The optical and geometrical properties of microstructured optical
fibres present new alternatives for a range of sensing applications. We
present the design criteria for achieving significant overlap between the
light guided in the fibre and the air holes and hence for producing
efficient evanescent field devices. In addition, the novel dispersive
properties combined with the tight mode confinement possible in holey fibres
make ultra-broadband single-mode sources and new source wavelengths a
possibility. Microstructuring technology can be readily extended to form
multiple-core fibres, which have applications in bend/deformation sensing.
Finally, fibre-based atom waveguides could ultimately be used for
rotational or gravitational sensing.
An improved design for hollow antiresonant fibers (HAFs) is presented. It consists of adding extra antiresonant glass elements within the air cladding region of an antiresonant hollow-core fiber. We use numerical simulations to compare fiber structures with and without the additional cladding elements in the near- and mid-IR regimes. We show that realizable fiber structures can provide greatly improved performance in terms of leakage and bending losses compared to previously reported antiresonant fibers. At mid-IR wavelengths, the adoption of this novel fiber design will lead to HAFs with reduced bending losses. In the near-IR, this design could lead to the fabrication of HAFs with very low attenuation.
We first use numerical simulations to show that bending losses of hollow antiresonant fibers are a strong function of their geometrical structure. We then demonstrate this by fabricating a hollow antiresonant fiber which presents a bending loss as low as 0.25 dB/turn at a wavelength of 3.35 μm and a bend radius of 2.5 cm. This fiber has a relatively low attenuation (<200 dB/km) over 600 nm mid-infrared spectral range.
We use numerical simulations to investigate how the curvature of the fiber core boundary influences the attenuation of hollow antiresonant fibers. We show the importance of a "negative" curvature core boundary in reducing confinement losses and also how, for certain curvatures, optical power is coupled resonantly to cladding modes. We simulate bending losses and find results in agreement with previously-reported experiments.
Abstract-Hollow core antiresonant fibers offer new possibilities in the near infrared and visible spectral range. I show here that the great flexibility of this technology can allow the design and fabrication of hollow core optical fibers with an extended transmission bandwidth in the near infrared and with very low optical attenuation in the visible wavelength regime. A very low attenuation of 175dB/km at 480nm is reported. A modification of the design of the studied fibers is proposed in order to achieve fast-responding gas detection.Index Terms-Hollow core fibers, anti-resonant fibers, optical design, optical fiber fabrication, gas sensing.
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