Nippon Telegraph and Telephone Corporation

Matsushita Electric Industrial Co., Ltd.

Katsumi Iwatsuki

Mitsuhiro Teshima

Masamichi Fujiwara

Noboru Takachio

Shingo Kawai

Jun-ichi Kani

Koji Akimoto

Hiroo Suzuki

Junichi Kani

Kenichi Suzuki

Naoto Yoshimoto

Hitoshi Obara

Masaru Fuse

Kiyoshi Matsumoto

Kuniaki Utsumi

Takashi Yamada

Hirotaka Nakamura

Yoshikazu Ishii

Shigeru Kuwano

Katsuhiro Araya

Masatoshi Saruwatari

Hiroaki Asano

Toru Shiozaki

Hideo Kawata

Shigendo Nishi

Ken-ichi Suzuki

Hidetaka Onishi

Hitoshi Uematsu

Masaki Fukui

Toru Ogawa

Hideo Kawada

Ukyo Yamaguchi

Jun-Ichi Kani

According to the present invention, a star-type wavelength multiplexed communication network using optical TX/RX devices capable of assigning the wavelengths can be provided without using the monitoring light. In an embodiment of the present invention, an optical TX/RX device for transmitting and receiving a wavelength-multiplexed signal light comprises an optical receiver capable of varying the RX wavelength and an optical transmitter capable of varying the TX wavelength. The optical TX/RX device detects RX wavelengths not in use via the optical receiver, and assigns the RX wavelength of the optical receiver to one of the RX wavelengths not-in-use, and assigns the TX wavelength of the optical transmitter to a TX wavelength corresponding to the RX wavelength according to a correspondence table of TX and RX wavelengths in the memory. Then, the optical TX/RX device transmits a signal light on this TX wavelength, and detects the response on the RX wavelength. If the response is detected, communication is initiated using the assigned TX wavelength and the RX wavelength. If the response is not detected, the operation is repeated from the detection of RX wavelengths not in use to the transmission of the signal light on TX wavelength again.

Optical wavelength multiplexing access system

In the present invention, the extremely complicated setting and control and an extremely expensive optical component (wavelength locker) are not required, and optical output wavelength and optical output power can simply be set and controlled at a moderate price. At least one value for determining a dependence of the optical output wavelength on drive current and device temperature and at least one value for determining a dependence of the optical output power on drive current and device temperature in a light emitting device constituting first meansfor emitting light are stored in fourth means. Fifth meansdetermines drive current or optical output power c and device temperature d, at which both the optical output wavelength and optical output power of the light emitting device are separately specified value b, from a relationship among the drive current, device temperature, and optical output wavelength of the light emitting device, the relationship being determined by the at least one value, and a relationship among the drive current, device temperature, and optical output power, the relationship being determined by the at least one value, and the fifth meansgives the drive current or optical output power c and device temperature d as target values to second meansand third means

Optical communication light source unit and wavelength monitoring control method

A dual structure for a multiplexing section extended to an OSU is obtained without adding a dynamic function, such as an optical switch, to a W-MULDEM. The W-MULDEM of an optical wavelength division multiplexing access system divides, among ports corresponding to the individual ONUs, downstream optical signals having wavelengths &#x3bb;dto &#x3bb;dn, which are received along a current-use optical fiber, or downstream optical signals having wavelengths &#x3bb;d+&#x394;&#x3bb; to &#x3bb;dn+&#x394;&#x3bb;, which are received along a redundant optical fiber. The W-MULDEM also multiplexes, for the port that corresponds to the current-use optical fiber or the redundant optical fiber, upstream optical signals having wavelengths &#x3bb;uto &#x3bb;un or wavelengths &#x3bb;u+&#x394;&#x3bb; to &#x3bb;un+&#x394;&#x3bb;, which are received along optical fibers corresponding to the ONUs. A wavelength difference between the downstream optical signal and the upstream optical signal that are consonant with each ONU is defined as an integer times the FSR of an AWG.

Optical wavelength division multiplexing access system

An optical modulation apparatus is provided which implements a stable amplifying function by reducing the effect of reflected light rays from end faces of a bidirectional optical amplifier by imposing a numerical limitation on the relationship between the gain of the bidirectional optical amplifier and the loss of the optical modulator, or by inserting a polarization rotation section in a reflection type optical modulator including the bidirectional optical amplifier or in a multi-wavelength collective optical modulation system combining the multiple optical modulators. An optical modulation apparatus is provided which implements a stable amplifying function and cost reduction by reducing the effect of reflected light rays by interposing optical isolators at every alternate SOAs in a transmission-type optical modulation apparatus including a plurality of semiconductor optical amplifiers (SOAs) connected in a multistage fashion.

Optical modulation apparatus

The present invention provides wavelength monitoring and/or control enabling size reduction and low power operation without requiring a complicated optical system in its wavelength monitoring and controlling mechanism. The measurement portion () measures temperature by a thermistor () in the measurement portion, and measures a bias current by using an LD drive current detecting circuit (). The LD temperature, optical output and bias current are measured by the measurement portion. The relationship between the LD temperature and wavelengths or between the temperature, bias current and wavelengths is stored in a memory map of the storage portion (). The central controlling portion () calculates wavelengths on the basis of the temperature and the bias current or the temperature information of the measurement portion, and the relationship between the LD temperature, bias current and wavelengths or between the temperature and wavelengths of the storage portion.

Optical module and method for monitoring and controlling wavelengths

An optical wavelength division multiplexing network has a multi-level structure where a plurality of optical network units (ONUs) are connected to a lowest-level network. A node apparatus connected to networks other than the lowest-level network includes (a) passive optical components to branch optical signals from a higher-level network to a lower-level network, and couple optical signals from the lower-level network to the higher-level network, and (b) optical amplifiers for the optical signals. A node apparatus connected to the lowest-level network includes (a) an optical multiplexer/de-multiplexer to de-multiplex optical signals from the higher-level network, selectively output an optical signal to each ONU, and multiplex wave-length specific optical signals from the ONUs into a multiplexed optical signal, and (b) optical amplifiers for the optical signals. The node apparatuses provide an optical communication path between the higher-level network and the lower-level (or lowest-level) network without converting the optical signals into electrical signals.

Node apparatus, optical wavelength division multiplexing network, and system switching method

The present invention provides an optical wavelength-division multiple access system and a corresponding optical network unit. A wavelength band Da (wavelengths &#x3bb;dto &#x3bb;dn) for downlink optical signals corresponding to the n ONUs, a wavelength band Ua (wavelengths &#x3bb;uto &#x3bb;un) for uplink optical signals corresponding to the n ONUs, a wavelength band Db (wavelengths &#x3bb;dn+1 to &#x3bb;dn+m) for downlink optical signals corresponding to the m ONUs, and a wavelength band Ub (wavelengths &#x3bb;un+1 to &#x3bb;un+m) for uplink optical signals corresponding to the m ONUs are set different from one another, the wavelength bands Ua and Ub are set adjacent to each other, and the wavelength bands Ua and Da or the wavelength bands Ub and Db are set adjacent to each other. Each of the ONUs has downlink optical signal receiving unit for receiving a downlink optical signal of one of the wavelengths &#x3bb;dto &#x3bb;dn+m in the wavelength bands Da and Db which wavelength is assigned to the ONU, and uplink optical signal receiving unit for receiving an uplink optical signal of one of the wavelengths &#x3bb;uto &#x3bb;un+m in the wavelength bands Ua and Ub which wavelength is assigned to the ONU or an uplink optical signal within a broad band including the wavelength bands Ua and Ub.

Optical wavelength-division multiple access system and optical network unit

An optical modulation apparatus is provided which implements a stable amplifying function by reducing the effect of reflected light rays form end faces of a bidirectional optical amplifier by imposing a numerical limitation on the relationship between the gain of the bidirectional optical amplifier and the loss of the optical modulator, or by inserting a polarization rotation section in a reflection type optical modulator including the bidirectional optical amplifier or in a multi-wavelength collective optical modulation system combining the multiple optical modulators. An optical modulation apparatus is provided which implements a stable amplifying function and cost reduction by reducing the effect of reflected light rays by interposing optical isolators at every alternate SOAs in a transmission-type optical modulation apparatus including a plurality of semiconductor optical amplifiers (SOAs) connected in a multistage fashion.

Optical modulating device

A first optical fiber transmission path is used to transmit continuous-wave light for upstream signal light from the center node to each of the remote nodes, while a second optical fiber transmission path is used to transmit downstream signal light from the center node to each remote node and to transmit upstream signal light (obtained by modulating continuous-wave light) from each remote node to the center node. In this network, specific wavelength bandwidths are allocated to each remote node for the continuous-wave lights (for upstream signal lights) and the downstream signal lights, and the wavelength bandwidths for the continuous-wave lights (for upstream signal lights) and the downstream signal lights are alternately set.

Ring network using multi-wavelength generator

In an optical wavelength division multiplexed access system, a center unit (OSU) and n optical network units (ONUs) are connected together via a wavelength splitter and optical fiber transmission lines, and downstream optical signals from the OSU to the ONUs and upstream optical signals from the ONUs to the OSU are transmitted in both directions, the wavelength spacing &#x394;&#x3bb;d (optical frequency spacing &#x394;fd) of the downstream optical signals is set to twice or more the wavelength spacing &#x394;&#x3bb;u (optical frequency spacing &#x394;fu) of the upstream optical signals, each ONU transmits an upstream optical signal whose optical spectral width is twice or more &#x394;&#x3bb;u (&#x394;fu), and the wavelength splitter spectrum slices the upstream signals transmitted from the ONUs into wavelengths (optical frequencies) whose optical spectral widths are mutually different within &#x394;&#x3bb;u (&#x394;fu), and wavelength-division multiplexes them and transmits to the OSU.

Optical network unit, wavelength splitter, and optical wavelength-division multiplexing access system

An optical wavelength division multiplexing network which can carry out large-capacity access service with a simple constitution is provided. In an optical network comprising a plurality of layers, a highest level network comprises a ring network having a center node and remote nodes; an intermediate level network comprises a ring centered around a node belonging to the higher level network, and a lowest level network comprises a star network centered around an access node which multiplexes traffic from a plurality of ONU, the ONU and the access node being directly joined together by optical fibers; the center node belonging to the highest level network and the ONU establish a direct communication path by using lights of different wavelengths; at nodes provided therebetween, the optical signals are not electrically processed but are amplified, branched, and routed.

Cost-reduction in an optical communication unit is achieved by using spectrum-sliced modulated broadband light for transmitting upstream signals, instead of using laser light. An optical communication system includes at least one pair of optical communication units that each has a bi-directional network interface in which physical bit rates of transmission signals and reception signals are identical, an optical transmitter, and an optical receiver, and that performs bi-directional transmissions via at least one optical fiber. One optical communication unit includes a physical bit rate down-converter that lowers the physical bit rate of transmission signals from the bi-directional network interface and outputs to the optical transmitter, and the other optical communication unit includes a physical bit rate up-converter that raises the physical bit rate of signals received by the optical receiver and outputs to the bi-directional network interface. These optical communication units are also applicable to wavelength-division multiplexing systems.

Optical communication system, optical communication unit, and optical transceiving package

Multi-wavelength light having a frequency band equal to or greater than the FSR of an AWG is demultiplexed into individual wavelength channels, and power level deviations between wavelength channels are suppressed. An optical demultiplexer includes a wavelength-group demultiplexer that demultiplexes multi-wavelength light into wavelength groups formed from wavelength channels, and channel demultiplexers that demultiplex each wavelength group into wavelength channels light. An optical multiplexer includes channel multiplexers that multiplex modulated signal light of each wavelength channel for each wavelength group, and a wavelength-group multiplexer that multiplexes, for each wavelength group, WDM signal light output from the channel multiplexers. The FSR of the wavelength-group multiplexer/demultiplexer is set to be equal to or greater than the frequency band of the multi-wavelength light. The channel multiplexer/demultiplexer is an AWG in which the FSR is approximately the full width at half maximum of the transmission characteristics of each port of the wavelength-group multiplexer/demultiplexer.

Multi-wavelength optical modulation circuit and wavelength-division multiplexed optical signal transmitter

To generate light with the degree of polarization zeroed and the spread of an optical spectrum suppressed even with temporal overlapping between optical pulses each of which is polarized orthogonally to the succeeding pulse, a polarization scrambler includes an optical pulse generator that generates optical pulses with an intensity waveform repetition period T/2 and an electrical field repetition period T in which the same intensity waveform is repeated every repetition period T/2 and in which phase is inverted every repetition period T/2, and an orthogonal polarization delay unit which receives each of the optical pulses, separates the optical pulse into two optical pulses with orthogonal states of polarization, and relatively shifts the temporal position of one of the two optical pulses from that of the other optical pulse by (2n&#x2212;1)T/4 (n is a natural number) to generate light in which each pulse is polarized orthogonally to a succeeding pulse.

Polarization scrambler and optical network using the same

This invention discloses an optical burst transmission system in which an optical generator generates Type 1 lightwaves having different wavelengths corresponding to transmission lines and having undergone intensity modulation with obtained data; a broad spectrum optical generator generates, by incorporating Type 2 lightwaves, a Type 3 lightwave using a fewer light emitting devices than the number of the Type 1 lightwaves, each Type 2 lightwaves having a corresponding wavelength apart from Type 1 lightwave's wavelength with an FSR interval and having undergone the intensity modulation with clock signals; an optical multiplexer multiplexes the Type 1 and Type 3 lightwaves to output the combination to each transmission line; and an optical routing unit extracts, from the combination, pairs of one Type 1 lightwave and one Type 2 lightwave having the corresponding wavelength, and guides pairs to each transmission line corresponding to the Type 1 lightwave's wavelength in each pair.

Growing community of inventors

Yokohama, Japan

Katsumi Iwatsuki