Backscattering in antiresonant hollow-core fibers: over 40  dB lower than in standard optical fibers

Abstract

The elastic backscattering of light in optical fiber is a fundamental phenomenon that sets the ultimate performance of several fiber systems such as gyroscopes and bidirectional transfer links. Until now, efforts to reduce the backscattering coefficient have yielded limited results, with the lowest value sitting at around − 76 d B / m in Ge-free silica-core fiber at 1.55 µm. Here, we present what we believe to be the first measurement of backscattering from a low-loss antiresonant hollow-core fiber and show that it is more than 40 dB below reported values in silica-core fiber and hollow-core photonic bandgap fiber. The record-low level of − 118 d B / m measured with our custom-built optical frequency-domain reflectometer is in good agreement with simulations in which we assume the scattering to originate from the intrinsic surface roughness. Our demonstration also shows that a tailored instrument can localize and quantify weak faults within a hollow-core fiber, enabling its detailed characterization.

Fundamental thermal noise in antiresonant hollow-core fibers

“…Though a more elaborate noise model and better low-frequency measurements are required to quantify the extent of the potential improvement, an order of magnitude gain already appears within reach in the 10 to 100 kHz range. This high stability potential comes in addition to other desirable properties of NANF such as high polarization purity 71 , low nonlinearity 72 , weak backscattering 60 , and low thermal sensitivity 44 (which can all benefit from core evacuation) in antiresonant HCFs displaying a transmission loss competitive with SMF at 1550 nm 33 and lower than SMF below 1100 nm 73 . Kilometer-scale antiresonant hollowcore fibers, properly shielded from environmental fluctuations and illuminated by high laser power, can therefore be considered for the most demanding interferometric applications.…”

“…The total length of the SMF pigtails contributing to the path imbalance was estimated to be 4.5 m in both cases. Additional information about these HCFs, including details about the HCF to SMF interconnections, can be found in 60 .…”

Highly Birefringent Anti‐Resonant Hollow‐Core Fiber with a Bi‐Thickness Fourfold Semi‐Tube Structure

“…Fortunately, almost all the drawbacks of PBGFs can be overcome by using another type of HCF, i.e., the ARF (also known as an inhibited‐coupling HCF [ 27 ] ), for which broadband transmission, [ 27 ] a high damage threshold, [ 13 ] pure spatial modes, [ 28 ] low backscattering, [ 29 ] and ultralow losses [ 30,31 ] have been demonstrated preliminarily. However, with regard to the high birefringence (on the 10 −4 level) in ARFs, the prevalent view of these fibers is that the high localization of light in air and the weakly guiding nature of a low‐loss ARF will hinder creation of a polarization difference.…”

Light guiding properties of negative-curvature hollow-core fiber

“…It can provide lower loss than Kagome fiber, and the fabrication procedure is more simplified than before [47][48]. The single-ring negative curvature fiber (SR-NCF) and nested nodeless HCF (NANF) are two typical NC-HCF [44,45,[47][48][49][50][51][52][53][54]. The SEM image of the cross section of SR-NCF is shown in Figs.…”

“…Nowadays, NC-HCF achieve great success. NC-HCF can have low confinement loss, acceptable bending loss, and good modal property, which make it promising for many applications [44][45][46][47][48][49][50][51][52][53][54][55]. < 100 dB/km exceeding 1000 nm [40] <1 dB/km over C and L band (measured) [51] Bending loss…”