A manufacturing method for an optical fiber, includes: drawing, while heating in a heating furnace, a lower end of an optical fiber preform that is to be an optical fiber having a core consisting of silica glass containing a rare earth element compound. The heating furnace has a temperature profile in which a temperature of the heating furnace increases to a maximum temperature T.sub.max and then decreases from an upstream side of the heating furnace toward a downstream side of the heating furnace. The temperature profile has a changing point at which the temperature decreases more steeply on the downstream side from a position where the maximum temperature T.sub.max is reached. At the maximum temperature, a temperature of the silica glass is higher than or equal to a glass transition temperature and the silica glass is in a single phase.

A fiber optic sensing device includes an optical fiber having a polished end defining a flat sensory portion coated with a lossy-mode-resonance (LMR) coating. A reflective coating on an end face of the optical fiber facilitates propagation of a return signal. An optic circuit for identifies a wavelength attenuated by the LMR coating from the return signal reflected by the reflective coating based on a moisture presence at the sensory portion. Various gaseous parameters may be detected based on the coating on the sensory portion. An LMR coating of tin oxide (SnO.sub.2) is employed for moisture sensing.

An imaging sensor includes at least one fiber Bragg grating for filtering an image from a subject for wavelength bands, and an imaging device for converting an image transmitted through the fiber Bragg grating into a digital signal.

The present invention is directed to an optical fiber grating having a core, that is capable of controlling the light signal transmission therethrough by causing at least one of: at least one spectral peak, and/or at least one spectral dip in its core light transmission spectrum, corresponding to at least one predetermined wavelength. The inventive optical fiber diffraction grating comprises at least one longitudinally positioned structural element of a predetermined geometric profile and that is configured for diffracting a portion of the transmitted light signal at at least one predefined wavelength thereof, from at least one core mode into at least one of: at least one cladding mode and/or at least one radiating mode. Various embodiments of a number of novel techniques for fabrication of the inventive optical fiber diffraction grating are provided, inclusive of a novel technique for fabricating the inventive grating from a single material. Advantageously, such novel fabrication techniques rely on configuration of a desired geometric profile for the at least one structural element portion of the novel grating, each profile comprising a number of readily configurable parameters that can be selected and/or adjusted during fabrication, to produce a variety of novel fiber diffraction gratings, each having a corresponding specific desirable core transmission spectrum having at least one of: least one spectral peak, and/or at least one spectral dip therein, corresponding to at least one specific desired wavelength, dependent on the configuration of the applicable geometric profile.

A fiber optic sensing device includes an optical fiber having a polished end defining a flat sensory portion coated with a lossy-mode-resonance (LMR) coating. A reflective coating on an end face of the optical fiber facilitates propagation of a return signal. An optic circuit for identifies a wavelength attenuated by the LMR coating from the return signal reflected by the reflective coating based on a moisture presence at the sensory portion. Various gaseous parameters may be detected based on the coating on the sensory portion. An LMR coating of tin oxide (SnO.sub.2) is employed for moisture sensing.

An optically transparent protective coating is described that remains stable at elevated temperatures associated with optical fiber-based sensor applications and is sufficiently transparent to allow for conventional fiber Bragg gratings (FBGs) to be formed by directly writing through the coating. In particular, vinyl group-containing silicone polymers have been found to provide the UV transparency required for a write-through coating (WTC) and promising mechanical properties for protecting the optical fibers, while also being able to withstand elevated temperatures for extended periods of time.

An optical connection structure includes a PLC that is an optical waveguide chip including an optical waveguide and at least one groove formed on a substrate, and at least one optical fiber that is fitted into the at least one groove of the PLC. The PLC includes the optical waveguide, at least one grating coupler that is optically connected to the optical waveguide, and the at least one groove formed at a position in a vicinity of the at least one grating coupler in a cladding layer in which the optical waveguide is formed. An optical fiber of the at least one optical fiber is fitted into a groove of the at least one groove such that an end surface of the optical fiber is located in a vicinity of a grating coupler of the at least one grating coupler, the optical fiber being optically connected to the grating coupler.

An optical fiber includes a silica-based glass. The optical fiber includes a core, an optical cladding surrounding the core, and a physical cladding surrounding the optical cladding. The optical cladding includes a first region in contact with the core and surrounding the core. A photosensitive material is added to the core and the first region. A concentration of the photosensitive material in the first region is 30% or more of a concentration of the photosensitive material in the core. A value obtained by integrating a light intensity of an LP.sub.01 mode at a wavelength of 1310 nm in a region added with the photosensitive material is 87% or more of a value obtained by integrating the light intensity in an entire region of the optical fiber.

A light detection and ranging (LIDAR) device includes a waveguide, cladding, and a scattering array. The waveguide is configured to route an infrared optical field. The cladding is disposed around the waveguide. The scattering array is formed in the cladding. The scattering array is configured to perturb the infrared optical field routed by the waveguide to direct the infrared optical field into an infrared beam propagating toward a surface of the cladding.

An optical fiber may include a first core, a second core, and a cladding surrounding the first core and the second core. The second core may be at an off-center location with respect to a center of the optical fiber, or the second core may include an azimuthally nonuniform section at the off-center location. The second core may twist about an axis of the optical fiber along a length of the optical fiber, and the second core being twisted about the axis may cause an optical beam, launched into the second core at a first end of the optical fiber, to be at least partially converted to a rotary optical beam at a second end of the optical fiber.