Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: The present invention provides an optical functional circuit where a holographic wave propagation medium is applied and a circuit property is excellent such as small transmission loss and crosstalk. The optical functional circuit where a plurality of circuit elements are formed on a substrate includes the wave propagation medium for converting an optical path of a leakage light so that the leakage light that is not emitted from a predetermined output port of the circuit element is not coupled to a different circuit element. This wave propagation medium is constituted by an optical waveguide that is provided with a clad layer formed on the substrate and a core embedded in the clad layer, and a part of the optical waveguide is formed in accordance with a refractive index distribution which is multiple scattered.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: The present invention provides an optical functional circuit where a holographic wave propagation medium is applied and a circuit property is excellent such as small transmission loss and crosstalk. The optical functional circuit where a plurality of circuit elements are formed on a substrate includes the wave propagation medium for converting an optical path of a leakage light so that the leakage light that is not emitted from a predetermined output port of the circuit element is not coupled to a different circuit element. This wave propagation medium is constituted by an optical waveguide that is provided with a clad layer formed on the substrate and a core embedded in the clad layer, and a part of the optical waveguide is formed in accordance with a refractive index distribution which is multiple scattered.

Abstract: The present invention has been achieved to provide a novel optical transmission system realizing high-speed optical transmission over greater distance by suppressing waveform degradation caused by mode dispersion and mode transition in a multimode optical transmission line. The optical transmission system of the present invention includes: an optical transmitter for transmitting incoherent light; an excitation mechanism for exciting a predetermined mode in the incoherent light transmitted from the optical transmitter; a multimode optical transmission line for transmitting the incoherent light transmitted from the excitation mechanism; a transmission mechanism for transmitting a predetermined mode in the incoherent light transmitted from the excitation mechanism; and an optical receiver for receiving the incoherent light transmitted from the transmission mechanism or the incoherent light transmitted from the transmission mechanism.

Abstract: A wave transmission medium includes an input port 3-1 and an output port 3-2. A field distribution 1 and a field distribution 2 are obtained by numerical calculations. The field distribution 1 is a field distribution of the propagation light (forward propagation light) launched into the input port 3-1. The field distribution 2 is a field distribution of the phase conjugate light (reverse propagation light) resulting from reversely transmitting from the output port side an output field that is expected to be output from the output port 3-2 when an optical signal is launched into the input port 3-1. According to the field distributions 1 and 2, a spatial refractive index distribution is calculated such that the phase difference between the propagation light and reverse propagation light is eliminated at individual points (x, z) in the medium.

Abstract: A wave transmission medium includes an input port 3-1 and an output port 3-2. A field distribution 1 and a field distribution 2 are obtained by numerical calculations. The field distribution 1 is a field distribution of the propagation light (forward propagation light) launched into the input port 3-1. The field distribution 2 is a field distribution of the phase conjugate light (reverse propagation light) resulting from reversely transmitting from the output port side an output field that is expected to be output from the output port 3-2 when an optical signal is launched into the input port 3-1. According to the field distributions 1 and 2, a spatial refractive index distribution is calculated such that the phase difference between the propagation light and reverse propagation light is eliminated at individual points (x, z) in the medium.

Abstract: A multistage Mach-Zehnder interferometer type optical circuit including any number of symmetrical Mach-Zehnder interferometers and any number of asymmetrical Mach-Zehnder interferometers connected in cascade. In the optical circuit, low coherence light is used first to obtain individual phase control conditions of the symmetrical Mach-Zehnder interferometers without being affected by the asymmetrical Mach-Zehnder interferometers. Second, phase control conditions of the individual asymmetrical Mach-Zehnder interferometers are obtained by controlling the symmetrical Mach-Zehnder interferometers based on the first phase control conditions.

Abstract: The object of the present invention is to provide a full-mesh optical wavelength division multiplexing transmission network device which is capable of exhibiting excellent communication quality and being mass produced, by reducing the accumulation number of coherent crosstalk lights, without any modification of constituent components constituting the conventional one. In the full-mesh optical wavelength division multiplexing transmission network device, provided is an N×N wavelength multi/demultiplexer having a periodic wavelength demultiplexing property in input/output combination, which performs input/output from/to first and second I/O port groups for optical signals and allows lightwaves traveling in opposite directions not to interfere with each other within the circut, thus reducing the accumulation number of coherent crosstalk lights in WDM wavelength lights and improving S/N of a received light.

Abstract: A multistage Mach-Zehnder interferometer type optical circuit including any number of symmetrical Mach-Zehnder interferometers and any number of asymmetrical Mach-Zehnder interferometers connected in cascade. In the optical circuit, low coherence light is used first to obtain individual phase control conditions of the symmetrical Mach-Zehnder interferometers without being affected by the asymmetrical Mach-Zehnder interferometers. Second, phase control conditions of the individual asymmetrical Mach-Zehnder interferometers are obtained by controlling the symmetrical Mach-Zehnder interferometers based on the first phase control conditions.

Abstract: An optical wavelength division multiplexing transmission network system having a star-topology network is disclosed, which comprises an arrayed-waveguide grating type multiplexing/demultiplexing circuit having N input ports and N output ports, and N transmitting/receiving apparatuses, each apparatus including a transmitter, receiver, demultiplexer, multiplexer, and N 2-input and 2-output optical path switching elements corresponding to N wavelengths, so as to cope with a damage to a transmitting or receiving portion corresponding to a specific wavelength. Each switching element is independently switched between first and second connective conditions.

Abstract: In a light waveguide circuit including a plurality of waveguides having different length, a material (10) having a temperature coefficient of a refractive index including a symbol different from that of a temperature coefficient of an effective refractive index of the waveguide (4) is charged into a groove (12) formed by removing the upper clad and the core from the waveguide (4), or a groove (12) formed by removing the upper clad, the core and the lower clad from the waveguide (4). A difference in length of the removed portions between adjacent waveguides is proportional to a difference in length of the waveguides which were not removed and remained.