Method of transmission of an optical signal through free space

The invention relates to a method for transmitting a signal to the Transmission of information from a source to a spatially thereof remote signal sink, wherein the signal of at least a part Path between the signal source and the signal sink as an optical signal at least one free optical path between an optical Transmitter and an optical receiver is transmitted. Next concerns Invention also computer programs and devices to support and Performing such a method, particularly suitable Signal transmission equipment, server units, processor modules and programmable gate array assemblies.

Such a method is known from EP 0962795 A2.

In some cases, the signal transmission may be advantageous optical to transmit signals through the free space instead of optical carrier media such as using optical fibers. The optical Signal transmission through free space brings especially cost advantages if the to be overcome distances are short and if the is vision range substantially undisturbed. In the above-mentioned EP 0 962 795 A1, for example, was the transmission of optical signals for a Communication for exchanging data between two separate areas separate devices used.

An optical communication link via the free space is However, a clear line of sight without obstacles ahead, so nothing with can interfere optical signal on the track. If obstacles may arise, for example, if a bird or a raindrop the Light beam crosses, mechanisms are needed, the error-free Transmission sure.

The object of the present invention is in contrast, a method of initially described type with the simplest possible means to the effect further develop that a reliable transmission of optical signals is ensured by the free space.

According to the invention, this object is as surprisingly simple as effective manner achieved in that the signal in two or more is duplicated or split identical signals that each of these mutually identical signals each as an optical signal over a own optical path, the at least one free optical path comprises, from an optical transmitter to an optical receiver is transmitted, and that the received signals via a signal combiner summarized and the only signal of the signal sink are supplied.

In this way, for example in a situation when one or even several of the free optical paths briefly by an obstacle are blocked, for example due to atmospheric agents such as rain, snow or debris, or for example by a Bird, the other on the remaining free optical paths Signal is still transmitted.

Advantageously, a variant of the method, which is characterized in that the signal from the signal source electromagnetic signal is that a signal splitter in several with the original signal in its information content identical signals is split, subsequently in a corresponding number of optical transmitters in each case converted into an optical signal and / or are amplified, and that the thus produced, mutually identical optical signals each having an associated optical path in time are transmitted in parallel in space and / or.

In a much simplified, alternative method variant is only one optical transmitter provided the passive beam splitter is connected downstream, in which from an optical signal of the optical transmitter a Plurality of mutually identical optical signals is generated. Thereby can be saved n-1 optical transmitter.

In a further process variant, it is provided that the intercrossed identical optical signals of each optical path respectively in an optical Receiver are converted into electric signals. The electrical Signals then enter the appropriate information and can in appropriate continue to be processed and forwarded devices to the signal sink.

A development of this method variant provides that the electrical Signals from the various optical receivers a signal combiner are supplied to the one from the various electrical signals Signal which is supplied to the signal sink.

Advantageously, the signal combiner to be executed as an evaluator, in which one of the various electrical input signals Output signal is generated which of the output signal from Signal source that best fits.

Especially advantageous is a further development in which the evaluator today detected corresponding information units of the various input signals be and it had a majority circuit each one formed Information Unit and impressed on the output signal. On This allows transmission errors on each channel optimally be suppressed.

It is also particularly advantageous if the above-described Process variations in the optical receivers coordinated Compensation of the maturities of the individual optical signals from the is made different optical paths.

Similarly, it may prove to be particularly favorable when the optical in Receivers coordinated power adjustment of each optical Signals from the various optical paths is performed.

In an alternative process variant, it is provided that the optical Signals from the various optical paths a passive Beam combiner are fed, of them into a single optical Signal summarizes which a downstream optical receiver is supplied.

In this way, n-1 optical receiver can in use of n free optical paths can be saved.

Very particular preference is a variant of the invention The method in which the optical signals are transmitted pulsed, wherein the the optical signals imparted information units on Pulse be ready. This is a very significant degree of freedom Handling of the signal transmission and an eventual processing of Signals opened.

Particularly preferred is a development of this embodiment, at the at least one optical path, the image information units inverted to rückinvertiert pulses and, after passing through an optical link becomes. In the event that all the optical paths on no pulse arrives, can in this way between a transmission of a series of 0-information units and it completely different case of Interruption of all transmitted signals are discriminated against.

Also advantageous is a development, which provides that in the presence a pulse from at least one optical signal of the various optical Paths a corresponding pulse in the output signal of the passive Strahlenüberlagerers produced and the downstream optical receiver is interpreted as corresponding information unit. Thus, even in a minimum to get through the optical signals on different paths still the signal transmission can be maintained in the correct form.

To adapt to different operating conditions is a Process variant is advantageous in which the optical signal to at least an optical path through at least one optical relay between two is enhanced and / or redirected optical paths. As a result, bridged larger distances and for example, massive obstacles be bypassed.

To comparable optical signals from the various optical paths in to obtain signal combiner, it is recommended that the optical paths so to designed that they each represent the same optical path length.

It is of particular advantage if the various optical paths are designed identical to each other.

Alternatively, however, a time alignment of the optical signals of various optical paths are made.

A particularly preferred variant of the method finally provides that the signal to be transmitted before its transmission is split into signal packets that each signal packet for a attached to burst characteristic signal sequence and together with of each signal packet with a higher bit rate than the original Signal is transmitted, and that the characteristic signal sequences for Detecting and optionally for correcting errors in the transmitted used signals and / or for synchronization of the transmission path will.

Thereby, on a splitting of the invention of Original signal and transmission on parallel optical paths completely independent path again to make sure that transmission errors, as described for example in case of interruption of the free optical distances can occur if an obstruction comes into the line of sight, be absolutely reliably avoided.

In the context of the present invention also falls a Signal transmission means for carrying out the invention Method with a signal source for generating to transfer a Signal, a signal splitter for duplicating or splitting this Signal into two or more identical signals, one of the number of these mutually identical signals corresponding set of optical Paths, each of which comprises at least one free optical path, one or more optical receivers for receiving the transmitted optical signals, and a signal combiner, in which the transmitted signals and performing an as single signal Signal sink can be supplied.

An embodiment of the signal transmission device according to the invention distinguished by the fact that a single optical path, an optical transmitter is provided which is coming from the beam splitter optical signals in Converts signals.

Considerably easier is an alternative embodiment in which an optical Transmitter for generating an optical signal from the output signal of the Signal source is provided, the signal splitter as a passive beam splitter downstream. In this way, when n optical used save paths n-1 optical transmitter.

Preferably, the one or more optical channels comprise at least one Laser, whereby the advantageous properties, such as the Generating coherent light, high beam bundling options, extremely low beam divergence and high power for the inventive can exploit signal transmission.

In a further embodiment of the invention Signal transmission means is a respective optical receiver per optical path for each of the mutually identical optical signals provided that the received optical signals into electrical signals, converts.

This embodiment can advantageously be improved by the Signal combiner is configured as an evaluator.

An alternative embodiment of the invention Signal transmission means provides that the signal combiner as a passive beam combiner is executed, the optical signals from the are supplied to various optical paths, and they only to a optical signal sums which a downstream optical Receiver is supplied. In this way, when n optical paths n-1 optical receiver from the embodiment described above, be saved.

To adaptability to different circumstances of to obtain signal transmission path, in a further advantageous Embodiment of the signal transmission device according to the invention at least one optical path of at least one optical relay between two optical paths provided in which the corresponding is optical signal is amplified and / or diverted.

Furthermore, falls within the scope of the present invention also provides a Server unit, a processor module and a gate-array module for Support the above described method according to the invention and a computer program for implementing the method. The method may both as a hardware circuit, as well as in the form of a computer program will be realized. Today, software for programming is power DSPs preferred as new findings and additional functions easier by changing the software on an existing hardware basis are implementable. but method can also as hardware modules in Facilities for signal transmission, for example in an IP (Internet = implemented Protocol) network or a telecommunications system will.

Further advantages of the invention will be apparent from the description and the Drawing. Also, the above-mentioned and further below Features according to the invention either individually or collectively be used in any combination. The illustrated and described Embodiments are not to be construed as an exhaustive list, but rather have exemplary character for describing the invention.

The invention is illustrated in the drawing and by means of embodiments explained in more detail. Show it:<dl tsize="5"><dt>Fig.1</dt><dd>a basic diagram of a first embodiment of the present invention Signal transmission means each having an optical transmitter and an optical receiver per free optical path length;</dd><dt>Fig.2</dt><dd>a second embodiment with only one optical transmitter for all optical paths, but a plurality of optical receivers;</dd><dt>Fig.3</dt><dd>a third embodiment with only one optical transmitter and only an optical receiver for optical paths; and</dd><dt>Fig.4</dt><dd>a schematic for a possible division of the signal to be transmitted in various signal packages in accordance with a variant of the Inventive method.</dd></dl>

According to the present invention, a signal to be transmitted in two duplicated or more identical signals, or split, each of these mutually identical signals each as an optical signal over a own optical path, the at least one free optical path comprises, from an optical transmitter to an optical receiver transmitted and the received signals via a signal combiner combined and fed as a single signal to a signal sink.

In Fig. 1 is a signal transmission means for carrying out the above Described method of the invention shown, in which a Splitting of the signal to be transmitted into a plurality of identical signals with the same information content as the original signal and transmission the same is provided via an independent free optical path.

Here, the signal to be transmitted is generated in a signal source. 1 At This entity may be, for example, even to an electrical signal, but already be an optical signal. In a downstream Signal splitter 2 is now the signal to be transmitted in a plurality of identical Signals, reproduced in this case, into three signals, each a optical transmitter 3, in particular a laser are supplied. From here the optical signals to each one a free optical Distance, which also features optical relay 4 as amplifiers or Baffles may be located, to a respective associated optical Receiver 5 sent. The received signals from the various optical Receiver 5 a signal combiner 6 are fed, where they at a single signal summarized and transmitted to a signal sink 7 are representing the goal of the entire signal transmission.

In FIG. 2 is an opposite of the signal transmission device according to Fig.1 considerably simplified embodiment shown, where the from the Source 1 outgoing original signal initially in a single optical Transmitter 3 ', preferably a laser, is converted into an optical signal becomes. This is then a passive beam splitter 2 'supplied to the as Signal splitter and acts from several (in this case 3) identical generates optical signals. These in turn are each on their own optical path with free optical path to a corresponding number optical receivers sent 5 where the optical signals received and in electrical signals are converted, the one designed as Evaluator Signal combiner 6 'are fed.

In evaluator 6 'in turn from the various signals supplied single signal which is transmitted to the signal sink 7th Preferably, the evaluator of each respective Information Units of the various input signals detected by a Majority circuits each formed a single unit of information and the Output toward the signal sink 7 impressed.

For error detection and correction can in the present case n = 3 optical paths of four power levels of the optical signals transmitted are defined as they arrive at the receivers. 5 These four Power levels are allocated to the digital numbers 0, 1, 2 and 3. FIG. A Majority circuit can now easily be realized that for In the event that the power level 0 or 1 in the respective received optical Signal is detected, the corresponding information unit is a logical 0, in the case that a power level 2 or 3 is detected, the Information unit, a logic 1 is assigned. This can be a very simples "2 of 3" realize -Entscheidungsschema. In addition, however also Other possibilities for the design of the evaluator, for example, complicated arbitration schemes imaginable.

A further, very particularly simple embodiment of the Signal transmission device according to the invention is shown in Fig. 3. The Transmitting part is here identical to that in FIG. 2 design, but could also be as shown in Fig. 1 be executed. In the receiving part is a signal combiner 6 "in contrast to the previously described embodiments, a single passive Beam combiner provided which collects all the optical signals from the various optical paths receiving and a single optical signal brings together, which a single optical receiver 5 'supplied is, in turn, generates a usually electrical signal therefrom, which the signal sink 7 is supplied to the end. In this way at n different optical paths n-1 optical receiver saved.

Especially advantageous is a variant of the method, at the splitting of the signal to be transmitted before its transmission in various signal packages are as schematically in the central part of Fig. 4 are shown. Then, each signal packet for a respective signal package attached to signal sequence characteristic of OH and together with the respective packet signal having a higher bit rate than the original signal is transmitted as in the lower part of FIG. 4 are indicated. If the bit rate of the original signal X bit / sec, then the be split signal along with their characteristic signal frequencies transmitted at a rate of (X + N) bit / s.

The characteristic signal sequences OH then to Detecting and optionally for correcting errors in the transmitted Signal and / or for synchronization of the transmission path used.