CN114172569B - Optical fiber dispersion coefficient measuring method and device based on coherent optical communication system - Google Patents
Optical fiber dispersion coefficient measuring method and device based on coherent optical communication system Download PDFInfo
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Abstract
The invention discloses a method and a device for measuring an optical fiber dispersion coefficient based on a coherent optical communication system, which relate to the technical field of optical fiber measurement, and the method comprises the steps of acquiring input data of a dispersion compensation module of a DSP unit at an optical fiber receiving end, and caching the acquired input data; adjusting the dispersion coefficient in the dispersion compensation module, inputting the cached input data for calculation to obtain data subjected to frequency domain dispersion compensation, and recovering the data into a time domain signal; extracting data recovered from a data judgment module of a DSP unit at an optical fiber receiving end, and calculating an EVM value of the extracted data; and adjusting the dispersion coefficient again, correspondingly calculating to obtain EVM values, and obtaining EVM values corresponding to different dispersion coefficients, wherein the dispersion coefficient corresponding to the minimum EVM value is the measurement result. The invention can complete the measurement of the dispersion coefficient of the optical fiber in a digital domain without adding special dispersion testing instrument equipment, thereby greatly reducing the measurement cost of the dispersion coefficient of the optical fiber.
Description
Technical Field
The invention relates to the technical field of optical fiber measurement, in particular to an optical fiber dispersion coefficient measuring method and device based on a coherent optical communication system.
Background
The dispersion coefficient of the optical fiber is an important parameter of the optical fiber, including material dispersion and waveguide dispersion, and is used for representing pulse broadening caused by unit spectral width and has a linear relation with the length of the optical fiber. For the measurement of the dispersion coefficient of the optical fiber, the traditional measurement method generally adopts a phase shift method, i.e. optical pulses with different wavelengths are used, the relative group delay is measured, and then the dispersion coefficient of the optical fiber is calculated.
However, the conventional method for measuring the dispersion coefficient of the optical fiber needs to be performed based on a special instrument, thereby causing the cost of measuring the dispersion coefficient of the optical fiber to be too high.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an optical fiber dispersion coefficient measuring method and device based on a coherent optical communication system, which can complete the measurement of the optical fiber dispersion coefficient in a digital domain without adding special dispersion testing instrument equipment, thereby greatly reducing the measurement cost of the optical fiber dispersion coefficient.
In order to achieve the above object, the method for measuring optical fiber dispersion coefficient based on coherent optical communication system provided by the present invention is implemented based on the DSP unit of coherent optical communication system, and specifically includes the following steps:
acquiring input data of a dispersion compensation module of a DSP unit of an optical fiber receiving end, and caching the acquired input data;
adjusting the dispersion coefficient in the dispersion compensation module, inputting the cached input data for calculation to obtain data subjected to frequency domain dispersion compensation, and recovering the data into a time domain signal;
extracting data recovered from a data judgment module of a DSP unit at an optical fiber receiving end, and calculating an EVM value of the extracted data;
and adjusting the dispersion coefficient again, correspondingly calculating to obtain EVM values, and obtaining EVM values corresponding to different dispersion coefficients, wherein the dispersion coefficient corresponding to the minimum EVM value is the measurement result.
On the basis of the above technical solution, the adjusting of the dispersion coefficient in the dispersion compensation module and the inputting of the buffered data for calculation to obtain data after frequency domain dispersion compensation and restoring to time domain signals specifically include:
adjusting the dispersion coefficient in a dispersion compensation module of a DSP unit at an optical fiber receiving end;
acquiring frequency domain data of the cached input data based on FFT, and compensating the optical fiber dispersion in the frequency domain to obtain data subjected to frequency domain dispersion compensation;
and restoring the data subjected to the frequency domain dispersion compensation into a time domain signal based on IFFT, and outputting the time domain signal by the dispersion compensation module.
On the basis of the above technical solution, the FFT-based acquisition of frequency domain data of the cached input data, wherein the calculation formula for acquiring the frequency domain data is:
data FFT ＝FFT(data in )
wherein, the data FFT Representing frequency domain data, FFT representing fast Fourier transform calculation, data in Representing the buffered input data.
On the basis of the technical scheme, the optical fiber dispersion is compensated in the frequency domain to obtain data after frequency domain dispersion compensation, wherein a specific calculation formula for compensation is as follows:
when in use
The method comprises the following steps:
when in use
The method comprises the following steps:
wherein i represents the serial number of the frequency domain data participating in the compensation calculation, the numeric area is 1-N, and the data CD (i) Representing data, after frequency domain dispersion compensation FFT (i) Representing the ith frequency domain data participating in compensation calculation, exp representing an exponential function with a natural constant e as a base, j representing an imaginary unit, pi representing a circumference ratio, C representing a light speed, L representing a fiber length, D representing an adjusted dispersion coefficient, f c Indicating the optical frequency, sa indicates the signal sampling rate of the DSP unit at the fiber receiving end.
On the basis of the above technical solution, the IFFT-based method recovers the data subjected to frequency domain dispersion compensation into a time domain signal, and the specific calculation formula is as follows:
data out ＝IFFT(data CD )
data out representing the time domain signal, i.e. the dispersion compensation module output data, IFFT representing the inverse fast Fourier transform calculation, data CD Representing the frequency domain dispersion compensated data.
On the basis of the technical scheme, the dispersion coefficient is adjusted again, and an EVM value is obtained through corresponding calculation, and the specific steps include:
adjusting the dispersion coefficient again, inputting the cached input data again for calculation to obtain data subjected to frequency domain dispersion compensation, and restoring the data into a time domain signal;
and extracting the data recovered from the data judgment module of the DSP unit at the optical fiber receiving end again, and calculating the EVM value of the extracted data.
On the basis of the above technical solution, the specific calculation formula of calculating the EVM value of the extracted data is:
the EVM represents an EVM value, i represents a serial number of frequency domain data participating in compensation calculation, the numeric area is 1-N, data (i) represents ith data recovered in the data judgment module, and map (i) represents an ideal position of a constellation point corresponding to the ith data recovered in the data judgment module.
On the basis of the technical scheme, the DSP unit of the optical fiber receiving end comprises a clock recovery module, a dispersion compensation module, a channel equalization module, a frequency offset estimation and compensation module, a carrier phase recovery module and a signal judgment module.
On the basis of the technical scheme, the clock recovery module, the dispersion compensation module, the channel equalization module, the frequency offset estimation and compensation module, the carrier phase recovery module and the signal judgment module are sequentially connected and transmit signals in sequence.
The invention provides an optical fiber dispersion coefficient measuring device based on a coherent optical communication system, which is realized based on a DSP unit of the coherent optical communication system and comprises the following components:
the data cache module is used for acquiring input data of the dispersion compensation module of the DSP unit of the optical fiber receiving end and caching the acquired input data;
the dispersion coefficient setting module is used for adjusting the dispersion coefficient in the dispersion compensation module, inputting the cached input data for calculation, obtaining data subjected to frequency domain dispersion compensation, and restoring the data into a time domain signal;
and the EVM calculation module is used for extracting the data recovered from the data judgment module of the DSP unit of the optical fiber receiving end, calculating the EVM value of the extracted data, driving the dispersion coefficient setting module to work again, adjusting the dispersion coefficient again, inputting the cached input data again for calculation to obtain data subjected to frequency domain dispersion compensation, restoring the data into a time domain signal, extracting the data recovered from the data judgment module of the DSP unit of the optical fiber receiving end again, calculating the EVM value of the extracted data to obtain EVM values corresponding to different dispersion coefficients, and obtaining the dispersion coefficient corresponding to the minimum EVM value as a measurement result.
Compared with the prior art, the invention has the advantages that: the input data of a dispersion compensation module of an optical fiber receiving end DSP unit is obtained, the obtained input data is cached, then the dispersion coefficient in the dispersion compensation module is adjusted, the cached input data is input for calculation, the data subjected to frequency domain dispersion compensation is obtained and is restored into a time domain signal, then the data restored in a data judgment module of the optical fiber receiving end DSP unit is extracted, the EVM value of the extracted data is calculated, then the dispersion coefficient is adjusted again, the EVM value is obtained through corresponding calculation, the EVM values corresponding to different dispersion coefficients are obtained, the dispersion coefficient corresponding to the minimum EVM value is the measurement result, special dispersion testing instrument equipment does not need to be added, the measurement of the optical fiber dispersion coefficient can be completed in a digital domain, and the measurement cost of the optical fiber dispersion coefficient is greatly reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flowchart of a method for measuring dispersion coefficient of an optical fiber based on a coherent optical communication system according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an optical fiber dispersion coefficient measuring device based on a coherent optical communication system in an embodiment of the present invention.
Detailed Description
The embodiment of the invention provides an optical fiber dispersion coefficient measuring method based on a coherent optical communication system, which comprises the steps of obtaining input data of a dispersion compensation module of a DSP unit of an optical fiber receiving end, caching the obtained input data, adjusting a dispersion coefficient in the dispersion compensation module, inputting the cached input data for calculation, obtaining data subjected to frequency domain dispersion compensation, restoring the data into a time domain signal, extracting data restored in a data judgment module of the DSP unit of the optical fiber receiving end, calculating an EVM (error vector magnitude) value of the extracted data, adjusting the dispersion coefficient again, obtaining the EVM value through corresponding calculation, obtaining the EVM values corresponding to different dispersion coefficients, and enabling the dispersion coefficient corresponding to the minimum EVM value to be a measuring result. The embodiment of the invention correspondingly provides an optical fiber dispersion coefficient measuring device based on the coherent optical communication system.
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments.
Referring to fig. 1, the method for measuring an optical fiber dispersion coefficient based on a coherent optical communication system according to an embodiment of the present invention is implemented based on a Digital Signal Processing (DSP) unit of the coherent optical communication system, and thanks to rapid development of the DSP technology, influences of an optical fiber transmission link and a transceiver end optoelectronic device on signals can be compensated in the DSP unit of an optical fiber receiving end. The DSP unit of the optical fiber receiving end comprises a clock recovery module, a dispersion compensation module, a channel equalization module, a frequency offset estimation and compensation module, a carrier phase recovery module and a signal judgment module. The clock recovery module, the dispersion compensation module, the channel equalization module, the frequency offset estimation and compensation module, the carrier phase recovery module and the signal judgment module are sequentially connected and transmit signals in sequence.
The method for measuring the dispersion coefficient of the optical fiber comprises the following steps:
s1: acquiring input data of a dispersion compensation module of a DSP unit at an optical fiber receiving end, and caching the acquired input data; the input data of the dispersion compensation module is cached, so that the consistency of the data is ensured, and the subsequent processing steps are calculated based on the same input data.
S2: adjusting a dispersion coefficient in a dispersion compensation module, inputting the cached input data for calculation to obtain data subjected to frequency domain dispersion compensation, and restoring the data into a time domain signal; and after the data subjected to the frequency domain dispersion compensation is restored into a time domain signal, the time domain signal is continuously output by the dispersion compensation module and is received and processed by a subsequent module of the DSP unit of the optical fiber receiving end.
S3: extracting data recovered from a data judgment module of a DSP unit at an optical fiber receiving end, and calculating an EVM (Error Vector Magnitude) value of the extracted data;
s4: and adjusting the dispersion coefficient again, correspondingly calculating to obtain EVM values, and obtaining EVM values corresponding to different dispersion coefficients, wherein the dispersion coefficient corresponding to the minimum EVM value is the measurement result. Namely, after the dispersion coefficient is adjusted again, repeating the steps S2 and S3, correspondingly calculating again to obtain one EVM value, sequentially circulating for many times, and obtaining a plurality of EVM values, wherein each EVM value corresponds to one adjusted dispersion coefficient, and for the obtained plurality of EVM values, the dispersion coefficient corresponding to the minimum EVM value is the measurement result, that is, the measured optical fiber dispersion coefficient.
In the process of measuring the dispersion coefficient, the invention carries out dispersion compensation on the received data of the dispersion compensation module by using different dispersion coefficients, compares the EVM values of the data obtained by DSP processing under different conditions, and the corresponding dispersion coefficient under the condition of the minimum EVM value is the dispersion coefficient of the current optical fiber link.
When the value of the dispersion coefficient is adjusted, the scanning range can be reduced according to actual conditions. For example, when the measuring fiber is a g.652 fiber and the wavelength of the optical signal is in the C band, the range of the dispersion coefficient should be set to be around 20 ps/(nm · km) to reduce the amount of calculation.
In the embodiment of the present invention, the dispersion coefficient in the dispersion compensation module is adjusted, and the buffered data is input for calculation to obtain data after frequency domain dispersion compensation, and the data is restored to a time domain signal, and the specific steps include:
s201: adjusting the dispersion coefficient in a dispersion compensation module of a DSP unit at an optical fiber receiving end;
s202: acquiring frequency domain data of the cached input data based on Fast Fourier Transform (FFT), and compensating fiber dispersion in a frequency domain to obtain data subjected to frequency domain dispersion compensation;
in the embodiment of the present invention, the frequency domain data of the cached input data is obtained based on the FFT, wherein a calculation formula for obtaining the frequency domain data is:
data FFT ＝FFT(data in )
wherein, the data FFT Representing frequency domain data, FFT representing fast Fourier transform calculation, data in Representing the buffered input data.
In the embodiment of the invention, the optical fiber dispersion is compensated in the frequency domain to obtain data after the frequency domain dispersion compensation, wherein the specific calculation formula for the compensation is as follows:
when in use
The method comprises the following steps:
when in use
The method comprises the following steps:
wherein i represents the serial number of the frequency domain data participating in the compensation calculation, the numeric area is 1-N, and the data CD (i) Representing data, after frequency domain dispersion compensation FFT (i) Representing the ith frequency domain data participating in compensation calculation, exp representing an exponential function with a natural constant e as a base, j representing an imaginary unit, pi representing a circumference ratio, C representing a light speed, L representing a fiber length, D representing an adjusted dispersion coefficient, f c Indicating the optical frequency, sa indicates the signal sampling rate of the DSP unit at the fiber receiving end.
S203: the data after frequency domain dispersion compensation is restored to a time domain signal based on IFFT (Inverse Fast Fourier transform), and is output by the dispersion compensation module.
In the embodiment of the present invention, the data after frequency domain dispersion compensation is restored to a time domain signal based on IFFT, and the specific calculation formula is:
data out ＝IFFT(data CD )
data out representing the time domain signal, i.e. the dispersion compensation module output data, IFFT representing the inverse fast Fourier transform calculation, data CD Representing the frequency domain dispersion compensated data.
In the embodiment of the invention, the dispersion coefficient is adjusted again, and the EVM value is obtained through corresponding calculation, and the specific steps comprise:
s401: adjusting the dispersion coefficient again, inputting the cached input data again for calculation to obtain data subjected to frequency domain dispersion compensation, and restoring the data into a time domain signal;
s402: and extracting the data recovered from the data judgment module of the DSP unit at the optical fiber receiving end again, and calculating the EVM value of the extracted data.
In the embodiment of the invention, the EVM value of the extracted data is calculated, and the specific calculation formula is as follows:
the EVM represents an EVM value, i represents a serial number of frequency domain data participating in compensation calculation, the numeric area is 1-N, data (i) represents ith data recovered in the data judgment module, and map (i) represents an ideal position of a constellation point corresponding to the ith data recovered in the data judgment module. Here, a simplified EVM result is calculated, and no normalization process is performed to reflect the deviation of the demodulated actual data from the ideal data on the constellation diagram.
The method for measuring the dispersion coefficient of the optical fiber comprises the steps of obtaining input data of a dispersion compensation module of a DSP unit of an optical fiber receiving end, caching the obtained input data, adjusting the dispersion coefficient in the dispersion compensation module, inputting the cached input data, calculating to obtain data subjected to frequency domain dispersion compensation, restoring the data into a time domain signal, extracting data restored in a data judgment module of the DSP unit of the optical fiber receiving end, calculating an EVM value of the extracted data, adjusting the dispersion coefficient again, calculating to obtain the EVM value correspondingly, and obtaining the EVM value corresponding to different dispersion coefficients, wherein the dispersion coefficient corresponding to the minimum EVM value is a measurement result, special dispersion testing instrument equipment does not need to be added, the measurement of the dispersion coefficient of the optical fiber can be completed in a digital domain, and the measurement cost of the dispersion coefficient of the optical fiber is greatly reduced.
In a possible implementation manner, an embodiment of the present invention further provides a readable storage medium, where the readable storage medium is located in the PLC controller, and the readable storage medium stores a computer program, where the computer program, when executed by a processor, implements the following steps of the method for measuring optical fiber dispersion coefficient based on a coherent optical communication system:
acquiring input data of a dispersion compensation module of a DSP unit at an optical fiber receiving end, and caching the acquired input data;
adjusting the dispersion coefficient in the dispersion compensation module, inputting the cached input data for calculation to obtain data subjected to frequency domain dispersion compensation, and recovering the data into a time domain signal;
extracting data recovered from a data judgment module of a DSP unit at an optical fiber receiving end, and calculating an EVM value of the extracted data;
and adjusting the dispersion coefficient again, correspondingly calculating to obtain EVM values, and obtaining EVM values corresponding to different dispersion coefficients, wherein the dispersion coefficient corresponding to the minimum EVM value is the measurement result.
The storage medium may take any combination of one or more computer-readable media. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer-readable storage medium may be, for example but not limited to: an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.
A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated data signal may take many forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wire, fiber optic cable, RF, etc., or any suitable combination of the foregoing.
Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, smalltalk, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider).
Referring to fig. 2, an optical fiber dispersion coefficient measurement device based on a coherent optical communication system according to an embodiment of the present invention includes a data caching module, a dispersion coefficient setting module, and an EVM calculation module. In fig. 2, the dotted line is a DSP unit at the optical fiber receiving end of the existing coherent optical communication system, and the implementation part is a data processing part for performing optical fiber dispersion coefficient measurement added in the embodiment of the present invention. Before the dispersion coefficient measurement is carried out, the wavelength or frequency of the optical signal and the length of the optical fiber are known quantities, and if the quantity is unknown, the measurement is carried out through corresponding equipment.
The data cache module is used for acquiring input data of a dispersion compensation module of the DSP unit of the optical fiber receiving end and caching the acquired input data; the dispersion coefficient setting module is used for adjusting the dispersion coefficient in the dispersion compensation module, inputting the cached input data for calculation, obtaining data subjected to frequency domain dispersion compensation, and recovering the data into a time domain signal; the EVM calculation module is used for extracting data recovered from the data judgment module of the DSP unit of the optical fiber receiving end, calculating an EVM value of the extracted data, driving the dispersion coefficient setting module to work again, adjusting the dispersion coefficient again, inputting the cached input data again for calculation to obtain data subjected to frequency domain dispersion compensation, recovering the data into a time domain signal, extracting the data recovered from the data judgment module of the DSP unit of the optical fiber receiving end again, calculating the EVM value of the extracted data to obtain EVM values corresponding to different dispersion coefficients, and obtaining the dispersion coefficient corresponding to the minimum EVM value as a measurement result.
The device for measuring the dispersion coefficient of the optical fiber obtains the input data of the dispersion compensation module of the DSP unit of the optical fiber receiving end, caches the obtained input data, adjusts the dispersion coefficient in the dispersion compensation module, inputs the cached input data for calculation to obtain data subjected to frequency domain dispersion compensation, restores the data into time domain signals, extracts the data restored in the data judgment module of the DSP unit of the optical fiber receiving end, calculates the EVM value of the extracted data, adjusts the dispersion coefficient again, correspondingly calculates the EVM value to obtain the EVM values corresponding to different dispersion coefficients, obtains the dispersion coefficient corresponding to the minimum EVM value as a measurement result, can complete the measurement of the dispersion coefficient of the optical fiber in a digital domain without adding special dispersion test instrument equipment, and greatly reduces the measurement cost of the dispersion coefficient of the optical fiber.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Claims (8)
1. An optical fiber dispersion coefficient measuring method based on a coherent optical communication system is realized based on a DSP unit of the coherent optical communication system, and is characterized by comprising the following steps:
acquiring input data of a dispersion compensation module of a DSP unit of an optical fiber receiving end, and caching the acquired input data;
adjusting the dispersion coefficient in the dispersion compensation module, inputting the cached input data for calculation to obtain data subjected to frequency domain dispersion compensation, and recovering the data into a time domain signal;
extracting data recovered from a data judgment module of a DSP unit at an optical fiber receiving end, and calculating an Error Vector Magnitude (EVM) value of the extracted data;
adjusting the dispersion coefficient again, correspondingly calculating to obtain EVM values, and obtaining EVM values corresponding to different dispersion coefficients, wherein the dispersion coefficient corresponding to the minimum EVM value is the measurement result;
the method comprises the following steps of adjusting dispersion coefficients in a dispersion compensation module, inputting cached data for calculation, obtaining data subjected to frequency domain dispersion compensation, and restoring the data into time domain signals, wherein the method comprises the following specific steps:
adjusting the dispersion coefficient in a dispersion compensation module of a DSP unit at an optical fiber receiving end;
acquiring frequency domain data of the cached input data based on FFT, and compensating the optical fiber dispersion in the frequency domain to obtain data subjected to frequency domain dispersion compensation;
restoring the data subjected to frequency domain dispersion compensation into a time domain signal based on IFFT, and outputting the time domain signal by a dispersion compensation module;
the optical fiber dispersion is compensated in the frequency domain to obtain data after frequency domain dispersion compensation, wherein the specific calculation formula for compensation is as follows:
when the temperature is higher than the set temperature
The method comprises the following steps:
when in use
The method comprises the following steps:
wherein i represents the serial number of the frequency domain data participating in the compensation calculation, the numeric area is 1-N, and the data CD (i) Representing data, after frequency domain dispersion compensation FFT (i) Representing the ith frequency domain data participating in compensation calculation, exp representing an exponential function with a natural constant e as a base, j representing an imaginary unit, pi representing a circumference ratio, C representing a light speed, L representing a fiber length, D representing an adjusted dispersion coefficient, f c Indicating the optical frequency, and Sa indicating the signal sampling rate of the DSP unit at the optical fiber receiving end.
2. The method according to claim 1, wherein the FFT-based acquisition of the frequency domain data of the buffered input data is performed by the following calculation formula:
data FFT ＝FFT(data in )
wherein, the data FFT Representing frequency domain data, FFT representing fast Fourier transform calculation, data in Representing the buffered input data.
3. The method according to claim 1, wherein the IFFT-based method for recovering the frequency-domain dispersion compensated data into the time-domain signal comprises the following specific calculation formula:
data out ＝IFFT(data CD )
data out representing the time domain signal, i.e. the dispersion compensation module output data, IFFT representing the inverse fast Fourier transform calculation, data CD Representing the frequency domain dispersion compensated data.
4. The method according to claim 1, wherein the dispersion coefficient is readjusted and the EVM value is obtained by corresponding calculation, and the method comprises the following steps:
adjusting the dispersion coefficient again, inputting the cached input data again for calculation to obtain data subjected to frequency domain dispersion compensation, and restoring the data into a time domain signal;
and extracting the data recovered from the data judgment module of the DSP unit at the optical fiber receiving end again, and calculating the EVM value of the extracted data.
5. The method according to claim 1, wherein the EVM value of the extracted data is calculated by using a specific calculation formula as follows:
the EVM represents an EVM value, i represents a serial number of frequency domain data participating in compensation calculation, the numeric area is 1-N, data (i) represents ith data recovered in the data judgment module, and map (i) represents an ideal position of a constellation point corresponding to the ith data recovered in the data judgment module.
6. The method of claim 1, wherein the method comprises: the DSP unit of the optical fiber receiving end comprises a clock recovery module, a dispersion compensation module, a channel equalization module, a frequency offset estimation and compensation module, a carrier phase recovery module and a signal judgment module.
7. The method of claim 6, wherein the method comprises: the clock recovery module, the dispersion compensation module, the channel equalization module, the frequency offset estimation and compensation module, the carrier phase recovery module and the signal judgment module are sequentially connected and transmit signals in sequence.
8. An optical fiber dispersion coefficient measuring device based on a coherent optical communication system is realized based on a DSP unit of the coherent optical communication system, and is characterized by comprising the following components:
the data cache module is used for acquiring input data of the dispersion compensation module of the DSP unit of the optical fiber receiving end and caching the acquired input data;
the dispersion coefficient setting module is used for adjusting the dispersion coefficient in the dispersion compensation module, inputting the cached input data for calculation, obtaining data subjected to frequency domain dispersion compensation, and restoring the data into a time domain signal;
the EVM calculation module is used for extracting data recovered from the data judgment module of the DSP unit of the optical fiber receiving end, calculating an error vector amplitude EVM value of the extracted data, driving the dispersion coefficient setting module to work again, inputting the cached input data again for calculation after the dispersion coefficient is adjusted again, obtaining data subjected to frequency domain dispersion compensation, recovering the data into a time domain signal, then extracting the data recovered from the data judgment module of the DSP unit of the optical fiber receiving end again, calculating the EVM value of the extracted data, obtaining EVM values corresponding to different dispersion coefficients, and obtaining the dispersion coefficient corresponding to the minimum EVM value as a measurement result;
the method comprises the following steps of adjusting dispersion coefficients in a dispersion compensation module, inputting cached data for calculation, obtaining data subjected to frequency domain dispersion compensation, and restoring the data into time domain signals, wherein the method comprises the following specific steps:
adjusting the dispersion coefficient in a dispersion compensation module of a DSP unit at an optical fiber receiving end;
acquiring frequency domain data of the cached input data based on FFT, and compensating the optical fiber dispersion in the frequency domain to obtain data subjected to frequency domain dispersion compensation;
restoring the data subjected to frequency domain dispersion compensation into a time domain signal based on IFFT, and outputting the time domain signal by a dispersion compensation module;
the optical fiber dispersion is compensated in the frequency domain to obtain data after frequency domain dispersion compensation, wherein a specific calculation formula for compensation is as follows:
when in use
The method comprises the following steps:
when the temperature is higher than the set temperature
The method comprises the following steps:
wherein i represents the serial number of the frequency domain data participating in the compensation calculation, the numeric area is 1-N, and the data CD (i) Representing data, after frequency domain dispersion compensation FFT (i) Representing the ith frequency domain data participating in compensation calculation, exp representing an exponential function with a natural constant e as a base, j representing an imaginary unit, pi representing a circumference ratio, C representing a light speed, L representing a fiber length, D representing an adjusted dispersion coefficient, f c Indicating the optical frequency, sa indicates the signal sampling rate of the DSP unit at the fiber receiving end.
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| US9628180B2 (en) * | 2014-03-31 | 2017-04-18 | Infinera Corporation | Configurable frequency domain equalizer for dispersion compensation of multiple sub-carriers |
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