Nippon Telegraph and Telephone Corporation

Nippon Telegraph and Telephone Public Corporation

Oki Electric Industry Co., Ltd.

The Furukawa Electric Co., Ltd.

Masao Kawachi

Kaname Jinguji

Norio Takato

Takao Edahiro

Mitsuho Yasu

Shoichi Suto

Yasuyuki Inoue

Yasufumi Yamada

Katsunari Okamoto

Satoru Tomaru

Akio Sugita

Hiroshi Terui

Masayuki Okuno

Kuniharu Kato

Shin Sumida

Morio Kobayashi

Akihiro Takagi

Hiroshi Takahashi

Ryo Nagase

Motohiro Nakahara

Akira Himeno

Akira Nagayama

Senichi Suzuki

Kiyoshi Kurosawa

Kunihiko Sasakura

Mitsuru Harada

Koichi Takiguchi

Fumihiko Yamamoto

Osamu Kogure

Fumiaki Hanawa

Shinichi Furukawa

Shintaro Sentsui

Mitsuhiro Makihara

Akira Morinaka

Hiroyuki Suda

Kyo Inoue

Yutaka Sasaki

Tsuneo Kanai

Shigefumi Hosokawa

Toshiaki Kuroha

Tadashi Miyashita

Tetsuo Miya

Yoshiaki Tachikawa

Jiro Utsunomiya

Atsushi Takahara

Shigeru Umemura

Yuji Akatsu

Katsumi Katoh

Syuichirou Inagaki

Hirobumi Kimura

Iida Saburo

Toshiyuki Kawashima

Ken-ichi Yukimatsu

Masayuki Okyno

Kazutosi Kato

Yoshinori Kato

Junichi Akahani

Hisao Takada

Kennosuke Fukami

Yasuro Furui

Katusunari Okamoto

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. In the first connective condition, the output port corresponding to a specific wavelength of the demultiplexer is connected to the input port corresponding to the specific wavelength of the receiver, and the output port corresponding to a specific wavelength of the transmitter is connected to the input port corresponding to the specific wavelength of the multiplexer; and in the second connective condition, the output port corresponding to a specific wavelength of the transmitter is connected to the input port corresponding to the specific wavelength of the receiver, and the output port corresponding to a specific wavelength of the demultiplexer is connected to the input port corresponding to the specific wavelength of the multiplexer.

Optical wavelength division multiplexing transmission network system using transmitting/receiving apparatuses having 2-input and 2-output optical path switching elements

An optical signal processor according to the present invention is an optical circuit of a lattice configuration. Its basic circuit structure comprises 3 dB directional couplers, two optical waveguides with equal optical path lengths, and two optical waveguides with different optical path lengths (an optical path difference of about 1 to 50 mm). Phase controllers for performing phase shift are provided on the optical waveguides. The portions with equal optical path lengths function as variable directional couplers, and variable directional couplers having arbitrary coupling rates can be constructed by changing the phase controllers on the optical waveguides with equal optical path lengths. As for an adaptive filter, there is adopted a construction in which a photodetector for withdrawing part of output is provided at the output port, and a feedback electric wiring for feedback control is laid.

Optical signal processor, method of its control, method of its

An integrated optical waveguide circuit includes a substrate; an optical wavelength multiplexer and an optical power splitter formed on a same surface of the substrate. The optical wavelength multiplexer is composed of a first slab optical waveguide, a second slab optical waveguide, a single or a plurality of input optical waveguides connected to the first slab optical waveguide at one end of the first slab optical waveguide, a plurality of arrayed optical waveguides arranged in parallel and having different lengths and connected to the first slab optical waveguide and the second slab optical waveguide, and a plurality of output optical waveguides arranged in parallel and connected to the second slab optical waveguide. The optical power splitter is composed of the second slab optical waveguide, one or more input optical waveguides, and the plurality of output optical waveguides arranged in parallel and connected to the second slab optical waveguide.

Integrated optical waveguide circuit and optical branch line test system

An optical switching module has an optical waveguide substrate mounted on an electronic circuit substrate. According to a first aspect of the invention, the optical waveguide substrate has thin-film heaters, and the electronic circuit substrate has trimmable thick-film resistors for adjusting current fed to the thin-film heaters. According to a second aspect of the invention, the optical switching module also has a pair of fiber pigtails butt-coupled to the optical waveguide substrate. The fiber pigtails are secured to the ends of a supporter, which is attached to a heat sink fastened below the electronic circuit substrate. According to a third aspect of the invention, the optical waveguide substrate is mounted in a depression in the electronic circuit substrate. The invention reduces the size of the optical switching module.

Compact optical switching module including thin-film heaters and trimmed

An optical device is presented which is useful for optical signal transmission and switching systems by multiplexing and demultiplexing optical signals in looped optical paths, consisting of a plurality of individual loop-back optical paths. The device is essentially a multi/demultiplexer having an arrayed waveguide grating disposed between a plurality of input sections and output sections which are joined by the plurality of individual loop-back optical paths. Because the modulated signals are looped back into the same optical paths using the same devices, problems of mismatching performance introduced by using different optical devices are avoided. The device processes individual optical signals of different wavelengths, minimizes splitting losses, and reduces noise components by producing narrow bandpass signals of high signal to noise ratio. Optical signal splitting and insertion, delay line memory and delay equalization circuits can all be handled by the same circuit configuration. The device is simple in construction, reliable in performance and economical in production.

Arrayed-wave guide grating multi/demultiplexer with loop-back optical

A waveguide-type optical matrix switch including as its switching element a Mach-Zehnder interferometer which includes two directional couplers and an optical phase shifter. The two directional couplers are arranged by placing two optical waveguides in close proximity at two positions on a substrate, and have an identical coupling ratio. The optical phase shifter is disposed over at least one of the two optical waveguides between the directional couplers. The two optical waveguides have an effective optical path length difference of half a wavelength of a light signal between the two directional couplers, and are intersected in the optical switch element. The waveguide-type optical matrix switch is little affected by fabrication errors in the coupling ratio of the directional couplers, and superior in the extinction ratio.

Waveguide-type optical matrix switch

In an optical MDF (main distributing frame) for interconnecting external subscriber optical lines (122) with office optical lines (131) through jumpering operation, a matrix waveguide (128, 129, 130) having a plurality of crosspoints coupled with external lines and office lines is used. The matrix waveguide has a groove (235 in FIG. 4A) at each crosspoint so that said crosspoint is switched ON or OFF depending upon whether said groove is filled with matching oil or not, so that one of the external lines is connected to the selected office line. Said matching oil has the same refractive index as that of waveguides. Each crosspoint groove is coupled with a respective oil pool (236), which supplies matching oil which has essentially the same refractive index as that of a waveguide to said groove. Switching at a crosspoint is carried out in a manner that a light signal in a waveguide goes straight through the crosspoint when a groove is filled with matching oil, and the light signal changes its direction at the crosspoint through total internal reflection when the groove is empty. A jumpering operation to connect or disconnect a crosspoint is carried out by a robot (133), which fills or pulls out matching oil in the oil pool at the designated coordinates. Each external line is branched by using an optical directional coupler (237) for test purposes, and one of the branch lines subject to test is selected by using a similar 1.times.N type matrix waveguide. (FIG. 4A)

Automated optical main distributing frame system

A guided-wave optical branching device having optical waveguides disposed on a substrate. The waveguides are partially arranged to be close to each other to form a tapered directional coupler in which the waveguides are point symmetrical or line symmetrical. Alternatively, the waveguides are neither line symmetrical nor point symmetrical. The tapered directional coupler reduces the wavelength dependence of the coupling ratio of the output power derived from the branching device. The widths of the waveguides in the parallel coupling region, the length of the coupling region in the symmetrical or asymmetrical directional coupler, the asymmetrical parameters or the like are set at values determined in accordance with the wavelength range used, so that the wavelength dependence of the coupling ratio of the power between the input port and the output port is reduced in a desired wavelength range, for example, 1.2 .mu.m-1.8 .mu.m.

Guided-wave optical branching device

A method for adjusting a characteristic of a guided-wave optical circuit which includes one or more waveguides formed by a substrate, a cladding layer formed on the substrate, and a core portion having one or more cores embedded in the cladding layer. The method is carried out by producing a reversible thermal hysteresis phenomenon, after the clading layer and core portion have been formed. The thermal hysteresis phenomenon is produced in a thermal hysteresis produced region preselected so as to include at least a portion of the cladding layer and/or the core portion, thereby adjusting a refractive index difference between the cladding layer and the core portion. To produce a reversible thermal hysteresis phenomenon, the following steps are carried out: raising the temperature of the thermal hysteresis produced region to a predetermined temperature; maintaining the predetermined temperature of the thermal hysteresis produced region for a predetermined time period; and cooling the thermal hysteresis produced region at a predetermined cooling rate. At least one of the values of the predetermined temperature, predetermined time period, and predetermined cooling rate is controlled so that the refractive index difference between the cladding layer and the core portion is adjusted to a desired value, thereby adjusting the characteristic of the guided-wave optical circuit.

Guided-wave optical circuit and method for adjusting a characteristic

A guided-wave optical branching component is composed of a Mach-Zehnder interferometer having two or more directional couplers. A slight difference .DELTA.L in the optical-path length is provided in two or more optical waveguides connecting the two or more directional couplers. The difference of the optical-path length is less than the shortest wavelength in the operational wavelength region of the guided-wave optical branching component, and the coupling ratio of each of the two directional couplers monotonically increases with wavelength in the operational wavelength region. By using the optical branching components thus constructed (i.e., Mach-Zehnder interferometer type 3-dB optical coupler) in conjunction with a phase shifter, a Mach-Zehnder interferometer type optical switch can be achieved.

Guided-wave optical branching components and optical switches

An integrated optical device includes a substrate; a single-mode optical waveguide having a cladding layer disposed on the substrate and a core portion embedded in the cladding layer for transmitting light therethrough; and a stress applying film disposed on a desired portion of the cladding layer for adjusting stress-induced birefringence of the single-mode optical waveguide by irreversibly changing the stress exerted on the core portion by a trimming technique. The integrated optical device can be manufactured by the steps of forming a cladding layer on a substrate; forming a single-mode optical waveguide having a core portion embedded in the cladding layer for transmitting light therethrough; and forming, on the cladding layer, a stress applying film for exerting a stress on the single-mode optical waveguide to irreversibly change the stress by trimming the film. The device exhibits a precisely adjusted birefringence and a desired polarization dependence or independence, and is effective for constructing an integrated optical device for optical communication, for optical sensing or for optical signal processing, in which the polarization characteristics play an important role.

Integrated optical device and method for manufacturing thereof

An integrated optical device includes a substrate; a single-mode optical waveguide having a cladding layer disposed on the substrate and a core portion embedded in the cladding layer for transmitting light therethrough; and a stress applying film disposed on a desired portion of the cladding layer for adjusting stress-induced birefringence of the single-mode optical waveguide by irreversibly changing the stress exerted on the core portion by a trimming technique. The integrated optical device can be manufactured by the steps of forming a cladding layer on a substrate; forming a single-mode optical waveguide having a core portion embedded in the cladding layer for transmitting light therethrough; and forming, on the cladding layer, a stress applying film for exerting a stress on the single-mode optical waveguide to irreversibly change the stress by trimming the film. The device exhibits a precisely adjusted birefringence and a desired polarization dependence or independence, and is effective for constructing an integrated optical device for optical communication, for optical sensing, or for optical signal processing, in which the polarization characteristics play an important role.

A single-polarization single-mode optical fiber comprises a core made of silica glass, a clad surrounding the core and made of silica glass having a smaller index of refraction than the glass comprising the core, a pair of stress applying members symmetrically disposed on the clad and made of silica glass having different thermal expansion coefficient from that of the clad, spacers interposed between the stress applying members and made of silica glass having substantially the same thermal expansion coefficient as the clad, and a jacket surrounding the spacers, stress applying members. The jacket is also made of silica glass and has a smaller expansion coefficient than the stress applying members. The optical fiber of this invention has an excellent polarization preserving characteristic, low loss, long length, and stable characteristics.

Method for making single-polorization, single mode optical fibers

In a single mode optical waveguide having a substrate, a cladding layer formed on the substrate, a core portion embedded in the cladding layer, and an elongated member for applying a stress to the core portion or a stress relief groove for relieving a stress from the core portion in the cladding layer along the core portion. The position, shape and material of the elongated member or the groove are determined in such a way that stress-induced birefringence produced in the core portion in accordance with a difference in thermal expansion coefficient between the substrate and the single mode optical waveguide is a desired value.

Single mode channel optical waveguide with a stress-induced

A hybrid optical integrated circuit having a high-silica glass optical waveguide formed on a silicon substrate, an optical fiber and an optical device coupled optically to the optical waveguide, and an optical fiber guide and an optical device guide on the substrate for aligning the optical fiber and the optical device at predetermining positions, respectively, relative to the optical waveguide. Islands carrying electrical conductors are disposed on the substrate. A first electrical conductor film is formed on the substrate. Second electrical conductor films are formed on the top surfaces of the optical waveguide, the optical fiber guide, the optical device guide and the islands and are electrically isolated from the first electrical conductor film. An electrical conductor member is provided to feed electric power from the first and second electric conductor films to the optical device which needs the power supply. The optical waveguide, the optical fiber guide, the optical device guide and the islands are formed from the same high-silica glass optical waveguide film. Alignment of various portions is facilitated when assembling the circuit. A high coupling efficiency is realized with a low cost.

Hybrid optical integrated circuit

Growing community of inventors

Mito, Japan

Masao Kawachi