CN114584434B - Filter coefficient calculation method and optical module - Google Patents
Filter coefficient calculation method and optical module Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03828—Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties
- H04L25/03834—Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties using pulse shaping
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
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Abstract
The application provides a calculation method of a filter coefficient and an optical module, wherein the filter coefficient is used for an oDSP chip in a coherent optical module, and the method comprises the following steps: acquiring an original spectrogram; setting an ideal spectrogram Sideal based on a Nyquist filter; resampling an original spectrogram and carrying out normalization processing on the amplitude and the frequency interval by referring to the resolution and the amplitude of the ideal spectrogram Sideal to obtain a spectrum measurement function Smeasure; calculating to obtain a compensation filter transfer function Scomp according to the compensation filter transfer function scomp=ideal/Smeasure; the filter coefficients are obtained from a back-reconstruction of the compensation filter transfer function Scomp. The calculation method of the filter coefficient and the optical module provided by the application enable the filter supplementing method of the oDSP chip to be simple and fast, and ensure that the filter in the oDSP chip has good high-frequency bandwidth compensation effect.
Description
Technical Field
The present disclosure relates to the field of optical communications technologies, and in particular, to a method for calculating a filter coefficient and an optical module.
Background
With the development of new business and application modes such as cloud computing, mobile internet, video and the like, the development and progress of optical communication technology become more and more important. In the optical communication technology, the optical module is a tool for realizing the mutual conversion of optical signals, is one of key devices in optical communication equipment, and the transmission rate of the optical module is continuously improved along with the development of the optical communication technology.
In the development process of the coherent optical module, the error rate of the optical module before correction cannot be optimized due to insufficient bandwidths of the laser driver and the modulator and high-frequency damage caused by wiring on a circuit board in the connection process of the module.
Disclosure of Invention
The application provides a calculation method of a filter coefficient and an optical module, which are used for enabling the error rate of the optical module to be optimal before correction.
In a first aspect, the present application provides a method for calculating a filter coefficient, where the method includes:
acquiring an original spectrogram;
setting an ideal spectrogram Sideal based on a Nyquist filter;
resampling an original spectrogram and carrying out normalization processing on the amplitude and the frequency interval by referring to the resolution and the amplitude of the ideal spectrogram Sideal to obtain a spectrum measurement function Smeasure;
calculating to obtain a compensation filter transfer function Scomp according to the compensation filter transfer function scomp=ideal/Smeasure;
the filter coefficients are obtained from a back-reconstruction of the compensation filter transfer function Scomp.
In a second aspect, the present application provides an optical module, including:
a circuit board;
the light emitting assembly is electrically connected with the circuit board and is used for emitting light signals;
the circuit board is provided with an oDSP chip, the oDSP chip is electrically connected with the light emitting component, the oDSP chip comprises a filter, the filter is used for preprocessing an electric signal transmitted to the light emitting component, and coefficients of the filter are coefficients calculated according to the method of the first aspect.
According to the filter coefficient calculating method and the optical module, an ideal spectrogram Sideal is set by using a Nyquist filter, the original spectrogram is resampled and normalized in amplitude and frequency interval is carried out according to the resolution and amplitude of the ideal spectrogram Sideal, a spectrum measuring function Smeasure is obtained, a compensation filter transfer function Scomp is obtained through calculation according to a compensation filter transfer function Scomp=Sideal/Smeasure, and a filter coefficient is obtained through inverse reconstruction according to the compensation filter transfer function Scomp. The filter coefficient obtained by the filter coefficient calculation method provided by the application ensures that the filter compensation method of the oDSP chip is simple and fast, and ensures that the filter in the oDSP chip has good electric signal precompensation effect so as to achieve the effect of compensating the high frequency bandwidth of the optical module and ensure that the error rate of the optical module before correction is smaller than or equal to the target error rate. Therefore, the filter coefficient calculating method and the optical module solve the problems that the bandwidth of a laser driver and a modulator is insufficient, the optical module is led into high-frequency damage in the wiring of a circuit board in the connection process, and the error rate of the optical module before correction cannot reach the best.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a connection diagram of an optical communication system according to some embodiments;
fig. 2 is a block diagram of an optical network terminal according to some embodiments;
FIG. 3 is a block diagram of an optical module according to some embodiments;
fig. 4 is an exploded view of a light module according to some embodiments;
FIG. 5 is a flow chart of a method of calculating filter coefficients according to some embodiments;
FIG. 6 is an original spectrum diagram of a coherent optical module according to some embodiments;
FIG. 7 is a schematic diagram of a structure for shifting the abscissa of the spectrum center of an original spectrogram to 0 according to some embodiments;
FIG. 8 is an idealized spectrogram provided in accordance with some embodiments;
FIG. 9 is a schematic diagram of a compensation filter transfer function according to an embodiment of the present application;
fig. 10 is a spectrum diagram after spectrum compensation according to some embodiments.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
Throughout the specification and claims, unless the context requires otherwise, the word "comprise" and its other forms such as the third person referring to the singular form "comprise" and the present word "comprising" are to be construed as open, inclusive meaning, i.e. as "comprising, but not limited to. In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", "some examples", "and the like are intended to indicate that a particular feature, structure, material, or characteristic associated with the embodiment or example is included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
The terms "first" and "second" are used below for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present disclosure, unless otherwise indicated, the meaning of "a plurality" is two or more.
In describing some embodiments, expressions of "coupled" and "connected" and their derivatives may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more elements are in direct physical or electrical contact with each other. As another example, the term "coupled" may be used in describing some embodiments to indicate that two or more elements are in direct physical or electrical contact. However, the term "coupled" or "communicatively coupled (communicatively coupled)" may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments disclosed herein are not necessarily limited to the disclosure herein.
At least one of "A, B and C" has the same meaning as at least one of "A, B or C," both include the following combinations of A, B and C: a alone, B alone, C alone, a combination of a and B, a combination of a and C, a combination of B and C, and a combination of A, B and C.
"A and/or B" includes the following three combinations: only a, only B, and combinations of a and B.
The use of "adapted" or "configured to" herein is meant to be an open and inclusive language that does not exclude devices adapted or configured to perform additional tasks or steps.
As used herein, "about," "approximately" or "approximately" includes the stated values as well as average values within an acceptable deviation range of the particular values as determined by one of ordinary skill in the art in view of the measurement in question and the errors associated with the measurement of the particular quantity (i.e., limitations of the measurement system).
In the optical communication technology, light is used to carry information to be transmitted, and an optical signal carrying the information is transmitted to an information processing device such as a computer through an information transmission device such as an optical fiber or an optical waveguide, so as to complete the transmission of the information. Since the optical signal has a passive transmission characteristic when transmitted through an optical fiber or an optical waveguide, low-cost and low-loss information transmission can be realized. Further, since a signal transmitted by an information transmission device such as an optical fiber or an optical waveguide is an optical signal and a signal that can be recognized and processed by an information processing device such as a computer is an electrical signal, it is necessary to perform mutual conversion between the electrical signal and the optical signal in order to establish an information connection between the information transmission device such as an optical fiber or an optical waveguide and the information processing device such as a computer.
The optical module realizes the function of interconversion between the optical signal and the electric signal in the technical field of optical fiber communication. The optical module comprises an optical port and an electric port, the optical module realizes optical communication with information transmission equipment such as optical fibers or optical waveguides through the optical port, realizes electric connection with an optical network terminal (for example, optical cat) through the electric port, and is mainly used for realizing power supply, I2C signal transmission, data signal transmission, grounding and the like; the optical network terminal transmits the electric signal to information processing equipment such as a computer through a network cable or wireless fidelity (Wi-Fi).
Fig. 1 is a connection diagram of an optical communication system according to some embodiments. As shown in fig. 1, the optical communication system mainly includes a remote server 1000, a local information processing device 2000, an optical network terminal 100, an optical module 200, an optical fiber 101, and a network cable 103;
one end of the optical fiber 101 is connected to the remote server 1000, and the other end is connected to the optical network terminal 100 through the optical module 200. The optical fiber itself can support long-distance signal transmission, such as signal transmission of several kilometers (6-8 kilometers), on the basis of which, if a repeater is used, it is theoretically possible to realize ultra-long-distance transmission. Thus, in a typical optical communication system, the distance between the remote server 1000 and the optical network terminal 100 may typically reach several kilometers, tens of kilometers, or hundreds of kilometers.
One end of the network cable 103 is connected to the local information processing device 2000, and the other end is connected to the optical network terminal 100. The local information processing apparatus 2000 may be any one or several of the following: routers, switches, computers, cell phones, tablet computers, televisions, etc.
The physical distance between the remote server 1000 and the optical network terminal 100 is greater than the physical distance between the local information processing apparatus 2000 and the optical network terminal 100. The connection between the local information processing device 2000 and the remote server 1000 is completed by an optical fiber 101 and a network cable 103; and the connection between the optical fiber 101 and the network cable 103 is made by the optical module 200 and the optical network terminal 100.
The optical module 200 includes an optical port and an electrical port. The optical port is configured to connect with the optical fiber 101 such that the optical module 200 establishes a bi-directional optical signal connection with the optical fiber 101; the electrical port is configured to be accessed into the optical network terminal 100 such that the optical module 200 establishes a bi-directional electrical signal connection with the optical network terminal 100. The optical module 200 performs mutual conversion between optical signals and electrical signals, so that a connection is established between the optical fiber 101 and the optical network terminal 100. For example, an optical signal from the optical fiber 101 is converted into an electrical signal by the optical module 200 and then input to the optical network terminal 100, and an electrical signal from the optical network terminal 100 is converted into an optical signal by the optical module 200 and input to the optical fiber 101.
The optical network terminal 100 includes a substantially rectangular parallelepiped housing (housing), and an optical module interface 102 and a network cable interface 104 provided on the housing. The optical module interface 102 is configured to access the optical module 200, so that the optical network terminal 100 and the optical module 200 establish a bidirectional electrical signal connection; the network cable interface 104 is configured to access the network cable 103 such that the optical network terminal 100 establishes a bi-directional electrical signal connection with the network cable 103. A connection is established between the optical module 200 and the network cable 103 through the optical network terminal 100. By way of example, since the optical network terminal 100 transmits an electrical signal from the optical module 200 to the network cable 103 and transmits a signal from the network cable 103 to the optical module 200, the optical network terminal 100 can monitor the operation of the optical module 200 as a host computer of the optical module 200. The upper computer of the optical module 200 may include an optical line terminal (Optical Line Terminal, OLT) or the like in addition to the optical network terminal 100.
The remote server 1000 establishes a bidirectional signal transmission channel with the local information processing device 2000 through the optical fiber 101, the optical module 200, the optical network terminal 100 and the network cable 103.
Fig. 2 is a block diagram of an optical network terminal according to some embodiments, and fig. 2 only shows a structure of the optical network terminal 100 related to the optical module 200 in order to clearly show a connection relationship between the optical module 200 and the optical network terminal 100. As shown in fig. 2, the optical network terminal 100 further includes a PCB circuit board 105 disposed in the housing, a cage 106 disposed on a surface of the PCB circuit board 105, and an electrical connector disposed inside the cage 106. The electrical connector is configured to access an electrical port of the optical module 200; the heat sink 107 has a convex portion such as a fin that increases the heat dissipation area.
The optical module 200 is inserted into the cage 106 of the optical network terminal 100, the optical module 200 is fixed by the cage 106, and heat generated by the optical module 200 is transferred to the cage 106 and then diffused through the heat sink 107. After the optical module 200 is inserted into the cage 106, the electrical port of the optical module 200 is connected with an electrical connector inside the cage 106, so that the optical module 200 establishes a bi-directional electrical signal connection with the optical network terminal 100. In addition, the optical port of the optical module 200 is connected to the optical fiber 101, so that the optical module 200 establishes a bi-directional electrical signal connection with the optical fiber 101.
Fig. 3 is a diagram of an optical module structure provided in accordance with some embodiments, and fig. 4 is an exploded diagram of an optical module provided in accordance with some embodiments. As shown in fig. 3 and 4, the optical module 200 includes a housing, a circuit board disposed in the housing, and an optical transceiver assembly.
The housing comprises an upper housing 201 and a lower housing 202, the upper housing 201 covering the lower housing 202 to form a wrapped cavity having two openings 204 and 205; the outer contour of the housing generally presents a square shape.
In some embodiments of the present disclosure, the lower housing 202 includes a bottom plate and two lower side plates disposed at both sides of the bottom plate and perpendicular to the bottom plate; the upper case 201 includes a cover plate, and two upper side plates disposed at two sides of the cover plate and perpendicular to the cover plate, and two side walls are combined with the two side plates to realize that the upper case 201 is covered on the lower case 202.
The direction of the connection line of the two openings 204 and 205 may be identical to the length direction of the optical module 200 or not identical to the length direction of the optical module 200. Illustratively, opening 204 is located at the end of light module 200 (left end of fig. 3) and opening 205 is also located at the end of light module 200 (right end of fig. 3). Alternatively, the opening 204 is located at the end of the light module 200, while the opening 205 is located at the side of the light module 200. The opening 204 is an electrical port, and the golden finger of the circuit board 300 extends out of the electrical port 204 and is inserted into an upper computer (such as the optical network terminal 100); the opening 205 is an optical port configured to be connected to the external optical fiber 101, so that the optical fiber 101 is connected to an optical transceiver module inside the optical module 200.
By adopting the assembly mode of combining the upper shell 201 and the lower shell 202, devices such as the circuit board 300, the optical transceiver component and the like are conveniently installed in the shell, and the upper shell 201 and the lower shell 202 can form packaging protection for the devices. In addition, when devices such as the circuit board 300 are assembled, the positioning component, the heat dissipation component and the electromagnetic shielding component of the devices are conveniently arranged, and the automatic implementation and production are facilitated.
In some embodiments, the upper housing 201 and the lower housing 202 are generally made of metal materials, which is beneficial to electromagnetic shielding and heat dissipation.
In some embodiments, the optical module 200 further includes an unlocking member 203 located on an outer wall of the housing, and the unlocking member 203 is configured to achieve a fixed connection between the optical module 200 and the host computer, or release the fixed connection between the optical module 200 and the host computer.
Illustratively, the unlocking member 203 is located on the outer walls of the two lower side plates 2022 of the lower housing 202, and includes an engagement member that mates with a cage of an upper computer (e.g., the cage 106 of the optical network terminal 100). When the optical module 200 is inserted into the cage of the upper computer, the optical module 200 is fixed in the cage of the upper computer by the clamping component of the unlocking component 203; when the unlocking member 203 is pulled, the engaging member of the unlocking member 203 moves along with the unlocking member, so as to change the connection relationship between the engaging member and the host computer, so as to release the engagement relationship between the optical module 200 and the host computer, and thus the optical module 200 can be pulled out from the cage of the host computer.
The circuit board 300 includes circuit traces, electronic components and chips, which are connected together by the circuit traces according to a circuit design to realize functions such as power supply, electrical signal transmission, and grounding. The electronic components may include, for example, capacitors, resistors, transistors, metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). The chips may include, for example, a micro control unit (Microcontroller Unit, MCU), limiting amplifier (limiting amplifier), clock data recovery chip (Clock and Data Recovery, CDR), power management chip, digital signal processing (Digital Signal Processing, DSP) chip.
The circuit board 300 is generally a hard circuit board, and the hard circuit board can also realize a bearing function due to the relatively hard material, for example, the hard circuit board can stably bear chips; the hard circuit board can also be inserted into an electrical connector in the upper computer cage.
The circuit board 300 further includes a gold finger 301 formed on an end surface thereof, the gold finger 301 being composed of a plurality of pins independent of each other. The circuit board 300 is inserted into the cage 106 and is conductively connected to the electrical connectors within the cage 106 by the gold fingers 301. The golden finger 301 may be disposed on only one surface (such as the upper surface shown in fig. 4) of the circuit board 300, or may be disposed on both upper and lower surfaces of the circuit board 300, so as to adapt to the situation where the pin number is large. The golden finger 301 is configured to establish electrical connection with an upper computer to achieve power supply, grounding, I2C signal transfer, data signal transfer, and the like. Of course, flexible circuit boards may also be used in some optical modules. The flexible circuit board is generally used in cooperation with the rigid circuit board to supplement the rigid circuit board.
In some embodiments of the present application, the optical transceiver includes an optical transmitting component and an optical receiving component. As shown in fig. 4, in some embodiments, the optical transceiver component includes an optical transmitter component 206 and an optical receiver component 207; the light emitting element 206 and the light receiving element 207 are located at the edge of the circuit board 300. The optical sub-module shown in fig. 3 and 4 is only an example of the present application, and the optical transceiver component in the embodiments of the present application may be a transceiver structure. Optionally, an optical transceiver is located at an end of the circuit board 300, and an optical transceiver module is physically separated from the circuit board 300, and the optical transceiver module is connected to the circuit board 300 through a flexible circuit board.
In some embodiments of the present application, an oDSP chip 301 is disposed on a circuit board 300, the oDSP chip 301 is electrically connected to an optical emission component 206, the oDSP chip 301 includes a filter, a signal that needs to be emitted through electro-optical conversion by the optical emission component 206 may be pre-compensated by the filter in the oDSP chip 301, so as to solve the problem that the error rate of an optical module before correction reaches the best because the bandwidth of a laser driver and a modulator is insufficient and high-frequency damage is led in by wiring on the circuit board. To ensure that the filter in the oDSP chip 301 has a good high frequency bandwidth compensation effect, the filter coefficients in the oDSP chip 301 may be configured, and the filter coefficients in the oDSP chip 301 may be obtained by calculation using an algorithm.
In the embodiment of the present application, in order to ensure that the filter in the oDSP chip 301 has a good high-frequency bandwidth compensation effect, a method for calculating a filter coefficient is provided, which is used for calculating a working coefficient of the filter in the oDSP chip 301, so that the error rate before correction of the optical module can be less than or equal to the target error rate.
Fig. 5 is a flow chart of a method of calculating filter coefficients according to some embodiments. As shown in fig. 5, a method for calculating a filter coefficient according to an embodiment of the present application includes:
s100: and obtaining an original spectrogram.
And when the coherent optical module works normally, acquiring spectrum data to acquire an original spectrum chart. For example, the light of the light emitting end of the coherent light module is input to the spectrometer, the spectrometer automatically collects the input light spectrum data, and the PC obtains an original spectrum diagram of the light emitting end of the light module through a data line of the spectrometer. FIG. 6 is an original spectrum diagram of a coherent optical module according to some embodiments; where the abscissa is the spectral frequency and the ordinate is the spectral power (dBm), the data in the figure are the raw spectral data of the coherent optical module without compensation.
In some embodiments of the present application, since the original spectrogram is substantially symmetrical on both sides of the center wavelength, to facilitate the operation, the original spectrogram is imported and the abscissa of the spectrum center is shifted to 0. Fig. 7 is a schematic diagram of a structure for shifting the abscissa of the spectrum center of the original spectrogram to 0, as shown in curve (1) in fig. 7, according to some embodiments.
S200: an ideal spectrogram Sideal is set based on the Nyquist filter.
The swedish scientist hali nyquist has proposed in 1928 a distortion-free condition for the transmission of digital waveforms over a noise-free linear channel, called the nyquist criterion, wherein the nyquist first criterion makes the sampling point distortion-free criterion, or the inter-symbol interference-free criterion, a problem with the shape of the received pulses that the receiver does not produce inter-symbol interference. For baseband transmission systems, to achieve no inter-symbol interference, the system transfer function H (f) is a rectangular function with a single-side bandwidth of 1/2T (i.e., an ideal nyquist filter), and the time domain waveform is H (T) =sinc (T/T), which is called ideal nyquist pulse shaping.
In the embodiment of the application, the ideal spectrogram Sideal is obtained by debugging amplitude and bandwidth coefficients based on the Nyquist filter. For ease of calculation, in some embodiments of the present application, the right spectrum of the ideal spectrogram Sideal is used. Fig. 8 is an ideal spectrum provided according to some embodiments, and curve (2) in fig. 8 is the right spectrum of the ideal spectrum ideal. Of course, the embodiments of the present application are not limited to the right spectrum using the ideal spectrogram ideal.
S300: and (3) resampling the original spectrogram and carrying out normalization processing on the amplitude and the frequency interval by referring to the resolution and the amplitude of the ideal spectrogram Sideal to obtain a spectrum measurement function Smeasure.
And (3) resampling the original spectrogram by referring to the resolution and the amplitude of the ideal spectrogram Sideal, and carrying out normalization processing on the original spectrogram to the ideal spectrogram Sideal, so that the data of the original spectrogram and the amplitude and the frequency interval of the ideal spectrogram Sideal are in the same unit, and a spectrum measurement function Smeasure is obtained.
In some embodiments of the present application, the right half of the original spectrogram origin is resampled, and then normalized to the ideal spectrogram Sideal, so that the amplitude and frequency interval of the ideal spectrogram Sideal are in the same unit.
S400: the compensation filter transfer function Scomp is calculated from the compensation filter transfer function scomp=ideal/smeasure.
In this embodiment of the present application, the compensation function is set to Scomp (W), the spectrum measurement function is Smeasure (W) and the desired spectral response is Snyquist (W), scomp (W) ×smeasure (W) =snyquist (W), the distortion may be obtained by Scomp (W) =snyquist (W)/Smeasure (W), the Smeasure (W) data is collected by the spectrometer, snyquist (W) is an ideal spectral map signal determined by setting the bandwidth, the amplitude and the coefficient, and therefore, the compensation filter transmission function scomp=ideal/Smeasure may be obtained by calculation. Fig. 9 is a schematic diagram of a compensation filter transfer function according to an embodiment of the present application, and curve (4) in fig. 9 is a compensation filter transfer function Scomp.
S500: the filter coefficients are obtained from a back-reconstruction of the compensation filter transfer function Scomp.
When the compensation filter transfer function Scomp is obtained, the filter Tap coefficients are obtained by inverse reconstruction from the compensation filter transfer function Scomp. The reverse reconstruction order of the Tap coefficient of the filter can be adjusted according to the order of the filter in the oDSP chip; if the order of the filter in the oDSP chip is 9, the inverse reconstruction order of the Tap coefficient of the filter is 9.
And writing the filter coefficient obtained by the calculation method of the filter coefficient into a register of the oDSP chip to perform optical module high-frequency bandwidth compensation. Fig. 10 is a spectrum diagram of a spectrum-compensated optical module with a compensated high bandwidth, according to some embodiments.
In some embodiments of the present application, in order to further ensure the performance of the filter coefficient obtained by the method for calculating the filter coefficient provided in the embodiments of the present application, the method for calculating the filter coefficient provided in the embodiments of the present application further includes: writing the obtained filter coefficient into a register of an oDSP chip, and detecting the error rate before correction of an optical signal output by a transmitting end of a coherent optical module; confirming whether the error rate before correction is larger than a target error rate; if the error rate before correction is larger than the target error rate, adjusting the ideal spectrogram Sideal through adjusting the amplitude and the bandwidth coefficient, and obtaining the filter coefficient again based on the adjusted ideal spectrogram Sideal. In the embodiment of the application, the target error rate can be selected according to the technical standard or requirement; configuring the Tap coefficient obtained by the calculation method of the filter coefficient to a register of an oDSP chip, and verifying the corresponding error rate before correction; and when the error rate before correction does not reach the target error rate, continuously adjusting the filter coefficient so as to enable the error rate before correction to reach the target error rate.
In some embodiments of the present application, the Tap coefficient generated by the factor corresponding to the optimal bit error rate may be selected according to the bit error rate index of the receiving end of the optical module by traversing the amplitude, bandwidth and alpha factor of the ideal spectrogram ideal. In general, the Tap coefficient corresponding to the lowest point of the error rate is the optimal Tap coefficient of the filter in the oDSP chip.
According to the method for calculating the filter coefficient, the optimal compensation coefficient can be found, so that the filter supplementing method of the oDSP chip is simple and high in speed, the filter in the oDSP chip is guaranteed to have a good high-frequency bandwidth compensation effect, the problem that the bandwidth of a laser driver and a modulator is insufficient, and meanwhile, the problem that the bandwidth of a modulation system is insufficient due to high-frequency damage caused by wiring of the module on a circuit board in the connection process is solved, and the error rate of an optical module before correction is optimal is solved.
Furthermore, the calculation method of the filter coefficient provided by the embodiment of the application has strong operability, the common spectrometer is used for collecting data, the light of the light emitting end of the coherent light module is input to the spectrometer before spectrum compensation is carried out, the PC end obtains the original data of the light emitting end spectrum through the data line of the spectrometer, the operation is simple, the data obtaining is rapid, and the compensation is flexible; the method has the advantages that the flexibility is good, the compensation frequency spectrum can be arbitrarily expanded or contracted, and the shape of the frequency spectrum can be flexibly changed by adjusting the parameters of an ideal filter; the transfer function Tap coefficient can be flexibly set according to the order of the DSP filter of the target module, and the compensation requirement of the oDSP filter is adapted; the compensation speed is high, the coefficients are calculated through an algorithm, the coefficients are led into an odsp filter, after the PC end obtains the original spectrum data, the calculation of the Tap coefficients of the transfer function is completed rapidly at the PC end, and the Tap coefficients are written into a DSP register through a communication line with a module, so that the whole process is free from manual intervention except for inserting optical fibers, and a conclusion is verified immediately, so that the optimal compensation coefficients can be found.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and are not limiting thereof; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.
Claims (6)
1. A method of calculating filter coefficients for an oDSP chip in a coherent optical module, the method comprising:
acquiring an original spectrogram;
setting an ideal spectrogram Sideal based on a Nyquist filter;
resampling an original spectrogram and carrying out normalization processing on the amplitude and the frequency interval by referring to the resolution and the amplitude of the ideal spectrogram Sideal to obtain a spectrum measurement function Smeasure;
calculating to obtain a compensation filter transfer function Scomp according to the compensation filter transfer function scomp=ideal/Smeasure;
the filter coefficients are obtained from a back-reconstruction of the compensation filter transfer function Scomp.
2. The method according to claim 1, wherein the method further comprises: writing the obtained filter coefficient into a register of an oDSP chip, and detecting the error rate before correction of an optical signal output by a transmitting end of a coherent optical module;
confirming whether the error rate before correction is larger than a target error rate;
if the error rate before correction is larger than the target error rate, adjusting the ideal spectrogram Sideal through adjusting the amplitude and the bandwidth coefficient, and obtaining the filter coefficient again based on the adjusted ideal spectrogram Sideal.
3. The method of claim 1, wherein, with reference to the resolution and amplitude of the ideal spectrogram ideal, resampling the original spectrogram and normalizing the amplitude and frequency intervals, the method further comprises, prior to obtaining the spectral measurement function Smeasure:
the original spectrogram is imported and the abscissa of the spectrum center is shifted to 0.
4. A method according to claim 3, wherein resampling the original spectrogram and normalizing the amplitude and frequency intervals to obtain a spectral measurement function Smeasure comprises:
and resampling the right side of the shifted original spectrogram 0, and carrying out normalization processing on the amplitude and the frequency interval to obtain a spectrum measurement function Smeasure.
5. The method of claim 1, wherein obtaining an original spectrogram comprises:
and inputting the optical signal output by the transmitting end of the coherent optical module into a spectrometer, and acquiring the optical signal through the spectrometer to obtain an original spectrogram.
6. An optical module, comprising:
a circuit board;
the light emitting assembly is electrically connected with the circuit board and is used for emitting light signals;
an oDSP chip is arranged on the circuit board and is electrically connected with the light emitting component, the oDSP chip comprises a filter, the filter is used for pre-compensating and processing electric signals transmitted to the light emitting component so that the error rate of the coherent light module before correction is smaller than or equal to the target error rate, and the coefficient of the filter is the coefficient calculated by the method according to claim 1.
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| JP7059637B2 (en) * | 2018-01-11 | 2022-04-26 | 富士通株式会社 | Signal processing device and signal processing method |
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| WO2016173324A1 (en) * | 2015-04-30 | 2016-11-03 | 中兴通讯股份有限公司 | Optical signal to noise ratio monitoring method and device |
| CN110031081A (en) * | 2019-03-26 | 2019-07-19 | 长江大学 | A kind of phi-OTDR distributed optical fiber vibration signal antinoise method and system based on modified wavelet packet |
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