Trench-Assisted Multicore Fiber with Single Supermode Transmission and Nearly Zero Flattened Dispersion

Abstract

A trench-assisted multicore fiber (TA-MCF) with single-supermode transmission and nearly zero flattened dispersion is proposed herein. By adding a simplified microstructure cladding with only one ring of low-index inclusions on the basis of the multicore fiber, the microstructure cladding and mode-coupling mechanism were jointly employed into the TA-MCF to modulate light transmission. This guarantees that the TA-MCFs had sufficient capability for wideband dispersion management when only pure, germanium-doped, and fluorine-doped silica glass with low index differences were chosen to form the TA-MCF. Analyses also revealed that the TA-MCFs have the merits of shorter cut-off wavelength and flatter-top optical intensity distribution compared with traditional multicore fibers. After the investigation of the structural parameters’ influences on the dispersion of the fundamental supermode, two TA-MCFs with single-supermode transmission and nearly zero flattened dispersion were designed. For the seven-core TA-MCF, the dispersion varying from −0.46 to 1.35 ps/(nm·km) in the wavelength range of 1.50 to 2.04 μm, with bending loss as low as 0.085 dB/km and 35-mm bending radius at 1550 nm was achieved with index difference less than 0.015. The TA-MCFs proposed herein have the advantages of being a quasi-single material, with an all solid scheme and simplified structure.

Chemical peptide macrolactonization via intramolecular S‐to‐S‐to‐O acyl transfer

“…We synthesized a panel of model peptide precursors, Ac‐Xaa‐Pro‐Zaa‐Gly‐Arg‐Gln‐Trp‐Ser‐Gly‐MESNa thioester (Figure 2a; in 1 – 4 , Xaa is assigned to Ser, Thr, Lys, or L‐2,3‐diaminopropionic acid [Dap], and Zaa is Cys; in 5 , Xaa is Ser, and Zaa is penicillamine [Pen]) where the underlined residues are consisting of either SPCG or its mutant motif followed by an arbitrary peptide sequence (RQWSG) attaching to the MESNa thioester at the C‐terminus. The respective precursor peptides were prepared by standard Fmoc‐SPPS followed by C‐terminal thioesterfication according to the method reported by Liu and coworkers as follows (Figure S1): [ 29,35 ] The peptides‐hydrazide was synthesized and purified by HPLC, and then the acyl azide was formed by sodium nitrite oxidation; this intermediate peptide was thioesterified by an excess amount of MESNa to yield the peptide‐MES thioester ( 1 – 5 ). We initially attempted in situ macrolactonization (via the intramolecular S ‐to‐ S ‐to‐ O acyl transfer) from the crude peptide‐MES thioester by elevating the pH to 7.5, but an excess residual MESNa disallowed an efficient S ‐to‐ O acyl transfer to occur.…”

“…The procedure followed previous report, as long as particularly mentioned. [ 29 ] The crude hydrazide peptide was dissolved in NCL buffer (6 M GnCl, 200 mM NaH 2 PO 4 buffer (pH range 3–4) to a concentration of 1–2 mM (measured by Nanodrop). After preparation of ice/salt bath at −15 °C, 1 ml of the peptide solution was put at 2 ml tube and cooled at −15 °C.…”

Supercontinuum Generation in the Cladding Modes of an Endlessly Single-Mode Fiber

“…In the case of ESF, however, these large area modes of the cladding can still have a relatively short-wavelength zero dispersion because of the additional confinement provided by close air-hole spacing. These types of effects are also seen in supermode fibers, where the overall dispersion properties of the supermode are strongly governed by the properties of each individual core that make up the supermode [29]. This allows the intensity of a supermode to spread out over all of the coupled cores of the fiber while maintaining the dispersion characteristics of the individual fibers.…”

Hollow-Core Negative Curvature Fiber with High Birefringence for Low Refractive Index Sensing Based on Surface Plasmon Resonance Effect

“…The confinement loss α Loss of the core mode as an important parameter can indicate the strength of the SPR effect, which is described as [ 26 , 27 ]: where Im( n eff ) stands for the imaginary part of the effective RI.…”