JPH06164517A - Optical add / drop node and optical communication network using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] An optical add / drop node and an optical communication network using the same, which are preferably used for communication in which data is written in cells time-divisionally multiplexed by optical signals. [Structure] An optical branching device 11 and an optical combining device 17 are installed on a transmission line in a node, and an optical delay device 18, an optical delay device 18 is provided in an optical adding / dropping node so that reading and writing of an optical signal can be performed via them. And branch signal light level detector 13 and E / O
An optical output control circuit 14 for controlling the converter 16 or an optical amplifier and a control circuit for controlling the gain thereof are provided. The optical delay device 18 delays the optical signal transmitted between the optical branching device 11 and the optical combiner 17 in the node, and adjusts it to the slot position of the optical signal from the E / O converter 16. Based on the information from the level detector 13, the optical output control circuit 14 makes the light quantity of the output signal from the O / E converter 16 combined by the optical combiner 17 substantially equal to the other light quantity to be merged. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical add / drop node in an optical communication system in which a plurality of nodes are connected on an optical transmission line, and an optical communication network using the optical add / drop node.

[0002]

2. Description of the Related Art Conventionally, in an optical communication system in which a plurality of nodes are connected to an optical transmission line, there are various methods for performing channel access control so as not to cause data collision while watching a communication request call from each node. Has been proposed,
One of them is DQDB (Distributed Queue).
ued Dual Bus) method.

In the DQDB method, a fixed-length cell is transmitted from the upstream side of an optical transmission line, and a node that obtains a transmission right detects whether the cell is in use, divides the data into cell lengths, and leaves the data empty. It is a method of inserting into cells. Next, the data insertion operation will be described. FIG. 5 shows a block diagram in the node of the DQDB method. In FIG. 5, reference numeral 51 denotes an O / that converts an optical signal sent from the preceding node into an electric signal.
E converters, 52 and 53 are flip-flop circuits that read data at clock timings, 54 is an OR circuit that combines the bits of the transmitted signal and the signal sent from the node, and 55 is an electrical circuit that is combined by the OR circuit 54. An E / O converter for converting a signal into an optical signal, 56 analyzes the presence or absence of data in the cell and transmission request information from a node located downstream from the header information of the cell, and further transmits from this analysis result. When the right is obtained, the communication control circuit 511 for sending the data transmitted from the terminal 520 to the flip-flop 53.
Is an optical fiber which is a transmission path of an optical signal.

In this device, the optical signal sent from the preceding node is converted into an electric signal by the O / E converter 51 and sent to the flip-flop 52 and the communication control circuit 56. The signal sent to the flip-flop 52 is synchronized with the extracted clock and input to the OR circuit 54. Communication control circuit 56
Analyzes the presence or absence of data in the cell or the transmission request information from the node located downstream, and when the data is not written in the cell, inputs the transfer data from the terminal 520 to the flip-flop 53, When data is written in the cell, the address of the cell is analyzed, and if the data is addressed to the own node, the information is input to the terminal 520.
The flip-flop 53 reads the transmission signal transmitted from the communication control circuit 56 by the timing clock indicating the position of the insertion slot generated from the extraction clock and transfers it to the OR circuit 54. Where flip-flop 5
Reference numerals 2 and 53 read data at the same timing and output the signals with the phases of both signals aligned. The OR circuit 54 combines the bit indicating the writing space of the cell sent from the flip-flop 52 and the bit of the divided transmission data from the flip-flop 53, and the E / O converter 55 causes the OR circuit 54 to
The composite signal from the optical fiber is converted into an optical signal and transmitted to the optical transmission line 511.

As described above, the data from the terminal 520 is time-division multiplexed without colliding with signals from other nodes.

[0006]

In the above-mentioned conventional apparatus, a processing relay circuit for converting an optical signal into an electric signal and performing a writing process is arranged on the transmission line, and therefore the processing circuit is required to have high reliability. In this respect, if the writing process can be performed with the optical signal as it is, this processing circuit can be eliminated. However, a specific configuration of an optical add / drop node that writes data by an optical signal to a fixed length cell that transmits on an optical transmission line has not been proposed yet.

In view of the above points, an object of the present invention is to provide an optical add / drop node preferably used for communication for writing data to a fixed length cell by an optical signal, and an optical communication using this optical add / drop node. To provide a network.

[0008]

In an optical add / drop node according to the present invention that achieves the above object, in an optical communication network in which a plurality of nodes are connected by an optical transmission line, the nodes are means for delaying light passing through the nodes. An optical signal inserting means and a means for making the light amounts of the delayed node passing light and the inserted optical output signal substantially equal are provided.

More specifically, an optical branching device for branching a part of the optical signal transmitted on the optical transmission line, and an O / E converter for converting the branched optical signal from the optical branching device into an electrical signal. , A level detection circuit for calculating the light quantity of the branched optical signal, an E / O converter for converting an electric signal to be transmitted into an optical signal, and an optical output of the E / O converter based on information from the level detection circuit. An optical output control circuit for controlling, an optical delay device for delaying the remaining optical signal branched by the optical branching device, an optical signal from the optical delay device and an optical signal from the E / O converter are merged, and optical transmission is performed. The optical output control circuit is configured so that the intensity of the optical signal from the E / O converter transmitted from the optical coupler to the optical transmission line is almost the same as the intensity of the optical signal from the delay device. It is characterized in that it is configured to perform control so as to be equal to each other, or is transmitted over an optical transmission line. Optical branching device for branching a part of the existing optical signal, O / E converter for converting the branched optical signal from the optical branching device into an electrical signal, and optical amplifier for amplifying the remaining optical signal branched by the optical branching device A gain control circuit for controlling the gain of the optical amplifier, an optical delay device for delaying the remaining optical signal branched by the optical branch device, a delayed optical signal from the optical delay device and an optical signal from the E / O converter The gain control circuit is configured to adjust the amount of light to be amplified by the optical amplifier to an output determined by the system.

That is, in order to solve the above-mentioned problems, a processing repeater for converting an electric signal from a transmission line is deleted, an optical branching device and an optical combiner are installed on the transmission line in a node, and an optical signal is transmitted through them. In order to be able to read and write data in the optical add / drop node, an optical delay circuit, an optical output control circuit for controlling the level detector and E / O converter of the branched signal light, or an optical amplifier and its gain The optical delay device delays the optical signal transmitted between the optical branching device in the node and the optical combiner, and each slot of the optical signal from the E / O converter and the delayed optical signal is provided. Adjust the position. The optical output control circuit, based on the information from the level detector or the photodetector, makes the light amount of the output signal from the O / E converter combined by the optical combiner approximately equal to the other combined light amount. Control to match. Further, the gain control circuit adjusts the amount of light amplified by the optical amplifier to an output determined by the system.

With the above configuration, the data from the own node can be inserted as an optical signal into the optical signal cell on the transmission line without demodulating the transmission signal cell into an electric signal.

[0012]

[First Embodiment] First, a first embodiment of the present invention will be described with reference to FIG.

FIG. 1 shows an optical add / drop node of the first embodiment. The optical add / drop node is an optical fiber 11.
1, an optical branching device 11 connected to the preceding node, an O / E converter 12 located in an optical fiber 113 which is a branching path of the optical branching device 11, and a level detection connected to the O / E converter 12. The circuit 13, the level detector 13, the optical output control circuit 14 connected to the communication control circuit 15, and the O / E converter 12 are connected to control the input and output of data divided into fixed length cells. A communication control circuit 15 for analyzing cell header information, an optical output control circuit 14, an E / O converter 16 connected to the communication control circuit 15, an optical branching device 11 and an optical fiber 112, and an optical branching device. An optical delay device 18 (composed of a plurality of optical fibers wound in a loop) for delaying cells of optical signals branched at 11 and transmitted through the optical fiber 112, and the optical delay device 18 and the optical fiber 112. Connected by It is provided with a light converging unit 17 to synthesize the cell transfer optical signals from the cells and the E / O converter 16 of the optical signal transmitted through the optical fiber 112.

Next, the operation of dropping and inserting an optical signal in the optical add / drop node device of the first embodiment of the present invention in the DQDB system protocol will be described.

In the DQDB method, a time-division multiplex cell having a header in which the presence / absence of data in a fixed length cell, a transmission request from a node, an address of transfer data, etc. are written is sent from the upstream side of an optical transmission line. The node is a system that analyzes the header information of the cell to communicate with at any time and writes the transfer data to the empty cell according to the result.

At this time, the optical signals of the divisionally multiplexed cells are transferred from the preceding node and branched by the optical branching device 11. The branched optical signal is input to the O / E converter 12, and the other optical signal is transmitted through the optical fiber 112. The optical signal input to the O / E converter 12 is converted into an electrical signal there and input to the level detection circuit 13 and the communication control circuit 15.

The level detection circuit 13 detects the detection level of the optical signal based on the electric signal, and the optical output control circuit 14
Send to. From the detection level, the optical output control circuit 14
The light quantity of the optical signal branched by the optical branching device 11 and input to the optical fiber 113 is calculated, and from the light quantity and the branching ratio of the optical branching device 11, the other of the optical signals branched by the optical branching device 11 and input to the optical delay device 18 is calculated. The light quantity of the optical signal is calculated back. And the merger 17
The optical output control circuit 14 controls the E / O converter 1 so that the light amount of the signal transmitted through the optical fiber 112 and the light amount of the optical signal transmitted from the E / O converter 16 match even if the branching ratio is changed.
The output light amount of 6 is controlled. Bit read processing is 0
A signal transmitted through the optical fiber 114 is a signal transmitted through the optical fiber 114 because the integrated average of the signal and the 1 signal is used as a reference, and when the signal is lower than the reference, it is recognized as the 0 signal and when it is higher than the reference, it is recognized as the 1 signal. If the intensity is significantly smaller than the intensity of the signal, all the signals transmitted through the optical fiber 112 may be recognized as 0 signals on the receiving side, and accurate signal transmission / reception cannot be achieved. Therefore, in order to match the intensities of the two signals and enable accurate signal transmission, the level detector 13
And a light output control circuit 14 are provided.

The communication control circuit 15 analyzes the presence or absence of data in the cell, the access control information, the data transmission destination address, etc. from the input electric signal. When the transmission cell addressed to the own node is received, it is divided into a header information part and a transmission data part and the transmission data is sent to the terminal 120. When the own node acquires the transmission right, the data sent from the own node divided into cell lengths is sent to the E / O converter 16, converted into an optical signal and sent. At the same time, the communication control circuit 15 sends a light amount control start command for the E / O converter 16 to the light output control circuit 14. When the transfer data from the terminal 120, which is divided into cell lengths, is converted into an optical signal by the O / E converter 16 and transmitted, the optical delay device 18 causes an empty cell of the optical signal passing through the optical fiber 112 and E In order to match the optical signal of the transfer data sent from the / O converter 16 to the position of a predetermined time slot, the header information of the optical signal cell branched by the optical splitter 11 and input to the O / E converter 12 The optical signal cell passing through the optical delay device 18 is delayed by the analysis time or other processing time. Then, the optical signal cell that has passed through the optical delay device 18 and is aligned with the position of the predetermined time slot and the optical signal of the transfer data from the E / O converter 16 are combined in the optical combiner 17, and the optical signal from the node is combined. The transmitted data can be transmitted without error.

Next, FIG. 2 shows an optical communication network using the above described optical add / drop node. In the figure, communication is performed between the nodes 231 to 239 (corresponding to the terminals 221 to 229, respectively) using the above-mentioned DQDB method, and communication is performed using the transmission path 211 for the right direction and the transmission path 212 for the left direction. To do this, by arranging the optical add / drop node 630 shown in this embodiment as shown in FIG.
The QDB node 625 (corresponding to the terminal 620) can be preferably used in the DQDB system network shown in FIG. In FIG. 5, a rightward transmission line 611 and a leftward transmission line 612 correspond to the rightward transmission line 211 and the leftward transmission line 212 of FIG.

[0020]

[Second Embodiment] FIG. 3 shows a second embodiment of the present invention. In this embodiment, in order to make the light amount of the optical signal sent from the node after passing through the optical delay device 46 and the optical amount of the optical signal from the E / O converter 47 substantially equal, An optical amplifier 44 is provided between them.

In FIG. 3, an optical branching device 41 connected to the preceding node by an optical fiber 411, an O / E converter 42 located on a branching path of the optical branching device 41, and an O / E converter 4 are shown.
2, a communication control circuit 43 (corresponding to the terminal 420) that controls input / output of data divided into fixed length cells and analyzes header information of each cell, and E / connected to the communication control circuit 43. An optical amplifier 44, which is connected to the O converter 47, the optical branching device 41, and an optical fiber 412 and keeps the amount of light output from the optical combiner 48 constant, a control circuit 45 for controlling the gain of the optical amplifier 44, and an optical amplifier 44. Is connected by an optical fiber 412, and is connected by an optical delay device 46 for delaying the cell of the optical signal branched by the optical branching device 41 and transmitted through the optical fiber 412, and the optical delay device 46 and the optical fiber 412. An optical combiner 48 for combining the cell of the transmitted optical signal and the cell of the transferred optical signal from the E / O converter 47 is provided.

The optical amplifier 44 amplifies the light on the optical fiber 412 input to the optical combiner 48, and the control circuit 45
Controls the optical output from the optical amplifier 44 to the set light amount. Therefore, it is not necessary to control the light quantity of the optical signal input from the E / O converter 47 to the optical combiner 48.
In the first and second embodiments, since the light quantity of the optical signal passing through the optical delay device fluctuates, the light quantity from the O / E converter is adjusted to the fluctuation, but in the present embodiment, the optical amplifier 44 Since the amount of light passing through the delay device 46 is controlled to the set light intensity, the amount of light from the E / O converter 47 may be set to a constant value corresponding to the set light intensity. The positions of the optical delay device 46 and the optical amplifier 44 may be reversed.

As described above, according to this embodiment, as shown in FIG.
It is possible to obtain the same effect as that of the first embodiment shown in (1) without using the level detector 13 and the optical output control circuit 14.

Further, by arranging the optical add / drop node 630 shown in this embodiment as shown in FIG.
The DB node 625 can be preferably used in the DQDB system network shown in FIG.

Further, as described in each of the above embodiments, the optical add / drop node is preferably used in the optical communication network using the DQDB system, but can be applied to other communication systems using time division multiplexing. Needless to say.

[0026]

As is apparent from the above description, the optical add / drop node of the present invention is an optical delay device that delays an optical signal cell without converting the optical cell on the optical transmission line into an electrical signal. By means of equalizing the intensities of the delayed optical signal sent from the node and the optical signal from the own node, data can be written in the time-division multiplexed optical signal cell by the optical signal. Therefore, it is possible to provide an optical communication network that does not require a highly reliable repeater that converts an optical cell into an electric signal and processes it.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a node according to a first embodiment of this invention.

FIG. 2 D in the first and second embodiments of the present invention
It is a block diagram of an optical communication network using the QDB method.

FIG. 3 is a diagram showing a configuration of a node according to a second exemplary embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a DQDB system node using the present invention.

FIG. 5 is a diagram showing a configuration of a node of a conventional example.

[Explanation of symbols]

11, 41 Optical branching device 12, 42, 51 O / E converter 13 Level detector 14 Optical output control circuit 44 Optical amplifier 45 Control circuit 15, 43, 56 Communication control circuit 16, 47, 55 E
/ O converter 17,48 Optical combiner 18,46 Optical delay device 111-114,411-414,511 Optical fiber 211,611 Right direction optical transmitter 212,612 Left direction optical transmitter 231-239,630
Optical add / drop node 625 DQD
B system node 120, 221-229, 420, 520, 620
Terminals 52 and 53 Flip-flop 54 OR circuit

Claims (5)

[Claims] 1. In an optical communication network in which a plurality of nodes are connected by an optical transmission line, the nodes are inserted with a node passing light delaying means, an optical signal inserting means, and a delayed node passing light. An optical add / drop node comprising means for making the light output signals have substantially the same light intensity. 2. An optical branching device for branching a part of an optical signal transmitted on the optical transmission line, an O / E converter for converting a branched optical signal from the optical branching device into an electric signal, A level detection circuit for calculating the light quantity of the branched optical signal, an E / O converter for converting an electric signal to be transmitted into an optical signal, and an optical output of the E / O converter based on information from the level detection circuit. , An optical output control circuit for controlling the optical signal, an optical delay device for delaying the remaining optical signal branched by the optical branch device, a merged optical signal from the E / O converter and a delayed optical signal from the optical delay device. And an optical combiner for transmitting the optical signal from the E / O converter to the optical transmission line from the optical combiner. The control is performed so that the intensity of the optical signal from the container is substantially equal to the intensity of the optical signal. Optical add / drop node. 3. An optical branching device for branching a part of the optical signal transmitted on the optical transmission line, an O / E converter for converting the branched optical signal from the optical branching device into an electric signal, An optical amplifier for amplifying the remaining optical signal branched by the optical branching device, a gain control circuit for controlling the gain of the optical amplifier, an optical delay device for delaying the remaining optical signal branched by the optical branching device, The gain control circuit includes an optical combiner for combining the delayed optical signal from the optical delay device and the optical signal from the E / O converter and sending the combined optical signal to the optical transmission line. The optical add / drop node according to claim 1, wherein the optical add / drop node is configured to adjust the output to a system-determined output. 4. An optical communication network using the optical add / drop node according to claim 1, 2 or 3 as a node of the network. 5. An optical communication network, wherein the optical add / drop node according to claim 1, 2 or 3 is used as a node of a DQDB system network.