Abstract: 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.

Abstract: 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.

Abstract: A storage circuit defines a first field for storing first header bits of a first payload signal of a first data unit, a second field, and a third field for storing the first payload signal. The first header bits are equal in number to second header bits of a second payload signal of a second data unit. A division circuit divides the first header bits by a generator polynomial to produce a first error check code. The same generator polynomial is used to divide the second header bits to produce a second error check code. A remainder of division of hypothetical header bits by the generator polynomial is summed to the first error check code to produce a sum which is inserted into the second field of the storage circuit. The hypothetical header bits are greater in number than a total number of bits in the first and second fields, so that the first and second data units can be distinguished from each other by different error check results of the first and second data units.

Abstract: A storage circuit defines a first field for storing first header bits of a first payload signal of a first data unit, a second field, and a third field for storing the first payload signal. The first header bits are equal in number to second header bits of a second payload signal of a second data unit. A division circuit divides the first header bits by a generator polynomial to produce a first error check code. The same generator polynomial is used to divide the second header bits to produce a second error check code. A remainder of division of hypothetical header bits by the generator polynomial is summed to the first error check code to produce a sum which is inserted into the second field of the storage circuit. The hypothetical header bits are greater in number than a total number of bits in the first and second fields, so that the first and second data units can be distinguished from each other by different error check results of the first and second data units.

Abstract: An optical packet exchange apparatus and an optical switch in which search for a connection pattern between an input unit devoid of a packet to be transmitted and an output unit devoid of a packet to be received is reduced to enable fast switch control even in cases wherein the number of channels of the exchange apparatus is increased or network speed is higher. A plurality of input units, a plurality of output units and an optical switch are provided. Each input unit includes an input buffer unit, a parallel/serial conversion unit, an electrical/optical conversion unit, and a dummy packet insertion unit for sending a dummy packet if there is no packet to be transmitted. Each output unit includes an exchange counterpart contention resolution unit for controlling the exchange counterpart, an optical/electrical conversion unit, a serial/parallel conversion unit, and a packet eliminating unit. The exchange counterpart contention resolution unit controls the packet eliminating unit to eliminate a dummy packet.

Abstract: An optical wavelength division coupler 11 wavelength-divides a wavelength multiplexed light to respective wavelength lights each of which is dropped to an optical gate switch 15-i (i=1˜n) and a light receiver 13-i by an optical coupler 12-i and supplied to an optical light fault monitor 14 through the light receiver 13-i. When the optical signal deterioration monitor 14 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 12-i as a fault detection signal in an optical layer, a controller 19 controls the optical gate switch 15-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 13-i, the optical signal deterioration monitor 14 can know the alarm indication signal (AIS) from the upstream side, removing the necessity of special hardware therefor.

Abstract: 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 (11 and 12) and pumping sources (31 and 32) is used as the first and second optical amplifiers, the switching is accomplished by switching on or off the pumping sources (31 and 32) in accordance with control signals supplied from a control circuit (300). One input light signal can be dropped through a first optical branch (51) located on the input side of the optical switch, while another input light signal can be added through a second optical branch (53).

Abstract: An optical ring system having: a wavelength demultiplexer to which wavelength-multiplexed optical signal to be sent through an optical fiber from a previous node of multiple nodes is input and in which optical signal with each wavelength assigned to itself is demultiplexed; an optical ring device which is disposed in a predetermined node of the multiple nodes to the each wavelength assigned and which is composed of a failure existence judging part which terminates an overhead of each optical signal with a wavelength demultiplexed by the wavelength demultiplexer and judges whether a failure occurs in regard to a wavelength in a previous section through which optical signal with the assigned wavelength is sent, and a switching part which, when the failure existence judging means determines the occurrence of failure, selects a path that allows optical signal with the wavelength to be transmitted to the previous node while avoiding the previous section incurring the failure; and a wavelength multiplexer which mul

Abstract: An optical receiving circuit 1 is composed of a preamplifier circuit 2, an output differential amplifier 3 and a mean value holding circuit 4. The optical receiving circuit 1 is connected to a photodetector 5 for receiving an input optical signal and outputting current. For the preamplifier circuit 2, a transimpedance type circuit may also be used. The preamplifier circuit 2 comprises a feedback resistor 21 and a resistor for detecting output voltage 22, the transimpedance gain is 55 dB &OHgr; and 3 dB bandwidth when the photodetector 5 the capacity of which is 0.2 pF is connected to its output is 8 GHz. The output differential amplifier 3 discriminates and regenerates data by regulating reference voltage Vref between the high level and the low level of the amplitude of an input signal. The mean value holding circuit 4 includes a sample-hold circuit 41 and capacity 42 for holding the mean value of voltage output from the preamplifier circuit 2.

Abstract: 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 (11 and 12) and pumping sources (31 and 32) is used as the first and second optical amplifiers, the switching is accomplished by switching on or off the pumping sources (31 and 32) in accordance with control signals supplied from a control circuit (300). One input light signal can be dropped through a first optical branch (51) located on the input side of the optical switch, while another input light signal can be added through a second optical branch (53).

Abstract: 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 ring 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.

Abstract: 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.

Abstract: Optical signals having arbitrary wavelengths of wavelength-multiplex optical signals are separated in an optical add-dorop multiplexer 110. Switching of the signals after separation and an external signal that is input outside is conducted in an ATM switch 170. The signals after the switching by the ATM switch 170 is combined with wavelength-multiplex signals in the optical add-dorop multiplexer 110.

Abstract: An optical packet exchange apparatus and an optical switch in which search for a connection pattern between an input unit devoid of a packet to be transmitted and an output unit devoid of a packet to be received is reduced to enable fast switch control even in cases wherein the number of channels of the exchange apparatus is increased or network speed is higher. A plurality of input units, a plurality of output units and an optical switch are provided. Each input unit includes an input buffer unit, a parallel/serial conversion unit, an electrical/optical conversion unit, and a dummy packet insertion unit for sending a dummy packet if there is no packet to be transmitted. Each output unit includes an exchange counterpart contention resolution unit for controlling the exchange counterpart, an optical/electrical conversion unit, a serial/parallel conversion unit, and a packet eliminating unit. The exchange counterpart contention resolution unit controls the packet eliminating unit to eliminate a dummy packet.

Abstract: 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.

Abstract: 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.

Abstract: In a cross-connect switch for transmitting an input signal to any one of a plurality of outgoing lines, the cross-connect switch includes a switch of which output port is connected to any one of the plurality of outgoing lines, and each of the plurality of outgoing lines is connected to a predetermined one of a plurality of paths. If the input signal to the cross-connect switch is a wavelength division multiplexing optical signal, then the cross-connect switch further includes a demultiplexer for demultiplexing the input signal into wavelength components, and a multiplexer for multiplexing signals on the outgoing lines which are connected to any one of the plurality of paths. The switch may include a two-stage-linked connection circuit network. Moreover, the cross-connect switch includes a first wavelength converter inserted between the demultiplexer and an input port of the switch, and a second wavelength converter inserted between an output port of the switch and the multiplexer.

Abstract: 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.

Abstract: An optical packet exchange apparatus and an optical switch in which search for a connection pattern between an input unit devoid of a packet to be transmitted and an output unit devoid of a packet to be received is reduced to enable fast switch control even in cases wherein the number of channels of the exchange apparatus is increased or network speed is higher. A plurality of input units, a plurality of output units and an optical switch are provided. Each input unit includes an input buffer unit, a parallel/serial conversion unit, an electrical/optical conversion unit, and a dummy packet insertion unit for sending a dummy packet if there is no packet to be transmitted. Each output unit includes an exchange counterpart contention resolution unit for controlling the exchange counterpart, an optical/electrical conversion unit, a serial/parallel conversion unit, and a packet eliminating unit. The exchange counterpart contention resolution unit controls the packet eliminating unit to eliminate a dummy packet.

Abstract: An optical wavelength division coupler 11 wavelength-divides a wavelength multiplexed light to respective wavelength lights each of which is dropped to an optical gate switch 15-i (i=I˜n) and a light receiver 13-i by an optical coupler 12-i and supplied to an optical light fault monitor 14 through the light receiver 13-i. When the optical signal deterioration monitor 14 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 12-i as a fault detection signal in an optical layer, a controller 19 controls the optical gate switch 15-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 13-i, the optical signal deterioration monitor 14 can know the alarm indication signal (AIS) from the upstream side, removing the necessity of special hardware therefor.