A method for estimating an environmental parameter includes transmitting a first interrogation signal into an optical fiber, receiving a reflected return signal including light reflected from one or more of the plurality of FBG's in the fiber and receiving at a processor data describing the reflected return signal. The received data is comparted to expected data to determine a shift in wavelength of light reflected for one or more of the plurality of FBGs and a change in a length of a dead zone of the optical fiber based on the comparison is also determined. From this, estimates of locations two or more of the plurality of FBG's are formed.

Disclosed herein are methods, apparatus, and systems for perturbing an optical beam propagating within a first length of fiber to adjust one or more beam characteristics of the optical beam in the first length of fiber or a second length of fiber or a combination thereof, coupling the perturbed optical beam into a second length of fiber and maintaining at least a portion of one or more adjusted beam characteristics within a second length of fiber having.

Air core optical fiber structures in which the cladding is composed of an engineered optical metamaterial having a refractive index less than unity for at least one specific wavelength band and provides for total internal reflection of optical energy between the air core and metamaterial cladding. According to certain examples, a method of guiding optical energy includes constructing a hollow core optical fiber with an all-dielectric optical metamaterial cladding, coupling optical energy into the optical fiber having an operating wavelength near a resonance of the metamaterial cladding, and guiding the optical energy within the hollow core optical fiber by total internal reflection.

Disclosed herein are methods, apparatus, and systems for providing an optical beam delivery system, comprising an optical fiber including a first length of fiber comprising a first RIP formed to enable, at least in part, modification of one or more beam characteristics of an optical beam by a perturbation assembly arranged to modify the one or more beam characteristics, the perturbation assembly coupled to the first length of fiber or integral with the first length of fiber, or a combination thereof and a second length of fiber coupled to the first length of fiber and having a second RIP formed to preserve at least a portion of the one or more beam characteristics of the optical beam modified by the perturbation assembly within one or more first confinement regions. The optical beam delivery system may include an optical system coupled to the second length of fiber including one or more free-space optics configured to receive and transmit an optical beam comprising the modified one or more beam characteristics.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50? C., preferably 50? C.<T.sub.h<250? C.

A microstructured optical fiber for generating supercontinuum light. The optical fiber includes a core and a cladding region surrounding the core. The optical fiber includes a first fiber length section, a second fiber length section as well as an intermediate fiber length section between said first and second fiber length sections. The first fiber length section has a core with a first characteristic core diameter larger than about 7 ?m. The second fiber length section has a core with a second characteristic core diameter, smaller than said first characteristic core diameter. The intermediate length section of the optical fiber includes a core which is tapered from said first characteristic core diameter to the second characteristic core diameter over a tapered length. Also, a supercontinuum light source including an optical fiber and a pump light source.

Air core optical fiber structures in which the cladding is composed of an engineered optical metamaterial having a refractive index less than unity for at least one specific wavelength band and provides for total internal reflection of optical energy between the air core and metamaterial cladding. According to certain examples, a method of guiding optical energy includes constructing a hollow core optical fiber with an all-dielectric optical metamaterial cladding, coupling optical energy into the optical fiber having an operating wavelength near a resonance of the metamaterial cladding, and guiding the optical energy within the hollow core optical fiber by total internal reflection.

A tapered waveguide is optically connected to an end surface of an optical fiber bundle part, and has a tapered part that changes in outside diameter in a tapered shape. The fiber bundle part is optically connected to the end surface of the large-diameter side of the waveguide. The entire waveguide has a substantially uniform index of refraction. A delivery fiber is optically connected to the end surface on the small-diameter side of the waveguide. As with the fiber bundle part the delivery fiber passes through a hole in a capillary and is affixed. The capillaries are each affixed to a retaining member such that the fiber bundle part, the waveguide, and the delivery fiber are disposed on the same axis and optically connected. The waveguide is retained in a state floating from the retaining member, and the outside surface of the waveguide is not in contact with the retaining member.

An illumination system generating light having at least one wavelength within 200 nm a plurality of nano-sized structures (e.g., voids). The optical fiber coupled to the light source. The light diffusing optical fiber has a core and a cladding. The plurality of nano-sized structures is situated either within said core or at a core-cladding boundary. The optical fiber also includes an outer surface. The optical fiber is configured to scatter guided light via the nano-sized structures away from the core and through the outer surface, to form a light-source fiber portion having a length that emits substantially uniform radiation over its length, said fiber having a scattering-in- duced attenuation greater than 50 dB/km for the wavelength(s) within 200 nm to 2000 nm range.

An Nd.sup.3+ optical fiber laser and amplifier operating in the wavelength range from 1300 to 1450 nm is described. The fiber includes a rare earth doped optical amplifier or laser operating within this wavelength band is based upon an optical fiber that guides light in this wavelength band. The waveguide structure attenuates light in the wavelength range from 850 nm to 950 nm and from 1050 nm to 1150 nm.