JP3741814B2 - Optical space transmission method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical space transmission method and apparatus for constructing a local area network (hereinafter referred to as LAN) called Ethernet (registered trademark) by optical space transmission. More specifically, the LAN is suitable for a local communication network in an office or the like called ten base tee (10 BASE-T), and reliability for easily constructing the LAN by optical space transmission. It is intended to provide a novel method and apparatus with high cost.
[0002]
[Prior art]
There are many well-known documents for easily constructing a LAN by optical space transmission.
Reference 1 JP 59-235 A
Reference 2 JP 59-79650 A
Reference 3 JP-A-60-180230
Reference 4 Japanese Patent Laid-Open No. 61-23427
Reference 5 JP-A-2-16822
[0003]
Reference 1 discloses a system in which a light reflecting means is provided on a ceiling or the like, and an optical signal is reflected and received by an optical receiver. There, a spherical plate, a planar light reflecting plate, and a planar light diffusing plate are used as the light reflecting means.
[0004]
Reference 2 is a signal transmission system in which a light reflecting mirror is provided on a ceiling or the like, a lens is provided in an optical transmission / reception unit, a directivity angle of transmission light is narrowed, reception light is condensed and n-to-n transmission is performed. Is disclosed.
[0005]
Reference 3 discloses an optical space transmission device in which a satellite head having a plurality of light receiving elements is provided on a ceiling or the like and performs optical communication with a terminal head.
[0006]
Reference 4 discloses an information transmission device using a ceiling, a wall, and a floor itself as a reflector.
[0007]
Reference 5 discloses an apparatus using a ceiling or the like as a diffuse reflection surface and using a transmission lens and a reception lens for an optical transceiver.
[0008]
The optical LAN disclosed in these references is summarized as follows: a satellite type that communicates with another terminal or a transmission line connected to the satellite via a satellite provided on the terminal side and the ceiling, and a reflective surface of the ceiling It is divided into the light diffuse reflection type using Reference 3 is a satellite type, and References 1, 2, 4 and 5 belong to the light diffuse reflection type.
[0009]
In the satellite type, the light output of the satellite had to be below a certain value. This is because the optical signal emitted by the satellite itself is reflected by a wall or the like, so that it is erroneously received as an optical transmission signal from the terminal side and output to the Ethernet. When this situation occurs, it is determined that a signal collision (collision) has occurred in the Ethernet, the collision detection function operates, and communication stops. If this phenomenon occurs frequently, the LAN becomes unable to communicate.
[0010]
Therefore, in order to prevent this phenomenon, it is necessary to make the light output of the satellite as small as possible. The decrease in optical output increases the occurrence of errors due to optical noise. Therefore, the satellite has to narrow the optical directivity angle of the transmission signal, and the optical axis alignment accuracy with the optical transceiver on the terminal side (hereinafter simply referred to as a node) is required, and the handling is troublesome. .
[0011]
In the case of the light diffuse reflection type, when the reflection of the ceiling or the wall material itself is used as in References 4 and 5, it is not necessary to provide a special reflector. The intensity of reflected light greatly depends on the material. When a plurality of nodes transmit light simultaneously in one room provided with many nodes, a collision occurs, and in Ethernet, the collision detect function operates and communication stops.
[0012]
Therefore, in order to reveal a state where the collision detection function in Ethernet does not operate, all other nodes in the room receive the optical transmission output of one node regardless of the material of the light diffusing reflection surface. Thus, it is necessary to prevent these other nodes from performing optical transmission during the period in which the optical transmission output exists.
[0013]
At the same time, each node is required to transmit an optical signal from one node to one or a plurality of other nodes without causing error data and to be received by diffuse reflection. A large optical transmission output was required.
[0014]
That is, in Ethernet, when each node detects a carrier (optical signal), nodes other than the node that optically transmits the carrier do not perform optical transmission during the presence, and optical transmission occurs when the carrier is not detected. Therefore, it is required that a plurality of nodes realize carrier sense multiple access (CSMA) using a LAN.
[0015]
[Problems to be solved by the invention]
In order to realize the CSMA function in Ethernet, adopting the satellite type or the light diffuse reflection type has the following problems.
[0016]
In the satellite type, the optical output of each node is reduced to prevent the occurrence of collision, and the optical directivity is sharpened. Therefore, the optical signal (carrier) of one node outputting the optical transmission signal is transmitted to the other node. It cannot be detected directly. If a carrier is to be detected, it is necessary to notify the existence of the carrier from the satellite to other nodes. For this reason, the satellite function is complicated, and therefore it is not suitable for realizing the CSMA function.
[0017]
Since the light diffuse reflection type uses a light diffuse reflection surface such as a ceiling material or wall material, a large light transmission output is required for each node in order to receive without generating error data regardless of the material. The problem was left.
[0018]
[Means for Solving the Problems]
In an optical local area network (LAN; commonly called Ethernet), optical transmission / reception for data communication is performed between a satellite and a node, and one node outputs an optical signal. Carrier detection to be performed is performed by diffuse reflected light from a ceiling material or wall material near the satellite, and other nodes do not output optical signals during the carrier detection period, thereby realizing CSMA.
[0019]
The light output from the node is radiated to the satellite and the surrounding ceiling. However, since there is a satellite near the center of the light emission area (signal transmission area), optical communication can be performed without causing errors in data. The diffuse reflected light from a fairly wide area around the satellite (carrier detection area) is only used for carrier sensing of other nodes, so even if the diffuse reflected light is weak, data It has nothing to do with the occurrence of errors. That is, the diffuse reflected light is not used for data communication.
[0020]
Therefore, satellites are used for data communication, and diffusely reflected light that is not used for data communication is used for carrier sense. Therefore, even if the optical signal output of the node is small, the distance from the satellite is sufficiently large. And CSMA / CD (CD: collision detection, collision detection) using light in a wide communication area.
[0021]
Further, if the present invention is used, full duplex communication is also possible. In full-duplex communication, when the satellite receives the transmission data from the node, the same data is returned to the node, and if it matches the transmission data at the node, it is necessary to recognize that it has been correctly transmitted.
[0022]
In the conventional light diffusion type, the light transmission signal from the node diffusely reflected by the ceiling material has a strength that can be sufficiently recognized as optical communication, and there is a possibility that this may be mistaken as a return signal, In the present invention, the diffusely reflected light is used only for the purpose of carrier sense and not used for data communication. Therefore, it is sufficient to output a sufficiently small light energy from the node.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a conceptual diagram of an embodiment of the present invention. Each of the nodes 3a to 3d is connected to a personal computer that is a terminal, for example, which is not illustrated by transmission lines 4a to 4d.
[0024]
Now, one node 3 b is outputting the transmission light 5. The transmission light 5 is radiated toward the satellite 7 provided on the ceiling. The satellite 7 includes an optical transceiver, and is connected to the LAN by a transmission line 9.
[0025]
The transmission light 5a forms a wide carrier detection region 12 (upper right hatched portion) on the ceiling around the satellite 7. The diffuse reflected light 6 reflected by the ceiling material reaches the nodes 3a, 3c, 3d. Although this diffusely reflected light 6 cannot be used as a data signal because the light energy is small, the diffuse reflected light 6 has sufficient intensity for carrier sense to detect a state in which a certain node (3b in the figure) outputs the transmission light 5. Therefore, the node 3a, 3c, 3d other than the node 3b does not transmit during the carrier sense operation.
[0026]
The signal transmission region 11 (lattice hatched portion) close to the center of the carrier detection region 12 is a ceiling portion irradiated with the transmission light 5b. If the satellite 7 is inside the signal transmission region 11, the transmission light 5c is converted into data. It can be used as an optical signal that does not cause an error. During the period when the optical transmitter included in the node 3b outputs the transmission light 5, the function of the optical receiver included in the node 3b does not operate even when the diffuse reflected light 6 is received.
[0027]
When the satellite 7 receives the signal from the transmission line 9 or responds to the optical transmission from the node 3b and confirms that there is no transmission from all the nodes 3a to 3d, it transmits the optical signal used for data communication. However, the optical signal from the satellite 7 can be received by all the nodes 3a to 3d, and the optical signal is transmitted from all the nodes 3a to 3d during the transmission of the optical signal of the satellite 7 by the carrier sense function. Can not.
[0028]
As described above, the period during which the satellite 7 and all the nodes 3a to 3d are not transmitting optical signals is detected by the carrier sense, and can be accessed by transmitting optical signals from any of the nodes 3a to 3d and the satellite 7. Therefore, the CSMA (Carrier Sense Multiple Access) function can be exhibited without causing a collision.
[0029]
【Example】
FIG. 2 is a conceptual diagram showing the system connection of the present application shown in FIG. Here, the same symbols are attached to the same components shown in FIG.
[0030]
In FIG. 2, the data to be transmitted from the personal computer PC2 is transmitted to the node 3b through the transmission line 4b. When the node 3b confirms that no carrier exists, the satellite 7 provided on the ceiling 15 transmits data used for data communication. Send out light 5. The node 3a that has detected (carrier sense) diffuse reflection light 6 that is not used for data communication from the carrier detection region 12 (not shown) surrounded by the transmission light 5a on the outer periphery of the transmission light 5 transmits the transmission light. It is not possible.
[0031]
The node 3a is connected to the hub 20 via a transmission line 4a, and is connected to many personal computers PC1a to PC1d by transmission lines 21a to 21d. When the carrier sense is lost, the data from the personal computers PC1a to PC1d can be optically transmitted for data communication via the node 3a.
[0032]
FIG. 3 shows another conceptual diagram in which the present application shown in FIG. 1 is system-connected. Here, the same components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.
[0033]
In FIG. 3, a server 30 serving as a master unit is connected to a printer 35 by a transmission line 36 via a switching hub 25 connected by a transmission line 31, and further connected to satellites 7a to 7c by transmission lines 9a to 9c. Under the control of the server 30, optical communication from (to) many nodes 3 a to 3 f is performed, and data is output to the printer 35 as necessary.
[0034]
【The invention's effect】
As apparent from the above description, the present invention can exert the following effects.
[0035]
1) Since satellites are used for data communication with nodes without using diffuse reflected light from ceiling or wall materials, the error rate of data is extremely small, and the optical transmission output of the nodes Can be small.
[0036]
2) The carrier sense for detecting that one node is performing optical transmission uses the diffuse reflected light from the carrier detection area of the transmitted light transmitted in the direction of the satellite. There is no need to output from the satellite an optical signal for notifying other nodes that the optical signal is being output.
[0037]
3) Satellites only need to be inside the signal transmission area, so it is convenient to install the nodes without requiring direction accuracy.
[0038]
4) Since diffused reflected light is not used for optical data communication but only for carrier sense, full-duplex communication by light is possible between satellites and nodes.
[0039]
5) Satellites are used for optical data communication, and diffusely reflected light is used for carrier sensing to ensure collision avoidance. Therefore, even if the optical signal output of the node is small, the distance to the satellite is small. It was possible to achieve sufficient optical CSMA over a wide communication area.
[0040]
Therefore, the effect of the present invention is extremely great.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating an example of an embodiment of optical space transmission according to the present invention.
FIG. 2 is a connection conceptual diagram showing an example of the entire system according to the present invention.
FIG. 3 is a connection conceptual diagram showing another example of the entire system according to the present invention.
[Explanation of symbols]
3 Node 4 Transmission line 5 Transmitted light 6 Diffuse reflected light 7 Satellite 9 Transmission line 11 Signal transmission area 12 Carrier detection area 15 Ceiling 20 Hub 21 Transmission line 25 Switching hub 30 Server 31 Transmission line 35 Printer 36 Transmission line PC Personal computer

Claims (6)

In an optical space transmission method for optical transmission / reception between the satellite (7) and a plurality of nodes (3a to 3d),
When one node (3b) of the plurality of nodes (3a to 3d) outputs transmission light (5) used for data communication in the direction of the satellite (7), the satellite (7) The other nodes (3a, 3c, 3d) of the plurality of nodes (3a to 3d) detected diffuse reflected light (6) that is not used for data communication from the carrier detection region (12) that is the peripheral region. Sometimes the other nodes (3a, 3c, 3d) perform a carrier sense operation to prevent optical transmission,
An optical space transmission method in which the satellite (7) optically receives transmission light (5) used for data communication from the one node (3b) and performs data communication operation. While the satellite (7) is receiving the transmission light (5) used for the data communication from the one node (3b), the satellite (7) does not perform an optical transmission operation,
The optical space transmission method according to claim 1, wherein during the optical transmission of the satellite (7), all the nodes (3 a to 3 d) do not perform an optical transmission operation by optically receiving the satellite. The optical space transmission method according to claim 1, wherein the satellite (7) is provided inside a signal transmission region (11) which is a region having a high light intensity used for data communication in the carrier detection region (12). . In an optical space transmission device for optical transmission and reception between the satellite means (7) and the plurality of node means (3a to 3d),
The plurality of node means (3a to 3d) transmit light used for data communication in the direction of the satellite means (7) by one node means (3b) of the plurality of node means (3a to 3d). When the diffuse reflected light (6) that is not used for data communication from the carrier detection area (12), which is the peripheral area of the satellite means (7), is detected while other satellite means (3a) is output. , 3c, 3d) have carrier sensing means for preventing optical transmission,
The satellite means (7) includes optical data receiving means for optically receiving transmission light (5) used for data communication from the one node means (3b) for optical data communication. Transmission equipment. While the satellite means (7) is receiving the transmission light (5) used for the data communication from the one node (3b), the satellite means (7) does not perform the optical transmission operation,
5. The optical space transmission device according to claim 4, wherein all of the node units (3 a to 3 d) do not perform an optical transmission operation by optically receiving the satellite unit (7) during optical transmission. The optical space transmission according to claim 4, wherein the satellite means (7) is provided inside a signal transmission region (11) which is a region having a high light intensity used for data communication in the carrier detection region (12). apparatus.

Images