Abstract: K×K optical switch unit according to the present invention is comprised of input ports 1-1, . . . 1-36, 1×M optical matrix switches 5-1-1, . . . 5-4-9 connected with the input ports 1-1, . . . 1-36, N×N optical matrix switches 7-1-1, . . . 7-4-2, and 10-1-1, . . . 10-4-2 connected with the 1×M optical matrix switches 5-11, . . . 5-4-9, an M×1 optical matrix switches 13-1-1, . . . 13-4-9 connected with the N×N optical matrix switches 7-1-1, . . . 7-4-2, and 10-1-1, . . . 10-4.2, and output ports 2-1, . . . 2-36 connected with the M×1 optical matrix switches 13-1-1 . . . 13-4-9, where K=M×N, M and N are integers more than 1.

Abstract: The present invention expands a selective wavelength band and flattens light intensity in the selective wavelength band as good as or better than prior art, and makes power loss less than prior art. The invention as a period characteristic wavelength splitter and an arrayed waveguide diffraction grating wavelength splitter between the first input/output port and the second input/output port in this sequence. The period characteristic wavelength splitter is comprised of the third star coupler, the second arrayed waveguide comprised of multiple waveguides having different optical path lengths, and the fourth star coupler. When an optical signal is input from the first input/output port, the period characteristic wavelength splitter outputs optical signals which wavelengths sequentially deviated with difference &dgr; from multiple ports at the first star coupler side of the fourth star coupler.

Abstract: A wavelength router has a structure capable of preventing a wavelength shift from occurring and an optical circuit device capable of reducing a phase error. The wavelength router includes three input ports; three input waveguides each having one end connected to the corresponding input ports, respectively; a first plane waveguide to which other ends of the input waveguides are connected; three output ports; three output waveguides each having one end connected to the corresponding output ports, respectively; a second plane waveguide to which other ends of the output ports are connected; and five interconnecting waveguides for connecting an output end face of the first plane waveguide and an input end face of the second plane waveguide. To make lengths of the interconnecting waveguides equal, optical path lengths from connection portions (end face) into which light signals are input to coupling parts between the first plane waveguide and the interconnecting waveguides, respectively, differ from one another.

Abstract: A lightwave filter which allows optical signals of a plurality of wavelength channels to be extracted even in the case of high-density multiplexing. It is provided with two rows of gratings, each with two fixed gratings, wherein the reflection wavelength is fixed, and two variable gratings, wherein the reflection wavelength can be shifted, connected rectilinearly to each other. It also has an optical circulator which guides optical signals of wavelength channels reflected by the first row of gratings to the second row of gratings. Of the variable gratings, the reflection wavelengths of those having basic reflection wavelengths which correspond to wavelength channels not selected from among the input optical signals are shifted to wavelengths other than the basic reflection wavelengths of the other variable gratings of the same row. This allows optical signals of selected wavelengths to be selected, while those of unselected wavelengths pass through.

Abstract: The optical communications system is capable of increasing its scale with the use of a fewer number of wavelengths and is flexible in allowing the topology to be altered. The optical cross connector minimizes optical loss and crosstalk. The optical communications system includes a plurality of optical communications networks. The optical communications network includes a group of nodes and optical fibers connecting the nodes to each other. The optical fibers include existing optical fibers forming a predetermined topology and auxiliary optical fibers provided for altering the topology with the help of a path switching function of each node. A selected one of the nodes in each optical communications network is connected to a switchboard by one of links. The switchboard is connected at the other end to a group of subscribers. The optical cross connector includes input side units, output side units, and an optical connecter connected between the input side units and the output side units.

Abstract: A wavelength router has first ports each receiving or providing a first multiwavelength optical signal having wavelengths, and second ports each providing or receiving second multiwavelength optical signals having multiplexed wavelengths. The number of multiplexed wavelengths of the second multiwavelength optical signal is smaller than the number of wavelengths of the first multiwavelength optical signal. The first multiwavelength optical signal is demultiplexed into the second multiwavelength optical signal. The second multiwavelength optical signals are multiplexed into the first multiwavelength optical signal. The first multiwavelength optical signal has a number N of multiplexed wavelengths, and the second ports are divided into M sets of second ports. The first multiwavelength optical signal is demultiplexed into optical signals having a number N/M of multiplexed wavelengths, which are supplied to the M sets of second ports.

Abstract: A multiwavelength optical switch capable of reducing an amount of internal circuit components to be connected to a plurality of multiwavelength circuit, and thus saving the occupied area of the switch. A wavelength router (11) receives, at M (M=3) input ports (a3, a6 and a9), multiwavelength optical signals (f#0-f#8) with the number of multiplexed wavelengths being nine (N=9) through incoming paths (13), reduces the number of multiplexed wavelengths to three (=N/M), and outputs the resultant optical signals from output ports (b1-b8). The same optical signals with the number of multiplexed wavelengths being three are connected to input ports of three switches (41, 42 and 43) through links (111-113), each consisting of M (=3) lines. The output ports of the switches are connected to input ports (b1-b9) of a wavelength router (12) through outgoing links (121-123). The three switches (41, 42 and 43) receive the multiwavelength optical signals (.lambda.2, .lambda.5, .lambda.8), (.lambda.0, .lambda.3, .lambda.

Abstract: A wavelength conversion apparatus has an optical amplifier, a wavelength converter, and an optical coupler coupled to form an optical ring resonator. The optical amplifier supplies pump light. The wavelength converter generates converted light, either from the pump light alone or by interaction between the pump light and signal light supplied from a signal source. The optical coupler extracts the converted light. The optical ring resonator preferably includes a tunable optical bandpass filter that defines the wavelength of the pump light. The optical coupler may also couple the signal light into the optical ring resonator, preferably through a polarization beam splitter and at least one polarization rotator, making the apparatus insensitive to the polarization of the signal light.

Abstract: An optical-wavelength interchanger element includes a branching section for bifurcating a wavelength-multiplexed input light signal having a multiplicity of an even number into first and second light signals. The interchanger element further includes a wavelength converting element for simultaneously converting wavelengths multiplexed in the first light signal so as to output a third light signal. The interchanger element further includes a transmission path for sending the second light signal therethrough without converting wavelengths multiplexed in the second light signal. The interchanger element further includes a joining section for combining the third light signal and the second light signal so as to output a wavelength-multiplexed output light signal. The interchanger elements may be connected in series in plural stages so as to form an optical-wavelength interchanger device.

Abstract: A wavelength conversion device includes a wavelength conversion element. The wavelength conversion element includes a ridge waveguide layer made of nonlinear optical crystals as being a zinc-blend material. The waveguide layer is provided on a GaAs substrate made of the zinc-blend material. The waveguide layer is made of InGaAsP and interposed between clad layers made of InGaP. With this arrangement, signal light and pumping light are incident upon the wavelength conversion element (DFG or SFG element) while the pumping light is fixed in a TE polarization direction. Alternatively, the signal light may be fixed in the TE polarization direction.

Abstract: An optical wavelength filter has a polarizer, an analyzer, and an optical waveguide, formed in a substrate displaying an acousto-optic effect, that guides light from the polarizer to the analyzer. A transducer formed on the substrate excites a surface acoustic wave, thus creating an acoustic beam. The amplitude of the surface acoustic wave is small at the two sides of the acoustic beam and larger in the middle. The optical waveguide enters the acoustic beam at a point on one of the two sides of the beam, then moves into the center of the beam, and exits the beam at another point on one of the two sides.

Abstract: A photonic switching method and a photonic switch utilizing the method are disclosed. Input electrical signals Ea.about.Ed are input through plural input ports 21a.about.21d are converted into optical signals with the pulse intervals of these input electrical signals being preserved unchanged. The converted optical signals are timing adjusted within the pulse interval and multiplexed in such a manner that these optical signals do not overlap with each other on the time axis. The resulting multiplexed optical signals are transferred to output ports 19a.about.19d. An optical signal, from among the multiplexed optical signals, which should be output at a target output port is separated by utilizing a mutual optical interactional function, for example, a four optical wave mixture.

Abstract: A polarization-independent optical wavelength filter uses a polarization splitter to divide an optical input signal into first and second signals with mutually perpendicular planes of polarization. The first signal propagates via a first optical path to a first end of an optical device, such as a TE-TM mode converter or a polarization-dependent filter, that acts selectively on the desired wavelength, then returns via a second optical path from a second end of the optical device to the polarization splitter. The second signal propagates via the second optical path to the second end of the same optical device, and returns from the first end via the first optical path to the polarization splitter. The polarization splitter recombines the returning signals into an optical output signal consisting only of the desired wavelength.

Abstract: An optical wavelength filter device capable of increasing the number of channels by narrowing a line width and widening a tuning width and comprising a first optical wavelength filter of a mode conversion type and a second optical wavelength filter of an interferometer type optically coupled with the first optical wavelength filter.

Abstract: A waveguide-type optical switch having a Y-branch structure composed of a Y-waveguide and branched waveguides provided with electrodes for electrically controlling the guide asynchronism thereof characterized in that the branched waveguides arranged at a converging angle of .theta..sub.1, and the Y-waveguide having a branching angle .theta..sub.2 (.theta..sub.2 >.theta..sub.1) connected to the branched waveguides. It is possible to shorten the length of the device of the Y-structured arrangement having the electrodes capable electrically of controlling the asynchronism of the branched waveguides.

Abstract: A waveguide-type optical device of the invention has a dielectric substrate, wave-guiding paths formed in the dielectric substrate, and electrodes for forming an operation-controlling electric field for the wave-guiding paths. A carrier capture layer is provided in a region into which carriers are injected from at least one of the electrodes.

Abstract: There is provided an optical wave-length filter which is constituted by a wave-guide route formed on a surface of a substrate; a front stage polarizer disposed in the wave-guide route for transmitting as an input light either TM mode light or TE mode light; a plurality of mode-converters disposed in the wave-guide route for mode converting one TM/TE-mode light transmitted from the front stage polarizer having a conversion wave length corresponding to an output light of the optical wave-length filter into the other TE/TM-mode light; and a rear stage polarizer disposed in the wave-guide route for transmitting as the output light of the optical wave-length filter the other TE/TM-mode light; the mode-converters being constituted by a finger-type electrode for control and a finger-type electrode for earthing interdigitally coupled for each other and disposed along the wave-guide route.

Abstract: Waveguide-type optical switch comprising a substrate, branched first and second waveguide routes provided thereon, and an electrode(s) provided on the substrate for controlling the propagation-constant difference or refractive index difference between the first and second waveguide routes. The interval between the first and second waveguide routes is extended towards the terminal end sides from the branch point side of the waveguide routes. The first and second waveguide routes are provided with a branched part. The first and second waveguide routes are provided with at least one part of the bending portions (II) connected to the branch part, respectively. The local branch angle between the first and second waveguide routes on the side of starting ends of the bending portions (II) is enlarged while the local branch angle between the first and second waveguide routes on the side of terminal ends at the bending portions (II) is reduced.

Abstract: An optical switching system has an optical transmission path for propagating signal beams, and a plurality of optical nodes for transmitting and receiving the signal beams. A reference beam source generates reference beams each having a particular wavelength. Each optical node generates a plurality of signal beams which are tuned to the wavelengths associated with the reference beams.

Abstract: A waveguide type photoswitch has a substrate on which a plurality of waveguide paths are provided in close proximity to each other. Electrodes are arranged along the waveguide paths in a coupling region of the paths. The distance between the waveguide paths is greater at the center of the coupling region than at opposite ends of the region, so that the coupling coefficient can be reduced at the central part of the coupling region and the coupling region itself can be shortened. The electrodes each is shorter than the coupling region to allow the operating voltage to be noticeably lowered and the operation speed to be increased.