Sumitomo Osaka Cement Co., Ltd.

Nec Corporation

National Institute of Information and Communications Technology, Incorporated

Other

University of California

National Institute for Materials Science

National Institute of Information and Communications Technology, Incorporated Administrative Agency

Communications Research Laboratory, Independent Administrative Institution

National Institute of Information and Communication

Kaoru Higuma

Junichiro Ichikawa

Shingo Mori

Tetsuya Kawanishi

Norikazu Miyazaki

Takaaki Ogata

Hirotoshi Nagata

Yasuhisa Taneda

Yoshihiro Hashimoto

Masayuki Izutsu

Toshio Sakane

Satoshi Oikawa

Toshio Kataoka

Masahito Mure

Masahiro Tsuchiya

Kenji Kitamura

Yoichi Oikawa

Sunao Kurimura

Hiroshi Nagaeda

Yozo Shoji

Hiroyo Ogawa

Futoshi Yamamoto

Youichi Hosokawa

Takahisa Fujita

Atsushi Kanno

Noriyasu Shiga

Paul Kit Lai Yu

Junichiro Minowa

Masahide Miyachi

Hiroyuki Sato

Jianxiao Chen

The optical modulator includes optical modulation units. The plurality of optical modulation units is disposed in parallel on the same substrate. One input waveguide branches off to be connected to the Mach-Zehnder type optical waveguide of each optical modulation unit, and an entire optical waveguide is formed such that outputs from the Mach-Zehnder type optical waveguides are combined and output through one output waveguide. A modulation signal with the same intensity is applied to a modulation electrode of each optical modulation unit. In at least some of the optical modulation units, mechanical structures including the modulation electrodes of the optical modulation units are configured such that an amplitude value of an optical output modulated by the modulation signal of the optical modulation unit is &#xbd;(n is a natural number) of a maximum amplitude value in other optical modulation units.

Optical modulator

Provided is an optical receiver which accurately demodulates an optical signal obtained by the differential phase shift modulation method. The optical receiver includes: an interferometer which branches the inputted optical signal into two parts and gives a one-bit phase difference to the resultant two optical signals so that the two optical signals after addition of the phase difference are made to interfere each other to output two output lights; reflection means which reflects one of the output lights from the interferometer so as to return to the interferometer; detection means which detects the return light which has been reflected by the reflection means and propagates through the interferometer in the different direction from the inputted optical signal, for output; and phase difference control means which adjusts the phase difference given by the interferometer according to the intensity of the return light detected by the detection means.

Optical receiver

The present invention relates to an optical receiver, and particularly, to an optical receiver by which a DQPSK-modulated optical signal is demodulated to a multilevel phase-modulated signal.

A method and device for adequately controlling the DC bias of each of the optical modulating sections of an optical modulator even while the optical modulator is operating in normal mode and even with a simple structure. An optical modulator bias controller (B) for controlling the DC bias of each optical modulating section of an optical modulator () is characterized by comprising DC bias application means () for applying a DC bias to each of the optical modulating sections, a low-frequency signal superimposing circuit () for superimposing a low-frequency signal fwith a specific frequency on a modulating signal b applied to each optical modulating section, optical sensing means () for sensing a change of the intensity of the light wave passing through the combining section, and bias control means () for extracting the change of the intensity of light corresponding to the low-frequency signal from the optical sensing means and controlling the DC bias application means according to the extracted change of the intensity of light.

Method and device for controlling bias of optical modulator

A method for generating a carrier residual signal and its device, in which a heterodyne optical signal used in a photometric field or an optical fiber radio communication field can be stably generated with a simplified structure. The device includes an optical modulating unit that includes a light source generating a light wave having a specific wavelength, and an SSB optical modulator. A light wave emitted from the light source enters into the optical modulating unit. A light wave emitted from the optical modulating unit includes a carrier component related to a zero-order Bessel function and a specific signal component related to a specific high-order Bessel function while suppressing signal components other than the specific signal component related to the specific high-order Bessel function, and a ratio of optical intensity between the carrier component and the specific signal component is set substantially to 1.

Method for generating carrier residual signal and its device

Light having components of frequencies f, fand foutputted from an optical modulator () is monitored, a second light detection means () measures the power Pof all the components, and a first light detection means () measures the power Pwith frequency fcomponent cut out by a filter means (). Based on these light receiving powers (P) and (P), phase differences imparted by the respective DC electrodes of Mach-Zehnder optical waveguides (MZ-A, MZ-B, MZ-C) of the optical modulator () are controlled. The control is performed to minimize the light receiving power (P) and to maximize the light receiving power (P).

Optical modulation device

The present invention purposes to provide a THz-wave generator capable of generating a THz-wave stably and efficiently, and particularly, to provide the THz-wave generator which is stable against a frequency shift of a laser source and which can easily vary the frequency of the THz-wave. A THz-wave generator, for inputting a laser beam from a light source unit A including a laser source to a THz-wave generating element D, and generating a THz-wave (f) from the THz-wave generating element, wherein a light circulating unit including an SSB optical modulator, and wavelength selecting means C are disposed between the laser source A and the THz-wave generating element D, the laser beam is guided into the light circulating unit, a specific wavelength lightwave is selected out of lightwaves having a plurality of wavelengths generated in the light circulating unit by the wavelength selecting means, and the specific wavelength (f, f) lightwave is input to the THz-wave generating element.

THZ wave generator

An optical modulator is provided which includes: an optical splitting part that splits an input light wave into two light waves; two optical waveguides that propagate the two light waves into which the input light wave is split, respectively; a first SSB modulating part that is provided in one of the two optical waveguides and modulates a light wave, which propagates into the first SSB modulating part, with a carrier frequency so that the light wave is converted into a different light wave having a single side band; a second SSB modulating part that is provided in the other of the two optical waveguides and modulates a light wave, which propagates into the second SSB modulating part, with a data signal in order to generate a signal light wave having a different single side band; and an optical combining part that combines the light wave modulated by the first SSB modulating part with the signal light wave generated by the second SSB modulating part.

A nested modulator is provided where the circuit arrangement of modifying electrodes including signal electrodes is simplified, and at the same time, the drive voltage can be lowered. A nested modulator, including: a substratemade of a material having electro-optic effects; an optical waveguide formed on the substrate; and a modulating electrode for modulating light waves which are guided through the optical waveguide, wherein the optical waveguide has a main Mach-Zehnder waveguideand sub-Mach-Zehnder waveguidesandprovided on two branching waveguides of the main Mach-Zehnder waveguide, and the modulating electrode is provided in a sub-branching waveguide of the sub-Mach-Zehnder waveguides, is characterized in that a polarization reversal regionoris formed in a portion of a sub-branching waveguide of each of the sub-Mach-Zehnder waveguides, the modulating electrode is formed of signal electrodes including introduced signal electrodesor, branching single electrodesorand lead signal electrodesoras well as ground electrodes for each of sub-Mach-Zehnder waveguides, and the branching signal electrodes which branch from the introduced signal electrode are placed so as to work on two sub-branching waveguides for each of the sub-Mach-Zehnder waveguides.

Nested modulator

The invention provides tunable delay or resonator devices in an electro optical substrate. Signals in at least one waveguide in the electro optical substrate pass through Y-junction reflectors which direct signals from one branch of the waveguide back into another branch of the waveguide. A coupled delay or resonator approximated loop is presented in an embodiment of the invention with opposing Y-junction reflectors. In other embodiments of the invention, a delay ladder is provided with selectable levels of delay from multiple outputs.

Y-junction reflector tunable delay or resonator waveguide devices

An optical modulator which magnifies a modulation index and reduces affection of SBS by suppressing a light source carrier component in an equivalent light source spectral width and performs more long-distance transmission by suppressing one of sideband spectrums generated by a modulation signal to reduce affection of fiber dispersion, having a light branch means that branches input light having a carrier component into two light waves; a SSB modulation means that modulates one branched wave and generates a wave having the carrier component and one sideband spectrum; an intensity adjustment means that adjusts intensity of the carrier component of the other wave; a phase adjustment means that adjusts the phase of the carrier component with respect to at least one of the two waves; and a multiplexing means that multiplexes the two waves passing through the modulation means, and the intensity and phase adjustment means, and emits output light.

An optical SSB modulator capable of appropriately adjusting a phase difference of light in the MZ waveguides and automatically adjusting a voltage impressed to the bias adjustment electrodes is provided. The above-mentioned object is achieved by an optical SSB modulator () provided with a first sub Mach-Zehnder waveguide (MZ) (), a second sub Mach-Zehnder waveguide (MZ) (), a main Mach-Zehnder waveguide (MZ) (), a first bias adjustment electrode (DCelectrode) (), a second bias adjustment electrode (DCelectrode) (), a first modulation electrode (RFelectrode) (), a second modulation electrode (RFelectrode) () and a third bias adjustment electrode (DCelectrode) (), wherein either one of or both of output portions () of the MZand the MZhave an X-branching form, and specifically having one of light paths of the X-branching connected to a photodetector.

Optical SSB modulator

An optical modulation apparatus includes an optical signal input section, an optical signal propagation path, an optical modulator that modulates the phase of optical signals in at least two of a plurality of optical paths, and a wavelength selective filter that selectively reflects and transmits. Optical signals input via the input section are divided into a plurality of optical paths at a branching point and phase modulated by the phase modulator, that divides the optical path into a plurality of optical paths. Light transmitted by the filter is output via the output section, while light reflected by the filter travels back along the optical path and is again phase modulated by the phase modulator combined at the branching point and output from the input section as an intensity modulated optical signal.

Optical modulator and optical signal and electric wave signal converter using same

The object of the present invention is to provide a light limiter which can control the generation of an optical surge, comprises few components, and has high reliability; in order to achieve the object, the light limiter of the present invention comprise a parametric amplification element parametrically amplifying an input signal light, and a wavelength selection element removing a wavelength component, excepting a specified wavelength, from among the signal light output from said parametric amplification element.

Growing community of inventors

Tokyo, Japan

Kaoru Higuma