Analog signal processing-based dispersion analog transmission link and dispersion analog method

Abstract

The application belongs to the field of optical fiber communication, and discloses a dispersion simulation transmission link and a dispersion simulation method based on analog signal processing. The dispersion simulation transmission link comprises a coherent transmitter, an IQ modulator, lasers with different wavelengths, an interference receiving chip (ICR), a Bragg dispersion compensation grating (FBG-DCM) and a coherent receiver. Data is sent from the coherent transmitter, first passes through the ICR to convert the optical field into the electrical domain, and is modulated into a new optical field by the IQ modulator. The output end of the ICR has two optional paths. The first path is connected to the IQ modulator, uses the secondary emission of intrinsic light with different wavelengths, and converts the wavelength to the FBG-DCM compensation window. After the above steps, the original wavelength is converted by the IQ modulator after being received by the ICR for transmission, so that the superposition of negative dispersion is realized. The second path is connected to the IQ modulator, uses the secondary emission of intrinsic light with different wavelengths, realizes the phase conjugation and converts to the FBG-DCM compensation window at the same time. After the above steps, the ICR receives and realizes the superposition of positive dispersion.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication, and particularly relates to a dispersion simulation transmission link and dispersion simulation method based on analog signal processing. Background Technology

[0002] Optical communication networks, as the cornerstone of modern information society, are developing at an unprecedented pace, carrying the explosive growth of global data traffic. Transoceanic submarine optical cable systems, in particular, serve as the lifeline of communication connecting continents, and their transmission capacity and reliability are crucial. However, transmission links spanning thousands of kilometers of ocean face a fundamental physical challenge: ultra-large cumulative dispersion. This effect, caused by the difference in propagation speed of different wavelengths of light signals in optical fibers, accumulates linearly with distance, reaching hundreds of thousands of picoseconds per nanometer (ps / nm) in transoceanic links spanning thousands of kilometers. This severely distorts signal pulses and is one of the key factors limiting the performance of high-speed coherent transmission systems. To effectively study and verify the tolerance of novel modulation formats, digital signal processing algorithms, and receiver performance to ultra-large dispersion in a laboratory environment, tools capable of accurately simulating this extreme dispersion effect are urgently needed. Directly using thousands of kilometers of real optical fiber for experiments is clearly impractical. The high cost, huge space occupation, and the additional noise degradation (manifested as a sharp drop in OSNR) and increased system complexity resulting from the introduction of numerous erbium-doped fiber amplifiers (EDFAs) due to signal attenuation make this method almost infeasible in laboratory research.

[0003] However, an ideal laboratory dispersion simulator not only needs to reproduce the large-scale positive dispersion (+CD) generated by transoceanic links, but also must be able to simulate the large-scale negative dispersion (-CD) required for dispersion pre-compensation at the transmitter. Taking the widely used G.652 standard single-mode fiber as an example, its typical dispersion coefficient is approximately +17 ps / (nm·km). This means that simulating the total dispersion of a 6000-kilometer link would be as high as +102,000 ps / nm; while to perform pre-compensation at the transmitter, an equivalent dispersion of -102,000 ps / nm needs to be generated at the same location.

[0004] Traditionally, dispersion compensation modules (DCMs) based on dispersion-compensating fiber (DCF) were used to generate negative dispersion and were applied in early transoceanic system experiments. However, when simulating large-scale dispersion generated by transmissions over thousands of kilometers, the required DCF length can reach tens or even hundreds of kilometers. This not only results in bulky and cumbersome equipment, but more importantly, the high loss characteristics of the DCF itself introduce significant signal attenuation. In contrast, thanks to industrial production, Bragg grating-based DCMs (FBG-DCMs) have become an attractive alternative for simulating high dispersion due to their compact size, low insertion loss, and relatively low cost. A very small FBG-DCM can generate the equivalent dispersion provided by hundreds of kilometers of DCF. However, the inherent limitation of FBG-DCMs is that their dispersion compensation bandwidth (or center wavelength tuning range) is typically very narrow, often only a few tenths of a nanometer. For the numerous wavelength channels covering the entire C-band (~35-40nm) in today's wavelength division multiplexing (WDM) systems, the vast majority of channels cannot fall within the effective compensation window of a single FBG-DCM, which severely limits its application in broadband, multi-wavelength dispersion simulation scenarios.

[0005] Therefore, the core requirement for a practical dispersion simulator for future high-capacity coherent transmission system research is to be able to flexibly and efficiently generate positive and negative dispersion over a very large range (± hundreds of thousands of ps / nm). Summary of the Invention

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a dispersion simulation transmission link and dispersion simulation method based on analog signal processing, so as to solve the problems that the existing technology cannot achieve large-range positive and negative dispersion simulation and has high cost.

[0007] To achieve the above objectives, the present invention provides a dispersion analog transmission link based on analog signal processing, comprising:

[0008] A coherent transmitter, a first coherent receiver chip, a first IQ modulator, a second coherent receiver chip, a second IQ modulator, a Bragg dispersion compensation grating module, and a coherent receiver;

[0009] The optical signal generated by the coherent transmitter is input to the first coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. These X / Y polarized baseband electrical signal components are divided into non-conjugate and conjugate signals. The non-conjugate signal drives the first IQ modulator, outputting a first non-conjugate optical signal to achieve wavelength conversion. The wavelength of the first non-conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module, while retaining the phase information of the optical signal. The conjugate signal drives the first IQ modulator, outputting a first conjugate optical signal, achieving both wavelength conversion and phase conjugation of the optical signal. The wavelength of the first conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module. The two optical signals are then loaded with the target color by the Bragg dispersion compensation grating module. The first non-conjugate signal, after being loaded with the target dispersion value, is input to the second coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output the second non-conjugate optical signal, achieving wavelength conversion. The wavelength of the second non-conjugate optical signal is converted to the original wavelength, effectively generating a signal with negative dispersion at the original wavelength. The conjugate signal, after being loaded with the target dispersion value, is input to the second coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output the second conjugate optical signal, achieving wavelength conversion while simultaneously achieving phase conjugation of the conjugate signal. The wavelength is converted to the original wavelength, effectively generating a signal with positive dispersion at the original wavelength. The signals with negative dispersion and positive dispersion are received by the coherent receiver.

[0010] This invention also provides a dispersion simulation method for a dispersion simulation transmission link based on analog signal processing, comprising the following steps:

[0011] The original wavelength optical signal is input to the first coherent receiving chip and demodulated into X / Y polarized baseband electrical signal components. The X / Y polarized baseband electrical signal components include non-conjugate signals. The non-conjugate signals drive the first IQ modulator to output a first non-conjugate optical signal, achieving wavelength conversion. The wavelength of the first non-conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module, preserving the phase information of the optical signal. The non-conjugate signal is loaded with a target dispersion value through the Bragg dispersion compensation grating module. The non-conjugate signal after being loaded with the target dispersion value is input to the second coherent receiving chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output a second non-conjugate optical signal, achieving wavelength conversion. The wavelength of the second non-conjugate optical signal is converted to the original wavelength, effectively generating a signal with negative dispersion at the original wavelength.

[0012] This invention also provides a dispersion simulation method for a dispersion simulation transmission link based on analog signal processing, comprising the following steps:

[0013] The original wavelength optical signal is input to the first coherent receiving chip and demodulated into X / Y polarized baseband electrical signal components. The X / Y polarized baseband electrical signal components include a conjugate signal. The conjugate signal drives the first IQ modulator to output a first conjugate optical signal, achieving wavelength conversion and phase conjugation of the conjugate signal. The wavelength of the first conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module. The conjugate signal is loaded with a target dispersion value through the Bragg dispersion compensation grating module. The conjugate signal after loading the target dispersion value is input to the second coherent receiving chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output a second conjugate optical signal, achieving wavelength conversion and phase conjugation of the conjugate signal. The wavelength of the second conjugate optical signal is converted to the original wavelength, effectively generating a signal with positive dispersion at the original wavelength.

[0014] The present invention also provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0015] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described method.

[0016] The present invention also provides a computer program product, including a computer program or instructions, which, when executed by a processor, implement the steps of the method described above.

[0017] In summary, compared with the prior art, the present invention, through the above-described technical solution, first passes the data transmitted from the coherent transmitter through an ICR to convert the optical field into a radio frequency (RF) domain. The RF signal then remodulates the optical field into a new optical field. At the output end of the RF domain, optional features include... Two paths are available. The first path will... The first path connects directly to the IQ modulator, utilizing the secondary emission of intrinsic light at different wavelengths to convert it to the center wavelength of the FBG-DCM compensation window. Then, after the same steps, the signal is received by the ICR and converted back to the original wavelength for transmission, achieving the superposition of negative dispersion. The second path involves... Connected to an IQ modulator, the intrinsic light of different wavelengths is emitted twice to achieve phase conjugation. This phase is then converted to the center wavelength of the FBG-DCM compensation window, received by an ICR, and subjected to the same phase conjugation process to achieve positive dispersion superposition. This invention cleverly utilizes the differential drive characteristics of the IQ modulator. By selecting the positive (p) or negative (n) terminals of the in-phase (I) and quadrature (Q) components of the ICR output to the four RF input ports of the IQ modulator, the complex conjugation state of the output light field can be precisely controlled. This feature allows the simulator to flexibly generate the desired ultra-large positive or negative dispersion—selecting specific port connection combinations can achieve signal phase conjugation (corresponding to negative dispersion simulation) or non-conjugation (corresponding to positive dispersion simulation). Attached Figure Description

[0018] Figure 1 This is a structural diagram of a transmission link for a dispersion simulation method based on analog signal processing, as shown in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram illustrating a dispersion simulation method based on analog signal processing, as shown in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] To illustrate the technical solution described in this invention, specific embodiments are described below.

[0022] This invention provides a dispersion analog transmission link based on analog signal processing, comprising:

[0023] A coherent transmitter, a first coherent receiver chip, a first IQ modulator, a second coherent receiver chip, a second IQ modulator, a Bragg dispersion compensation grating module, and a coherent receiver;

[0024] The optical signal generated by the coherent transmitter is input to the first coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. These X / Y polarized baseband electrical signal components are divided into non-conjugate and conjugate signals. The non-conjugate signal drives the first IQ modulator, outputting a first non-conjugate optical signal to achieve wavelength conversion. The wavelength of the first non-conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module, while retaining the phase information of the optical signal. The conjugate signal drives the first IQ modulator, outputting a first conjugate optical signal, achieving both wavelength conversion and phase conjugation of the optical signal. The wavelength of the first conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module. The two optical signals are then loaded with the target color by the Bragg dispersion compensation grating module. The first non-conjugate signal, after being loaded with the target dispersion value, is input to the second coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output the second non-conjugate optical signal, achieving wavelength conversion. The wavelength of the second non-conjugate optical signal is converted to the original wavelength, effectively generating a signal with negative dispersion at the original wavelength. The conjugate signal, after being loaded with the target dispersion value, is input to the second coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output the second conjugate optical signal, achieving wavelength conversion while simultaneously achieving phase conjugation of the conjugate signal. The wavelength is converted to the original wavelength, effectively generating a signal with positive dispersion at the original wavelength. The signals with negative dispersion and positive dispersion are received by the coherent receiver.

[0025] Example 1

[0026] After the data is transmitted from the coherent transmitter, it first passes through the ICR. The coherent heterodyne receiver converts the optical field into the radio frequency (RF) domain, and the RF signal remodulates the optical field into a new optical field. The output terminals of the electrical domain ICR can be selected from XIp, XIn, XQp, XQn, YIp, YIn, YQp, and YQn. Two paths are available. The first path connects XIp, XQp, YIp, and YQp directly to the IQ modulator, using secondary emission of intrinsic light of different wavelengths to convert to the center wavelength of the FBG-DCM compensation window. After the same steps are performed, the signal is received by the ICR and then converted back to the original wavelength for transmission, achieving superposition of negative dispersion. The second path connects XIp, XQn, YIp, and YQn to the IQ modulator, using secondary emission of intrinsic light of different wavelengths to achieve phase conjugation, converting to the center wavelength of the FBG-DCM compensation window, receiving the signal by the ICR, and then performing the same phase conjugation step to achieve superposition of positive dispersion.

[0027] In this embodiment of the invention, a large dispersion simulator based on photoelectric-optical (OEO) conversion and FBG-DCM cascade is used to achieve polarity-switchable dispersion load by utilizing the complex conjugate control capability of differential driving IQ modulator, while overcoming the inherent narrowband limitation of FBG-DCM.

[0028] The pulse propagation process in optical fiber (including effects such as dispersion, nonlinearity, and attenuation) can be expressed by the Schrödinger equation as follows:

[0029] In the formula It is a slowly varying amplitude. Indicates transmission distance. It's a loss. It is group speed The reciprocal, It is a second-order chromaticity dispersion parameter. It is a nonlinear parameter.

[0030] After complex conjugation, the transport equation is expressed as:

[0031] In the formula, the superscript * is the complex conjugate operator, which indicates the dispersion parameter. It was reversed.

[0032] Input wavelength is The optical signal is demodulated by the ICR, outputting four differential electrical signals. These signals are split into two independent streams for processing:

[0033] 1) Non-conjugate path (Path 1):

[0034] The positive terminal of the in-phase signal output by the ICR ( ) and the positive terminal of the quadrature signal ( Connect to the positive input terminal of the IQ modulator driver. The driving voltage is:

[0035]

[0036]

[0037] IQ modulator at wavelength Under intrinsic light driving, the complex envelope of the output light field is:

[0038]

[0039] in This process achieves wavelength conversion to the complex envelope of the input optical field. .

[0040] 2) Conjugate Path (Path 2):

[0041] The positive terminal of the in-phase signal output by the ICR ( ) and the negative terminal of the quadrature signal ( (Connected to the IQ modulator. Based on the differential relationship) The driving voltage is:

[0042]

[0043]

[0044] The complex envelope of the output light field is:

[0045]

[0046] This path achieves phase conjugation and wavelength conversion. ,and Complex envelope of input light field They form a phase conjugate relationship.

[0047] By precisely controlling the intrinsic light wavelength Both signals are converted to the center wavelength of the compensation window of the FBG-DCM module. ( .

[0048] The wavelength-converted signal is fed into a reconfigurable FBG-DCM module array. Each module contains an FBG-DCM unit and a mechanical-optical switch for switching states. Controlling the dispersion of a single FBG-DCM With the access of [the system], the total system dispersion is:

[0049]

[0050] like Figure 1 As shown, taking N=5 as an example. Figure 2 This is a schematic diagram illustrating a dispersion simulation method based on analog signal processing, as shown in an embodiment of the present invention.

[0051] FBG-DCM introduces a quadratic phase response in the frequency domain, and its time-domain equivalent impulse response is a linear frequency modulation function:

[0052]

[0053] in, The frequency domain representation of the input optical signal. At the speed of light, Angular frequency, The wavelength is specified. After the signal is dispersed by the FBG-DCM module, it enters the secondary OEO conversion stage. This process not only restores the wavelength to the target test frequency band, but also completes the final locking of the dispersion symbol through sophisticated phase control.

[0054] In the non-conjugate path, the optical signal output by FBG-DCM (carrying negative dispersion) The baseband signal is directly demodulated by the ICR, and its baseband signal is at the in-phase positive terminal ( , ) and orthogonal positive ends ( The configuration drives the IQ modulator. At wavelength... Under intrinsic light excitation, the complex envelope of the output light field maintains the original phase relationship. The frequency domain characterization is a typical negative dispersion response, and the total signal transformation of the input optical field is:

[0055]

[0056] in and These represent the complex gain responses of the initial OEO conversion and the second OEO conversion, respectively, including amplitude scaling and linear phase shift; The negative dispersion phase response introduced for the FBG-DCM module, where the dispersion parameter Under ideal distortion-free conditions ( The system degenerates into the standard negative dispersion model:

[0057]

[0058] In the conjugate path, the signal output by the FBG-DCM is first demodulated by the ICR, but the IQ modulator driver uses a quadrature component inverted configuration. , , This differential design achieves quadratic phase conjugation in the time domain. This path achieves operator inversion through a double conjugate architecture:

[0059]

[0060] in and These are the complex gain terms for the initial and second conjugate operations, respectively. The conjugate symmetry is obtained through the Fourier transform. Simplifying, we get the core expression:

[0061]

[0062] The double conjugate operation makes the actual negative dispersive phase response of FBG-DCM Convert to an equivalent positive dispersive response Meanwhile, the gain term retains its product form. .

[0063] Example 2

[0064] The present invention also relates to an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0065] The electronic device can be a desktop computer, laptop, handheld computer, or cloud server, etc. The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The memory can be used to store computer programs and / or modules. The processor performs various functions of the electronic device by running or executing the computer programs and / or modules stored in the memory, and by accessing data stored in the memory.

[0066] Example 3

[0067] The present invention also relates to a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0068] Specifically, the memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital (SD) cards, flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0069] Example 4

[0070] This invention provides a computer program product or computer program that includes computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the steps of the method described in the above embodiments of this invention.

[0071] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "again" in this invention are intended to illustrate the invention and are not intended to limit the invention.

[0072] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A dispersive analog transmission link based on analog signal processing, characterized in that, include: A coherent transmitter, a first coherent receiver chip, a first IQ modulator, a second coherent receiver chip, a second IQ modulator, a Bragg dispersion compensation grating module, and a coherent receiver; The optical signal generated by the coherent transmitter is input to the first coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. These X / Y polarized baseband electrical signal components are divided into non-conjugate and conjugate signals. The non-conjugate signal drives the first IQ modulator, outputting a first non-conjugate optical signal to achieve wavelength conversion. The wavelength of the first non-conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module, while retaining the phase information of the optical signal. The conjugate signal drives the first IQ modulator, outputting a first conjugate optical signal, achieving both wavelength conversion and phase conjugation of the optical signal. The wavelength of the first conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module. The two optical signals are then loaded with the target color by the Bragg dispersion compensation grating module. The first non-conjugate signal, after being loaded with the target dispersion value, is input to the second coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output the second non-conjugate optical signal, achieving wavelength conversion. The wavelength of the second non-conjugate optical signal is converted to the original wavelength, effectively generating a signal with negative dispersion at the original wavelength. The conjugate signal, after being loaded with the target dispersion value, is input to the second coherent receiver chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output the second conjugate optical signal, achieving wavelength conversion while simultaneously achieving phase conjugation of the conjugate signal. The wavelength is converted to the original wavelength, effectively generating a signal with positive dispersion at the original wavelength. The signals with negative dispersion and positive dispersion are received by the coherent receiver.

2. The dispersion analog transmission link as described in claim 1, characterized in that, The Bragg dispersion compensation grating module includes a cascaded Bragg dispersion compensation grating array controlled by a mechanical optical switch. The cascaded Bragg dispersion compensation grating array loads the target dispersion value through a binary combination method, and the total dispersion is... ,in The amount of dispersion for a single Bragg dispersion compensation grating. N represents the switching state of a single mechanical optical switch, and N is the number of Bragg dispersion compensation gratings.

3. A dispersion simulation method for a dispersion simulation transmission link based on analog signal processing as described in claim 1 or 2, characterized in that, Includes the following steps: The original wavelength optical signal is input to the first coherent receiving chip and demodulated into X / Y polarized baseband electrical signal components. The X / Y polarized baseband electrical signal components include non-conjugate signals. The non-conjugate signals drive the first IQ modulator to output a first non-conjugate optical signal, achieving wavelength conversion. The wavelength of the first non-conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module, preserving the phase information of the optical signal. The non-conjugate signal is loaded with a target dispersion value through the Bragg dispersion compensation grating module. The non-conjugate signal after being loaded with the target dispersion value is input to the second coherent receiving chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output a second non-conjugate optical signal, achieving wavelength conversion. The wavelength of the second non-conjugate optical signal is converted to the original wavelength, effectively generating a signal with negative dispersion at the original wavelength.

4. A dispersion simulation method for a dispersion simulation transmission link based on analog signal processing as described in claim 1 or 2, characterized in that, Includes the following steps: The original wavelength optical signal is input to the first coherent receiving chip and demodulated into X / Y polarized baseband electrical signal components. The X / Y polarized baseband electrical signal components include a conjugate signal. The conjugate signal drives the first IQ modulator to output a first conjugate optical signal, achieving wavelength conversion and phase conjugation of the conjugate signal. The wavelength of the first conjugate optical signal is converted to the optimal compensation window wavelength of the Bragg dispersion compensation grating module. The conjugate signal is loaded with a target dispersion value through the Bragg dispersion compensation grating module. The conjugate signal after loading the target dispersion value is input to the second coherent receiving chip and demodulated into X / Y polarized baseband electrical signal components. This drives the second IQ modulator to output a second conjugate optical signal, achieving wavelength conversion and phase conjugation of the conjugate signal. The wavelength of the second conjugate optical signal is converted to the original wavelength, effectively generating a signal with positive dispersion at the original wavelength.

5. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in claim 3 or 4.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method as described in claim 3 or 4.

7. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by the processor, they implement the steps of the method as described in claim 3 or 4.

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