Nec Corporation

Hirofumi Shimomura

Naoya Henmi

Hitoshi Takeshita

Seigo Takahashi

Tatsuya Shiragaki

Makoto Nishio

Multiple working paths are established on each working rings and multiple protection paths are established on each of multiple protection rings. A working path on a first working ring spans across first and second nodes for signal transmission in a first direction of the ring, and a working path on a second working ring spans across the first and second nodes for signal transmission in a second, opposite direction of the ring. A protection path on a first protection ring spans across the first and second nodes for signal transmission in said second direction, and a protection path on a second protection ring spans across the first and second nodes for signal transmission in said first direction. The first and second nodes normally use the working paths, respectively. When one of the working paths fails, the first and second nodes use a corresponding protection path.

Ring network for sharing protection resource by working communication paths

The first present invention provides an optical switch including the following elements. At least a plurality of optical transmission lines are provided for transmissions of optical signals. Each of the at least plurality of optical transmission lines have at least an impurity doped fiber. At least an excitation light source is provided for emitting an excitation light. At least an excitation light switch is provided which is connected to the excitation light source and also connected to the at least plurality of optical transmission lines for individual switching operations to supply the excitation light to the at least plurality of optical transmission lines to feed the excitation light to the impurity doped fiber on the at least plurality of optical transmission lines, thereby causing an excitation of the impurity doped fiber on selected one of the at least plurality of optical transmission lines so as to permit a transmission of the optical signal through the excited impurity doped fiber, whilst unselected one of the impurity doped fibers is unexcited whereby the optical signals are absorbed into the unselected one of the impurity doped fibers thereby to discontinue transmission of the optical signal by the unselected one of the impurity doped fibers.

Optical switch, optical amplifier and optical power controller as well as optical add-drop multiplexer

An optical wavelength division couplerwavelength-divides a wavelength multiplexed light to respective wavelength lights each of which is dropped to an optical gate switch-i (i=1&#x2dc;n) and a light receiver-i by an optical coupler-i and supplied to an optical light fault monitorthrough the light receiver-i. When the optical signal deterioration monitordetects an optical loss of wavelength (OLOW), an optical loss of signal (OLOS) or an optical signal degrade (OSD) in wavelength lights processed by the optical coupler-i as a fault detection signal in an optical layer, a controllercontrols the optical gate switch-i to cut off wavelength light passing therethrough and sends an optical alarm indication signal (AIS-O) to a downstream side. Therefore, when a loss of signal is detected by the light receiver-i, the optical signal deterioration monitorcan know the alarm indication signal (AIS) from the upstream side, removing the necessity of special hardware therefor.

Optical add-drop multiplexer

Disclosed is an optical switch for transmitting or shutting down an input light signal in accordance with a set switching state. The optical switch comprises first and second optical amplifiers connected in cascade. When an optical fiber amplifier comprising EDFs ( and ) and pumping sources ( and ) is used as the first and second optical amplifiers, the switching is accomplished by switching on or off the pumping sources ( and ) in accordance with control signals supplied from a control circuit ( ). One input light signal can be dropped through a first optical branch ( ) located on the input side of the optical switch, while another input light signal can be added through a second optical branch ( ).

Optical switch and optical network

In a ring topology network, a number of nodes interconnect transmission links to form first and second working rings and first and second optical protection rings in a ring topology. Multiple working paths are established on each working ring and multiple protection paths are established on each protection ring corresponding to the working paths. A first working path spans across first and second nodes for transmission of a signal in a first direction of the ring topology, and a second working path of the second working rings spans across the first and second nodes for transmission of a signal in a second direction of the ring topology opposite to the first direction. A first protection path on the first protection ring spans across the first and second nodes for transmission of a signal in the second direction of the ring topology, and a second protection path of the second protection ring spans across the first and second nodes for transmission of a signal in the first direction of the ring topology. The first and second nodes normally use the first and second working paths, respectively. Responsive to a failure of one of the first and second working paths, the first and second nodes use a corresponding one of the first and second protection paths, instead of the failed working path.

A signal quality monitoring method with reliability is disclosed. After extracting a clock signal from the light signal, a decision region is set for each bit of the light signal. The decision region is defined by a plurality of threshold amplitudes corresponding respectively to threshold phases which are produced with respect to the clock signal. The quality of the light signal is monitored depending on whether an amplitude of the light signal falls into the decision region at timings of the N threshold phases.

Optical signal monitoring method and apparatus

The first present invention provides an optical switch including the following elements. At least a plurality of optical transmission lines are provided for transmission of optical signals. Each of the at least plurality of optical transmission lines have at least an impurity doped fiber. At least an excitation light source is provided for emitting an excitation light. At least an excitation light switch is provided which is connected to the excitation light source and also connected to the at least plurality of optical transmission lines for individual switching operations to supply the excitation light to the at least plurality of optical transmission lines to feed the excitation light to the impurity doped fiber on the at least plurality of optical transmission lines, thereby causing an excitation of the impurity doped fiber on selected one of the at least plurality of optical transmission lines so as to permit a transmission of the optical signal through the excited impurity doped fiber, whilst unselected one of the impurity doped fibers is unexcited whereby the optical signals are absorbed into the unselected one of the impurity doped fibers thereby to discontinue transmission of the optical signal by the unselected one of the impurity doped fibers.

The first present invention provides an optical switch including the following elements. At least a plurality of optical transmission lines are provided for transmissions of optical signals. Each of the at least plurality of optical transmission lines have a least an impurity doped fiber. At least an excitation light source is provided for emitting an excitation light. At least an excitation light switch is provided which is connected to the excitation light source and also connected to the at least plurality of optical transmission lines for individual switching operations to supply the excitation light to the at least plurality of optical transmission lines to feed the excitation light to the impurity doped fiber on the at least plurality of optical transmission lines, thereby causing an excitation of the impurity doped fiber on selected one of the at least plurality of optical transmission lines so as to permit a transmission of the optical signal through the excited impurity doped fiber, whilst unselected one of the impurity doped fibers is unexcited whereby the optical signals are absorbed into the unselected one of the impurity doped fibers thereby to discontinue an transmission of the optical signal by the unselected one of the impurity doped fibers.

An optical wavelength division coupler wavelength-divides a wavelength multiplexed light to respective wavelength lights each of which is dropped to an optical gate switch -i (i&equals; &tilde;n) and a light receiver -i by an optical coupler -i and supplied to an optical light fault monitor through the light receiver -i. When the optical signal deterioration monitor detects an optical loss of wavelength (OLOW), an optical loss of signal (OLOS) or an optical signal degrade (OSD) in wavelength lights processed by the optical coupler -i as a fault detection signal in an optical layer, a controller controls the optical gate switch -i to cut off wavelength light passing therethrough and sends an optical alarm indication signal (AIS-O) to a downstream side. Therefore, when a loss of signal is detected by the light receiver -i, the optical signal deterioration monitor can know the alarm indication signal (AIS) from the upstream side, removing the necessity of special hardware therefor.

Disclosed is an optical signal repeating and amplifying device which has: an optical amplifier which amplifies an optical signal to be input thereto and then outputs it; and an optical filter means through which only one wavelength light of the optical signal to be output from the optical amplifier is passed. Also disclosed is an optical level adjusting device which has: an optical demultiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights; a plurality of optical attenuators which attenuate separately the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer; and an optical multiplexer which multiplexes the attenuated wavelength lights to be output from the plurality of optical attenuators into a wavelength-multiplexed optical signal and output it.

Optical signal repeating and amplifying device and optical level adjusting device

There is disclosed an array type space optical switch of the present invention, in which each one end of optical fibers to to is fixed to support members . The optical fibers and form one pair, and have end surfaces opposite to each other, and the optical fibers and form one pair, and have end surfaces opposite to each other. Moreover, the optical fibers and form one pair, and have end surfaces opposite to each other, and the optical fibers and form one pair, and have end surfaces opposite to each other. A space propagation part is formed between the end surfaces of the optical fibers to and to . An interrupting plate is inserted to or extracted from the space propagation part

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Tokyo, Japan

Hirofumi Shimomura