Fujitsu Corporation

Fujitsu Optical Components Limited

Hirotomo Izumi

Nobuaki Mitamura

Hiroshi Nagaeda

Yuichi Kawahata

Takashi Ishiwada

Nobuhiro Fukushima

Setsuo Yoshida

Kazumasa Takabayashi

Suguru Akiyama

Manabu Yamazaki

Shigeki Kawaai

Yukie Iga

Yasuhiro Hirose

A wavelength filter includes a first filter circuit and a second filter circuit. The first filter circuit that has a passband that is obtained from a vernier effect by connecting, in series, a plurality of ring resonators each having a different transmission wavelength interval and that is within a gain band of an optical amplifier, and that passes, from the gain band, light at a selected wavelength and light that has a wavelength in a recursive mode and that is produced on a short wavelength side or a long wavelength side of the selected wavelength. The second filter circuit is connected to the first filter circuit in series and suppresses the light at the wavelength in the recursive mode from the light passing through the first filter circuit.

Wavelength filter and laser apparatus

A Mach-Zehnder optical modulator includes: a Mach-Zehnder interferometer that includes first and second arms formed on a silicon substrate, and a controller that controls bias current of the first and second arms. The controller controls the bias current of the first and second arms respectively to be a first offset value. The controller repeatedly executes a current adjustment process to increase the bias current of the first arm until a gradient of a phase shift amount of the first arm with respect to the bias current of the first arm reaches a target value. The controller controls the bias current of the second arm to be a second offset value that is smaller than the first offset value. The controller repeatedly performs the current adjustment process to increase the bias current of the first arm until a phase difference of the Mach-Zehnder interferometer reaches a target phase difference.

Mach-zehnder optical modulator

A chromatic dispersion compensator whereby the amount of dispersion and the group delay time can be easily adjusted. A dispersion unit, a transmitting lens and a group delay generation unit are arranged along the optical axis of incident light. The dispersion unit separates the incident light into beams of respective different wavelengths. The transmitting lens is arranged across the optical paths of the beams of different wavelengths separated by the dispersion unit, and refracts the beams at different angles according to their respective incidence positions. The group delay generation unit is arranged across the optical paths of the beams of different wavelengths refracted by the transmitting lens, causes the beams to undergo propagation delay for periods corresponding to their respective incidence positions, and converges and emits the beams of different wavelengths. Consequently, the beams of different wavelengths are imparted group delay corresponding to the refracting angles of the transmitting lens.

Chromatic dispersion compensation device and method

A spectroscopic apparatus which is compact in size and performs high-precision light-splitting with a large angular dispersion. An optical input-processing section outputs a filtered transmitted light, using a bandpass filter that transmits only wavelength bands at one period of an input light, and collects the filtered transmitted light to generate a collected beam. An optic includes a first reflection surface and a second reflection surface which are high but asymmetric in reflectivity, and causes the collected beam incident thereon to undergo multiple reflections within an inner region between the first reflection surface and the second reflection surface, to thereby cause split beams to be emitted via the second reflection surface. A received light-processing section performs received light processing of the beams emitted from the optic. A control section variably controls at least one of a filter characteristic of the bandpass filter and an optical length through the optic.

Spectroscopic apparatus

The present invention has an object to provide an optical apparatus of VIPA-type for achieving the reduction of the inter-channel loss deviation to realize a high accurate demultiplexing function. To this end, the optical apparatus according to the present invention comprises: a collimator lens converting an input light into a parallel light; a phase mask changing a phase of the parallel light from the collimator lens to change the intensity distribution into a shape different from the Gaussian distribution; a line focal lens condensing the light output from the phase mask onto a one-dimensional direction; and a VIPA plate multi-reflecting the light condensed by the line focal lens to emit the multi-reflected light.

Optical apparatus provided with demultiplexing function

An object of the invention is to easily realize an optical element using an etalon type structure, capable of changing a periodic transmission wavelength characteristic in an axial direction of transmissivity, and also capable of changing a periodic characteristic with respect to wavelength. To this end, a transmission wavelength characteristics variable optical element according to the invention comprises: a light interference section including a pair of wedge shape magneto-optic crystals arranged with taper faces thereof in close contact, that can change a distance between reflecting films formed on parallel planes of the magneto-optic crystals, by relatively moving the magneto-optic crystals by movable sections, permanent magnets for applying a fixed magnet field to the pair of magneto-optic crystals, an electromagnet for applying a variable magnetic field in a direction different to the fixed magnetic field, and a variable current source controlling the current flowing into the electromagnet.

Transmission wavelength characteristics variable optical element, and wavelength characteristics variable apparatus, optical amplifier, and optical transmission system, using same

A VIPA plate having a configuration where a translucent reflection film and a total reflection film are respectively arranged on one side and the other side of a transparent parallel plate can be used as a wavelength dispersion compensator by using a special mirror and a lens. However, the transparency characteristic of the wavelength dispersion compensator using such a VIPA plate is a periodical characteristic which is asymmetric with a central wavelength in a wavelength regime. Accordingly, not parallel light but converged or diverged light having angular dispersion is input to an etalon plate, so that a filter whose transparency characteristic is an asymmetric periodical characteristic which is reverse to the VIPA plate is configured for the central wavelength in the wavelength regime. With this filter, the transparency characteristic of the wavelength dispersion compensator using the VIPA plate is optimized.

Optical apparatus and device

The present invention aims at providing a transmission wavelength characteristics variable optical element which can actively equalize changes of the wavelength characteristics due to temperature changes, and providing a wavelength characteristics variable apparatus, an optical amplifier, an optical transmission system, and a control method of the transmission wavelength characteristics, which use such an optical element. To this end, the transmission wavelength characteristics variable optical element according to the present invention comprises: an light interference section in which for example reflection films are formed on a light incident plane and a light emitting plane of a magneto-optic crystal; a permanent magnet that applies a fixed magnetic field to the magneto-optic crystal; an electromagnet that applies a variable magnetic field in a direction different from that of the fixed magnetic field; and a variable current source that controls the current flowing in the electromagnet, and varies transmission wavelength characteristics which occur due to an interference of light multireflected between the reflection films, by changing a Faraday rotation angle given to the light being propagated within the magneto-optic crystal, corresponding to a synthetic magnetic field formed by the fixed magnetic field and the variable magnetic field.

TRANSMISSION WAVELENGTH CHARACTERISTICS VARIABLE OPTICAL ELEMENT, AND WAVELENGTH CHARACTERISTICS VARIABLE APPARATUS, OPTICAL AMPLIFIER, OPTICAL TRANSMISSION SYSTEM, AND CONTROL METHOD OF TRANSMISSION WAVELENGTH CHARACTERISTICS, USING SAME

By connecting a plurality of VIPA type wavelength dispersion compensators, each compensating for wavelength dispersion of a different order by a plurality of optical circulators and sequentially inputting input light to each VIPA type wavelength dispersion compensator, light, even the higher-order wavelength dispersion of which is compensated for, is outputted as output light.

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Kawasaki, Japan

Hirotomo Izumi