An optical fiber amplifier comprising a first optical fiber, a second optical fiber, a third optical fiber, and an excitation light source, is disclosed. Each optical fiber has cores and a cladding surrounding the cores. The third optical fiber transmits excitation light used for signal amplification in the second optical fiber. A rare-earth element is doped to the second optical fiber that amplifies an optical signal propagating therein by the excitation light. The third optical fiber includes a reduced-diameter portion. A distance between the cores of the third optical fiber in the reduced-diameter portion is shorter than a distance between the cores in other portion of the third optical fiber, and the excitation light entering from the excitation light source to one of the cores of the third optical fiber is mode-coupled with another core of the third optical fiber to distribute the excitation light in the reduced-diameter portion.

A light source includes features configured to compensate for discontinuous solid state sources. The light source can produce a wide color gamut in display, and improved color rendering of tissue under observation by phosphor gap filling with colored LEDs. The light source can include provisions to depart from a white light spectrum to heighten differences in anatomical features or functions. The light source can include provisions to introduce narrow-band solid-state sources for producing false-color and pseudo-color images, with variable color rendering to change the power spectral distribution and to compensate for fiber optic length and fiber optic diameter tip sensing.

An optical connector includes: at least a ferrule and n self-forming optical waveguides, wherein the ferrule includes n optical fiber insertion holes, and optical fibers are each inserted into and included in the optical fiber insertion holes, the number n indicates a natural number not including zero, there are variations in an angle of each optical fiber in a core axial direction and a core gap between adjacent ones of the optical fibers, an end surface of the ferrule is formed with roundness, and end portions of the self-forming optical waveguides are each optically connected to the optical fibers.

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.

An apparatus includes an optical gain fiber having a core, a cladding surrounding the core, the core and cladding defining an optical gain fiber numerical aperture, and a multimode fiber having a core with a larger radius than a radius of the optical gain fiber core, a cladding surrounding the core, the core and cladding of the multimode fiber defining a multimode fiber stable numerical aperture that is larger than the optical gain fiber numerical aperture, the multimode fiber being optically coupled to the optical gain fiber so as to receive an optical beam propagating in the optical gain fiber and to stably propagate the received optical beam in the multimode fiber core with low optical loss associated with the optical coupling.

An optical fiber fuse protection device includes an upstream optical fiber disposed on an upstream side, a downstream optical fiber disposed on a downstream side, and a wall interposed between a part of the upstream optical fiber and a part of the downstream optical fiber. The downstream optical fiber is fusion-spliced to the upstream optical fiber and is made of a single optical fiber or a plurality of optical fibers fusion-spliced to each other.

An optical input/output device includes: one or more multicore fibers each comprising one or more transmitting cores and one or more receiving cores; first transmitting single-core fibers whose number is equal to a total number of the transmitting cores; first receiving single-core fibers whose number is equal to a total number of the receiving cores in all the multicore fibers; a fan-in/fan-out device that optically couples each core of the first transmitting single-core fibers and each of the transmitting cores at one end of a respective one of the first transmitting single-core fibers, and optically couples each of the first receiving single-core fibers and each of the receiving cores at one end of a respective one of the first receiving single-core fibers; and a transmission/reception connector comprising connector ports whose number is equal to a total number of the first transmitting single-core fibers and the first receiving single-core fibers.

An in-plane photonic device is provided for transmission of an optical signal across a gap, in particular an in-plane photonic device for use in a photonic integrated circuit with one or more in-plane crossings of electrical connections and photonic waveguides. One embodiment relates to an in-plane photonic device for use in a photonic integrated circuit with in-plane crossings of electrical connections and photonic waveguides, including: at least one input optical waveguide; and at least one output optical waveguide; wherein the at least one input optical waveguide and the at least one output optical waveguides are positioned such that a gap between them separates the input and the output optical waveguide(s), and wherein the input and the output optical waveguides are configured for optical mode matching across the gap, such that an optical signal can be transmitted from the input optical waveguide to the output optical waveguide across the gap.

An optical connection structure includes a first spatial multiplex transmission line, a second spatial multiplex transmission line, a first lens arrangement, a second lens arrangement and a first beam diameter conversion portion. The first spatial multiplex transmission line has a plurality of first transmission lines. The second spatial multiplex transmission line has a plurality of second transmission lines. The first lens arrangement is optically coupled with the first spatial multiplex transmission line. The second lens arrangement is optically coupled with the second spatial multiplex transmission line. The first beam diameter conversion portion has a first end face and a second end face and arranged between the first spatial multiplex transmission line and the first lens arrangement. The first beam diameter conversion portion is configured such that an optical diameter at the second end face is larger than an optical diameter at the first end face.

Passive optical couplers having passive optical activity indicators and methods of operating the same are disclosed. An example passive optical coupler for passively coupling first and second optical fibers includes a housing including: a first port configured to receive an end of a first optical fiber, and a second port configured to receive an end of a second optical fiber; and a passive optical activity indicator positioned at least partially within the housing, wherein a first portion of the passive optical activity indicator is exposed through the housing, and wherein the passive optical activity indicator is configured to passively illuminate in response to (i) first light propagating in the first optical fiber when the end of the first optical fiber is received in the first port, and (ii) second light propagating in the second optical fiber when the end of the second optical fiber is received in the second port.