Sensitive and nonintrusive gas detection finds an increasing number of applications, from biomedical diagnostics to atmospheric sensing. This motivates the exploration of new approaches to optical molecular spectroscopy. Frequency agile laser techniques achieve very fast spectral measurements [1][2][3]. Concurrently, laser frequency combs [4] open up novel opportunities for precise multiplex [5][6][7][8][9][10][11][12][13] or multichannel [14][15][16] spectroscopy with resolved individual Figure 1. Experimental set-up: The continuous-wave laser is intensity-modulated by two electrooptics modulators driven by radio-frequency generators set at slightly different frequencies. Two trains of 50-ps pulses at repetition frequencies of about 300 MHz are spectrally-broadened by wave-breaking in a normal dispersion nonlinear optical fiber, in which they counter-propagate. The gas under study may be contained in a hollow-core photonic crystal fiber, which enhances the absorption path length. The comb beams beat onto a InGaAs fast photodiode. The electric signal is low-pass filtered. The time domain interference signal is then amplified and digitized with a data acquisition board.

PURPOSE. To evaluate the association between retinal microvasculature (vascular density) on optical coherence tomography-angiography (OCT-A) and the cardiovascular profile of patients hospitalized for acute coronary syndrome (ACS). METHODS. EYE-Myocardial Infarction (EYE-MI) study is a prospective cross-sectional study in the Cardiology Intensive Care Unit of Dijon University Hospital. Retinal OCT-A was performed for each patient within 2 days after admission. Superficial retinal capillary plexus (SCP) vascular density was measured. The population was divided into tertiles according to OCT-A data. RESULTS. Overall, 237 cases were retained for analysis. Patients in the tertile with the lowest retinal vascular density (RVD) were older, and more frequently had systemic hypertension and diabetes. Moreover, American Heart Association (AHA) risk and Global Registry of Acute Coronary Events (GRACE) scores were higher and left ventricular ejection fraction (LVEF) was lower in these patients. In multivariate analysis, the AHA risk score (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.04-1.09; P < 0.001) and LVEF (OR, 0.95; 95% CI, 0.93-0.98; P ¼ 0.001) were significantly associated with the lowest tertile of RVD. The association between RVD and a high-risk cardiovascular profile was confirmed by a moderate correlation with the GRACE scores (Spearman r ¼ À0.33, P < 0.001). CONCLUSIONS. SCP density measured on OCT-A was associated with the cardiovascular risk profile and with impaired LVEF in patients with a high-risk cardiovascular status. In the future, quantitative retinal microvascular data could be considered a good surrogate of the cardiovascular risk profile and could improve cardiovascular risk assessments.

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In many photonics applications, especially in optical fibre based systems, the state of polarization of light remains so far an elusive uncontrolled variable, which can dramatically affect the performances of that systems and which one would like to control as finely as possible. Here, we experimentally demonstrate light-by-light polarization control via a nonlinear effect occurring in single mode optical fibre. We observe a polarization attraction and stabilization of a 10 Gbit/s optical telecommunication signal around 1550 nm. We also validate the potentiality of the device to annihilate very fast nanosecond polarization bursts. This result confirms yet another fascinating possibility to all-optical control the light properties in optical fibre.

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The nonlinear propagation of a partially coherent continuous-wave laser beam in single-mode optical fibers is investigated both theoretically and experimentally, with a special attention to the zero-dispersion wavelength region where modulation instability is expected. Broadband asymmetric spectral broadening is reported experimentally and found in fairly good agreement with a numerical Schrödinger simulation including a phase-diffusion model for the partially coherent beam. This model shows in addition that the underlying spectral broadening mechanism relies not only on modulation instability but also on the generation of high-order soliton-like pulses and dispersive waves. The coherence degradation which results from these ultrafast phenomena is confirmed by autocorrelation measurement.

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