Record bandwidth waveband-shift-free optical phase conjugation in nonlinear fiber optical loop mirror.

We present a novel configuration for broadband, wavelength-shift-free optical phase conjugation (OPC) utilizing four-wave mixing in a nonlinear fiber optical loop mirror (NOLM). In the proposed configuration, the input signals and the pump wave return to the input port of the NOLM whereas the phase-conjugated signals generated in the NOLM loop are transmitted through the output port. This allows the phase-conjugated copies to occupy the same wavelength band as the input signals, in line with the requirements for practical deployment of OPC in communication links.

Vacuum-free femtosecond fiber laser microplasma X-ray source for radiography.

Radiographic imaging using X-rays is a tool for basic research and applications in industry, materials science, and medical diagnostics. In this article, we present a novel approach for the generation of X-rays using a vacuum-free microplasma by femtosecond fiber laser. By tightly focusing a laser pulse onto a micrometer-sized solid density near-surface plasma from a rotating copper target, we demonstrate the generation of Cu K-photons (8-9 keV) with high yield ∼ 1.

Hepatobiliary system and intestinal injury in new coronavirus infection (COVID-19): A retrospective study.

Background: An important area of effective control of the coronavirus disease 19 (COVID-19) pandemic is the study of the pathogenic features of severe acute respiratory syndrome coronavirus 2 infection, including those based on assessing the state of the intestinal microbiota and permeability.

Aim: To study the clinical features of the new COVID-19 in patients with mild and moderate severity at the stage of hospitalization, to determine the role of hepatobiliary injury, intestinal permeability disorders, and changes in the qualitative and quantitative composition of the microbiota in the development of systemic inflammation in patients with COVID-19.

Methods: The study was performed in 80 patients with COVID-19, with an average age of 45 years, 19 of whom had mild disease, and 61 had moderate disease severity.

Design of an interferometric fiber optic parametric amplifier for the rejection of unwanted four-wave mixing products.

We introduce a novel (to our knolwedge) interferometric fiber optic parametric amplifier (FOPA), allowing for the suppression of unwanted four-wave mixing products. We perform simulations of two configurations where one rejects idlers and, the other rejects nonlinear crosstalk from the signal output port. The numerical simulations presented here demonstrate the practical feasibility of suppressing idlers by >28 dB across at least 10 THz enabling the reuse of the idler frequencies for signal amplification and thus doubling the employable FOPA gain bandwidth.

Dual-band fiber optic parametric amplifier for bi-directional transient-sensitive fiber optical transmission links.

We demonstrate an in-line polarization-insensitive fiber optic parametric amplifier (PI-FOPA) to simultaneously amplify burst and non-burst signals transmitted in opposite directions in C and L bands. The PI-FOPA provides >16 dB polarization insensitive net gain for signals which are 53 nm apart and counter-propagating in an extended reach link: an upstream bursty signal at 1533 nm and a downstream non-burst signal at 1586 nm. The PI-FOPA potential application as an in-line dual-band amplifier in transient-sensitive communication links is demonstrated by its employment in an extended reach access network with a symmetric 10 Gbps capacity.