Abstract: In frame transfer in a network for transferring an Ethernet frame sent from a source on the network to a predetermined destination, to an applied Ethernet frame, an expansion tag containing information about forwarding to an egress edge node to a host as a destination is added to make an expansion frame, and each node on the network relays the data frame based on the forwarding information of the added expansion tag to transfer the frame to the egress edge node.

Abstract: A node that configures a spanning tree over a network to which a plurality of nodes are connected generates a tree after a cost change using another LAN while continuing to operate the tree that existed before the change, and switches the tree that is used for forwarding after the new tree has been stable.

Abstract: A node to relay the Ethernet frame provided with means to insert, in the relay process of the frame, two or more VLAN tags into the frame at a time and to remove the inserted VLAN tags wherein a TTL area to show the frame survival time is provided in the VLAN tag to be inserted to the frame so that whether the survival time has been elapsed or not is checked by the value in the TTL area and the frame after elapse of the survival time is discarded without being relayed.

Abstract: In a communication system in which a plurality of communication terminals sequentially transfer data to a server during the respective transmission permissible periods assigned to the respective communication terminals, the communication terminal transfers a preamble for synchronization to the server at a time of starting the transmission permissible period, converts a data frame for every 8 bits into every 10 bit-code, and transmits to the server, the signal string with a code indicating the head added there, during the transmission permissible period, and turns a communication to the server into a zero signal state, during a period other than the transmission permissible period, while the server establishes a synchronization by reading the preamble for synchronization inserted into the signal string received from each of the communication terminals, converts a portion of the zero signal state of the signal string into a predetermined special code string, and inversely transforms the received signal string i

Abstract: In a communication system for transmitting and receiving communication frames between a plurality of communication terminals and a server, a control frame which is indicative of control information necessary for communication between the communication terminals and the server and whose size is smaller than the size of the communication frame is transferred being included in a preamble portion of each communication frame and when no communication frame to be transmitted exists, the control frame is transferred as an independent frame.

Abstract: A remote station creates a transfer frame with one synchronous bit string added to at least one or more client frames and sends this transfer frame to a base station, when multiplexing the client frame received from a client system through an optical fiber and transferring the same to the base station.

Abstract: A surface acoustic wave device includes a package having an element mounting surface, a surface acoustic wave element provided in the package and having at least one bonding electrode, an adhesive arranged such that the surface acoustic wave element is fixed to the element mounting surface of the package, and at least one bonding wire connected to the at least one bonding electrode. The at least one bonding electrode has at least one line-shaped through hole extending therethrough at a region where the at least one bonding wire is connected to the at least one bonding electrode.

Abstract: A surface acoustic wave device substantially eliminates a stress caused by a curing shrinkage of an adhesive and substantially eliminates a strain in a case containing a surface acoustic wave element to prevent variation in characteristics of the surface acoustic wave device. In addition, a strength of joining of bonding wires provided in the surface acoustic wave device is improved to have an improved reliability. The surface acoustic wave element of the surface acoustic wave device is fixed on a case member via a soft adhesive and bonding electrodes of the surface acoustic wave element have a plurality of through holes. Ends of the bonding wires are wire-bonded to the bonding electrodes having the through holes formed therein.

Abstract: Disclosed is an optical network which has a plurality of subordinate optical networks, each of which being connected with a plurality of optical terminals which function as a transmitter and a receiver of a signal light, wherein multiplexing of transmission signals and demultiplexing of reception signals at the optical terminals are carried out in the subcarrier multiplexing manner; and a main optical network which is connected with the subordinate optical networks, wherein multiplexing of signal lights transmitted from the subordinate optical networks is carried out in the wavelength division multiplexing manner.

Abstract: Disclosed is an optical network which has a plurality of subordinate optical networks, each of which being connected with a plurality of optical terminals which function as a transmitter and a receiver of a signal light, wherein multiplexing of transmission signals and demultiplexing of reception signals at the optical terminals are carried out in the subcarrier multiplexing manner; and a main optical network which is connected with the subordinate optical networks, wherein multiplexing of signal lights transmitted from the subordinate optical networks is carried out in the wavelength division multiplexing manner.

Abstract: An optical transmission system of an N : 1 or an N:N type is provided, in which there is no deterioration caused by beat noise between signals. A plurality of optical modulators are cascaded in an optical fiber transmission path having a light source and a plurality of light receivers connected to two respective ends of the optical fiber transmission path, and carrier waves having frequencies respectively different are applied to the optical modulators. This enables the light receivers to receive a radio frequency signal in which the carrier waves are frequency-multiplexed. The light receivers receive only the signal beam so that there is no occurrence of beat noise. In another arrangement, at the optical network terminal, a part of a signal beam is split and the split beam is intensity-modulated responsively to carrier waves by an optical modulator and, thereafter, is combined again to a passing beam.

Abstract: The subcarrier frequency multiplexed optical transmission system disclosed is one in which a plurality of analog subcarrier signals and at least one digital subcarrier signal is optically transmitted by frequency multiplexing. The system includes an amplitude limiter, a filter, a multiplexer and a semiconductor laser. Portions of the analog subcarrier signals which are lower in level than the threshold value of the semiconductor laser are eliminated by the amplitude limiter, and further impulse distortions generated due to clipping in the frequency band of the digital subcarrier signal are eliminated by the filter. Then, the analog and digital subcarrier signals are frequency multiplexed to be inputted to the semiconductor laser. The system enables to reduce the transmission quality deterioration of digital subcarrier signal caused by clipping.

Abstract: An optical module for use in a subcarrier multiplexed (SCM) optical transmission system and capable of reducing the distortion of a signal light due to multiple reflections. A distortion reducing device is implemented by an optical fiber cable longer than the coherence length of the signal light and is located at each of signal input and output portions or each portion where optical devices are jointed together within the module.

Abstract: A cellular mobile communication system in which each of one or more cells is provided with a base radio station, and mobile terminals communicate with the base radio stations. Base radio stations (21, 22 and 23) are connected to a central base station (100) by optical fibers. The central base station is connected to a mobile switching center (50). Each of the base radio stations is provided with an O/E converter (201) and E/O converter (207). The O/E converter converts a optical signal containing speech signals and a call connection control signal into RF signals. The E/O converter (207) converts RF signals, received from a mobile terminal (11) via an antenna (204), into optical signals and transmits the optical signals to the central base station.

Abstract: The present invention provides a resonance-type optical receiver circuit which keeps predetermined small distortion even when the received light level becomes high. The resonance-type optical receiver circuit varies the resistance value of variable resistance element 80, which is used as a load resistor to optical detector 4, in response to the intensity of output signal 10 of an amplifier. The load resistor varies in response to a variations of the received light level of the optical detector in this manner to keep the input to the amplifier lower than a fixed value.

Abstract: The present invention provides a resonance-type optical receiver circuit which keeps predetermined small distortion even when the received light level becomes high. The resonance-type optical receiver circuit varies the resistance value of variable resistance element 80, which is used as a load resistor to optical detector 4, in response to the intensity of output signal 10 of an amplifier. The load resistor varies in response to a variations of the received light level of the optical detector in this manner to keep the input to the amplifier lower than a fixed value.

Abstract: The present invention provides a resonance-type optical receiver circuit which keeps predetermined small distortion even when the received light level becomes high. The resonance-type optical receiver circuit varies the resistance value of variable resistance element 80, which is used as a load resistor to optical detector 4, in response to the intensity of output signal 10 of an amplifier. The load resistor varies in response to a variations of the received light level of the optical detector in this manner to keep the input to the amplifier lower than a fixed value.

Abstract: In a polarization diversity heterodyne receiving device comprising a first arrangement (16 to 18, 21 to 24, 26, 27) for receiving an incident signal beam having an incident beam intensity and an incident state of polarization to produce IF signals having signal amplitudes and a second arrangement (31, 32) for demodulating the IF signals into baseband signals which are combined into a device output signal having an output amplitude independent of the incident state, a comparing arrangement (34 to 36) produces a control signal which is feedback supplied to the first arrangement to adjust the signal amplitudes in a common ratio so as to render the output amplitude independent of the incident beam intensity.

Abstract: To supply a frequency control signal to a laser diode module for generating a laser beam susceptible to a variation in frequency or wavelength, a frequency stabilizing device comprises a birefringent body (21) for converting the variation to a variation in a polarization state of the laser beam to produce a polarization varied beam, which a polarization separating element (22) separates into first and second beam components having orthogonally polarized directions and first and second beam intensities. Optical detectors (26,27) detect the beam intensities to produce first and second detection signals. A subtracter (28) calculates a difference between the beam intensities. A control signal producing arangement (29) produces the frequency control signal in compliance with the difference. Preferably, the difference is normalized by a sum of the beam intensities. The birefringent body may be a uniaxial or a biaxial body. The uniaxial body should have an optic axis which forms an angle of 45.degree.

Abstract: Two intermediate frequency signals, which are used in a polarization diversity optical heterodyne receiver operable according to demodulation and subsequent combination and have a common intermediate signal frequency variable in an intermediate frequency range, are subjected to delaying relative to each other and then combined into a combined intermediate frequency signal. A frequency discriminator (24) discriminates the intermediate signal frequency of the combined intermediate frequency signal to produce a control signal for use in stabilizing a local optical frequency of a local beam used in combination with a signal beam susceptible to polarization fluctuation. A delay may be given for the delaying to one of the two intermediate frequency signals alone. Alternatively, a delay may be given for the delaying to only one of two local beam components which are coupled to two signal beam components for use in producing the two intermediate frequency signals.