An optical fiber for measuring pressure comprising a core for guiding optical signals along a length of the core and a cladding layer including a plurality of stress applying parts disposed around the core. The plurality of stress applying parts are disposed parallel to and symmetrically around the core to induce intensified symmetric shear stress upon application of external pressure while preventing birefringence. The optical fiber provides improved strain sensitivity compared to a standard single-mode optical fiber.

A medical instrument is described that includes an optical source, an optical fiber, and a waveguide patterned upon a substrate. The optical fiber receives radiation from the optical source and includes a first segment and a second segment. The second segment is rotated about an optical axis relative to the first segment. The waveguide receives radiation from the optical source and guides a beam of radiation. The waveguide includes a first waveguide segment designed to impart a first differential group delay on the beam of radiation and a second waveguide segment designed to impart a second differential group delay on the beam of radiation. A sum of the first differential group delay and the second differential group delay is substantially zero.

A medical instrument is described that includes an optical source, an optical fiber, and a waveguide patterned upon a substrate. The optical fiber receives radiation from the optical source and includes a first segment and a second segment. The second segment is rotated about an optical axis relative to the first segment. The waveguide receives radiation from the optical source and guides a beam of radiation. The waveguide includes a first waveguide segment designed to impart a first differential group delay on the beam of radiation and a second waveguide segment designed to impart a second differential group delay on the beam of radiation. A sum of the first differential group delay and the second differential group delay is substantially zero.

A polarization-maintaining dispersion-compensation microstructure fiber includes an inner core, an air-hole array in area 1 and an air-hole array in area 2. The air holes in the area 1 and 2 air-hole arrays are arranged in square lattice. The air-hole arrays in areas 1 and 2 are dislocated by half-layer along y-direction. In area 1, 2 air holes in the middle row are omitted to form a solid area as the inner core. 2 outer cores are located in 2 sub-areas of area 2, and each outer core contains 2 air holes. The long (or short) axes of the inner and outer cores are perpendicular, and the center points of the inner core and the two outer cores are located on the x-axis. The optical mode has a large negative dispersion in a certain polarized direction of the inner core, and the microstructure fiber can maintain the polarized direction of this mode during transmission.

A polarization-maintaining dispersion-compensation microstructure fiber includes an inner core, an air-hole array in area 1 and an air-hole array in area 2. The air holes in the area 1 and 2 air-hole arrays are arranged in square lattice. The air-hole arrays in areas 1 and 2 are dislocated by half-layer along y-direction. In area 1, 2 air holes in the middle row are omitted to form a solid area as the inner core. 2 outer cores are located in 2 sub-areas of area 2, and each outer core contains 2 air holes. The long (or short) axes of the inner and outer cores are perpendicular, and the center points of the inner core and the two outer cores are located on the x-axis. The optical mode has a large negative dispersion in a certain polarized direction of the inner core, and the microstructure fiber can maintain the polarized direction of this mode during transmission.

A multicore fiber is provided that includes a plurality of elliptical cores spaced apart from one another. Each of the plurality of elliptical cores has an elliptical shape. The multicore fiber also includes a cladding surrounding the plurality of elliptical cores.

A method of forming a tapered tip of a polarization-maintaining (PM) fiber includes inserting a tip of the PM fiber into a first etchant solution characterized by a first etching rate for the core of the PM fiber and a second etching rate for the stress members of the PM fiber, the second etching rate being lower than the first etching rate, withdrawing the tip of the PM fiber from the first etchant solution at a withdrawal rate, immersing the tip of the PM fiber in a second etchant solution for a time duration. The second etchant solution is characterized by a third etching rate for the core and a fourth etching rate for the stress members, the fourth etching rate being greater than the third etching rate. The method further includes withdrawing the tip of the PM fiber from the second etchant solution.

A method of forming a tapered tip of a polarization-maintaining (PM) fiber includes inserting a tip of the PM fiber into a first etchant solution characterized by a first etching rate for the core of the PM fiber and a second etching rate for the stress members of the PM fiber, the second etching rate being lower than the first etching rate, withdrawing the tip of the PM fiber from the first etchant solution at a withdrawal rate, immersing the tip of the PM fiber in a second etchant solution for a time duration. The second etchant solution is characterized by a third etching rate for the core and a fourth etching rate for the stress members, the fourth etching rate being greater than the third etching rate. The method further includes withdrawing the tip of the PM fiber from the second etchant solution.

A fiber optic temperature sensor, a sensing head structure, and a manufacturing method are provided. The fiber optic temperature sensor includes a broad spectrum light source, a first fiber optic coupler, a spectrometer, a first sensing interferometer, and a second sensing interferometer. The first sensing interferometer and the second sensing interferometer have opposite temperature responses. A first free spectral range corresponding to the first sensing interferometer is close to but not equal to a second free spectral range corresponding to the second sensing interferometer. In the fiber optic temperature sensor, two sensing interferometers both sensitive to temperature are used, and the two sensing interferometers have opposite temperature responses, thereby achieving an enhanced vernier effect, and improving the sensitivity of temperature measurement.

A fiber optic temperature sensor, a sensing head structure, and a manufacturing method are provided. The fiber optic temperature sensor includes a broad spectrum light source, a first fiber optic coupler, a spectrometer, a first sensing interferometer, and a second sensing interferometer. The first sensing interferometer and the second sensing interferometer have opposite temperature responses. A first free spectral range corresponding to the first sensing interferometer is close to but not equal to a second free spectral range corresponding to the second sensing interferometer. In the fiber optic temperature sensor, two sensing interferometers both sensitive to temperature are used, and the two sensing interferometers have opposite temperature responses, thereby achieving an enhanced vernier effect, and improving the sensitivity of temperature measurement.