The selection of starting materials used in the process of forming an MCR is controlled to specifically define the physical properties of the core tube and/or the capillary tubes in the local vicinity of the core tube. The physical properties are considered to include, but are not limited to, the diameter of a given tube/capillary, its wall thickness, and its geometry (e.g., circular, non-circular). A goal is to select starting materials with physical properties that yield a final hollow core optical fiber with a “uniform” core region (for the purposes of the present invention, a “uniform” core region is one where the struts of cladding periodic array surrounding the central core are uniform in length and thickness (with the nodes between the struts thus being uniformly spaced apart), which yields a core wall of essentially uniform thickness and circularity.

Disclosed is an ultralow loss hollow-core antiresonant fiber, which includes an outer layer structure, a hollow-core area and a plurality of closed cavities. The radial section of the inner surface of the outer layer structure is a circle with a first radius. In the circumferential direction of the inner surface of the outer layer structure, the plurality of the closed cavities are spaced from one another and are distributed uniformly and circumferentially. Each closed cavity includes: an outermost wall serving as a first thin wall, and the radial section of the outermost wall is a fan shape or a circle with a second radius. Each closed cavity further includes: second thin walls located in the inner space surrounded by the inner surface of the outermost wall, and the end surfaces of the second thin walls are annular thin-walled structures with thin-walled spacers arranged in the centers.

A preform (10) for an antiresonant hollow core optical fibre comprises an outer jacket tube (12) having an inner surface and a central longitudinal axis (24); a plurality of antiresonant cladding tubes (14) spaced apart at predefined peripheral locations around the inner surface of the outer jacket tube (12), each antiresonant cladding tube (14) in contact with the inner surface such that a central longitudinal axis (26) of each antiresonant cladding tube (14) is at a first radial distance from the central longitudinal axis (24) of the outer jacket tube (12); and a plurality of spacing elements (22) disposed alternately with the antiresonant cladding tubes (14) and each in contact with an outer surface of each of two adjacent antiresonant cladding tubes (14) at one or more contact points (28), the contact points (28) at a second radial distance from the central longitudinal axis (24) of the outer jacket tube (12), the second radial distance being greater than the first radial distance.

A photonic crystal fiber (PCF) assembly including a PCF and at least one ferrule structure. The PCF includes a core region and a cladding region and a first fiber end section with a first fiber end. The ferrule structure is mounted to the first fiber end section. The ferrule structure includes an inner ferrule arrangement and an outer ferrule arrangement surrounding the first fiber end section. The inner ferrule arrangement includes an inner ferrule front section proximally to the first fiber end and an inner ferrule rear section distally to the first fiber end, and each of the sections has an inner diameter and in at least a length thereof fully surrounds the PCF. The inner ferrule rear section is anchored in an anchor length section to the first fiber end section and the inner ferrule front section supports the first fiber end section proximally to the first fiber end.

Multicore fibers and endoscope configurations are provided, along with corresponding production and usage methods. Various configurations include an adiabatically tapered proximal fiber tip and/or proximal optical elements for improving the interface between the multicore fiber and the sensor, photonic crystal fiber configurations which reduce the attenuation along the fiber, image processing methods and jointed rigid links configurations for the endoscope which reduce attenuation while maintaining required flexibility and optical fidelity. Various configurations include spectral multiplexing approaches, which increase the information content of the radiation delivered through the fibers and endoscope, and configurations which improve image quality, enhance the field of view, provide longitudinal information. Various configurations include fiber-based wave-front sensors. Many of the disclosed configurations increase the imaging resolution and enable integration of additional modes of operation while maintain the endoscope very thin, such as spectral imaging and three dimensional imaging.

A device for connecting a fiber preform including a plurality of elongate holes extending substantially parallel to a longitudinal axis of the fiber preform to a pressure supply system, the device including a first surface to be connected to an end face of the fiber preform where the plurality of elongate holes end, a second surface including at least two ports configured to be in fluid connection with the pressure supply system, and a channel system within the device connecting the plurality of elongate holes at the first surface to the at least two ports, wherein a density of the at least two ports at the second surface is smaller than a density of the plurality of corresponding elongate holes at the first surface.

A terminated hollow-core optical fiber includes an outer capillary having an end-face, a hollow-core optical fiber having a fiber-end located inside the outer capillary a non-zero distance away from the end-face of the outer capillary, a fiber jacket disposed on a surface of the hollow-core optical fiber, and an inner capillary disposed between the fiber jacket and an inner surface of the outer capillary. The inner capillary holds the hollow-core optical fiber via the fiber jacket such that the fiber-end protrudes from the inner capillary and is suspended inside the outer capillary. The terminated hollow-core optical fiber further includes an endcap adjacent the end-face of the outer capillary. This configuration positions the sensitive and potentially fragile fiber-end close to the endcap in a protected environment, while avoiding direct contact between the fiber-end and other mechanical structures, and can be realized without fusing anything to the light-transmitting surfaces of the endcap.

According to embodiments of the present invention, a fiber preform or an optical fiber is provided. The fiber preform or the optical fiber includes a core region having a plurality of cores, wherein two cores of the plurality of cores are bridged by an air gap, and a cladding arrangement including a first cladding region having a plurality of structures surrounding the core region, and a second cladding region in between the core region and the first cladding region, the second cladding region having a plurality of tubes, wherein at least one split is defined in the second cladding region. According to further embodiments of the present invention, a method for forming the fiber preform, a method for forming the optical fiber, an optical coupler having the optical fiber, an optical combiner having the optical fiber, and an optical apparatus having the optical fiber are also provided.

The present disclosure provides a preparation method of an optical fiber device having a polymer micronano structure integrated in an optical fiber, the method comprising: welding a hollow optical fiber so that the hollow optical fiber is welded between two solid optical fibers, ablating the welded hollow optical fiber utilizing a femtosecond laser ablation technology so that a channel vertical to an inner wall is ablated on the hollow optical fiber, filling a colorless and transparent liquid photoresist material inside the hollow optical fiber which has been ablated so that the inside of the hollow optical fiber is filled with the photoresist material, and polymerizing on the photoresist material inside the hollow optical fiber utilizing a femtosecond laser two-photon polymerization technology.

A method of processing an out-coupling end of a hollow core fiber including a plurality of anti-resonance elements surrounding a hollow core, and a hollow core fiber having been so processed. The method may include performing a tapering step to form a taper in the anti-resonance elements; performing a cleaving step at the taper to form at least one tapered out-coupling end of the hollow core fiber; and performing an end processing step including further heating the out-coupling end in a controlled manner to smoothen the out-coupling end.