An easy-to-fabricate and highly efficient single-mode optical fiber-to-single-mode optical waveguide coupler having relatively large horizontal and vertical alignment tolerances between the fiber and the waveguide coupler. The waveguide coupler also features ease of end-facet cleaving. The waveguide coupler can be used in ultra-broadband high coupling efficiency applications or other suitable applications. Single-mode on-chip waveguides incorporating such coupler(s) are also provided, as are methods of manufacturing the waveguide coupler and on-chip waveguide.

An intravascular or other 2D or 3D imaging apparatus can include a minimally-invasive distal imaging guidewire portion. A plurality of thin optical fibers can be circumferentially distributed about a cylindrical guidewire core, such as in an spiral-wound or otherwise attached optical fiber ribbon. A low refractive index coating, high numerical aperture (NA) fiber, or other technique can be used to overcome challenges of using extremely thin optical fibers. Coating and ribbonizing techniques are described. Also described are non-uniform refractive index peak amplitudes or wavelengths techniques for FBG writing, using a depressed index optical cladding, chirping, a self-aligned connector, optical fiber routing and alignment techniques for a system connector, and an adapter for connecting to standard optical fiber coupling connectors.

The present invention relates to an apparatus for optical applications, a spectrometer system and method for producing an apparatus for optical applications, and in particular to an apparatus comprising an optical waveguide having a first refractive index along a light propagation axis interrupted by a plurality of scattering portions having a second refractive index. Each scattering portion has a long axis substantially perpendicular to the light propagation axis as well as a short axis substantially perpendicular to the light propagation axis and the long axis. A receiver unit or a transmitter unit is arranged on a side of the optical waveguide, the long axis being substantially perpendicular, i.e. normal to the plane of this side on which the receiver unit or transmitter unit is arranged. Accordingly, simplification and miniaturization of an optical apparatus can be realized.

Methods include, for each of a plurality of pluggable optical transceivers that are fiber-coupled to respective inputs of a passive wavelength division multiplexer having a predetermined loss profile defining a path specific loss between each input and a common output, sending an optical output signal along an optical signal path while the other optical transceivers of the plurality are not sending optical output signals and measuring an optical power of the sent optical output signal at an input of a local optical amplifier downstream from an output of the wavelength division multiplexer, wherein the local optical amplifier is configured to transmit the optical output signals to a distant location, and, based on the measured optical powers, determining a loss distribution across the optical output signals at the input of the local optical amplifier by subtracting the predetermined path specific losses of the wavelength division multiplexer, comparing a variation in the loss distribution to a nominal variation to determine a defect in a transceiver fiber path associated with a higher loss component of the distribution where the variation exceeds the nominal variation, comparing an average or maximum loss in the loss distribution to a nominal average or maximum allowable loss to determine a defect in a common fiber path downstream from the multiplexer, and adjusting one or more of the optical powers of the optical output signals produced by the optical transceivers before transmission through the multiplexer, by an optical power offset that produces a predetermined flat optical power spectrum profile at the input of the local optical amplifier and that increases a transmission distance over which the optical output signals decodably propagate.

Described are optical fibers, e.g., for use in stress-sensing or shape-sensing applications, that use overlapping grating configurations with chirped gratings to facilitate strain delay registration. In accordance with various embodiments, a fiber core may, for instance, have two overlapping sets of chirped gratings that differ in the direction of the chirp between the first and second sets, or a set of chirped gratings overlapping with a single-frequency grating. Also described are strain sensing systems and associated computational methods employing optical fibers with overlapping gratings.

Multi-clad optical fiber cladding light stripper (CLS) comprising an inner cladding with one or more recessed surface regions to remove light propagating within the inner cladding. A CLS may comprise such recessed surface regions along two or more azimuthal angles about the fiber axis, for example to improve stripping efficiency. One or more dimensions, or spatial distribution, of the recessed surface regions may be randomized, for example to improve stripping uniformity across a multiplicity of modes propagating within a cladding. Adjacent recessed surface regions may abut, for example, end-to-end, as segments of a recess that occupies a majority, or even an entirety, of the length of a fiber surrounded by a heat sink. One or more dimensions, or angular position, of individual ones of the abutted recessed surface regions may vary, according to a regular or irregular pattern.

The exemplary embodiments provide an optical fiber sensor and a vector measuring device which measure a motion of a subject using a double Bragg grating formed in a core with a helical structure and measure a chiral motion inflection point vector.

Example embodiments include an optical interrogation system with a sensing fiber having a single core, the single core having multiple light propagating modes. Interferometric apparatus probes the single core multimode sensing fiber over a range of predetermined wavelengths and detects measurement interferometric data associated with the multiple light propagating modes of the single core for each predetermined wavelength in the range. Data processing circuitry processes the measurement interferometric data associated with the multiple light propagating modes of the single core to determine one or more shape-sensing parameters of the sensing fiber from which the shape of the fiber in three dimensions can be determined.

Multi-clad optical fiber cladding light stripper (CLS) comprising an inner cladding with one or more recessed surface regions to remove light propagating within the inner cladding. A CLS may comprise such recessed surface regions along two or more azimuthal angles about the fiber axis, for example to improve stripping efficiency. One or more dimensions, or spatial distribution, of the recessed surface regions may be randomized, for example to improve stripping uniformity across a multiplicity of modes propagating within a cladding. Adjacent recessed surface regions may abut, for example, end-to-end, as segments of a recess that occupies a majority, or even an entirety, of the length of a fiber surrounded by a heat sink. One or more dimensions, or angular position, of individual ones of the abutted recessed surface regions may vary, according to a regular or irregular pattern.

The invention relates to a waveguide and a polarisation splitter based on said waveguide, in which a rotation of an angle greater than zero is applied to a plurality of sections of a core material and a plurality of sections of a covering material, thereby achieving an independent control of the refractive indices of a zero-order transverse electric mode and a zero-order transverse magnetic mode. This document also describes a manufacturing method of said waveguide which allows the birefringence of the light that passes through the waveguide.