Fujitsu Corporation

Fumihiro Ikawa

Koichi Nishimura

Junichi Moriyama

Kanji Naito

Ikuo Taniguchi

Hatsumi Iino

Hisashi Taketomi

Masumi Kurokawa

An optical receiver unit is connected to each of a work optical line and a protection optical line, and after an optical signal is converted to an electrical signal, only the overhead of the signal is extracted. Furthermore, bytes accommodated in the overhead are demultiplexed. K bytes are transferred to both an APS processing unit and a mismatching judgement unit. The mismatching judging unit judges whether or not a WTR, DNR, RR, etc. are set in the K1 byte received from the opposite station, compares the mode of the opposite station with the mode of its own station, and detects a mismatching between the modes of the opposite and own stations. The result of the detection is transferred to the APS processing unit, and if there is a mismatching, the mismatching is solved.

Terminal apparatus, device for detecting the mismatching of work/protection line bridging function in a synchronous communication network and the method

An optical transmission system containing a protection system and a plurality of working systems. When a trouble occurs in the protection system to which one of the working system is switched, a line alarm indication signal (LINE AIS), which can be detected in a reception portion of a piece of terminal equipment, and can activate a switch control circuit, is transmitted to a piece of terminal equipment on the reception side. In response to the receipt of the line alarm indication signal (LINE AIS), the piece of terminal equipment on the reception side transmits a far end receive failure signal (FERF) through an protection system optical transmission line (PTCT2) to a piece of protection system terminal equipment on the transmission side, and transmits a path alarm indication signal (PATH AIS) which does not activate the switch control circuit, through an optical transmission line in the same terminal station to the pieces of working system terminal equipment in the same terminal station on the reception side.

Optical transmission system wherein protection terminal equipment

Nested APS is implemented in a simple configuration for synchronous transmission systems such as SONET and SDH. Bits 5 to 8 of the received K1 byte are compared with line numbers of lines terminated at the receiving node, and when they do not match, the received K1 byte is sent via a first selection circuit for further transmission. At the same time, the K2 byte incoming from the opposing direction is redirected via second selection circuit for transmission.

Method and apparatus for nested automatic protection switching

Disclosed is an optical transmission system for transmitting data via an optical transmission line in accordance with a frame format having overhead which includes a K1 byte used for a switching request and a K2 byte used to respond to the K1 byte. The optical transmission system includes N sets of working terminal stations, one set of protection terminal stations, N-number of optical transmission lines for interconnecting respective ones of the N sets of working terminal stations one optical protection transmission line for interconnecting the one set of protection terminal stations, repeater stations, which are provided in the optical transmission lines between the N sets of working terminal stations, for demultiplexing and outputting data extracted from the transmission lines or for multiplexing data and inserting the data in the transmission lines, protection transmission line connecting units, which are provided at positions in a protection transmission line corresponding to positions at which the repeater stations are disposed, for switching a failed transmission line to the protection transmission line in every section demarcated by the repeater stations. A working terminal station or repeater station that has detected occurrence of failure in a transmission line of a prescribed section sends K1 byte to and receives K2 byte from an opposing working terminal station or repeater station of the section via a protection terminal station or protection transmission line connecting unit and switches the failed transmission line section to the protection transmission line.

Optical transmission system and transmission line switching control

A line switching control system provided in each of stations connected by a first type line and a second type line in a synchronous communication network system in which frame data including an overhead is transmitted through the first type line or the second type line between the stations. The line switching control system includes a protection switching unit for switching the first type line used as a work line to the second type line defined as a protection line in a predetermined switching mode when a failure occurs in the first type line, and a unit, when the failure first type line is recovered, for transmitting line recovery mode information representing whether a line recovery mode is a REV mode in which the recovered first type line is reverted as the work line or a NON-REV mode in which the second type line is continuously used as a new work line and the recovered first type line is defined as a new protection line, the line recovery mode information being included in the overhead of the frame data.

Line switching control system in synchronous communication network system

A communication system includes a plurality of stations, a first working line coupling adjacent stations among the plurality of stations, a second working line passing predetermined stations among the plurality of stations without dropping therein, and a protection line provided in common for the first working line and the second working line, a supervisory signal always passing through the protection line. Each of the stations includes an internal circuit for receiving an input transmission signal from the first working line and sending an output transmission signal to the first working line. Each station also includes a switching portion for passing the protection line without dropping in each of the stations in a normal mode and for connecting the protection line to the internal circuit in an alarm mode so that the input transmission signal is received from an upstream side via the protection line instead of the first working line and the supervisory signal which is generated from the output transmission signal is output toward a downstream side via the protection line.

Optical communication system having an improved protection line

A one-to-one line switching system for switching between a hot line and a standby line in a one-to-one correspondence. To enable removal of a switching unit while in use, from a mother board for change over or repair, a pair of switching units (1 and 2 or 3 and 4) is provided at the transmitting part and at the receiving part, respectively, the earth element in one of the pair being connected to the other of the pair and the other of the pair being pulled up by a voltage, whereby, when one of the pair in use is removed, the other of the pair can pass the input signal.

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Kawasaki, Japan

Fumihiro Ikawa