A distributed acoustic system (DAS) may comprise an interrogator and an umbilical line attached at one end to the interrogator, a downhole fiber attached to the umbilical line at the end opposite the interrogator. The interrogator may further include a proximal circulator, a distal circulator connected to the proximal circulator by a first fiber optic cable, and a second fiber optic cable connecting the proximal circulator and the distal circulator.

The present disclosure generally pertains to systems and methods that utilize optical frequency discriminators based on fiber Bragg gratings. In some embodiments, an optical frequency discriminator has a polarization-maintaining fiber Bragg grating (PM-FBG), and an incoming polarized optical signal is reflected from the PM-FBG, which differentiates the two polarization modes in the incoming signal according its frequency relative to the two resonance peaks of the PM-FBG. The optical frequency discriminator then compares (e.g., subtracts) the reflected power in the two polarization modes to provide an output having an amplitude that varies linearly with the frequency of the incoming signal. This output may then be used to extract various information about the frequency of the incoming signal. As an example, the output may be used to recover data that has been frequency modulated onto the incoming signal or to characterize the frequency noise of the incoming signal.

A cassette for optical fiber includes one or more optical sensors. The cassette has a spool for handling optical fiber. An adjustable shaft is disposed such that the spool is configured to rotate about the adjustable shaft. The adjustable shaft is configured to handle spools having different diameters. A spool controller is coupled to the adjustable shaft and configured to rotate the adjustable shaft to perform one or more of extract and retract the optical fiber. One or more bushings are disposed proximate the spool and are configured to prevent the optical fiber from jumping off the spool.

Improvements to gratings for use in waveguides and methods of producing them are described herein. Deep surface relief gratings (SRGs) may offer many advantages over conventional SRGs and Bragg gratings, an important one being a higher S-diffraction efficiency. In one embodiment, deep SRGs can be implemented as polymer surface relief gratings or evacuated Bragg gratings (EBGs). EBGs can be formed by first recording a holographic polymer dispersed liquid crystal (HPDLC) grating. Removing the liquid crystal from the cured grating provides a polymer surface relief grating. Polymer surface relief gratings have many applications including for use in waveguide-based displays.

An optical fiber including a plurality of embedded optical reflectors distributed periodically along the length of the fiber and a method of quantifying loss associated with an optical connector that is connected to optical fiber comprising a plurality of embedded optical reflectors distributed periodically along the length of the fiber. The method includes inserting an optical signal into the fiber through the optical connector; measuring a component of the optical signal reflected by at least one of the plurality of embedded optical reflectors, in which the component is received through the optical connector; calculating the difference in power level between the inserted and reflected signals; and quantifying, based on the calculated power level difference and the reflectivity of the embedded optical reflector, the loss associated with the optical connector.

Multiplexed reflection and transmission gratings, and methods of their manufacture, are provided that improve uniformity with laser light, that is, reduced banding and other illumination artifacts occurring in waveguides. The mechanism for this can be the multiple reflections between the waveguide reflecting surfaces and the reflection hologram, which promote illumination averaging as beam propagation processes within a waveguide. In some gratings, a beam splitter layer overlapping the multiplexed gratings can be provided for the purposes of reducing banding in a laser-illuminated waveguide. The beam splitter can be provided by one or more dielectric layers. The beamsplitter can have sensitivity to one polarization. The beamsplitter can be sensitive to S-polarization. The beam splitter can be an anti-reflection coating optimized for normal incidence that becomes reflective at high TIR angles when immersed in glass or plastic.

A device includes a waveguide, an in-coupling element, and an out-coupling element coupled with the waveguide. The waveguide, the in-coupling element, and the out-coupling element are configured to deliver a plurality of portions of an image light to an eye-box of the device. At least one of the in-coupling element or the out-coupling element includes a polarization selective diffractive element. The polarization selective diffractive element includes a grating including a plurality of microstructures defining a plurality of grooves filled with a passive optically anisotropic material having a first effective refractive index along a groove direction of the grooves and a second effective refractive index along an in-plane direction perpendicular to the groove direction. One of the first effective refractive index or the second effective refractive index substantially matches with a refractive index of the microstructures.

An optical waveguide-transmitter apparatus, an ultrasonic transceiver apparatus, an ultrasonic imaging apparatus and an associated production method are disclosed. The optical waveguide-transmitter apparatus includes a substrate made of a semiconductor material; a carrier layer arranged on the substrate; and at least one transmitter-optical waveguide made of a semiconductor material with a refractive index greater than a refractive index of the carrier layer. At least one side of the waveguide is at least partially surrounded by the carrier layer. The waveguide is configured at an end facing toward the examination region for a decoupling of the light beams into the examination region for generating the ultrasonic waves in the examination region by way of the decoupled light beams for an optoacoustic imaging and/or has, on the end facing toward the examination region, an optical absorption layer for such a conversion of the light beams.

There is provided a projection display device comprising: a light source, an SBG device comprising a multiplicity of separately SBG elements sandwich between transparent substrate to which transparent electrodes have been applied. The substrates function as a light guide. A least one transparent electrode comprises plurality of independently switchable transparent electrodes elements, each electrode element substantially overlaying a unique SBG element. Each SBG element encodes image information to be projected on an image surface. Light coupled into the light guide, undergoes total internal reflection until diffracted out to the light guide by an activated SBG element. The SBG diffracts light out of the light guide to form an image region on an image surface when subjected to an applied voltage via said transparent electrodes.

An optical apparatus (200) includes an outer jacket (230), common cladding (220), and multiple single mode fiber cores (210). The common cladding (220) is within the outer jacket (230) and is used as multimode fiber such that the outer jacket (230) clads the common cladding (220). The single mode fiber cores (210) are within the common cladding (220) such that the common cladding (220) clads the plurality of single mode fiber cores (210).