Optical linearization technology

Abstract

An integrated circuit is described. This integrated circuit may include an optical transmitter circuit that outputs an optical signal (such as an optical pulse or FMCW optical signal) having a carrier frequency (or chirp) pattern as a function of time, and the modulated signal corresponding to the carrier frequency pattern, associated with the light source, includes pre-distortion to reduce the nonlinearity associated with the optical transmitter circuit. Furthermore, the integrated circuit may include a feedback circuit that measures the nonlinearity (e.g., using an interferometer) and dynamically adjusts the pre-distortion based at least partly on the measured nonlinearity. It should be noted that the integrated circuit may provide closed-loop adjustment of the pre-distortion. In some embodiments, the correction of nonlinearity may be performed in the frequency domain.

Description

[Technical Field]

[0001] This disclosure relates to a technique for determining the predistortion of a modulated signal corresponding to the carrier frequency pattern of a chirp transmitted signal in order to linearize an optical measurement device or system (such as a light detection and ranging device or system, i.e., a LiDAR measurement device or system). [Background technology]

[0002] LiDAR uses optical signals to measure the relative position and velocity of one or more objects in the environment. Using a narrow beam width in LiDAR measurements can reduce the amount of clutter or transient signals in the measurement. However, using higher carrier frequencies in LiDAR measurements generally increases the Doppler effect, resulting in a mixing of signals related to relative position and velocity. Furthermore, the high frequencies used in LiDAR typically impose strict constraints on the linearity of the components within the measurement system. For example, an error of tens or hundreds of kilohertz at a carrier frequency of 100 terahertz corresponds to an error of less than one part per million (ppm). Additionally, nonlinear constraints are typically determined across the modulation bandwidth. [Overview of the project] [Means for solving the problem]

[0003] Embodiments of an integrated circuit are described. The integrated circuit includes an optical transmitting circuit that outputs an optical signal having a carrier frequency (or chirp) pattern as a function of time, and the modulated signal corresponding to the carrier frequency pattern in relation to the light source includes pre-distortion to reduce nonlinearity associated with the optical transmitting circuit. Furthermore, the integrated circuit includes a feedback circuit that measures the nonlinearity and dynamically adjusts the pre-distortion based at least in part on the measured nonlinearity.

[0004] Integrated circuits can provide closed-loop adjustment for pre-strain.

[0005] Furthermore, pre-distortion may include the direct modulation of a current or voltage related to a modulation signal, such as a current or voltage applied to a light source (such as a laser) within an optical transmission circuit.

[0006] In some embodiments, the integrated circuit may provide closed-loop adjustment of pre-strain.

[0007] Furthermore, the feedback circuit can measure the carrier frequency of the output optical signal as a function of time.

[0008] In addition, the feedback circuit may include an interferometer.

[0009] In some embodiments, at least a portion of the dynamic adjustment may be performed in the frequency domain. Furthermore, the feedback circuit may compare at least a portion of the frequency band related to the Fourier transform (such as the Fast Fourier Transform or FFT) of the output optical signal with the target waveform (or pattern). Furthermore, the feedback circuit may adjust the pre-distortion so that the time average of the comparison is zero. For example, the pre-distortion adjustment may be performed in bin units or frequency interval units.

[0010] Another embodiment provides an electronic device including an integrated circuit.

[0011] Another embodiment provides a system including an integrated circuit.

[0012] Another embodiment provides a method for closed-loop adaptation of a modulated signal corresponding to the carrier frequency pattern of an optical signal provided by an optical transmission circuit in relation to a light source. This method includes at least some operations performed by an integrated circuit.

[0013] The outline of the present invention is presented to illustrate several exemplary embodiments in order to provide a basic understanding of some aspects of the subject matter described herein. It will be understood that the features described above are illustrative and should not be construed as limiting the scope or spirit of the subject matter described herein. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following embodiments, drawings, and claims for carrying out the invention. [Brief explanation of the drawing]

[0014] [Figure 1A] This is a block diagram illustrating the circuit diagram of an optical transmission circuit according to some embodiments of the present disclosure. [Figure 1B] This is a block diagram illustrating the circuit diagram of an optical transmission circuit according to some embodiments of the present disclosure. [Figure 2] This flowchart illustrates an example of a method for closed-loop adaptation of a modulated signal corresponding to the carrier frequency pattern of an optical signal in relation to a light source according to some embodiments of the present disclosure. [Modes for carrying out the invention]

[0015] Note that similar reference numerals indicate corresponding parts throughout the drawing. Furthermore, multiple instances of the same part or component (such as subnumbers) may be designated by a common number separated from the instance number by a dash.

[0016] The integrated circuit is described below. This integrated circuit may include an optical transmitter circuit that outputs an optical signal (such as an optical pulse or continuous wave optical signal) having a carrier frequency (or chirp) pattern as a function of time, and the modulated signal corresponding to the carrier frequency pattern in relation to the light source includes pre-distortion to reduce the nonlinearity associated with the optical transmitter circuit. Furthermore, the integrated circuit may include a feedback circuit that measures the nonlinearity (e.g., using an interferometer) and dynamically adjusts the pre-distortion based at least partly on the measured nonlinearity. It should be noted that the integrated circuit may provide closed-loop adjustment of the pre-distortion. In some embodiments, the correction of nonlinearity may be performed in the frequency domain.

[0017] By dynamically adjusting the pre-distortion of the modulated signal, these circuit techniques can enable integrated circuits to have improved performance. In particular, integrated circuits can reduce or eliminate the nonlinearity associated with optical transmission circuits. For example, circuit techniques can reduce or eliminate changes in nonlinearity associated with changes in ambient temperature and / or the aging of one or more components in the optical transmission circuit. More generally, integrated circuits can reduce or eliminate the nonlinearity associated with optical transmission circuits. As a result, circuit techniques can facilitate the increased use of integrated circuits in a wide variety of systems, electronic devices, and application equipment. For example, integrated circuits can be used in semi-autonomous and / or autonomous or self-driving vehicles.

[0018] Next, embodiments of the circuit technology will be described. This circuit technology can be implemented using one or more integrated circuits. One or more integrated circuits may include some or all of the components and associated functions described. Figures 1A and 1B are block diagrams illustrating the schematic of the optical transmission circuit 100.

[0019] The optical transmission circuit 100 may provide or output an optical transmission signal. These optical transmission signals may be associated with a light source and have a carrier wave frequency that is varied as a function of time based at least in part on a modulated signal corresponding to a carrier wave frequency pattern. For example, the optical transmission signal may include a Frequency Modulated Continuous Wave (FMCW) signal. However, in other embodiments, the optical transmission signal may include a pulse signal. In the following description, an FMCW optical transmission signal is used as an illustrative example.

[0020] Accordingly, LiDAR measurement may use a chirp signal in which the carrier frequency of the transmitted optical signal varies as a function of time. For example, the carrier frequency may be varied linearly between a start carrier frequency and an end carrier frequency over a chirp frame. This chirp pattern may be repeated one or more times within the chirp frame. Further, the chirp pattern may be repeated in subsequent chirp frames. In some embodiments, the chirp pattern may include a sawtooth pattern, a triangular wave pattern, or a trapezoidal pattern. The triangular wave pattern may allow the contributions of the reflected or received optical signals related to the relative position and velocity of one or more objects in the environment to be separated or disambiguated. It should be noted that the relative position and velocity in the received signal may be measured by beating the received signal with the transmitted (or chirp) signal, which may result in a beat frequency proportional to the time delay of the received signal, a Doppler shift related to the relative velocity, and a slope of the carrier frequency as a function of time.

[0021] One of the elements of an FMCW LiDAR system with good performance is the linearity of the light source (such as a laser) for the optical transmission signal. For example, the non-linearity required to have a negligibly small penalty on the probability and accuracy of relative position (or range) and velocity detection is on the order of tens to hundreds of parts per million of the chirp bandwidth.

[0022] In the disclosed circuit technology, linearization of a light source (e.g., a laser) can be achieved by measuring the laser frequency using an interferometer, and by pre-correcting or pre-distorting the output that drives the laser (such as the output of a digital-to-analog converter or DAC output).

[0023] The optical transmission circuit 100 shows a general description of the circuit technology. In FIG. 1A and FIG. 1B, it should be noted that block 110 may include components within a measurement device or system to be controlled, block 112 may include intermediate results, block 114 may include the output of the circuit technology, block 116 may include inputs used to construct the circuit technology, bar 118 may include forks and junctions that illustrate different alternatives for the circuit technology, and the rest of the blocks and circles may include operations. It should be noted that when one arrow enters one of the bars 118 and multiple arrows exit from one of the bars 118, this may mean that only one of the outputs can be used in a particular implementation of the circuit technology. When multiple arrows enter one of the bars 118 and one arrow exits therefrom, it may also mean that only one of the inputs can be used in a particular implementation of the circuit technology.

[0024] The components within the measurement device or system to be controlled may include a DAC that drives the modulation port of the laser via a signal conditioning block that performs functions such as DC removal and anti-aliasing filtering. Further, the coupler may receive a sample of the laser output, measure the laser carrier frequency, and close the feedback loop in the optical transmission circuit 100. The coupler may also transmit a part of the laser beam or the output optical signal, which may allow the rest of the measurement device or system to operate.

[0025] In some embodiments, the optical signal to be monitored can be measured by one of several methods. For example, a laser or output optical signal can be input to one of several interferometers. An optical beam splitter can split the output optical signal. Different delays can be applied to the two optical paths. The optical signals are then coupled, and a photodiode can be used to measure the frequency difference between the two optical signals. Ideally, the output of the interferometer may be a sinusoidal function.

[0026] In one approach, the optical signal to be monitored may be measured using a short-path real interferometer (up to a few centimeters) and a power tap. The monitored signal may need to be converted into a frequency signal as a function of time by performing signal tuning, power fluctuation correction, nonlinearity compensation, and compensation for the sin(x) function produced by the interferometer. The short-path real interferometer may be kept in an orthogonal phase state (for example, by controlling the laser frequency or the length of the interferometer). Note that in this embodiment, the beat period may be 1 ms and the chirp period may be, for example, 10 μs. As a result, the sinusoidal output occurs within a range of 0.01 to 0.1 of the full cycle, so the output of the interferometer can be linear (and therefore, an arctan function may not be required to linearize the output of the interferometer). In some embodiments, the arctan function may be replaced by a polynomial approximation which is easier to compute or implement.

[0027] Alternatively, the optical signal to be monitored may be measured using a long-path real interferometer (within a range of several tens of centimeters to several meters). The optical signal to be monitored may also need to be adjusted. A Hilbert transform may be used to obtain the imaginary part of the optical signal to be monitored, based at least part of the real part of the optical signal to be monitored. The output of the Hilbert transform can then be converted into a frequency signal as a function of time by a combination of the arctan function, phase unwrapping, slope sign assignment, and scaling.

[0028] In some embodiments, the optical signal being monitored may be measured using a complex interferometer (which may be short-path or long-path). For example, a long-path interferometer may have a value obtained by dividing the beat period by a chirp period of 10 to 100. However, long-path interferometers used in real interferometry and / or complex interferometry can be several meters long, are expensive to implement without power loss (e.g., using delay lines in silicon photonics), and / or have high computational costs. Note that while a complex interferometer may be sensitive to the sign of the slope of the carrier frequency pattern, a real interferometer may measure or be sensitive to the absolute value of the slope of the carrier frequency pattern.

[0029] It should be noted that a complex interferometer may include two optical and analog paths for measuring the real and imaginary parts of a transmitted optical signal. The complex signal can then be converted to a frequency signal as a function of time by calculating the arctan function, unwrapping the phase, and scaling.

[0030] It should be noted that each of the approaches described above involves signal conditioning processes such as filtering and / or averaging the signal across multiple chirp frames.

[0031] After the frequency signal as a function of time is obtained using one of the aforementioned options, this circuit technique may employ further processing. In particular, the frequency signal as a function of time may have a length that depends at least in part on the chirp frame length and the interferometer sampling frequency. The aforementioned signal length can be converted to a second signal length that is convenient for performing an FFT using the available hardware in the optical transmission circuit 100 by performing interpolation. However, zero-padding may or may not be used in this operation.

[0032] After the interpolated frequency signal as a function of time is obtained, it can be subtracted from the target waveform. This target waveform may be the target frequency (the input to this circuit technique) or a modified version of the target frequency (e.g., with rounded edges). Such operation can improve the convergence of this circuit technique and avoid unwanted high-frequency signals in the pre-distorted waveform.

[0033] After subtraction, an error signal may be obtained. Then, an FFT is calculated on the error signal, thereby allowing the spectrum of the error signal to be measured.

[0034] Furthermore, the DC component of the resulting signal can be discarded. Additionally, at least some of the N complex terms of the FFT can be used in this circuit technique (where N is a non-zero integer). Generally, higher frequencies do not need to be tracked, but in some embodiments, N can be as large as the number of coefficients in the FFT.

[0035] In addition to the above, N proportional-integral-derivative (PID) controllers or loops (sometimes referred to as "PID circuits") can be run in parallel on these FFT coefficients. This can repeatedly zero out the time-averaged error of each frequency component (or bin). Some or all of the proportionality constants (K) of the FFT coefficients (or bins) can be used. P ), integral coefficient (K I ), and / or the derivative (K D Please note that these may differ.

[0036] The inverse fast factor (iFFT) of the outputs of N PIDs can be calculated beforehand to obtain a first version of the compensation function. In some embodiments, the iFFT can be calculated by adding zeros to the signal consisting of the N outputs of the PIDs. For example, the values ​​corresponding to the DC component of the FFT can be replaced with zeros before performing the iFFT.

[0037] In some embodiments, the FFT uses N bins out of M bins of the FFT, where N and M are non-zero integers and N is less than or equal to M. For example, N may be equal to the number of PID controllers or loops. Furthermore, when N is less than M, all M bins may be used by padding MN bins with zeros when performing an iFFT.

[0038] It should be noted that the DAC waveform may include the number of samples, which is a function of the chirp frame length and the DAC sampling frequency. In some embodiments, interpolation may be performed to make the iFFT output the correct size.

[0039] Furthermore, at this point, the initially pre-distorted waveform may be added. This can improve the convergence of the circuit technique. For example, a pre-distorted waveform may be added from a previous example or iteration of the circuit technique. Note that a previous example or iteration of the circuit technique may be determined during the calibration operation performed when fabricating the optical transmission circuit. Therefore, the pre-distorted waveform may be stored in a register, memory, or computer-readable medium.

[0040] Furthermore, scaling, DC offset, and other DAC corrections may be performed. For example, compensation for DAC integral nonlinearity (INL) may be applied to the optical transmission circuit 100 at this point. The result may be a DAC pre-distortion waveform that can be used by the DAC to drive the frequency modulation port of a laser or light source.

[0041] In some embodiments, this circuit technology monitors the slope, adjusts the target frequency as a function of time, calculates the linearity of the laser or light source, monitors the convergence of the linearization in this circuit technology, and / or controls each PID controller (or PID circuit) P ,K I ,K DThis may include calculations of the slope. Slope monitoring can be used to have good ranging accuracy. In particular, the slope can be easily measured in the output of a frequency signal as a function of time, for example, by fitting one or more linear polynomials to the segments of the chirp frame corresponding to the most linear part of each slope (e.g., the central 90%).

[0042] Furthermore, adjusting the target frequency as a function of time can be used to reduce the high-frequency components of the target frequency (for example, a triangular wave pattern may have sharp edges that can be difficult for the laser or light source to track in direct modulation, thereby introducing high-frequency components into the DAC pre-distortion waveform). For example, in direct modulation, the current injected into the laser or light source or the voltage applied to the laser or light source can be modulated to change the excitation of the laser or light source.

[0043] Furthermore, laser linearity can be calculated in the error signal in either the time or frequency domain (for example, before or after the FFT). Functional safety (FUSA) can be used in this case, for example, because performance may degrade if the linearity of the laser or light source is poor. Note that laser linearity may trigger corrective measures or at least some action by the optical transmission circuit 100.

[0044] In addition, at the output of the PID controller, the convergence of linearization in the present circuit technology may be monitored. The optical transmission circuit 100 may be considered to be converged when the coefficients have a change less than a given amount at each iteration. Such a convergence criterion can be useful for managing the optical transmission circuit 100, for example, for controlling the transition from "intensive initial linearization" in which the laser or light source is brought into a state of being well linearized from nonlinear behavior. When such a situation occurs, the control circuit 110 of the optical transmission circuit 100 may transition to a low-speed monitoring mode or low-speed update mode in which only slight corrections to the pre-distortion are performed. Alternatively, when the optical transmission circuit 100 has converged and the linearity is not good, the optical transmission circuit 100 (such as the control circuit 110) may take corrective or remedial measures, such as adjusting the PID coefficients or changing the target frequency signal. It should be noted that in some embodiments, the PID controller may converge in no more than 1000 iterations.

[0045] In some embodiments, K P , K I , K D may be calculated for each PID controller (and thus for each complex coefficient of the FFT). The optical transmission circuit 100 is configured such that K P , K I , K DInitial values ​​for can be used to start. Then, each frequency component may have its own loop gain and phase shift. Loop gains are equalized so that all PID controllers converge at the same rate and / or all PID controllers can stabilize. Furthermore, phase shifts may need to be compensated to avoid operation, such as when a sine function generates a cosine function, which can cause instability in the optical transmitter circuit 100 (and generally the measurement system). Furthermore, loop gains and phase shifts can be monitored based at least in part on the convergence of the coefficients (for example, if they loop, the phase may be incorrect, and conversely, if they converge slower than others, the gain may be incorrect). In some embodiments, loop gains and phase shifts may be calculated in an initial training phase. Such a training phase may include inserting an array of zeros with all but one value into the complex correction coefficients in the frequency domain, and / or setting the target frequency to zero. The optical transmitter circuit 100 can then measure the magnitude and phase of the error coefficients in the frequency domain.

[0046] It should be noted that the numerical values ​​listed in Figures 1A and 1B are illustrative examples. Different numerical values ​​may be used in other embodiments. Furthermore, the optical transmission circuits in Figures 1A and 1B may include fewer or additional components, two or more components may be combined into a single component, a single component may be implemented using two or more separate components, and / or the positions of one or more components may be changed.

[0047] Next, embodiments of the method will be described. Figure 2 shows a flowchart illustrating an example of a flow 200 of a method for closed-loop adaptation of a modulated signal relating to a light source and corresponding to the carrier frequency pattern of an optical signal, which can be performed by an optical transmitting circuit (such as the optical transmitting circuit 100 in Figures 1A and 1B). During operation, the optical transmitting circuit may measure nonlinearity related to the optical transmitting circuit (process 210). The optical transmitting circuit may then dynamically adjust the pre-distortion in the modulated signal relating to the light source and corresponding to the carrier frequency pattern, based at least in part on the measured nonlinearity (process 212). The optical transmitting circuit may then provide or output an optical signal based at least in part on the dynamically adjusted modulated signal (process 214).

[0048] In some embodiments of the method flow 200, there may be additional or fewer actions. Furthermore, the order of actions may be changed, and / or two or more actions may be combined into a single action.

[0049] In the above description, direct modulation of a light source or laser in an optical transmission circuit or measurement system was used as an exemplary example; however, in other embodiments, the light source or laser may be modulated using a Mach-Zehnder interferometer (MZI). Furthermore, in the above description, circuit techniques using operations performed in the frequency domain were illustrated; however, in other embodiments, at least a portion of the operation may be performed in the time domain (for example, in samples).

[0050] The disclosed integrated circuits and circuit technologies may be (or may be included in) any electronic device or system. For example, an electronic device may include a mobile phone or smartphone®, a tablet computer, a laptop computer, a notebook computer, a personal computer or desktop computer, a netbook computer, a media player device, an ebook device, a MiFi® device, a smartwatch, a wearable computing device, a portable computing device, a consumer electronic device, an access point, a router, a switch, communication equipment, test equipment, a vehicle, a ship, an aircraft, an automobile, a truck, a bus, a motorcycle, manufacturing equipment, agricultural machinery, construction machinery, or any other type of electronic device.

[0051] While specific components are used to illustrate an embodiment of the integrated circuit, alternative embodiments may include different components and / or subsystems within the integrated circuit. Thus, an embodiment of the integrated circuit may include fewer components, additional components, different components, two or more components may be combined into a single component, a single component may be separated into two or more components, one or more components may be repositioned, and / or there may be different types of components.

[0052] Furthermore, the circuits and components in the embodiments of the integrated circuit may be implemented using any combination of analog and / or digital circuits, including bipolar, PMOS and / or NMOS gates or transistors. Additionally, the signals in the embodiments described above may include digital signals with approximately discrete values ​​and / or analog signals with continuous values. Moreover, the components and circuits may be single-ended or differential, and the power supply may be unipolar or bipolar. It should be noted that the electrical coupling or connection in the embodiments described above may be direct or indirect. In the embodiments described above, a single line corresponding to a route may represent one or more single lines or routes.

[0053] As mentioned above, integrated circuits can implement some or all of the functions of circuit technology. These integrated circuits may include hardware and / or software mechanisms used to implement functions related to circuit technology.

[0054] In some embodiments, the output of a process for designing an integrated circuit, or a part of an integrated circuit, including one or more of the circuits described herein, may be on a computer-readable medium, such as magnetic tape or optical or magnetic disk. The computer-readable medium may be encoded with data structures or other information describing circuits that can be physically exemplified in the integrated circuit or as part of an integrated circuit. Various formats may be used for such encoding, but these data structures are generally described in Caltech Intermediate Format (CIF), Calma GDS II Stream Format (GDSII), Electronic Design Interchange Format (EDIF), Open Access (OA), or Open Artwork System Interchange Standard (OASIS). A person skilled in the art of integrated circuit design can develop such data structures from the types of wiring diagrams and corresponding descriptions described above and encode the data structures onto a computer-readable medium. A person skilled in the art of integrated circuit manufacturing can use such encoded data to manufacture an integrated circuit, including one or more of the circuits described herein.

[0055] While some of the operations in the embodiments described above are implemented in hardware or software, generally speaking, the operations in the embodiments described above can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations in the embodiments described above can be performed in hardware, software, or both. For example, at least some of the operations in circuit technology can be implemented using program instructions executed by a processor or in firmware within an integrated circuit.

[0056] Furthermore, while numerical examples are provided in the preceding description, different numerical values ​​may be used in other embodiments. Consequently, the numerical values ​​provided are not intended to be limiting.

[0057] The above description refers to "several embodiments." Note that "several embodiments" describes a subset of all possible embodiments, but does not always specify the same subset of embodiments.

[0058] The foregoing description is intended to enable those skilled in the art to construct and use the configurations of the Disclosure and is provided in the context of a particular application and its requirements. Furthermore, the foregoing description of embodiments of the Disclosure is presented for illustrative and illustrative purposes only. They are not intended to be exhaustive or to limit the Disclosure to the forms disclosed. Thus, many modifications and variations will be obvious to those skilled in the art, and the general principles set forth herein may also be applicable to other embodiments and applications without departing from the spirit or scope of the Disclosure. In addition, the foregoing description of embodiments is not intended to limit the Disclosure. Thus, the Disclosure is not intended to be limited to the illustrated embodiments, but rather to apply in the broadest scope consistent with the principles and features disclosed herein. [Explanation of Symbols]

[0059] 100 Optical Transmitter Circuit 110 Control circuit 200 ways

Claims

1. An optical transmitting circuit configured to output an optical signal having a carrier frequency pattern as a function of time, wherein the modulation signal corresponding to the carrier frequency pattern related to the light source includes pre-distortion to reduce nonlinearity related to the optical transmitting circuit, An integrated circuit comprising a feedback circuit configured to measure the nonlinearity and to dynamically adjust the pre-strain based at least part of the measured nonlinearity.

2. The integrated circuit according to claim 1, wherein the integrated circuit is configured to provide closed-loop adjustment of the pre-strain.

3. The integrated circuit according to claim 1, wherein the pre-distortion includes direct modulation of a current or voltage related to the modulation signal.

4. The integrated circuit according to claim 1, wherein the feedback circuit is configured to measure the carrier frequency of the output optical signal as a function of time.

5. The integrated circuit according to claim 1, wherein the feedback circuit includes an interferometer.

6. The integrated circuit according to claim 1, wherein the dynamic adjustment of the nonlinearity is performed in the frequency domain.

7. The integrated circuit according to claim 1, wherein the feedback circuit is configured to compare at least a portion of the frequency band related to the Fourier transform of the output optical signal with a target waveform.

8. The integrated circuit according to claim 7, wherein the feedback circuit is configured to adjust the pre-distortion so that the time average of the comparison becomes zero.

9. A method for closed-loop adaptation of a modulated signal corresponding to the carrier frequency pattern of an optical signal in relation to a light source, By optical transmission circuit, Steps to measure nonlinearity, Based at least in part on the measured nonlinearity, the steps include dynamically adjusting the pre-distortion in the modulation signal corresponding to the carrier frequency pattern in relation to the light source, A method comprising the step of providing the optical signal based at least part on the dynamically adjusted modulated signal.

10. The method according to claim 9, further comprising the step of providing closed-loop adjustment of the pre-strain.

11. The method according to claim 9, wherein the pre-distortion includes direct modulation of a current or voltage related to the modulation signal.

12. The method according to claim 9, wherein the method includes the step of measuring the carrier frequency of an output optical signal as a function of time.

13. It is an integrated circuit, An optical transmitting circuit configured to output an optical signal having a carrier frequency pattern as a function of time, wherein the modulation signal corresponding to the carrier frequency pattern in relation to a light source includes pre-distortion to reduce nonlinearity related to the optical transmitting circuit, An electronic device comprising an integrated circuit including a feedback circuit configured to measure the nonlinearity and to dynamically adjust the pre-strain based at least part of the measured nonlinearity.

14. The electronic device according to claim 13, wherein the integrated circuit is configured to provide closed-loop adjustment of the pre-strain.

15. The electronic device according to claim 13, wherein the pre-distortion includes direct modulation of a current or voltage related to the modulation signal.

16. The electronic device according to claim 13, wherein the feedback circuit is configured to measure the carrier frequency of the output optical signal as a function of time.

17. The electronic device according to claim 13, wherein the feedback circuit includes an interferometer.

18. The electronic device according to claim 13, wherein the dynamic adjustment of the nonlinearity is performed in the frequency domain.

19. The electronic device according to claim 13, wherein the feedback circuit is configured to compare at least a portion of the frequency band related to the Fourier transform of the output optical signal with a target waveform.

20. The electronic device according to claim 19, wherein the feedback circuit is configured to adjust the pre-distortion such that the time average of the comparison becomes zero.

Images