Abstract: An implicit function field of a nonmanifold is held in a form of volume data; a value of an implicit function at a point between lattice points is decided by interpolation; and if a difference in code distances between two adjacent voxels to be interpolated is larger than a fixed width, no surface is formed between the voxels. Furthermore, an entered curved surface is broken down into curved surface patches which enable determination of a front and a back; numbers are given to the front and the back, respectively, to be distinguished from each other; and a space is classified into a plurality of regions by using the number of a surface of a nearest point.

Abstract: In a spatial transmission optical transceiver, signals of two lines from a feeder-affixed twisted pair line 17 which is a data transmission line based on IEEE1394 standard are converted to signals of one line by a code conversion circuit 14, and further converted to optical signals and emitted to space by a optical transmitter 15. The optical signal transmitted through the space is converted to an electrical signal by a optical receiver 16. The code conversion circuit 14 receiving the electrical signal of one line thus converted to signals of two lines, and transmits the signals onto the feeder-affixed twisted pair line 17. The electrical signal from the optical receiver 16 is input to an interception and insertion/removal detection circuit 13 to detect the presence or absence of the optical signal and judge whether the received signal is a reflection signal, thereby detecting the interception of a communication path and the insertion/removal of a signal line connected to a confronting optical transceiver.

Abstract: The present invention provides a network service information providing system which allows users to readily know a location and radio transmission parameters for connecting to a narrow-area wireless communications system in a system which contains a mixture of wide-area wireless communications systems and narrow-area wireless communications systems and to set up a new narrow-area wireless communications system which can provide higher communications services without causing degradation in existing communications services in the environment where different wireless communications systems coexist. The user knows his/her own location through a wide-area wireless communications system and sends the location of a narrow-area wireless communications system which he/she wants to connect to, wireless transmission parameters, and other requirements to a wireless area information server.

Abstract: To provide a terminal location estimation method capable of accurately estimating a location of a mobile terminal when providing information services according to the location of the terminal in a radio communication system. A positioning server sends a location measurement probe message to the mobile terminal in order to measure the location of the terminal. Each of base stations receives a response message broadcasted from the terminal, measures the reception level and delay spread and sends the measurement results to the positioning server. The positioning server has a radio wave propagation estimating portion and a database for storing estimation results thereof. The server estimates the location of the terminal by checking the measurement results of the base stations against the estimation results on radio wave propagation stored in the database.

Abstract: An alerting device allowing easy estimation of possible interference and useful suggestions to eliminate deteriorated communication quality due to interference is disclosed. A signal including a band used by a target radio communication system is selected from a received signal based on a prescribed system specification of the radio communication system. A detected signal level of the selected signal is detected and compared with the prescribed interference level. When the detected signal level is greater than the prescribed interference level, it is determined that interference occurs. Further, an interference source is estimated by analyzing the selected signal with respect to time and frequency components.

Abstract: To provide a propagation environment notification method in radio communication allowing a user to easily understand radio propagation environment information. When receiving a service start command C1 from a user terminal 100, a server 102 transfers software for clients to the user terminal 100 (C2). The user terminal 100 starts the transferred software for clients, and a user condition inputting process P2 is carried out to collect user specific information and radio base station information and transfer the same to the server 102 (C3). When receiving the information, the server 102 starts a distribution information generating process P1 for generating radio propagation environment information based on the information, and the generated information is transferred to the user terminal 100 (C4), and is converted into a format convenient for the user by the software for clients transferred on the user terminal 100, and displayed on the user terminal 100 (P3).

Abstract: An optical transmitter/receiver transmits and receives optical signals between terminal devices of a network which are connected by a twisted pair cable with a feeder line. The optical transmitter/receiver has an electric connector for connection to the twisted pair cable, a peak holding circuit for detecting whether there is an optical signal in an optical fiber based on an output signal from an optical receiver, and a biasing circuit for applying a bias voltage to the twisted pair cable. The biasing circuit applies a bias voltage to a twisted pair of the twisted pair cable if there is an optical signal in the optical fiber, and stops the application of the bias voltage to the twisted pair if there is no optical signal in the optical fiber. The terminal devices are capable of detecting insertion or removal of the twisted pair cable or the optical fiber.

Abstract: Disclosed is an optical fiber network system which has optical transmitter-receivers disposed in optical network units(ONUs) of number N.

Abstract: A fiber-optic access system for subscriber optical communication adopting star type topology in an optical fiber network includes a central office, a plurality of optical network units, an optical interface, and a signal recognition/reproduction and clock extraction IC. The optical interface is provided in the central office and includes an array optical transmission module as a package unit accommodating a plurality of light sources and a plurality of output fiber terminals, and an array optical reception module as a package unit accommodating a plurality of optical sensors and a plurality of input fiber terminals. The signal recognition/reproduction and clock extraction IC is provided to each channel of the array optical reception module. The access system provided is of a scale comparable to that of a central office side optical interface of PDS and wide band characteristics comparable to those of a single star type system.

Abstract: An interface device includes a transmission level converting circuit for converting a differential amplitude voltage of different signs, output from an IC for a transmission line driving circuit pursuant to IEEE 802.3 10 Base T, into an output voltage of a single pole code. The interface device also includes a reception level conversion circuit for converting a voltage of a single pole code into a differential amplitude voltage of different signs to an IC for driving a transmission line driving circuit, and an optical transceiver to which the single pole code voltage is input and output. A transmission line driving circuit is provided to enable connection to an optical fiber via the optical transceiver.

Abstract: In an optical network unit of an optical access network, an optical receiver is connected through a single-mode fiber optic link to a central office for receiving therefrom an ATM cells having a rate in conformance to the transmission capacity of the link. Multiple line interface cards are associated respectively with subscriber drop lines.

Abstract: An optical transmission method which suppresses waveform distortion caused by an in-optical fiber non-linear optical effect in a long-distance coherent optical communication system. The modulation index of a transmitting station is increased or decreased with respect to the value at which the best receiver sensitivity is realized in a condition in which an optical fiber is not in its transmitting condition. Otherwise, the delay amount of a delay detection circuit of a receiving station is increased or decreased with respect to the value at which the best receiver sensitivity is realized in a condition in which the optical fiber is not in its transmitting condition.

Abstract: In a wavelength division multiplexed optical communication network which includes a transmitter including a multiplexing arrangement (15-17) for wavelength division multiplexing signal beams of a plurality of channels into the multiplexed signal beam for reception by at least one receiver (12) capable of producing a data carrying intermediate frequency signal by using a local optical beam in receiving the signal beam of a selected channel, the transmitter comprises a modulating arrangement (15) for frequency modulating optical beams of the channels into frequency modulated beams by channel discrimination signals (18) having different frequencies in correspondence to the channels before (19) the signal beams are multiplexed.

Abstract: An automatic frequency control system, for an optical coherent communication system, in which an output frequency of a local oscillator is swept by a frequency sweep signal FM-modulated with a frequency shift signal. The FM-modulated local frequency is combined with an input optical signal and heterodyne-detected. A frequency shift signal component derived from a heterodyne detection output is compared with the frequency shift signal to verify whether or not the local oscillation frequency is in a predetermined range with respect to the input signal frequency. When it is in the predetermined range, the system operates to terminate the frequency sweep signal and remove the frequency shift signal and is switched to oscillation frequency control of the local oscillator by using a d.c. component of the hterodyne detection output.

Abstract: In a polarization control system for use in an optical communication system comprising an optical fiber (11), first and second polarization control devices (31, 41) are controlled to make the optical fiber bidirectionally transmit first and second signal beams with their respective incident polarization states rendered coincident with a common one or with respective ones of two principal states of the optical fiber. When the first signal beam is supplied to the first polarization control device with a first original polarization state and passes through the second polarization control device with a first variable polarization state and when the second signal beam is supplied to the second polarization control device with a second original polarization state and passes through the first polarization control device with a second variable polarization state, the first polarization control device keeps the second variable polarization state parallel or orthogonal to the first original polarization state.

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.

Abstract: In an optical communication system where first and second transmitter devices (12, 16) bidirectionally transmit first and second signal beams through an optical fiber (11) and first and second receiver devices (13, 17) receive the second and the first signal beams, respectively, a polarization control system comprises a polarization control unit (21) between the optical fiber and the first transmitter and receiver devices and a controller (23) for controlling the polarization control unit by a detected signal produced by the first receiver device so as to supply the second signal beam to the first receiver device with a constant reference polarization state. The first signal beam may be an FDM signal beam. In this event, the second receiver device comprises tunable receivers (R.times.1/100) which may be installed in a hub together with the second transmitter device and connected to terminal units through metal cables.

Abstract: Frequency division multiplex signal lights are propagated through an optical fiber, and polarizations of the lights are collectively controlled by a polarization controller. The polarization-controlled signal lights are received separately in receiving systems including optical heterodyne or homodyne receivers. In the collective polarization control, a step is selected from steps of controlling relative polarization states of local oscillation lights to coincide to each other, receiving a control signal from one of the receiving systems which receives a signal light of a frequency to be allocated in the center of a frequency band of the signal lights or the vicinity thereof, and dividing the frequency division multiplex signal lights into plural groups, thereby controlling polarizations collectively in each of the plural groups.

Abstract: In an optical apparatus for pulling an intermediate frequency in a predetermined frequency range, a local oscillation light source is swept in an oscillation frequency thereof in accordance with a signal applied to a frequency adjusting terminal thereof. The signal is of a counted value of a counter which counts pulse signals of an oscillator. When an intermediate frequency is pulled in a predetermined frequency range including a predetermined intermediate frequency, the counter is stopped to count the pulse signals, and is controlled to hold a then counted value which will be a fixed driving signal for the local oscillation light source.

Abstract: In an optical heterodyne homodyne detection apparatus, signal light and local oscillation light are combined, and the combined light is received in an optical detector to produce intermediate frequency signal which is then demodulated thereby producing base band signals. The frequency sweep of the intermediate frequency signal is performed so that the frequency of the intermediate frequency signal becomes a predetermined value. During the frequency sweep, at least one polarization of the signal light and the intermediate frequency signal is scrambled, and is stopped when the frequency becomes the predetermined value. Thereafter, polarizations of the signal light and the local oscillation light are coincided with each other in accordance with the polarization angle control.