Abstract: The present invention provides a 90-degree hybrid capable of miniaturization and also capable of a stable operation in a wide band. According to an embodiment of the present invention, a PLC-type 90-degree hybrid comprises: a PLC chip having a planar lightwave circuit formed therein; and a 90-degree hybrid circuit formed in the planar lightwave circuit, mixing a modulated signal light and an LO light to separate the signal light into quadrature components I and Q, and outputting the same. The 90-degree hybrid circuit includes: two Y-branch couplers each branching the signal light and the LO light; and two wavelength-independent directional couplers which cause LO lights passing through two paths and signal lights passing through two paths to interfere with each other, respectively. The above-described paths include waveguides having mutually inverted shapes and waveguides having an identical shape, and have a shape substantially symmetrical with respect to the signal light.

Abstract: A waveguide-type optical circuit comprises an optical coupler being an optical branch coupler constructed from waveguide cores which are closely arranged to each other, and dummy patterns that lay along sides of the waveguide cores in the optical coupler for preventing optical major axes of the waveguide cores from inclining.

Abstract: Disclosed are a PLC-type delay demodulation circuit and a PLC-type optical interferometer capable of reducing the size of a PLC chip with respect to the arrangement of various kinds of light output waveguides. In a PLC-type delay demodulation circuit, arm waveguides of a first MZI and arm waveguides of a second MZI are formed so as to overlap each other in the same region of a planar lightwave circuit. The optical paths of the MZIs are arranged such that the propagation directions of two DQPSK signals branched by a Y-branch waveguide are opposite to each other.

Abstract: The present invention provides an optical waveguide circuit which includes: a waveguide made of a material whose temperature coefficient of refractive index has a second-order component; a groove formed in a part of the waveguide; and a compensation material having a temperature coefficient of refractive index different from the temperature coefficient of refractive index of the waveguide, and in which a normal line of an interface between the groove and the waveguide, and an optical axis of light propagating through the waveguide intersect at a predetermined intersection angle, and the predetermined intersection angle is determined so as to reduce a second-order component of optical path length change of the waveguide due to the second-order component of temperature coefficient of the refractive index of the waveguide.

Abstract: The present invention provides a Mach-Zehnder interferometer-arrayed waveguide grating (MZI-AWG) and a planar light-wave circuit chip in which a certain number of chips can be secured without degradation of MZI-AWG characteristics. An MZI-AWG (10) includes a Mach-Zehnder interferometer (MZI) (20) and an arrayed waveguide grating (AWG) (30) using the MZI for an input waveguide. The FSR of the MZI and the channel spacing of the AWG coincide with each other. An input side coupler (21) and an output side coupler (22) of the MZI are disposed on a straight line connecting a center part (a0) in one end surface (31a) of an input slab waveguide (31) and a center part (b0) in the other end surface (31b) which is a circular-arc shaped end surface having a radius of a focal length (Lf) from the center part (a0).

Abstract: The present invention provides a 90-degree hybrid capable of miniaturization and also capable of a stable operation in a wide band. According to an embodiment of the present invention, a PLC-type 90-degree hybrid comprises: a PLC chip having a planar lightwave circuit formed therein; and a 90-degree hybrid circuit formed in the planar lightwave circuit, mixing a modulated signal light and an LO light to separate the signal light into quadrature components I and Q, and outputting the same. The 90-degree hybrid circuit includes: two Y-branch couplers each branching the signal light and the LO light; and two wavelength-independent directional couplers which cause LO lights passing through two paths and signal lights passing through two paths to interfere with each other, respectively. The above-described paths include waveguides having mutually inverted shapes and waveguides having an identical shape, and have a shape substantially symmetrical with respect to the signal light.

Abstract: The invention provides a PLC-type DP-QPSK demodulator that reduces connection loss between a polarization beam splitter and a 90-degree hybrid circuit and aims at reducing the manufacturing cost and an optical transmission system using the same. In an embodiment of the invention, a PLC-type DP-QPSK demodulator that receives a DP-QPSK signal includes one PLC chip having a planar lightwave circuit. Input ports and output ports of signal light are provided at an input end and at an output end of the PLC chip, respectively. Within the planar lightwave circuit, there are integrated a polarization beam splitter that splits the DP-QPSK signal into an X-polarization QPSK signal and a Y-polarization QPSK signal, and two 90-degree hybrid circuits that mix the X-polarization QPSK signal and local oscillation light and the Y-polarization QPSK signal and local oscillation light, respectively, split each QPSK signal into orthogonal components I, Q and output them.

Abstract: An arrayed waveguide grating type optical multiplexer and demultiplexer which reduces a package size although plural arrayed waveguide gratings are included, is provided, comprising plural arrayed waveguide gratings which are provided in parallel to one another on a substrate and each of which has a first waveguide, a first slab waveguide, an arrayed waveguide, a second slab waveguide, and a second waveguide, and also includes a waveguide chip divided into a first and second separated waveguide chip in the first or second slab waveguide in each of the arrayed waveguide gratings and a compensation member compensating a temperature dependent shift of a light transmission center wavelength in the arrayed waveguide grating by relatively moving the first and second waveguide chip when expanded or contracted according to a temperature change. The waveguide chip has a shape bending along a bending direction of the arrayed waveguide.

Abstract: An arrayed waveguide grating type optical multiplexer and demultiplexer which achieves a low crosstalk even when temperature changes is provided, comprising, on a substrate, a waveguide chip in which an arrayed waveguide grating is formed that has a first waveguide, a first slab waveguide, an arrayed waveguide, a second slab waveguide, and a second waveguide, the waveguide chip being divided into two by any of the first and second slab waveguide, and includes a first glass plate to which one side of the arrayed waveguide grating divided into two in the waveguide chip is fixed, a second glass plate to which the other side thereof is fixed, and a compensation member compensating a temperature dependent shift of a light transmission center wavelength of the arrayed waveguide grating, wherein a part for the arrayed waveguide is not fixed to any of the first and second glass plates.

Abstract: The PLC-type delay demodulation circuit includes a planar lightwave circuit that is provided on one PLC chip and demodulates a DQPSK signal. The planar lightwave circuit includes a Y-branch waveguide that branches a DQPSK-modulated optical signal into two optical signals and first and second MZIs that delay the branched optical signals by one bit. A wave plate is provided in central portions of first and second arm waveguides of the first MZI and first and second arm waveguides of the second MZI in such a manner that the wave plate intersects all of the four arm waveguides, the four arm waveguides being close to one another in a portion where the wave plate is provided.

Abstract: A PLC-type delay demodulation circuit includes a planar lightwave circuit that is provided on one PLC chip and demodulates a DQPSK signal. The planar lightwave circuit includes a Y-branch waveguide that branches a DQPSK-modulated optical signal into two optical signals and first and second MZIs that delay the branched optical signals by one bit. The length of a short arm waveguide of the first MZI is different from the length of a short arm waveguide of the second MZI, and the length of an optical path from the Y-branch waveguide to output ports of the first MZI through the short arm waveguide of the first MZI is equal to that of an optical path from the Y-branch waveguide to output ports of the second MZI through the short arm waveguide of the second MZI.

Abstract: A waveguide-type optical circuit comprises an optical coupler being an optical branch coupler constructed from waveguide cores which are closely arranged each other, and dummy patterns that lay along sides of the waveguide cores in the optical coupler for preventing optical major axes of the waveguide cores from inclining.

Abstract: The present invention provides a wavelength multiplexer/demultiplexer comprising a Mach-Zehnder interferometer and an arrayed waveguide diffraction grating, the wavelength multiplexer/demultiplexer having a simple configuration and being capable of reducing the degradation in the temperature compensation characteristics of a temperature compensation material provided in the Mach-Zehnder interferometer or the peeling-off of the temperature compensation material, and a method of manufacturing the same. A wavelength multiplexer/demultiplexer comprises an AWG including two separated slab waveguides and an MZI including two arm waveguides.

Abstract: A semiconductor laser module includes a semiconductor laser section, a light selecting section, and an optical converting section. The semiconductor laser section includes a semiconductor laser substrate, a plurality of semiconductor laser elements mounted on the semiconductor laser substrate, and a first temperature adjusting element for adjusting temperature of the semiconductor laser elements. The light selecting section includes a light selecting element substrate and a light selecting element mounted on the light selecting element substrate and optically connected to the semiconductor laser elements, which selects laser light output from at least one of the semiconductor laser elements.

Abstract: The tunable dispersion compensator 10 of the present invention comprises: the Mach-Zehnder interferometers (MZIs) 21 to 25 cascaded on a planar lightwave circuit; and the tunable couplers 31 to 34 connected to between each corresponding pair of the MZIs respectively. The Y-branch waveguide 15 and 16 are used for connecting to between the MZIs 21, 25 as both end sides and the input/output optical waveguides 13, 14 respectively. The waveguide loop mirror 40 is connected to the final stage MZI 25 among the MZIs 21 to 25 which an incident light is propagated last therethrough. The half-wave plate 50 is inserted to the loop waveguide 41 of the waveguide loop mirror 40. And it becomes able to enhance (double) the amount of tunable dispersion because an input light signal is passed twice through the similar path by the waveguide loop mirror 40.

Abstract: An athermal AWG module 10 comprises: an AWG 11 having waveguides partially divided to separate a chip, separated chips being connected by a compensation plate 33 to achieve temperature-independence; an athermal AWG chip 12 having a substrate and the AWG 11 formed on the substrate; a package 13 having an opening 14 and accommodating the athermal AWG chip 12; and a cover for blocking the opening 14. The athermal AWG chip 12 is fully covered with a gelled refractive index matching agent 16 that is matched in refractive index to the waveguides of the AWG 11. As the gelled refractive index matching agent 16 is excellent in water resistance and hardly passes water, the adhesive agent for fixing the compensation plate 33 to the surfaces of the separated two chips is prevented from being deteriorated due to ingress of water, thereby enhancing the reliability.

Abstract: Two Mach-Zehnder optical interferometer circuits are accurately point-symmetrically connected to each other to form a first point-symmetrically connected optical interferometer circuit constituting a light input side circuit. Optical signals having a plurality of wavelengths are input to a light input terminal. A second point-symmetrically connected optical interferometer circuit having the same functional structure as the first point-symmetrically connected optical interferometer circuit is connected to a through port, which is an output terminal of the light input side circuit, as a first light output side circuit. A cross port, which is the other output terminal of the light input side circuit, is connected to a second light output side circuit having at least one of Mach-Zehnder optical interferometer circuits whose transmittance characteristics are different from those of the Mach-Zehnder optical interferometer circuits.

Abstract: The delay demodulation device 1 comprises: an input waveguide 2 which receives DQPSK signals; a Y-branch waveguide 3 which splits the input waveguide 2; a first Mach-Zehnder interferometer 4; and a second Mach-Zehnder interferometer 5. Both end of two arm-waveguides 8, 9 of the first Mach-Zehnder interferometer 4 and both ends of two arm-waveguides 12, 13 of the second Mach-Zehnder interferometer 5 are angled toward the center portion of a planar lightwave circuit (PLC) 1A. Because of the angle, the length of the two arm-waveguides 8, 9 of the first Mach-Zehnder interferometer 4 and the length of the two arm-waveguides 12, 13 of the second Mach-Zehnder interferometer 5 in Z-direction can be shortened, and input couplers 6,10 and output couplers 7,11 of each Mach-Zehnder interferometers in Z-direction can be shortened as well. The area occupied by each Mach-Zehnder interferometers 4, 5 are also reduced.

Abstract: The delay demodulation device 1 comprises an input waveguide 2 which receives DQPSK signals; a Y-branch waveguide 3 which splits the light waveguide 2; a first Mach-Zehnder interferometer (MZI) 4; and a second Mach-Zehnder interferometer 5. Both ends of the arm-waveguides 8, 9 of the MZI 4 and the both ends of the arm-waveguides 12, 13 of the MZI 5 are bent toward the center portion of the planar lightwave circuit (PLC) 1A. Thereby, the length of the arm-waveguides 8, 9 of the MZI 4 and the length of the arm-waveguides of the MZI 5 are shortened in the Z-direction. And, the length of the input couplers 6, 10 and the output couplers 7, 11 of the MZIs 4, 5 are shortened in the Z-direction. Therefore, the area covered by the MZIs 4, 5 can be made smaller.

Abstract: An arrayed waveguide grating includes input waveguides, an input slab waveguide, n output waveguides, an output slab waveguide, and an arrayed waveguide. Gaps are formed in the output waveguides other than the output waveguides of both sides of an array of the output waveguides, respectively, such that loss increases toward the central side of the array. Sizes of the gaps in the output waveguides increase toward the central side of the array.