JP2003179555A - Light signal collision detecting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To construct a wide area optical network at a lower cost by employing techniques and parts, employed in a conventional LAN, as much as possible. <P>SOLUTION: A reflector 301 is provided between communication terminals 110, 120, and photocouplers 21, 22. When the light signal is transmitted from the communication terminals 110, 120, the light signals transmitted from the communication terminals 110, 120 are branched respectively by the photocouplers 31, 32. A photocoupler 33 composes the branched light signals, respectively outputted from the photocouplers 31, 32, to produce a composite light signal. The composite light signal is branched by another photocoupler 34 and, thereafter, the branched signals are composed by other photocouplers 35, 36 into light signals received by respective communication terminals 110, 120 to supply the same to the communication terminals 110, 120. Respective communication terminals 110, 120 monitor the composite light signals turned by a reflector 301 to detect collision and re-transmit the data. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal collision detection system, and more specifically, a plurality of communication terminals are star-connected to a hub, and the plurality of communication terminals share a shared optical signal via the hub. The present invention relates to an optical signal collision detection system that detects collision of optical signals transmitted from a plurality of communication terminals and controls retransmission of optical signals in a medium sharing type network that transmits optical signals using a transmission line. Especially LAN
It can be suitably used for collision detection of optical signals from a plurality of terminals in a data communication network such as (local area network).

[0002]

2. Description of the Related Art In a medium sharing type LAN, since a plurality of communication terminals share a transmission path, there is a problem that when a plurality of communication terminals simultaneously transmit data, the data collide with each other and are destroyed. To deal with this, CSMA is generally used.
/ CD (Carrier Sense Multipl
e Access with Collision D
Emission method is used. In this system, the communication terminal has a function of inspecting the received data while transmitting the data, and retransmitting the transmitted data when a collision is detected when the data different from the transmitted data is received.

On the other hand, FTTH (Fiber To Th)
In a wide area optical network such as e Home),
In terms of cost, PDS (Passive Double
PON (Passive Op) such as eStar method
A form in which a plurality of terminals share an optical transmission line via an optical coupler is generally adopted by the technical network) technology. In this case, there is a problem that it takes time to detect a collision because the terminals are farther than expected on the LAN. For example, when a plurality of terminals simultaneously transmit optical signals in the PDS system, optical signal collision occurs in the optical coupler. In order for each terminal to detect this collision, the optical signals that have collided in the optical coupler arrive at the station. After that, it takes time to return to each terminal. In other words, roughly speaking, between the terminal and the station (several kilometers)
It takes time for the optical signal to make a round trip. Therefore, it is difficult to directly use the CSMA / CD method in such a wide area optical network. Therefore, in the wide area optical network, a method of avoiding the collision itself by multiplexing the transmission data from the communication terminals in time division is used.

[0004]

In order to reduce the cost, it is generally effective to use the technology / parts used in a larger market. This is the LA
The same applies to N and wide area optical networks. That is, it is possible to reduce the cost for constructing the wide area optical network by directly using the technology / parts used in the huge LAN market for the wide area optical network.

However, in the wide area optical network as described above, it is necessary to introduce the special technique for avoiding the collision as described above. This is a factor of increasing costs in wide area optical networks.

Therefore, it is an object of the present invention to provide conventional LA
It is to provide an optical signal collision detection system capable of constructing a wide area optical network at a lower cost by using the technology and components used in N as much as possible.

[0007]

According to a first aspect of the present invention, a plurality of communication terminals are star-connected to a hub via an optical transmission line, and the plurality of communication terminals are shared via the hub. It is an optical signal collision detection system that detects the collision of the optical signals transmitted from a plurality of communication terminals and controls the retransmission of the optical signals in the medium sharing type network that transmits the optical signals using the optical transmission path. The hub is provided with a reflector that returns a combined optical signal obtained by combining the optical signals transmitted from the plurality of communication terminals to each of the plurality of communication terminals, and each communication terminal monitors the combined optical signal from the reflector. A collision detection unit that detects a collision of the optical signal and a retransmitting unit that retransmits the optical signal when the collision of the optical signal is detected are provided.

As described above, according to the first aspect of the invention, since the combined optical signal obtained by combining the optical signals from the respective communication terminals can be returned to the respective communication terminals by the reflector, the CSMA / CD system can be applied to the wide area optical network. It becomes possible to apply the medium access control according to the above, and as a result, it becomes possible to use the technology / parts used in the large market called LAN in the layer above the MAC sublayer of the communication terminal, and to further improve the wide area optical network. It can be built at low cost. Note that the communication terminal includes any device having a communication function, for example, a device such as a media converter that provides a bridge function between an optical transmission line and another transmission line by converting an optical signal.

A second invention is characterized in that, in the first invention, the reflector is constituted by a passive element which does not require an electric device.

As described above, according to the second invention, it is not necessary to supply power to the reflector, and the reflector can be miniaturized.

In a third aspect based on the first aspect, the reflector includes a plurality of first optical branching means for branching the optical signals from the plurality of communication terminals to take out a branched optical signal, and a plurality of branching optical signals. A plurality of first optical multiplexing means for multiplexing the signals to generate a combined optical signal, second optical branching means for branching the combined optical signal, and a plurality of combined optical signals branched by the second optical branching means are provided. A plurality of second optical multiplexing means for respectively multiplexing the optical signals received by the communication terminal.

As described above, according to the third aspect of the invention, the optical signals from a plurality of communication terminals are optically branched and combined to easily generate a combined optical signal and return it to the communication terminal. it can.

According to a fourth aspect of the present invention, in the first aspect of the present invention, between the plurality of communication terminals and the reflector, the optical signals from the plurality of communication terminals are multiplexed and transmitted to the shared optical transmission line.
And a plurality of first optical branching means for branching an optical signal from the shared optical transmission line and sending the branched optical signals to a plurality of communication terminals, respectively, and the reflector is a first optical multiplexing means. Before branching the second optical branching means for branching the optical signal multiplexed by the above-mentioned to take out it as a combined optical signal and the combined optical signal taken out by the second optical branching means for the first optical branching means Second optical multiplexing means for multiplexing the optical signal from the shared optical transmission line.

As described above, according to the fourth aspect of the present invention, the optical signals from a plurality of communication terminals are optically branched / multiplexed to easily generate a combined optical signal and return it to the communication terminal. it can. Further, the first optical multiplexing means and the first
Since the conventional PON technology can be used as it is for the optical branching means, the structure of the reflector is simplified and the cost is further reduced. Further, since each communication terminal can monitor an optical signal obtained by branching the optical signal itself supplied to the shared optical transmission line as a combined optical signal, it is possible to easily and accurately detect a collision.

A fifth invention is characterized in that, in the first invention, each communication terminal functions as a media converter for converting an optical signal to bridge with another transmission path.

As described above, according to the fifth aspect of the invention, even if the user and the hub are far apart from each other, the time required for retransmission from the occurrence of a signal collision is short, so that good communication efficiency can be maintained. You can

In a sixth aspect based on the first aspect, the reflector has a wavelength of an optical signal transmitted from the plurality of communication terminals to the hub and a wavelength of an optical signal transmitted from the hub to the plurality of communication terminals. When different, the wavelength conversion means for converting the wavelength of the combined optical signal from the former wavelength to the latter wavelength is included.

As described above, according to the sixth aspect of the invention, each communication terminal monitors the combined optical signal to detect the optical signal even if the wavelength of the optical signal is different between when transmitting and when receiving. It is possible to detect collision and retransmit.

According to a seventh aspect of the invention, a plurality of communication terminals are connected in a star shape via an optical transmission line, and optical signals from the plurality of communication terminals are supplied to a shared optical transmission line shared by the plurality of communication terminals. In addition, it is a hub that supplies the optical signal from the shared optical transmission line to each of the plurality of communication terminals, and the combined optical signal obtained by combining the optical signals transmitted from the plurality of communication terminals with each of the plurality of communication terminals. It is equipped with a reflector that folds back.

As described above, according to the seventh aspect of the invention, since the combined optical signal obtained by combining the optical signals from the respective communication terminals can be returned to each communication terminal by the reflector, the CSMA / CD system can be applied to the wide area optical network. It becomes possible to apply the medium access control according to the above, and as a result, it becomes possible to use the technology / parts used in the large market called LAN in the layer above the MAC sublayer of the communication terminal, and to further improve the wide area optical network. It can be built at low cost.

An eighth invention is characterized in that, in the seventh invention, the reflector is constituted by a passive element which does not require an electric device.

As described above, according to the eighth aspect of the invention, it is not necessary to feed power to the reflector, and the reflector can be miniaturized.

In a ninth aspect based on the seventh aspect, the reflector includes a plurality of first optical branching means for branching optical signals from a plurality of communication terminals to extract a branched optical signal, and a plurality of branching optical signals. A plurality of first optical multiplexing means for multiplexing the signals to generate a combined optical signal, second optical branching means for branching the combined optical signal, and a plurality of combined optical signals branched by the second optical branching means are provided. A plurality of second optical multiplexing means for respectively multiplexing the optical signals received by the communication terminal.

As described above, according to the ninth aspect of the present invention, the optical signals from a plurality of communication terminals are optically branched / multiplexed so that a composite optical signal can be easily generated and returned to the communication terminal. it can.

In a tenth aspect based on the seventh aspect, between the plurality of communication terminals and the reflector, the optical signals from the plurality of communication terminals are multiplexed and sent to the shared optical transmission line. An optical multiplexing means and a plurality of first optical branching means for branching an optical signal from the shared optical transmission path and sending the branched optical signals to a plurality of communication terminals are provided, and the reflector is a first optical multiplexing means. Second optical branching means for branching the optical signal multiplexed by the means to extract it as a combined optical signal, and combined optical signal extracted by the second optical branching means for being branched by the first optical branching means. Second optical multiplexing means for multiplexing the optical signal from the previous shared optical transmission line.

As described above, according to the tenth aspect of the present invention, the optical signals from a plurality of communication terminals are optically branched / multiplexed so that a combined optical signal can be easily generated and returned to the communication terminal. it can. Further, by utilizing the first optical multiplexing means and the first optical branching means, the structure of the reflector is simplified and the cost is reduced. Further, since each communication terminal can monitor an optical signal obtained by branching the optical signal itself supplied to the shared optical transmission line as a combined optical signal, it is possible to easily and accurately detect a collision.

In an eleventh aspect based on the seventh aspect, the reflector has a wavelength of an optical signal transmitted from the plurality of communication terminals to the hub and a wavelength of an optical signal transmitted from the hub to the plurality of communication terminals. When different, the wavelength conversion means for converting the wavelength of the combined optical signal from the former wavelength to the latter wavelength is included.

As described above, according to the eleventh aspect of the invention, each communication terminal monitors the combined optical signal to detect the optical signal, even if the wavelength of the optical signal is different between when transmitting and when receiving. It is possible to detect collision and retransmit.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing the arrangement of an optical signal collision detection system according to the first embodiment of the present invention. The present embodiment is a form close to the basic concept of the present invention. In FIG. 1, the optical signal collision detection system includes communication terminals 110 and 120, a HUB 201, and optical transmission lines 411 and 41.
2, 421, 422, 501, 502. The communication terminal 110 uses the pair of optical transmission lines 411 and 412 for H
It is connected to the UB201. Similarly, the communication terminal 120 is connected to the HUB 201 by a pair of optical transmission lines 421 and 422. Further, the HUB 201 includes a pair of optical fibers 50.
1, 502 connect to a station or a higher-level device. The MAC (media access control) layers of the communication terminals 110 and 120 include a retransmitting unit 11 and a collision detecting unit 12, respectively. The HUB 201 includes optical couplers 21 and 2.
2 and a reflector 301. The reflector 301 has optical couplers 31 to 36.

The operation of the optical signal collision detection system configured as described above will be described. First, in order to facilitate understanding, the general flow of the optical signal will be described. Each of the communication terminals 110 and 120 has an electrical / optical conversion (E
/ O) and transmits the optical signal generated to the station.
The optical signals transmitted from the communication terminals 110 and 120 are supplied to the HUB 201 via the optical transmission lines 411 and 421, respectively, and finally supplied to the common optical transmission line 501 via the optical coupler 21. It is transmitted to the station through the optical transmission line 501. On the other hand, from the station to the communication terminals 110, 1
When the optical signal is transmitted to the HUB 20, the optical signal is supplied to the HUB 201 through the common optical transmission line 502, and finally connected to the communication terminals 110 and 120 via the optical coupler 22 in the HUB 201. Are supplied to the optical transmission lines 412, 422,
It is transmitted via 22 to the respective communication terminals 110 and 120. Each of the communication terminals 110 and 120 converts the received optical signal into an electrical signal by optical / electrical conversion (O / E). As described above, the network of the present embodiment is a medium sharing type network in which the plurality of communication terminals 110 and 120 share the optical transmission line 501. Therefore, in the following description, the optical transmission lines 501 and 502 are appropriately referred to as shared optical transmission lines 501 and 502.

Next, the reflector 301 characteristic of the present invention
The operation of will be described. In this embodiment, as shown in FIG. 1, a reflector 301 is provided between the communication terminals 110 and 120 and the optical couplers 21 and 22. Communication terminal 11
When the optical signals are transmitted from 0, 120 to the station, the optical signals transmitted from the communication terminals 110, 120 are branched by the optical couplers 31, 32 before being supplied to the optical coupler 21. One of the branched optical signals is supplied to the optical coupler 21, and the other branched optical signal is supplied to the optical coupler 33 as a branched optical signal. The optical coupler 33 multiplexes the branched optical signals output from the optical couplers 31 and 32 to generate a combined optical signal. This combined optical signal is branched by the optical coupler 34, and then the optical couplers 35, 36.
Thus, the optical signals received by the communication terminals 110 and 120 are multiplexed and supplied to the communication terminals 110 and 120. By such an operation of the reflector 301, each of the communication terminals 110 and 120 immediately outputs a combined optical signal obtained by multiplexing the optical signals transmitted by all the communication terminals 110 and 120 connected to the HUB 201 (the optical signal is transmitted It can be monitored (without waiting for the round trip time between the terminal and the station).

Collision detection unit 1 of each communication terminal 110, 120
When transmitting an optical signal, 2 monitors itself by transmitting the optical signal, monitoring the combined optical signal returned by the reflector 301, and comparing the optical signal transmitted from its own communication terminal with the combined optical signal. It is determined whether the data transmitted by the communication terminal is deformed due to the collision. If another communication terminal other than itself does not transmit the optical signal, the collision of the optical signals does not occur, and the data transmitted by the combined optical signal and the data transmitted by the own communication terminal are the same. If other communication terminals other than the above also transmit the optical signals at the same time, collision of the optical signals occurs in the optical coupler 21, and the data transmitted by the combined optical signal and the data transmitted by the own communication terminal do not match. become.
When the collision detection unit 12 knows that the data transmitted by its own communication terminal is deformed due to the collision, that is, when the collision is detected, it instructs the retransmission unit 11 to retransmit the data. In this way, each communication terminal 110, 120 can detect the collision and retransmit the data.

The functions of the collision detection unit 12 and the re-transmission unit 11 as described above are based on the conventional LAN as the CSMA / CD system.
Is a function that is already commonly used in. Therefore, it becomes possible to use the technology / parts used in the large market called LAN in the processing layers above the MAC sublayer of the communication terminal, and the wide area optical network can be constructed at a lower cost.

The HUB 201 has a transmitting / receiving function and a HU.
A communication function from B201 to a higher-level device or the like may be appropriately included. Also, the optical couplers 21 and 22 are not always HUs.
The HUB201 does not have to be provided inside the B201.
It may be provided outside.

In this embodiment, the case where the two communication terminals 110 and 120 are connected to the HUB 202 has been described. However, the present invention is not limited to this, and the case where three or more communication terminals are connected is the same as this embodiment. The effect of can be realized. Further, the communication terminals 110 and 120 may be any device having a communication function. For example, the communication terminal 1 shown in FIG.
As in the case of 10, 120, it may function as a media converter that provides a bridge function with another transmission line by converting an optical signal. 2 that are the same as those in FIG. 1 are designated by the same reference numerals.

Further, as shown in FIG. 3, the HUB 201 may be arranged in a station or the like. In FIG. 3, the same components as those in FIG. 1 are designated by the same reference numerals. When the HUB 201 is arranged in the station, the media converters 110, 12
0 is arranged near the HUB 201, and a device such as a communication terminal managed by a user is connected to a long-distance transmission line (not limited to an optical transmission line) connected to the media converters 110 and 120. It is common. In this case, it is possible to detect and retransmit optical signal collisions only between the media converters 110 and 120 and the HUB 201.
Therefore, it is possible to detect and retransmit optical signal collisions regardless of the conditions of the long-distance transmission lines connected to the media converters 110 and 120 and the conditions of the devices connected thereafter. In general, the CSMA / CD system has a drawback that the time required for retransmission from the occurrence of collision increases in proportion to the transmission distance, resulting in deterioration of communication efficiency. However, according to the configuration shown in FIG. 3, even if the user and the HUB 201 are far apart from each other, the communication efficiency can be kept good because the time required for the retransmission from the occurrence of the signal collision is short.

In the above description, the communication terminals 110, 1
No reference is made to the relationship between the wavelength at which the optical signal is transmitted from 20 to the station and the wavelength at which the optical signal from the station is received, but the wavelength at the time of transmission and the wavelength at the time of reception are generally clarified. There is also a system to use properly. In such a system, even if the present embodiment is applied as it is, it is not possible to detect the collision of the optical signals because the wavelength of the combined optical signal is not the receivable wavelength. Therefore, in this case, the reflector 302 shown in FIG. 4 may be used instead of the reflector 301 shown in FIG. 4, the same components as those in FIG. 1 are designated by the same reference numerals. The reflector 302 shown in FIG. 4 differs from the reflector 301 shown in FIG. 1 in that
The point is that the wavelength conversion unit 37 is provided between the optical coupler 33 and the optical coupler 34. The wavelength converter 37 determines the wavelength λt at the time of transmission.
Has a function of converting to the wavelength λr at the time of reception. As a result, the wavelength of the combined optical signal is converted from the wavelength λt to the wavelength λr and supplied to the communication terminals 110 and 120. The communication terminals 110 and 120 monitor the combined optical signal and detect the collision of the optical signals. And it becomes possible to retransmit.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
It is a block diagram showing a configuration of an optical signal collision detection system according to the embodiment of. In FIG. 5, the optical signal collision detection system includes communication terminals 110 and 120, a HUB 202, and optical transmission lines 411, 412, 421, 422, 501 and 502. The communication terminal 110 includes a pair of optical transmission lines 411,
Connected to HUB 202 by 412. Similarly, the communication terminal 120 uses the pair of optical transmission lines 421 and 422 to connect the HU
It is connected to B202. Further, the HUB 202 is connected to a station, a host device, etc. by a pair of optical fibers 501 and 502. The HUB 202 includes optical couplers 21 and 22 and a reflector 303. The reflector 303 is an optical coupler 3
It has 8,39. 5, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

Next, of the operation of the optical signal collision detection system configured as described above, the part mainly different from that of the first embodiment will be described. Although the reflector 301 is provided between the communication terminals 110 and 120 and the optical couplers 21 and 22 in the first embodiment, unlike this, in the present embodiment, the communication device 110,
A reflector 303 is provided on the side opposite to 120 (that is, the office side). When optical signals are transmitted from the communication terminals 110 and 120 to the station, these optical signals are combined by the optical coupler 21. The optical signal output from the optical coupler 21 is branched by the optical coupler 38. One of the branched optical signals is supplied to the shared optical transmission line 501 as a transmission signal to the station, and the other of the branched optical signals is supplied to the optical coupler 39 as a combined optical signal to be returned to the respective communication terminals 110 and 120. To be done. The optical coupler 39 multiplexes the combined optical signal and the optical signal from the station. The optical signal output from the optical coupler 39 is supplied to the optical coupler 22 and branched.
The respective branched optical signals are transmitted to the respective communication terminals 110, 1
20. By such an operation of the reflector 303, the communication terminals 110 and 120 can be connected to the HUB 202.
Immediately (without waiting for the time for the optical signal to make a round trip between the communication terminal and the station) to immediately monitor the combined optical signal obtained by multiplexing the optical signals transmitted by all the communication terminals 110 and 120 connected to the communication terminal. You can In each communication terminal 110, 120,
Similar to the first embodiment, collision detection and retransmission are performed based on the combined optical signal.

As described above, according to the second embodiment,
Similar to the first embodiment, it is possible to use a technology / component that is used in a large market called LAN in the processing layers above the MAC sublayer of the communication terminal, and construct a wide area optical network at a lower cost. be able to. Furthermore, in the second embodiment, the conventional PON technology can be used as it is for the optical couplers 21 and 22, and as is apparent from the figure, the reflector configuration is different from that in the first embodiment. Since it is simplified, the cost can be further reduced. Furthermore, in the second embodiment,
Since each of the communication terminals 110 and 120 can monitor an optical signal obtained by branching the optical signal itself supplied to the shared optical transmission line 501 as a combined optical signal, it is possible to easily and accurately detect a collision. . This is because, in the first embodiment, the optical signal itself (that is, the output of the optical coupler 21) supplied to the shared optical transmission line 501 is not monitored, but each optical signal before being multiplexed in the optical coupler 21 is optically monitored. Since the combined optical signal generated by being separately combined by the coupler 33 is monitored, the combined optical signal actually monitored by the shared optical transmission line 501 is monitored due to the influence of the difference in transmission delay. This is because there may be a gap between That is, even when the optical signals output from the optical couplers 31 and 32 in FIG. 1 are input to the optical coupler 33 at the same time, the optical signals output from the optical couplers 31 and 32 are input to the optical coupler 21. This is because there is no guarantee that they will be input at exactly the same time.

The HUB 202 has a transmitting / receiving function and a HU.
A communication function from B202 to a higher-level device may be appropriately included. Also, the optical couplers 21 and 22 are not always HUs.
The HUB202 does not have to be provided inside the B202.
It may be provided outside. Also in HUB202 3
Even if more than one communication terminals are connected, the same effect as this embodiment can be realized. In addition, the communication terminals 110 and 120
May be any device having a communication function. For example, it may function as a media converter that provides a bridge function with another transmission line by converting an optical signal. Further, the HUB 202 may be arranged in the station or the like.

Further, in a system in which the wavelength for transmission and the wavelength for reception are clearly used, the collision of the optical signals is detected because the wavelength of the combined optical signal is not the receivable wavelength even if this embodiment is applied as it is. Can not do it.
Therefore, in this case, the reflector 304 shown in FIG. 6 may be used instead of the reflector 303 shown in FIG. In FIG. 6, the same components as those in FIG. 5 are designated by the same reference numerals. The reflector 304 shown in FIG. 6 is different from the reflector 303 shown in FIG. 5 in that a wavelength conversion unit 37 is provided between the optical coupler 38 and the optical coupler 39. Wavelength converter 3
Reference numeral 7 has a function of converting the wavelength λt at the time of transmission into the wavelength λr at the time of reception. As a result, the wavelength of the combined optical signal is the wavelength λt.
Is converted to a wavelength λr and supplied to each communication terminal 110, 120, and each communication terminal 110, 120 can monitor the combined optical signal and detect and retransmit the optical signal collision.

In the above description of the embodiment, the HUB2
Although 01 and 202 are configured with a plurality of optical couplers, a part of them is replaced with an electrical method to combine signals.
You may branch. However, by using passive elements such as optical couplers that do not require power supply,
This is preferable because the size of 201 and 202 can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical signal collision detection system according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an application example of the first embodiment.

FIG. 3 is a block diagram showing a configuration of another application example of the first embodiment.

FIG. 4 is a block diagram showing a configuration of a modified example of a reflector when the first embodiment is applied to a system that uses different wavelengths for transmission and reception.

FIG. 5 is a block diagram showing a configuration of an optical signal collision detection system according to a second exemplary embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a modified example of a reflector when the second embodiment is applied to a system that uses different wavelengths for transmission and reception.

[Explanation of symbols]

11 ... Retransmission unit 12 ... Collision detection units 21, 22, 31-36, 38, 39 ... Optical coupler 37 ... Wavelength conversion units 110, 120 ... Communication terminals (communication terminals as media converters) 201, 202 ... HUB 301-304 ... Reflectors 411, 412, 421, 422 ... Optical transmission lines 501, 502 ... Optical transmission line (shared optical transmission line)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuki Maeda             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5K002 AA01 AA03 BA05 CA05 DA04                       DA05 DA12 EA05 FA01                 5K033 DA15 DB02

Claims (11)

[Claims] 1. A medium in which a plurality of communication terminals are star-connected to a hub via an optical transmission line, and the plurality of communication terminals transmit optical signals via the hub using a shared optical transmission line. In a shared network, an optical signal collision detection system that detects the collision of optical signals transmitted from the plurality of communication terminals and performs retransmission control of the optical signals, wherein the hub is transmitted from the plurality of communication terminals. Collision detecting means for detecting a collision of optical signals by monitoring the combined optical signals from the reflectors, each of the communication terminals including a reflector that returns a combined optical signal obtained by combining the optical signals to each of the plurality of communication terminals. And an optical signal collision detection system, comprising: a retransmitting unit that retransmits the optical signal when a collision of the optical signal is detected. 2. The reflector is constituted by a passive element which does not require an electric device,
The optical signal detection system according to claim 1. 3. The reflector combines a plurality of first optical branching means for branching optical signals from the plurality of communication terminals to extract a branched optical signal, and multiplexing the plurality of branched optical signals for the branching. A first optical combining unit that generates a combined optical signal, a second optical branching unit that branches the combined optical signal, and a combined optical signal that is branched by the second optical branching unit, the plurality of communication terminals. 2. The optical signal collision detection system according to claim 1, further comprising a plurality of second optical multiplexing means for respectively multiplexing optical signals received by the optical signal reception apparatus. 4. A first optical multiplexing unit that multiplexes optical signals from the plurality of communication terminals between the plurality of communication terminals and the reflector and sends the multiplexed optical signals to the shared optical transmission line, A plurality of first optical branching means for branching an optical signal from the shared optical transmission line and sending the branched optical signals to the plurality of communication terminals respectively, wherein the reflector is multiplexed by the first optical multiplexing means. Before dividing the combined optical signal extracted by the second optical branching means and the first optical branching means into second optical branching means for branching the extracted optical signal as the combined optical signal. The optical signal collision detection system according to claim 1, further comprising a second optical multiplexing unit that multiplexes an optical signal from the shared optical transmission line. 5. The optical signal collision detection system according to claim 1, wherein each of the communication terminals functions as a media converter that converts an optical signal to bridge with another transmission path. 6. The reflector is characterized in that when the wavelengths of the optical signals transmitted from the plurality of communication terminals to the hub are different from the wavelengths of the optical signals transmitted from the hub to the plurality of communication terminals. The optical signal collision detection system according to claim 1, further comprising wavelength conversion means for converting the wavelength of the combined optical signal from the former wavelength to the latter wavelength. 7. A plurality of communication terminals are connected in a star shape via an optical transmission line, and optical signals from the plurality of communication terminals are supplied to a shared optical transmission line shared by the plurality of communication terminals, and A hub for supplying an optical signal from a shared optical transmission line to each of the plurality of communication terminals, and returning a combined optical signal obtained by combining the optical signals transmitted from the plurality of communication terminals to each of the plurality of communication terminals. Hub with reflector means. 8. The reflector is constituted by a passive element which does not require an electric device,
The hub according to claim 7. 9. The reflector combines a plurality of first optical branching means for branching optical signals from the plurality of communication terminals to extract a branched optical signal, and multiplexing the plurality of branched optical signals for the branching. A first optical combining unit that generates a combined optical signal, a second optical branching unit that branches the combined optical signal, and a combined optical signal that is branched by the second optical branching unit, the plurality of communication terminals. 8. The hub according to claim 7, further comprising a plurality of second optical multiplexing means for respectively multiplexing optical signals received by the second optical multiplexing means. 10. A first optical multiplexing unit that couples optical signals from the plurality of communication terminals and sends the multiplexed optical signals to the shared optical transmission line between the plurality of communication terminals and the reflector.
A plurality of first optical branching means for branching the optical signal from the shared optical transmission path and sending out to the plurality of communication terminals are provided, and the reflector is provided by the first optical multiplexing means. Second optical branching means for branching the combined optical signal to take out the combined optical signal, and the combined optical signal taken out by the second optical branching means for being branched by the first optical branching means. 8. The hub according to claim 7, further comprising a second optical multiplexing unit that multiplexes the optical signal from the shared optical transmission line before the optical multiplexing. 11. The reflector, wherein the wavelength of an optical signal transmitted from the plurality of communication terminals to the hub is different from a wavelength of an optical signal transmitted from the hub to the plurality of communication terminals. The hub according to claim 7, further comprising wavelength conversion means for converting the wavelength of the combined optical signal from the former wavelength to the latter wavelength.