Systems and methods for improved laser mode hop detection for hard disk drive applications

Abstract

The present disclosure provides systems and methods for improved laser mode hop detection for hard disk drive applications. A solution for providing laser mode hop detection in a hard disk drive can include a first circuit for providing a signal having a stepped voltage, the amplitude of which can be adjusted according to a first control signal. The solution can include a second circuit that delays the signal for a period of time to produce a delayed signal, the period of time being adjustable according to a second control signal. The solution can include a filter for receiving the delayed signal as an input and providing an offset signal corresponding to a frequency response of a sensor as an output. The system can subtract the offset signal from a sensor signal of the sensor to provide an output.

Description

[0001] Cross-referencing of related patent applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 506,529, filed June 6, 2023, the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0003] This disclosure generally relates to systems and methods for controlling and operating hard disk drives (HDDs), including (but not limited to) laser mode transition detection in HDDs. Background Technology

[0004] Hard disk drives (HDDs) are used to store data in computers and other electronic devices. HDDs can contain various designs and components, such as magnetic platters on which data can be written or read, and actuator arms for reading or writing data. HDDs can be operated using lasers. Summary of the Invention

[0005] Heat-assisted magnetic recording (HAMR) is an energy-assisted technology in hard disk drives (HDDs) where a laser is used to heat localized areas of a highly coercive medium for more efficient data recording. The consistency and size of the area heated by the laser on the disk surface are important for maximizing recording density, as they define tracks and bit pitch. The area on the disk surface heated by the laser for data recording is referred to as the "spot size." During data recording, the HDD's laser can experience mode jumps, which may involve sudden shifts in the laser's operating mode or characteristics, resulting in changes in laser output properties, such as the laser's output frequency or power. These sudden changes caused by mode jumps can lead to abrupt changes in the spot size, potentially imprinting a phase shift onto the recorded data beyond the HDD's read channel recovery capabilities, resulting in data corruption during the mode jump. In such cases, the system can identify mode jumps that have exceeded a previously determined permissible threshold and rewrite the corrupted sectors before clearing the data buffer. If this correction is not performed before clearing the data buffer, the data may become unretrievable, making adequate mode transition detection an important feature of HAMR systems.

[0006] When an HDD transitions from a read operation (reading data from the HDD) to a write operation (writing data to the HDD), the laser power output can increase from a lower laser power output (e.g., during a read operation) to a higher laser power output (during a write operation). As a result, for a specific period after the read / write (R2W) transition (e.g., tens or hundreds of nanoseconds after the transition), a power monitoring device, for example, can output a signal resembling a mode transition to the HDD system's preamplifier, making it difficult to determine whether a true mode transition has occurred or whether the signal is due to the R2W transition. Consequently, reliably detecting a true mode transition event of the laser can be challenging when it coincides with a time period immediately following the R2W mode transition (e.g., approximately 1 to 2 microseconds). This solution overcomes this challenge by allowing more reliable and accurate transition detection in the time immediately following the R2W mode transition. It provides circuitry that subtracts a signal matching the detector's frequency response from the laser detector signal, enabling reliable detection of the mode transition signal throughout the entire duration of HDD write mode operation, including the time interval immediately following the R2W transition.

[0007] One aspect relates to a system. The system may include a first circuit system for generating a first signal representing a transition from a read operation to a write operation on the storage device, and delaying the first signal according to a first time period. The system may include a filter coupled to the first circuit system to filter out frequencies above a threshold from the delayed first signal, and outputting a second signal according to a second time period of the filter's frequency response. The system may include a second circuit system for receiving a measurement of the optical output of the laser of the storage device undergoing the transition and having a mode hopping of the laser, the frequency response of the second circuit system being indicated by the measurement and corresponding to the frequency response of the filter. The second circuit system may be configured to subtract the second signal from the measurement to output a third signal identifying the occurrence of the mode hopping of the laser.

[0008] The first signal may comprise an increase from a first voltage corresponding to the read operation to a second voltage corresponding to the write operation, wherein the first time period corresponds to the start time of the transition. The difference between the first voltage and the second voltage is typically in the range of 1mV to 1000mV. The value may be adjusted according to a first control signal used to control the first circuit system.

[0009] The system may include a delay circuit for the first circuit system to align the timing of the transition indicated by the second signal with the timing of the transition indicated by the measurement using the first time period. The first time period may be adjusted to a duration value typically between 5 ns and 10 μs, according to a second control signal for controlling the delay circuit of the first circuit system.

[0010] The system may include a resistor for the filter. The resistor may be coupled to the output of the delay circuit of the first circuit system. The system may include a capacitor for the filter. The capacitor may have a first contact coupled to the resistor and a second contact coupled to ground. The resistor and the capacitor may be configured to match the frequency response of the filter to match the frequency response of the second circuit system.

[0011] The system may include a sensor of the second circuit system. The sensor may be configured to provide a signal corresponding to the optical output of the laser. The system may include an amplifier circuit of the second circuit system to amplify the sensor signal and generate the measurement. The sensor may be a photoelectric transducer, such as a calorimeter or photodetector. The amplifier circuit may include a differential amplifier configured to subtract the second signal from the measurement to output the third signal.

[0012] The second time period may correspond to the duration during which the measurement from the sensor of the second circuit system transitions from a first level corresponding to the read operation to a second level corresponding to the write operation. The measurement may include a first portion corresponding to a disturbance in the optical output of the laser caused by an increase in power input to the laser in response to the transition, and a second portion corresponding to a mode transition of the laser occurring during or after the disturbance.

[0013] The second circuitry can be configured to subtract the second signal from the measurement to eliminate the first portion of the measurement from the third signal that identifies the occurrence of the mode transition of the laser. The mode transition of the laser can occur either after the start of the transition or at approximately the start of the transition.

[0014] The third signal may be input to a third circuit system. The third circuit system includes at least a bandpass filter, an amplifier, and a peak detector, the peak detector being used to detect the occurrence of the mode transition event in response to a peak value in a signal output from the amplifier and filtered by the bandpass filter exceeding a threshold value of the peak detector.

[0015] One aspect relates to a method. The method may include a first circuit system that generates a first signal representing a transition from a read operation to a write operation on the storage device. The method may include the first circuitry delaying the first signal according to a first time period. The method may include a filter coupled to the first circuit system that filters out frequencies above a threshold from the delayed first signal to output a second signal according to a second time period of the filter's frequency response. The method may include a second circuit system that receives a measurement of the optical output of the laser of the storage device undergoing the transition and exhibiting a mode hopping of the laser. The measurement may indicate a frequency response of the second circuit system corresponding to the frequency response of the filter. The second circuit system may subtract the second signal from the measurement to output a third signal identifying the occurrence of the mode hopping of the laser.

[0016] The first signal may comprise an increase from a first voltage corresponding to the read operation to a second voltage corresponding to the write operation, and the first time period corresponds to the start time of the transition. The difference between the first voltage and the second voltage is typically between 1 mV and 1000 mV. This value can be adjusted using a first control signal for controlling the first circuit system.

[0017] The method may include a delay circuit in the first circuit system, the delay circuit using a first time period to align the time of the transition indicated by the second signal with the time of the transition indicated by the measurement. The first time period may be a value in the range of 5 nanoseconds and 10 microseconds. The value may be adjusted according to a second control signal used to control the delay circuit of the first circuit system.

[0018] The method may include a resistor and a capacitor of the filter, configured to match the frequency response of the filter to the frequency response of the second circuit system. The resistor may be coupled to the output of the delay circuit of the first circuit system, and the capacitor may include a first contact coupled to the resistor and a second contact coupled to ground. The method may include providing a signal from the sensor corresponding to the optical output of the laser via a sensor of the second circuit system. The method may include an amplification circuit of the second circuit system that amplifies the sensor signal and generates the measurement. The sensor may be either a calorimeter or a photodetector, and the amplification circuit may include a differential amplifier configured to subtract the second signal from the measurement to output the third signal.

[0019] The second time period may correspond to the duration during which the measurement from the sensor of the second circuit system transitions from a first level corresponding to the read operation to a second level corresponding to the write operation. The measurement may include a first portion corresponding to a disturbance in the optical output of the laser caused by an increase in power input to the laser in response to the transition, and a second portion corresponding to a mode transition of the laser occurring during or after the disturbance.

[0020] The method may include a second circuit system that subtracts the second signal from the measurement to eliminate a first portion of the measurement that identifies the occurrence of the mode transition of the laser from the third signal. The mode transition of the laser can occur at any time after the start of the transition.

[0021] One aspect relates to a storage device system. The storage device system may include a voltage generator for generating a first signal representing a transition from a read operation to a write operation of the storage device. The storage device system may include a delay circuit for delaying the first signal according to a first time period. The storage device system may include a filter coupled to the delay circuit to filter out frequencies above a threshold from the delayed first signal and output a second signal according to a second time period of the frequency response of the filter. The storage device system may include an amplifier for receiving the second signal from the filter and receiving a measurement from a sensor of the optical output of the laser of the storage device undergoing the transition and having a mode transition of the laser. The measurement may indicate the frequency response of the second circuit system matching the frequency response of the filter. The storage device system may include the amplifier for subtracting the second signal from the measurement to output a third signal identifying the occurrence of the mode transition of the laser. Attached Figure Description

[0022] These and other aspects and features of this embodiment will become apparent to those skilled in the art when reading the following description of specific embodiments in conjunction with the accompanying drawings.

[0023] Figure 1 This is an example block diagram of a mode transition detection system that uses a transducer sensor to detect mode transitions of a laser (e.g., a laser diode) in a hard disk drive (HDD).

[0024] Figure 2 It is an example waveform of the operation or result of the mode transition detection system.

[0025] Figure 3This is an example waveform of a read / write (R2W) transition in a mode transition detection system.

[0026] Figure 4 It is an example of a waveform representing the operation or result of a mode transition detection system.

[0027] Figure 5 It is an example of a waveform representing the operation or result of a mode transition detection system.

[0028] Figure 6 This is an example block diagram of a mode transition detection system using a transducer sensor, which uses a preamplifier circuit to model the sensor response in the mode transition detection system.

[0029] Figures 7 to 12 This is an example of a waveform representing the operation or result of the mode transition detection system in this solution.

[0030] Figures 13 to 17 This is an instance of the table or operation result of the mode change detection system in this solution.

[0031] Figure 18 An example flowchart illustrating a method for providing mode transition detection according to an embodiment of this solution. Detailed Implementation

[0032] This embodiment will now be described in detail with reference to the accompanying drawings, which are provided as illustrative examples of the embodiments to enable those skilled in the art to practice embodiments and alternatives that are obvious to them. The drawings and examples below are not intended to limit the scope of this embodiment to a single embodiment, but other embodiments are possible by interchangeing some or all of the elements described or illustrated, or those that are obvious to those skilled in the art. Certain elements of this embodiment may be implemented partially or entirely using known components, and only those portions of such known components necessary for understanding this embodiment will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure this embodiment. The embodiments described in the illustrative context of the embodiments should not be limited thereto. For example, embodiments described as implemented in hardware or software should not be limited to such implementations, but may include embodiments implemented in hardware, software, or any combination of software and hardware, as will be obvious to those skilled in the art, unless otherwise specified herein. In this specification, embodiments showing a single component should not be considered limiting; rather, unless expressly stated otherwise herein, this disclosure is intended to cover other embodiments that include a plurality of identical components, and vice versa. Furthermore, the applicant does not wish for any terminology in the specification or claims to be given an uncommon or special meaning unless explicitly stated so. Moreover, this embodiment covers current and future known equivalents of known components mentioned herein by way of illustration.

[0033] While HAMR systems can incorporate various types of power monitoring transducers or sensors, such as photodiodes and calorimeters, this technical solution is applicable to any power monitoring device. Although a calorimeter can be used in the illustrated examples, any other monitoring transducer can be used in the system solution, including any resistive temperature detector, capacitive sensor, Hall effect sensor, piezoelectric sensor, magnetic sensor, semiconductor photodetector, or any other sensor or detector. Furthermore, mode transitions may not have a preferred polarity, and therefore, such events can lead to an increase or decrease in laser power. While the illustrated examples may discuss mode transitions with positive polarity, it should be understood that the solution is similarly applicable to any polarity.

[0034] Because the technical solution presented herein is adaptable to the characteristics of any power monitoring device, it addresses the problem of timely laser transition detection (or any other electrical or electronic time-constrained detection) for a wide range of applications, including both fast and time-constrained detection. The solution improves power monitor sensitivity and frequency response across a range of amplitude, delay, and frequency response tuning parameters. HAMR systems can utilize power changes between read and write operations (e.g., read and write modes), and the solution can use this to provide improvements for HAMR HDD devices and related applications. The solution provides improved and accurate mode transition detection for a significant portion of write events, including coverage of the entire write event or the time period during which write operations occur.

[0035] Figure 1 Example of a block diagram illustrating a mode transition detection system 100. The mode transition detection system 100 may include circuitry or a circuit system that includes and utilizes a transducer sensor 105 to measure the optical output 155 from a laser 150 and provide sensor measurements 125 to a filter 130. The filter 130 may filter the received sensor measurements 125 and provide its output to a peak detector, which may utilize a threshold 160 to provide a mode transition detection signal 140.

[0036] Laser 150 may include any laser or laser diode that emits a focused optical output 155 (e.g., light) onto the surface of the magnetic recording medium of the HDD to create a locally heated region. The optical output 155 of laser 150 may include any emitted light or electromagnetic radiation generated by laser 150, which may be characterized by specific properties of laser 150, such as the wavelength, intensity, and coherence of the emitted electromagnetic radiation. Because heat reduces the coercivity of the medium, data can be written to the HDD more easily, allowing for higher recording densities and improved storage capacity. Laser 150 may operate in a power range between one or more milliwatts and one or more watts. Optical output 155 may include any optical output range between 400 nm and 10 μm, including, for example, the 800 to 1000 nm range.

[0037] Sensor 105 may be placed or positioned near laser 150 or its optical output 155 to monitor a small portion of the optical output 155. Sensor 105 may include any sensor for measuring the optical output 155 from laser 150. Sensor 105 may be any device that converts one type of energy into another, including, for example, a photoelectric transducer (e.g., a calorimeter or photodetector). Sensor 105 may include or be characterized by a resistor RSeminor 120, which may be inherent in sensor 105. Since sensor 105 can be driven by a DC bias current ISeminor 110, voltage VSeminor 115 (e.g., voltage across sensor 105) can be detected, measured, and monitored. When sensor 105 (e.g., a calorimeter or photodetector) is exposed to optical output 115 (e.g., a change in optical output due to a change in laser power input), monitoring ISeminor 110 and / or VSeminor 115 allows this technical solution to react. For example, a power disturbance can cause a disturbance in RSeminor 120 and can affect the VSeminor voltage, resulting in a change in sensor measurement 125.

[0038] The VSeminor 115 voltage of sensor 105, which reflects any change in the optical output 155 signal, can be input to or pass through filter 130 as sensor measurement 125. In some instances, depending on the type of sensor 105, the Isensor 110 current can be input to filter 130 as sensor measurement 125. Filter 130 receiving sensor measurement 125 may include a bandpass filter and may include a gain circuitry with programmable gain for amplifying or enhancing sensor measurement 125. Filter 130 may have corner frequencies (e.g., frequency poles) to remove DC signals or content (which may be large) and to remove any high-frequency signals or noise. The output of filter 130 (e.g., a bandpass filter) can be fed to or passed to peak detection circuitry or peak detector 135. Peak detector 135 may include and utilize a programmable threshold 150 to detect whether the filtered sensor measurement contains a peak indicating the occurrence of a mode-jump event. A mode-hopping event may include any rapid and unexpected change (e.g., a disturbance) in the operating mode or characteristics of the laser 150, causing a sudden shift in the laser's output properties (e.g., frequency, mode, or power). The programmable threshold 160 may include or be coupled to circuitry capable of sending a digital output to a fault monitoring and control circuitry system. A peak detector 135 may detect mode-hopping events that exceed the programmable threshold at either polarity (positive or negative edge). When the filtered signal exceeds the threshold 160, the peak detector 135 may provide or output a mode-hopping detection signal 140 indicating that a mode-hopping event has been detected. This, in turn, allows the HDD system to use circuitry or functionality to correct any corrupted data or to take corrective action with the laser 150.

[0039] Figure 2 exhibit Figure 1Example 200 shows a waveform representing the operation or result of system 100. In this example, a mode transition may occur at time = 20 µs. The mode transition event can be indicated by plotted line 210, which shows a step function that instantly increases from a lower voltage reading of 100 mV to a higher voltage reading of 105 mV. If the calorimeter has a very high bandwidth, the voltage across it will increase almost instantaneously at that time (e.g., as shown by plotted waveform 210). However, since the calorimeter may have a bandwidth of only 1 MHz, it will respond with a delay of approximately 1 microsecond (µs). Therefore, the calorimeter will take approximately 1 µs to fully respond to such a mode transition event, as indicated by plotted waveform 205. If the signal is then amplified or gained by 50 V / V (e.g., via an amplifier) ​​and passed through a 2 kHz high-pass filter 130, the result can be expressed by plotted waveform 220 (e.g., “Vp_PkDet”). If the user sets the mode transition detection threshold 160 to 200mV based on the input of the peak detector 135 (e.g., as shown by plotted waveform 225), then a fault condition can be reported (e.g., plotted waveform 215) as long as waveform 220 is greater than waveform 225 (e.g., Vp_PkDet > Vn_PkDet). This digital signal, where "1" represents logic high and "0" represents logic low, can then be latched and reported to the system controller, enabling a rewrite to be initiated (e.g., to repair any corrupted data caused by the mode transition event).

[0040] As shown in Example 200, system 100 may require 1 µs to detect a mode-jumping event, and this amount of time can represent a large portion of the recording duration. This is a consequence of the low bandwidth of sensor 105. Low-bandwidth sensor 105 may rely on a low high-pass corner (HPC) to achieve a usable signal-to-noise ratio (SNR). Furthermore, an additional consequence of low HPC is that peak detector input may require >200 µs to return to its steady-state value. This poses a challenge to accurately detecting mode-jumping events following the first one.

[0041] Read operations in an HDD may include the process of retrieving data from a storage medium, such as accessing and reading information stored on a disk using a read / write head. Write operations in an HDD may include the process of storing data onto a magnetic storage medium by encoding data using a magnetic write head. The technical solution disclosed herein overcomes the challenges of current mode-jump detection systems that use preamplifier circuit solutions to allow the detection of mode-jump events even during the approximate time period of a read / write (R2W) transition.

[0042] Read / write (R2W) transitions can involve any switching of a storage device, such as a hard disk drive (HDD), from a read operation mode to a write operation mode. This can involve changes in the power output of the laser (e.g., from lower power in read mode to higher power in write mode) or changes in other parameters used to enable data recording. For example, when the preamplifier circuit is commanded to enter write mode (e.g., from read mode), the laser power can rapidly increase to achieve the recording threshold. In such R2W transitions, if the laser output power does not increase in time, previously recorded data may be partially erased, resulting in insufficient storage duration (e.g., excessively high laser bias current during read), or no new data may be recorded at all (e.g., excessively low laser bias voltage during write). However, as an artifact of the sudden increase in laser power, the laser may experience a disturbance around the R2W transition, making it difficult to detect the actual mode-change event during the disturbance.

[0043] Figure 3 Example 300 depicts a plotted waveform 305 showing the R2W transition occurring at time = 10µs. During the R2W transition, sensor 105 (e.g., a calorimeter) can output a signal that increases from 50mV (e.g., sensor measurement 125 during HDD read mode operation) to 100mV (e.g., sensor measurement 125 during HDD write mode operation). Sensor 105 can perform this transition from 50mV to 100mV over a 1µs period. This can be in response to commands for additional laser bias current (i.e., power) used by the HDD system for recording data.

[0044] refer to Figure 4 Example 400 illustrates the input and output of peak detector 135 while maintaining a 200mV mode transition detection threshold (e.g., as shown by the dashed line). For example, the system can increase the HPC setting (e.g., increase) of the detection path by several orders of magnitude (e.g., from 2kHz to 20MHz) during the R2W transition to minimize disturbances at the input of peak detector 135. If this is not done (e.g., waveform 405), then erroneous mode transitions of >200µs can be reported (e.g., waveform 405 plotted in the lower right corner). An erroneous mode transition of 200µs can last longer than the entire write sector, providing insufficient mode transition protection during said time period. Since increasing the HPC can attenuate the signal at lower frequencies and achieve faster baseline stabilization, it can be used to “suppress” disturbances. Suppression can also involve other techniques, such as using switches to disconnect, using switches to short-circuit the input of the peak detector, and using cross-coupled differential pairs to reroute / cancel the signal. Figure 4 and 5Techniques that can increase HPC to ~20MHz can be used.

[0045] The 410 waveform illustrates that if the HPC remains high (~20MHz) for a minimum of 450ns after the R2W transition, no error event will be reported due to the bias change. However, in this example, write mode transition detection may be compromised because the residual perturbation remaining after shifting the HPC down to 2kHz at 450ns may be significant (i.e., not far below the 200mV threshold). In this case, the preamplifier may be at risk of overreporting problems via minor mode transition events that were previously determined to be problem-free.

[0046] Furthermore, extending the duration of the ~20MHz HPC suppression interval to 1µs (waveform 415) can effectively suppress the entire bias change event. This may be beneficial for the remainder of the write operation. However, the entire 1µs coverage may be lost, and mode transitions can occur at any time during the write operation, even within the first 1µs. In some cases, the initial 1µs after the R2W transition may be the most likely time for a mode transition event, as this is when the laser's operating point changes (e.g., from a lower power level to a higher power level).

[0047] In some instances, a suppressor (or shield) interval of approximately 1 µs can be used to allow robust and accurate mode transition detection of the remainder of the write (i.e., without error reporting). Figure 5 Example 400 illustrates the use of this shielding interval and plots of mode transition events occurring at 200 ns to write mode (e.g., waveform 505) and at 1 µs to write mode (e.g., waveform 510). In such implementations, events are detected only 1 µs after the R2W transition. Data written where the mode transition occurs at 200 ns may be unrecoverable, and the HDD controller may not be aware of this. Therefore, for a preamplifier designed to provide maximum mode transition detection coverage, individual suppression may be an insufficient solution, while this technical solution provides coverage across the entire write interval.

[0048] Figure 6This describes an example of a system 600 that provides or facilitates improved laser mode-jump detection for the entire operation of an HDD (e.g., within 1µs of a read / write mode transition event). The example system 600 may be described as having a compensated circuitry with a preamplifier matched to the frequency response of sensor 105. The frequency response may include any characteristic behavior of the circuitry, system, or device in response to a varying input frequency. The frequency response may be represented as a plot of amplitude (or gain) versus frequency, showing how the circuitry, device, or system transmits, attenuates, or amplifies signals according to frequencies within a given frequency range.

[0049] Example system 600 may include a voltage generator 605 that provides a generated voltage signal (GVS) 635 (e.g., VComp) input to a delay circuit 610. The delay circuit 610 may provide a configurable or adjustable delay to the GVS 635 provided by the voltage generator 605 and output a delayed voltage signal (DVS) 640. DVS 640 may be input to a filter 615 that may include one or more resistors and capacitors (e.g., a 1 kΩ (1K) resistor R4 and a capacitor C10 with a capacitance C of 1 / (2π*BW_Bolo)), where π is 3.14159 and BW_Bolo is the bandwidth of the signal output from sensor 105. Filter 615 may output a preamplifier signal output (PSO) 645 (e.g., VComp_filt), which may be fed into an amplifier 620 that may also receive sensor measurements 125 (e.g., the V_Bolo signal) from sensor 105. Amplifier 620 can combine these two signals (e.g., subtracting PSO 645 from amplified sensor measurement 125) and generate or output a signal 630 with a mode transition. The signal 630 with a mode transition (e.g., V_Bolo_Comp) can be sent as input to... Figure 1 The signal is filtered in filter 130 and then processed by peak detector 135 to generate mode transition detection signal 140 when a threshold 160 is exceeded.

[0050] exist Figure 6In this embodiment, system 600 may include or correspond to a preamplifier circuit, which may include a voltage generator 605, a delay circuit 610, and a filter 615. The preamplifier circuits (e.g., 605, 610, and 615) may collectively generate a frequency response corresponding to (e.g., correlated, aligned, or matched to) the frequency response of sensor 105. For example, the preamplifier circuits (e.g., 605, 610, and 615) may be matched to the frequency response of sensor 105 and any circuitry and contacts from sensor 105 to amplifier 620. In some aspects, system 600 includes or corresponds to a preamplifier circuit having a reciprocal of the frequency response corresponding to (e.g., correlated, aligned, or matched to) sensor 105 and its circuitry and contacts providing sensor measurement 125 to system 600.

[0051] System 600 may include a voltage generator 605, which may include any combination of hardware and software, devices, or circuitry for generating a voltage. The voltage generator 605 may generate a GVS 635, which is a step voltage output, such as a step voltage between 0mV and 100mV, or any arbitrary amplitude within a range from an external power source. The voltage generator 605 may include or utilize a programmable switching circuitry to adjust the voltage level output and provide a response over a time range of approximately 1 ns, such as 0.1 ns, 0.5 ns, 10 ns, 20 ns, or longer. A voltage regulator 605 may provide or generate an adjustable or programmable amplitude (e.g., a VComp signal) to the GVS 635, which may be output from the voltage generator 605 and fed into a delay circuit 610.

[0052] Delay circuit 610 may include any combination of hardware and software for delaying the GVS 635 signal to provide a configurable, adjustable, or programmable delayed (e.g., time-offset) version of the GVS 635 (referred to as delayed voltage signal (DVS) 650). Delay circuit 610 may include programmable delay elements that provide versions of the input signal that are delayed by a set time amount, such as between 1 ns and 20 μs, for example, any time value up to 500 ns, 1 μs, 3 μs, 5 μs, 10 μs, or 20 μs. Delay circuit 610 may have a resolution for adjusting the time in steps of about 10 to 100 ns, for example, at least 10 ns, 20 ns, 30 ns, 50 ns, 70 ns, or 100 ns. Delay circuit 610 may provide a delayed output version (e.g., VComp_Del) of the input signal that can be input to filter 615.

[0053] Filter 615 may include any filter (e.g., low-pass, band-pass, or high-pass) that can be used to filter the frequency DVS 640 output from delay circuit 610 and input to filter 615. Filter 615 may include a programmable low-pass filter that may have a frequency response matched to the frequency response or characteristics of sensor 105 (e.g., a calorimeter or photodetector for detecting the optical output 155 of laser 150). Filter 615 may have a frequency response matched to the frequency response of sensor 105 and its contact lines, as well as any processing circuitry, such as the connection lines or amplification circuitry that increase the gain of sensor measurement 125 before the combination of amplified sensor measurement 125 and amplified PSO 645. For example, PSO 645 may be subtracted from sensor measurement 125 before or without any gain adjustment to sensor measurement 125 or PSO 645.

[0054] Filter 615 may include one or more frequency poles to adjust its frequency response. Filter 615 may include a single-pole RC filter whose resistor (e.g., R4) and capacitor (e.g., C10) values ​​can be adjusted, modified, or changed to match the frequency response of sensor 105 and its signal path to amplifier 620, where PSO 645 will be subtracted from sensor measurement 125. System 60 may implement the subtraction of a delayed and filtered step voltage from the calorimeter response at the R2W transition.

[0055] This solution may include a feedforward arrangement in which the matched frequency response of sensor 105 (e.g., a calorimeter) can be regenerated in a preamplifier (e.g., voltage generator 605, delay circuit 610, and filter 615) and then subtracted from the actual sensor 105 response. Laser mode-hopping events can manifest as disturbances in optical output 155 and can be readily detected because the volume sensor 105 response due to non-hopping laser power changes (e.g., disturbances in optical output 155 caused by R2W mode transitions) can now be eliminated (e.g., by subtracting PSO 645 from sensor measurement 125). As a result, the residual signal 630 with mode-hopping may not contain residual disturbances due to R2W transitions, leaving only the actual mode-hopping event for system detection.

[0056] For example, if the expected output of sensor 105 is projected to change from 50mV to 100mV during the R2W transition ( Figure 3Therefore, the value of the signal output from voltage generator 605 (e.g., VComp) can be 100-50 = 50mV. The delayed voltage signal 640 (e.g., VComp_Del) can be used to account for propagation delay within the circuit system, since the elimination of the R2W transition can be achieved by the sensor measurement 125 and PSO 645 arriving approximately simultaneously at amplifier 620 and peak detector 135. The output of the compensation circuit (e.g., signal 630 with mode transition, also known as V_Bolo_Comp) can be directly passed to the combined... Figure 1 The filter 130, amplifier, and peak detector 135 are discussed.

[0057] Figure 7 A plot 700 illustrates the performance when amplitude, delay, and filter are matched to the frequency response or characteristics of sensor 105. The preamplifier circuitry (e.g., 605, 610, and 615) can produce a frequency response that matches the frequency response of sensor 105 within acceptable threshold tolerances, such as 0.1%, 0.5%, 1%, 2%, 5%, 10%, or 15% of the signal (which can be evaluated in terms of timing, amplitude, power, voltage, frequency response (e.g., frequency plot) or event detection). In plot 700, because the transient behavior of PSO 645 during the R2W transition (e.g., 710 or VComp_filt) precisely matches the transient behavior of sensor measurement 125 (e.g., 705 or V_Bolo), the signal 630 with mode-hopping (e.g., 715 or V_Bolo_Comp signal) and the input of the high-pass filter (e.g., 720 or Vp_PkDet) remain undisturbed throughout the transition. This can be achieved using the static 2kHz setting of the HPF (i.e., no suppression / shielding interval).

[0058] Figure 8Example plot 800 illustrates the performance and advantages of a compensation circuit (e.g., system 600) when a 5mV mode transition occurs at 200ns (e.g., waveforms 805, 815, 825, and 835) and 1us (e.g., waveforms 810, 820, 830, and 840) in a write event (e.g., after the R2W transition). Both mode transitions can be detected because the expected baseline offset is compensated for and the suppression interval is not activated. The voltage (e.g., V_Bolo_Comp) at waveforms 815 and 820 can increase by 5mV due to the mode transition. Furthermore, the amplified, high-pass filtered version of V_Bolo_Comp (e.g., system 600) at the input of the peak detector (e.g., waveforms 825 and 830, or Vp_PkDet) can have the same transient characteristics for both events. In other words, because it can compensate for system disturbances and the HPF corner can be maintained at its steady-state value (2kHz), mode transition detection is available from the start to the end of the write operation without any spurious activity.

[0059] In one implementation, a technical solution can be implemented when one or more characteristics (e.g., amplitude, propagation delay, and / or frequency) of the baseline transition and compensation signal (e.g., PSO 645) from the preamplifier match or are matched within a predetermined tolerance threshold with characteristics of sensor 105 or sensor measurement 125. For example, PSO 645 may have any combination of signal amplitude, propagation delay (e.g., time characteristics of the signal), and / or frequency (e.g., frequency response or signal output) that matches sensor measurement 125. When PSO 645 can be mapped (e.g., one-to-one) over the entire sensor measurement 125 to match the characteristics of sensor measurement 125 corresponding to signal artifacts or perturbations in the optical output 155 caused by the R2W transition, subtracting PSO 645 from sensor measurement 125 removes all optical perturbations, artifacts, or other characteristics caused by the R2W transition, providing a signal 630 with only mode-jumping events. For example, such mode transition detection events can be seen in waveforms 835 and 840, corresponding to 200ns and 1us events.

[0060] Depending on the manufacturing process of the HDD and its components, for example, in the large-scale production of systems where system variations may exist, the design and / or performance may change. For example, according to the combination Figure 9 , 10 The discussion in section 11 provides the sensitivity for each parameter. For these three graphs, the detection threshold can be set to 200mV, since it can be measured at the signal 630 with mode transition or at the input of the peak detector 135.

[0061] Figure 9The illustration shows plot 900, which shows a tolerance for errors of approximately + / -20% at the filter frequency before reporting an error event. For example, when the error (e.g., at the filter frequency) is -20%, waveform 905 corresponds to the Vp_PkDet signal. For example, when the error (e.g., at the filter frequency) is -10%, waveform 910 corresponds to the Vp_PkDet signal. For example, when the error (e.g., at the filter frequency) is 0%, waveform 915 corresponds to the Vp_PkDet signal. For example, when the error (e.g., at the filter frequency) is +10%, waveform 920 corresponds to the Vp_PkDet signal. For example, when the error (e.g., at the filter frequency) is +20%, waveform 925 corresponds to the Vp_PkDet signal. As shown in plot 900, properly matching the signal and reducing the percentage error can benefit the system output.

[0062] Figure 10 A plot 1000 illustrates the effect of amplitude error on the performance of system 600. For example, plot 1000 may show the degree of amplitude error that system 600 can tolerate (e.g., approximately + / - 20%), because signals exceeding this degree can produce erroneous events (e.g., detection of two polarities). For example, when the error (e.g., in amplitude) is -20%, waveform 1005 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in amplitude) is -10%, waveform 1010 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in amplitude) is 0%, waveform 1015 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in amplitude) is +10%, waveform 1020 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in amplitude) is +20%, waveform 1025 corresponds to the Vp_PkDet signal.

[0063] at last, Figure 11The diagram 1100 illustrates that propagation delay difference can be a sensitive parameter, as an error of 20 ns can lead to an erroneous event. For example, diagram 1100 can show the degree tolerable delay mismatch or error (e.g., approximately + / -20 ns relative to the measured signal) for system 600, since a time mismatch at approximately 20 ns can produce an erroneous event (e.g., in waveform 1125). For example, when the delay error (e.g., time mismatch) is -20 ns, waveform 1105 corresponds to the Vp_PkDet signal. For example, when the error (e.g., time mismatch) is -10 ns, waveform 1110 corresponds to the Vp_PkDet signal. For example, when the error (e.g., time mismatch) is 0 ns, waveform 1115 corresponds to the Vp_PkDet signal. For example, when the error (e.g., time mismatch) is +10 ns, waveform 1120 corresponds to the Vp_PkDet signal. For example, when the error (e.g., time mismatch) is +20 ns, waveform 1125 corresponds to the Vp_PkDet signal. As shown in waveform 1125, the +20 ns time mismatch leads to incorrect mode transition detection, while waveform 1115 shows a flat mode transition curve (e.g., accurately detecting no mode transition event).

[0064] Another aspect of this solution may include an effective and practical calibration solution, algorithm, or technique. Calibration can be used during HDD production to finely tune system 600 to account for any manufacturing variations. For example, the calibration solution can be used to achieve full coverage in mass production (e.g., taking into account product variations of various HDD components or parts). For example, three parameters, such as voltage amplitude, can be calibrated, which may be the first parameter to be calibrated and can be measured before any high-pass filtering. For example, calibration can be initiated by measuring the DC output of sensor 105 (e.g., a calorimeter or photodetector) in both read and write modes of HDD operation. Laser 150 may be turned on (e.g., or assumed to be turned on), and the output of sensor 105 in write mode (e.g., sensor measurement 125) can adequately represent a real write event. To avoid affecting any recorded data, this can be performed when the preamplifier is idle or in standby mode (e.g., stopped on a ramp). At this same measurement point, the user can switch to monitoring the calibration voltage and scanning its control DAC until its output matches the difference (V_Bolo_write - V_Bolo_read) between the previous measurement and the output of sensor 105 (e.g., sensor measurement 125) from read to write. With the calibrated (e.g., optimal) compensated amplitude established, the user can iterate between delay and filter settings to optimize both (e.g., reduce delay, frequency, or amplitude errors). For this stage of calibration, the output of the HPF (i.e., the input to the peak detector) can be the monitoring point.

[0065] Figure 12 The illustration 1200 shows plots of several waveforms (e.g., 1205 to 1230), the first of which may contain the original response (e.g., waveform 1230) at the input (black) of the positive peak detector without compensation. Below waveform 1230, there may be two sets of waveforms, both scanning the filter error from 80% to 120% (e.g., from -20% to +20%). The dashed group of waveforms (e.g., 1205 to 1225) may show the response when the compensated signal (e.g., PSO 645) leads the original signal (e.g., sensor measurement 125) by 20 ns (i.e., -20 ns error). The solid waveforms (e.g., 1235 to 1255) may contain the same filter error scan but without any propagation delay error. As shown in waveform 1245, when there is no propagation delay error (e.g., PSO 645 and sensor measurement 125 are time-aligned within 1 ns), subtracting the two signals results in a flat response, which allows detection of any mode-jumping events reflected therein. If the compensation voltage (e.g., PSO 645) starts too early (e.g., waveform 1210), the voltage can drop rapidly after a 10 µs R2W transition. If the filter setting is too high (e.g., Filt_Error = 1.2, as shown in waveforms 1220 and 1225), the voltage may overshoot (i.e., return to above 0 mV). Plot 1200 can be shown because event detection can be bidirectional, thus the outputs of the positive and negative peak detectors can be monitored simultaneously as the user performs a full-factor scan of the delay and filter settings via firmware.

[0066] To further elaborate on the proposed method, the delay error can be scanned from -10ns to +10ns in 1ns steps. Within the same scan, the filter frequency can be scanned from 0.9 to 1.1 in 0.025 steps (i.e., in 2.5% steps within a + / -10% error range). Initially, the solution may involve setting the comparator threshold to 20mV, which represents 10% of the target threshold for mode transition detection.

[0067] Figure 13 Table 1300 shows the results. In Table 1300, when the delay matches within + / - 1 ns and the filter frequency matches within + / - 2.5%, both the positive and negative comparators (and their logic OR) are operable to not report events. This is evident in the MH_P, MH_N, and MH measurements reported separately in Figure / Table 1300. Table 1300 may reflect or refer to a solution, technique, or algorithm that can effectively allow the user to correctly optimize both the delay and filter frequency values ​​after having a first optimized amplitude. For example, scanning sensor 105 with a compensated signal match.

[0068] Figure 13 It is also revealed that amplitude, delay, and filter frequency matching can use a 20mV threshold to eliminate erroneous events. This suggests that the implementation can provide high-resolution scanning capabilities. If the amplitude and frequency response of sensor 105 exhibit variations greater than the threshold (e.g., erroneous readings may occur), then a wide tuning range can also be used. The delay tuning range can be wide enough to cover expected full-path propagation delay variations with process, voltage, and temperature.

[0069] like Figure 14 As shown in Table 1400, continuing the sensitivity analysis, if the system can tolerate a baseline error of 40 mV (V_Threshold = 40 mV), then the permissible delay and filter error can be increased to + / -2 ns and + / -5%, respectively. Figure 15 As shown in Table 1500, continuing the sensitivity analysis, if the detection threshold can be relaxed to 80mV, then the tolerable delay and filter error can be increased to + / -5ns and + / -10%, respectively.

[0070] In some aspects, calibration results may or may not use a suppression interval, and technical solutions can allow mode-jump detection to be available within less than 1 ns or 0.1 ns from the start of a write operation, thus functionally covering the entire duration of the write mode. In some aspects, system 600 may include a short suppression interval to relax the matching requirements between the compensation signal and the signal from sensor 105, since the peak amplitude of the offset can occur at approximately the beginning of the R2W transition. Besides increasing HPC to higher frequencies (e.g., 20 MHz), another effective suppression method could be to short-circuit the input of the peak detector at the beginning of the write until the end of the suppression interval. This additional technique can be combined with... Figure 16 Table 1600 and Figure 17 The solutions reflected in Table 1700 are shown or used, illustrating the results using a 20mV calibration threshold. By comparing them separately... Figure 13 , 16 From the results in Tables 1300, 1600, and 1700, we can see the trade-off between the accuracy of the compensated signal and the suppression times of 0 ns, 50 ns, and 100 ns, respectively. Therefore, a calibrated (e.g., optimal) solution can employ a compensated signal, calibration, and some programmable suppression intervals, with "no suppression" being an option.

[0071] Figure 18 This is an example flowchart of a method 1800 for providing laser mode transition detection in a hard disk drive according to an embodiment of this solution. Method 1800 may include actions 1805 to 1825, which may, for example, use a combination of... Figures 1 to 17A combined implementation of systems 100 and 600 is shown or described. For example, at 1805, the method may include generating a first signal. At 1810, the method may include delaying the first signal. At 1815, the method may include filtering the delayed first signal to output a second signal. At 1820, the method may include receiving a measurement. At 1825, the method may include subtracting the second signal from the measurement to output a third signal.

[0072] At 1805, the method may include generating a first signal. The method may include a first circuit system that generates a first signal representing a transition from a read operation to a write operation on the storage device. The first circuit system may include a voltage generator capable of generating the first signal. The first signal may include a generated voltage signal. The generated voltage signal may include a step voltage signal having an amplitude configured according to a control signal.

[0073] The first signal (e.g., a generated voltage signal) may comprise an increase from a first voltage corresponding to a read operation to a second voltage corresponding to a write operation. The difference between the first and second voltages may be a voltage value within the range of 10mV to 100mV. The value corresponding to the difference between the first and second voltages may be adjusted using control signals for controlling the first circuit system.

[0074] At 1810, the method may include delaying a first signal. The method may include a first circuit system delaying the first signal according to a first time period. The first circuit may include a delay circuit receiving a generated voltage signal from a voltage generator. The delay circuit may delay, time-shift, or time-shift the generated voltage signal for the duration of the first time period.

[0075] The first time period may correspond to a transition, such as the start time of a read / write (R2W) transition of an HDD. For example, the first time period, after the generated voltage signal is delayed or adjusted, may be or may include the duration from the time that causes the rise of the delayed first signal to the rise measured by a sensor indicating the R2W event reflected or indicated in the optical output of the laser.

[0076] The method may include a delay circuit of a first circuit system using a first time period to align the timing of a transition indicated by a second signal with the timing of a transition indicated by a measurement from a sensor. For example, the first time period may be adjusted to match the delays of one or more circuits, such as the propagation delay of a preamplifier, the propagation delay of a sensor, or the propagation delay of any one or more of the following: a sensor, any of a filter, a peak detector, a voltage generator, a delay circuit, and / or an amplifier. The first time period may be a value in the range of 500 picoseconds to 10 microseconds. This value may be adjusted according to a control signal used to control the delay circuit of the first circuit system.

[0077] At 1815, the method may include filtering the delayed first signal to output a second signal. The method may include a filter coupled to a first circuit system, the filter filtering out frequencies above a threshold from the delayed first signal according to a second time period of the filter's frequency response to output the second signal. The filter may include a low-pass filter. The filter may include a band-pass filter or a high-pass filter. The filter may include resistors and capacitors, such as resistors placed in parallel or series with capacitors. The filter may include resistors and inductors, such as resistors placed in parallel or series with inductors. The filter may include combinations of resistors, inductors, and capacitors, which may be arranged in parallel, series, or a combination of parallel and series arrangements.

[0078] A filter may include one or more frequency poles defined, set, or controlled based on its components or parts (e.g., its resistors, capacitors, and / or inductors). The filter may be a low-pass filter, which may attenuate, reduce, block, or filter frequencies above a threshold based on poles defined by the values ​​of resistors and capacitors arranged in parallel and defining the frequency response of the filter. The filter may adjust a first signal, delayed, to rise from a lower voltage level to a higher voltage level that expands, amplifies, or diffuses over a second time period defined by the filter's frequency response. The second time period may correspond to the duration during which a change in a delayed voltage signal (e.g., a voltage signal generated by a time offset) is scaled or diffused over time. The second time period may include or correspond to the duration during which a measurement from a sensor in a second circuit system transitions from a first measurement level corresponding to a read operation to a second measurement level corresponding to a write operation.

[0079] At 1820, the method may include receiving a measurement. The method may include a second circuit system that receives a measurement of the optical output of a laser in a storage device undergoing a transition and having a mode hopping of the laser. The second circuit system may include any combination of a sensor, wires for the sensor, filters (e.g., low-pass, band-pass, or high-pass filters), and / or amplifiers. The second circuit system may receive the measurement of the laser's optical output by monitoring a portion of the optical output (e.g., reflection of an optical signal). The storage device may be undergoing or is undergoing a transition, such as a read / write transition. The signal may indicate, experience, or reflect a mode hopping of the laser. The measurement may be reflected, included, indicated, or shaped at least based on the frequency response of the second circuit system. The frequency response of the second circuit system may correspond to the frequency response of the filter.

[0080] The frequency response of the second circuit system can be matched to the frequency response of the filter, and vice versa. For example, a filter can amplify or attenuate signals within a frequency range to match, align, simulate, or equal the amplification or attenuation of sensor measurements within the same frequency range. For example, a filter can provide an output with an amplitude at a specific frequency or frequency range that matches, is the same as, or corresponds to the amplitude of a sensor measurement output of a specific signal at a sensor within the same frequency or frequency range.

[0081] The received measurement may comprise a first part and a second part of a signal or measurement. The first part may correspond to an artifact or disturbance in the optical output of the laser. The artifact or disturbance may be caused by an increase in power input to the laser in response to a transition (e.g., a transition from read mode to write mode of an HDD). The received measurement may comprise a second part corresponding to a mode jump of the laser that occurs during or after the disturbance. The second part may comprise, reflect, or indicate the mode jump event within the time range of the disturbance in the optical output caused by the read / write transition. The time range between the mode jump event and the transition may be anywhere between 0.1 ns and 20 μs, such as 20 μs, 10 μs, 5 μs, 3 μs, 2 μs, 1 μs, 0.5 μs, 0.3 μs, 0.2 μs, 0.1 μs, 50 ns, 40 ns, 20 ns, 10 ns, 1 ns, or 0.1 ns.

[0082] The method may include a second circuit system of sensors that provides a sensor signal corresponding to the optical output of the laser. The signal may correspond to a specific small portion of the laser's optical output, such as a portion of the laser beam or a measurement of the reflection of the laser beam. The signal may correspond to a specific percentage of the optical output, such as up to 0.1%, 1%, 2%, 5%, or more of the signal.

[0083] The method may include a resistor and a capacitor for a filter, configured to match the frequency response of the filter to match the frequency response of a second circuit system. The resistor may be coupled to the output of a delay circuit in the first circuit system. The capacitor may include a first contact coupled to the resistor and a second contact coupled to ground. For example, the resistor may be arranged in parallel with the capacitor, wherein a delayed voltage signal from the delay circuit is input to the resistor. For example, the capacitor may have a value that is, or corresponds to, the reciprocal of 2π multiplied by the bandwidth of the sensor output or sensor measurement (e.g., 2 * 3.14159 * the bandwidth of the sensor response).

[0084] The method may include amplifying a sensor signal and generating a measurement via an amplification circuit of a second circuit system, wherein the sensor is one of a calorimeter or a photodetector, and the amplification circuit includes a differential amplifier configured to subtract a second signal from the measurement to output a third signal.

[0085] At 1825, the method may include subtracting a second signal from a measurement to output a third signal. The method may include a second circuit system subtracting the second signal from a measurement (e.g., from a sensor) to output a third signal identifying the occurrence of a mode transition of the laser. The second circuit system may include, for example, an amplifier or amplification circuit to combine the measurement signal and the second signal from a filter of a preamplifier. For example, the second circuit system may include a differential amplifier or subtraction circuit to subtract the sensor measurement signal from the second signal output from the filter of the preamplifier.

[0086] The method may include a second circuit system subtracting a second signal from a measurement to eliminate a first portion of the measurement that identifies the occurrence of a mode hopping event in the laser from the resulting third signal. The second circuit system may subtract the sensor measurement from the second signal output from a filter of a preamplifier to eliminate perturbations or artifacts of the read / write transition from the sensor measurement signal, thereby generating a third signal in which a mode hopping event can be detected. The mode hopping of the laser can occur at any time after the start of the transition, for example, within 0.6 μs, 0.3 μs, 0.1 μs, or 0.05 μs.

[0087] A reference to “or” can be interpreted as inclusive, such that any term described using “or” can refer to a single, more than one, or any of all the terms described. A reference to at least one of a list of combinations of terms can be interpreted as inclusive, indicating a single, more than one, or any of all the terms described. For example, a reference to “at least one of 'A' and 'B'” can include only 'A', only 'B', or both 'A' and 'B'. Such references used in conjunction with “include” or other open terms can include additional items.

[0088] It should be noted that certain paragraphs of this disclosure may refer to terms, such as “first” and “second,” used in conjunction with subsets of transport spatial streams, probe frames, responses, and means, for purposes of identification or distinction between one and another or for other purposes. These terms are not intended to associate entities (e.g., first means and second means) solely in time or according to sequence, although in some cases such a relationship may exist. These terms also do not limit the number of possible entities (e.g., delay circuits, filters, peak detectors) that can operate in the system or environment. It should be understood that the system described above may provide any or multiple of those components, and these components may be located on a standalone machine, or, in some embodiments, on multiple machines in a distributed system. Furthermore, the bit field positions may be changed, and multiple bit words may be used. Additionally, the above-described systems and methods may be provided as one or more computer-readable programs or executable instructions embodied on or within one or more articles of manufacture (e.g., floppy disk, hard disk, CD-ROM, flash memory card, PROM, RAM, ROM, or magnetic tape). At least a portion of the technical solution can be implemented in any programming language (e.g., LISP, PERL, C, C++, C#) or in any bytecode language (e.g., JAVA). The software program or executable instructions can be stored as object code on or within one or more artifacts.

[0089] While the foregoing written description of the methods and systems enables those skilled in the art to make and use embodiments thereof, those skilled in the art will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiments, methods, and examples herein. Therefore, the methods and systems should not be limited to the embodiments, methods, and examples described above, but should be limited to all embodiments and methods within the scope and spirit of this disclosure.

Claims

1. A storage device system comprising: A first circuit system is configured to generate a first signal representing a transition from a read operation to a write operation of the storage device, and to delay the first signal according to a first time period. A filter coupled to the first circuit system to filter out frequencies above a threshold from the delayed first signal, and outputs a second signal according to a second time period based on the frequency response of the filter; A second circuit system is used to receive a measurement of the optical output of the laser of the storage device undergoing the transition and having a mode jump of the laser, the frequency response of the second circuit system being indicated by the measurement and corresponding to the frequency response of the filter; The second circuit system is used to subtract the second signal from the measurement to output a third signal that identifies the occurrence of the mode transition of the laser.

2. The storage device system of claim 1, wherein the first signal comprises an increase from a first voltage corresponding to the read operation to a second voltage corresponding to the write operation, and wherein the first time period corresponds to the start time of the transition.

3. The storage device system of claim 2, wherein the difference between the first voltage and the second voltage is a value in the range of 1 mV to 1000 mV, the value being adjustable according to a first control signal for controlling the first circuit system.

4. The storage device system according to claim 1, comprising: The first circuit system has a delay circuit for aligning the time of the transition indicated by the second signal with the time of the transition indicated by the measurement using the first time period.

5. The storage device system of claim 1, wherein the first time period is adjustable to a duration value in the range of 500 ps to 10 us according to a second control signal for controlling the delay circuit of the first circuit system.

6. The storage device system according to claim 1, comprising: The filter has a resistor that is coupled to the output of the delay circuit of the first circuit system. and The filter has a capacitor having a first contact coupled to the resistor and a second contact coupled to ground, wherein the resistor and the capacitor configure the frequency response of the filter to match the frequency response of the second circuit system.

7. The storage device system according to claim 1, comprising: The second circuit system has a sensor configured to provide a signal corresponding to the optical output of the laser; and The second circuit system has an amplifier circuit for amplifying the signal from the sensor and generating the measurement.

8. The storage device system of claim 7, wherein the sensor is a photoelectric transducer and the amplification circuit includes a differential amplifier configured to subtract the second signal from the measurement to output the third signal.

9. The storage device system of claim 1, wherein the second time period corresponds to the duration during which the measurement from the sensor of the second circuit system changes from a first level corresponding to the read operation to a second level corresponding to the write operation.

10. The storage device system of claim 1, wherein the measurement comprises a first portion corresponding to a disturbance in the optical output of the laser caused by an increase in power input to the laser in response to the transition, and a second portion corresponding to a mode jump of the laser occurring during or after the disturbance.

11. The storage device system of claim 10, wherein the second circuitry is configured to subtract the second signal from the measurement to eliminate the first portion of the measurement from the third signal that identifies the occurrence of the mode transition of the laser.

12. The storage device system of claim 1, wherein the mode transition of the laser occurs within 1 microsecond after the start of the transition.

13. The storage device system of claim 1, wherein the third signal is input to a third circuit system, the third circuit system comprising at least: A bandpass filter, an amplifier, and a peak detector, the peak detector being configured to detect the occurrence of the mode-jumping event in response to a peak value in a signal output from the amplifier and filtered by the bandpass filter exceeding a threshold value of the peak detector.

14. A method for performing storage device operations, comprising: A first signal representing the transition from a read operation to a write operation on the storage device is generated by a first circuit system; The first signal is delayed by the first circuit system according to a first time period; A filter coupled to the first circuit system filters out frequencies above a threshold from the delayed first signal to output a second signal in a second time period according to the frequency response of the filter. The second circuit system receives a measurement of the optical output of the laser of the storage device after the transition and the laser mode jump, the measurement indicating the frequency response of the second circuit system corresponding to the frequency response of the filter; and The second circuit system subtracts the second signal from the measurement to output a third signal that identifies the occurrence of the mode transition of the laser.

15. The method of claim 14, wherein the first signal comprises an increase from a first voltage corresponding to the read operation to a second voltage corresponding to the write operation, and the first time period corresponds to the start time of the transition, and wherein the difference between the first voltage and the second voltage is a value in the range of 1 mV to 1000 mV, the value being adjustable using a first control signal for controlling the first circuit system.

16. The method of claim 14, further comprising: The delay circuit of the first circuit system uses the first time period to align the time of the transition indicated by the second signal with the time of the transition indicated by the measurement, wherein the first time period is a value in the range of 500 picoseconds and 20 microseconds, the value being adjustable according to a second control signal for controlling the delay circuit of the first circuit system.

17. The method of claim 14, further comprising: The frequency response of the filter is configured by the resistor and the capacitor of the filter to match the frequency response of the second circuit system, wherein the resistor is coupled to the output of the delay circuit of the first circuit system, and the capacitor includes a first contact coupled to the resistor and a second contact coupled to ground; The sensor of the second circuit system provides a signal corresponding to the optical output of the laser; and The signal from the sensor is amplified by the amplification circuit of the second circuit system to generate the measurement, wherein the sensor is a photoelectric transducer, and the amplification circuit includes a differential amplifier configured to subtract the second signal from the measurement to output the third signal.

18. The method of claim 14, wherein: The second time period corresponds to the duration during which the measurement from the sensor of the second circuit system changes from a first level corresponding to the read operation to a second level corresponding to the write operation; and The measurement includes a first portion corresponding to a disturbance in the optical output of the laser caused by an increase in power input to the laser in response to the transition, and a second portion corresponding to a mode jump of the laser that occurs during or after the disturbance.

19. The method of claim 14, further comprising: The second circuit system subtracts the second signal from the measurement to eliminate the first portion of the measurement that identifies the occurrence of the mode transition of the laser from the third signal, wherein the mode transition of the laser occurs within 1 microsecond after the start of the transition.

20. A storage device system comprising: A voltage generator is used to generate a first signal representing the transition from a read operation to a write operation on the storage device; A delay circuit, used to delay the first signal according to a first time period; A filter coupled to the delay circuit to filter out frequencies above a threshold from the delayed first signal, and outputs a second signal according to a second time period based on the frequency response of the filter; and Amplifier, which is used for: Receive the second signal from the filter; Measurements are received from the sensor of the optical output of the laser of the storage device undergoing the transition and having a mode jump of the laser, the measurements indicating the frequency response of a second circuit system that matches the frequency response of the filter; and The second signal is subtracted from the measurement to output a third signal that identifies the occurrence of the mode transition of the laser.

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