Nippon Telegraph and Telephone Corporation

Nippon Telegraph & Telephone Corporation of Japan

Noriki Miki

Kiyomi Kumozaki

Manabu Yoshino

Noriyuki Oota

Osamu Yoshihara

Daisuke Murayama

Kenji Okada

Tomohiro Taniguchi

Shin Kaneko

Noriyuki Ota

Ryuichi Watanabe

Nobuyuki Tokura

Akihiro Otaka

Seiichi Yamano

Norio Tamaki

Yasuyuki Okumura

Fumio Mano

Yoshihiro Takigawa

Shinichi Aoyagi

An optical line terminal calculates a requirement threshold for each optical subscriber unit based on a difference between the time average allocated bandwidth of each optical subscriber unit and the target bandwidth, and notifies a corresponding optical subscriber unit of the calculated requirement threshold. The corresponding optical subscriber unit then notifies, based on the data amount accumulated in a buffer, the optical line terminal of a data amount, as a transmission requirement, up to a data separation that is less or equal to the notified requirement threshold and in which a maximum transmission amount can be transmitted. The optical line terminal then notifies the corresponding optical subscriber unit of a transmission permission amount in which the data equal to the transmission requirement of which the optical line terminal is notified can be transmitted. The corresponding optical subscriber unit then transmits the data amount corresponding to the transmission permission amount.

Bandwidth allocation method and passive optical network system

An optical code communication system comprises an optical transmitter, an optical receiver, and an optical transmission line. The optical receiver has an optical mixing decoder for mixing a coded light and a local light, dividing the mixed light into an object optical frequency and a non-object optical frequency, and outputting the lights and a detection adder-subtractor filter for detecting the object optical frequency and the non-object optical frequency, filtering the intermediate frequency signals, subtracting one of the intermediate frequency signal from the other, and outputting the resultant intermediate frequency signal. The coded light and the local light are coherent with each other between the optical frequency chips constituting the coded light when detected. The optical mixing decoder or detection adder-subtractor filter regulates the phase of the intermediate frequency signal within the passband when filtered so that the output value or the absolute value of the intermediate frequency signal within the passband when filtered is different when the optical receiver receives a coded light modulated with a different value of the transmission data.

Optical code communication system

The aim of the present invention is to achieve a low delay and high bandwidth efficiency in an upstream bandwidth and to accurately reflect assured bandwidth in an actual transmitted bandwidth. To achieve this, in the present invention the maximum value and the transmission cycle of a requested bandwidth are set for each service class. The present invention allocates bandwidth to a service path terminating section based on excess allocated bandwidth and requested bandwidth of each service path terminating section. For each service path terminating section the present invention also selects one bandwidth out of a plurality of bandwidths requested by a service path terminating section in such a manner that the sum value of the allocated bandwidths of the plurality of service path terminating sections is within a predetermined range.

Dynamic bandwidth allocation circuit, dynamic bandwidth allocation method, optical network unit, PON system, dynamic bandwidth allocation program and recording medium

The invention dispenses with calibration of the optical frequency of the light source and permits the use of many codes without increasing the transmission bandwidth used. Let the optical frequency width of the light source be represented by FSR and the code length of every code be represented by FSR, the codes are made to be orthogonal to each other. The optical intensity-frequency characteristic of an n-th optical code signal is set to Cn(f)=(1+cos(2&#x3c0;sf/FSR+r&#x3c0;/2))/2 (where s is an integer in the range from 1 to maximum number of codes/2, and r=0 or 1) to provide orthogonality between the optical code signals. Alternatively, optical frequency chips are sequentially assigned to chip sequences forming the optical code signals, the optical frequency of each chip '1' is output, and a filter is provided with an optical filtering characteristic of a concatenated code which is a repeated continuation of, for example a second-order Hadamard code word (0101) or (0011), and light emitted from the light source is passed through the filter to form the optical code signal. An encoding optical frequency regionand a decoding optical frequency regionare so chosen as to cover a range of drift of the source frequency. In FIG., &#x394;Fand &#x394;Findicate drifts of the source frequency.

Optical communication system using optical frequency code, optical transmission device and optical reception device thereof, and reflection type optical communication device

In a P2MP system in which upstream bandwidth is shared by a plurality of ONUs, a dynamic bandwidth allocation circuit is provided which reduces the consumption of memory capacity, and avoids the divergence of parameters. A dynamic bandwidth allocation circuit provided in an optical line terminal (OLT) calculates, for each cycle and for each ONU, a target data size (target) which constitutes a target for allocated data size (allocated). Furthermore, taking the time constant of an exponential weighted moving average as &#x3c4;, and taking &#x3b1;=(&#x3c4;&#x2212;1)/(&#x3c4;+1), an ideal allocated data size (ideal) is calculated by ideal=target&#x2212;(&#x3b1;/(1&#x2212;&#x3b1;))&#xb7;excess. Furthermore, an excess allocated data size (excess) per one cycle is calculated by excess=&#x3b1;&#xb7;excess+(1&#x2212;&#x3b1;)&#xb7;(allocated&#x2212;target). If ideal&#x3c;0, the condition that bandwidth allocation is not granted is used for bandwidth allocation.

Dynamic band allocation circuit, dynamic band allocation method, dynamic band allocation program, and recording medium

A bandwidth allocation method used in a point-to-multipoint communication system, for efficiently using the bandwidth while shortening delay time. A central unit quantizes round-trip propagation delay times of subsidiary units, groups the subsidiary units, assigns the same quantized round-trip delay time to the same group, and allocates allocation request signal bandwidths to the subsidiary units of the same group when receiving allocation requests within a predetermined period. Based on the quantized round-trip delay time, the bandwidths are located as close as possible while the bandwidths do not temporally overlap with each other and as temporally ahead as possible. Data signal bandwidths are also allocated to the subsidiary units of the same group, based on the quantized round-trip delay time and requested amounts of data, in a manner such that the bandwidths are located as temporally ahead as possible but temporally behind in comparison with the allocation request signal bandwidths.

Bandwidth allocation method in point-to-multipoint communication system

A packet multiplexing apparatus is presented for multiplexing packets to be transmitted from a number of user facilities to a local service node in such a way to assure equal access to the output port for all the users. The apparatus is provided with input ports for inputting a packet in a respective input port; a buffer memory provided for each input port for temporary storage of a packet; an output signal transmission circuit for retrieving a packet from each buffer memory in a specific sequence; an output port for transmitting packets output from the output signal transmission circuit; and a retrieval sequencing section for controlling the specific sequence by changing a retrieving order of packets from buffer memories for each complete round of packet retrieval so that a frequency of the retrieving order for each input port is uniformly shared by the input ports.

Packet multiplexing apparatus

The present invention provides a subscriber registration and authentication method which secures high safety and by which necessary circuit scale is small. In the method of the present invention, each network termination unit has a peculiar secret information item for identifying it and an encrypted information item obtained from the secret information item with a public key determined by the network manager; the operation system decrypts the encrypted information item stored in the network termination unit which will be registered with a secret key determined by the network manager, and registers this termination unit for the local service unit by writing the encrypted and decrypted information items into the service unit; at the beginning of providing the service, the local service unit calls the network termination unit as a communication partner by sending the encrypted information item which is peculiar for the termination unit; the called network termination unit compares the received encrypted information item with that of its own, and if these agree with each other, responds to the local service unit by using the secret information item of its own; and the local service unit confirms that the network termination unit has been regularly registered by collating the received information item with the information item of its own.

Subscriber registration and authentication method

The present invention provides an optical time compression multiplexing transmission system which suppresses the influence of optical reflection by a simple configuration without degrading transmission efficiency. The present invention is a 1:n (n being a natural number) time division multiplexing point-to-multi-point optical time compression multiplexing transmission system which comprises a decision element for determining whether or not the receiving signal which is outputted from a receiving element is a regular signal, an initialization element for initializing the operation condition of the receiving element when a receiving signal is determined to not be a regular signal by the decision element. When a signal is determined to not be a regular signal by the decision element, because the initialization element initializes the operation condition of the receiving element, the abnormal operation of the receiving element which is abnormal due to optical reflection which occurs by reflection can be returned to normal operation in a minimum amount of time.

Optical time compression multiplexing transmission system

A point-to-multipoint communication system is presented to enable a reliable, high quality communication using multiplexed optical signals between a central office equipment and a plurality of subscriber's equipment. The system is provided with a plurality of office transceivers in the central office equipment, and the each of the subscribers is provided with at least one subscriber transceiver. The system is designed so that a redundancy system is built-in by providing one of either the office transceivers, a plurality of subscriber's transceivers or the optical connection device, to connect the two sets of transceivers at all times. One of these redundancy systems provides an operating connection between each of the office transmitters which are connected to the office transceivers and each of the subscriber transmitters which are connected to the subscriber transceivers. Therefore, when a malfunction occurs somewhere in the optical network, the least number of the malfunctioning components need to be switched over the the normally functioning system to maintain continued communication services. The present communication system is designed with the least number of active components, therefore, the failure probability is significantly decreased, and repairs if necessary can be preformed quickly. The overall effect of the present system is that interactive point-to-multipoint communication services of high quality and reliability are provided at reasonable cost.

Point-to-multipoint optical transmission system

In a secure transmission system in which first and second pieces of communication equipment are interconnected via a transmission line, the first communication equipment has a conversion part for encrypting an information signal to be transmitted, through utilization of a received signal and the second communication equipment has an information memory for storing, as a key information, information to be transmitted to the first communication equipment and an inverse conversion part in which the encrypted signal received from the first communication equipment is decoded using the key information read out of the information memory. As the transmission information signal varies, the key information also varies accordingly. Hence, a highly secure transmission system and secure communication equipment can be realized.

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Yokohama, Japan

Noriki Miki