Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Other

Yasuyuki Inoue

Yasuhiro Hida

Yoshinori Hibino

Takashi Saida

Tsutomu Kitoh

Mikitaka Itoh

Toshikazu Hashimoto

Hiroshi Takahashi

Shin Kamei

Manabu Oguma

Shinji Ando

Masayuki Okuno

Takashi Sawada

Takayuki Mizuno

Takuya Tanaka

Akio Sugita

Akimasa Kaneko

Yasuaki Hashizume

Kuninori Hattori

Masahiro Yanagisawa

Makoto Abe

Yusuke Nasu

Yasufumi Yamada

Katsunari Okamoto

Motohaya Ishii

Masao Kawachi

Yohei Sakamaki

Akira Himeno

Kuniharu Kato

Norio Takato

Fumiaki Hanawa

Hiroaki Yamada

Toshimi Kominato

Yutaka Miyamoto

Kenji Yokoyama

Masahito Tomizawa

Takashi Kurihara

Akira Hirano

Toshio Watanabe

Takashi Goh

Seiji Toyoda

Toshiaki Tamamura

Saburo Imamura

Motohiro Nakahara

Koichi Arishima

Seiko Mitachi

Shoichi Hayashida

Naoki Ooba

Shoichiro Kuwahara

Tomohiro Shibata

Shin Sumida

Taisuke Oguchi

Senichi Suzuki

Kaname Jinguji

Takao Kimura

Fumihiko Yamamoto

Fumihiro Ebisawa

Tetsuyoshi Ishii

Shinichi Furukawa

Shigeo Nagashima

Akira Morinaka

Hiroyuki Suda

Kazumasa Takada

Takashi Yoshida

Tsutomu Kitou

Daisuke Ogawa

Masaki Kohtoku

Mikitaka Ito

Masaki Koutoku

Tetsuo Yoshizawa

Toru Maruno

Yuji Moriya

Yasumori Ohmura

Toshiumi Kominato

Masahito Ntt Intel Property Center Tomizawa

Yutaka Ntt Intellectual Property Center Miyamoto

Shoichirou Ntt Intel Property Center Kuwahara

Akira Ntt Intellectual Property Center Hirano

An optical wavelength multi/demultiplexing circuit is provided in which temperature dependence at a transmission center wavelength remained in an athermalized AWG is compensated. An AWG according to an embodiment of the present invention is compensated for the main temperature dependence at the transmission center wavelength. The AWG comprises an optical splitter, a first and second arm waveguides, an optical mode combining coupler and a multimode waveguide between an input/output waveguide and a slab waveguide. The optical mode combining coupler couples fundamental mode light from the first arm waveguide as fundamental mode and the fundamental mode light from the second arm waveguide as first mode. The multimode waveguide is capable of propagating the fundamental and first mode light. This AWG is configured such that the temperature dependence remained in the arrayed waveguide grating is compensated by changing the optical path length difference between the first and second arm waveguides with temperature.

Arrayed waveguide grating

An arrayed waveguide grating optical multiplexer/demultiplexer according to the present invention including an input channel waveguide, an input slab waveguide, an arrayed waveguide, a polarization dependence eliminating means, an output slab waveguide, a temperature compensating means, and an output channel waveguide is characterized in that the temperature compensating means compensates for the temperature dependence of the optical path lengths in the channel waveguides of the arrayed waveguide, and the polarization dependence eliminating means eliminates the temperature dependence and the polarization dependence of the arrayed waveguide grating optical multiplexer/demultiplexer at the same time.

Waveguide type optical device

An optical wavelength multiplexing/de-multiplexing circuit having a low loss and a flat transmission spectrum is provided. The optical wavelength multiplexing/de-multiplexing circuit compensates a temperature dependence of a center transmission wavelength which remains in an athermal AWG, and has an excellent accuracy of the center transmission wavelength in a whole operating temperature range or has a comparatively wide operable temperature range. The temperature dependence of the transmission wavelength in the athermal MZI is modulated and set so as to cancel the temperature dependence of the center wavelength which remains in the athermal AWG. The present invention focuses particularly on an optical coupler in the MZI and modulates the temperature dependence of the transmission wavelength in the MZI by providing the optical coupler itself with a mechanism which changes a phase difference between two outputs by temperature.

Optical wavelength multiplexing/ de-multiplexing circuit

In an optical interferometer, polarization dependence attributable to the optical path difference has conventionally been eliminated by inserting a half-wave plate at the center of the interferometer. However, light induced by polarization coupling produced in directional couplers used in the optical interferometer causes interference having different interference conditions from those of the normal light. Polarization rotators that effect any one of 90&#xb0; rotation and &#x2212;90&#xb0; rotation of all states of polarization of incoming light are inserted in the optical interferometer, and thereby the interference conditions of light induced by polarization coupling are made the same as those of the normal light. Each of the polarization rotators is implemented by using two half-wave plates and by varying an angle of combination of these half-wave plates. Alternatively, each of the polarization rotators is implemented through a combination of one half-wave plate and a waveguide having birefringence properties.

Waveguide-type optical interferometer

A demodulator is provided for a multilevel differential phase shift keyed signal, capable of eliminating polarization dependence due to birefringence and polarization coupling-induced light resulting from a waveguide structure, and also, polarization dependence due to dynamic birefringence produced at the time of driving a variable phase adjuster. The demodulator is configured of an optical delay line interferometer of a waveguide interference type. The S/N ratio of a demodulated signal in the demodulator formed by the optical delay line interferometer can be also improved. Further, both the polarization dependence and the temperature dependence of the optical delay line interferometer can be reduced. The disposition of a polarization converter and groves filled with a temperature compensation material makes it possible to provide a circuit configuration suitable for eliminating the polarization dependence and the temperature dependence of the optical delay line interferometer.

Optical delay line interferometer

The present invention relates to an automatic dispersion compensating optical link system. Carrier suppressed RZ encoded optical signals generated using carrier suppressing means and binary NRZ code or partial response code, or carrier suppressed clock signals generated using carrier suppressing means and clock signals are transmitted on an optical transmission line. Two bands of the carrier suppressed RZ encoded optical signals or carrier suppressed clock signals transmitted on the optical transmission line are each divided into bands and are received. Phase information of the respective basebands is extracted from the binary NRZ code components or partial response code components or clock signals in each band and the relative phase difference thereof is detected. The chromatic dispersion value of the optical transmission line is then calculated from the relative phase difference.

High precision chromatic dispersion measuring method and automatic dispersion compensating optical link system that uses this method

A Y branch circuit according to the present invention includes; a under clad; a circuit core, formed on the under clad and having a main core and two branch cores, connected to the main core, and an over clad that embeds the circuit core. The main core and the two branch cores are connected across an interval. The two branch cores have a width-to-height ratio of 50% to 150% and have a gap, at the main core end, that is narrower at the over clad side than at the under clad side.

Y branch circuit and method for manufacturing the same

An arrayed waveguide grating type optical multiplexer/demultiplexer circuit in which wavelength dispersion is reduced. An input wave guide (), a first slab waveguide (), an arrayed waveguide (), a second slab waveguide () and an output waveguide () are connected sequentially. Furthermore, a parabola waveguide () is provided between the input waveguide () and the first slab waveguide (), and a taper waveguide () is provided between the second slab waveguide () and the output waveguide (). A parabola waveguide length Zexists in a range Z=Z=Zdetermined by a parabola waveguide length Zwhere the ratio of absolute amplitude between the main peak and the first side peak in the field distribution of far-field of the parabola waveguide () has an upper limit of 0.217, and a parabola waveguide length Zwhere the relative phase of the main peak and the first side peak in the field distribution of far-field has a lower limit of 3.14 radian.

Arrayed waveguide grating type optical multiplexer/demultiplexer circuit

A planar lightwave circuit type variable optical attenuator with a small polarization dependent loss is provided. By setting the waveguide birefringence (absolute value) in first and second optical coupler sections equal to or greater than 3.5&#xd7;10, the polarization mode coupling is made equal to or less than &#x2212;25 dB, and the effect of the polarization dependence caused by the polarization mode coupling at the cross port of the first and second optical couplers is suppressed. In addition to or independently of this, the arm waveguide length can be designed to be equal to an integer multiple of the optical beat length obtained by dividing a used optical wavelength by the waveguide birefringence.

Planar lightwave circuit type variable optical attenuator

Disclosed is a wavelength multi/demultiplexer for separating two wavelength bands with a narrow wavelength spacing. A dielectric multilayer filter is provided in an intersection portion where two optical waveguides intersect each other and separates incident light to the dielectric multilayer filter to transmitted light and reflected light. Here, the distance X from the multilayer surface on the light-incident side of the dielectric multilayer to the central intersection point of the two intersecting optical waveguides is arranged to satisfy 0&#x2266;X&#x2266;d/2 (where 'd' represents the thickness of the dielectric multilayer). With this configuration, a multi/demultiplexer can be realized that shows good wavelength response without spectral degradation even for two wavelengths having narrow wavelength spacing.

Wavelength multi/demultiplexer

An optical waveguide circuit includes a first loss component for causing a diffraction loss of light propagating through an optical waveguide, and a second loss component provided at least one of before and after the first loss component, for causing a diffraction loss less than the diffraction loss in the first loss component to the light propagating through the optical waveguide. This enables the beam spot size of the lightwave launched into the first loss component to be magnified seemingly, and to reduce the radiation angle of the lightwave at the first loss component, thereby making it possible to reduce the excess loss involved in the propagation of the light through the optical waveguide.

Optical waveguide circuit

An optical multi/demultiplexing circuit includes at least one phase generating optical coupler and an optical delay line coupled to the phase generating optical coupler. The phase generating optical coupler consists of at least one input and at least two outputs. At least one of the phase generating optical coupler has a wavelength dependent or frequency dependent output phase difference in the passband of the circuit so that it can change the transmittance characteristics of the optical multi/demultiplexing circuit.

Optical multi/demultiplexing circuit equipped with phase generating device

A planar lightwave circuit is provided. The planar lightwave circuit includes a waveguide and a spotsize converter which is a part of the waveguide, wherein a core is embedded in a cladding in the waveguide, and the spotsize converter is located near an end face of a substrate on which the planar lightwave circuit is formed, the spotsize converter including: a core width fine-tuning part in an end face side of the substrate; and a core width converting part which follows the core width fine-tuning part; wherein core width of the spotsize converter is minimum at an end face of the substrate, a mean taper angle &#x3b8;of the core width fine-tuning part is larger than 0&#xb0; and smaller than a mean taper angle &#x3b8;of the core width converting part.

Planar lightwave circuit and optical circuit

An object of this invention is to cancel a polarization dependence of a transmission center wavelength due to the waveguide birefringence in an array waveguide and a slab waveguide in an array waveguide diffraction grating type optical multiplexer/demultiplexer filter applied for optical communication, particularly, wavelength split multiplexing system. In order to achieve the object of this invention, a polarization mode convertor converts the TE mode in a waveguide to the TM mode and the TM mode to the TE mode. This conversion function makes it possible to cancel the polarization dependence of the transmission center wavelength due to the waveguide birefringence in the array waveguide and the slab waveguide in front of and behind the polarization mode convertor.

Array waveguide diffraction grating type optical multiplexer/demultiplexer

An interferometer includes a waveguide core, and thin film heaters with widths W and W . The thin film heaters are mounted directly above the waveguide core, and operate as two types of different annealing regions. The annealing, which is carried out by supplying current to the thin film heaters, can alter the quality of the cladding, and change the stress applied on the waveguide core, thereby making it possible to control the polarization dependency. Thus changing the width of the thin film heaters and/or the amount of the supply current thereto enables the permanent control of the effective refractive index (birefringence index) independently in the transverse electric polarization mode and the transverse magnetic polarization mode. This enables the transverse electric polarization mode to be adjusted to a phase difference of &lgr;/2, and the transverse magnetic polarization mode to a phase difference of zero.

Interferometer and its fabrication method

Growing community of inventors

Atsugi, Japan

Yasuyuki Inoue