Structures for an edge coupler and methods of fabricating a structure for an edge coupler. A first waveguide core has a first section that has a tapered shape and a second section that is adjoined to the first section. Multiple segments are positioned with a spaced arrangement adjacent to an end surface of the second section of the first waveguide core. A slab layer is adjoined to the first section of the first waveguide core. A second waveguide core has a section that overlaps with the first section of the first waveguide core to define a layer stack. The section of the second waveguide core has a tapered shape, and the first and second waveguide cores are comprised of different materials. The first section of the first waveguide core has a first thickness, and the slab layer has a second thickness that is less than the first thickness.

A method of processing by controlling one or more beam characteristics of an optical beam may include: launching the optical beam into a first length of fiber having a first refractive-index profile (RIP); coupling the optical beam from the first length of fiber into a second length of fiber having a second RIP and one or more confinement regions; modifying the one or more beam characteristics of the optical beam in the first length of fiber, in the second length of fiber, or in the first and second lengths of fiber; confining the modified one or more beam characteristics of the optical beam within the one or more confinement regions of the second length of fiber; and/or generating an output beam, having the modified one or more beam characteristics of the optical beam, from the second length of fiber. The first RIP may differ from the second RIP.

A method of processing by controlling one or more beam characteristics of an optical beam may include: launching the optical beam into a first length of fiber having a first refractive-index profile (RIP); coupling the optical beam from the first length of fiber into a second length of fiber having a second RIP and one or more confinement regions; modifying the one or more beam characteristics of the optical beam in the first length of fiber, in the second length of fiber, or in the first and second lengths of fiber; confining the modified one or more beam characteristics of the optical beam within the one or more confinement regions of the second length of fiber; and/or generating an output beam, having the modified one or more beam characteristics of the optical beam, from the second length of fiber. The first RIP may differ from the second RIP.

An optical filter comprising a first lens, and first and second optical elements. The first lens has an optical axis, configured to focus beams propagating parallel to the optical axis at a focal point. The first optical element has a first semi-reflective surface, the first semi-reflective surface being curved and having a first radius of curvature around a first centre of curvature on the optical axis. The second optical element has a second semi-reflective surface. The first radius of curvature is between 1 and 10,000 times the distance between the first semi reflective surface and the focal point along the optical axis. The first and second semi-reflective surfaces are arranged to form a resonator. The first lens and the first and second semi-reflective surfaces are arranged along the optical axis such that light is transmittable along an optical path through the lens and the resonator. The optical filter further comprises one or more expansion elements located outside of the optical path, and arranged such that expansion of the expansion elements causes relative movement of the first and second semi-reflective surfaces.

A first multimode optical fiber carries a mode division multiplexed (MDM) optical signal. The MDM optical signal is transmitted into a second multimode fiber from the first multimode optical fiber. The first and second multimode fibers are coupled via a fiber connector. The lateral offset between the two fibers at the connector is less than 2 μm.

A first multimode optical fiber carries a mode division multiplexed (MDM) optical signal. The MDM optical signal is transmitted into a second multimode fiber from the first multimode optical fiber. The first and second multimode fibers are coupled via a fiber connector. The lateral offset between the two fibers at the connector is less than 2 μm.

The present invention relates to a glass fiber (1) comprising at least one fiber core (10), at least one fiber cladding (11) which at least substantially encloses the fiber core (10) in the circumferential direction (U) and along the longitudinal axis (X), and at least one fiber coating (12) which substantially encloses the fiber cladding (11) in the circumferential direction (U) and along the longitudinal axis (X), wherein the glass fiber (1) has at least one first exposed portion (13a) where the fiber cladding (11) is exposed by the fiber coating (12), for removing light (B) at least from the fiber cladding (11), wherein at least the fiber cladding (11) has a plurality of recesses (14) at least substantially in the radial direction (R), which recesses are designed to at least partially discharge the light (B) at least from the fiber cladding (11). The glass fiber (1) is characterized in that the recesses (14), as longitudinal recesses (14), are each formed at least in portions precisely along the longitudinal axis (X).

Embodiments are disclosed for a coupling element with embedded modal filtering for a laser and/or a photodiode. An example system includes a laser and an optical coupling element. The laser is configured to emit an optical signal. The optical coupling element is configured to receive the optical signal emitted by the laser. The optical coupling element is also configured to be connected to an optical fiber such that, in operation, the optical signal is transmitted from the laser to the optical fiber via the optical coupling element. Furthermore, the coupling element comprises a tapered section that provides modal filtering of the optical signal.

Embodiments are disclosed for a coupling element with embedded modal filtering for a laser and/or a photodiode. An example system includes a laser and an optical coupling element. The laser is configured to emit an optical signal. The optical coupling element is configured to receive the optical signal emitted by the laser. The optical coupling element is also configured to be connected to an optical fiber such that, in operation, the optical signal is transmitted from the laser to the optical fiber via the optical coupling element. Furthermore, the coupling element comprises a tapered section that provides modal filtering of the optical signal.

The present disclosure provides a polarization attenuator and a polarization attenuation method to solve the problem of polarization dependent loss of optical devices, or to be used in optical devices or systems as a polarizer structure. The polarization attenuator comprises a first main waveguide, an offset waveguide and a second main waveguide which are arranged in sequence, wherein an output surface of the first main waveguide partially overlaps an input surface of the offset waveguide; an output surface of the offset waveguide partially overlaps an input surface of the second main waveguide; the first main waveguide or the second main waveguide supports fundamental modes and supports at least one high order mode. Meanwhile, the present disclosure further provides the polarization attenuation method comprising following steps: 1) optical signals enter the first main waveguide; 2) the optical signals excite high order modes at a joint of the first main waveguide and the offset waveguide; and 3) the signals are mixed again at a joint of the second main waveguide and the offset waveguide, and power between a fundamental mode and high order modes of the offset waveguide is redistributed between the fundamental mode and the high order mode of the second main waveguide.