Abstract: There is provided an optical resonator including: N individual optical waveguide paths of line segment shape disposed in a common flat-plane so as to intersect at a single intersection region, wherein N is an integer of 2 or more; curved optical waveguide paths connecting respective portions of the optical waveguide paths that extend towards the outside from the intersection region, wherein for a first to a 2Nth optical waveguide path portions in a clockwise direction, connection is made between end portions at the opposite side to the intersection region of the (2i?1)th to 2ith optical waveguide path portions, wherein i is an integer of 1 to N; and an optical coupler that couples light input or output perpendicular to the flat-plane with the optical waveguide paths, the optical coupler being formed in a region containing the intersection region where the optical waveguide paths are connected.

Abstract: An optical waveguide includes a substrate, an upper clad layer arranged on the substrate; and an optical waveguide structure that is disposed in the upper clad layer so as to be parallel to a surface of the substrate. The optical waveguide structure includes a flat optical waveguide, channel optical waveguides that are each connected with a first edge face of the flat optical waveguide and extend radially therefrom, the channel optical waveguides each respectively have lateral sides parallel to the substrate surface that have a width therebetween which increases as the distance from the first edge face increases, and an input optical waveguide connected with a second edge face that is arranged at an side of the flat optical waveguide opposite to the first edge face.

Abstract: An optical device includes a core sandwiched between two clads. The core includes a planar waveguide layer with ridges protruding into one of the clads, forming a ridge waveguide structure that guides the propagation of light in the core. The core dimensions satisfy the following conditions: the ridge width is less than the total core height; the ridge height is less than the ridge width; the thickness of the planar waveguide layer is equal to or less than one-fourth of the total core height. Dimensions satisfying these conditions can be selected to provide polarization independent operation. The ridges may be arranged to define a pair of optical waveguides forming a Mach-Zehnder interferometer, an optical wavelength filter, or various other optical devices.

Abstract: An optical device has two optical waveguides embedded in a clad. The optical waveguides are mutually parallel and are separated by a distance that allows optical coupling between them. The optical waveguides have identical square cross sectional shapes in a plane orthogonal to the direction of light propagation, so that light propagates through each optical waveguide without polarization dependence. The length of each side of the square cross section of the optical waveguides is determined from the refractive index of the clad and the distance between the longitudinal axes of the optical waveguides so that coupling between the two optical waveguides is also polarization independent for light with a wavelength of 1.49 micrometers, which is the longer of the two wavelengths used in optical subscriber networks.

Abstract: A spot-size converter is equipped with a substrate, a clad that is formed on the substrate, a core that is embedded inside the clad, and an input/output end face. The core is tapered toward the input/output end face along a light propagation direction. In the clad, groove portions that expose a substrate face are formed extending as far as the input/output end face and on both sides of the core along the light propagation direction.

Abstract: An optical wavelength filter has optical waveguides each of which includes a cladding layer and a core having a refractive index that is as high as that of the cladding layer by a factor of 1.4 or more. Each optical waveguide is partitioned into a reference section providing a reference and an adjustment section for adjusting phase differences. The reference section of each optical waveguide is so set that the optical waveguide in this section has a first equivalent refractive index and a first length. The adjustment section is so set that the waveguide in this adjustment section has a second equivalent refractive index and a second length. Two waves of light outputted from the output ends of adjacent two of the optical waveguides interfere with each other with a predetermined phase difference, thereby accomplishing independency of temperature and dimensional error.

Abstract: A polarization-independent optical multiplexer/demultiplexer with wide passbands has a core including an input optical waveguide, an input slab optical waveguide connected to the input optical waveguide, a waveguide array connected to the input slab optical waveguide, an output slab optical waveguide connected to the waveguide array, a pair of multimode couplers connected to the output slab optical waveguide, and a pair of output optical waveguides connected to the multimode couplers. The multimode couplers are dimensioned so that as both TE and TM polarized light propagates through them, the phase difference between the fundamental and second-order modes changes by an odd multiple of pi radians.

Abstract: A star coupler includes a core embedded in a clad on a major surface of a substrate. The refractive index of the core differs by at least 40% from the refractive index of the clad. The core includes a slab optical waveguide, at least one input-output optical waveguide connected to the slab optical waveguide, and an array of channel optical waveguides connected to the slab optical waveguide. The star coupler also includes a high-index layer having a refractive index intermediate between the refractive indexes of the clad and core, covering the sides of the core orthogonal to the major surface of the substrate. The high-index layer reduces light loss.

Abstract: An optical resonator has a Y-branched waveguide including first, second, and third optical waveguides interconnected at a single point. The first optical waveguide leads toward a reflector. The second and third optical waveguides are optically interconnected by a curved extension of the second and third optical waveguides, or by an independent ring waveguide to which the second and third optical waveguides are directionally coupled. At least one wavelength selector such as a Mach-Zehnder interferometer is formed in one or both of the second and third optical waveguides. This optical resonator is small in size and can be tuned by means of a single parameter. A tunable laser can be formed by inserting an optical amplifier between the first optical waveguide and the reflector.

Abstract: A spot-size converter is equipped with a substrate, a clad that is formed on the substrate, a core that is embedded inside the clad, and an input/output end face. The core is tapered toward the input/output end face along a light propagation direction. In the clad, groove portions that expose a substrate face are formed extending as far as the input/output end face and on both sides of the core along the light propagation direction.

Abstract: The present invention provides a data communication network that has a link structure that allows a large traffic-handling performance to be obtained with a small network construction cost. In the data communication network of the present invention, the nodes are assigned with m-dimensional coordinates (J1, J2, J3, J4, J5, . . . , Jm?1, Jm), in which any one of the coordinate values J1 to Jm is zero and the other coordinate values are all natural numbers, and each of said node is connected to other nodes which satisfy both of the following conditions (i) and (ii): (i) the coordinate Jp whose value is zero at said other node differs from a coordinate Jq whose value is zero at said node; and (ii) the value of coordinates other than the Jp and the Jq at said the other node all match the corresponding coordinate values of said node.

Abstract: An optical device has two optical waveguides embedded in a clad. The optical waveguides are mutually parallel and are separated by a distance that allows optical coupling between them. The optical waveguides have identical square cross sectional shapes in a plane orthogonal to the direction of light propagation, so that light propagates through each optical waveguide without polarization dependence. The length of each side of the square cross section of the optical waveguides is determined from the refractive index of the clad and the distance between the longitudinal axes of the optical waveguides so that coupling between the two optical waveguides is also polarization independent for light with a wavelength of 1.49 micrometers, which is the longer of the two wavelengths used in optical subscriber networks.

Abstract: An optical device includes a core sandwiched between two clads. The core includes a planar waveguide layer with ridges protruding into one of the clads, forming a ridge waveguide structure that guides the propagation of light in the core. The core dimensions satisfy the following conditions: the ridge width is less than the total core height; the ridge height is less than the ridge width; the thickness of the planar waveguide layer is equal to or less than one-fourth of the total core height. Dimensions satisfying these conditions can be selected to provide polarization independent operation. The ridges may be arranged to define a pair of optical waveguides forming a Mach-Zehnder interferometer, an optical wavelength filter, or various other optical devices.

Abstract: An optical deflector made of an electro-optic material has one or more pairs of electrodes on opposite surfaces. Each pair of electrodes defines an interaction region in which an electric field applied from the electrodes produces a linear refractive-index gradient in the direction of the electric field. An incident light beam is refracted in this direction within the interaction region. The interaction region is shaped so that the light beam is also refracted in an orthogonal direction when it enters or leaves the interaction region. The light beam is thereby deflected three-dimensionally.

Abstract: In an optical multiplexing/demultiplexing device are arranged in parallel and disposed on a substrate. The optical multiplexing/demultiplexing device is disposed with three or more Mach-Zehnder interferometers between the first and second optical input/output ports. The optical multiplexing/demultiplexing device divides, by wavelength, multiplexed light comprising first light and second light whose wavelengths are different and which are input to one of the first optical input/output ports and outputs the multiplexed light from each of the second optical input/output ports. The absolute value of an optical path difference ?L of each the Mach-Zehnder interferometers is constant. The optical multiplexing/demultiplexing device includes one or more each of a pair of two successive Mach-Zehnder interferometers where the sum of their optical path differences becomes +2?L or ?2?L and a pair of two successive Mach-Zehnder interferometers where the sum of their optical path differences becomes 0.

Abstract: There is provided an optical resonator including: N individual optical waveguide paths of line segment shape disposed in a common flat-plane so as to intersect at a single intersection region, wherein N is an integer of 2 or more; curved optical waveguide paths connecting respective portions of the optical waveguide paths that extend towards the outside from the intersection region, wherein for a first to a 2Nth optical waveguide path portions in a clockwise direction, connection is made between end portions at the opposite side to the intersection region of the (2i?1)th to 2ith optical waveguide path portions, wherein i is an integer of 1 to N; and an optical coupler that couples light input or output perpendicular to the flat-plane with the optical waveguide paths, the optical coupler being formed in a region containing the intersection region where the optical waveguide paths are connected.

Abstract: There is provided an optical device including a first optical waveguide of a directional coupler, a second optical waveguide connected to the first optical waveguide and which guides light, and a common cladding of the first and second optical waveguides, wherein: the common cladding of the first and second optical waveguides includes a first cladding and a second cladding, the second cladding being provided on the first cladding and having a higher refractive index than the first cladding; the first optical waveguide and the second optical waveguide are formed continuously on the first cladding with a constant width and a constant height and are integrated with each other, and a cross sectional shape of each of the first and second optical waveguides is a rectangular shape that is longest in a direction orthogonal to a surface of the first cladding.

Abstract: An optical transceiver module includes a semiconductor laser that emits light along a first optical axis. A grating coupler, located in a plane including the first optical axis, diffracts the emitted light out of the plane and into an external optical system. A photodetector receives incoming light from the external optical system on a second optical axis that passes through the grating coupler at an angle to the plane. The photodetector can be placed parallel to the plane, directly above or below the grating coupler, to create an extremely compact optical transceiver module.

Abstract: An optical resonator has a Y-branched waveguide including first, second, and third optical waveguides interconnected at a single point. The first optical waveguide leads toward a reflector. The second and third optical waveguides are optically interconnected by a curved extension of the second and third optical waveguides, or by an independent ring waveguide to which the second and third optical waveguides are directionally coupled. At least one wavelength selector such as a Mach-Zehnder interferometer is formed in one or both of the second and third optical waveguides. This optical resonator is small in size and can be tuned by means of a single parameter. A tunable laser can be formed by inserting an optical amplifier between the first optical waveguide and the reflector.

Abstract: The present invention provides a data transfer network receiving a higher evaluation overall than conventional ones from various perspectives such as the number of effective nodes, the required number of links, and the required maximum node capacity. The present invention is a data transfer network of a hyper configuration in which each node is an element of m (m is 2 or more) different local networks. Further, at least one of the local networks to which the respective nodes belong is a hub network and, when a node belongs to a local network other than a hub network, the local network is a full mesh network.