992 results about "Continuous wave" patented technology

A method of making a vacuum insulating panel, the vacuum insulating panel comprising a first glass substrate, a second glass substrate, a plurality of spacers provided in a gap between at least the first and second glass substrates, and a seal provided between at least the first and second glass substrates, the seal comprising a first seal layer and / or a second seal layer. The method may include laser heating, using a laser beam from a continuous wave near-IR laser, seal material in order to form the first seal layer; wherein the laser heating may include causing the laser beam to move at a lateral speed of from about 5-70 mm / second relative to the substrates and the first seal material so that the laser beam at least partially passes through at least one of the glass substrates and impinges upon at least the second seal layer in order to heat the second seal layer and fire and / or sinter the first seal material thereby forming the first seal layer.

A method of making a vacuum insulating panel, the vacuum insulating panel including a first glass substrate, a second glass substrate, a plurality of spacers provided in a gap between at least the first and second glass substrates, and a seal provided between at least the first and second glass substrates, the seal comprising a first seal layer. The method may include: providing first seal material for the first seal layer in a location at least partially between at least the first and second glass substrates; laser heating, using a laser beam from a continuous wave near-IR laser, the first seal material in order to form the first seal layer; wherein said laser heating may comprise using the laser beam, having a size of from about 2-15 mm, so that the laser beam at least partially passes through at least one of the glass substrates to fire and / or sinter the first seal material thereby forming the first seal layer, in a manner so that the first seal layer a density of from about 2.8-4.0 g / cm3; and after forming the first seal layer, evacuating the gap to a pressure less than atmospheric pressure.

The invention discloses a distributed photovoltaic access power distribution network relay protection analysis method and system, and belongs to the technical field of photovoltaic grid connection, and the method specifically comprises the steps: injecting a dynamic resonance detection signal at the AC side of a current converter of a photovoltaic grid-connected system, and enabling the frequency to be matched with the natural resonance frequency of a target section; analyzing the energy focusing effect of the dynamic resonance detection signal in the power distribution network, and generating a resonance energy distribution map; when the energy density of a certain section in the resonance energy distribution map exceeds a preset threshold value, the photovoltaic output current waveform is adjusted to be a discontinuous waveform containing periodic intermittent cutoff; based on the reflection delay difference of the waveform in the fault section, constructing a space-time mapping model of a fault point, and analyzing and determining a fault position; according to an output result of the space-time mapping model, controlling a photovoltaic side circuit breaker and a power grid side relay to execute a selective tripping action based on waveform phase synchronization; according to the invention, the sensitivity and reliability of distributed photovoltaic access power distribution network relay protection are improved.

The invention discloses a snapshot type hyperspectral imaging industrial online sorting system which comprises a support assembly, an optical imaging assembly and a motion control assembly. The bracket assembly consists of a bottom plate, and an adjustable bracket and a fixed bracket which are fixed on the bottom plate; the optical imaging assembly comprises a lighting unit, an imaging objective lens and a snapshot type hyperspectral camera, and can synchronously obtain space image information of a measured object and spectral information of a continuous wave band in a single exposure process; the motion control assembly realizes automatic transmission of the measured object through the transmission platform; the data processing module is integrated with an image preprocessing unit, a spectral analysis unit and a spectral database, and is used for end-to-end closed-loop control from original hyperspectral data generation to sorting decision making; the system adopts a metasurface light splitting structure to realize real-time decoding, performs material or category identification by using a pre-trained classification model, and finally automatically generates a sorting decision signal according to an identification result to drive a motion control assembly to complete sorting operation.

A monitoring system is presented for monitoring vital signs of subject(s). The monitoring system includes a control system configured for signal communication with a frequency modulated continuous wave (FMCW) radar to process measured data which is received from a single-channel front end of receiver of said FMCW radar and which is in the form of data matrix indicative of consecutive beat signals. The control system comprises a data processing utility comprising: a localization module configured and operable to process the measured data indicative of said data matrix and provide support recovery data indicative of the received signals originated at localized one or more subjects; and a vital signs monitoring module configured and operable to analyze the support recovery data and monitor vital signs of said localized one or more subjects.

The invention provides a sensing system fusing optical fiber vibration and acoustic emission, a monitoring method and a device, and relates to the technical field of optical fiber sensing. The device comprises a light source module, a sensing optical fiber, a detection module and a controller, the light source module is used for respectively emitting modulation pulse light for vibration monitoring and continuous wave laser for acoustic emission monitoring; the sensing optical fiber is arranged along a monitored structure or area, and at least one optical fiber acoustic emission sensing head is connected to the optical fiber in series. The detection module collects Rayleigh scattering light and beat frequency signals at all positions in the sensing optical fiber through a circulator and a coherent light receiver, and optical signals are converted into electric signals; wherein the electric signals comprise vibration electric signals and acoustic emission electric signals; the signal processing unit carries out phase demodulation and envelope analysis processing on the collected vibration electric signals and acoustic emission electric signals so as to obtain vibration waveforms and acoustic emission event space-time information along all points of the optical fiber. According to the invention, a monitoring task fusing vibration and acoustic emission can be accurately completed.

A nonlinear all optical machine learning system (NAOMLS) with nonlinear optical resonator-based continuous wave and / or spiking neurons (NORs) and linear optical components or layers (LOL) learns to implement target tasks after machine learning based direct and / or indirect inverse design and / or optimization of the NORs and / or optimization of the LOL. The inversely designed and / or optimized NORs and the optimized LOL collectively define learnable mapping functions between input lights and output lights of the NAOMLS to meet target objectives for target tasks. In some embodiments, the NORs are indirectly and inversely designed to meet inversely designed objectives in order to be integrated with the NAOMLS so that the NAOMLS can function properly to meet target objectives for target tasks. In some embodiments, the NORs are integrated directly with the NAOMLS and inversely designed and / or optimized with the LOL to directly meet target objectives for target tasks.

The invention provides an SAR satellite scanning mode task planning method and system for the maximum coverage rate of multiple areas, and the method comprises the steps: obtaining the geographic information, satellite load parameters and orbit information of a target area, and enabling the load parameters to comprise a continuous wave position set in a scanning mode; the population of the swarm intelligent optimization algorithm is initialized, individuals represent a task planning scheme, and individual parameters comprise a beam position set and task timing information; iteratively updating the population until a preset iteration termination condition is met, and seeking an optimal task planning scheme; and after iteration is finished, outputting an optimal planning scheme. The method effectively solves the problems that in the prior art, a task planning method for an SAR satellite scanning mode lacks, and an existing method is insufficient in the aspect of multi-target area coverage rate.

The invention discloses a frequency domain ground penetrating radar transmitting source coding and receiving signal synthesis method and system. The method comprises the following steps: constructing a frequency domain coding continuous wave ground penetrating radar transmitting signal by extracting amplitude and phase information of multiple frequency points of a time domain ultra-wideband transmitting pulse; adopting a fast forward modeling method based on impulse response to realize forward modeling of a coding source emission signal of the typical geoelectric model; in-phase components and orthogonal components of all frequency points are extracted, frequency responses are synthesized into responses of quasi-time-domain transmitted pulses through an inverse Fourier transform method, the high resolution equal to that of time-domain ultra-wideband transmitted signals is obtained, and higher anti-noise performance is achieved. According to the invention, the amplitude phase coding continuous wave transmitting signal is adopted, so that the frequency spectrum shaping of the quasi-time domain pulse of the transmitting frequency spectrum is realized, the resolving power of the synthetic signal is improved, and a theoretical basis is laid for signal synthesis of frequency domain ground penetrating radar hardware design.

Disclosed herein is an optical frequency comb generator for a distributed acoustic anomaly detection system. The system can include a continuous wave frequency modulated laser source configured to generate a laser signal. The system can include an acousto-optical modulator configured to modulate the laser signal by altering an amplitude and / or frequency of the laser signal based on an RF drive signal applied to the AOM, and to output an optical pulse with multiple frequency sidebands based on the modulation. The output can form an optical frequency comb usable detecting and locating acoustic anomalies within a structure under observation.

The invention discloses a control method and equipment of a laser perforation system and a storage medium, and relates to the technical field of automatic system control. The method comprises the following steps: determining initial laser parameters according to the type and thickness of a to-be-processed workpiece; then, a pre-punching instruction is generated according to the initial laser parameters, and the pre-punching instruction is sent to a laser module so as to control the laser module to emit continuous wave laser for pre-punching to form a molten pool; when the state parameters of the molten pool meet switching conditions, pulse laser parameters are determined according to the state parameters of the molten pool; and then, generating a pulse laser instruction according to the pulse laser parameter, and sending the pulse laser instruction to the laser module to control the laser module to emit pulse laser to continue perforation. According to the method, the continuous wave laser is used for pre-perforating to form the molten pool, then the state of the molten pool is monitored, the molten pool is switched into pulse laser, pulse laser parameters are determined according to the state parameters of the molten pool, materials are accurately removed on the basis of the molten pool, and the perforating quality is improved.

Disclosed are systems and techniques for wireless joint communications and sensing. For example, a network device can receive, from a network entity, at least one configuration signal indicating at least one configuration comprising a resource for a physical uplink control channel (PUCCH) and for sensing. The network device can output, for transmission to the network entity, the PUCCH based on the at least one configuration comprising the resource. The network device can transmit a sensing signal based on the at least one configuration comprising the resource.

The invention provides a frequency modulated continuous wave laser radar-based target identification method and a laser radar system, which can be applied to the technical field of laser radars. The method comprises the following steps: acquiring an interference beat frequency signal after polarization orthogonal demodulation; performing signal demodulation on the electric signal of the interference beat frequency signal to obtain a target detection feature; performing feature matching on the target detection features and a typical target polarization feature library to obtain a feature matching result; and under the condition that the feature matching result represents that the target feature similarity meets a first threshold condition, performing identification processing on the target detection features based on an air intrusion target identification model to obtain a target type identification result.

The photonic integrated chip comprises a substrate, a demultiplexer and a light guide assembly, and the light guide assembly and the demultiplexer are integrated on the substrate; the light guide assembly comprises a first light splitting coupler, a second light splitting coupler and a frequency mixer, and the first light splitting coupler is in optical communication connection with the output end of a corresponding channel of the demultiplexer so as to allow the demultiplexer to transmit an optical signal to the first light splitting coupler; the first light splitting coupler is used for splitting a received optical signal into local oscillation light and signal light, and the first light splitting coupler is in optical communication connection with the second light splitting coupler and the frequency mixer so as to allow the first light splitting coupler to transmit the local oscillation light to the frequency mixer and transmit the signal light to the second light splitting coupler; the second light splitting coupler is used for transmitting the signal light to a detection object and receiving echo signal light fed back by the detection object, and the second light splitting coupler is in optical communication connection with the frequency mixer so as to allow the second light splitting coupler to transmit the echo signal light to the frequency mixer.

The invention provides a target positioning method and system based on a distributed networking radar system, and belongs to the technical field of radars, and the method comprises the steps: controlling a plurality of radar nodes to transmit stepping linear frequency modulation continuous wave pulse signals, and collecting target echoes; carrying out band-pass filtering, pulse compression and fast time synchronization processing on the echoes, and generating interference-free data through a moving target extraction algorithm; realizing cross-node clock synchronization based on a moving target behavior cognition model and a template matching algorithm; constructing a multi-node distance estimation equation set, generating an accurate distance value through calibration broadband synthesis and FFT, and determining a target three-dimensional coordinate; and generating a motion track and speed prediction through Kalman filtering based on the target position sequence. The system comprises a signal emission and acquisition module, a signal processing module, a clock synchronization module, a distance estimation and coordinate fusion module and a trajectory prediction module. The method supports multi-target tracking, improves positioning precision and time synchronization precision, has few errors, and is compatible with any node deployment form.

An optical comb generator receives light from at least two continuous wave laser sources, produces a different frequency comb from each laser source, and produces an output that it the simultaneous combination of the different frequency combs. The different frequency combs span different frequency bands, but at least partially overlap in frequency with an adjacent comb in a region of overlap. A spectral filter produces a filtered output that has at least one pair of tones from the region of overlap, the pair of tones comprising one tone from each of two adjacent combs. Feedback control based on the filtered output is applied to adjust the light entering the comb generator such that the frequencies and phases of the pair of tones from the region of overlap are aligned. In this way, the multiple different overlapping combs are stitched together to form a single seamless comb spanning a broader frequency range.

The invention discloses a terahertz continuous wave wind power blade defect imaging method based on an unmanned aerial vehicle platform, relates to the technical field of blade defect imaging, and solves the problems that in the prior art, when a crawling robot serves as a contact type mobile platform to detect a wind power blade, the process is tedious and time-consuming, and safety risks exist. According to the method, an efficient and flexible non-contact detection mode is provided, the unmanned aerial vehicle is adopted as an aerial autonomous bearing platform, contact dependence on the surface of the blade is overcome, rapid deployment, long-distance maneuvering and flexible arrival of detection equipment are achieved, and the detection operation efficiency and safety of the high-altitude and in-service wind power blade are greatly improved; the invention further provides a split type terahertz transmission imaging method capable of being integrated with an unmanned aerial vehicle platform, visual and high-resolution imaging of bubbles, layering and other defects in the blade is achieved by means of the penetrating characteristic of terahertz waves to a composite material, and the defect that in the prior art, the internal defect detection capacity is insufficient is overcome.

A continuous-wave perovskite polariton laser device, including an optical microcavity, a spacer layer, and a gain medium. The gain medium is a perovskite material or a composite material containing perovskite, in a form of thin film, microcrystal, phosphor, nanocrystal, quantum dot, or single crystal. The perovskite gain medium is prepared by solution process or vacuum deposition technique, and is combined with an optical resonator. By exploiting the strong interaction between excitons and photons, a steady-state exciton-polariton condensation is formed, enabling the generation of continuous-wave polariton laser emission with a low threshold. The laser device can achieve low-threshold continuous-wave or pulsed lasing emission at room temperature under various light sources pumping or electrical excitation. Its threshold is 1 to 3 orders of magnitude lower than that of conventional semiconductor lasers, with an optimized threshold as low as 0.1 to 1 W / cm2, representing a novel ultralow-power coherent light source technology.

The invention discloses continuous wave winding 2D forming equipment for manufacturing a wave winding flat wire stator and a control method, and relates to the technical field of new energy automobile driving wave winding flat wire motor production and manufacturing, and the continuous wave winding 2D forming equipment comprises a linear forming device, a linear conveying device, a linear supporting device and a wave winding 2D forming unit; according to the continuous wave winding 2D forming equipment for manufacturing the wave winding flat wire stator and the control method provided by the invention, a split type mold motion forming technology and a forming synchronous control technology are adopted, so that the difficult problem of a 2D forming process of an enameled wire of a new generation of flat wire motor can be effectively solved; the linear size stability after forming is improved, poor forming is reduced, the blank of the existing production technology is solved, the diversified production requirements of the driving flat wire continuous wave winding motor in the automobile manufacturing industry are met, and great influence and far-reaching significance are achieved.

The invention discloses a gesture recognition method and system based on an active acoustic sensing field, and the method comprises the steps: transmitting a frequency modulation continuous wave through a loudspeaker on head-mounted equipment, and receiving an echo signal reflected by the hand of a wearer through a microphone on the head-mounted equipment; performing frequency mixing, low-pass filtering and analog-to-digital conversion on the echo signal to obtain a digital baseband signal; performing range correction and noise reduction processing on the digital baseband signal to obtain a hand echo signal; inputting a hand echo signal into the multi-scale time sequence encoder, and capturing long time sequence dependence to obtain multi-scale spatial-temporal characteristics; performing trajectory tracking on the multi-scale spatial-temporal features by the hand key point regression branches to obtain hand key point features; inputting the hand key point features and the multi-scale spatial-temporal features into the gesture recognition branch to obtain a gesture recognition result; according to the method, multipath interference and spatial fuzziness in the acoustic sensing process can be overcome, and high-precision and fine-grained gesture recognition is realized.

The invention relates to the technical field of leakage detection, in particular to a drainage pipe network leakage area AI identification method and system, and the method comprises the following steps: collecting sound pressure changes through an acoustic collection device, extracting candidate leakage sections, collecting images through an inspection robot, screening training samples, analyzing brightness and profile changes, adjusting the training weight, and identifying the leakage position. And calculating a boundary coincidence area ratio, and adjusting model parameters in combination with a pipe section material. According to the method, leakage candidate sections are compared and screened based on continuous fluctuation of a sound pressure multi-frequency channel, the problem of frequent occurrence of misrecognition under noise interference is avoided, a complexity index is constructed by combining a texture direction and a span in an image, and sample screening is performed; the gray-scale curved surface constructed in the non-abnormal area in the image is compared with the profile trend of the abnormal area to identify the abnormal structure, the extraction capability of irregular leakage features is enhanced, the leakage boundary and material coding data are superposed to evaluate the identification interference degree of the mixed section, and the adaptability and stability of model parameters under different materials are guaranteed.

The invention discloses a surface plasmon resonance imaging system for expanding a dynamic range through a multi-mode optical path, and relates to the technical field of microscopic imaging, a laser outputs a monochromatic and linearly polarized continuous wave beam, a first dynamic beam deflection device performs dynamic angle deflection adjustment on the continuous wave beam, a prism is used for providing a total reflection interface, and a second dynamic beam deflection device is used for performing dynamic angle deflection adjustment on the continuous wave beam. Exciting an evanescent wave; a surface plasma resonance effect is generated through interaction of the SPR detection chip and evanescent waves, and sample characteristics are detected; the flow cell provides a sample flow channel, so that a sample is in full contact with the surface of the SPR detection chip; the second dynamic light beam deflection device cooperatively adjusts the propagation direction of reflected light on the surface of the SPR detection chip, and the imaging detection device captures a high-spatial-resolution SPR image formed by the reflected light and transmits the image to the upper computer in real time for processing and analysis. According to the invention, the change of the resonance angle can be tracked in real time, and high-sensitivity and high-resolution monitoring of the dynamic process of biomolecule interaction is realized.

The invention discloses a millimeter wave radar health monitoring method and system based on wearable equipment, and relates to the technical field of non-contact physiological signal monitoring, the specific steps are as follows: low-frequency life signals of a monitored object are collected based on frequency modulation continuous waves emitted by a radar system, and the low-frequency life signals are time sequence signals of multiple channels; performing wavelet packet decomposition and adaptive filtering on the low-frequency life signal to obtain a filtered signal; and inputting the filtered signal into a trained feature extraction and separation model, carrying out feature extraction and evaluation, and outputting a heartbeat signal and a respiration signal. According to the method, a strong anti-interference preprocessing process is constructed by fusing wavelet packet dynamic decomposition and a sub-band energy entropy threshold method and combining an NLMS adaptive filtering technology, motion artifacts and environmental noise can be effectively stripped, the signal-to-noise ratio of original millimeter wave radar signals is increased, and the anti-interference performance of the millimeter wave radar signals is improved. And a solid foundation is laid for subsequent accurate extraction of weak vital sign signals (respiration and heart rate).

The invention relates to the technical field of laser radar detection, in particular to a frequency-modulated continuous wave laser radar high-precision distance measurement method, which comprises the following steps of: 1, firstly, performing noise suppression by using an improved FTRLS (Fast Transverse Recursive Least Squares) adaptive filtering algorithm aiming at a low signal-to-noise ratio signal; 2, adjusting the added limitation and filter parameters, iterating the optimal parameters, and applying the optimal effect to subsequent spectrum correction; 3, windowing the denoised signal, and carrying out FFT (Fast Fourier Transform) to obtain a frequency spectrum of the signal; and 4, smoothing the signal by using a Butterworth filter, suppressing a side lobe of a frequency spectrum due to the characteristics of the filter, and highlighting the energy of a main lobe of the signal and the position of a spectrum peak. According to the method, a redundancy feedback-dynamic restart mechanism is applied to an adaptive filtering algorithm RLS, the FTRLS algorithm which is added with a transverse filter and leads to reduction of denoising precision is greatly improved, numerical divergence of the FTRLS algorithm is inhibited by using a regularization factor, and the signal-to-noise ratio is improved.

Certain aspects of the present disclosure provide techniques for generating and processing a frequency multiplexed continuous wave (FMCW) based synchronization signal (SS). According to certain aspects, a method for wireless communication at a wireless node, comprising obtaining a synchronization signal comprising a first frequency modulated continuous waveform signal associated with a frequency that increases in time for a duration according to a first slope and a second FMCW signal that overlaps with the first FMCW signal, wherein the second FMCW signal is associated with a frequency that decreases in time for the duration according to a second slope that corresponds to a negative of the first slope; and performing frequency offset estimation based on the first and second FMCW signals.

The invention provides a time-sharing multi-channel power distribution system and a control method thereof, and the system comprises a microwave excitation source which is used for generating a continuous wave radio frequency signal; the common end of the multi-channel radio frequency switch is connected with the output end of the microwave excitation source, and the multi-channel radio frequency switch is used for switching a radio frequency signal to any one of a plurality of output channels of the multi-channel radio frequency switch in a time-sharing manner; the control module is electrically connected with the control end of the multi-channel radio frequency switch, and the control module is used for outputting a control signal according to a preset time sequence so as to drive the multi-channel radio frequency switch to be switched among different output channels; the directional protection module is connected between the microwave excitation source and the multi-channel radio frequency switch and is used for guiding reflection power from an output channel to a matched absorption load, so that the inherent problem of power division attenuation of a traditional power divider is solved; therefore, each output channel can obtain almost all original input power in the working gap, thereby greatly improving the power utilization rate and the transmission efficiency.

A low-cost lightweight single-bit multiplexing array radar signal processing method and system. The method comprises: on the basis of a radio frequency multiplexer, acquiring an array echo signal, and preprocessing the array echo signal to obtain a first zero-intermediate-frequency signal and a second zero-intermediate-frequency signal (S100); performing single-bit synchronous sampling on the first zero-intermediate-frequency signal and the second zero-intermediate-frequency signal to obtain symbol data (S200); and on the basis of the symbol data, estimating an intermediate parameter, and on the basis of the estimation result of the intermediate parameter, calculating target information (S300). The problem of a traditional frequency-modulated continuous wave array radar using a plurality of receivers and a multi-bit analog-to-digital converter to acquire echo signals from a plurality of antennas, resulting in a complex hardware system, a large size, a heavy load and high power consumption, thus limiting the application of the radar in a low-cost and small-payload unmanned system is solved.

To provide an optical fiber light source having high spectral wavelength flexibility and enabling incoherent continuous-wave output in a single transverse mode.SOLUTION: An optical fiber light source has: an optical fiber having a first end, a second end, and a tapered part positioned between the first and second ends, which is a single mode fiber; a wavelength conversion part; a light source for exciting the wavelength conversion part; and a support part. The first end outputs radiant light emitted from the excited wavelength conversion part. The tapered part includes: a constricted part; a first tapered region in which a diameter gradually decreases from the second end side toward the constricted part; and a second tapered region in which a diameter gradually increases from the constricted part toward the first end side. The constricted part has a diameter smaller than those of the first and second ends, and has a size of the wavelength or less of the radiant light. The wavelength conversion part is composed of liquid or gas and is disposed so as to surround at least an outer periphery of the constricted part of the tapered part. The light source simultaneously excites the outer peripheral portion surrounding the wavelength conversion part.SELECTED DRAWING: Figure 2

The invention provides a laser radar, a detection method thereof and a transmitting and receiving device, and the transmitting and receiving device comprises a light splitting modulation unit which carries out the light splitting modulation of original light, so as to form a detection light signal group and a local oscillation light signal group; the coherent unit is suitable for receiving and coupling the echo optical signal group and the local oscillation optical signal group to form a coherent optical signal group, and the coherent optical signal group comprises a plurality of coherent optical signals in time division. Different coherent optical signals in the coherent optical signal group have preset time delay, so that in the process of processing the coherent optical signal group, interference signals can be further eliminated by using the preset time delay, thereby achieving the purpose of improving the anti-interference capability, especially the anti-interference capability in a microwave frequency band, of the laser radar formed by the laser radar, and improving the anti-interference capability of the laser radar in the microwave frequency band. Full-spectrum anti-interference of the frequency-modulated continuous wave laser radar can be realized, and popularization of the frequency-modulated continuous wave laser radar can be further promoted.

According to an aspect of the present inventive concept there is provided a laser system for generating a frequency modulated continuous wave, FMCW, light signal, the system comprising: a tunable laser for generating the FMCW light signal; an optical measurement unit configured to receive a portion of the FMCW light signal, and to output, via an optical hybrid coupler, at least two angle diversity signals based on a difference between a first and second signal formed by splitting the portion of the FMCW light signal wherein the second signal is delayed relative to the first signal, wherein a pair of signals of the at least two angle diversity signals have a fixed phase shift relative to each other; and a control unit configured to: receive the at least two angle diversity signals, estimate, based on the at least two angle diversity signals, a compensation needed for adjusting a non-linearity of a frequency chirp of the tunable laser, and output a corresponding control signal to the tunable laser, wherein the control signal is configured to improve a linearity of the frequency chirp.