An optical system performs a method for measuring an acoustic signal in a wellbore. The optical system includes a light source, an optical fiber and a detector. The light source generates a light pulse. The optical fiber has a first end for receiving the light pulse from the light source and a plurality of enhancement scatterers spaced along a length of the optical fiber for reflecting the light pulse. A longitudinal density of the enhancement scatterers increases with a distance from the first end to increase a signal enhancement generated by the enhancement scatterers distal from the first end. The detector is at the first end of the optical fiber and measures a reflection of the light pulse at the enhancement scatterers to determine the acoustic signal.

The disclosed embodiments generally relate to extruding multiple layers of micro- to nano-polymer layers in a tubular shape. In particular, the aspects of the disclosed embodiments are directed to a method for producing a Bragg reflector comprising co-extrusion of micro- to nano-polymer layers in a tubular shape.

A distributed device for the detection of a substance is disclosed, comprising: a distributed optical excitation source (21) including a first optical fiber (22) having a plurality of extraction regions (24), each extraction region (24) being adapted to extract part of the light carried by the first optical fiber (22) from said fiber; and a distributed acoustic sensor (25) including a second optical fiber (26).

There is described a method of fabricating an optical fiber device, the method comprising: positioning longitudinal portions of a plurality of optical fibers alongside each other in a given geometrical relationship, depositing liquid coating material around the longitudinal portions of the plurality of optical fibers; and the liquid coating material setting up around the longitudinal portions of the plurality of optical fibers thereby maintaining said given geometrical relationship along the longitudinal portions.

A curvature sensor includes a light source, a flexible light guide including cores, and FBG sensors that are provided in the cores and constitute FBG sensor groups at predetermined positions at predetermined positions along longitudinal axes of the cores. The curvature sensor includes a detector that detects an optical spectrum of light from the FBG sensors, and a processor that obtains a bend of the light guide. FBG sensors provided in a core include a first FBG sensor and a second FBG sensor next to it. The first and second FBG sensors include gratings having first and second pitches. The first pitch is shorter than the second pitch and is closer to the second pitch than other pitches of gratings of all FBG sensors that are provided in the core and include gratings having pitches shorter than the second pitch.

A lighting unit includes a single core optical fiber, a light converter, and an exit end. The single core optical fiber includes an incident end and a distal end, and is configured to guide primary light, which is a laser light incident on the incident end, to the distal end. The light converter is formed inside the optical fiber, and is configured to receive the primary light guided by the optical fiber, convert optical properties of at least part of the received primary light and generate secondary light. The exit end is arranged at the distal end of the optical fiber, and is configured to emit the secondary light externally as illumination light.

In various embodiments, wavelength beam combining laser systems incorporate optical cross-coupling mitigation systems and/or engineered partially reflective output couplers in order to reduce or substantially eliminate unwanted back-reflection of stray light.

An optical fiber made of silica glass includes a core having a maximum refractive index n1, a depressed portion surrounding the core and having an average refractive index n2, and cladding surrounding the depressed portion and having an average refractive index n3. In the optical fiber, n1>n3>n2. The optical fiber has a local maximum value of chromatic dispersion within a wavelength range of 1530 nm to 1610 nm, and the local maximum value is 2 ps/nm/km or greater and below 0 ps/nm/km.

An optoelectronic device (20, 50) includes a planar substrate (30), an optical bus (40, 82, 84, 96, 140, 150, 180, 182, 224) disposed on the substrate and configured to convey coherent radiation through the bus, and an array (32, 72) of sensing cells (34, 74, 90, 160, 170, 200, 212, 380) disposed on the substrate. Each sensing cell includes at least one tap (92, 94, 144, 146, 226, 228) coupled to extract a portion of the coherent radiation propagating through the optical bus, an optical transducer (36, 108, 162, 172, 202, 204, 214) configured to couple optical radiation between the sensing cell and a target external to the substrate, and a receiver (114, 174, 178, 216, 218), which is coupled to mix the coherent radiation extracted by the tap with the optical radiation received by the optical transducer and to output an electrical signal responsively to the mixed radiation.

An apparatuses relating generally to a test wafer, processing chambers, and method relating generally to monitoring or calibrating a processing chamber, are described. In one such an apparatus for a test wafer, there is a platform. An optical fiber with Fiber Bragg Grating sensors is located over the platform. A layer of material is located over the platform and over the optical fiber.