 bit/s/Hz). The line rate (net data rate) can be boosted to 2.112 Tbit/s (1.867 Tbit/s) for transmission over 300 km of SSMF by using a bandwidth of 300 GHz and QPSK modulation on the weaker carriers. For the reported net data rates and spectral efficiencies, we assume a variable overhead of either 7\% or 20\% for forward- error correction depending on the individual sub-channel quality after fiber transmission

Optimally Coherent Kerr Combs Generated with Crystalline Whispering Gallery Mode Resonators for Ultrahigh Capacity Fiber Communications

International audienceOptical Kerr frequency combs are known to be effective coherent multiwavelength sources for ultrahigh capacity fiber communications. These combs are the frequency-domain counterparts of a wide variety of spatiotemporal dissipative structures, such as cavity solitons, chaos, or Turing patterns (rolls). In this Letter, we demonstrate that Turing patterns, which correspond to the so-called primary combs in the spectral domain, are optimally coherent in the sense that for the same pump power they provide the most robust carriers for coherent data transmission in fiber communications using advanced modulation formats. Our model is based on a stochastic Lugiato-Lefever equation which accounts for laser pump frequency jitter and amplified spontaneous emission noise induced by the erbium-doped fiber amplifier. Using crystalline whispering-gallery-mode resonators with quality factor Q∼109 for the comb generation, we show that when the noise is accounted for, the coherence of a primary comb is significantly higher than the coherence of their solitonic or chaotic counterparts for the same pump power. In order to confirm this theoretical finding, we perform an optical fiber transmission experiment using advanced modulation formats, and we show that the coherence of the primary comb is high enough to enable data transmission of up to 144  Gbit/s per comb line, the highest value achieved with a Kerr comb so far. This performance evidences that compact crystalline photonic systems have the potential to play a key role in a new generation of coherent fiber communication networks, alongside fully integrated systems

Terabit/s communications using chip-scale frequency comb sources

High-speed optical interconnects rely on advanced wavelength-division multiplexing (WDM) schemes. However, while photonic-electronic interfaces can be efficiently realized on silicon-on-insulator chips, dense integration of the necessary light sources still represents a major challenge. Chip-scale frequency comb sources present an attractive alternative for providing a multitude of optical carriers for WDM transmission. In this paper, we give an overview of our recent progress towards terabit communications with chip-scale frequency comb sources. In a first set of experiments, we demonstrate frequency comb generation based on silicon-organic hybrid (SOH) electro-optic modulators, enabling line rates up to 1.152 Tbit/s. In a second set of experiments, we use injection locking of a gain-switched laser diode to generate frequency combs. This approach leads to line rates of more than 2 Tbit/s. A third set of experiments is finally dedicated to using Kerr nonlinearities in integrated nonlinear microcavities for frequency comb generation. We demonstrate coherent communication using Kerr frequency comb sources, thereby achieving line rates up to 1.44 Tbit/s. Our experiments show that frequency comb generation in chip-scale devices represents a viable approach to terabit communications

Outcomes After Transcatheter Mitral Valve Replacement According to Regurgitation Etiology.

BACKGROUND Whether transcatheter mitral valve replacement (TMVR) devices perform similarly with respect to the underlying mitral regurgitation (MR) etiology remains unelucidated yet. The aim of the present analysis was to assess outcomes of TMVR according to the MR underlying etiology among the CHoice of OptImal transCatheter trEatment for Mitral Insufficiency Registry (CHOICE-MI) registry. METHODS Out of 746 patients, 229 (30.7%) patients underwent TMVR. The study population was subdivided according to primary, secondary or mixed MR. Patients with mitral annular calcification were excluded. The primary study endpoint was a composite endpoint of all-cause mortality or hospitalisation for heart failure at 1 year. Secondary study endpoints included all-cause and cardiovascular mortality at 1 year, New York Heart Association functional class and residual MR, both at discharge and 1 year. RESULTS The predominant MR etiology was secondary MR (58.4%), followed by primary MR (28.7%), and mixed MR (12.9%). Technical success was similar according to MR etiology as was procedural mortality. Discharge echocardiography revealed residual MR 2+ in 11.3%, 3.7%, and 5.3% of patients with primary, secondary, and mixed MR, respectively (P=0.1). MR elimination was similar in all groups up to the 1-year follow-up. There was no difference in terms of primary combined outcome occurrence according to MR etiology. One-year all-cause mortality was reported in 28.8%, 24.2% and 32.1% of the patients with primary, secondary and mixed MR (P=0.07), respectively. CONCLUSIONS In our study, we did not find differences in short- and 1-year outcomes after TMVR according to MR etiology

Clinical outcomes of transcatheter mitral valve replacement: two-year results of the CHOICE-MI Registry.

BACKGROUND Transcatheter mitral valve replacement (TMVR) using dedicated devices is an alternative therapy for high-risk patients with symptomatic mitral regurgitation (MR). AIMS This study aimed to assess the 2-year outcomes and predictors of mortality in patients undergoing TMVR from the multicentre CHOICE-MI Registry. METHODS The CHOICE-MI Registry included consecutive patients with symptomatic MR treated with 11 different dedicated TMVR devices at 31 international centres. The investigated endpoints included mortality and heart failure hospitalisation rates, procedural complications, residual MR, and functional status. Multivariable Cox regression analysis was applied to identify independent predictors of 2-year mortality. RESULTS A total of 400 patients, median age 76 years (interquartile range [IQR] 71, 81), 59.5% male, EuroSCORE II 6.2% (IQR 3.8, 12.0), underwent TMVR. Technical success was achieved in 95.2% of patients. MR reduction to ≤1+ was observed in 95.2% at discharge with durable results at 1 and 2 years. New York Heart Association Functional Class had improved significantly at 1 and 2 years. All-cause mortality was 9.2% at 30 days, 27.9% at 1 year and 38.1% at 2 years after TMVR. Chronic obstructive pulmonary disease, reduced glomerular filtration rate, and low serum albumin were independent predictors of 2-year mortality. Among the 30-day complications, left ventricular outflow tract obstruction, access site and bleeding complications showed the strongest impact on 2-year mortality. CONCLUSIONS In this real-world registry of patients with symptomatic MR undergoing TMVR, treatment with TMVR was associated with a durable resolution of MR and significant functional improvement at 2 years. Two-year mortality was 38.1%. Optimised patient selection and improved access site management are mandatory to improve outcomes