WO2000001097A1

WO2000001097A1 - Method and device for optically transmitting data via optical waveguides

Info

Publication number: WO2000001097A1
Application number: PCT/DE1999/001864
Authority: WO
Inventors: Claus-Georg MÜLLER
Original assignee: Ams Optotech Vertrieb Gmbh
Priority date: 1998-06-26
Filing date: 1999-06-25
Publication date: 2000-01-06
Also published as: DE19828614A1

Abstract

The invention relates to a method for optically transmitting data via optical waveguides during which the electric signal (Sel) or optical information signal (Sopt) to be transmitted is split into a plurality of partial signals (Sel1 to Seln) each having a lower bandwidth. In addition, each partial signal (Sel1 to Seln) is converted into an optical partial signal (Sopt1 to Soptn) each having different medium wave lengths (μ1 to μn) or having an optical carrier frequency and/or having a different orthogonal polarization. Optical partial signals (Sopt1 to Soptn) are transmitted on an optical waveguide which forms the transmission path (7). The optical partial signals (Sopt1 to Soptn) are each separately detected again at the end of the transmission path (7) and are composed into the information signal (Sel) to be transmitted. The invention also relates to a transmitting unit, a receiving unit, and to a complete system for carrying out the inventive method.

Description

Method and device for optical data transmission via optical fibers

The invention relates to a method and a device for optical data transmission via optical fibers.

For data transmission via optical waveguides, an electrical signal is usually converted by means of an optical transmission element, for example a laser diode, into an optical signal with a transmission spectrum with a specific central wavelength and a specific optical bandwidth and is coupled into an optical waveguide. At the end of the transmission path, the signal is converted optically and electrically and processed further. If transmission over the desired length is not possible due to the bandwidth or dispersion limitation of the optical waveguide, amplifiers are usually used in the transmission link. This can be a conventional repeater amplifier or optical amplifier, e.g. Fiber amplifier, act. However, only a fraction of the transmission capacity of an optical fiber is used in this method.

To make better use of the transmission capacity of an optical waveguide, it is known to transmit a plurality of electrical information signals in wavelength division multiplexing or polarization multiplexing via a single optical waveguide. The individual electrical signals are each converted into optical information signals, the optical transmission elements, usually narrow-band ones

Laser diodes, each generating optical signals with a transmission spectrum with different center wavelengths or optical signals with mutually orthogonal polarization directions. These optical signals will be then combined using a mostly passive coupler to form an optical wavelength division multiplex signal and transmitted to a single optical waveguide. At the end of the transmission path, the wavelength division multiplex signal is again divided into the individual optical signals. These are implemented optically and electrically for further processing. Through the multiplex

Transmission results in an optimal or improved utilization of the transmission capacity of the optical waveguide.

The transmission system is usually designed simultaneously with the planning of the transmission route. This has the advantage that

Transmission system and transmission route can be optimally matched to the respective application. The transmission path is designed so that the total attenuation and in particular the entire dispersion or the optical bandwidth in each optical channel enables the transmission of the signal in question. Especially with multimode

The bandwidth limitation often plays a larger role than the attenuation limitation. If necessary, repeater amplifiers must then be used in the line. However, this is associated with a relatively high outlay, since for this purpose, complex structural measures are usually required in addition to the necessary circuitry outlay.

The present invention is therefore based on the object of providing a method for optical data transmission via optical waveguides and / or transmitting and receiving units suitable for this purpose, the transmission of a signal over a bandwidth-limited or dispersion-limited path being made possible with relatively little effort. The invention solves this problem with the features of claims 1 and 3 and 6.

The starting point for the invention is, for example, the case that an (electrical) information signal is present at the beginning of a transmission link, which is no longer or no longer transmitted with the desired quality due to the dispersion limitation or bandwidth limitation of the present transmission link or the individual optical fibers of the transmission link can. The information signal is preferably a uniform signal, for example the signal for a television channel,

Voice channel or the like. Of course, however, it can also already be an information signal that contains several individual pieces of information, for example several television or voice channels. Such a combined information signal is usually available as a time-division multiplex signal.

The invention is now based on the knowledge that such an information signal, which cannot be transmitted as a uniform optical signal over the existing transmission path, is first split into several partial signals, each partial signal is converted into an optical partial signal and the optical partial signals are simultaneously applied the existing optical transmission path are transmitted. The partial optical signals have a spectrum of different center wavelengths or a different optical carrier frequency and / or different orthogonal polarization directions.

In this way, the optical partial signals at the end of the transmission path can be converted into individual optical signals in a corresponding receiving unit Partial signals are separated and converted into electrical partial signals. The partial electrical signals can then in turn be combined to form the original information signal.

This has the advantage that such (electrical) information signals can also be transmitted via an already existing optical transmission path whose bandwidth-length product would be too small at a predetermined transmission wavelength or whose dispersion would be too large at a predetermined transmission wavelength to To be able to transmit information signal at all or with sufficient quality using a single optical transmission element (with finite width of the transmission spectrum). In contrast to existing wavelength division multiplex transmission systems, in which various individual electrical information signals are converted into corresponding optical information signals and transmitted on a transmission link, the invention follows the path of firstly separating an existing electrical information signal into electrical partial signals, which are then divided into wavelength division multiplexes or polarizations -Multiplex to transmit and then summarize again to the (uniform) information signal.

This transmission method according to the invention or the ones suitable for this

Transmitter and receiver units are particularly suitable for increasing the capacity of existing transmission links, especially in the case of multimode optical fibers. The electrical information signal with higher bandwidth or higher bit rate generated to increase the capacity only has to be supplied to a transmission unit according to the invention and the optical output of the

Transmitter unit can be connected to the existing transmission path. On the receiving side, the optical output of the transmission link must be connected to the input of a receiving unit according to the invention and In turn the receiving unit produces the transmitted information signal with a higher bandwidth or higher bit rate. Structural interventions in the transmission path, as would be the case when using repeater amplifiers, are not necessary.

According to one embodiment of the invention, the information signal, which is present in digital form, is broken down into partial digital signals according to a pre-determined processing instruction. For this purpose, for example, every nth bit or every nth group of m bits can be assigned to one of n partial signals. In this case, the bit duration of the partial signals can in each case be chosen to be greater by a factor n than the bit duration of the original digital information signal.

The combination of the transmitted optical partial signals and converted into electrical partial signals can then take place in the reverse manner. For this purpose, one bit or a group of m bits of one of the n partial signals are successively combined to form the original digital information signal in a defined sequence. If the bit duration of the partial signals for transmission over the optical transmission link has been increased, this must of course be reduced again by the appropriate factor before it is possible to combine them into the electrical information signal.

Further embodiments of the invention result from the subclaims.

The invention is illustrated below with the aid of one in the drawing

Embodiment explained in more detail. The single drawing shows a schematic representation of a system for optical data transmission over a single optical waveguide according to the invention.

The system for optical data transmission shown in the figure comprises a transmission unit 3, the output 5 of which is connected to a transmission link 7. The transmission link is an optical waveguide, which is usually provided within a laid cable. Furthermore, the system 1 for optical data transmission comprises a receiving unit 9, the optical input 11 of which is connected to the end of the transmission link 7 or the optical waveguide in question.

An electrical information signal S _e i is fed to the electrical input 13 of the transmission unit 3. To split the electrical information signal S _e ι into electrical partial signals S _e ιι to S _e ι _n , the transmission unit 3 comprises a transmission

Signal processing unit 15.

In the electrical information signal S _e ι it may be for example a digital signal with a predetermined (high) bit rate act, wherein the transmitting Signalverabeitungseinheit 15 from the signal present at input 13 information signal S _e i partial signals S _e n to S _e i _n generated which have a lower bit rate, preferably a factor of n. For this purpose, the transmission signal processing unit 15 can assign each nth bit or every nth group of m bits of the original information signal S _e ι to the individual partial signals in a predetermined order.

The transmission signal processing unit 15 supplies each of the partial signals S _ell to S _e _{n n} generated by it to an optical transmission element 17 ₁ to 17 _n . Each of the opti- see transmission elements converts the relevant electrical partial signal S _e n to S _eln into an optical partial signal S _opt ι to S _optn . The individual optical partial signals are combined by means of an optical coupling unit 19 to form an optical information signal S _opt , which is fed to the transmission link 7. Each of the optical partial signals S _opt ι to S _optn has a transmission spectrum with a different center wavelength, the distances between adjacent center wavelengths being selected such that a sufficiently low crosstalk arises. However, the partial optical signals can also have different, mutually orthogonal polarization directions, so that transmission in polarization (mode) multiplexing is possible. For this purpose, the transmission link 7 will preferably be in the form of a polarization-maintaining single-mode fiber. In this way, two optical partial signals with mutually orthogonal polarization directions can be transmitted at each wavelength.

The optical information signal S _opt is fed to a further optical coupling unit 21 in the receiving unit 9. The optical coupling unit 21 separates the optical information signal S _opt back into the individual component optical signals S i to S _opt _OPTN on. For the sake of simplicity, these optical partial signals on the receiving side are referred to as the optical partial signals on the transmitting side.

Of course, however, the optical optical signals on the receiving end are acted upon by the transmission characteristics of the transmission link.

The optical coupling units 19 and 21 can be implemented in the usual way. In the case of the coupling unit 19, for example, a simple, correspondingly broadband nx 1 coupler can be used. On the receiving side, the coupling unit 21 has to perform a filter function in addition to its function of splitting into different signal paths, so that at the output the coupling unit only receives the desired optical partial signal in question. For example, the optical coupling unit 21 can be designed as a phased array. Such a phased array must have an optical input and n optical outputs in accordance with the desired topology of the coupling unit 21. The design as a phased array ensures that a bandpass filter characteristic can be achieved between the common input and each output.

Each optical output of the optical coupling unit 21 is connected to an optical receiving element 23 ₁ to 23 _n , the receiving _{elements converting} the optical partial signals S _opt ι to S _optn into the electrical partial signals S _e ιι to S _e ι _n . If it is to be _n the same for the information to be transmitted signal is a digital signal, the emfangsseitigen partial electric signals S _e can ιι to S _e ι _n in a row of the possible complete restoration with the empfangsseiti- gen partial electric signals S _e ιι to S _e ι .

The reception unit 9 has a reception signal processing unit 25 for regenerating the electrical partial signals and for combining the electrical partial signals S _eU to S _e ι _n into the transmitted electrical information signal S _e ι.

For the example explained above of splitting a digital electrical signal S _e ι into n digital electrical partial signals S _e ιι to S _e ι _n , the received signal processing unit 25 can combine the individual electrical partial signals into the electrical information signal S _e ι in such a way that that in the same order in which the electrical information signal is broken down into individual electrical partial signals, one bit or a group of m bits one of the n Partial signals S _e ιι to S _e ι _n taken and is assembled in this order to the digital information signal S _e ι.

The bit duration of the partial signals can be greater by a factor of n than the bit duration of the information signal to be transmitted. Has been broadcast

Signal processing unit 15 after the splitting of the information signal into the individual sub-signals increases the bit duration to reduce the bandwidth required for the transmission of the individual sub-signals, the received signal processing unit 25 must independently increase the bit duration before combining the electrical sub-signals into the entire information signal reduce again by the same factor.

Claims

Method and device for optical data transmission via optical fiber

1. Method for optical data transmission via optical fibers

a) in which the electrical (S _e ι) or optical information signal (S _opt ) to be transmitted is broken down into several partial signals (S _e π to S _e ι _n ), each with a smaller bandwidth,

b) in which each partial signal (S _e n to S _e ι _n ) is converted into an optical partial signal (S _optl to S _opm ), each with a different center wavelength (λi to λ _n ) or optical carrier frequency and / or different orthogonal polarization,

c) in which the optical partial signals (S _optl to S _optn ) are _transmitted on an optical waveguide forming the transmission link (7), and

d) in which the optical partial signals (S _opt ι to S _optn ) at the end of the transmission link (7) are again separately detected and combined to form the information signal (S _e ι) to be transmitted.

A method according to claim 1, characterized in that the optical waveguide is a multimode optical waveguide.

3. Sending unit for optical signal transmission, in particular for performing the method according to one of the preceding claims,

a) with a transmission signal processing unit (15) for separating an electrical information signal to be transmitted (S _e ι) into several electrical partial signals (S _e n to S _em ),

b) with a plurality of optical transmission elements (17 to 17 _n ), to which the electrical partial signals (S _e π to S _e ι _n ) are fed and which from the electrical partial signals (S _opt ι to S _optn ) _include optical partial signals

Generate transmission spectra each with different center wavelengths (λi to λ _n ) or carrier wavelengths and / or different orthogonal polarization, and

c) with a coupling unit (19), which combines the optical partial signals (S _opt ι to S _optn ) on an optical information signal (S _opt ) and feeds an optical output (5).

4. Transmitting unit according to claim 3, characterized in that the transmitting signal processing unit (15) breaks down a digital information signal according to a predetermined processing rule into digital partial signals (S _e ιι to S _e ι _n ).

5. Transmitting unit according to claim 4, characterized in that the transmitting signal processing unit (15) every nth bit or every nth group of m

Bit assigned to one of n partial signals (S _e n to S _e ι _n ).

6. Transmitting unit according to claim 5, characterized in that the bit duration of the partial signals (S _e n to S _e ι _n ) is greater by a factor n than the bit duration of the digital information signal (S _e] ).

7. receiving unit for optical signal transmission, in particular for performing the method according to one of claims 1 or 2,

a) with a coupling unit (21) which separates an optical signal (S _opt ) which is present at an optical input (11) and is transmitted in wavelength division multiplex and / or polarization multiplex into the optical partial signals (S _opt i to So _P tn),

b) with a plurality of optical receiving elements (23ι to 23 _n ), to which the optical partial signals (S _opt ι to S _optn ) are supplied and which generate electrical partial signals (S _e π to S _e ι _n ) from the optical partial signals and

c) with a received signal processing unit (25) for combining the electrical partial signals (S _e n to S _e ι _n ) into an electrical information signal (S _e ι) according to a predetermined regulation.

8. Receiving unit according to claim 7, characterized in that the received signal processing unit (25) _combines digital partial signals (S _e n to S _eln ) according to a predetermined processing _rule to form a digital _information signal (S _e ι).

9. receiving unit according to claim 8, characterized in that the receiving signal processing unit (25) according to a predetermined Sequence combines one bit or a group of m bits of one of n sub-signals (S _e n to S _e in) in succession to form a digital information signal (S _e i).

10. Receiving unit according to claim 9, characterized in that the bit duration of the partial signals (S _e n to S _e ι _n ) is greater by a factor n than the bit duration of the digital information signal (S _e ι).

11. System for optical data transmission, in particular according to the method according to one of claims 1 or 2, with a transmitting unit (3) according to one of claims 3 to 6 and a receiving unit (9) according to one of claims 7 to 10.