Fujitsu Corporation

Junichi Ishiwatari

Masahiro Shinbashi

Akihiko Oka

Yukio Yamazaki

Takashi Kuwabara

Masahiro Shioda

Atsuki Taniguchi

Kazuo Takatsu

Hideaki Mochizuki

Nobuyuki Nemoto

Hideo Sunaga

Tsuyoshi Morishita

Dai Hagimura

Takatoshi Nakamura

Masaru Kameda

Koji Iwamoto

Masaki Kubo

Shigeyuki Kobayashi

Shuniti Nakayama

An optical transmission apparatus in which the reliability and quality of optical performance monitoring are improved. A light output unit selects and outputs light of one of a plurality of wavelengths. A digital information conversion unit converts a performance parameter for the light to digital information. A conversion map management unit manages a conversion map including a conversion format for converting the digital information indicative of values which vary according to the wavelengths of light with the same output power so that reference values at normal operation time for all the wavelengths will be the same and used for converting the digital information to a monitored value. A display control unit exercises control over the displaying of the monitored value corresponding to the digital information.

Optical transmission apparatus monitoring optical performance

In an error correcting method and an apparatus therefor using Hamming codes, a frame regulated by a synchronous network is divided into L blocks in the direction of row. Preferably, information bits and check bits are allocated to a payload portion and non-defined bits of an LOH portion, respectively. More preferably, the information bits and the check bits are divided into M sub blocks to form a Hamming code block. In addition, a code error correcting means rearrange each Hamming code block per bit and further preferable, a syndrome register with a plurality of banks operates an error syndrome of the Hamming code block, and based on the operation result, the code error correction of the Hamming code block is performed by a bank switchover.

Error correcting method and apparatus

A signal quality monitoring device includes alarm producing/canceling sections for first and second grade, and an alarm holding section for, when a grade of low quality of the current signal shifts from one to the other grades and the corresponding alarm producing/canceling section discriminates that the current signal is in the other grade of low quality, holding the continuous output of the one alarm regardless of the cancellation by the one alarm producing/canceling section, until the other alarm producing/canceling section produces the continuous output of the corresponding other alarm as a consequence of expiration of the corresponding producing time period. Therefore, no-alarm states, caused by frequently shifting of low quality among plural grades in accordance with lengths of a producing time period and a canceling time period set for each grade of low quality, can be avoided.

Signal transmitter and signal quality monitoring device

An error correction method and a transmission apparatus used in a transmission using a frame including a header and a payload are provided. In the error correction method and the transmission apparatus, a pseudo error is inserted in check bits of the frame to be transmitted. Thus, an error-correcting function of a transmitter and a receiver can be easily tested. A mismatch of a state of validation or invalidation of the error-correcting function between the transmitter and the receiver can be avoided without affecting a main signal by inserting information on whether or not an error correction is performed in an unused area of the header in the transmitter.

Error correction method and transmission apparatus

An alarm detection apparatus includes a plurality of alarm detectors detecting and/or cancelling alarms for identical and different error rates. The plurality of alarm detectors are grouped into a major detector unit made up of alarm detectors which detect major error rates, and a minor detector unit made up of alarm detectors which detect minor error rates. The major detector unit and the minor detector unit output detection outputs corresponding to specified detection rates thereof. A predetermined alarm detector corresponding to a part of the minor detector unit has a specified detection rate overlapping a specified detection rate of the major detector unit being controlled, so that a detection function or a detection output of the predetermined alarm detector is disabled.

Alarm detection apparatus

A transmission device includes a channel allocation part which groups channels defined on a transmission line into groups and allocate, for each of the groups, the channels in one of predetermined transmission modes which can be defined on a dual link formation of a network to which the transmission device can be connected.

Transmission device and system having the same

An add-drop multiplexer contains a partial drop unit and a partial add unit. The partial drop unit selects a number n of first signal(s) of n channel(s) among a number N of first signals of N channels, which are received from a first transmission line, and transmits the n first signal(s) of n channel(s) on at least one second transmission line, where N and n are integers satisfying N&gt;n&gt;0. The partial add unit receives n second signal(s) of n channel(s) from at least one third transmission line, and a number (N-n) of first signal(s) of (N-n) channel(s) among the N first signals of the N channels, which are not selected by the partial drop unit, and transmits on the first transmission line the n second signal(s) of n channel(s) and the (N-n) first signal(s) of (N-n) channel(s) as N third signals of N channels.

Add-drop multiplexer with enhancement of accessibility to signals in

A wait-to-restore section corresponding to a first channel has a selector for switching an output side under the control of a mode setting section, and a timer which is reset at the time of mode change. The selector of the wait-to-restore section corresponding to the first channel supplies its output only to a path switch corresponding to the first channel in STS-1 mode and commonly supplies the output to path switches corresponding to the first to third channels. The mode setting section supplies selector change signals to respective alarm detecting sections corresponding to the first to third channels, and supplies a selector change signal and a timer reset signal to the selector of the wait-to-restore section corresponding to the first channel. At the time of mode change from the STS-1 mode to the STS-3c mode or vice versa, the timer of the wait-to-restore section corresponding to the first channel is reset. In STS-3c mode, timers of the wait-to-restore sections corresponding to the second and third channels exclusive for the STS-1 mode are reset.

Transmission system

Error detection apparatus for a communications line includes an even/odd detection unit for detecting whether an even number of bipolar pulses or an odd number of bipolar pulses occur between a first pulse (violation pulse) interrupting an alternating pattern of bipolar pulses and a second pulse (violation pulse), and an output unit which determines that there is a line error in a target block defined by the first and second violation pulses when a detection result of the even/odd detection unit indicates an even number, wherein the first and second violation pulses occur in a code sequence in accordance with a predetermined coding scheme.

Apparatus for detecting error in a communications line

An optical transmission device for transmitting and receiving SONET signals has a path switch controlled in operation depending on the states of signals received bidirectionally over optical transmission lines. The optical transmission device generates one of a plurality of path switch alarms indicative of respective faults of the signals, based on the states of the signals transmitted to the path switch, and actuates the path switch depending on the generated path switch alarm to output one of the signals from two line terminal equipment units to a lower-level receiver. When SONET signals are transmitted and received in an A/B ring mode, the path switch is actuated in at least one of five control modes to output one of the signals from the two line terminal equipment unit to the lower-level receiver. When SONET signals are transmitted and received in a linear mode, a tributary path function added to the path switch is activated to meet a requirement for the reception of an optical signal transmitted over a unidirectional one of the optical transmission lines.

Method of changing over path switch in optical transmission device

A terminal equipment is connected in a first optical network and connected, via a conductive path, to a predetermined one of a plurality of communication devices connected in a second optical network. The above terminal equipment includes an optical transmitter/receiver unit, a controller for controlling the above predetermined one of the communication devices in order to monitor the communication devices connected in the second optical network, and a selector unit. This selector unit transfers, via a control path coupled to the predetermined one of the communication devices, a poling signal from the first optical network to a specified one of the communication devices addressed by the poling signal, and sends back, to the first optical network, control data which shows a status of the specified one of the communication devices connected in the second optical network and which is received, via the control path, from the specified one of the communication devices.

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Kawasaki, Japan

Junichi Ishiwatari