Hitachi, Ltd.

Hitachi Communication Technologies, Ltd.

Masaki Ohira

Yusuke Yajima

Tohru Kazawa

Takashi Mori

Norihiro Sakamoto

Yukio Nakano

Toshiki Sugawara

Akihiko Tsuchiya

Masahiro Takatori

Yoshinobu Morita

Koji Kato

Masatoshi Shibasaki

Mitsunobu Kimura

Masazumi Noguchi

Taro Tonoduka

Yuichi Yamaguchi

Hirohisa Sano

Makoto Suzuki

Hiroaki Inoue

Ryuji Ishii

Tatsuo Kanetake

Hideaki Takano

Toshiyuki Atsumi

Toru Okamoto

Tomohiro Mori

Kentarou Watanabe

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

There is provided an encryption apparatus including an idle data inserting unit that takes input of a frame including a fixed-length header and a variable-length payload and an encrypting unit that receives an output of the idle data inserting unit. If the length of a block to be processed, included in the payload, is less than a predetermined value, the idle data inserting unit appends idle data following the block and transmits the frame including the block padded with the idle data to the encrypting unit.

Encryption apparatus

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

There are provided an optical line terminal and an optical network terminal, which can process with the same forward error correction code even if an EFC frame size of G-PON descending signals is different between two types of 255 and 120. The optical network terminal includes a photoelectric converter, a PON transceiver, and a physical layer. The PON transceiver includes an error correction code encoder including a shortening compensation parameter table and a shortening compensation calculator for calculating compensated data by referring to the shortening compensation parameter table. Also the optical line terminal includes a photoelectric converter, a PON transceiver, and a physical layer. The optical line terminal includes an error correction code encoder including a shortening compensation parameter table and a shortening compensation calculator for calculating compensated data by referring to the shortening compensation parameter table.

Optical line terminal and optical network terminal

The optical line terminal has a PON transceiver including an error correction code decoder. The error correction decoder includes: a shortening compensation parameter table; and a syndrome calculator for calculating a syndrome by referring to the shortening compensation parameter table, or an error search part for calculating an error position or an error value by referring to the shortening compensation parameter table. Also the optical network terminal has a PON transceiver including an error correction code decoder. The error code decoder includes: a shortening compensation parameter table; and a syndrome calculator for calculating a syndrome by referring to the shortening compensation parameter table, or an error search part for calculating an error position or an error value by referring to the shortening compensation parameter table.

A station-side communication device connected to subscriber-side communication devices via an optical combining device; sending, to the subscriber-side communication devices, a distance measurement request signal; computing transmission delay times of optical signals from the individual subscriber-side communication devices by receiving distance measurement signals, and including: a threshold control part identifying the level of distance measurement signals; a signal detection part detecting breaks in the distance measurement signals from the threshold control part; a transmission granting part determining the timing at which transmission of optical signals is granted, and a reset timing generation part that, there is notification of detection of a break in the distance measurement signal from the signal detection part while it is being notified that distance measurement is carried out to and from the subscriber-side communication devices from the transmission granting part, sends a reset signal indicating that the voltage level is reset to the threshold control part.

Passive optical network system and ranging system thereof

A Passive Optical Network system implementing a parent station capable of receiving high-speed burst signals transmitted from a plurality of subsidiary stations to a parent station, with excellent bandwidth utilization efficiency in the link from the stations to the parent. The system is provided with a configuration in which, when launched or an addition of a new subsidiary station, the parent stores threshold values appropriate for the received signals on the basis of the strength of the received signal for each subsidiary station, from among a plurality of preset threshold value candidates, and in response to the parent station's sending of a transmission grant with respect to each subsidiary station each time the subsidiary station transmitting optical signals changes, the stored threshold value corresponding to the subsidiary station is set in the receiver circuit.

Passive optical network system and operating method thereof

A client signal having a constant bit rate is segmented every a bytes to create code information blocks. The bit rate of the client signal is increased such that the client signal has the code information block and an empty area comprised of b bytes, and the ratio c/a is equal to or higher than 110% to create a code blockcomprised of c bytes. The code information block in the code block is encoded such that an error correcting code is included therein to have an encoding gain of 6 dB or higher for a bit error ratio of 10. Associated check bits are placed in the empty area to eventually generate a super FEC signal.

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Yokohama, Japan

Masaki Ohira