JP2002198905A - Subscriber local loop communication system for optical fiber network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high reliable and low cost subscriber local loop communication system for an optical fiber network with a simple configuration. SOLUTION: Loop-shaped optical fiber lines constituted of two systems having a normal line 10 and a backup line 11 connect station equipment 1 and a plurality of nodes N1-N15 in a loop form. Each node includes a first splitter 21 connected to the normal line 10, a second splitter 22 connected to the backup line 11 and an add drop multiplexer 23 connected to the first and second splitters. An optical signal transmitted on the loop-shaped normal line 10 is monitored by the station equipment 1. The station equipment 1 is so configured as to transmit an optical signal on the backup line 11 when an optical signal is not detected by the monitoring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop type optical fiber network subscriber system and, more particularly, to a loop type optical fiber network subscriber system which can be formed with a simple structure and can provide high reliability. .

[0002]

2. Description of the Related Art Conventionally, in an optical fiber system applied to a subscriber system, ADS (Active Double Star) and PDS
(Passive double star) is common. When connecting the office side and the subscriber side by individual lines, it is called a single star, and when connecting from one common line to a plurality of subscriber lines, it is called a double star. When the branching means is an active circuit, it is called an active double star, and when it is a passive circuit, it is called a passive double star.

An outline of the PDS system will be described with reference to FIG. This system has 25 passive circuits.
The case where a 6-branch splitter is used is shown. The 25
The six-branch splitter is, in principle, a two-branch splitter 6
1 are connected in multiple stages. The two-branch splitter 61
As shown in FIG. 6, the optical signals input from the branch ends 1 and 2 are combined (combined) at a fixed ratio and transmitted to the collecting end, while the optical signals input to the collecting end are Is divided (demultiplexed) at a fixed ratio and transmitted to the branch end.

[0004] As a communication method, for example, an uplink from a station-side facility (hereinafter referred to as OLU) to a subscriber device (hereinafter referred to as ONU. ONU: Optical Network Unit) is a TDMA (Time Division Multiplex) method. For the downlink, the TDM system is used. When the upstream and downstream are shared by one line, a ping-pong system in which upstream and downstream are alternately communicated, and a WDM (wavelength multiplexing) system in which light of different wavelengths is used for upstream and downstream are used.

[0005]

However, the above-mentioned PDS system has a problem that communication with a plurality of subscribers becomes impossible when the station side line or a two-way splitter in the middle breaks down. Further, when the two-branch splitter is moved closer to the OLT to facilitate maintenance, there is a problem that the total length of the subscriber-side line is increased and the cost is increased.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a high-reliability and low-cost loop type optical fiber network subscriber which can be constructed with a simple configuration. System communication system.

[0007]

In order to achieve the above-mentioned object, the present invention provides an optical fiber line having a starting end and a terminating end at a station-side facility, wherein m (m is a positive integer) nodes are looped. In the connected loop type optical fiber network subscriber system, the optical fiber line is composed of two lines of a normal line and a backup line, and the m nodes are respectively connected to the normal line. A first splitter; a second splitter connected to the backup line; and a splitter / combiner connected to the first and second splitters, wherein the first splitter receives the input light. The second splitter splits a signal into a normal line connected to an adjacent node and the splitter / combiner, and the second splitter converts the input optical signal into a backup line connected to the adjacent node. The first and second splitters multiplex the optical signals input from opposite directions, respectively, and the optical signal transmitted through the loop-shaped normal line is the same as that of the first embodiment. Monitored by office equipment,
The first characteristic is that the optical line terminal transmits an optical signal to the backup line when the optical signal is not detected by the monitor.

According to this feature, both of the optical signal transmitted through the normal line and the backup line can be guided to a common splitter / combiner.
Further, it is possible to provide a highly reliable and low-cost loop type optical fiber network subscriber communication system with a simple configuration.

In the present invention, the branching ratio of the first splitter of an n-th node (n is a positive integer satisfying n ≦ m) is set to about 1: (m−n + 1), A second feature is that the splitting ratio of the splitter is set to about n: 1.

According to this feature, the level of the optical signal output from the multiplexer collecting end of the demultiplexer / demultiplexer can be made uniform at all of the m nodes. Further, the level of the optical signal reaching the optical line terminal from the m nodes can be made uniform.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 shows a system diagram of an embodiment of the present invention.

A center station or station-side equipment (OLT: Optica)
l Line Terminal 1 is an optical subscriber unit (OSU: O)
(Ptical Subscriber Unit) 2 and a monitor unit 3. The station-side equipment 1 includes a loop-like 2 starting from the optical subscriber unit 2 and entering the monitor unit 3.
System optical fibers 10 and 11 are connected, and 15 nodes N1 to N15 are connected in the middle of the optical fibers. Of the two optical fibers, one is a line for performing normal communication (hereinafter, referred to as a normal line 10), and the other is broken (for example, in the middle of the line).
This is a line (hereinafter, referred to as a backup line 11) for performing communication by a reverse route when an optical fiber break occurs.

Since the nodes N1 to N15 have the same configuration, the configuration of the node N1 will be described as a representative. The node N1 is connected to the normal splitter 21 connected to the normal line 10 and to the backup line 11. And a splitter / combiner 23 connected to each of the normal splitter 21 and one of the branch lines of the backup splitter 22. here,
As the normal splitter 21, the backup splitter 22, and the splitter / combiner 23, basically, the two-branch splitter having the collecting end and the branching ends 1 and 2 shown in FIG. 6 can be used.

As a method for producing the two-branch splitter, two optical fibers are generally processed and fused. Further, the two-branch splitter splits (demultiplexes) the optical signal input to the collecting end at an arbitrary ratio, and
2 to be transmitted. The optical signals input from the branching ends 1 and 2 are combined (combined) at a ratio automatically determined by the manufacturing and transmitted to the collecting end.

The node N1 further includes the demultiplexer / multiplexer 23.
, A multi-branch splitter 24 having four branches connected to the collecting end of the multi-segment. The multi-splitter 24 can also be configured by connecting the two-branch splitter in multiple stages as shown.

Output end (branch end) of the multi-splitter 24
Are two-stage splitters 31 and 32 disposed outside.
Are connected to ONUs (subscriber devices) 41 and 42 via the. In addition, the ONU via the two-branch splitters 31 and 33
43 and 44. Therefore, in the illustrated example, one node N1 has 16 ONUs 41, 42, 43,.
・ Can be connected. In the present embodiment, 1
Each station-side facility 1 can accommodate 240 ONUs. This scale is an example, and the present invention is not limited to this.

As a preferred embodiment of the present invention, the node N1
Use a normal splitter 21 that branches to the splitter / multiplexer 23 at a rate of 1 and a node N2 to branch at a rate of 15; the backup splitter 22 uses 1 for the splitter / multiplexer 23 and 1 for the monitor unit 3. Use the one that branches at the ratio of
In the node N2, a normal splitter that splits at a ratio of 1:14 and a backup splitter that splits 1: 2 are used. Hereinafter, a normal splitter and a backup splitter whose branch ratio is determined by the same rule are used for each of the nodes N3 to N15.

Next, the operation of this embodiment having the above-described configuration will be described. In a normal state, an optical signal emitted from the optical subscriber unit 2 of the optical line terminal 1 passes through the normal line 10 and sequentially from the first node N1 to the fifteenth node N15 via the normal splitters 21 of each node. And transmitted to the monitor unit 3 of the station-side equipment 1. Upon receiving the optical signal, the monitor unit 3 confirms that the operation is normally performed.

When receiving the optical signal from the optical subscriber unit 2, the splitter 21 of the first node N1 splits the intensity of the optical signal at a ratio of 1:15, and separates and combines the optical signal having the intensity of 1. Send to waver 23. The splitter / multiplexer 23 further transmits the optical signal to a multi-splitter 24, which distributes the optical signal to 16 subscriber units ONUs.

On the other hand, the optical signal having the intensity of 15 branched from the splitter 21 is output to the normal line 10 going to the second node N2, and is input to the normal splitter of the second node N2. In the normal splitter, the optical signal is split at a ratio of 1:14, the optical signal having the intensity of 1 is supplied to the splitter / combiner, and the optical signal having the intensity of 14 is supplied to the third node N3.
Output to the normal line going to. The optical signal having the intensity of 1 input to the splitter / combiner passes through the multi-splitter and is distributed to 16 subscriber units ONU as in the case of the first node N1.

Hereinafter, in the third, fourth,..., And fourteenth nodes, the same operation as described above is performed. At the last fifteenth node N15, the optical signal input to the normal splitter 25 is split in a one-to-one ratio, one split signal is sent to the demultiplexer / multiplexer 26, and the other split signal is sent to the station-side equipment. Is transmitted to the first monitor unit 3.

As a result, 24 stations accommodated in the station-side equipment 1
Optical signals having the same strength reach zero subscriber units ONU, and the received signal level can be made uniform. When a failure or the like of the normal line 10 occurs, the optical signal is transmitted to the monitor unit 3
, The fault or the like is immediately detected.

Next, an operation when a fault occurs in the normal line 10 will be described. When the optical signal is no longer received by the monitor unit 3, the station-side equipment 1 issues an alarm at that time to prompt inspection and repair, and starts communication toward the back splitter 27 of the fifteenth node N15 after a fixed time. . At this time, the communication from the station side equipment 1 to the normal line 10 is continuously performed.

The signal transmitted to the back splitter 27 is transmitted from the fifteenth node N15 to the fourteenth node, the thirteenth node,... To the point of failure. Obviously, the optical signal is not transmitted after the point of failure.

Therefore, when a fault occurs in the line, communication is performed via the normal line 10 to the node up to the point before the point of failure of the line, and via the backup line 11 to nodes subsequent to the point of failure.

Therefore, according to the present embodiment, even if a fault such as a line disconnection occurs, backup can be performed immediately, and a highly reliable system can be provided.
Further, since an optical fiber is used, a system capable of high-speed communication can be provided.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, wireless access is made possible using the above-mentioned loop type fiber network.

In the present embodiment, as shown in the figure, a media converter, that is, an optical / electrical converter (O / O) is provided at each node, for example, at the combiner collecting end of the multiplexer / demultiplexer 23 of the first node N1. / E) 52 is connected, and a hub 53 is connected to its electric output end.
Via a wireless access base station (radio 54 + antenna 5
5) is connected. Then, a radio wave is emitted from the antenna 55 to perform wireless communication with the subscriber unit ONU. According to this method, a low-cost and highly reliable system can be provided without making a major change to the loop type optical fiber network.

Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, wired (ETTH) access is made possible using the above-mentioned loop type fiber network.

In this embodiment, as shown in the figure, a media converter, that is, an optical / electrical converter (O / O) is provided at each node, for example, at the multiplexer collecting end of the multiplexer / demultiplexer 23 of the first node N1. / E) 52 is connected, and a hub 53 is connected to its electric output end.
Via a metallic cable such as an Ethernet bus line (for example, 10BASE-5)
A coaxial cable 56 is connected, and a plurality of subscriber units 57 are connected via the Ethernet bus line 56.

According to this embodiment, the cost is higher than that of the second embodiment but lower than that of the first embodiment, and is lower than that of the first embodiment but higher than that of the second embodiment. It is possible to provide a highly reliable system.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, an optical fiber access (FTTH: Fi
berTo The Home), wireless access, and wired access (ETTH: Ethernet To The Home), or any two of these three accesses can be simultaneously performed.

In this embodiment, as shown in FIG. 4, a two-branch splitter 51 is connected to each node, for example, the splitter / combiner 23 of the first node N1, and one of the two-branch splitter 51 Is connected to the multi-splitter 24, and the other terminal is connected to the optical / electrical converter (O / E) 52. The multi-splitter 24 includes a subscriber unit 41, an optical fiber and splitters 31, 32, 33,.
, 43, ... are connected. On the other hand, the optical / electrical converter 5
2, a switching hub 53 is connected, and the switching hub 53 is connected to a wireless access base station, that is, a wireless device 5.
4. Connect to antenna 55. An Ethernet bus line 56 is connected to the switching hub 53, and an Ethernet subscriber device 57 is connected to the Ethernet bus line 56.

According to this configuration, an optical fiber can be accessed via the multi-splitter 24.
In addition, wireless access can be made via the antenna 55, and wired access can be made via the Ethernet bus line 56.

According to this embodiment, it is possible to provide a highly reliable communication system that can be accessed by any of optical fiber, wireless, and wired, or any combination of the two. In addition, it is considered that the needs of the Internet connection and the like will differ depending on the user layer and the era, and it becomes possible to set a final subscriber line corresponding to such needs or suitable for the needs.

[0036]

As is apparent from the above description, according to the first to sixth aspects of the present invention, even if a failure such as a breakage of a loop-shaped optical fiber line occurs on the way, it can be dealt with immediately. Therefore, it is possible to provide a highly reliable and inexpensive loop type optical fiber network subscriber communication system with a simple configuration.

According to the second aspect of the present invention, in addition to the above effects, the levels of the optical signals output from the nodes become equal, and the reception level of the subscriber unit can be made uniform. become.

According to each of the third to sixth aspects of the present invention, an optical fiber access (FTTH: Fiber To The Hom)
e), wireless access and wired access (ETTH: E
Thernet To The Home) can be performed individually or in any combination, so that a communication system that meets the needs of the user can be provided.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a system diagram showing a configuration of a second embodiment of the present invention.

FIG. 3 is a system diagram showing a configuration of a third embodiment of the present invention.

FIG. 4 is a system diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 5 is a system diagram showing an example of a conventional configuration.

FIG. 6 is an explanatory diagram of functions of a splitter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Station-side equipment, 2 ... Optical subscriber unit, 3 ... Monitor unit, N1-N15 ... Node, 10 ... Normal line, 11 ... Backup line, 21 ... Normal splitter, 22: Backup splitter, 23: Splitter / combiner, 24: Multi splitter, 41, 42, 43,
44 ... subscriber unit (ONU), 52 ... optical / electrical converter, 53 ... hub, 54 ... radio, 56 ... Ethernet bus line.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5K002 BA05 DA11 EA05 EA33 FA01 5K031 AA06 AA08 DA02 DA12 DA19 DB12 DB14 EA03 EA11 EB02 EB06 5K033 AA04 AA06 DA01 DA14 DA16 DB02 DB22 EA02 EA04 EA06 EB02 EB06

Claims (6)

[Claims] 1. A loop-type optical fiber subscriber line communication system in which m (m is a positive integer) nodes are connected in a loop by an optical fiber line having a start end and an end in a station-side facility. The line is composed of two lines of a normal line and a backup line, and each of the m nodes is a first splitter connected to the normal line and a second splitter connected to the backup line, respectively. And a splitter / combiner connected to the first and second splitters, wherein the first splitter converts an input optical signal into a normal line connected to an adjacent node and the splitter / multiplexer. The second splitter splits the input optical signal into a backup line connected to an adjacent node and the splitter / multiplexer, and also splits the first and second splitters. The multiplexor multiplexes the optical signals input from the opposite directions, respectively.The optical signal transmitted through the loop-shaped normal line is monitored by the station side equipment, and when the optical signal is not detected by the monitor. Wherein the station-side equipment transmits an optical signal to the backup line. 2. The branching ratio of the first splitter of an n-th node (n is a positive integer satisfying n ≦ m) is about 1 to (m−
n + 1), and the branching ratio of the second splitter is about n
2. The loop type optical fiber network subscriber communication system according to claim 1, wherein the communication system is a one-to-one communication system. 3. A multi-splitter is connected to a multiplexer gathering end of the demultiplexer / multiplexer, and a plurality of subscriber units are connected via the multi-splitter. 3. The loop type optical fiber network subscriber system according to item 2. 4. A media converter optical end is connected to a multiplexer collecting end of the splitter / multiplexer, and a radio access base station is connected to a media converter electrical end via a hub. A loop type optical fiber network subscriber system according to claim 1 or 2. 5. A media converter optical end is connected to a multiplexer collecting end of the splitter / multiplexer, and a metallic cable is connected to a media converter electrical end via a hub, and an end of the metallic cable is connected. 3. The loop-type optical fiber network subscriber communication system according to claim 1, wherein a subscriber device is connected to the subscriber system. 6. A multi-splitter and a medium are connected to a collecting end of another demultiplexer / multiplexer, and to a collecting end of the other demultiplexer / multiplexer. Connecting the optical end of the converter to a subscriber unit via the multi-splitter, the electrical end of the media converter, the connection of a radio access station via a hub, the electrical end, 3. A loop type optical fiber network subscriber system according to claim 1, wherein at least two of the three connections of the subscriber unit via the hub and the metallic cable are connected. Communications system.