An optical waveguide device that enables single-mode coupling between cores to be coupled by controlling optical signal intensity variation due to an MPI. The optical waveguide device includes a first device end surface, a second device end surface, a waveguide, and a cladding layer. The waveguide has a first waveguide end surface and a second waveguide end surface, and light beams of a plurality of modes having different orders are guided. Further, the waveguide has one or more bent portions. The cladding layer has a refractive index lower than a refractive index of the waveguide. The waveguide has a waveguide length L of 5×10.sup.6 [nm] or more and 100×10.sup.6 [nm] or less, and has a structure in which an inter-mode group delay time difference Δβ1 satisfies a condition given by |Δβ1|≤½×10.sup.−12 [s]/L.

A coupler including a first end that optically couples with a plurality of single-core optical fibers, a second end that optically couples with a multi-core optical fiber, and a plurality of cores that each extends from the first end to the second end. The plurality of cores comprising a first core such that an outer diameter of the first core at the first end is larger than an outer diameter of the first core at the second end. The coupler further includes an outer cladding surrounding the plurality of cores and extending from the first end to the second end such that an outer diameter of the outer cladding at the first end is larger than an outer diameter of the outer cladding at the second end. Additionally, the coupler is a single, contiguous, conical glass member that tapers from the first end to the second end.

A dual-core optical fiber include a first waveguide comprising a first core longitudinal centreline and a second waveguide comprising a second core longitudinal centreline. The first and second waveguides extend through a common cladding through comprising a longitudinal centerline and an outer radius R.sub.4 that is less than or equal to 45 μm. The first core longitudinal centerline and the second core longitudinal centerline are separated from one another by a waveguide-to-waveguide separation distance that is greater than or equal to 30 μm. A cross-talk between the first and second waveguides is less than or equal to −40 dB at 1310 nm, as measured over a length of 100 km of the dual-core optical fiber.

Multicore fibers and endoscope configurations are provided, along with corresponding production and usage methods. Various configurations include an adiabatically tapered proximal fiber tip and/or proximal optical elements for improving the interface between the multicore fiber and the sensor, photonic crystal fiber configurations which reduce the attenuation along the fiber, image processing methods and jointed rigid links configurations for the endoscope which reduce attenuation while maintaining required flexibility and optical fidelity. Various configurations include spectral multiplexing approaches, which increase the information content of the radiation delivered through the fibers and endoscope, and configurations which improve image quality, enhance the field of view, provide longitudinal information. Various configurations include fiber-based wave-front sensors. Many of the disclosed configurations increase the imaging resolution and enable integration of additional modes of operation while maintain the endoscope very thin, such as spectral imaging and three dimensional imaging.

Provided is a method of manufacturing an optical device that includes a multicore fiber including a plurality of cores and a fan-in/fan-out device including single-core fibers that are respectively connected to the cores based on a plurality of connection combinations when the multicore fiber is rotated. The method includes: a first step of determining an optical loss for each of the cores while changing the connection combinations between the single-core fibers and the cores; and a second step of selecting one of the connection combinations according to a result of the first step and connecting an end portion of the multicore fiber and an end portion of the fan-in/fan-out device to connect the single-core fibers with the cores based on the one of the connection combinations.

According to embodiments, a method of making a microstructured glass article includes bundling M bare optical fibers in a fiber bundle, wherein M is an integer greater than 100. Thereafter, the fiber bundle may be inserted in a cavity of a soot preform. The soot preform may have a density of less than or equal to 1.5 g/cm.sup.3 and comprise silica-based glass soot. The soot preform and inserted fiber bundle may then be consolidated to form a microstructured glass article preform. The microstructured glass article preform may then be drawn into the microstructured glass article comprising M core elements embedded in a cladding matrix.

An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.

An optical fiber includes multiple optical waveguides configured in the fiber. An interferometric measurement system mitigates or compensates for the errors imposed by differences in a shape sensing optical fiber's response to temperature and strain. A 3-D shape and/or position are calculated from a set of distributed strain measurements acquired for a multi-core optical shape sensing fiber that compensates for these non-linear errors using one or more additional cores in the multicore fiber that react differently to temperature changes than the existing cores.

An optical combiner includes: first optical input portions each including a first optical input waveguide; and an optical output portion to which the first optical input portions are connected and that includes a first core that allows light to propagate therethrough, and a cladding layer disposed outside of the first core and that has a refractive index lower than a refractive index of the first core. The first optical input portions are connected to a connection end face of the optical output portion such that the first optical input waveguide of at least one of the first optical input portions is optically coupled to the first core of the optical output portion.

A multicore fiber includes: a plurality of first glass regions each including: a core portion; and a first cladding portion having a lower refractive index than a maximum refractive index of the core portion; and a cladding region formed on outer peripheries of the plurality of first glass regions, wherein compressive stress is applied to the plurality of first glass regions.