A robust, rugged, and small hybrid fiber for use in reference chambers was created using a Hollow-Core Photonic Bandgap Fiber (HCPBF). The hybrid fiber and associated chamber apparatus is amenable to mass production and can be used for wavelengths of light from 400 nm to 2000 nm. The apparatus and method of making thereof is described herein.

A source of optical supercontinuum radiation comprises a length of microstructured optical fiber and a pump laser adapted to generate lasing radiation at a pump wavelength. The length of microstructured optical fiber is arranged to receive lasing radiation at the pump wavelength to generate optical supercontinuum radiation and comprises a core region and a cladding region which surrounds the core region. The source of optical supercontinuum radiation is arranged such that at a location along the length of the microstructured optical fiber (a) the microstructured optical fiber comprises a group index (GI) versus wavelength curve having a zero crossing wavelength (ZCW) at which the group velocity dispersion has a zero crossing and such that the GI increases for wavelengths away from the ZCW such that the curve includes group indices that are greater than the GI at the ZCW for wavelengths greater than as well as less than the ZCW; (b) light having a wavelength of greater than 2000 nm propagates along the length of microstructured optical fiber and has a GI that is matched to the GI of light that propagates along the length of microstructured optical fiber and that has a wavelength of less than 400 nm; and (c) the pump wavelength is within 200 nm of the ZCW.

Microstructured optical fiber (MOF) includes a cladding extending a length between first and second ends. The cladding includes an inner porous microstructure that at least partially surrounds a hollow core. A perimeter contour of the hollow core has a non-uniform radial distance from a center axis of the cladding such that first segments of the cladding along the perimeter contour have a shorter radial distance from the center axis relative to second segments of the cladding along the perimeter contour. The cladding receives and propagates light energy through the hollow core, and the inner porous microstructure substantially confines the light energy within the hollow core. The cladding defines at least one port hole that extends radially from an exterior surface of the cladding to the hollow core. Each port hole penetrates the perimeter contour of the hollow core through one of the second segments of the cladding.

The invention relates to a supercontinuum light source comprising a microstructured optical fiber and a pump light source. The microstructured optical fiber comprises a core and a cladding region surrounding the core, as well as a first fiber length section, a second fiber length section and an intermediate fiber length section between said first and second fiber length sections. The first fiber length section comprises a core with a first characteristic core diameter. The second fiber length section comprises a core with a second characteristic core diameter, smaller than said first characteristic core diameter, where said second characteristic core diameter is substantially constant along said second fiber length section. The intermediate length section of the optical fiber comprises a core which is tapered from said first characteristic core diameter to said second characteristic core diameter over a tapered length.

A microstructured optical fiber has periodically arranged high-index rods embedded in a low-index background, a high-index ring surrounding the high-index rods, and a high-index core located at the center. The high-index rods and the low-index background forms a microstructured cladding region which supports the guidance of supermodes. The fundamental and the highest supermodes form a cladding-mode band, wherein at least the effective index of a core mode lies in the cladding-mode band. Also provided is

a technique for selectively filtering the fiber modes, to selectively filter out one or some of the high-order modes with the other modes still guided in the core with low loss. The cascade of optical fibers can filter out a group of fiber modes, marking guidance of a single high-order mode in a few-mode optical fiber possible.

The present disclosure is a photonic crystal fiber in which a plurality of holes are formed in a cladding, having a uniform light refractive index, capable of propagating three modes of a fundamental mode, a first higher-order mode, and a second higher-order mode, wherein the plurality of holes are disposed in a triangular lattice pattern so as to surround a center of the photonic crystal fiber with no hole disposed at the center of the photonic crystal fiber, and the photonic crystal fiber has a ratio d/A of a diameter d of each of the holes to a pitch A between the holes such that a confinement loss of a third higher-order mode at a minimum wavelength within a used wavelength range is 1.0 dB/m or more and a confinement loss at a maximum wavelength is 0.001 dB/km or less.

Fiber optic amplification in a spectrum of infrared electromagnetic radiation is achieved by creating a chalcogenide photonic crystal fiber (PCF) structure having a radially varying pitch. A chalcogenide PCF system can be tuned during fabrication of the chalcogenide PCF structure, by controlling, the size of the core, the size of the cladding, and the hole size to pitch ratio of the chalcogenide PCF structure and tuned during exercising of the chalcogenide PCF system with pump laser and signal waves, by changing the wavelength of either the pump laser wave or the signal wave, maximization of nonlinear conversion of the chalcogenide PCF, efficient parametric conversion with low peak power pulses of continuous wave laser sources, and minimization of power penalties and minimization of the need for amplification and regeneration of pulse transmissions over the length of the fiber, based on a dispersion factor.

The invention relates to a photonic crystal fiber, in particular single-mode fiber, for the transmission of electromagnetic radiation in the IR wavelength range of >1 m, in particular in the wavelength range from 1 m to 20 m, preferably from 9 m to 12 m, having a light-conducting hollow core, in particular a hollow core having a diameter D, and a plurality of hollow bodies, in particular hollow tubes composed of a chalcogenide glass, arranged around the light-conducting hollow core. The hollow bodies (10, 20) are arranged in such a way that the diameter D of the light-conducting hollow core is greater than the shortest wavelength to be transmitted, preferably at least 20 m, preferably at least 50 m, particularly preferably at least 100 m, preferably in the range from 100 m to 500 m, in particular in the range from 150 m to 350 m, and the damping for the transmission of electromagnetic radiation is <2 dB/m, in particular <1 dB/m, preferably <0.3 dB/m, in particular <0.1 dB/m.

A supercontinuum optical pulse source provides a combined supercontinuum. The supercontinuum optical pulse source comprises one or more seed pulse sources, and first and second optical amplifiers arranged along first and second respective optical paths. The first and second optical amplifiers are configured to amplify one or more optical signals generated by said one or more seed pulse sources. The supercontinuum optical pulse source further comprises a first microstructured light-guiding member arranged along the first optical path and configured to generate supercontinuum light responsive to an optical signal propagating along said first optical path, and a second microstructured light-guiding member arranged along the second optical path and configured to generate supercontinuum light responsive to an optical signal propagating along said second optical path. The supercontinuum optical pulse source further comprises a supercontinuum-combining member to combine supercontinuum generated in at least the first and second microstructured light-guiding members to form a combined supercontinuum. The supercontinuum-combining member comprises an output fiber, wherein the output fiber comprises a silica-based multimode optical fiber supporting a plurality of spatial modes at one or more wavelengths of the combined supercontinuum.

In some embodiments, an optical transmission system includes a few-mode fiber that supports at least 2 spatial modes but no more than 50 spatial modes.