DE2333968A1 - Fibre network for data transmission - has optical fibres transmitting by optoelectronic means between any number of subscribers - Google Patents

Abstract

Each subscriber station transmitter and receiver have a certain address code, and the signal content in individual stations are cyclically scanned by a common address generator. A number n of star points is provided, from which individual fibre conductors run to the connected subscribers; these star points are intermediate amplifiers, and the above address generator is connected to one of these points; an intermediate amplifier consists of a transmitter, a receiver and a pulse amplifier; a subscriber station consists of a transmitter, a receiver and a coding unit; a transmitter contains a luminescent diode, and a receiver contains a photodiode.

Description

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Patelhold Patentverwertungs- & Elektro-Holding AG, Glarus (Switzerland)

Fiber network for optoelectronic data transmission

The invention relates to a fiber network for optoelectronic data transmission between any number of sub-'. subscriber stations, in which network between any stations • The possibility of data traffic is given, with each station having a transmitter and a receiver, each transmitter and the associated recipient is assigned a specific address code and the message content of the individual subscriber stations is scanned cyclically by a common address transmitter.

Due to the considerable progress made in recent years in the development of optoelectronic components

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the transmission of information by means of optical fibers is also gaining ground is becoming increasingly important, especially over shorter distances (up to approx. 1 km), such as those used for data transmission Are given in power plants. Optical fibers are already known in various designs. The one Form consists of a glass core with a relatively high refractive index, which glass core is covered by a glass cladding a slightly lower refractive index is enclosed. A beam of light falling through the face, for example, at an angle is therefore continuously and totally reflected at the interface between the core and the cladding in a zigzag shape and can only pass the Paser penetrate lengthways. In another shape, the refractive index changes in the core glass in the radial direction, e.g. according to a quadratic law. This fiber is self-focusing. One outside of the fiber axis The light beam is continuously bent towards the axis and can therefore not leave the fiber laterally. One

Coating of the core is not necessary here.

A distinction is made between single-mode transmission and Multi-mode transmission. In the case of single-mode fibers, the Core diameter only 2 - 4 µm, but the cladding diameter

50-100 µm. The light propagation takes place here according to the same laws as in the dielectric reiter in micro wave technology. The transmission is single-wave and coherent

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Lies required. In the case of the multi-lane fiber, the core diameter is significantly larger, for example 30 - 70 μm, while the cladding thickness is only about 10 μm. As a result of this core diameter, which is very large compared to the light wavelength (0.4-0.7 / μm in the visible range), the light can also be propagated via numerous modes, ie spatial harmonics, in addition to the fundamental wave. Multi-wave and incoherent light can therefore also be used for transmission (light-intensity transmission). The Mehrwelligkeit this Paser has _s, based on a certain Uebertragungsbandbreite, the reach of the fiber limit, however, additional phase distortion. However, it is believed that transmission lengths of up to 1 km can be achieved with a bandwidth of 30 MHz.

The transmission qualities of the various optical fibers are z. Currently, depending on the manufacturer, still very different. Attenuation values of only 4 db / km have already been achieved with single-mode fibers. In addition to a glass core, the multimode fiber also has a liquid core. The lowest attenuation obtained be about 10 db / km (0.6-0.9 / um) ^ eI the version with glass core and about 20 db / km at those with liquid core. With the self-focusing fiber (Selfoc), the attenuation is also 20 db / km. These numerical values originate from tests carried out. The currently commercially available multimode fibers have significantly higher values, for example 200 db / km.

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For applications with less stringent requirements, plastic fibers are still available (attenuation approx. 1000 db / km). While the single mode fiber is always used as a single fiber must be, the multimode fiber can be used as a single fiber as well as in bundles of e.g. 100 pieces or more.

The HeNe laser and the GaAs laser diode come into consideration as light sources for monomode transmission. The HeNe laser is very expensive, laser diodes only exist in the laboratory. In multimode technology, luminescent diodes (LEDs or LE diodes) can be used. They are relatively cheap and already available in numerous designs. The modulation of the light (possible up to approx. 100 MHz) results directly from the corresponding control of the diode / direct current. Photo elements (miniaturized solar cells) and photo diodes come into consideration as receiving elements. They are a little less sensitive than phototransistors, but have very short response times. To complete an optoelectronic transmission path, optical transition elements LE diode fiber and fiber photo sensor are also required. Optical switches, ie semi-transparent mirrors and beam splitting cubes (bridge switches) are also available for special cases. Non-reciprocal switches already exist, but they are impractical and very expensiveν

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Intermediate amplifiers (repeaters) can be built up rait der Combination of photodiode (receiver), pulse amplifier and LE diode (transmitter). Light amplifier without transition to the Modulation bands are variously under development. the The maximum permissible attenuation of the light between two transmission stations is around 50 - 60 db including transfer losses on the fiber. With the attenuation of the currently available multimode fibers can be used without an intermediate amplifier Bridging distances of no more than 250 - 300 m with a recently developed multimode fiber (attenuation approx. 10 db / km) However, distances over 1 km.

According to the current state of the art, the optoelectronic Components for monomode transmission are still in the development stage, in multimode technology already available for purchase. ' Only the transitions between LE-Diode-Paser and fiber-photosensor are still waiting to be realized. In the single mode technology are In addition, the requirements for mechanical accuracy are at least an order of magnitude higher than for multimode transmission.

In building fiber networks propagation of light with respect to observe the same laws as the Uebertragungssystemen in microwave technology. So Each fiber branch is always

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with a considerable loss of performance. Alone through Reflection and power sharing are obtained e.g. for a node with three branches (one incoming, two outgoing) one Attenuation of 3> 5 db and Xein at the knot with four branches incoming, three outgoing) one of 6 db. In addition, there are the absorption losses of the beam splitting elements. These ratios can only be neglected when using bridge switches, with circulators because of them does not improve the high transmission loss at all. In the case of long transmission distances, intermediate amplifiers may have to be used (Repeater) can be installed. If the amplification takes place in the modulation band, there is also a regeneration of the pulses possible.

When transmitting data in power plants, information (e.g. measured and control values, control and switching commands) be transmitted or exchanged between different stations. Every sender and associated receiver is assigned a specific address code. The stations are queried cyclically, e.g. within 20 ms when 50 participants arrive, controlled by a common address transmitter. During each scan cycle, the address code is first transmitted and then the corresponding connection is established. There is thus between the individual information rates

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a temporal correlation that can possibly be exploited when building a fiber network.

Today's transmission networks contain metallic conductors and are therefore susceptible to interference with regard to electrical or magnetic stray fields and translational variables. Such effects are not possible in the case of a pas network with light modulation.

The invention is based on the object of providing a fiber network with a transmission rate for optoelectronic data transmission up to a maximum of about 10 Mbit / s and a maximum transmission distance of about 1 km, which corresponds to the use in an extensive power station. The system should as few / or. have short connections between the individual subscriber stations and, if possible, none Contain nodes and also no optical polygons. If a subscriber station fails, only the one linked to it should Communication links are affected, while the traffic between all other stations continues to function unhindered got to. Any amplifiers should with regard to the temporal interleaving of the information rates of the individual Transmission channels are used as far as possible so that each of the signals from a large number of F4serlinien in their entirety reinforced.

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According to the invention, these requirements are met by that with a fiber network of the type mentioned at the beginning - i.e. with a network in which between any Subscriber stations the possibility of data traffic is given, with each station having a transmitter and a receiver possesses, each sender and the associated recipient is assigned a specific address code and the message content of the individual subscriber stations is scanned cyclically by a common address transmitter -, η star points available are, where η:> 1, from which star points the individual Exit fiber lines to the connected subscriber stations, these star points designed as an intermediate amplifier and the common address transmitter is connected to one of these star points.

By the measures proposed according to the invention and in particular the use of the star point system is in particular a minimum of connections between the individual subscriber stations is ensured and the possibility is given to keep these connections short. Fiber branches and optical switches can largely be avoided, and the Disturbance of individual stations does not affect the undisturbed traffic between the other stations.

The invention is explained by way of example with the aid of FIGS. 1-3. Show it

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Pig. 1 a wire network with only one star point and a number Subscriber stations,

Fig. 2 shows the structure of the neutral point intermediate amplifier shown in Fig. 1,

3 shows a fiber network with two star points and the associated subscriber station groups.

In Fig. 1, 1 means the intermediate amplifier located in the neutral point of the network (its structure still to be explained), which has a receiver E, a transmitter S and a pulse amplifier (not shown here)] 2 means one of the numerous subscriber stations (six are shown symbolically), each consisting of the receiver E, the ' Sender S and the coding part CT, and finally 3 is the ■ common address generator AG.

The transmitter S of the intermediate amplifier 1 is connected to the receivers E of the stations 2 via fiber lines 4 and similarly the transmitters S of the stations 2 via fiber lines to the receiver E of the repeater 1. The address transmitter 3 can either be connected directly to the modulation part of the intermediate amplifier 1 via a metallic line 6 be connected or, as shown in Fig. 1, partially or all over fiber lines. In the latter case, the

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Signals in a converter 7 with the transmitter S into light pulses implemented and fed to the receiver of the intermediate amplifier 1 via the fiber 8.

The receivers E of the stations 2 are designed both as address receivers and as message receivers. At the handover of an address code, all fiber lines leading to the address receivers E. are always sent via the repeater 1 applied. As soon as the corresponding transmitter S comes into operation, the associated address receiver E is switched off, so that there are no feedback phenomena via the intermediate amplifier 1 may occur. The message sent by the transmitter S of a station arrives via the intermediate amplifier 1 also to all message receivers E, but is only recorded before the one programmed to the same address. If at ■ If individual stations are only to be received, the transmitter S can of course be omitted. The numbers at the repeater 1 incoming and outgoing fiber lines so be quite different.

Since all messages flow via the pulse part or transmitter S of the intermediate amplifier 1, the message from the address transmitter 3 The connection leading to this amplifier can also be used to control the entire flow of information. if the Address switching takes place via the fiber line 8, a second fiber line 9 is required for feedback, which

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on the one hand with the transmitter S of the amplifier 1 and on the other hand is connected to the receiver E of the converter 7.

The structure of the intermediate amplifier 1 is shown in more detail in FIG
outlined. As already mentioned, it consists of the receiver E, the pulse amplifier PV and the transmitter S. The paser lines 10 (symbolically five shown) leading to the receiver are surrounded at their ends by a socket 11 and at the end they are optically connected to the active surface 12 of the photodiode FD of receiver E adjusted. The fibers 13 (also symbolically five shown) outgoing from the transmitter S are analogously connected to the
Ends mechanically set and visually attached to the front side
Active area Ik of the LE diode adapted. Due to the directional characteristic of the fiber ends, all fiber lines are mutually decoupled on the receiving side (and also / on the transmitter side).
Couplings exist only in the transmission direction of the amplifier, ie always between one fiber line on the input side and all fiber lines on the output side. The signal amplification is therefore always the same for all channels.

The lengths of the repeater 1 to the subscriber stations leading fiber lines can of course be arbitrarily different. The repeater 1 is if possible to be arranged in the center of a grouping of stations so that the lines are as short as possible. Address giver

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and information flow control, with the repeater 1 via the metallic line 6 or via the fiber lines 8 and 9 connected, on the other hand, can be accommodated in one (or different) possibly far away place (s) be.

If there are several priorities with regard to the locations of the various subscriber stations, these stations can also be combined in separate networks with their own repeaters in the star points. The individual amplifiers are then connected to each other and thus also to the address transmitter via fiber lines. In this way, under certain circumstances, a large number of parallel cable runs can be saved, others can be shortened, or it can be _; bridge the high fiber attenuation in branches with excessively long lengths. A related application example is shown in FIG. As indicated, further such networks can be connected to the amplifier 17. The procedure described allows any combination of star-shaped networks in terms of parallel and / or series connection. As can be seen immediately, the transmission processes are the same as in the case of the individual star-shaped network.

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Here too, in the outgoing and return line (15, l6) between two intermediate amplifiers located in discrete star points 1 and 17, measures against self-excitation can be provided, the This means that feedback barriers, not shown in FIG. 3, must be installed. These locks can be controlled by address codes e.g. optically using Pockels cells. Another possibility is that the transmitter of each neutral point repeater contains at least two light-emitting diodes, one diode all having this star point connected subscriber stations including connection to the next neutral point repeater, while the second diode is connected to the return line to the preceding neutral point repeater. In this case it can the address code controlled non-return lock immediately in which the second diode feeding modulation part be housed. The blocking would then take place in the modulation part and not in the optical area, which would be a great advantage. “In the case of intermediate amplifier 1, this second diode could be connected to the fiber return line be connected to the address giver.

The structure of the proposed network is simple and clear; optoelectronic there are only the problems of a simple fiber connection. In particular, as already noted, there are no fiber branches and optical switches. If a subscriber station fails

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of which, as has also already been said, only the relevant one Communication link affected, while traffic between all other stations is unhindered. The operational safety of the few intermediate amplifiers located at critical points can be increased, for example, through redundancy circuits increase additionally. Any failures can also be monitored by reporting back on the flow of information easily identify and locate. Instead of individual fibers, fiber bundles (e.g. 100 fibers, bundle diameter about 0.5 mm). Sporadic fiber breaks then have a practical effect on the transmission quality no influence yet. The fiber network can be expanded as required up to a large number of participant stations (e.g. 50 - 100).

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Claims (1)

- 15 - P 533 Claims ■%. ' Fiber network for optoelectronic data transmission between Any number of subscriber stations, in which network the possibility of data traffic between any stations is given, with each station having a transmitter and a receiver, each transmitter and the associated receiver a specific address code is assigned and the message content of the individual subscriber stations through a common Address transmitter is scanned cyclically, characterized in that η star points are present, where n ^ gs-l, from which star points the individual fiber lines to the connected subscriber stations (2) depart that these Star points are designed as an intermediate amplifier (1) and that the common address transmitter (3) at one of these star points connected. 2. fiber network according to claim 1, characterized in that an intermediate amplifier (1) consists of a receiver (E), a transmitter (S) and a pulse amplifier (PV). 3. fiber network according to claim 2, characterized in that a subscriber station (2) from a receiver (E), one Transmitter (S) and a coding part (CT) consists. 409882/0688 - 16 - P. 4. fiber network according to claim 3, characterized in that a transmitter (S) has a luminescent diode (LE) and a receiver (E) has a photodiode (FD). 5. Fiber network according to claim 3, characterized in that the transmitter (S) of an intermediate amplifier (1) is connected via fiber lines ( ¹ O with the receivers (E) of the associated subscriber stations (2), while the transmitters (S) of the subscriber stations (2) are connected to the receiver (E) of the intermediate amplifier (1) via other fiber lines (5). 6. fiber network according to one of claims 1 to 5, characterized in that the address transmitter (3) has a metallic line (6) is connected directly to the modulation part of each intermediate amplifier (1). 7. fiber network according to one of claims 1 to 5, characterized in that the address transmitter (3) at least partially is connected directly to the receiving part of the intermediate amplifier (1) via a fiber line (8). 8. fiber network according to claim 7, characterized in that the signals of the address transmitter (3) in a converter (7) with 409882/0688 - 17 - ρ a transmitter (S) converted into light pulses and via a Paser line (8) are fed to the receiver (E) of the intermediate amplifier (1). 9. Pasernetz according to one of claims 1 to 8, characterized in that the receivers (E) of the subscriber stations (2) are designed both as address as well as message receivers that when an address code is transmitted via the assigned repeater (1) always ^{all of the paser lines (2} O) leading to the address receivers (E) are acted upon and that as soon as the corresponding transmitter (S) enters the puncture, the associated address receiver (E) is switched off. 10. Pasernetz according to one of claims 1 to 9, characterized in that a message sent by the transmitter (S) of a subscriber station (2) reaches all message receivers (E) via the associated repeater (1), but only from the one to the same Address programmed recipient is recorded. 11. Fiber network according to one of claims 1 to 10, characterized in that the connection from the address transmitter (3) to an intermediate amplifier (1) at the same time to the 409882/0688 - 18 -? 533 Control of the whole, through this repeater information flow is used. 12. Fiber network according to claim 11 and 8, characterized in that that for the information flow control the one between the address transmitter (3) and the intermediate amplifier (1) Converter (7) in addition to the transmitter (S) also has a receiver (E), which is connected to the via a further Paser line (9) Transmitter (S) of the intermediate amplifier (1) is connected, via which Paser line the feedback takes place. 13. Pasernetz according to one of claims 1 to 12, characterized characterized in that the intermediate amplifiers (1) assigned to the individual subscriber station groups (2) are connected to each other and thus also to the address transmitter (3) via fiber conductors (15, 16), the transmitter (S) an intermediate amplifier (1) with the receiver (E) of another and its transmitter (S) with the receiver (E) of the the former is connected. I ¹ I. Fiber network according to claim 13, characterized in that in the outgoing and return line (15, 16) between two intermediate amplifiers located in discrete star points (1, 17 Fig. 3) to avoid self-excitation, feedback 409882/0688 - 19 - P 533 locks are built in. 15. Fiber network according to claim 14, characterized in that the feedback barriers are address code controlled. 16. Fiber network according to claim 15, characterized in that the control takes place optically with the help of Pockels cells. 17. Fiber network according to claim 15, characterized in that the transmitter (S) of each neutral point repeater
contains at least two light-emitting diodes, one diode feeding all subscriber stations connected to this neutral point, including the connection to the next neutral point repeater, while the second diode is connected to the return line to the preceding neutral point repeater, and that the address code-controlled feedback lock directly in the second diode-feeding modulation part is housed. PATELHOLD Patent exploitation and
Elektro-Holding AG 409882/0688