Nippon Telegraph and Telephone Corporation

Ntt Corporation

Rintaro Harada

Jun Terada

Shin Kaneko

Hirotaka Ujikawa

Hiroyuki Uzawa

Hirotaka Nakamura

Daisuke Hisano

Naotaka Shibata

Takeshi Imai

Junichi Kani

An optical transmitter () tracks a moving body () and irradiates the moving body () with a laser beam (). An optical receiver () is mounted on the moving body (), receives the laser beam (), and performs optical space communication with the optical transmitter (). The optical transmitter () extends an irradiation range () of the laser beam () into an elliptical shape.

Optical communication device and optical communication method

A spatial optical communication system in which a plurality of transmitters and a plurality of receivers opposite to each of the plurality of transmitters perform an optical communication in parallel, in which the plurality of transmitters transmit optical signals of same or adjacent wavelengths to the receivers of each opposite location, and has an interference blocking unit which is disposed between the transmitter and the receiver and spatially blocks an optical signal that interferes with the receiver of a non-opposite location among optical signals transmitted from the transmitter to the receiver of an opposite location. As a result, it is possible to avoid interference with other optical communications with a reduced space and at low cost, without need to supply power.

Spatial optical communication system

A wavelength multiplexing communication system includes a master station apparatus and a plurality of slave station apparatuses. The master station apparatus includes a wavelength multiplexing communication unit. The wavelength multiplexing communication unit performs wavelength multiplexing communication with the plurality of slave station apparatuses by using optical signals having the number of wavelengths equal to or less than the number of the plurality of slave station apparatuses. The slave station apparatus includes an optical communication unit. When the main signal communication is performed in the host slave station apparatus, the optical communication unit communicates with the master station apparatus by an optical signal having the same wavelength as a wavelength used by another slave station apparatus in which a main signal notification is not performed.

Wavelength multiplexing communication system and wavelength multiplexing communication method

The present invention enables shortening the time required for resuming communication in a protection method that uses a backup path in an optical communication system that includes a master station device and multiple slave station devices. The slave station devices are connected to a loop path in parallel. The communication paths between the master station device and the slave station devices include a normal path and a backup path. First and second slave station devices are slave station devices that cannot perform communication via the normal path. The magnitude relationship between backup path RTTs is opposite to the magnitude relationship between normal path RTTs. If the second normal path RTT for the second slave station device is longer than the first normal path RTT for the first slave station device, the first backup path RTT is longer than the second backup path RTT, and the second backup path RTT is shorter than the first backup path RTT. Based on this fact, the master station device limits the QuietWindow, which is used in ranging processing for measuring the backup path RTT, to a size smaller than a predetermined maximum size.

Optical communication system and master station

Time taken for resuming communication in a protection scheme using a backup path in an optical communication system including a master station device and a plurality of slave station devices is decreased. The plurality of slave station devices are connected in parallel to a looped path. A communication path between the master station device and each of the slave station device includes a normal path and a backup path. The master station device performs communication control processing for each of the slave station device based on RTT. A first slave station device is a slave station device with which communication through the normal path has become impossible. First backup path RTT of the first slave station device is calculated based on first normal path RTT of the first slave station device, first partial RTT between the master station device and the looped path, and loop propagation time necessary for one trip through the looped path. The communication control processing for the first slave station device is resumed based on the calculated first backup path RTT without measurement of the first backup path RTT when the first slave station device is sensed.

Optical communication system, master station, and optical communication method

The present invention enables shortening the time required for resuming communication in a protection method that uses a backup path in an optical communication system that includes a master station device and multiple slave station devices. The slave station devices are connected to a loop path in parallel. The communication paths between the master station device and the slave station devices include a normal path and a backup path. The master station device executes communication control processing with respect to the slave station devices based on the RTTs. A first slave station device is a slave station device that cannot perform communication via the normal path. If the first slave station device is detected, the master station device calculates a first backup path for the first slave station device based on a first RTT between the master station device and the loop path, a loop RTT required for one full lap on the loop path, and the first normal path RTT for the first slave station device. The master station device then resumes communication control processing for the first slave station device based on the calculated first backup path RTT.

A wavelength multiplexing communication system includes a master station apparatus and a plurality of slave station apparatuses. The master station apparatus includes a wavelength multiplexing communication unit that performs wavelength multiplexing communication with the plurality of slave station apparatuses by wavelengths the number of which is equal to or less than the number of the plurality of slave station apparatuses using an optical signal of a wavelength in a first wavelength group and an optical signal of a wavelength in a second wavelength group. The slave station apparatuses include an optical communication unit that performs communication of the main signal with the master station apparatus by an optical signal of a wavelength in the first wavelength group, which is different from a wavelength in the first wavelength group used by another slave station when the main signal communication is performed in the host slave station apparatus, and performs communication of a signal other than the main signal with the master station apparatus by an optical signal of a wavelength in the second wavelength group, which is a wavelength same as a wavelength used by another slave station apparatus when the main signal communication is not performed in the host slave station apparatus.

In an optical communication system, an optical communication device and a plurality of optical transmission devices are loop-connected via transmission line. An optical signal transmission unit of the optical communication device, when no communication interruption occurs in the transmission line, outputs an optical signal addressed to a communication destination device that communicates with the own device to a transmission line connected to either one of two neighboring optical transmission devices. The optical signal transmission unit outputs, at the time of communication interruption occurring in the transmission line, an optical signal addressed to the communication destination device to both of transmission lines connected to respective two neighboring optical transmission devices. A branch unit of the optical transmission device branches the optical signal input from a neighboring device, and outputs branched optical signals to another neighboring device and a subordinate communication destination device of the own device.

Optical communication system, optical communication apparatus and optical communication method

A transfer device installed between a host device and a plurality of OLTs in a communication system to which a network with a PON configuration including the plurality of OLTs between the host device and a subordinate device is applied, the transfer device including a frame information acquisition unit configured to monitor downstream frames input from the host device and calculate a statistical value of the downstream frames per a predetermined fixed cycle, a frame storage unit including a plurality of queues each configured to store downstream frames to be transferred to the plurality of OLTs, the frame storage unit configured to store the downstream frames input from the host device, a frame sorting unit configured to input the downstream frames to the plurality of queues in the frame storage unit, and a distribution control determination unit configured to determine the number of frames to be sequentially input by the frame sort unit to the plurality of queues based on the statistical value.

Downstream frame transfer device, transfer method, and transfer program

The present invention enables shortening the time required for resuming communication in a protection method that uses a backup path in an optical communication system that includes a master station device and multiple slave station devices. The slave station devices are connected to a loop path in parallel. The communication paths between the master station device and the slave station devices include a normal path and a backup path. The master station device executes communication control processing with respect to the slave station devices based on the RTTs. A first slave station device is one of the slave station devices, and a second slave station device is a slave station device that cannot perform communication via the normal path. If a second slave station device is detected, the master station device calculates a second backup path RTT for the second slave station device based on the first normal path RTT and the first backup path RTT for the first slave station device and a second normal path RTT for the second slave station device. The master station device then resumes communication control processing for the second slave station device based on the calculated second backup path RTT.

A transfer device includes: a frame information acquisition unit configured to monitor downstream frames between host devices and OLTs and calculate a statistical value of the downstream frames per a fixed cycle; a frame storage unit configured to store the downstream frames in a plurality of queues; a frame sorting unit configured to input the downstream frames to the queues; and a distribution control unit configured to determine the number of frames to be sequentially input to the queues and increase the number of distributed frames of at least one of the host devices input to an OLT, the OLT having a smaller value of a total number of frames input from all the host devices than a maximum number of rounded frames obtained by dividing a value of a total number of frames input until the frames of all the host devices take turns around the plurality of queues by the number of OLTs. As a result, a delay requirement can be satisfied while a memory size of the queue and power consumption required for the frame sorting process are reduced.

Downstream frame transfer device, transfer method and transfer program

A transfer apparatus include a distribution unit, a storage unit, and a transfer unit, in which the distribution unit is configured to identify a plurality of networks to which frames belong, distribute the frames for each of the networks based on an identification result, and store the distributed frames in the storage unit, the storage unit is configured to store information of a time at which a frame of the frames is stored in the storage unit and the frame in association with each other, and the transfer unit is configured to detect a period of time for which the frame stays in the storage unit, detect a remaining period to send which is a remaining time of a time for which the frame is permitted to stay in the storage unit, for each of the frames, based on a difference between the time for which the frame stays in the storage unit and the delay upper limit value, and output the frame to a predetermined apparatus based on the remaining period to send.

Transfer apparatus, transfer method, and transfer program

A bandwidth allocation apparatus includes a request information acquisition unit configured to acquire request information indicating a required amount for a bandwidth allocation by using a communication link separated from a data link used in data communication, a determination unit configured to determine, on the basis of the request information, whether the bandwidth allocation that allows transmission of data within the designated time, to a termination apparatus is possible, and a bandwidth-allocation amount definition unit configured to, in a case where the bandwidth allocation to the termination apparatus is determined not to be possible, specify some termination apparatuses to which the bandwidth allocation that allows transmission of data within the designated time, is possible, define a bandwidth allocation amount for a specified termination apparatus, and allocate the defined bandwidth allocation amount to the specified termination apparatus.

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Musashino, Japan

Rintaro Harada