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North Granby, CT, United States

Nufern | Date: 2014-09-16

The present invention relates generally to a mount for securely holding an optical fiber in place, for example, on an optical bench or a translation stage. In one embodiment, the mount includes a lower block having a first portion, which has an upward-facing channel formed in the top surface thereof and extending from the front surface to the rear region. The channel forms a groove at its bottom. The mount further includes an upper block disposed over the first portion of the lower block. The upper block has a downward-facing ridge that includes one or more holding surfaces disposed adjacent the groove and extending along the downward-facing ridge. The upper block is held against the first portion of the lower block, such that the one or more holding surfaces are positioned to hold the optical fiber in the groove.

The present invention relates to optical fibers useful for the transmission of electromagnetic energy at such high levels of power that stimulated Brillouin scattering (SBS) may be of importance. One aspect of the present invention is an optical fiber for the propagation of optical radiation having an optical wavelength, the optical fiber and optical wavelength having an SBS acoustic wavelength associated therewith, the optical fiber comprising a core having a geometrical center and an outer perimeter; and a cladding surrounding the core; wherein the core is rare earth doped and substantially free of germanium, the optical fiber has a refractive index profile such that the core is guiding for optical radiation having the optical wavelength, and the optical fiber has an acoustic index profile such that the core is antiguiding for an acoustic wave having the SBS acoustic wavelength.

An optical fiber preform, and method for fabricating, having a first core, a second core spaced from the first core and first and second regions, the first region having an outer perimeter having a first substantially straight length and the second region having an outer perimeter having a second substantially straight length facing the first straight length. One of the regions can comprise the first core and the other comprises the second core. The preform can be drawn with rotation to provide a fiber wherein a first core of the fiber is multimode at a selected wavelength of operation and a second core of the fiber is spaced from and winds around the first core and has a selected longitudinal pitch. The second core of the fiber can couple to a higher order mode of the first core and increase the attenuation thereof relative to the fundamental mode of the first core.

Gu G.,Clemson University | Kong F.,Clemson University | Hawkins T.W.,Clemson University | Foy P.,Thorlabs | And 3 more authors.
Optics Express | Year: 2013

In a leakage channel fiber, the desired fundamental mode (FM) has negligible waveguide loss. Higher-order modes (HOM) are designed to have much higher waveguide losses so that they are practically eliminated during propagation. Coherent reflection at the fiber outer boundary can lead to additional confinement especially for highly leaky HOM, leading to lower HOM losses than what are predicted by conventional FEM mode solver considering infinite cladding. In this work, we conducted, for the first time, careful measurements of HOM losses in two leakage channel fibers (LCF) with circular and rounded hexagonal boundary shapes respectively. Impact on HOM losses from coiling, fiber boundary shapes and coating indexes were studied in comparison to simulations. This work, for the first time, demonstrates the limit of the simulation method commonly used in the large-mode-area fiber designs and the need for an improved approach. More importantly, this work also demonstrates that a deviation from circular fiber outer shape may be an effective method to mitigate HOM loss reduction from coherent reflection from fiber outer boundary, even in double-clad fibers, with HOM losses in excess of 20dB/m measured in the hexagonal LCF with ~50?m core diameter while keeping FM loss negligible. ©2013 Optical Society of America. Source

Barankov R.A.,Boston University | Wei K.,Nufern | Samson B.,Nufern | Ramachandran S.,Boston University
Optics Letters | Year: 2012

Leakage channel fibers, designed to suppress higher-order modes, demonstrate resonant power loss at certain critical radii of curvature. Outside the resonance, the power recovers to the levels offset by the usual mechanism of bend-induced loss. Using C2 imaging, we experimentally characterize this anomaly and identify the corresponding physical mechanism as the radiative decay of the fundamental mode mediated by the resonant coupling to a cladding mode. © 2012 Optical Society of America. Source

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