Optical fiber filters and uses thereof are presented. In typical implementations, there is provided a FBG taking deleterious light out of a fiber core without reflecting it into the fiber core. It also allows the unhindered transmission of useful light at a wavelength outside of the spectral band covered by the deleterious light. The filter couples the incoming deleterious light to cladding modes propagating in the opposite direction without coupling the incoming useful light to core or cladding modes propagating in the opposite direction. The filter may for example be useful as a Raman or ASE filter in a laser cavity of other optical devices.

Embodiments of the invention comprise apparatus and methods for detecting the presence of a substance in a test material using a plurality of wavelength-specific couplers (e.g. tilted fibre gratings) which provide a spatially distributed multi-node all-optical measurement system. Each node of the measurement system can comprise an optical module that is sensitive to the intensity of a limited band of wavelengths. The node is thus capable of detecting the presence of an absorption peak in a spectrum without having to obtain the full spectrum. By providing a plurality of optical modules that are sensitive to different wavelengths, the spectral signature of different substances may be monitored without having to measure full spectra. The measurement system may be particularly useful in a process control environment where it is desirable to take measurements of one or more substances in different locations.

A waveguide structure is provided. A silicon substrate layer, a silicon waveguide layer, a first silicon dioxide layer, a silicide waveguide layer, and a second silicon dioxide layer are stacked in sequence, the silicon waveguide layer is a conical waveguide layer, the silicon waveguide layer and the silicide waveguide layer are coupled by using an evanescent wave, the silicide waveguide layer includes multiple first waveguide blocks and multiple second waveguide blocks, a material of the first waveguide blocks is the same as a material of the silicide waveguide layer, and a refractive index of a material of the second waveguide blocks is lower than a refractive index of the material of the first waveguide blocks. By using the waveguide structure, a waveguide flare size can be increased, so as to match a mode size of a fiber core of an optical fiber.

The present disclosure provides a pitch reducing optical fiber array or a multicore fiber including at least one chiral fiber grating incorporated therein that is operable to couple the modes in different fiber cores within a spectral range determined in some instances by the helical pitch of the corresponding chiral fiber grating.

An optical sensor includes an optical fiber inscribed with a repeated refraction pattern such that light scattered from a location on the optical fiber is scattered at multiple frequencies in a range of frequencies. The inscribed patterns overlap at every measurement point along at least a portion of the length of the sensor. An optical sensing system including control circuitry coupled to the optical fiber detects measurement scatter data from the optical fiber over the range of frequencies, determines a change in the detected measurement scatter data over the range of frequencies, and extracts a parameter describing a state of the optical fiber from the determined change in the detected measurement scatter data. The sensor may be made by inscribing a first light refracting pattern on the optical fiber at every measurement point along at least a portion of the length of the sensor and inscribing a second light refracting pattern on the optical fiber that overlaps the first inscribed light refracting pattern at every measurement point along at least that portion of the length of the sensor.

A transparent waveguide for use in eye tracking includes an input-coupler and an output-coupler. The input-coupler comprises a plurality of curved grating lines having a radially varying pitch. When positioned in front of an eye illuminated with infrared light, infrared light beams reflected from the eye and incident on the input-coupler enter the waveguide at the input-coupler, propagate through the waveguide by way of total internal reflections, and exit the waveguide proximate the output-coupler. The radially varying pitch of the curved grating lines of the input-coupler provides angular encoding of infrared light incident on the input-coupler, and more specifically, causes different beams of infrared light incident on respective different horizontal and vertical positions of the input-coupler to propagate through the waveguide at respective different angles of reflection and exit the waveguide at respective different angles of incidence relative to a surface of the waveguide through which infrared light beams exit.

An eyepiece waveguide for an augmented reality. The eyepiece waveguide can include a transparent substrate with an input coupler region, a first orthogonal pupil expander (OPE) region, and an exit pupil expander (EPE) region. The input coupler region can couple an input light beam that is externally incident on the input coupler region into at least a first guided light beam that propagates inside the substrate. The first OPE region can divide the first guided beam into a plurality of replicated, spaced-apart beams. The EPE region can re-direct the replicated beams from the first OPE region such that they exit the substrate. The EPE region can have an amount of optical power.

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.

An eyepiece for an augmented reality display system. The eyepiece can include a waveguide substrate. The waveguide substrate can include an input coupler grating (ICG), an orthogonal pupil expander (OPE) grating, a spreader grating, and an exit pupil expander (EPE) grating. The ICG can couple at least one input light beam into at least a first guided light beam that propagates inside the waveguide substrate. The OPE grating can divide the first guided light beam into a plurality of parallel, spaced-apart light beams. The spreader grating can receive the light beams from the OPE grating and spread their distribution. The spreader grating can include diffractive features oriented at approximately 90° to diffractive features of the OPE grating. The EPE grating can re-direct the light beams from the first OPE grating and the first spreader grating such that they exit the waveguide substrate.

In accordance with an embodiment, a bandpass transmission filter having a center wavelength of transmission includes: a waveguide structure comprising a grating structure having changing grating pitch values configured to diffract radiation in the waveguide structure having a first wavelength lower than the center wavelength of transmission, and configured to reflect radiation in the waveguide structure having a second wavelength higher than the center wavelength of transmission; and a radiation absorbing structure configured to absorb radiation guided by the waveguide structure having a third wavelength higher than the second wavelength, wherein the radiation absorbing structure is an integrated part of the waveguide structure or comprises a layer arranged adjacent to the waveguide structure.