Hitachi, Ltd.

Hitachi Communication Technologies, Ltd.

Hitachi Communication Systems, Inc.

Tohru Kazawa

Yusuke Yajima

Yoshihiro Ashi

Masahiko Mizutani

Kenichi Sakamoto

Masaki Ohira

Norihiro Sakamoto

Masayuki Takase

Ryosuke Nishino

Akihiko Tsuchiya

Takanori Miyamoto

Hideki Endo

Takeshi Shibata

Toshiki Sugawara

Takashi Morita

Masanobu Kobayashi

Toshiro Suzuki

Hiroki Ikeda

Atsushi Iwamura

Masao Niibe

Yoshinobu Morita

Shinya Sasaki

Ryosuke Kurata

Jun Sugawa

Akihiko Tanaka

Shigeo Nishita

Taishi Shinagawa

Takeshi Kiyose

Ichiro Masse

Masaki Oohira

Souichi Yamashita

Toshiroh Suzuki

Yukio Nakano

Hiroyuki Nakano

Satoshi Aoki

Masahiro Takatori

Eiichi Amada

Hideaki Tsushima

Shin Nishimura

Naohiro Sakakida

Hirotoshi Shirasu

Hironari Matsuda

Tatsuya Kameyama

Masatoshi Takihiro

Makoto Matsuoka

Hiroshi Takatori

Youichi Igarashi

Takahiro Tanaka

Satoshi Konno

Noboru Oosawa

Makoto Hasegawa

Atsushi Otani

Katsuyuki Miyazaki

Yoshihiro Yano

Taiki Nema

Kenta Komiya

Kazuyori Umematsu

Toyomi Teramoto

Toshihiro Ashi

Shota Takagi

Souichi Yamashima

Ichiro Mass'e

Kenji Tomooka

Ryoji Tateyari

An optical line terminal includes the transmission rate control table for storing a minimum bandwidth for an emergency status for each of optical network units in addition to a maximum assigned bandwidth in a normal status. When a decrease in a supply power is detected, the optical line terminal calculates a transmission clock rate providing a minimum bandwidth required by each optical network unit with reference to the transmission rate control table. The optical line terminal determines change timing of downstream and upstream transmission clock rates, and change timing of upstream data for time-division multiplexing to instruct each of the optical network units. Both the optical line terminal and the optical network unit change the transmission clock rates with substantial synchronization therebetween.

Passive optical network system, optical line terminal, and optical network unit

An example is a bandwidth control method employed in an optical line terminal including: determining a first time point at which a first optical network unit starts the processing of transitioning between the states in a case where the first optical network unit is to be transitioned between the states; transmitting a state control signal containing the first time point to the first optical network unit in order to control the first optical network unit to start the processing of transitioning between the states; and stopping allocating a bandwidth used to transmit a signal to the optical line terminal to a second optical network unit during a period from the first time point until it is determined that the first optical network unit has finished the processing of transitioning between the states.

Optical line terminal, bandwidth control method and optical network system

To, even when a transmission wavelength varies in each ONU and an optical amplifier gain depends on the wavelength in an OLT equipped with an optical amplifier, prevent the optical amplifier gain from varying in every ONU and thus prevent deterioration of a dynamic range. The OLT estimates a transmission wavelength of each ONU at the time of ONU registration, and retains a correspondence between an ONU identifier and the transmission wavelength. Moreover, for every burst, an injection current to the optical amplifier is adjusted based on a wavelength and optical amplifier characteristic database.

Burst-mode receiver equipped with optical amplifier, method for controlling optical amplifier, and system

Provided is a passive optical network system, wherein the electric power to be consumed is reduced on the basis of the quantity of signal to be transmitted downstream in a WDM-PON where signals having different transmission rates for wavelengths are mixed. In the passive optical network system, an OLT () and a plurality of ONUes () are connected by an optical fiber network including an optical splitter () and a plurality of optical fibers (and). The OLT () indicates to the ONUes () the wavelength to be used, in addition to the timing for transmission to the ONUes (). A format for signal transmission from the OLT () to the ONUes () comprises both the region, in which the timing for transmission to the ONUes () indicated by the OLT () to the ONUes () is stored, and the region, by which the wavelength to be used in the communication in the direction from the OLT () to the ONUes () is indicated.

Optical multiplexing terminal device, wavelength multiplexing passive optical network system and downlink wavelength transmission method

It is provided an optical access system, comprising an optical line terminal which is coupled to another network and optical network units which are coupled to the optical line terminal and to a plurality of user terminals. Each of the optical network units obtains a capacity of a buffer included in the each of the optical network unit and a link speed between the each of the optical network units and one of the plurality of user terminals that is coupled to the each of the optical network units; determines a sleep time based on the obtained capacity and the obtained link speed in a case where no communication frames are transmitted for a given period of time from any one of the plurality of user terminals and the optical line terminal; and sets in a sleep state for the determined sleep time.

Optical access system, optical network unit, and optical line terminal

Provided is a passive optical network system for operating a mixture of PONs with differing transmission speeds and is capable of reducing power consumption on the basis of the amount of signals being transmitted. The master station of the passive optical network system, which determines the amount and timing of signals sent thereto by each of a plurality of slave stations on the basis of the requests of the plurality of slave stations and receives signals from the plurality of slave stations via an optical fiber network, is equipped with a control unit that determines in each set cycle the amount, transmission timing, and transmission speed of the signals that each slave station is permitted to transmit to said master station on the basis of the amount of signals that each of the plurality of slave stations has requested to transmit, and that notifies such to each slave station. Additionally, each of the plurality of slave stations is equipped with a control unit that transmits signals to the master station at a first transmission speed or a second transmission speed that is faster than the first transmission speed, and is configured to transmit signals with either the first transmission speed or the second transmission speed on the basis of notifications from the master station.

Passive optical network system and operating method thereof

In a communication system using a PON, time synchronization of a slave device such as a base station is realized with respect to a master device such as an L2SW or the base station. Time information acquired by a GPS satellite is corrected by ranging information of a discovery function of an OLT so as to be reflected on time information of each ONU. A propagation delay from the L2SW to the OLT is obtained with the use of a delay estimation mechanism, a propagation delay from the OLT to the ONU which is obtained by ranging is added to obtain a propagation delay from the L2SW to the ONU. The obtained propagation delay from the L2SW to the ONU is added to the transmitted time stamp value whereby a time stamp value received at a base station or femtocell side becomes a time into which the propagation delay to the ONU is incorporated, and absolute values of clock timers can be synchronized with each other. The addition process can be realized by rewriting the time stamp value of the packet within the OLT or the ONU.

Communication system and time synchronization method

There is a need to recover an ONU from a sleep state for communication with the PON before a specified sleep cancel time in a short period of time without degrading the band use efficiency. An OLT manages an electric state of each ONU connected to a PON. When at least one ONU is in sleep mode, the OLT transmits a grant to allocate a band for a sleep cancel report to the ONU. When the sleep-mode ONU requires communication, the ONU transmits the sleep cancel report to the OLT using the band for the sleep cancel report. When receiving the sleep cancel report, the OLT changes the managed ONU to a normal state and resumes the communication with the PON.

Method of recovery from sleep state of an ONU in a PON system capable of power saving

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

A passive optical network system such that the power consumption can be reduced as much as possible according to the end-user traffic. An OLT uses the DBA function thereof and sequentially uses frequencies in ascending order of transmission rate in order to sequentially allocate bands to ONUs in ascending order of the requested bandwidth. At this time, a frequency to be allocated is selected so that the bandwidth allocated to each ONU is narrower than a maximum bandwidth through which transmission using the allocated wavelength is enabled. An OLT uses a grant area to specify the transmission timing of the secondary station and to inform the specified transmission timing to the secondary station. In addition, an area is set for storing information used to inform the secondary station of a new frequency to be used.

Optical multiplexing terminating device, passive optical network system and method for allocating wavelength

A master station includes an optical transmission interface for transmitting signals to a plurality of slave stations at a first transfer rate or a second transfer rate which is higher than the first one, packet buffers for accumulating the signals addressed to each of the plurality of slave stations, and a control unit for determining transmission timings and transfer rates of the signals on the basis of an amount of the signals accumulated in the packet buffers, transmitting the signals with the determined timings and rates, and notifying each of the slave stations about the determined timings and rates. Each of the slave stations includes an optical reception interface for receiving the signals of the first transfer rate or the second transfer rate, and a control unit for controlling the optical reception interface on the basis of the timings and rates which the slave stations is notified.

Passive optical network system and operation method thereof

In a light reception element such as an APD (Avalanche Photo Diode) used for receiving a high-speed and weak optical signal, it is possible to prevent the phenomenon of distortion of a signal inputted after a large-level light is received. A PON (Passive Optical Network) system includes an OLT (Optical Line Terminal) which can impartially and effectively transmit light reception data to each ONU (Optical Network Unit). According to a light reception amplitude received by each ONU, an inter-frame gap of an appropriate length is assigned for each ONU. The OLT includes a unit for measuring and accumulating the reception light amplitude and data on the inter-frame gap of an appropriate length decided in advance according to the characteristic of the light reception device and generates a grant value for assuring an inter-frame gap of an appropriate length by using the both information.

Apparatus of adjusting optical signal transmission timing

There are provided multiple candidates for FEC codes selectable for each of the ONTs. An OLT is provided with: means for storing redundancy and a code length of each FEC code in a table; means for selecting an FEC code; means for encoding or decoding data using the selected FEC code; means for calculating a bandwidth in consideration for the FEC redundancy and the code length with reference to the table during band assignment calculation; and means for notifying the destination ONT of the selected FEC code.

Optical access system

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.

Optical communication system

In order to be able to moderate the inclination of the PON burst reception characteristics and to improve the FEC effect, a first offset is used in a ranging window field, and a second offset, which is lower than the first offset value, is used in a burst data field other than the ranging window field.

Passive optical network system and optical line terminal

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Kokubunji, Japan

Tohru Kazawa