Nippon Telegraph and Telephone Corporation

Other

Ntt Electronics Corporation

Yasuaki Hashizume

Yasuyuki Inoue

Josuke Ozaki

Yoshihiro Ogiso

Takashi Saida

Manabu Oguma

Akio Sugita

Hiroshi Takahashi

Masahiro Yanagisawa

Toshikazu Hashimoto

Takayuki Mizuno

Yusuke Nasu

Takashi Goh

Hiromasa Tanobe

Shunichi Soma

Yohei Sakamaki

Yasuhiro Hida

Masayuki Okuno

Yoshinori Hibino

Mitsuru Nagano

Kuninori Hattori

Nobuhiro Nunoya

Mitsuteru Ishikawa

Takanori Ishikawa

Atsushi Murasawa

Masaki Kotoku

A semiconductor Mach-Zehnder optical modulator includes input-side lead-out lines, phase modulation electrode lines, and electrodes that apply modulation signals propagating through the phase modulation electrode lines to waveguides, respectively. The semiconductor Mach-Zehnder optical modulator further includes a conductive layer between a substrate and the waveguides, a plurality of first wiring layers connected to the conductive layer, and a second wiring layer that connects an electrode pad and the plurality of first wiring layers.

Semiconductor Mach-Zehnder optical modulator and IQ modulator

Provided is an IQ optical modulator including a nest-type MZ optical waveguide having optical modulation regions of I channel and Q channel End portions of an input optical waveguide and an output optical waveguide of the IQ optical modulator are located on a same edge face of a chip of the IQ optical modulator, an optical cross waveguide is included in which an optical waveguide between a first optical combiner and a second optical combiner of the nest-type MZ optical waveguide and the input optical waveguide cross each other, a first optical divider is provided between the I-channel optical modulation region and the Q-channel optical modulation region, and a light propagation direction in the first optical divider and a light propagation direction in the optical modulation regions are opposite to each other.

IQ optical modulator

In the adjustment method of optical coupling for an optical integrated circuit according to the present disclosure, the optimal adjustment position of optical coupling is determined on the basis of, for example, a sum of a plurality of photocurrents at electrodes on arm waveguides respectively formed on the plurality of MZIs in the polarization-multiplexing IQ modulator. According to the maximum value of the sum of the plurality of photocurrents, the light condensing spot position is adjusted to the center position of the end face core of the optical waveguide of the integrated chip. Typically, the light condensing spot position is adjusted to the center of the end face core by displacing the two input lenses.

Optical coupling method

Excess optical power in a waveguide device is appropriately terminated. According to one embodiment of the present invention, the waveguide device comprises a termination structure filled with a light blocking material for terminating light from the end section of a waveguide. This termination structure can be formed by forming a groove on an optical waveguide by removing the clad and core, and filling the inside of that groove with a material attenuating the intensity of the light (light blocking material). In this manner, light that enters into the termination structure is attenuated by the light blocking material, and influence on other optical devices as a crosstalk component can be suppressed. With such termination structure, not only the influence on optical devices integrated on the same substrate, but also the influence on other optical devices directly connected to that substrate can be suppressed.

Waveguide device and module

A Mach-Zehnder interferometer circuit () is provided with two couplers () and two arm waveguides () connecting the couplers with each other, each fabricated on a substrate, in which a polarization rotation device () is disposed in a groove dividing each of the two arm waveguides into two, the polarization rotation device () for converting vertically polarized light into horizontally polarized light, and birefringence is adjusted by performing laser irradiation or the like partially into at least one of the two arm waveguides such that a difference between birefringence values divided by an optical wavelength to be used is within a range of 2 m-0.2 to 2 m+0.2 (m is an integer including zero), the birefringence values being those integrated linearly along the respective two arm waveguides in an optical signal travelling direction.

Polarization-independent waveguide-type optical interference 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 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

A low-cost, high-reliability polarization-independent optical waveguide interferometer is proposed which does not bring about any additional job involved in the insertion of a half-wave plate or excess loss of light. In an optical multi/demultiplexer utilizing optical interference of light waves passing through a plurality of optical waveguides with different lengths, such as an AWG and a Mach-Zehnder interferometer, longitudinal integral values of birefringence values of the individual waveguides, which values are variable or invariable along the waveguides, are made equal for all waveguides 201 and 202. Thus, simply varying the waveguide width can implement polarization-independent operation, or on the contrary implement a polarization beam splitter. For example, the polarization-independent can be implemented by making the core widths, which are averaged in a longitudinal direction of a plurality of optical waveguides with different lengths, wider in a shorter optical waveguide, and narrower in a longer optical waveguide.

Polarization desensitized optical waveguide interferometer

Growing community of inventors

Atsugi, Japan

Yasuaki Hashizume