WO2020097651A1

WO2020097651A1 - Method for transferring data and/or information

Info

Publication number: WO2020097651A1
Application number: PCT/AT2019/060380
Authority: WO
Inventors: Gerhard Humer
Original assignee: Ait Austrian Institute Of Technology Gmbh
Priority date: 2018-11-13
Filing date: 2019-11-11
Publication date: 2020-05-22
Also published as: AT521851A1; EP3881454A1

Abstract

The invention relates to a method for transferring data and/or information, comprising the following steps: - creating a carrier signal (S₁) having a specified local transmission frequency (f_LOT), - creating an electrical useful signal (S₂) containing the data/information to be transmitted, wherein, in individually successive periods of time (T₁,..., T₂₀), individual symbols are encoded in the useful signal (S₂), - symbolically modulating the useful signal (S₂) to the carrier signal (S₁) and creating a modulated optical data signal (S₃) for individual periods of time (T₁,..., T₂₀), wherein, for each of the periods of time (T₁,..., T₂₀), as a result of the modulation, a phase position of the optical data signal is specified, - wherein the phase position of the optical data signal in a period of time (T₁,..., T₂₀) is determined on the basis of the value of the useful signal available in said period of time (T_i) and the phase position in the preceding period of time (T_i-1), particularly by specifying a phase difference from the phase position in the directly preceding period of time (T_i-1), - as applicable, weakening or amplifying the modulated optical data signal (S₃), - transmitting said data signal (S₃; S₄) via an optical channel (5), particularly via fiberglass cable or open space, - receiving the transmitted optical data signal (S₅) by a receiver, - creating an additional carrier signal (S₆) having a specified local receiver frequency (f_LOR), the difference of which from the local transmitting frequency (f_LOT) is determined by an intermediate frequency (f_ZF) specified in advance, particularly by means of a receiver-side laser (306), - multiplicative mixing of the transmitted optical data signal (S₅) and of the additional carrier signal (S₆) and thus creating an electrical signal (S'₇₎, - band pass filtering the electrical signal (S'₇) by means of a band pass filter and thus creating a band pass filtered signal (S'₈) having a frequency band comprising the specified intermediate frequency (f_ZF), - delaying the band pass filtered signal (S'₈) by the duration of a period of time (T₁,..., T₂₀) and superimposing or multiplying the band pass filtered signal (S'₈) together with the thus created and, as applicable, modified, delayed signal (S'₉) and thus obtaining a receiving signal (S'₁₀) corresponding to the useful signal (S₂).

Description

Process for the transmission of data and / or information

The invention relates to a method for transmitting data and / or information between a transmitter via an optical channel according to one of claims 1 and 6 and a receiver according to one of claims 10 and 11, and an arrangement according to claim 13.

The influence of the carrier signal can be reduced by choosing a modulation in which the information is coded with reference to the preceding modulation signals, for example in the case of differential coding. In such a case, the phase or frequency difference between transmitter and receiver only have a differential influence. Therefore, the transmission of a residual carrier or a pilot signal can be saved in comparison to procedures known from the prior art. A conversion into an intermediate frequency and a residual carrier or a pilot signal is not necessary. Such a transmission is used primarily in the field of quantum communication.

The term symbol denotes the information content that is encoded by a useful signal within a certain time period.

The main advantage of the present invention is that synchronization between transmitter and receiver does not have to be present. Furthermore, the invention has the advantage that demodulation and signal conditioning can take place at relatively low frequencies, so that existing or cheap circuits can be used and complex signal reconstruction is not necessary.

A preferred embodiment of the invention relates to a method for transmitting data and / or information comprising the following steps:

Creating a carrier signal with a predetermined local transmission frequency,

Creating an electrical useful signal containing the data / information to be transmitted, with individual symbols being encoded in the useful signal in individual successive time segments,

modulating the useful signal onto the carrier signal symbol-wise and creating a modulated optical data signal for individual time segments, with a phase position of the optical data signal being predetermined by the modulation for each of the time segments, the phase position of the optical data signal in a time section is determined on the basis of the value of the useful signal available in this time section and the phase position in the respective previous time section, in particular by specifying a phase difference with the phase length in the immediately preceding time section,

- If necessary, weakening or amplifying the modulated optical data signal

Transmission of this data signal via an optical channel, in particular via fiber optic cable or free space,

Receiving the transmitted optical data signal with a receiver,

Creating a further carrier signal with a predetermined local receiver frequency, the difference to the local transmission frequency being determined by a predetermined intermediate frequency, in particular by means of a receiver-side laser,

multiplicative mixing of the transmitted optical data signal and the further carrier signal and thus creating an electrical signal,

Bandpass filtering of the electrical signal with a bandpass filter and thus creating a bandpass-filtered signal with a frequency band comprising the predetermined intermediate frequency,

- Delaying the bandpass-filtered signal by the duration of a time period and linking, in particular superimposing or multiplying, the bandpass-filtered signal with the delayed signal that has been created and possibly modified in this way and thus receiving a received signal corresponding to the useful signal.

A particularly simple possibility of signal coding in all the methods according to the invention provides

- That the useful signal encodes one of symbols in each of the time segments and

- That when modulating the useful signal on the carrier signal within the framework of the generation of the carrier signal, if one of the symbols is present, a phase change of 180 ° with respect to the phase position is carried out in the immediately preceding period and no phase change is made if the other symbol is present.

Furthermore, in order to increase the information transmitted within a time period,

- That the useful signal contains coded information in each of the time segments

- That when modulating the useful signal on the carrier signal within the framework of the generation of the carrier signal when one of the coded information is present, a predetermined phase change associated with the coded information relative to the phase position in the immediately preceding period is carried out, and - If necessary, a predetermined amplitude assigned to the coded information is used when modulating the useful signal on the carrier signal in the course of generating the carrier signal when certain coded information is present.

A particularly easy-to-use embodiment of the invention is characterized:

- by multiplying the bandpass-filtered signal by the possibly modified, delayed signal and in this way obtaining a received signal corresponding to the useful signal, the signal energy of which corresponds to the cosine of the phase jump coded with the respective information and such reconstruction of the respective information, or

by ascertaining the phase difference between the bandpass-filtered signal and the possibly modified, delayed signal by means of a phase detector and in this way obtaining a phase reception signal corresponding to the useful signal, the signal energy of which corresponds to the phase jump coded with the respective information, and in this way reconstructing the respective information.

For the same purpose, it can in particular also be provided that, in addition to the phase jump, the amplitude of the bandpass-filtered signal is also used for the reconstruction of the coded information.

The invention further relates to a method for transmitting data and / or information comprising the following steps:

Creating a carrier signal with a predetermined local transmission frequency,

modulating the useful signal onto the carrier signal symbol-wise and creating a modulated optical data signal for individual time segments, with a phase position of the optical data signal being predetermined by the modulation for each of the time segments,

the phase position of the optical data signal in a time section is determined on the basis of the value of the useful signal available in this time section and the phase position in the respective previous time section, in particular by specifying a phase difference with the phase length in the immediately preceding time section,

- If necessary, weakening or amplifying the modulated optical data signal

Transmission of this data signal via an optical channel, in particular via fiber optic cable or free space, Receiving the transmitted optical data signal with a receiver,

Creating another carrier signal with a predetermined local receiver frequency,

- Delaying the optical data signal by the period of a time period and superimposing the optical data signal with the delayed signal thus created, and possibly modified, and thus obtaining an optical reception signal corresponding to the useful signal,

- Electroptic detection of the optical received signal.

This procedure enables a simple reconstruction of the useful signal in the receiver.

A preferred signal processing in the receiver provides that the following steps are carried out as part of the electroptic detection of the optical received signal:

Creating a further carrier signal with a predetermined local receiver frequency which corresponds to the transmission frequency of the carrier signal or whose difference to the transmission frequency falls below a predetermined value, in particular from 0.1-10 GHz,

multiplicative mixing of the optical received signal and the further carrier signal and thus creating an electrical signal,

Bandpass filtering of the electrical signal with a bandpass filter and thus creating a bandpass filtered signal with a frequency band comprising the difference frequency between the two frequencies of the carrier signals,

- That the useful signal encodes one of several predetermined symbols in each of the time segments and

For highly secure data transmission using quantum communication, it can be provided that in the course of the attenuation of the optical data signal (S ₃ ) an attenuated data signal is generated which has a maximum of 100 photons per symbol, preferably a maximum of 1/10 photons per symbol.

The invention further relates to a receiver. This provides that preferably the signal was created by symbol-wise modulating a useful signal onto an optical carrier signal for individual time segments, with a phase position of the optical data signal being predetermined by the modulation for each of the time segments, and wherein the phase position of the optical data signal in a time segment based on this Time period of available value of the useful signal and of the phase position in the previous time period, in particular by defining a phase difference to the phase length in the previous time period,

full:

- An input for receiving the optical signal

a receiver laser for generating a carrier signal on the receiver side with a predetermined local receiver frequency, the difference to the local transmit frequency contained in the received signal being determined by a predetermined intermediate frequency,

a mixer for multiplicative mixing of the transmitted optical data signal and the further carrier signal, at the output of which an electrical signal is present,

a bandpass filter connected downstream of the mixer for generating a bandpass-filtered signal with a frequency band comprising the predetermined intermediate frequency, and

- An electrical delay unit for delaying the bandpass-filtered signal by the length of a period of time and combining, in particular superimposing or multiplying, the bandpass-filtered signal with the delayed signal thus generated and possibly modified, and in this way obtaining a received signal corresponding to the useful signal.

The main advantage of such a receiver is that it does not have to be synchronized with the transmitter. Furthermore, the invention has the advantage that demodulation and signal conditioning can take place at relatively low frequencies, so that existing or cheap circuits can be used and complex signal reconstruction is not necessary.

An alternative recipient that offers the same benefits provides that

preferably the signal was created by symbol-wise modulating a useful signal onto an optical carrier signal for individual time segments, with a phase position of the optical data signal being predetermined by the modulation for each of the time segments, and wherein the phase position of the optical data signal in a time segment based on this Period available The value of the useful signal and of the phase position in the preceding period, in particular by specifying a phase difference from the phase length in the preceding period,

full:

- An input for receiving the optical signal

a receiver laser for generating a carrier signal on the receiver side with a predetermined local receiver frequency,

In particular, their difference to the local transmission frequency contained in the received signal is determined by a predetermined intermediate frequency,

a delay element for delaying the optical data signal by the length of a period of time and obtaining a delayed optical signal

a superimposition unit for superimposing the delayed signal with the undelayed optical data signal and for generating an optical reception signal.

A preferred signal processing in the receiver provides that

whose difference, in particular from the local transmission frequency contained in the received signal, is determined by a predetermined intermediate frequency,

a mixer for multiplicative mixing of the optical data signal and the further carrier signal, at the output of which an electrical signal is present,

a bandpass filter connected downstream of the mixer for generating a bandpass-filtered signal with a frequency band, in particular comprising the predetermined intermediate frequency, the bandpass-filtered signal being present at the output of the receiving unit.

A preferred arrangement according to the invention comprising a transmitter and a receiver, with which data can be transmitted without synchronization measures contained in the signal, comprises in addition to a transmitter according to the invention:

a transmission laser for generating a carrier signal with a predetermined local transmission frequency,

an input for an electrical useful signal containing the data / information to be transmitted, in which individual symbols are coded in the useful signal in individual successive time segments,

- A modulator for symbol-wise modulating the useful signal on the carrier signal and for creating a modulated optical data signal for individual time segments, wherein the modulator is designed to specify a phase position of the optical data signal for each of the time sections by means of the modulation, and the phase position of the optical data signal in a time section based on the value of the useful signal available in this time section and the phase position in the preceding time section, in particular by definition a phase difference to the phase length in the previous period, and

- If necessary, an attenuator for weakening or amplifying the modulated optical data signal.

A particularly simple possibility of signal coding on the transmitter side in all methods according to the invention provides

- That the modulator is designed to carry out a phase change by 180 ° with respect to the phase position in the immediately preceding period when one of the symbols is present when the useful signal is modulated onto the carrier signal as part of the generation of the carrier signal and no phase change is present when the other symbol is present .

For high-security data transmission using quantum communication, it can be provided that an attenuator is provided at the output of the transmitter, which attenuator is designed to attenuate the optical data signal and to create an attenuated data signal in this way and to transmit it to the transmission channel, which contains a maximum of 100 photons per symbol. preferably at most 1/10 photons per symbol.

In this context, a 1/10 photon is understood to mean a coherent attenuated light which is produced by the fact that a coherent light beam is attenuated so strongly that, on average, only an amount of energy equivalent to one tenth of the energy of a is transmitted during the period of a symbol Corresponds to photons.

Individual exemplary embodiments of the invention are illustrated in more detail with the aid of the following drawing figures.

1 shows a transmitter, a transmission channel and a receiver on which a first embodiment of a method according to the invention is carried out.

1a shows schematically the frequency response of individual signals. 2 shows a transmitter, a transmission channel and a receiver on which a second embodiment of a method according to the invention is carried out.

Fig. 3 shows the functioning of the modulator when generating the modulated signal. Fig. 4 shows a time-delayed modulated signal and the time-delayed useful signal.

FIG. 5 shows a superimposition of the signals shown in FIGS. 3 and 4 and the undelayed useful signal.

6 shows a possible embodiment of a multiplicative mixer as a balanced receiver.

FIG. 7 shows a further embodiment of a receiver with which amplitude and phase-modulated signals can be detected.

1 shows a first embodiment of a method according to the invention, a transmission device comprising a transmitter 100 and a receiver 200 being shown. The transmitter 100 and the receiver 200 are connected to one another via a transmission channel 5.

The transmitter 100 has a laser 101 which generates a carrier signal S1 with a predetermined local transmission frequency f _L oi. For example, a laser can be used to emit red laser light. Such light has a wavelength of 700 nm or a frequency of 430 THz. The oscillation period in such a case is 1 / (430 THz) ~ 2.3 fs. This carrier signal is fed to a modulator 102. Furthermore, the modulator 102 is supplied with a useful signal S ₂ to be transmitted, which can originate from different data sources. For example, the data source can be a code generator for creating a cryptographic key.

The electrical useful signal S ₂ contains data or information to be transmitted, wherein in individual successive time segments T _1; ..., T ₂₀ each individual symbols are encoded in the useful signal S ₂ . The symbols are typically taken from a finite set of symbols. In the present exemplary embodiment, the useful signal has one of two possible symbols "1" or "0", the signal coding of which can be carried out in different ways.

A phase modulation is carried out in the modulator 2, ie the phase of the carrier signal Si of the laser 101 is determined as a function of the predetermined discrete useful signal S ₂ within the relevant time period. For each of the time periods T _1; ..., M ₂₀ a specific phase position of the optical data signal is predetermined by modulation.

In the present case, the phase position defined in the modulated signal in a time segment Ti, T _{20 is} determined on the basis of the symbol value present in the current time segment T, and on the basis of the phase position present in the immediately preceding time segment TM. Specifically, this can be done, for example, by specifying a phase difference between the phase position in the immediately preceding time period T and the phase position in the current time period T on the basis of the symbol prevailing in the respective time period.

The useful signal S ₂ and the modulated optical data signal S ₃ are shown in more detail in FIG. 3, the useful signal S ₂ to be transmitted being able to be generated, for example, at a symbol rate or frequency between 0 and 100 MHz. If the electrical useful signal is band-limited with a frequency f _s , the modulated optical data signal S ₃ is band-limited between the frequencies f _L oi-fs and f _L o _T + fs (FIG. 1 a).

In the implementation variant of the modulator 2 shown in FIG. 3 it is provided that when a symbol "1" is present in the relevant time segment T, there is a phase jump of 180 ° with respect to the phase position of the modulated optical data signal S ₃ in the immediately preceding time segment T. With reference to the modulation signal shown in FIG. 3, at the end of the period T _1; at which the useful signal S _{2 has} the value "1", a phase jump of 180 ° can be seen. The oscillation period of the modulated optical data signal S _{3 shown here} is only to be understood schematically and serves to make it easier to recognize the individual phase jumps. Since the transmission frequency at the modulator is in the range of a few THz, depending on the choice of laser light used, there are regularly several million vibrations within a period of time.

Such behavior in the modulated optical signal S ₃ can also be observed at the beginning of the time periods T ₂ , T ₃ , T ₇ , T ₁₀ , Tu, T ₁₂ , T ₁₃ , T ₁₄ , T ₁₅ , T ₂₀ , T ₂₁ . So has the useful data signal S ₂ at the beginning of the respective time period T _1; ..., T _{20 to} the value "1", the phase position of the modulated optical signal S ₃ is rotated by 180 °. If, on the other hand, the useful signal S _{2 has} the symbol value “0”, as is the case at the beginning of the time segments T ₅ , T ₆ , T ₈ , T ₉ , T ₁₆ , T ₁₇ , T ₁₈ , T ₁₉ , the phase position remains of the modulated signal S ₃ unchanged. In addition to this type of modulation, other different types of modulation or forms of modulation can also be used. For example, there is the possibility of specifying a useful signal S ₂ which is within the individual time segments T _1; ..., T ₂₀ can assume a total of four different values, each of which causes a different phase shift of the modulated optical data signal S ₃ , in each case compared to the modulated optical data signal, in the immediately preceding period.

The optically modulated data signal S ₃ is fed to an attenuator 104 shown in FIG. 1, whereby an attenuated modulated data signal S _{4 is} created. The attenuated modulated data signal S ₄ is reduced to an intensity such that it has a maximum of 100 photons per symbol. For particularly safety-critical applications, an attenuation can be provided in which the attenuated modulated data signal S ₄ preferably only has a maximum of 1/10 photons per symbol. The attenuated modulated data signal S ₄ is fed to the receiver 200 via the channel 5.

The channel 5 is, for example, a glass fiber channel, which can be of different lengths; alternatively, however, a free space transmission can also take place, for example via satellite communication.

In principle, light of different frequencies can be transmitted via a glass fiber or also via free space. Those frequencies are particularly suitable for the present method which can be transmitted particularly advantageously via glass fibers. These are, for example, light with wavelengths in the range of approximately 850 nm or 1310 nm (O band) or wavelengths of 1550 nm (C band) as well as wavelengths between 1570 nm and 1610 nm, which are assigned to the L band.

If free-space communication is used instead of a transmission using a glass fiber cable, different wavelengths can be used for the transmission, frequencies in the UV range, in the visible range and in the infrared range being selected in order to transmit data, for example via satellite communication.

The received modulated optical data signal S ₅ is, after receipt at an input of the receiver 200, fed to a delay and superimposition unit 250, which is implemented by two beam splitters 251, 253 connected in series. The transferred Modulated data signal S ₅ is transmitted to one of the two inputs of the first beam splitter 251 and is split in this first beam splitter 251 over two glass fiber lines 254. One of the two glass fiber lines is equipped with a delay element 252, which delays the light signal arriving at it with a predetermined time delay. The output of the delay element 252 is fed to one of the inputs of the second beam splitter 253. The other output of the first beam splitter 251 is fed to the other output of the second beam splitter 253 via an almost instantaneous line 254. The difference between the delay caused by the delay element 252 and the delay caused by the almost instantaneous line 254 corresponds to the duration of a time period Ti, ..., T ₂₀ .

The delayed modulated optical data signal S _5a has the time profile shown in FIG. 4. 4 also shows the non-delayed course of the useful signal S ₂ provided in the transmitter 100 or in the modulator 102. The oscillation period of the delayed modulated optical data signal S _5a shown in FIG. 4 is only to be understood schematically and serves to make it easier to identify the individual phase jumps. Again, the transmission frequency is in the range of a few THz, depending on the choice of laser light used, so that there are regularly several million vibrations within a period of time.

At one of the two outputs of the second beam splitter 253, which corresponds to the output of the delay and superimposition unit 250, there is consequently a light signal which overlaps the modulated optical data signal S ₅ transmitted via the channel ₅ with itself, but is shifted by that Time duration of a period T _1; ..., M ₂₀ corresponds.

If the two received optically modulated data signals S ₅ , S _5a are now superimposed in the second beam splitter 254, an optical reception signal S _5b corresponding to the useful signal S ₂ results at the output of the second beam splitter 254. This optical received signal S _5b is shown in FIG. 5 together with the useful signal S ₂ . It can be seen that the signal S _5b only in those time segments T _1; ..., T _{20 has} a value different from 0, in which the predetermined useful signal S _{2 has} the symbol value "0". In those periods T _1; ..., T ₂₀ , in which the useful signal S _2, on the other hand, has the symbol value "1", the signal S _{5b has} a significantly lower or vanishing value. The oscillation period [HG1] of the optical shown in FIG Received signal S _5b is only to be understood schematically and serves to make it easier to identify the superimposition.

The optical reception signal S _{5b obtained in this way} is relatively weak, in particular when attenuation is already taking place in the transmitter 100, and can be further improved or made easier to detect with the additional measures shown in FIG. 1. For this purpose, as shown in FIG. 1, an additional receiver laser 206 is provided in the receiver 200, which is designed to generate a further carrier signal S ₆ with a predetermined local receiver frequency f _L o _R. This local receiver frequency f _L o _R can either correspond directly to the transmission frequency f _L oi of the carrier signal 1 or have a predetermined frequency difference f _IF to the transmission frequency f _LO T of the transmission laser 1.

Both the optical received signal S _5b and the further carrier signal S ₆ are fed to an optical mixer 207, which can preferably be designed as a "balanced receiver" (FIG. 6). A specific implementation of a balanced receiver is presented in detail in connection with the second exemplary embodiment of the invention.

This has the essential advantage that it enables multiplicative mixing of the optical received signal S _5b and the further carrier signal S ₆ and in this way an electrical signal S ₇ can be generated which has an electrical frequency which is in the range of an intermediate frequency f _IF lies, which is predetermined by the difference of the frequencies f _L o _T , fi_o _{R of} the two carrier signals Si, S ₆ .

By bandpass filtering this electrical signal S ₇ with a bandpass filter 8, in whose frequency band the intermediate frequency f _IF and / or the difference frequency fi_o _T -fi_o _R lies between the two frequencies of the carrier signals Si, S ₆ , a bandpass filtered electrical signal S ₈ can ultimately be created that have a non-zero and detectable value only in those time segments in which the useful signal has the symbol "0". In the present exemplary embodiment, a frequency difference or an intermediate frequency f _IF of 0.1-10 GFIz is specified.

This signal can be fed to a further signal processing unit 21 1, in order to improve additional signal properties, the signal processing unit 11 can have, for example, an amplifier stage for amplifying the signal and / or a noise suppression unit. A further preferred embodiment of the invention is shown in more detail in FIG. 2, the transmitter 100 corresponding to the transmitter 100 of the first embodiment of the invention. However, the receiver 300 is designed differently from the receiver 200 shown in FIG. 1 and has an input which is connected to the channel 5 and to which the transmitted optical signal S _{5 is} fed.

In the receiver 300, as in the first exemplary embodiment of the invention, a receiver laser 306 is provided, with which a further carrier signal S _{6 is} generated. The optical light frequency of the receiver-side laser 306, referred to as the receiver frequency f _L oi, and of the further carrier signal S ₆ generated by it, is defined in such a way that it has a frequency difference from the local transmission frequency f _{LOT of} the transmission-side laser 101 that is predetermined by an intermediate frequency f _IF . As in the first exemplary embodiment, a frequency difference or an intermediate frequency f _IF of 0.1-10 GFIz can also be specified in the present second exemplary embodiment of the invention. In order for at least one period of a signal modulated to an intermediate frequency to lie within a period of time, the intermediate frequency should advantageously be higher than the symbol frequency. This facilitates the later processing of the superimposed signal.

A multiplicative mixer 307 is provided in the receiver 300, to which both the transmitted optical data signal S ₅ and the further carrier signal S _{6 of} the receiver laser 306 are supplied. In the mixer 307, which is preferably designed as a balanced receiver, the two signals S ₅ , S ₆ fed to the mixer 307 are multiplied with one another. At the output of the mixer 7 there is an electrical signal S ' ₇ which corresponds to the product of the two signals S ₅ , S ₆ fed to the mixer 7. Due to the multiplicative mixing, the transmitted modulated optical signal S ₅ is amplified on the one hand, and on the other hand shifted into the range of the predetermined intermediate frequency f _IF due to the frequency differences.

Such a mixer or balanced receiver 207 comprises, as shown in FIG. 6, a beam splitter 471 on the input side, which overlaps the electromagnetic fields of the optical reception signal S _5b and the carrier signal S ₆ , the reception signal being phase-shifted by 180 ° by means of a special coating, so that there is an output of the beam splitter 471 whose signal amplitude corresponds to the difference between the two incoming beams S ₅ , S ₆ , while a signal is present at the other output of the beam splitter 471 whose signal amplitude corresponds to the sum of the two incoming beams S ₅ , S ₆ . Those at the output of the beam splitter 471 Optical signals are supplied to photodiodes 472, 472, the output signal of which corresponds to the squares of the determined amplitudes of the incoming signals. The two photodiodes 472, 472 are connected in series, the two ends of the series connection being connected to a predetermined voltage source. The connection at which the two photodiodes are connected to one another has a signal S ₇ with a voltage value which is proportional to the product of the two incoming optical signals S ₅ , S ₆ .

A bandpass-filtered electrical signal S ' _{8 is} generated with a bandpass filter 308 connected downstream of the mixer 307. The frequency band B of the bandpass filter

308 comprises the predetermined intermediate frequency f _IF , possibly a bandwidth of 2 ^* f _s , so that the signal amplified by mixer 307 can also pass through bandpass filter 308. Basically, the electrical signal S ' _{8 present} at the output of the bandpass filter 308 corresponds to the modulated optical data signal S ₅ transmitted via the optical channel ₅ , the only difference being that its modulation frequency lies in the range of the intermediate frequency f _IF . However, individual phase jumps are also contained in the electrical signal S ' ₇ or in the bandpass-filtered electrical signal S' ₈ .

In a further step, the bandpass-filtered signal S ' ₈ becomes a delay element

309 supplied, which creates a delayed electrical signal S ' ₉ . The delay takes place with a delay time that corresponds to the duration of a time segment T _1; ..., T ₂₀ corresponds to the useful signal S ₂ .

The time-delayed electrical signal S ' ₉ , like the bandpass-filtered signal S' _{8, is} fed to an adder 310, in which the two signals S ' ₈ , S' ₉ are superimposed to form a reception signal S'i ₀ corresponding to the useful signal. Basically, the bandpass-filtered signal S ' ₈ corresponds to the signal shown in FIG. 3, the time-delayed signal S' ₉ corresponds to the signal shown in FIG. 4. Due to the additive superimposition of the two signals S ' ₈ , S' ₉ in the adder 10, an electrical reception signal S'i _{0 is} generated which corresponds to the signal shown in FIG. 5.

This signal can be fed to a further signal processing unit 31 1, which can be designed like the signal processing unit 31 1 shown in FIG. 1.

With all the signals S ' ₈ , S' ₉ and S'i _{0 shown in} FIGS. 3-5, it should be noted that the representation of the oscillation period or frequency is only to be understood schematically and serves to make it easier to recognize the superimposition and the phase jumps. Provided that the period of the intermediate frequency f _IF corresponds to half the time of a time segment of a symbol, the representation of FIGS. 3-5 is to scale in terms of time. The frequency or oscillation period of these S ' ₈ , S' ₉ and S'i ₀ corresponds to the frequencies and oscillation periods of the signals S ₃ , S _5a or S _5b , nor are they to scale in comparison to the useful signal S ₂ .

In order to reduce an excessive attenuation and the associated noise, and ultimately to be able to use components of lower quality or lower costs, there is also the possibility of reducing the phase jumps and performing a less severe attenuation of the signal.

In the course of the attenuation of the optical data signal S _3, an attenuated data signal S _{4 is} created which has at most a number of photons which corresponds to ten times the phase difference measured in radians. The phase change predetermined by the coded information of the useful signal is predetermined in that the difference in the phase positions of two immediately successive time segments is not greater than a predetermined threshold value of less than 10 °, in particular less than 1/10 °.

FIG. 7 shows a further embodiment of the invention, which allows amplitude and phase demoulation of the transmitted signal. This embodiment is described in more detail below on the basis of the differences from the exemplary embodiment of the invention shown in FIG. 2.

In the present case, the laser light Si generated by the transmitter-side laser 101 is used to generate an amplitude and phase-modulated optical data signal S ₃ by means of the modulator 102 of the transmitter 100. As in the first embodiment of the invention, the phase position of the optical data signal S ₃ in the individual time periods J ..., T _{20 is} determined on the basis of the value of the useful signal S ₂ available in this time period (T,) and the phase position in the previous time period T , specifically by specifying a phase difference to the phase length in the immediately preceding period T. The amplitude of the optical data signal can in principle also be specified as a function of the amplitude of the optical data signal S ₃ . However, this is not the case in the present exemplary embodiment: the amplitude is determined in each case in the useful signal S2 on the basis of the symbol to be transmitted. An amplitude and phase modulation is specified, the phase difference between two phase positions in successive time segments being in each case less than 180 °. In the present exemplary embodiment, a total of eight different pieces of information or symbols can be transmitted in a time window, ie a total of three bits can be transmitted per time window in this specific implementation. For the individual possible information to be transmitted, individual amplitudes and phase jumps are shown in more detail below:

Table 1

As in the first embodiment of the invention, the signal determined in this way is attenuated in the attenuator 104 and transmitted via the channel 5 and transmitted to the receiver 200.

The optical data signal S ₅ transmitted to the receiver is further processed, as in the embodiment of the invention shown in FIG. 2. The transmitted optical data signal S ₅ and the laser light S _{6 from} the receiver-side laser 406 are fed to a balanced receiver as a mixer 407, and a signal S ₇ with a voltage value is generated that is proportional to the product of the two incoming optical signals S ₅ , S ₆ is. The signal thus obtained is fed to a low-pass filter 408. The bandpass-filtered signal S ' ₈ thus obtained is supplied to a delay unit 409 on the one hand. Instead of the adder 310 shown in FIG. 2, the time-delayed electrical signal S ' ₉ and the bandpass-filtered signal S' _{8 are} fed to an electronic multiplier 410 in which the two signals S ' ₈ , S' ₉ form a reception signal S corresponding to the useful signal " _{10 are} superimposed. The received signal S ₁₀ thus obtained is filtered in a low-pass filter 41 1 and forms an output of the receiver at which a phase output signal S'n is present, which corresponds to the phase difference of the useful signal S ₂ and corresponds to the cosine of the phase difference.

In order to be able to reconstruct the phase difference unambiguously from a signal proportional to its cosine, phase jumps which are on the same half-plane are advantageously chosen for the phase coding. In the present case, the phase jumps between 0 ° and 180 ° are selected. However, it is also sufficient if the cosine of the phase shift is clear among the individual symbols chosen.

Furthermore, the bandpass-filtered signal S ' _{8 is} fed to a low-pass filter 412, at the output of which there is an amplitude output signal S' ₁₂ which corresponds to the amplitude of the signal corresponding to the useful signal S ₂ . May be selected from the two output signals S 'n S' _12, the individual symbols, which are encoded in the useful signal S ₂ can be obtained.

A further, particularly simple embodiment, which essentially corresponds to the embodiment shown in FIG. 7, shows that the low-pass filter 412 and the amplitude output signal S _'12 can be omitted.

In the embodiment of the invention shown in FIG. 7, instead of a multiplier 410, a phase detector can also be determined, which delivers at its output a signal whose amplitude or signal energy is proportional to the phase difference of the signals present at its input. The signal generated by the phase detector can thus be used to reconstruct the phase difference and ultimately to reconstruct the transmitted symbol. Such phase detectors are known from the prior art, preferably about AD8302 can be used. (http://www.farnell.com/datasheets/9619.pdf)

During the transmission, for example, a signal coding with a total of four possible symbols or different information can be transmitted per time window; in particular, the same coding can be used that is already shown in Table 1, the amplitude of the signal to be transmitted always remaining the same.

Table 2 If the low-pass filter 412 shown in FIG. 7 is used, there is of course also the possibility of reconstructing the amplitude, so that coding as shown in Table 1 can also be used.

Another alternative embodiment of the invention is shown in more detail in FIG. 8. The transmitter 100 shown in FIG. 8 basically corresponds to the transmitter 100 shown in FIG. 1. Basically, phase modulation is carried out, but the phase shifts generated by phase modulation with the useful signal S ₂ are very small, ie in the range below 20 °, are in particular below 1 °. In contrast to the preceding embodiments of the invention, however, the overall amplitude of the signals is not weakened in such a way that the signal contains only a few photons per time period. Rather, the signal preferably has a number of more than 1,000, in particular more than 10,000, photons per time period T. The minimum number of photons required in the transmitted signal varies depending on the attenuation of channel 5 and the quality of the receiver used, in particular the quality of the multiplicative mixer 554.

In the receiver 500 shown here, the received signal S _{5 is divided} into two partial signals S _6a , S _6b in a beam splitter 552, one of the two partial signals S _{6a being} fed via a delay unit 553 to an input of an optical mixer 554, the other signal S ₆ b, however, is fed to the optical mixer without additional delay. As in the previous exemplary embodiments of the invention, the first partial signal S _{6a is} delayed or a delayed partial signal S _6a 'is generated by the time t of a time segment J- _\ , ..., T ₂₀ .

Due to the lack of attenuation in the signal energy contained in the received signal S ₅ , signal detection can be carried out by means of an optical mixer 552 without the presence of a local receiver laser (206; FIG. 1). The electrical signal S ₇ obtained at the output of the optical mixer 554 depends on how large the phase difference between the respective phase in the current time period and the phase in the immediately preceding time period is.

The electrical output signal of the multiplicative mixer 554 is transmitted to a low-pass filter 555, which preferably has a cut-off frequency which is in the range of 1 / t, where t corresponds to the duration of the time window T. The signal thus obtained has an amplitude that is the cosine of the difference between the two phases of the transmitted Corresponds signal between the current and the immediately preceding time window.

In addition, it is also possible to measure the signal energy separately to compensate for fluctuations in the amplitude of the received signal S5 and to take this signal energy into account when determining the transmitted information. For this purpose, the received signal is split beforehand in a further beam splitter 551 in the beam splitter 552 and passed to a low-pass filter 556, which has essentially the same structure as the low-pass filter 555.

Claims

Claims:

1 . Process for the transmission of data and / or information comprising the following steps:

- Creating a carrier signal (Si) with a predetermined local transmission frequency (f LOT) _J

- Creating an electrical useful signal (S ₂ ) containing the data / information to be transmitted, with individual symbols being encoded in the useful signal (S ₂ ) in individual successive time segments (T _1; T ₂ o),

- Symbol-wise modulating the useful signal (S ₂ ) on the carrier signal (Si) and creating a modulated optical data signal (S ₃ ) for individual periods (T _1; T ₂₀ ), whereby for each of the periods (T _1; T ₂₀ ) by A phase position of the optical data signal is specified for each modulation,

- The phase position of the optical data signal in a time period (T _1; ..., T ₂₀ ) on the basis of the value of the useful signal available in this time period (T,) and the phase position in the preceding time period (T _mi ), in particular by specifying a Phase difference to the phase length in the immediately preceding period (T, 1), is determined,

- If necessary, weakening or amplifying the modulated optical data signal

(S ₃ )

- transmitting this data signal (S ₃ ; S ₄ ) via an optical channel (5), in particular via fiber optic cable or free space,

Receiving the transmitted optical data signal (S ₅ ) with a receiver,

- Creating a further carrier signal (S ₆ ) with a predetermined local receiver frequency (f _L o _F t), the difference to the local transmission frequency (f _L oi) is determined by a predetermined intermediate frequency (f _ZF ), in particular by means of a receiver-side laser ( 306),

multiplicative mixing of the transmitted optical data signal (S ₅ ) and the further carrier signal (S ₆ ) and thus creating an electrical signal (S ' ₇ ),

- bandpass filtering of the electrical signal (S ' ₇ ) with a bandpass filter and thus creating a bandpass filtered signal (S' ₈ ) with a frequency band comprising the predetermined intermediate frequency (f _IF ),

- Delaying the bandpass-filtered signal (S ' ₈ ) by the duration of a period (T _1;

T ₂₀ ) and linking, in particular superimposing or multiplying, the bandpass-filtered signal (S ' ₈ ) with the delayed signal (S' ₉ ) thus created and possibly modified, and in this way obtaining a received signal (S ') corresponding to the useful signal (S ₂ ) ₁₀ )

2. The method according to claim 1, characterized in that

- That the useful signal (S ₂ ) in each of the time segments (T _1; T ₂₀ ) one of each

Symbols coded and

- That in the modulation of the useful signal (S ₂ ) on the carrier signal (Si) within the framework of the generation of the carrier signal (S ₃ ), if one of the symbols is present, a phase change of 180 ° with respect to the phase position in the immediately preceding period (T, _i) is carried out and there is no phase change if the other symbol is present.

3. The method according to claim 1 or 2, characterized in that

- That the useful signal (S ₂ ) contains coded information in each of the time segments (T _1; ..., T ₂₀ )

- That when modulating the useful signal (S ₂ ) on the carrier signal (S ^ in the course of generating the carrier signal (S ₃ ) in the presence of one of the coded information, a predetermined phase change associated with the coded information relative to the phase position in the immediately preceding period (T , _i) is made, and

- If necessary, in the modulation of the useful signal (S ₂ ) on the carrier signal (S ^ in the course of generating the carrier signal (S ₃ ) in the presence of certain coded information, a predetermined amplitude assigned to the coded information is used.

4. The method according to claim 3, characterized

- by multiplying the band-pass filtered signal 'to the optionally modified, delayed signal (S ₍₈ ₉₎ S)' and so obtaining a the useful signal (S ₂₎ corresponding received signal (S 'i _0), the signal energy of the cosine of the respective with the Corresponds to the coded phase jump and thus reconstructs the respective information, or

by determining the phase difference between the bandpass-filtered signal (S ' ₈ ) and the possibly modified, delayed signal (S' ₉ ) by means of a phase detector and in this way obtaining a phase reception signal corresponding to the useful signal (S ₂ ), the signal energy of which corresponds to the respective information corresponds to the coded phase jump and thus reconstruct the respective information.

5. The method according to claim 4, characterized in that in addition to the phase jump, the amplitude of the bandpass-filtered signal (S ' ₈ ) is used for the reconstruction of the coded information.

6. A method of transmitting data and / or information comprising the following steps:

Creating a carrier signal (Si) with a predetermined local transmission frequency (f LOT),

- Symbol-wise modulating the useful signal (S ₂ ) on the carrier signal (S ^ and creating a modulated optical data signal (S ₃ ) for individual periods (T _1; ..., T ₂₀ ), wherein for each of the periods (T _1;. .., T ₂₀ ) a phase position of the optical data signal is predetermined by the modulation,

- If necessary, weakening or amplifying the modulated optical data signal

(S ₃ )

Receiving the transmitted optical data signal (S ₅ ) with a receiver,

- Creating a further carrier signal (S ₆ ) with a predetermined local

Receiver frequency (f _L o _R) ,

- Delaying the optical data signal (S ₅ ) by the duration of a time period and superimposing the optical data signal (S ₅ ) with the thus created and possibly modified delayed signal (S _5a ) and thus obtaining an optical signal corresponding to the useful signal (S ₂ ) Received signal (S _5b ),

- Electroptic detection of the optical received signal (S _5b ).

7. The method according to claim 6, characterized in that the following steps are carried out within the scope of the electroptic detection of the optical received signal (S _5b ):

- Creating a further carrier signal (S ₆ ) with a predetermined local

Receiver frequency (f _L o _R ) _> which corresponds to the transmission frequency of the carrier signal (S ^ or whose difference from the transmission frequency falls below a predetermined value, in particular from 0.1-10 GHz,

multiplicative mixing of the optical received signal (S _5b ) and the further carrier signal (S ₆ ) and thus creating an electrical signal (S ₇ ),

- bandpass filtering of the electrical signal (S ₇ ) with a bandpass filter and thus creating a bandpass filtered signal (S ₈ ) with a frequency band comprising the difference frequency between the two frequencies of the carrier signals (Si, S ₆ ),

8. The method according to any one of claims 6 or 7, characterized in

- That the useful signal (S ₂ ) in each of the time segments (T _1; ..., T ₂₀ ) each encodes one of several predetermined symbols and

- That in the modulation of the useful signal (S ₂ ) on the carrier signal (S ^ in the course of creating the carrier signal (S ₃ ), if one of the symbols is present, a phase change of 180 ° with respect to the phase position is carried out in the immediately preceding period and if the no phase change is made for each other symbol.

9. The method according to any one of the preceding claims, characterized in that, in the course of the attenuation of the optical data signal (S ₃ ), an attenuated data signal is generated which has at most 100 photons per symbol, preferably at most 1/10 photons per symbol, and / or

- That in the course of the weakening of the optical data signal (S ₃ ) a weakened data signal is created which has a maximum of 10,000 photons per symbol, and that the phase change predetermined by the coded information of the useful signal is predetermined by the difference in the phase positions of two successive phases Periods is not greater than a predetermined threshold of less than 20 °, in particular less than 1/10 °.

10. A method of transferring data and / or information comprising the following steps:

- Creating a carrier signal (S ^ with a predetermined local transmission frequency (f _LOT ),

- Creating an electrical useful signal (S ₂ ) containing the data and / or information to be transmitted, with individual symbols being encoded in the useful signal (S ₂ ) in individual successive time segments (T _1; ..., T ₂₀ ),

- Symbol-wise modulating the useful signal (S ₂ ) on the carrier signal (S ^ and creating a modulated optical data signal (S ₃ ) for individual periods (T _1; ..., T ₂₀ ), whereby for each of the time segments (T _1; T ₂₀ ) is given a phase position of the optical data signal by the modulation,

- The phase position of the optical data signal in a time period (T _1; T ₂₀ ) based on the value of the useful signal available in this time period (T,) and the phase position in the preceding time period (T _mi ), in particular by specifying a phase difference to the phase length in immediately preceding time period (T _m 1), and the difference between the phase positions of two immediately successive time periods is not greater than a predetermined threshold value,

- If necessary, weakening or amplifying the modulated optical data signal

(S ₃ ),

- Receiving the transmitted optical data signal (S ₅ ) with a receiver, the following steps being carried out in the receiver:

a) delaying the incoming signal (S ₅ ) by the duration of a period (T _1; ...,

T ₂ o),

b) multiplicative mixing of the transmitted optical data signal (S _6b ) and the delayed signal (S _6a ) and thus creating an electrical signal (S ' ₇ ),

c) bandpass filtering the electrical signal (S ' ₇ ) provided in step b) by multiplicative mixing with a bandpass filter (555) and measuring the signal energy of the bandpass filtered electrical signal (S ₇ ) and thus obtaining a received signal corresponding to the useful signal (S ₂ ).

1 1. The method according to claim 10, characterized in that the phase change predetermined by the coded information of the useful signal is predetermined, wherein the difference in phase between two immediately successive time segments is not greater than a predetermined threshold of less than 20 °, in particular less than 1/10 °.

12. The method according to claim 10 or 1 1, characterized in

- That the total energy of the transmitted incoming signal (S ” ₅ ) is at least a factor 10000 greater than the portion of the signal energy that is caused by the phase jumps, and / or

- That in the course of the attenuation of the optical data signal (S ₃ ) a weakened data signal (S ₄ ) is created and transmitted via the channel (5), which has at most a number of photons, which corresponds to ten times the phase difference, measured in radians .

13. The method according to any one of the preceding claims, characterized in that the upper band limit of the bandpass filter is selected around a frequency 1 / T, where T corresponds to the duration of a period.

14. Receiver (300; 400) for receiving an optical signal (S ₅ ), which were created in particular according to one of the preceding claims,

wherein preferably the signal (S ₅ ) was generated by symbol-wise modulating a useful signal (S ₂ ) onto an optical carrier signal (Si) for individual time periods (T _1; ..., T ₂₀ ), whereby for each of the time periods (T, ) a phase position of the optical data signal was predetermined by the modulation, and the phase position of the optical data signal in a time period (T,) on the basis of the value of the useful signal available in this time period (T) and the phase position in the preceding time period (T), in particular by specifying a phase difference to the phase length in the preceding time period (T),

full:

- an input for receiving the optical signal (S ₅ )

- A receiver laser (306) for generating a carrier signal (S ₆ ) on the receiver side with a predetermined local receiver frequency (fi_o _F t), the difference to the local transmission frequency (f _L oi) contained in the received signal by a predetermined intermediate frequency (f _IF ) is determined

a mixer (307) for multiplicative mixing of the transmitted optical data signal (S ₅ ) and the further carrier signal (S ₆ ), at the output of which an electrical signal (S ' ₇ ) is present,

- A bandpass filter (308) connected downstream of the mixer (307) for generating a bandpass-filtered signal (S ' ₈ ) with a frequency band comprising the predetermined intermediate frequency (f _IF ), and

- An electrical delay unit (309) for delaying the bandpass-filtered signal (S ' ₈ ) by the time of a period (T _1; ..., T ₂₀ ) and linking, in particular superimposing or multiplying, the bandpass-filtered signal (S' ₈ ) with the delayed signal (S ' ₉ ) thus created and possibly modified and thus receiving a received signal (S' ₁₀ ) corresponding to the useful signal (S ₂ )

15. Receiver (200) for receiving an optical signal (S ₅ ), which were created in particular according to one of the preceding claims, wherein preferably the signal (S ₅ ) was generated by symbol-wise modulating a useful signal (S ₂ ) onto an optical carrier signal (Si) for individual time segments, with a phase position of the optical data signal being predetermined for each of the time segments by the modulation, and wherein the phase position of the optical data signal in a time segment was determined on the basis of the value of the useful signal available in this time segment and the phase position in the preceding time segment, in particular by specifying a phase difference to the phase length in the previous time segment,

full:

- an input for receiving the optical signal (S ₅ )

a receiver laser (206) for generating a carrier signal (S ₆ ) on the receiver side with a predetermined local receiver frequency (f _LOR ),

In particular, their difference from the local transmission frequency (f _LOT ) contained in the received signal is determined by a predetermined intermediate frequency (f _IF ),

- A delay element (252) for delaying the optical data signal (S ₅ ) by the duration of a period (T _1; ..., T ₂₀ ) and receiving a delayed optical signal delayed signal (S _5a )

- A superimposition unit (253) for superimposing the delayed signal (S _5a ) with the undelayed optical data signal (S ₅ ) and for generating an optical reception signal (S _5b ).

16. Receiver according to claim 15, characterized by

a receiver laser (206) for generating a carrier signal (S ₆ ) on the receiver side with a predetermined local receiver frequency (f _L o _F t),

whose difference, in particular from the local transmission frequency (f _L oi) contained in the received signal, is determined by a predetermined intermediate frequency (f _IF ),

a mixer (207) for multiplicative mixing of the optical data signal (S _5b ) and the further carrier signal (S ₆ ), at the output of which an electrical signal (S ₇ ) is present,

- A bandpass filter (208) connected downstream of the mixer (207) for generating a bandpass-filtered signal (S ₈ ) with a frequency band, in particular comprising the predetermined intermediate frequency (f _IF ), the bandpass-filtered signal (S ₈ ) being present at the output of the receiving unit.

17. Arrangement comprising a receiving unit (200) according to one of claims 14 to 16 and comprising the transmitting unit (100) connected to the receiving unit (200) via a channel (5)

- A transmission laser (101) for generating a carrier signal (Si) with a predetermined local transmission frequency (f LOT),

an input for an electrical useful signal (S ₂ ) containing the data / information to be transmitted, in which individual symbols are coded in the useful signal in individual successive time segments,

- A modulator (103) for symbol-wise modulating the useful signal (S ₂ ) on the

Carrier signal (Si) and for creating a modulated optical data signal (S ₃ ) for individual time periods (T _1; T ₂₀ ), the modulator being designed for each of the

Periods (T _1; ..., T ₂₀ ) to specify a phase position of the optical data signal by the modulation, and the phase position of the optical data signal in a time period (T _1; ..., T ₂₀ ) on the basis of the in this time period (T ,) to determine the available value of the useful signal (S ₂ ) and the phase position in the previous time period (T,), in particular by specifying a phase difference to the phase length in the previous time period (T _mi ), and

- If necessary, an attenuator (104) for weakening or amplifying the modulated optical data signal (S ₃ ).

18. Arrangement according to claim 17, characterized in

- That the useful signal (S ₂ ) encodes one of several predetermined symbols in each of the time segments and

- That the modulator (102) is designed to modulate the useful signal (S ₂ ) on the carrier signal (Si) within the framework of the generation of the carrier signal (S ₃ ) in the presence of one of the symbols, a phase change by 180 ° compared to the phase position in immediately preceding period and do not change the phase when the other symbol is present.

19. The arrangement according to claim 17 or 18, characterized in that an attenuator (104) is provided at the output of the transmitter (100), which is designed to attenuate the optical data signal (S ₃ ) and thus an attenuated data signal (S ₄ ) to create and forward in the transmission channel (5), which has at most 100 photons per symbol, preferably at most 1/10 photons per symbol.