Nippon Telegraph and Telephone Corporation

Junji Sakamoto

Toshikazu Hashimoto

Kei Watanabe

Ryoichi Kasahara

Takahiro Kashiwazaki

Naru Nemoto

Satomi Katayose

Yuji Fujiwara

Tomohiro Inaba

To provide an optical multiplexing circuit that can accurately monitor light of a plurality of wavelengths, and that can mitigate allowable errors in manufacturing. The present invention includes a plurality of branching units that each divide light output from a corresponding one of a plurality of input waveguides; a multiplexing unit that multiplexes beams each being one beam of the light divided by each of the plurality of branching units; an output waveguide that outputs the light multiplexed by the multiplexing unit; and a plurality of monitoring waveguides that each output another beam of the light divided by the plurality of branching units, wherein a plurality of optical multiplexing circuits including multiplexing units having different multiplexing characteristics are provided on a same substrate.

Optical multiplexing circuit and light source

An optical beam combiner circuit includes a plurality of branch portions configured to divide optical beams output from a plurality of input waveguides, a combiner unit configured to combine optical beams, each of the optical beams being one of the divided optical beams obtained by one of the plurality of branch portions, an output waveguide configured to output an optical beam obtained by the combiner unit combining the optical beams, a plurality of monitoring waveguides configured to output optical beams, each of the optical beams being another of the divided optical beams obtained by one of the plurality of branch portions, and a plurality of light-blocking grooves provided on both sides with respect to each input waveguide, the plurality of light-blocking grooves being positioned to enable stray light not coupled to the plurality of input waveguides to be reflected toward an end surface different from an exit end surface of each monitoring waveguide and also different from an exit end surface of the output waveguide.

Optical multiplexing circuit

There is a manufacturing error even if an RGB coupler is appropriately designed, and thus a problem that it is difficult to achieve the function as designed with good yield arises. To solve this problem, an optical circuit with a first waveguide in which light in a zero-th order mode is guided and a second waveguide having a larger width than the first waveguide, in which light in a primary mode is guided in which the first and second waveguides at least include a first curved portion in a curve shape curved toward the first waveguide while maintaining a combination of waveguide widths satisfying mode conversion conditions is provided.

Optical circuit

An optical multiplexing circuit capable of accurately monitoring light of a plurality of wavelengths is provided. An optical multiplexing circuit includes a plurality of branching units configured to each divide light output from a corresponding one of a plurality of input waveguides, a multiplexing unit configured to multiplex a plurality of first beams of the light, each obtained by dividing the light by a corresponding one of the plurality of branching units, an output waveguide configured to output the light multiplexed by the multiplexing unit, a plurality of monitoring multiplexing units that are optical circuits identical to the multiplexing unit, a plurality of first monitoring waveguides configured to output a plurality of second beams of the light, each obtained by dividing the light by a corresponding one of the plurality of branching units, to corresponding ones of the plurality of monitoring multiplexing units, and a plurality of second monitoring waveguides configured to each output an output of a corresponding one of the plurality of monitoring multiplexing units.

To provide an optical multiplexing circuit that can accurately monitor light of a plurality of wavelengths, and that can tolerate degradation of LDs. An optical multiplexing circuit includes m sets of multiplexers configured to multiplex light output from n connection waveguides being a plurality of connection waveguides wherein a multiplexing unit configured to input and multiplex light output from the m sets of the multiplexers from m input waveguides, an output waveguide configured to output light multiplexed by the multiplexing unit, and n×m or m branching units being inserted into n×m connection waveguides of the plurality of connection waveguides or the m input waveguides are provided on a same substrate.

Provided is a planar lightwave circuit in which stress on a substrate is reduced to decrease the curve of the substrate. The planar lightwave circuit is formed by layering a glass film on the substrate. When the optical axis direction from an input waveguide toward an output waveguide is in the longitudinal direction of the substrate, a plurality of grooves are formed in a line in the transverse direction of the substrate.

Planer lightwave circuit

A mode multiplexing/demultiplexing optical circuit with a reduced inter-mode crosstalk is provided. A mode multiplexing/demultiplexing optical circuit includes a Portthrough which light from a light source is input to a waveguide, a Portthrough which light propagating through a first waveguide is output, a mode conversion unit located adjacent to the first waveguide, and configured to convert a first-order mode light input from the Portto a second-order mode, and Portconfigured to convert, via a waveguide located adjacent to the mode conversion unit, second-order mode light input to the mode conversion unit to a zeroth-order mode.

Mode multiplexing/demultiplexing optical circuit

An optical multiplexing circuit includes a plurality of branching units configured to each divide light output from a corresponding one of a plurality of input waveguides, a multiplexing unit configured to multiplex a plurality of first beams of the light, each obtained by dividing the light by a corresponding one of the plurality of branching units, an output waveguide configured to output the light multiplexed by the multiplexing unit, a plurality of monitoring filters configured to individually input, via a first monitoring waveguide, a corresponding one of a plurality of second beams of the light, a wavelength through each of the plurality of monitoring filters having a transmittance of 50% being set to be a center wavelength of the plurality of second beams of the light, and a change in wavelength due to an assumed change in temperature being set to be less than half of an FSR, and a plurality of second monitoring waveguides.

In a conventional RGB coupler, the split ratio largely depends on the wavelength. The split ratio of R and the split ratios of G and B are non-uniform because R has a wavelength far from those of G and B. Accordingly, a video display device needs to have the monitoring detection value corrected, making it difficult to use the monitoring function. A light combining circuit and a light source of this disclosure include a first splitting unit for splitting R wavelength light and a second splitting unit for splitting G and B combined light. They split monochromatic light of R and combined light of G and B, independently. G and B light from an LD are first combined by a preliminary wave-combining unit before being split. The split lights of each wavelength are combined by a main wave-combining unit, outputting RGB combined light. Each split light from the two splitting units is detected by a single PD.

Optical multiplexing circuit and optical source

To reduce the size while being able to accurately monitor light of a plurality of wavelengths. An optical multiplexing circuit includes: a plurality of branching units each configured to divide light output from a corresponding one of a plurality of input waveguides; a multiplexing unit configured to multiplex beams each being one beam of the light divided by each of the plurality of branching units; an output waveguide configured to output the light multiplexed by the multiplexing unit; and a plurality of monitoring waveguides each configured to output another beam of the light divided by each of the plurality of branching units, wherein at least one monitoring waveguide of the plurality of monitoring waveguides includes a bent waveguide constituted by a rib-shaped waveguide.

To provide a planar lightwave circuit capable of being optically connected to a semiconductor optical element or an optical wiring component in a simple, precise, and stable manner without an increase in circuit footprint or the number of fabrication steps or a deterioration of characteristics. By arranging a dummy optical waveguide having a mirror function in the vicinity of an input/output waveguide of an optical functional circuit forming the planar lightwave circuit, a semiconductor optical element or an optical wiring component can be easily aligned with and fixed to the optical functional circuit by monitoring the reflection light intensity from the dummy optical waveguide. When the optical functional circuit has a plurality of input/output waveguides to be optically connected, each input/output waveguide can be identified if the dummy optical waveguides having the mirror function have different reflection properties (such as reflectance, width, position, or reflection wavelength).

Planar lightwave circuit and optical device

An optical multiplexer that extends a transmission bandwidth of light is achieved. The present invention provides an optical multiplexer constructed of a multimode waveguide to which two single mode input waveguides are connected at a distance and two single mode output waveguides connected at a distance to a surface opposite a surface to which the input waveguides of the multimode waveguide are connected, in which a width of the multimode waveguide is smaller than widths of the two input waveguides plus a distance between the input waveguides, and the input waveguides are connected to the multimode waveguide and the multimode waveguide is connected to the output waveguides via tapered waveguides, respectively.

Optical multiplexer and RGB coupler

Provided is an optical multiplexing circuit. The waveguide width of each waveguide is set such that the effective refractive index of a first optical waveguide with a first light beam in the 0-th order mode is equal to the effective refractive index of a MM conversion waveguide with the first light beam in the higher order mode and that the effective refractive indexes of the MM conversion waveguide with second and third light beams in the higher order mode are not equal to the effective refractive indexes of a second optical waveguide with the second and third light beams in the 0-th order mode.

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Kanagawa-ken, Japan

Junji Sakamoto