Hitachi, Ltd.

Hitachi Communication Technologies, Ltd.

Masahiko Mizutani

Yoshihiro Ashi

Tohru Kazawa

Masayuki Takase

Kenichi Sakamoto

Hideki Endo

Yusuke Yajima

Toshiki Sugawara

Hiroki Ikeda

Takayuki Kanno

Atsushi Iwamura

Nobuyuki Yamamoto

Takeshi Shibata

Masanobu Kobayashi

Masao Niibe

Shinya Fujioka

Ryosuke Nishino

Morihito Miyagi

Takeshi Yasuda

Akihiko Tanaka

Shinya Sasaki

Shinichi Akahane

Shinobu Gohara

Kazuyoshi Hoshino

Norihiro Sakamoto

Hiroaki Nakazawa

Akihiko Tsuchiya

Makoto Kitani

Shigeaki Kinoshita

Taishi Shinagawa

Masayuki Hino

Takeshi Kiyose

Hideyuki Nakanishi

Daiji Mitsunaga

In an extensive distribution system with no delay guarantee network used as a relay network, an influence of a fluctuation of a communication delay time is avoided to conduct a high-precision time synchronization. First and second delay control devices installed in junctions between communication networks and a relay network, respectively, have functions of retaining first and second time information, and setting a first relay network passing time of a first communication signal directed from a time dissemination device toward a time receiving device through a relay network, and a second relay network passing time of a second communication signal directed from the time receiving device toward the time dissemination device, respectively. In measurement of communication delay time of the first communication network and the second communication network prior to time synchronization, the first and second relay network passing times are unified in advance to exclude uncertainty of the communication time.

Communication system and time synchronization method

A transmission device uses transmission delay time of reciprocation with the terminal and time information of the transmission device to create a correction value of time information of the terminal and transmits it to the terminal. The terminal includes expected arrival time information based on the time information of the terminal and the correction value received from the transmission device in a frame transmitted to the transmission device. The transmission device compares reception time of the frame with the expected arrival time information in the frame. If they match, the time information of the terminal synchronizes with the time information of the transmission device. If they do not match, the transmission device transmits a new correction value to the terminal. The terminal transmits a frame including expected arrival time information using the new correction value to the transmission device.

Communication system and its device

A transmission network system includes a network terminating device connected to a user terminal and an authentication information device connected to the network terminating device through a transmission network. The transmission network is connected to a reference clock that holds a reference time. The network terminating device includes a terminating internal clock that synchronizes with the reference clock, when receiving a first frame from the user terminal, generates a second frame including a time outputted from the terminating internal clock as a request time on the basis of the first frame, and transmits the second frame to the authentication information device. The authentication information device generates time authentication information based on the request time included in the received second frame, generates a third frame including the generated time authentication information, and transmits the third frame to the transmission network.

Transmission network system, transmission method, and authentication information device

A redundant path configuration method and a control method are disclosed. An intercommunication path for mutually transmitting and receiving a signal is provided among the BHEs each of which is a top of a tree. When failures occur in an active system path in certain AE, a standby system path (BHE) relays communication between the AE and the (active system) BHE so as to secure continuity of communication. The intercommunication path through which a data signal does not flow in a normal operation is used as a traffic accommodation path in an emergency among the BHEs. By setting a bypass between the tops of the trees, when a failure occurs in one tree, a signal is transferred from the active system BHE to the standby system path in which another BHE is a top to build a sub-tree bypassing the failure point and to secure a communication path.

Communication network system and communication network configuration method

When an ONU accommodating range is enlarged, and ONUs shorter and ONUs longer in a communication path to an OLT are accommodated in a PON at the same time, there is a need to change a light intensity at the time of transmitting a downstream signal in order that both of the ONUs receive a downstream signal from the OLT. When a near-end ONU receives a signal having a light intensity necessary to communicate between the OLT and a far-end ONU, there arises such a problem that the light intensity is as high as an ONU receiver fails. In order to eliminate the ONU failure of the above problem, prior to transmission of the downstream signal, a downstream signal transmission schedule (downstream light intensity map) is notified to all of the ONUs. An optical transceiver of the OLT has a function of adjusting an output light intensity, and adjusts the light intensity to values receivable by the individual ONUs when the signal arrives at the respective ONUs according to route distances to the respective ONUs.

Passive optical network system

When data is disclosed to a plurality of users by using a transfer network and a transfer apparatus, data disclosure time control which cannot be adversely affected by the users is performed to reduce the difference in data disclosure time among the users. A transfer network system includes a distribution server serving as a data-distribution-source transfer apparatus, and a network terminal connected to distribution-destination user equipment. The distribution server and the network terminal each have a time keeping function and a time synchronization function for matching the time of the time keeping function with a master clock. The distribution server sends in advance disclosure data and disclosure time to the network terminal. When the time of the time keeping function of the network terminal matches the disclosure time, the network terminal sends the disclosure data to the user equipment.

Transfer apparatus, transfer network system, and transfer method

An interconnection between fully synchronous networks and next-generation frame communications networks is disclosed. A means of bidirectional frame format conversion between a synchronous multiplexing system and a logical multiplexing system is provided, along with a method of transmitting data between different networks on a path as if it were being transmitted in the same network. Further, when converting network control information in an STM network into data suitable for a packet network, even across the boundary of a synchronous multiplexing system and a logical multiplexing system, a unified communication management means is provided over the whole path.

System apparatus and method for interconnecting TDM and frame/packet communication networks

Switching process at the occurrence of a path trouble is performed more quickly to reduce the number of packet discards during a traffic transition from a currently used system path to a standby system path within a section to be protected. An OLT (-W) refers to the DBA information of a PON section and, if receiving no CCM frame at a timing at which the same should be received, then determines that some trouble has occurred on the path (S) and transmits, to an OAM-compliant NE (-Z), an application-for-switching frame () to notify the OAM-compliant NE (-Z) of the abnormal condition. The OAM-compliant NE (-Z) monitors the occurrence of the trouble within the PON section nearly in real time, starts a switching process (S) and generates and transmits a standby-system delivery request () (SS). An OAM-compliant NE (-A) switches the communication path to the standby-system passing through an OLT (-P).

Communication system, subscriber accommodating apparatus and communication method

It is necessary to completely remove overlapping of signals between plural PONs in order to make the PONs coexist. Accordingly, it is required to share or intensively manage bandwidth use conditions over an optical fiber that serves as a common band between plural systems. Therefore, transmission clocks should be synchronized with high accuracy between plural systems. A reference clock is provided from an external device or a representative OLT to the entire systems to perform clock synchronization between plural systems, so that the overall systems are synchronized by synchronizing each OLT with the reference clock. A hierarchical management method is selected that manages ONUs under the control of each OLT by managing band use information arranged for each OLT with respect to an external device or a representative OLT for sharing of bandwidth use conditions between plural systems.

Network system and optical line terminal

Network system, optical network unit and optical line terminal

In the communication system, a master station is coupled to slave stations by a fiber network comprising a splitter and a reach extender, the master station includes a first bandwidth control section which determines, based on a request from each slave station, a first data amount of a signal transmitted in a first cycle, the reach extender includes: a distance measurement section which measures a distance or a time between the reach extender and each slave station; and a second bandwidth control section which determines a second data amount and transmission timing of a signal based on a request from each slave station and the first data amount, and each slave station transmits a signal with a data amount, which the first bandwidth control section determined based on a data amount and transmission timing determined in second cycles, to the master station in the first cycle.

Optical communication system and communication bandwidth control method

In the configuration of an optical communication system interconnecting a parent station and a plurality of child stations via an optical fiber network equipped with an optical splitter, RE is provided having a measuring unit for measuring a transmission distance or time to a child station, a determining unit for determining a timing when a child station transmits a signal, in accordance with a transmission bandwidth request from the child station, and a signal processing unit for processing a signal received from a child station and transmitting the processed signal to the parent station. When a burst signal is received from each child station at the determined timing, a portion of the header of the burst signal is deleted, and a dummy signal is inserted into the deleted area and a gap area between received burst signals to convert the burst signals into a series of signals to be sent to the parent station.

Optical passive network system and its operation method

Communication arrangements wherein each of ONUs of a first or second PON transmits data toward a connected first or second OLT after a wait time period designated by the connected first or second OLT; the first communication device of the first packet communication network sends a first frame for measuring communication time period, to the second communication device of the second packet communication network through the first PON, and sends a second frame for measuring communication time period, to the second communication device through the second PON; and the second communication device calculates a difference of communication time period between the received first and second frames, and instructs the first or second OLT of the first or second PON, for correcting a wait time period which is set to the one or plural ONUs connected to the first or second OLT, based on the difference between communication time periods.

Communication system and communication apparatus

When a neighbor ONU receives a signal with light intensity high enough to secure communication between an OLT and a remote ONU, the light intensity may be excessively high to damage a receiver of the neighbor ONU. In order to avoid such a problem, each ONU is notified of a downstream signal transmission plan (downstream light intensity map) prior to transmission of a downstream signal. Each ONU receives the downstream light intensity map (light intensity transmission schedule of downstream signal) in advance. Thus, the neighbor ONU can block or attenuate an optical signal addressed to the remote ONU, and the remote ONU can determine normal operation even when the remote ONU cannot receive a signal addressed to the neighbor ONU. Thus, the remote ONU can be prevented from issuing a wrong error signal.

A transmitting apparatus includes a plurality of code spreaders different in spreading code, a reception processing unit that selectively distributes transmission data to the plurality of code spreaders, a plurality of optical transmitters each of which that transmit a code-spread signal to an optical fiber as a CDMA optical signal of a carrier wavelength different from that of the other optical transmitters, and a signal multiplexing unit that selectively supplies outputs of the plurality of code spreaders to the plurality of optical transmitters. A receiving apparatus includes an optical receiver that receives a wavelength-division-multiplexed CDMA optical signal from the optical fiber, and a plurality of despreaders connected to the optical receiver and different in spreading code, wherein each of the despreaders reproduces a CDMA signal corresponding to its spreading code from an output signal of the optical receiver.

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Kokubunji, Japan

Masahiko Mizutani