JP2002198915A - Optical transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission system which maintains the quality of transmission easily and in good condition. SOLUTION: An optical transmission system composed of a transmission node 14a-14d which transmits an optical signal, a common optical path 1 which transmits the optical signal from the transmission node, a reception node 15a-15d which receives the optical signal from the common optical path and a transmission control part 12 which is connected to each transmission and reception node. The transmission control part 12 stores the optical characteristic of the transmission path and controls when transmits the optical signal at least either the optical signal strength which should be transmitted at the transmission node or the amplify ratio of the signal received at the reception node based on the optical characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission system for transmitting an optical signal via a light guide.

[0002]

2. Description of the Related Art In recent years, with the development of ultra-large-scale integrated circuits,
The circuit functions of circuit boards used in data processing systems have increased significantly. As the number of signal connections to each circuit board increases as this circuit function increases, the data bus board that connects each circuit board with a bus structure adopts a parallel architecture that requires a large number of connectors and connection lines. ing. The operation speed of the parallel bus is improved by promoting the parallelization of the connection lines by multi-layering and miniaturization. However, the processing speed of the system may be limited by the operation speed of the parallel bus due to the signal delay caused by the capacitance between the connection lines or the connection line resistance. In addition, the electromagnetic noise (E
MI: Electromagnetic Interf
issue) is also a significant constraint on improving the processing speed of the system. Therefore, optical interconnections, which have been spotlighted mainly in trunk systems, have been applied to the field of electrical wiring between substrates.

[0003] Among the various types of optical interconnection technologies that have been proposed in the past, the most widespread one at present is trunk line communication using a single mode optical fiber. However, the cost of the equipment required for these systems is expensive, and optical interconnection has not yet penetrated the consumer market.

As a low-cost and highly expandable optical interconnection, for example, Japanese Patent Application Laid-Open No. 10-123350 proposes an optical bus technique. This technology uses a low-cost flat light guide path made of resin, and has a diffusion optical system provided therein to broadcast light to multiple points.

[0005]

However, in the technique using a flat light guide as described above, in addition to the deterioration of the element and the change in the light intensity depending on the surrounding environment, the light using the light guide or the transmission line itself is not sufficient. There is a change in intensity. That is, when transmitting one optical signal to many receivers,
This is because it is difficult in principle to distribute light uniformly, and a certain degree of variation occurs.

As a method of compensating for a change in light intensity in order to maintain transmission quality, as described in, for example, Japanese Patent Application Laid-Open No. Hei 6-37719, in an optical space transmission apparatus, there is a large difference between weather conditions and transmission distances. Changes in the damping rate
Techniques for changing the amount of incident light, light receiving sensitivity, and amplification factor are known. Further, as described in Japanese Patent Application Laid-Open No. 9-93199, a technique is known in which loss information of an optical signal detected by a receiving unit is notified to a transmitting unit, and the driving condition of the light emitting element is adjusted based on the information. However, these techniques are suitable for tracking the surrounding environment and changes over time after starting transmission, but are redundant means when the state of the system is known in advance. Further, in the method of feeding back information detected by the receiving unit, there is a problem that a system is complicated due to the feedback, and that it takes time to start transmission.

As described above, at present, there is no simple method that cannot be ignored from the initial state of transmission and compensates for a change in light intensity that is different from a change in the surrounding environment or a change with time. is the current situation.

Accordingly, it is an object of the present invention to provide an optical transmission system that can maintain transmission quality simply and well.

[0009]

The object of the present invention is to provide a transmitting node for transmitting an optical signal, a light guide for transmitting an optical signal from the transmitting node, and a receiving node for receiving an optical signal from the light guide. This is achieved by an optical transmission system including a transmission control unit that stores optical characteristics of the light guide path and controls at least one of the transmitting node and the receiving node based on the optical characteristics when transmitting an optical signal. Here, the optical characteristics are physical characteristics that affect when light propagates in the light guide path, and include, for example, an attenuation rate of an optical signal. This varies depending on the refractive index distribution of the light guide path and the light quantity distribution when light is diffused.

The transmission control unit can control, for example, the intensity of an optical signal to be transmitted at the transmitting node, and can control the amplification factor of a signal received at the receiving node. Further, the light guide path may include a diffusion optical system for expanding a traveling direction of light.
At least one of the light guide path and the transmission node and / or the light guide path and the reception node may be connected by an optical fiber.

A transmitting node according to the present invention transmits an optical signal via a light guide, and the intensity of the optical signal to be transmitted based on the optical characteristics of the light guide stored in advance when transmitting the optical signal. Is controlled. The receiving node according to the present invention receives an optical signal via a light guide, and controls an amplification factor of a received signal based on optical characteristics of a light guide stored in advance when receiving the optical signal. Is what you do.

An optical transmission method according to the present invention transmits an optical signal transmitted from a transmission node via a light guide path and receives the signal at a reception node. Controlling the intensity of the optical signal transmitted from the transmitting node based on, or controlling the amplification factor of the signal received at the receiving node based on the optical characteristics of the light guide when receiving the optical signal, or It controls both the intensity of the transmitted optical signal and the gain of the received signal.

With this configuration, it is possible to easily and satisfactorily maintain the transmission quality of the optical transmission system. Here, the transmission quality can be translated into a bit error rate by guaranteeing that a transmitted signal can be transmitted accurately at a desired speed. If the light quantity of the emitted light signal is attenuated for some reason and reaches a receiving unit and does not reach a predetermined light quantity, an erroneous signal may be transmitted. Can prevent this.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. FIGS. 1A and 1B are schematic diagrams each showing an example of a transmission line used in an optical transmission system according to the present invention. In the following drawings, the same reference numeral will be used when referring to the same object.

The transmission path shown in FIG. 1A includes an electro-optical conversion section 3 for converting an electric signal 2 into an optical signal 7, a first individual light guide path 4 optically coupled to the electro-optical conversion section 3, A common light guide 1 optically coupled to the first individual light guide 4, a second individual light guide 4 optically coupled to the common light guide 1, and optically to the second individual light guide 4 An optical-to-electrical conversion unit 6 that converts the optical signal 7 into the electric signal 2 is provided.

In FIG. 1A, an electric signal 2 is converted into an optical signal 7 in an electro-optical converter 3 and guided to a common light guide 1 by a first individual light guide 4. This common light guide path 1
Shows a generally rectangular flat plate shape, but the shape is not limited to this, and may be, for example, a disk shape or another polygonal shape. Further, the shape may be, for example, a sphere having a three-dimensional spread. The optical signal 7 guided to the common light guide path 1 spreads in the traveling direction, and the light reaches a range having a certain area. As shown, the first individual light guide 4 and the common light guide 1
By providing the diffusion optical system 5 at the coupling portion with the optical signal 7 and actively diffusing the optical signal 7, the optical signal 7 can be largely diffused in the common light guide path 1. A part of the propagated optical signal 7 is input to the second individual light guide path 4 facing the optical signal 7, and is converted into the electric signal 2 by the photoelectric conversion unit 6.

The transmission path shown in FIG. 1B is one in which first and second individual light guide paths 4 are arranged on the same surface of the common light guide path 1. In this example, since the optical signal 7 diffused in the common light guide path 1 is reflected at the facing surface, the optical signal 7 can be extracted from the light emitting portion on the same end surface as the light incident portion. Here, a light emitting diode, a semiconductor laser, or the like can be used for the electro-optical converter 3, and a PIN photodiode or an avalanche photodiode can be used for the opto-electric converter 6. An optical fiber made of resin or glass or an optical waveguide can be used for the individual light guide 4. When the diffusion optical system 5 is provided, a diffusion sheet such as that used for a frosted glass or a liquid crystal backlight can be used.

FIG. 2A is a plan view of the common light guide path 1, and FIG. 2B is a side view of the same. Common light guide path 1
For the core 10, a light-transmitting medium that transmits light is used. As the translucent medium, for example, polymethyl methacrylate,
Polycarbonate, plastic materials such as amorphous polyolefin or inorganic glass are suitable,
Free space is acceptable. The optical signal 7 enters from a light incident portion 8 on the right side of the drawing and is extracted from a light emitting portion 9 on the left side. It is required that the optical signal 7 entering the common light guide path 1 does not leak from portions other than the light emitting portion. Therefore, as shown in FIG. It is desirable to provide the cladding 11 having the following.

With this configuration, the light entering the common light guide path 1 from the light incident portion 8 propagates through the core 10 while spreading in the plane direction. The light can be received by providing the light emitting section 9 with a light receiving section. That is, in the transmission paths shown in FIGS. 1 and 2, the same signal can be broadcast transmitted from one signal transmission unit to a plurality of signal reception units.

FIG. 5 is a diagram showing an embodiment of the optical transmission system according to the present invention. The optical transmission system according to the present embodiment includes:
As shown in the figure, a plurality of transmission nodes 14a to 14d, a common light guide 1 connected to these transmission nodes via a first individual light guide 4, and a second individual light guide 4 connected to the common light guide 1.
A plurality of receiving nodes 15a to 15d connected via
And a transmission control unit 12 connected to each transmitting node and receiving node via an electric wiring 13. In the present embodiment, the receiving node and the transmitting node are separately illustrated, but nodes capable of transmitting and receiving may be arranged on both sides of the common light guide path 1. In this case, it is possible to propagate the optical signal in both directions.

FIG. 6 is a diagram showing an example of the transmission control unit 12. As shown in the figure, the transmission control unit 12 receives a transmission request from the transmission node, and issues a communication permission.
It includes a transmission arbitration unit 19 that performs contention arbitration by a specific protocol when receiving a plurality of communication requests, an intensity distribution information holding memory 16, a coupling efficiency information holding memory 17, and an intensity attenuation rate calculating unit 18.

The intensity distribution information holding memory 16 holds the following light intensity distribution information. That is, in the present invention using broadcast transmission, it is difficult in principle to transmit a signal with light intensity equal to all points, and as shown in FIG. 3, the light intensity changes depending on the position where the optical signal is received (light receiving position). Is common. The origin in FIG. 3 is a position in front of the light incident portion of the optical signal into the common light guide path 1, where the light intensity is the highest, and the light intensity decreases as the distance from the portion increases. Since the tendency of the light intensity can be understood when designing the light guide path, the distribution information of the light intensity is stored and held in the intensity distribution information holding memory 16.

The coupling efficiency information holding memory 17 holds the following coupling efficiency information. That is, in the transmission path shown in FIG. 1, a coupling section between the electro-optical converter 3 and the first individual light guide path 4, a coupling section between the first individual light guide path 4 and the common light guide path 1,
A joint between the common light guide 1 and the second individual light guide 4;
Light coupling loss occurs at the coupling portion between the second individual light guide path 4 and the photoelectric conversion unit 6. Assuming that the ratio of the light intensity transmitted by the optical coupling unit is the coupling efficiency, the coupling efficiency of each node can be estimated when designing the optical transmission line. The coupling efficiency is stored and retained in the coupling efficiency information holding memory 17. When the connection configuration of each part of the transmission line is changed, the coupling efficiency changes, so that the memory contents can be rewritten according to the connection configuration in the same manner as in the system initialization procedure.

The intensity decay rate calculator 18 calculates the decay rate from the transmitting node that has issued the transmission request to the receiving node of the transmission destination in accordance with FIG. When an optical signal is transmitted from a transmitting node to a receiving node, the attenuation rate of the received light intensity with respect to the initial light intensity is determined by the optical coupling efficiency of the light emitting unit (including the path until the optical signal is input to the common light guide 1). , And the product of the intensity distribution of the transmission path (common light guide path 1) and the optical coupling efficiency of the light receiving section (including the path up to the input of the optical signal from the common light guide path 1). The intensity decay rate calculator 18 outputs a signal related to the calculated intensity decay rate as a control signal 21 from the input / output controller 20 to the transmission node that has received the transmission request.

The transmitting node is a light emitting unit 2 as shown in FIG.
2 The light emitting section 22 includes a light emitting element 25 such as a semiconductor laser (LD) and a light emitting element driving section 2 for driving the light emitting element.
4, and a light emission intensity control unit 23 to which a signal related to the above-described intensity decay rate is input. The light emitting element driving unit 24 drives the light emitting element 25 according to the input electric signal and the signal from the light emission intensity control unit 23, whereby the light emitting unit 22 outputs an optical signal having a desired intensity. As described above, according to the present invention, by adjusting the output current of the light emitting element driving unit so that a predetermined intensity level is obtained in the light receiving unit based on the signal related to the above-described intensity decay rate, the light emitting element The intensity of the optical signal output from the light source 25 can be adjusted.

As another method, a signal related to the calculated intensity attenuation rate may be output to the receiving node. In this case, the receiving node has a light receiving unit 26 as shown in FIG. The light receiving unit 26 includes a photodiode (P
D) and the like, a signal amplifying section 29 for amplifying a signal from the light receiving element, and a signal amplification rate control section 27 to which a signal related to the above-described intensity attenuation rate is input. The signal amplifying unit 29 amplifies the signal from the light receiving element with an amplification factor according to the signal from the signal amplification factor control unit 27. Thereby, the light receiving section 26 outputs an electric signal of a desired intensity. As described above, according to the present invention, it is possible to amplify the electric signal obtained by the light receiving element 28 to a predetermined level based on the signal related to the above-described intensity decay rate.

Furthermore, it is also possible to use a combination of the above two adjustment methods in the transmitting node and the receiving node.

As described above, according to the present invention, in order to compensate for a change in light intensity, an electro-optical converter for converting an electric signal into an optical signal, a light guide path for transmitting the optical signal, An optical-to-electrical conversion unit for converting to an electric signal, and a transmission control unit for monitoring and controlling the transmission and reception of the optical signal so that the optical signal is correctly transmitted, and wherein the transmission control unit has A memory for storing characteristics is provided, so that transmission quality can be maintained while referring to the optical characteristics of the light guide path during transmission.

Further, the transmission control unit receives a transmission request from an arbitrary communication node, and when giving a communication permission to the transmission node and the reception node, considers a physical positional relationship between the transmission node and the reception node, and The attenuation factor is calculated, whereby the transmitting node is notified of the intensity of the optical signal to be transmitted, or the receiving node is notified of the amplification factor for amplifying the received signal. Further, the light guide path may include a diffusion optical system for expanding a traveling direction of light in a part thereof,
The light guide path and each node may be connected by an optical fiber.

As described above, according to the present invention, the intensity attenuation information included in the optical transmission line is stored in advance, and each node is controlled based on the stored information.
It is possible to maintain a predetermined signal level. This is a mechanism for correcting signal variations between nodes existing from the beginning of transmission, unlike time-dependent changes and changes in the surrounding environment. According to the present invention, it is possible to improve transmission quality in a transmission path using light. .

[0031]

According to the present invention, it is possible to obtain an optical transmission system capable of easily maintaining good transmission quality.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic diagrams each showing an example of a transmission line used in an optical transmission system according to the present invention.

FIG. 2A is a plan view of a common light guide path, and FIG. 2B is a side view thereof.

FIG. 3 is a graph showing a relationship between a light receiving position and light intensity.

FIG. 4 is a diagram for explaining an attenuation rate of received light intensity.

FIG. 5 is a diagram showing an embodiment of the optical transmission system according to the present invention.

FIG. 6 is a diagram illustrating an example of a transmission control unit.

FIG. 7 is a diagram illustrating an example of a light emitting unit.

FIG. 8 is a diagram illustrating an example of a light receiving unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Common light guide path 2 Electric signal 3 Electric light conversion part 4 Individual light guide 5 Diffusion optical system 6 Photoelectric conversion part 7 Optical signal 8 Light incidence part 9 Light emission part 10 Core 11 Cladding 12 Transmission control part 13 Electric wiring 14a-14d Sending nodes 15a to 15d Receiving nodes 16 Intensity distribution information holding memory 17 Coupling efficiency information holding memory 18 Intensity attenuation rate calculation unit 19 Transmission arbitration unit 20 Input / output control unit 21 Control signal

Claims (10)

[Claims] 1. A transmitting node for transmitting an optical signal, a light guide for transmitting an optical signal from the transmitting node, a receiving node for receiving an optical signal from the light guide, and storing optical characteristics of the light guide. A transmission control unit that controls at least one of the transmitting node and the receiving node based on the optical characteristics when transmitting an optical signal. 2. The optical transmission system according to claim 1, wherein said transmission control unit controls the intensity of an optical signal to be transmitted in said transmission node. 3. The optical transmission system according to claim 1, wherein the transmission control unit controls an amplification factor of a signal received at the receiving node. 4. The optical transmission system according to claim 1, wherein said light guide path includes a diffusion optical system for expanding a traveling direction of light. 5. The optical transmission system according to claim 1, wherein at least one of the optical waveguide and the transmitting node and at least one of the optical waveguide and the receiving node are connected by an optical fiber. . 6. A transmitting node for transmitting an optical signal via a light guide, wherein the transmitting node controls the intensity of the optical signal to be transmitted based on optical characteristics of the light guide stored in advance when transmitting the optical signal. The sending node to be characterized. 7. A receiving node for receiving an optical signal via a light guide path, wherein the receiving node controls an amplification factor of the received signal based on optical characteristics of the light guide path stored in advance when the optical signal is received. The receiving node. 8. An optical transmission method for transmitting an optical signal transmitted from a transmission node via a light guide path and receiving the optical signal at a reception node, wherein the transmission node transmits the optical signal based on the optical characteristics of the light guide path. An optical transmission method characterized by controlling the intensity of an optical signal transmitted from a personal computer. 9. The optical transmission method according to claim 8, wherein an amplification factor of the signal received by the receiving node is controlled based on an optical characteristic of the light guide when receiving the optical signal. 10. An optical transmission method for transmitting an optical signal transmitted from a transmitting node via a light guide and receiving the signal at a receiving node, wherein the receiving node is configured to receive the optical signal based on the optical characteristics of the light guide. Controlling an amplification factor of a signal received by the optical transmission method.