According to some embodiments method for making an optical fiber preform comprises the steps of: (i) placing a plurality of rods with an outer surface having a coefficient of friction 0.02≦COF≦0.3 into an inner cavity of an apparatus; (ii) placing particulate glass material in the inner cavity between the rods and an inner wall of the mold cavity; and (iii) applying pressure against the particulate glass material to press the particulate glass material against the plurality of rods.

Certain exemplary embodiments can provide a system, machine, device, manufacture, circuit, and/or composition of matter, and/or a method for activities, that can comprise and/or relate to, a polarization-maintaining photonic crystal fiber comprising an elongated guiding core and/or an elongated photonic crystal cladding surrounding the core, the cladding defining a plurality of holes.

An optical fiber may comprise a core doped with one or more active ions to guide signal light from an input end of the optical fiber to an output end of the optical fiber, a cladding surrounding the core to guide pump light from the input end of the optical fiber to the output end of the optical fiber, and one or more inserts formed in the cladding surrounding the core. The core may have a geometry (e.g., a cross-sectional size, a helical pitch, and/or the like) that varies along a longitudinal length of the optical fiber, which may cause an absorption of the pump light to be modulated along the longitudinal length of the optical fiber.

Certain exemplary embodiments can provide a system, machine, device, manufacture, circuit, and/or composition of matter, and/or a method for activities, that can comprise and/or relate to, a polarization-maintaining photonic crystal fiber comprising an elongated guiding core and/or an elongated photonic crystal cladding surrounding the core, the cladding defining a plurality of holes.

An optical fiber may comprise a core doped with one or more active ions to guide signal light from an input end of the optical fiber to an output end of the optical fiber, a cladding surrounding the core to guide pump light from the input end of the optical fiber to the output end of the optical fiber, and one or more inserts formed in the cladding surrounding the core. The core may have a geometry (e.g., a cross-sectional size, a helical pitch, and/or the like) that varies along a longitudinal length of the optical fiber, which may cause an absorption of the pump light to be modulated along the longitudinal length of the optical fiber.

A preform element, its production, and fiber production methods from preform assemblies. The preform element has a length and a center axis along its length, a first and second end defined by its length and an outer preform element surface. The preform element includes a plurality of longitudinal structures disposed to form longitudinal hole(s) in a background material. At least one slot extending from its outer preform element surface and intersecting at least one of the longitudinal holes, wherein the at least one slot does not fully intersect the preform element. The preform element may be a preform center element or a preform ring element and may be assembled to a form part of a preform assembly for an optical fiber.

A preform element, it production and fiber production methods from preform assemblies are disclosed. The preform element has a length and a center axis along its length, a first and second end defined by its length and an outer preform element surface. The preform element comprises a plurality of longitudinal structures disposed to form longitudinal hole(s) in a background material. At least one slot extending from its outer preform element surface and intersecting at least one of the longitudinal holes, wherein the at least one slot does not fully intersect the preform element. The preform element may be a preform center element or a preform ring element and may be assembled to a form part of a preform assembly for an optical fiber.

This application relates generally to an optical fiber for the delivery of infrared light where the polarization state of the light entering the fiber is preserved upon exiting the fiber and the related methods for making thereof. The optical fiber has a wavelength between about 0.9 m and 15 m, comprises at least one infrared-transmitting glass, and has a polarization-maintaining (PM) transverse cross-sectional structure. The infrared-transmitting, polarization-maintaining (IR-PM) optical fiber has a birefringence greater than 10.sup.5 and has applications in dual-use technologies including laser power delivery, sensing and imaging.

A polarization maintaining fiber includes: a core; an inner cladding enclosing the core; two stress applying parts that sandwich the inner cladding therebetween; and an outer cladding enclosing the inner cladding and the two stress applying parts. Each of the two stress applying parts is depressed inward against the inner cladding, and the core has a flattened cross section having a long-axis that corresponds to a direction in which the two stress applying parts are aligned.

A polarization-maintaining optical fiber includes at least one polarization maintaining core, a first cladding surrounding the at least one polarization maintaining core, and a second cladding surrounding the first cladding. The at least one polarization maintaining core includes a core and a pair of low-refractive-index portions each having a refractive index lower than a refractive index of the core. In a cross section, at least a portion of an outer periphery of each of the pair of low-refractive-index portions is in contact with the core, and an outer periphery of the core, excluding portions each being in contact with the low-refractive-index portions, has a circular shape. A maximum value of an absolute value of a residual stress in the cross section is 100 MPa or less. A mode-field flattening f is 0.05 to 0.40 at any wavelength within a range of 850 nm to 1625 nm.