WO2005116710A1

WO2005116710A1 - Apparatus for the transmission of data via a plastic optical waveguide

Info

Publication number: WO2005116710A1
Application number: PCT/EP2005/003855
Authority: WO
Inventors: Rainer Schenkyr
Original assignee: Hirschmann Automation And Control Gmbh
Priority date: 2004-05-19
Filing date: 2005-04-13
Publication date: 2005-12-08
Also published as: EP1749228A1; DE102004025280A1

Abstract

Disclosed is an apparatus (1) for transmitting data via an optical waveguide (4), at one end of which binary data is fed via a transmitter unit (3) while the fed and transmitted data is extracted at the other end via a receiver unit (5). The aim of the invention is to convert the binary electrical data in order to increase the data rate. Said aim is achieved by mounting an encoding unit (2) upstream of the transmitter unit (3) and mounting a decoding unit (6) downstream of the receiver unit (5), the optical waveguide (4) being made of plastic.

Description

DESCRIPTION

DEVICE FOR TRANSMITTING DATA THROUGH A PLASTIC LIGHTWAVE GUIDE The invention relates to a device for transmitting data via an optical waveguide according to the features of patent claim 1.

Devices for data transmission of binary data via optical fibers are known. Data transmission via fiber optic cables has the advantage that no interference due to electromagnetic influences can occur during data transmission.

When using such devices for data transmission, it is necessary to connect the devices of systems, plants or the like which are to be networked with one another for the purpose of data exchange to the optical fibers. In principle, a transmission unit at one end of the optical waveguide is required for data transmission via optical waveguides, the data to be fed into the optical waveguide being converted from binary electrical data into optical signals via this transmitting unit. The data fed in and transmitted at one end are then coupled out at the other end of the optical waveguide via a receiving unit and converted from optical to binary electrical signals there, so that they are available for further processing in the device connected there. 0 When installing and networking such systems and systems, it is therefore necessary to connect the ends of the optical fibers via suitable plug connections to the transmitter or receiver units or interfaces of the devices and the like. When using fiber-optic cables made of glass, the disadvantage here is that a very complex and therefore error-prone assembly of the plug connections on the fiber-optic cable is given because such glass optical fibers have a very thin light-guiding diameter of less than 100 micrometers in diameter. In areas in which there are no critical environmental conditions, such as high temperature fluctuations, vibrations, moisture and the like, such optical waveguides made of glass are suitable, since they can be used to achieve a high transmission rate of over 100 megabits per second. If glass fiber-optic cables are used in harsh environmental conditions (e.g. in production halls, on machines, in unfavorable weather conditions and the like), such a glass fiber-optic cable can no longer be used with reasonable effort, especially with regard to the time and costs for the installation be used. To avoid these critical assembly and installation techniques, it is advisable to use plastic ones instead of glass optical fibers. For this reason, plastic optical waveguides with a light-guiding diameter of 1 mm, for example, are preferably used in the industrial environment, which can therefore be provided (assembled) quickly and reliably with a simple tool in an industrial environment. However, such an optical fiber made of plastic has the disadvantage of a smaller transmission bandwidth compared to an optical fiber made of glass, which is significantly less than 5 megahertz at a length of 1 km. With such a transmission bandwidth, a transmission rate of at most 10 megabits per second can at best be achieved, which, however, is far too low for data transmission in the industrial environment with today's requirements.

The invention is therefore based on the object of providing a device for data transmission via an optical waveguide in which, on the one hand, a plug connection can be attached to the ends of the optical waveguide quickly, easily, inexpensively and reliably, but at the same time also the required transmission rate of up to 100 Megabits per second (and possibly more) can be achieved.

This object is achieved by the features of patent claim 1. On the one hand, it is proposed according to the invention that the optical waveguide is a plastic optical waveguide. The advantages of the easy and, above all, process-reliable mounting of connectors at the ends of the optical fibers are retained, with another advantage to be mentioned that the laying of such optical fibers made of plastic provides the required robustness in the industrial environment and also beyond are inexpensive. This is particularly noticeable when networking devices that are further away. At the same time, however, the transmission rate or bandwidth decreases with the distance of the devices to be networked, so that, on the other hand, the invention provides that a coding unit is connected upstream of the transmitting unit for converting the binary data in order to increase the data rate, and a decoding unit is connected downstream of the receiving unit. The coding unit converts the signals pending for data transmission in such a way that the conversion results in an increase in the data rate. By means of this conversion, the invention enables the binary data to be transmitted with a substantially higher transmission speed and a significantly increased bandwidth via an optical fiber made of plastic. This significantly increases the transmission rate while maintaining the advantages of the plastic optical fiber, so that it can be used in an industrial environment under today's requirements. If the data has been transmitted via the optical fiber made of plastic, it is necessary at the end of the optical fiber that the data be decoupled and converted back there, for which purpose a decoding unit is connected at the end of the optical fiber, which is designed for this conversion (decoding) of the transmitted data is.

In a further development of the invention, it is provided that the coding unit is designed to convert the binary digital data signal into a multi-stage coded signal, which has a power density spectrum shifted to a lower frequency range than the binary code, and the decoding unit for converting the multi-stage signal into a binary-coded output signal is trained. This implementation represents one of are several ways to implement the binary data in order to increase the data rate with limited bandwidth of the transmission line.

In a further development of the invention, the coding unit is designed for conversion according to an MLT-3 coding, and the decoding unit is designed for converting back the MLT-3-coded data. Such coding has the advantage that corresponding electronic modules (coding circuits) with this function are commercially available. The MLT-3 code is a special 3-level code with the output status of the coding unit 0, +1,

0, -1, 0, A logical 1 at the input of the coding unit means a change in the output state in the sequence described. A logical 0 does not change the initial state.

The output states of the coding unit must be adapted accordingly in the optical transmitter unit, e.g. State -1 in "no light" (LED off), state 0 in "half light output" and state +1 in "full light output".

In addition to the two methods mentioned for converting the binary data for the purpose of increasing the data rate, other methods that serve the same purpose are also conceivable. Overall, such methods have the advantage that a transmission of digital data with bit rates greater than 50 megabits per second (or the resulting bandwidth) is made possible in the first place via a plastic optical waveguide with a corresponding length.

In a further development of the invention, light-emitting diodes are used for signal transmission, which emit light in the visible green area (preferably approximately 585 nm ± 10%). This has the advantage that a very rapid conversion of the electrical signals into optical signals can be achieved by means of light-emitting diodes and the attenuation of the signals when using plastic optical fibers is very low in this length wave range.

In a further development of the invention, light-emitting diodes are used for transmission, which emit in the infrared range (preferably approximately 850 nm ± 10%), the Plastic optical fibers are designed as HCS optical fibers. In this combination, too, the damping is extremely low, so that the combination mentioned is particularly advantageous.

In a development of the invention, the transmitter unit and / or the receiver unit have a direct, micro-reflector-assisted light coupling. This increases the coupling efficiency between the means for converting the electrical signals into optical signals (or vice versa), which are, for example, light-emitting diodes, and the optical waveguide, it being possible to achieve increases of at least 5 dB, preferably 7 dB, and therefore transmission distances of a few hundred meters, preferably more than 500 meters.

Further refinements of the invention, to which, however, this is not restricted, are described below and explained using exemplary embodiments.

Show it:

FIG. 1 shows an inventive device for data transmission,

FIG. 2 shows an automation system according to the prior art for using the device according to the invention,

FIG. 3 shows a further embodiment of the device according to the invention according to FIG. 1,

FIG. 4 shows the design of a direct, microreflector-assisted light coupling,

Figure 5 shows one end of the optical fiber with a connector.

FIG. 1 shows the configuration of a device 1 according to the invention for data transmission. A coding unit 2 is provided on the input side has an input E, via which the coding unit 2 is supplied with binary electrical input signals. On the output side, the coding unit 2 is followed by a transmission unit 3 with which the binary electrical input signals are converted into optical signals after their conversion. This transmission unit 3 is preferably light-emitting diodes. The conversion of the electrical binary input signals in the coding unit 2 takes place according to methods as have already been described, for example, for patent claims 2 and 3. After the conversion of the signals in the coding unit 2 for the purpose of increasing the data rate and a subsequent conversion into optical signals in the transmission unit 3, these optical signals are fed into an optical waveguide 4. The optical waveguide 4 is a plastic optical waveguide, for example a polymer or an HCS fiber. This list is only an example, so that other types of fibers can also be used.

At the output end of the optical waveguide 4 there is a receiving unit 5 which converts the optical signals transmitted via the optical waveguide 4 into electrical signals. These converted signals are fed to a decoding unit 6, which is designed, for example, to convert the multistage signal back into the binary-coded output signal. The binary input signals transmitted quickly and over a large distance are thus available for further processing as binary output signals at the output A of the decoding unit 6. -

FIG. 2 shows an automation system 7 for using the device 1 for data transmission. The automation system 7 shown by way of example consists of a control level 8, a process level 9 and a field level 10 in a manner known per se. In the control level 8 there is a control computer 11 which monitors a process (for example a production or a process-related sequence). One or more process computers 12 are present within process level 9. These can be, for example, programmable logic controllers (PLCs). Input units are on the process computers 12 (For example sensors 13) and output units (for example actuators 14, actuators or the like) are connected. The underlying process can be controlled or regulated with the signals of the input or output units. In this exemplary embodiment, the master computer 11 is connected to the process computers 12 via a data bus 15, wherein the master computers 12 can also be connected to their connected devices via corresponding bus systems. The control computer 11 has an interface 16, just as the process computers 12 each have an interface 17, the connection to the data bus 15 being established at these interfaces 16, 17. According to the present invention, this data bus 15 is an optical waveguide made of plastic, which is particularly advantageous due to the harsh environmental conditions that prevail during the operation of the automation system 7.

According to FIG. 3 it is shown that the device according to the invention, as shown in FIG. 1, is connected on one side to the master computer 11 and on the other side to one of the process computers 12. For this purpose, in the embodiment according to FIG. 3, on the one hand, the coding unit 2 with its associated transmission unit 3 are connected to the control computer 11, while the reception unit 5 with its associated decoding unit 6 is connected to the control computer 12. It is conceivable here that the units 2/3 or 5/6 form an independent module, which is connected on the one hand to the optical waveguide 4 and on the other hand to the interface 16, 17 of the control computer 11 or the process computer 12. Alternatively, it is conceivable to integrate the units 2/3 or 5/6 into the interfaces 16 or 17 of the computers 11, 12. In addition, it is conceivable that not only the unit 2/3 or 5/6 is arranged at one end of the optical waveguide 4 (as shown in FIG. 3), but that a transmitting unit 3 and a receiving unit 5 is assigned with the coding unit 2 assigned to it or the decoding unit 6. A bidirectional data transmission is thus implemented in a particularly advantageous manner for fast data exchange. FIG. 4 shows that the transmitter unit 3 (the same applies analogously to the receiver unit 5) has a direct, micro-reflector-assisted light coupling. For this purpose, the transmitter unit 3 (light-emitting diode) is followed by a reflector 18 (microreflector) and aligned in the direction of the end face of the end of the optical waveguide 4, so that the light emitted by the transmitter unit 3 is focused as completely as possible onto the end face of the optical waveguide 4 Avoid wastage. This increases the coupling efficiency between the transmitter unit 3 and the optical waveguide 4 in a particularly advantageous manner.

FIG. 5 shows the end of an optical waveguide 4 which, in a manner known per se, has a light-guiding conductor 19 (here made of plastic), around which a sheathing 20 is arranged. This optical waveguide 4 made of plastic can be provided with a plug 21 in a simple manner, a part of the sheathing 20 being removed beforehand, and depending on the design of the plug connector 21, the sheathing 20 may not be removed. By means of the attached connector 21, this end of the optical waveguide 4 is connected to the transmitting unit 3 or the receiving unit 5. The counterpart (socket) matching the plug connector 21 is part of the transmitter unit 3 (or the receiver unit 5) or a module (consisting of the units 2/3 or 5/6) or part of the interfaces of devices.

LIST OF REFERENCE NUMBERS

1. Device for data transmission

2. Coding unit 3. Transmitting unit

4. Optical fiber

5. Receiver unit

6. Decoding unit

7. Automation system 8. Control level

9. Process level

10th field level

11. host computer

12. Process computer 13. Sensors

14. Actuators

15. Data bus

16. Interface

17. Reflector 18. Light guiding conductor

19. Sheathing

20. Connector

Claims

PATENT CLAIMS

1.

Device (1) for data transmission via an optical waveguide (4), at one end of which binary data are fed in via a transmitting unit (3), the fed-in and transmitted data being coupled out at the other end via a receiving unit (5), characterized in that that for converting the binary electrical data for the purpose of increasing the data rate of the transmitting unit (3), a coding unit (2) is connected upstream and the receiving unit (5) is followed by a decoding unit (6), the optical fiber (4) being an optical fiber made of plastic.

Second

Device (1) according to Claim 1, characterized in that the coding unit (2) is designed to convert a binary digital data signal into a multi-stage coded signal which has a power density spectrum shifted to a lower frequency range than the binary code, and the decoding unit (6) is designed to convert the multistage signal into the binary-coded output signal.

Third

Device (1) according to claim 1 or 2, characterized in that for

Transmission via the optical fiber (4) an MLT-3 coding is used.

4th

Device (1) according to claim 1, 2 or 3, characterized in that the transmitter unit (3) has a light-emitting diode which shines in the visible green area, and the receiver unit (5) is designed to receive the green optical signals.

5th

Device (1) according to claim 1, 2 or 3, characterized in that the transmitter unit (3) has a light-emitting diode which emits in the infrared range, and the receiver unit (5) is designed to receive the infrared signals.

6th

Device (1) according to one of the preceding claims, characterized in that the transmitting unit (3) and / or the receiving unit (5) have a direct, microreflected, supported light coupling.

7th

Device (1) according to one of the preceding claims, characterized in that a transmitting unit (3) with an associated coding unit (2) and a receiving unit (5) with an associated decoding unit (6) for bidirectional data transmission are arranged at one end of the optical waveguide (4) are.

8th.

Device (1) according to one of the preceding claims, designed for use in the. Transmission of Fast Ethernet signals in the range of 100 megabits per second.

9th

Device (1) according to claim 2, characterized in that the multi-stage coded signal is converted by means of a tertiary code.