Linli Meng

Low-loss hollow-core fibers with improved single-modedness

Hollow-core fibers (HCFs) are a revolution in light guidance with enormous potential. They promise lower loss than any other waveguide, but have not yet achieved this potential because of a tradeoff between loss and single-moded operation. This paper demonstrates progress on a strategy to beat this tradeoff: we measure the first hollow-core fiber employing Perturbed Resonance for Improved Single Modedness (PRISM), where unwanted modes are robustly stripped away. The fiber has fundamental-mode loss of 7.5 dB/km, while other modes of the 19-lattice-cell core see loss >3000 dB/km. This level of single-modedness is far better than previous 19-cell or 7-cell HCFs, and even comparable to some commercial solid-core fibers. Modeling indicates this measured loss can be improved. By breaking the connection between core size and single-modedness, this first PRISM demonstration opens a new path towards achieving the low-loss potential of HCFs.

Measuring higher-order modes in a low-loss, hollow-core, photonic-bandgap fiber

We perform detailed measurements of the higher-order-mode content of a low-loss, hollow-core, photonic-bandgap fiber. Mode content is characterized using Spatially and Spectrally resolved (S2) imaging, revealing a variety of phenomena. Discrete mode scattering to core-guided modes are measured at small relative group-delays. At large group delays a continuum of surface modes and core-guided modes can be observed. The LP11 mode is observed to split into four different group delays with different orientations, with the relative orientations preserved as the mode propagates through the fiber. Cutback measurements allow for quantification of the loss of different individual modes. The behavior of the modes in the low loss region of the fiber is compared to that in a high loss region of the fiber. Finally, a new measurement technique is introduced, the sliding-window Fourier transform of high-resolution transmission spectra of hollow-core fibers, which displays the dependence of HOM content on both wavelength and group delay. This measurement is used to illustrate the HOM content as function of coil diameter.

Polarization Maintaining Single-Mode Low-Loss Hollow-Core Fiber

Hollow-core fibre (HCF) is a powerful technology platform offering breakthrough performance improvements in sensing, communications, higher-power pulse delivery and other applications. Free from the usual constraints on what materials can guide light, it promises qualitatively new and ideal operating regimes: precision signals transmitted free of nonlinearities, sensors that guide light directly in the samples they are meant to probe and so on. However, these fibres have not been widely adopted, largely because uncontrolled coupling between transverse and polarization modes overshadows their benefits. To deliver on their promises, HCFs must retain their unique properties while achieving the modal and polarization control that are essential for their most compelling applications. Here we present the first single-moded, polarization-maintaining HCF with large core size needed for loss scaling. Single modedness is achieved using a novel scheme for resonantly coupling out unwanted modes, whereas birefringence is engineered by fabricating an asymmetrical glass web surrounding the core.

First demonstration of hollow-core fiber for intra data center low latency connectivity with a commercial 100Gb/s interface

For the first time 100Gb/s transmission using commercial low latency hardware is demonstrated over the longest manufactured hollow-core fiber (2.75km) to date, proving the feasibility of ultra-low latency intra-data center connectivity.

High resolution S 2 mode imaging of photonic bandgap fiber

Spatially and spectrally resolved mode imaging of a 19 cell photonic bandgap fiber with minimum loss at 1550 nm is demonstrated using a high resolution tunable laser and phosphor-coated CCD camera.

Transmission of Commercial Low Latency Interfaces Over Hollow-Core Fiber

For the first time, we successfully demonstrate the transmission of commercial 10- and 100-Gb/s interfaces, both direct detect and coherent, over 2.75 km of hollow-core fiber. The fiber is connected to the transceivers using spliced standard single-mode pigtails. This demonstration solidifies the commercial potential for low latency applications.

Low-Loss Low-Latency Transmission Over Single-Mode Hollow Core Fiber at 10 and 120 Gb/s

We present a single-mode hollow-core fiber with loss of 5.7 dB/km for low latency transmission. We demonstrated penalty-free transmission over 1 and 300 m at 10 Gb/s and 120 Gb/s without optimization of launch conditions.

37-cell hollow-core-fiber designs with improved single-modedness

Simulations show that resonant shunt cores for suppression of higher-order modes in hollow-core fibers can be applied broadly, to cores larger than 19-cell and core thicknesses larger than half the lattice web thickness.

Single-mode hollow-core fiber for portable acetylene sub-Doppler frequency reference

A newly-developed, single-mode hollow-core fiber is employed for saturated absorption spectroscopy in a molecular gas. Lack of surface modes, ease of angle splicing, and single-modedness make it promising for portable frequency references.

Hollow-Core Photonic Bandgap PRISM Fibers for Low Loss Single-Mode Guidance

We demonstrate a 19-cell hollow core fiber with essentially single-mode propagation and 7.5 dB/km loss using a PRISM (Perturbed Resonance for Improved Single Modedness) design. This approach has potential for further loss reduction.