Nec Corporation

Other

Yukinobu Nakabayashi

Jungo Kondo

Minoru Imaeda

Tatsuo Kawaguchi

Jun Yokoyama

Mitsuhiro Kitamura

There is provided an optical matrix switch which comprises a branch-selective network and has, in its center stage, a transmittance-variable optical switch (a gate) with one input and one output. Varying the transmittance of the gate can reduce crosstalk between channels, and, if necessary, can control the power of optical channels. An optical ADM is also provided. In this optical ADM, a first level controller is provided between first and second optical switches for drop and add and controls the level of transmitted light, the level of an optical signal dropped is controlled in a second level controller, and the level of an optical signal added is controlled in a third level controller. The individual members are provided in an integral form on a single substrate. This can realize a reduction in size and a reduction in weight of an optical ADM. Further, this facilitates the control of a variation in loss in each path and the control of the level of optical signals in a terminal for drop and a terminal for add.

Matrix optical switch and optical ADM

A process for producing an optical waveguide element by thermally diffusing a metal element or a metallic compound into a substrate having a photoelectric effect, includes the steps of: forming a waveguide pattern on the substrate, the waveguide pattern includes a metal element or metallic compound; forming a film on a main plane of the substrate that covers the entire waveguide pattern, the film having an electro-optic effect; and effecting the thermal diffusion of the metallic element or the metallic compound.

Optical waveguide elements and a process for producing the same

An optical circuit include a plurality of optical wave guides each having an electro-optic crystal such as LiNbO,or LiTaO,and a domain orientation different from the other waveguide. More specifically, in accordance with the invention, a portion of the circuit is inverted with respect to a domain. For instance, in an optical wave guide having a domain-inverted portion, if electric fields having the same orientation are applied to a plurality of portions which vary an index of refraction thereof, indexes of refraction are caused to vary in opposite polarities. Hence, it is possible to lower a voltage at which an optical device operates. If the present invention is applied to a Mach-Zehnder type phase shifter, it would be possible to accomplish push-pull operation, only if an electric field has one orientation. The invention further lower a voltage at which the phase shifter operates through a difference in an index of refraction between two optical wave guides.

Optical circuit and method of fabricating the same

A rare earth-doped optical fiber is supplied with a input signal light and an excitation light, so that the input signal light is amplified to be supplied to an output as an amplified signal light. At this time, an intensity of an amplification of spontaneous emission (ASE) is detected to be compared with a predetermined intensity, thereby to provide a difference signal. An amount of the excitation light is controlled by the difference signal to equalize the ASE to the predetermined intensity.

Optical fiber amplifier and optical transmission system using the same

An optical fiber amplifier includes an optical amplifying section having an Er-doped fiber. A gain equalizing section is provided at secondary stage of the optical amplifying section and has an optical filter unit for compensating for wavelength dependency characteristics of a signal gain at the optical amplifying section. The gain equalizing section has a filter rotating device and the optical filter unit has et least two optical filters of transparent multi-layer film in which a layer of high refractive index and a layer of low refractive index are alternately and repeatedly stacked. The optical filter is rotated by the filter rotating device such that the wavelength transmission characteristics of the optical filter are set by changing an angle of incidence of the signal light with respect to the optical filter and the wavelength dependency characteristics of the signal gain are compensated for. The optical filter which is of the multi-layer film and which is rotatably arranged improves wavelength tunability.

Growing community of inventors

Tokyo, Japan

Yukinobu Nakabayashi