Nippon Telegraph and Telephone Corporation

Yoshitada Katagiri

Wataru Imajuku

Etsu Hashimoto

Kenichi Suzuki

Atsushi Nakamura

Junichi Shimada

Akinori Watabe

Shinji Nagaoka

Hidenao Tanaka

Fumikazu Ohira

Hiroshi Abe

Yoshio Suzuki

Masamichi Fujiwara

Kazuo Aida

Noboru Takachio

Shingo Kawai

Kunihiko Mori

Ken-Ichi Suzuki

Renshi Sawada

Tomoyuki Toshima

Hitoshi Obara

Yoshiaki Tachikawa

Ken-ichi Suzuki

Yoshihiro Isomura

Hiroo Ukita

Yuuji Uenishi

Keisuke Mise

Tetsuo Abe

Extremely advanced technology for scrambling an optical signal based on quantum mechanical fluctuation is used to provide a highly reliable optical communication method which can invalidate illicit activities such as wire-tapping, a system, and a laser oscillator which is used in the method and system. A transmitter side generates laser light, simultaneously oscillated at a plurality of wavelengths, the total number of generated photons being constant, and transmits a signal light comprising data which has been added to the light of the plurality of wavelengths; and at a receiving side, light, simultaneously oscillated at the plurality of wavelengths, is selected from the signal light, and the data is demodulated.

Laser oscillator, optical communication method and system

Optical wavelength control method and apparatus which are capable of controlling an optical wavelength of a light source with a central wavelength which is uncertain and unstable at nanometer order is disclosed. In the optical wavelength control apparatus, the control target light entered from the variable wavelength light source is scanned at a prescribed period and optical pulses having a phase corresponding to the optical wavelength of the control target light are obtained. Then, a phase difference between a phase of the optical pulses and a phase corresponding to a reference optical wavelength is detected, and the variable wavelength light source is controlled by feeding back the phase difference to the variable wavelength light source such that the optical wavelength of the control target light is controlled by an optical frequency pulling with respect to the reference optical wavelength according to the phase difference.

Method and system for controlling optical wavelength based on optical frequency pulling

Method and apparatus for controlling optical wavelength based on optical frequency pulling

A temperature meter for measuring temperature of a measurement target object to which a temperature sensor cannot be fixed directly is formed by a temperature sensor configured to measure an observed temperature in a vicinity of the measurement target object; a timer configured to measure a temperature observation time; and a calculation processor configured to calculate the temperature of the measurement target object according to the observed temperature and the temperature observation time by carrying out a prescribed calculation processing.

Method and apparatus for measuring temperature of movable object

A method for manufacturing an optical filter capable of manufacturing an optical filter in such a manner that the transmission wavelength varies linearly with respect to the angle &thgr; in the rotation direction of the substrate and that almost the entire range of the angle &thgr; is utilizable as the optical filter. A mask capable of being rotated relatively with respect to the substrate coaxially on a plane parallel to the substrate, which is either having an aperture extending along a radius direction with an aperture angle &phgr; or itself extending along a radius direction to cover an angle &phgr;, is provided over the substrate. Then, the mask is relatively rotated with respect to the substrate at least once at a non-constant angular speed during a formation of a single layer or multiple layers on the substrate, while depositing a dielectric material in a single layer or multiple layers on the substrate from the mask side within a deposition chamber.

Method for manufacturing optical filter

The present invention provides a light generation method and a light source that are preferable in obtaining a single-mode light having high outputs, a small wavelength spectral bandwidth, and a low intensity noise. A white output from a white-light source and having wavelength components over a wide-band in a wavelength spectrum passes through an isolator and is then filtered by a disc-shaped optical filter. A transmitted light is input to a semiconductor optical amplifier having its polarization plane regulated by a polarization controller. An output from the amplifier passes through an isolator and is then filtered by a disc-shaped optical filter again to generate a single-mode light having a small spectral bandwidth and high outputs. Polarization control by the polarization controller corresponds to control of the polarization plane of a semiconductor laser in the semiconductor optical amplifier so as to obtain a maximum gain from the amplifier. This configuration enables a single-mode light having a small spectral bandwidth and high outputs to be easily generated at an arbitrary wavelength.

Light generation method and light source

A disk shaped tunable optical filter is formed by a transparent substrate in a disk shape, and a filter layer formed on a top surface of the substrate, having such a filter characteristic that a transmission central wavelength varies along a circumferential direction as a monotonic function of a viewing angle. This disk shaped tunable optical filter can be advatageously utilized in realizing a wavelength discrimination apparatus, a reference wavelength light generation apparatus, an optical packet generation apparatus, and a tunable optical filter module, which are also disclosed.

Disk shaped tunable optical filter

A semiconductor laser apparatus includes a semiconductor substrate, a first cladding layer, an active layer, a second cladding layer, a second electrode, and a pair of resonator mirrors. The semiconductor substrate has a first electrode on one surface. The first cladding layer is formed on the other surface of the semiconductor substrate. The active layer is placed on the cladding layer. The second cladding layer is placed on the active layer. The second electrode is placed on the second cladding layer. The pair of resonator mirrors are placed in a waveguide direction perpendicular to the surfaces of the semiconductor substrate to oppose each other. The active layer is constituted by a quantum well layer having a tensilely strain. The second electrode is separated into portions not less than two portions.

Magneto-optic information storage system utilizing a TE/TM mode

Polarization mode switching semiconductor laser apparatus

A micro optical head, for optically reading and/or writing digital data on a recording medium in which digital data 1 and 0, corresponding to a high reflection factor and a low reflection factor, is composed of a self-coupled semiconductor laser located close to the recording medium. A bias current of the laser is determined so that it is smaller than a first threshold current, in which the medium has a low reflection factor, and is higher than a second threshold current, in which the medium has a high reflection factor. Output light of the laser is either strong stimulated emission light, corresponding to the high reflection factor, or weak spontaneous emission light, corresponding to the low reflection factor. The present head is carried on a flying slider with a spacing length less than several .mu.m which provides a small beam spot of about 1 .mu.m, and has an excellent signal to noise ratio. A photodetector for sensing the output of the laser may be carried on the same semiconductor substrate as that of the laser.

Micro optical head with an optically switched laser diode

Growing community of inventors

Tokyo, Japan

Yoshitada Katagiri