Fujitsu Corporation

Mitsushi Nitta

Masaaki Takahashi

Shinichirou Harasawa

Takanori Maki

Katsumi Kikawa

Kazuya Amaki

Hiroshi Nakashima

An optical transmission system including a plurality of optical repeaters arranged along a transmission line. A respective gain equalizer is arranged along the transmission line after an integer number of optical repeaters. Further, each optical repeater can include an optical amplifier, a gain equalizer and a connection mechanism. The connection mechanism has a first state and a second state so that (a) when the connection mechanism is in the first state, the gain equalizer of the optical repeater performs an equalization process on the light signal, and (b) when the connection mechanism is in the second state, the gain equalizer of the optical repeater does not perform an equalization process on the light signal. An add/drop apparatus is also provided for adding/dropping an individual wavelength signal from a wavelength division multiplexed (WDM) signal travelling through the optical communication system. The add/drop apparatus includes a plurality of filters, and a selection mechanism. Each filter affects a different wavelength. The plurality of filters includes at least one filter affecting a wavelength corresponding to a wavelength signal in the WDM signal. The selection mechanism selects a respective filter of the at least one filter to allow the apparatus to add/drop the wavelength signal in the WDM signal corresponding to the wavelength of the selected filter.

Optical transmission system including optical repeaters with selectively

An object of the present invention is to provide an optical branching and insertion apparatus with which the damage location can be searched for in all sections when a damage location is searched for in an optical transmission system in which an optical branching and insertion apparatus has been installed. The present invention provides an optical branching and insertion apparatus comprising a filter for reflecting light of a specific wavelength, a first optical circulator operatively connected to one side of the filter, outputting to the filter first light inputted from a first transmission path, outputting to a second transmission path the light of the specific wavelength reflected from the filter, and outputting to the first transmission path second light inputted from the second transmission path and a second optical circulator operatively connected to the other side of the filter, outputting to the filter third light inputted from a third transmission path, outputting to a fourth transmission path the light signal of the specific wavelength reflected from the filter, and outputting to the third transmission path fourth light inputted from the fourth transmission path.

Optical branching and insertion apparatus

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

Mitsushi Nitta