Hitachi Cable, Inc.

Fujitsu Corporation

Yokogawa Electric Corporation

Hideaki Arai

Hisato Uetsuka

Ryoji Suzuki

Takafumi Chiba

Korenori Tamura

Dai Kobayashi

Takeshi Hoshida

Yasuyuki Suzuki

Hiroshi Onaka

Takafumi Terahara

George Ishikawa

Kentaro Nakamura

Akira Miura

Hiroyuki Matsuura

Jens Rasmussen

Morio Wada

Akihiko Isomura

Kenji Akiba

Koichi Maru

Masahiro Okawa

Satoshi Takasugi

Masahiro Hikage

An interferometer for demodulating a differential M-phase shift keying signal includes a PLC type interferometer main body, a heating portion that heats the PLC type interferometer main body, and an intermediate member having a higher stiffness than that of the PLC type interferometer main body, for bonding the PLC type interferometer main body and the heating portion with each other while being sandwiched therebetween. A linear expansion coefficient difference between the PLC type interferometer main body and the intermediate member is equal to or smaller than 4.5&#xd7;10/&#xb0; C., and a thermal conductivity difference between the PLC type interferometer main body and the intermediate member is equal to or larger than 10 W/mK. A phase of an optical signal flowing through the interferometer is adjusted by using the heating portion and a second heating portion.

Interferometer for demodulating differential M-phase shift keying signal

A waveguide-type optical multiplexer/demultiplexer with low crosstalk characteristics and reduced wavelength dispersion is provided. A waveguide-type optical multiplexer/demultiplexer comprising, first, second and third optical multiplexer/demultiplexer circuits connected in multistage, each multiplexer/demultiplexer circuit has four input-output ports, third input-output port of first optical multiplexer/demultiplexer circuit is connected to third input-output port of second optical multiplexer/demultiplexer circuit, and fourth input-output port of first optical multiplexer/demultiplexer circuit is connected to fourth input-output port of third optical multiplexer/demultiplexer circuit, when wavelength division multiplex signals having wavelength &#x3bb;, &#x3bb;, &#x3bb;, &#x3bb;, &#x3bb;, &#x3bb;. . . are input through first input-output port of first optical multiplexer/demultiplexer circuit, multiplex signals of odd wavelength &#x3bb;, &#x3bb;, &#x3bb;. . . are output from first input-output port of second optical multiplexer/demultiplexer circuit, and multiplex signals of even wavelength &#x3bb;, &#x3bb;, &#x3bb;. . . are output from first input-output port of third optical multiplexer/demultiplexer circuit.

Waveguide-type optical multiplexer/demultiplexer

In an optical multiplexer/demultiplexer comprising optical multiplexer/demultiplexer circuits connected in multistage, the optical multiplexer/demultiplexer circuits each have two input ports and two output ports, an optical path, through which input optical signals with predetermined wavelengths are output after multiplexing and demultiplexing, varies depending upon the input port; the optical paths in each of the optical multiplexer/demultiplexer circuits have mutually opposite wavelength dispersion characteristics, and one of the optical paths in a first optical multiplexer/demultiplexer circuit is connected to one of the optical paths, in a second optical multiplexer/demultiplexer circuit, having wavelength dispersion characteristics opposite to the optical path in the first optical multiplexer/demultiplexer circuit. By virtue of this construction, an optical multiplexer/demultiplexer can be realized which causes no significant wavelength dispersion and, at the same time, has excellent wavelength flatness characteristics in passband.

Optical multiplexer/demultiplexer

In the optical multiplexer/demultiplexer according to the invention, an MMI (multi mode interference) coupler having a percentage coupling of about 50% is used as first and second optical couplers, and a directional coupler having a percentage coupling of less than 10% is used as third and fourth optical couplers. By virtue of this constitution, the optical multiplexer/demultiplexer according to the invention has a small dependency upon wavelength and can be used in a wide waveband, is less susceptible to a preparation error, and, at the same time, has good wavelength flatness in passband and a wide rejection band.

A glass wave guide element, which is small in size and amenable to integration and mass-production, and a method of manufacturing the glass wave guide element are provided. The glass wave guide element includes a core having a diffraction grating formed on an under cladding, an over cladding covering the core and a heater for changing the Bragg wavelength of the diffraction grating, the heater being arranged on the over cladding. The core and a central portion of both claddings in a surrounding portion around the core are formed in a state of being continuously separated along a longitudinal direction of the core from the substrate through a gap, and the core and the surrounding portion around the core are formed in a state of being spatially intermittently separated in a width direction of the core from a surrounding portion of both claddings through a gap. The wave guide is formed by etching to form gaps spaced intermittently along both sides of a core with under cladding and over cladding, and then removing a patterned silicon film from underneath the core.

Glass wave guide element and method of manufacturing the same

An optical wavelength multiplexer/demultiplexer, comprising: a substrate: and, provided thereon, input waveguides, output waveguides, an array waveguide diffraction grating comprising a plurality of waveguides with a predetermined difference in length being provided between the waveguides, an input slab waveguide for connecting the input waveguides to the array waveguide diffraction grating, an output slab waveguide for connecting the output waveguides to the array waveguide diffraction grating, and multimode waveguides, for example, tapered waveguides and parabolic waveguides, provided in a connecting section between the input waveguides and the input slab waveguide. The output slab waveguide may have a smaller radius than the input slab waveguide to narrow the width of the electric field distribution on the output side. The above construction can bring wavelength characteristics to a rectangular form to broaden the transmission band and at the same time can reduce the loss.

Optical wavelength multiplexer/demultiplexer

A glass wave guide element, which is small in size and amenable to integration and mass-production, and a method of manufacturing the glass wave guide element are provided. The glass wave guide element includes a core 3 having a diffraction grating formed on an under cladding 2, an over cladding 4 covering the core 3 and a heater 6 for changing the Bragg wavelength of the diffraction grating, the heater being arranged on the over cladding 4. The core 3 and a central portion (2B, 4B) of both claddings in a surrounding portion around the core 3 are formed in a state of being continuously separated along a longitudinal direction of the core 3 from the substrate 1 through a gap 5, and the core 3 and the surrounding portion around the core 3 are formed in a state of being spatially intermittently separated in a width direction of the core 3 from a surrounding portion (2A, 2C, 4A, 4C) of both claddings through a gap.

A waveguide type grating device according to the invention includes a quartz substrate, a cladding and two waveguides. Waveguides are arranged to provide an input port, an Add port, an output port, a Drop port, directional 3 dB couplers, core width-changing portions, and grating portions each interposed between core width-changing portions. The width of core is changed between each non-grating portion and each grating portion in an adiabatic structure, for example, a parabolic structure. For this structure, a waveguide type grating device is structured to suppress the increase in wavelength loss due to coupling from progressive propagation mode to regressive radiation mode, with less cost and smaller dimension.

Waveguide type grating device

A width of a core in an optical waveguide is decreased in accordance with a value of a predetermined equation, as a distance of a position of the core to the center position thereof is decreased. Consequently, a rectangular spectrum property having no ripple is obtained on a lower wavelength side in a reflection grating. In addition, the width of the core is changed at the position Z in the direction of light propagation, while a UV light is radiated to the core, so that a periodically striated distribution of refractive indices having an envelope which is changed in accordance with a value of '.vertline.sin(C.multidot.Z).vertline./.vertline.C.multidot.Z.vertline.' is formed in the core of the optical waveguide, and a phase of a light to be propagated in the direction of the light propagation is shifted at the position Z as defined below by .pi..

Optical device formed with grating therein, add/drop filter using same,

A width of a core in an optical waveguide is decreased in accordance with a value of a predetermined equation, as a distance of a position of the core to the center position thereof is decreased. Consequently, a rectangular spectrum property having no ripple is obtained on a lower wavelength side in a reflection grating. In addition, the width of the core is changed at the position Z in the direction of light propagation, while a UV light is radiated to the core, so that a periodically striated distribution of refractive indices having an envelope which is changed in accordance with a value of '.vertline.sin (C.multidot.Z).vertline./.vertline.C.multidot.Z.vertline.' is formed in the core of the optical waveguide, and a phase of a light to be propagated in the direction of the light propagation is shifted at the position Z as defined below by .pi.. Z=m.pi./C(m= - - - , -3,-2,-1,1,2,3, - - - ) Thus, a rectangular spectrum property is obtained in a low reflection grating.

An optical device having a switching function has a waveguide filter for switching whether input signal light of including at least one specific wavelength should be transmitted or reflected. The input signal lights of wavelength of .lambda..sub.1 .about..lambda.n are transmitted to the input waveguide. When the waveguide filter is off, the signal lights of all wavelength are transmitted to the output port. When the waveguide filter is on, the signal light of wavelength of .lambda..sub.2 .about..lambda.n are transmitted, but the signal light of wavelength of .lambda..sub.2 is reversed and output to the drop port. If the thin film heaters are off, a signal light of wavelength of .lambda..sub.1 is output (dropped) from the drop port. If the thin film heaters are on, it is reversed and transmitted to the output port.

Optical device having switching function

A guided-wave optical multi/demultiplexer is capable of providing a wide wavelength band freely. Each of two directional couplers is constructed so that the coupling ratio of light intensity in the wavelength .lambda..sub.2 is at least 50% and the coupling ratio of light intensity in the wavelength .lambda..sub.3 having a wavelength band in close proximity to the wavelength .lambda..sub.1 is 0% or 100%, the light in the wave band containing the wavelength .lambda..sub.1 and the wavelength .lambda..sub.3 and the light in the wave band containing the wavelength .lambda..sub.2 being multiplexed and demultiplexed.

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Ibaraki, Japan

Hideaki Arai