Abstract: A multistage switch control circuit allows unit switches to be set at a higher speed than conventional multistage switch control circuits. Higher-order half first and second control elements are connected to a first section of a bus to form a first cluster, while lower-order half third and fourth control elements are connected to a second section of the bus to form a second cluster. A bus switch which functions as a cluster formation means is arranged between the first section and the second section of the bus to perform the connection/separation of the first section and the second section. The first to fourth control elements transmit switch control signals to corresponding unit switches, respectively, in each stage.

Abstract: A multistage switch control circuit allows unit switches to be set at a higher speed than conventional multistage switch control circuits. Higher-order half first and second control elements are connected to a first section of a bus to form a first cluster, while lower-order half third and fourth control elements are connected to a second section of the bus to form a second cluster. A bus switch which functions as a cluster formation means is arranged between the first section and the second section of the bus to perform the connection/separation of the first section and the second section. The first to fourth control elements transmit switch control signals to corresponding unit switches, respectively, in each stage.

Abstract: An optical wavelength division multiplexing network has a multi-level structure where a plurality of optical network units (ONUs) are connected to a lowest-level network. A node apparatus connected to networks other than the lowest-level network includes (a) passive optical components to branch optical signals from a higher-level network to a lower-level network, and couple optical signals from the lower-level network to the higher-level network, and (b) optical amplifiers for the optical signals. A node apparatus connected to the lowest-level network includes (a) an optical multiplexer/de-multiplexer to de-multiplex optical signals from the higher-level network, selectively output an optical signal to each ONU, and multiplex wave-length specific optical signals from the ONUs into a multiplexed optical signal, and (b) optical amplifiers for the optical signals.

Abstract: An optical wavelength division multiplexing network has a multi-level structure where a plurality of optical network units (ONUs) are connected to a lowest-level network. A node apparatus connected to networks other than the lowest-level network includes (a) passive optical components to branch optical signals from a higher-level network to a lower-level network, and couple optical signals from the lower-level network to the higher-level network, and (b) optical amplifiers for the optical signals. A node apparatus connected to the lowest-level network includes (a) an optical multiplexer/de-multiplexer to de-multiplex optical signals from the higher-level network, selectively output an optical signal to each ONU, and multiplex wave-length specific optical signals from the ONUs into a multiplexed optical signal, and (b) optical amplifiers for the optical signals.

Abstract: An optical wavelength division multiplexing network which can carry out large-capacity access service with a simple constitution is provided. In an optical network comprising a plurality of layers, a highest level network comprises a ring network having a center node and remote nodes; an intermediate level network comprises a ring centered around a node belonging to the higher level network, and a lowest level network comprises a star network centered around an access node which multiplexes traffic from a plurality of ONU, the ONU and the access node being directly joined together by optical fibers; the center node belonging to the highest level network and the ONU establish a direct communication path by using lights of different wavelengths; at nodes provided therebetween, the optical signals are not electrically processed but are amplified, branched, and routed.

Abstract: An optical wavelength division multiplexing network which can carry out large-capacity access service with a simple constitution is provided. In an optical network comprising a plurality of layers, a highest level network comprises a ring network having a center node and remote nodes; an intermediate level network comprises a ring centered around a node belonging to the higher level network, and a lowest level network comprises a star network centered around an access node which multiplexes traffic from a plurality of ONU, the ONU and the access node being directly joined together by optical fibers; the center node belonging to the highest level network and the ONU establish a direct communication path by using lights of different wavelengths; at nodes provided therebetween, the optical signals are not electrically processed but are amplified, branched, and routed.

Abstract: A disk shaped tunable optical filter is formed by a transparent substrate in a disk shape, and a filter layer formed on a top surface of the substrate, having such a filter characteristic that a transmission central wavelength varies along a circumferential direction as a monotonic function of a viewing angle. This disk shaped tunable optical filter can be advatageously utilized in realizing a wavelength discrimination apparatus, a reference wavelength light generation apparatus, an optical packet generation apparatus, and a tunable optical filter module, which are also disclosed.

Abstract: In an ultraviolet exposure apparatus, substances contained in an atmosphere contacting a lens surface are reduced, the substances generating accumulations on the lens surface. Openings are formed in the wall of a lens barrel to allow the atmosphere to be replaced by a proper gas. The proper atmospheric gas may be a gas not containing oxygen such as a nitrogen gas, or clean air obtained by intentionally generating accumulations by applying ultraviolet light to source air. A ultraviolet light source is preferably cooled by a cooling system different from the cooling system of a lens optical system.

Abstract: A multiwavelength simultaneous monitoring circuit capable of precise discrimination of wavelengths of a WDM (Wavelength Division Multiplexed) signal including multiplexed wavelength waves, and suitable for optical integrated circuits having large resistance to vibration.