A multi-mode interferometric optical waveguide device includes: a multi-mode interferometric optical waveguide which includes a first reflective surface; a first single-mode waveguide connected to the multi-mode interferometric optical waveguide; and a second single-mode waveguide connected to the multi-mode interferometric optical waveguide and oppose the first reflective surface. Consequently, the multi-mode interferometric optical waveguide device can propagate light from the first single-mode waveguide to the second single-mode waveguide, with further reduced optical losses.

In various embodiments, a beam-parameter adjustment system and focusing system alters a spatial power distribution of a plurality of radiation beams before the beams are coupled into an optical fiber.

Swept-source Raman spectroscopy uses a tunable laser and a fixed-wavelength detector instead of a spectrometer or interferometer to perform Raman spectroscopy with the throughput advantage of Fourier transform Raman spectroscopy without bulky optics or moving mirrors. Although the tunable laser can be larger and more costly than a fixed wavelength diode laser used in other Raman systems, it is possible to split and switch the laser light to multiple ports simultaneously and/or sequentially. Each site can be monitored by its own fixed-wavelength detector. This architecture can be scaled by cascading fiber switches and/or couplers between the tunable laser and measurement sites. By multiplexing measurements at different sites, it is possible to monitor many sites at once. Moreover, each site can be meters to kilometers from the tunable laser. This makes it possible to perform swept-source Raman spectroscopy at many points across a continuous flow manufacturing environment with a single laser.

A waveguide having a bi-directional optical transmission structure comprises: a main waveguide which is formed in a preset direction; a branch waveguide which is connected to at least one of both ends of the main waveguide; and a reflector which is placed at an intersection where the branch waveguide and the at least one of both ends of the main waveguide are connected, and which has a different refraction index from the refraction index of the main waveguide and the refraction index of the branch waveguide, wherein the reflector refracts or reflects in different forms the bidirectional light signals for transmission and reception, and thereby directs the light signal for transmission to the main waveguide, and separates the light signal for reception to the branch waveguide.

An optical module according to an embodiment includes a first optical component and a second optical component including a multicore fiber (MCF) and a spatial joining part. The first optical component includes a first uncoupled MCF having small optical coupling between cores and a first coupled MCF having a mode field diameter (MFD) larger than a MFD of the first uncoupled MCF. The second optical component includes a second uncoupled MCF having small optical coupling between cores and a second coupled MCF having a MFD larger than a MFD of the second uncoupled MCF. In the first coupled MCF and the second coupled MCF, crosstalk is periodically produced along the length direction of an MCF, and the total of the length of the first coupled MCF and the length of the second coupled MCF is a length L in which crosstalk is suppressed.

Provided is a detecting apparatus including a light source emitting an illumination light flux, a light receiving element receiving a reflected light flux from an object, a deflection unit deflecting illumination light flux toward the object to scan the object and deflecting reflected light flux toward light receiving element, a splitting unit allowing illumination light flux from light source to proceed toward deflection unit and allowing reflected light flux from deflection unit to proceed toward light receiving element, and a first telescope increasing a diameter of illumination light flux deflected by deflection unit, and decreasing a diameter of reflected light flux from the object in which the deflection unit is arranged so that a light path of a principal ray of illumination light flux at a center angle of view in a scanning range of deflection unit is prevented from coinciding with an optical axis of first telescope.

Included are a transmitter and a receiver caused to have a constant temperature. The transmitter includes: a semiconductor optical amplifier having a reflection mirror at a first end thereof; an optical waveguide having a first end coupled to a second end of the semiconductor optical amplifier; a wavelength demultiplexing filter having an input port coupled to a second end of the optical waveguide and a plurality of output ports having constant transmission wavelength intervals; reflection structures to reflect part of light output from the output ports, the reflection structures provided for the respective output ports of the wavelength demultiplexing filter; modulators to modulate light transmitted through the reflection structures, the modulators provided for the respective reflection structures; and a wavelength multiplexing filter having input ports coupled to the respective output ends of the modulators, transmission wavelength intervals of the input ports being identical to the transmission wavelength intervals of the wavelength demultiplexing filter, and having the output port coupled to a first end of an optical fiber. The receiver includes: a wavelength demultiplexing filter having an input port coupled to a second end of the optical fiber and a plurality of output ports having the same transmission wavelength intervals as the transmission wavelength intervals of the wavelength demultiplexing filter and an FSR obtained by multiplying the transmission wavelength interval by the number of the output ports; light receivers to receive light output from the output ports, the light receivers provided for the respective output ports of the wavelength demultiplexing filter; and a temperature controller to control the temperature of the wavelength demultiplexing filter.

In various embodiments, a beam-parameter adjustment system and focusing system alters a spatial power distribution of a plurality of radiation beams before the beams are coupled into an optical fiber.

A system including an optical waveguide having a length extending from an optical interrogator at a first end, a plurality of light-modulating sensor nodes disposed at predetermined locations along the length of the optical waveguide, and (in some embodiments) a plurality of first beam splitters at each of the predetermined locations along the length of the optical waveguide, each of the first beam splitters configured to direct a portion of an optical signal from the optical interrogator to one of the plurality of light-modulating sensor nodes along an optical waveguide path, and return a reflected optical signal to the optical interrogator in an opposite direction along the same optical waveguide path.

A curved light guide structure configured to guide a spectral region, includes: end faces disposed at two ends of the ring segment structure; a first main side extending between the end faces and a second main side opposite the first main side and extending between the end faces; at least a first pass region on the first main side, the first pass region being configured to receive and let pass an optical signal within the spectral region, the curved light guide structure being configured to guide the optical signal along an axial direction between the end faces; and at least a second pass region on the second main side that is configured to let pass and to emit at least part of the optical signal from the curved light guide structure.