Fujitsu Corporation

Takanori Maki

Masaaki Takahashi

Kenji Ohta

Tatsuo Nagayoshi

Kazunori Hayami

Katsumi Kikawa

Kazuya Amaki

Mitsushi Nitta

Katsuhiko Suga

Koichi Kimotsuki

An optical multiplexing apparatus of a low cost is capable of reliably multiplexing a plurality of optical signals having a narrow wavelength interval, while suppressing the nonlinear optical effect and the crosstalk, and a multiplexing method. The optical multiplexing apparatus includes a first optical multiplexer for multiplexing, among a plurality of optical signals that are input with directions of linear polarization of the neighboring wavelengths being differed to each other, optical signals having odd wavelength numbers while maintaining their polarization states. A second optical multiplexer multiplexes optical signals having even wavelength numbers while maintaining their polarization states, and a third optical multiplexer multiplexes, at an output unit thereof through first and second input units having sharp filtering characteristics, the optical signals multiplexed by the first and second optical multiplexing means, to output WDM signal light.

Optical multiplexing apparatus and optical multiplexing method

The present invention is directed to the provision of a wavelength division multiplexing optical transmission apparatus and, more particularly, to a wavelength division multiplexing optical transmission apparatus having high wavelength stability unaffected by the temperature characteristics, aging, etc. of an arrayed-waveguide grating (AWG) and its peripheral components. The wavelength division multiplexing optical transmission apparatus comprises: an arrayed-waveguide gratinghaving operating input/output ports and an input dummy port; a light emitting meansfor generating a pilot signal to be input to the input dummy port; a light detecting meansfor monitoring the pilot signal contained in a wavelength division multiplexed signal output from the operating output port; and a temperature control circuitfor controlling the temperature of the arrayed-waveguide grating in such a manner as to cancel the amount of wavelength fluctuation occurring in the arrayed-waveguide grating and detected by monitoring the pilot signal.

Wavelength division multiplexing optical transmission apparatus

The invention provides a wavelength division multiplexing optical transmitter wherein an unequally spaced arrangement of optical wavelengths can be realized readily and economically. The wavelength division multiplexing optical transmitter includes an optical transmission section for outputting a plurality of optical signals having wavelengths spaced by unequal distances from each other, and a wave multiplexer having an equally spaced wavelength optical multiplexing characteristic of multiplexing a plurality of optical signals having wavelengths spaced by a substantially equal distance from each other. The wave multiplexer being constructed such that, when the plurality of optical signals are inputted thereto from the optical transmission section, the wave multiplexer multiplexes the plurality of optical signals from the optical transmission section into a multiplexed optical signal and outputs the multiplexed optical signal. Also a wavelength division multiplexing-demultiplexing optical transmission-reception system which incorporates the wavelength division multiplexing optical transmitter is disclosed.

Wavelength division multiplexing optical transmitter and wavelength

Pumping light from two pumping light sources is supplied to an optical coupler which splits it into two output beams and supplies the beams to erbium-doped optical fibers in the forward and backward paths, respectively. To avoid the detrimental effect caused by interference that occurs when the wavelengths of the two pumping light sources coincide perfectly with each other, the two pumping light sources are activated alternately by clock signals that are 180.degree. out of phase with each other. Alternatively, optical shutters may be provided between the optical coupler and the respective pumping light source, and these optical shutters may be opened alternately. If one or other of the pumping light sources stops due to failure, the average level of the pumping light supplied to the optical fibers will drop. To compensate for this, it will be preferable to make provision so that when a fault is detected in one light source, pumping light is continuously supplied to the optical coupler from the other pumping light source.

Optical-fiber amplifier

An optical repeater having a loop-back function is provided in a transmission system including first and second transmission lines. The optical repeater includes a first optical amplifier connected to the first transmission line, a second optical amplifier connected to the second transmission line, a loop-back unit connected to both transmission lines, and a control unit. The control unit controls the loop-back unit to form a loop-back line when a loop-back instruction is detected. Therefore, optical signals are directly amplified without being converted into electrical signals, and a loop-back signal (return signal) and optical signals are not mixed in the optical repeater so that a loop-back operation can be correctly carried out in an optical repeater having a small size and low power consumption.

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Kawasaki, Japan

Takanori Maki