Example embodiments include an optical assembly for an optical interrogation system having a single core or a multicore sensing fiber, a measurement fiber to couple light into the sensing fiber, and a reference fiber arranged with the measurement fiber as part of an optical interferometer. A beam splitter combines light from the sensing fiber and with light from the reference fiber. A polarization beam splitting prism separates the combined light into first polarized light and second polarized light that is orthogonal to the first polarized light. The optical assembly can substantially reduce the size, complexity, or cost associated with the traditional optical components in an optical interrogation system that it replaces. Other example optical assemblies are described. Embodiments describe optical interrogation systems using the example optical assemblies.

A semi-translucent photovoltaic device is described having a translucent substrate with a photovoltaic stack interrupted in spatially distributed openings filled with a translucent polymer. Also disclosed is a method of manufacturing the device. The method comprises providing the substrate at a first side with the photovoltaic stack; removing material from the stack in spatially distributed regions, therewith forming openings within these regions; blanket-wise depositing a protective layer over the substrate with the photovoltaic stack; blanket-wise depositing a layer of a radiation-curable precursor for the translucent polymer over the protective layer; irradiating the substrate from a second side opposite its first side to therewith selectively cure the radiation-curable precursor within and in front of the spatially distributed openings, the radiation-curable precursor being converted therewith into said translucent polymer; removing an uncured remainder of the layer of the radiation-curable precursor.

Systems and methods for bondline inspection using mechanical wave measurement and gas excitation. A cost-effective optical interferometry technique is used to measure mechanical waves generated by gas excitation, which measurements may be used to verify the strength of a bondline of a composite bonded structure. A gas gun which produces a high-pressure short-pulsewidth gas pulse at the front free surface of the composite material. A velocity interferometer system for any reflector (VISAR) is synchronized with the controlled gas pulsation and used to measure the surface velocities. The respective shock wave-induced displacements of the back and front free surfaces are then calculated. The measured free surface displacements are compared with calibrated thresholds to determine whether a weak bond has been detected or not. Optionally, a ring magnet is aligned exactly under the gas gun nozzle to enable VISAR beam centering.

A composed multicore optical fiber (MCF) device includes a first segment (MCF1) of a MCF having three coupled identical cores and having a first length (L1) and a second segment (MCF2) of the same MCF having a second length (L2). L1 and L2 are different from each other. One of the three coupled cores is located in a geometrical centre of the MCF. The first segment (MCF1) and the second segment (MCF2) of the MCF are rotated 180° relative to each other and spliced together. The first segment (MCF1) is spliced to a first segment (SMF1) of a single mode fiber (SMF) and the second segment (MCF2) is spliced to a second segment (SMF2) of the SMF. The free end of the second segment (SMF2) of the SMF is coupled to a mirror (M) to reflect an optical signal coming from the first segment (SMF1) of the SMF.

Processes for rapidly and accurately measuring the coefficient of moisture expansion for materials, such as adhesives, are disclosed. A replication technique may be used to manufacture highly flat and smooth adhesive samples. Moisture is introduced in a controlled humidity atmosphere, distortion is monitored with an accurate laser interferometer (e.g., ˜1 nanometer (nm) accuracy), and measurements are correlated with moisture content change. Such processes decrease sample size by three orders of magnitude as compared with conventional techniques and have a smaller adhesive mass requirement, which enables measurement of expensive microelectronic adhesives that were previously cost-prohibitive to measure. Also, thinner films allow CME measurements of ultraviolet (UV) cured adhesives that would otherwise have depth of penetration issues. Furthermore, saturation occurs quickly, allowing pre-stabilization at room temperature, which enabled parametric studies as a function of processing or cure state. Additionally, testing occurs within hours versus months, enabling short lead times for root-cause investigations.

There is described a method for interrogating optical fiber comprising fiber Bragg gratings (“FBGs”), using an optical fiber interrogator. The method comprises (a) generating an initial light pulse from phase coherent light emitted from a light source, wherein the initial light pulse is generated by modulating the intensity of the light; (b) splitting the initial light pulse into a pair of light pulses; (c) causing one of the light pulses to be delayed relative to the other of the light pulses; (d) transmitting the light pulses along the optical fiber; (e) receiving reflections of the light pulses off the FBGs; and (f) determining whether an optical path length between the FBGs has changed from an interference pattern resulting from the reflections of the light pulses.

Analysis of residual stress in materials is often done in static conditions in a laboratory. Accurate systems and methods for performing these analyses in a dynamic, non-laboratory environment are notoriously difficult and can be very inaccurate. A method using a portable, field deployable apparatus having greater accuracy than currently available is disclosed whereby accurate and repeatable residual stress analysis may be implemented in non-laboratory environments leading to greatly improved diagnostics, maintenance and life limit prediction. Especially the analysis of a pipe or channel can be facilitated with this invention.

An optical fiber sensor includes an optical fiber. The optical fiber includes a cladding having a cladding refractive index, and a plurality of fiber cores embedded in the cladding and extending along a longitudinal axis of the optical fiber. The plurality of fiber cores include a first subset of at least one first fiber core and a second subset of at least one second fiber core. The at least one first fiber core has a first core refractive index different from the cladding refractive index and a first core radius in a direction transverse to the longitudinal axis. The at least one second fiber core has a second core refractive index different from the cladding refractive index and a second core radius transverse to the longitudinal axis. The second core refractive index and the second core radius differ from the first core refractive index and the first core radius such that a temperature sensitivity of the at least one second fiber core differs from the temperature sensitivity of the first fiber core.

Disclosed herein are electronic devices having touch input surfaces. A user's touch input or press on the touch input surface is detected using a set of lasers, such as vertical-cavity surface-emitting lasers (VCSELs) that emit beams of light toward the touch input surface. The user's touch causes changes in the self-mixing interference within the VCSEL of the emitted light with reflected light, such as from the touch input surface. Deflection and movement (e.g., drag motion) of the user's touch is determined from detected changes in the VCSELs' operation due to the self-mixing interference.

Disclosed herein are wearable devices, their configurations, and methods of operation that use self-mixing interferometry signals of a self-mixing interferometry sensor to recognize user inputs. The user inputs may include voiced commands or silent gesture commands. The devices may be wearable on the user's head, with the self-mixing interferometry sensor configured to direct a beam of light toward a location on the user's head. Skin deformations or vibrations at the location may be caused by the user's speech or the user's silent gestures and recognized using the self-mixing interferometry signal. The self-mixing interferometry signals may be used for bioauthentication and/or audio conditioning of received sound or voice inputs to a microphone.