Fujitsu Corporation

Toshihiro Otani

Yoshinobu Kubota

Yasuhiro Omori

Tomoyuki Itoh

Hironao Hakogi

Hisashi Takamatsu

Eiji Ishikawa

Shinya Sawae

Tomoyuki Ito

Junko Watanabe

Tomoyuki Itou

Akiko Tanno

An optical transmission system wherein a main signal light is amplified by Raman amplification, and noise light (ASS light) produced by the Raman amplification can be corrected with a simple configuration and with high accuracy. The optical transmission system includes, in each transmission section: a cutoff section for transmitting/cutting off a main signal light outputted from the optical transmitter on the preceding stage and inputted into the Raman amplification medium on an optical transmission line; a control section for varying the power of the pumping light supplied to the Raman amplification medium and changing the state of the cutoff section depending on the variation of the pumping light power; a monitor section for measuring the power of the pumping light supplied to the Raman amplification medium and the power of the light propagated through the optical transmission line and inputted into an optical transmitter on the succeeding stage; and a processing section for separately detecting the power of the main signal light and the power of the ASS light on the basis of the results of the measurement by the monitor section, and correcting the ASS light.

Optical transmission system having function of correcting noise light due to Raman amplification

An optical modulator for modulating light emitted from a signal light source has a substrate having electrooptic effect, an optical waveguide of a Mach-Zehnder type formed on the substrate, an electrode formed on the substrate to control light propagated in the optical waveguide, an interference light generating means for making radiation light radiated from the optical waveguide and signal light leaking from the optical waveguide interfere with each other to generate interference light, and emitting the interference light from an end surface of the substrate, a photo-detector for monitoring the interference light of the radiation light and the signal light, and a signal controlling circuit for controlling an operating point of the optical modulator according to a change of the interference light monitored by the photo-detector It is thereby possible to prevent degradation of a distinction ratio due to a shift of the operating point of the optical modulator so as to allow stable optical modulation, while facilitating a design of the mechanism of the optical modulator.

Optical modulator

An optical modulator for modulating light emitted from a signal light source has a substrate having electrooptic effect, an optical waveguide of a Mach-Zehnder type formed on the substrate, an electrode formed on the substrate to control light propagated in the optical waveguide, a light guiding unit for guiding light radiated or leaking from the optical waveguide, an interference light generating means for making light emitted from the light guiding unit and signal light leaking from the optical waveguide interfere with each other to generate interference light, and for emitting the interference light from an end surface of the substrate, a photo-detector for monitoring the interference light obtained by the interference light generating means, and a signal controlling circuit for controlling an operating point of the optical modulator according to a change of the interference light monitored by the photo-detector, thereby stably controlling the operating point of the optical modulator while facilitating a design of the mechanism.

An optical waveguide device including a package housing having an element mounting surface, an element inserting groove opening to the element mounting surface, and a cutout as a space opening to an inner surface of the element inserting groove; and an optical waveguide element having a dielectric substrate, an optical waveguide formed in a surface of the dielectric substrate, and an electrode formed over the surface of the dielectric substrate, the optical waveguide element being inserted and fixed in the element inserting groove of the package housing by using an adhesive. The cutout opens also to the element mounting surface. In applying the adhesive to the bottom surface of the element inserting groove and inserting the optical waveguide element into the element inserting groove, the adhesive flows into the cutout and is prevented from flowing up to the element mounting surface. Further, a working space for application of the adhesive to the bottom surface of the element inserting groove can be ensured by the cutout.

Optical waveguide device

A crystal substrate, with an adhesive uniformly applied to its entire rear surface, is fixed to the inner wall of an element housing. By adjusting the thickness of a wall of the element housing, forming grooves in the wall, or fixedly attaching a deadweight to the wall, the resonant frequency of the element housing is adjusted so as to restrain the optical waveguide element from resonating. Further, by mounting the optical waveguide device on a printed board via an elastic member or the like, propagation of the vibration to it is suppressed.

Optical waveguide device and optical waveguide apparatus

Disclosed herein is an optical modulator module including an optical waveguide structure of a Mach-Zehnder type, for example, an electrode for switching a coupling mode where an output beam is obtained from the optical waveguide structure and a leakage mode where a leakage beam deflects from the optical waveguide structure, a photodetector having a photodetecting surface for receiving the leakage beam, and a mechanism for converting a beam parameter of the leakage beam so as to prevent close contact of the photodetecting surface with the optical waveguide structure. The optical modulator module allows monitoring of optical power by the use of the leakage beam and is improved in manufacturability.

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Sapporo, Japan

Toshihiro Otani