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

Abstract

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

Description

[0001] Cross-references to related patent applications

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

[0003] The present disclosure generally relates to systems and methods for control and operation of hard disk drives (HDDs), including but not limited to laser mode hop detection in HDDs. Background Art

[0004] Hard disk drives (HDDs) can be used to store data in computers and other electronic devices. HDDs can include various designs and components, such as magnetically sensitive platters on which data can be written or read and actuator arms for reading or writing data. HDDs can utilize lasers for their operation. Summary of the invention

[0005] Heat Assisted Magnetic Recording (HAMR) is an energy-assisted technology in hard disk drives (HDDs) in which lasers can be used to heat localized areas of high coercivity media to enable more efficient data recording. The consistency and size of the area heated by the laser on the disk surface can be important for maximizing recording density because it can define the track and bit spacing. The area on the disk surface heated by the laser to record data can be referred to as the "spot size". While recording data, the laser of the HDD can experience mode jumps, which can include sudden shifts in the operating mode or characteristics of the laser, resulting in changes in laser output properties, such as the frequency or power of the laser output. These sudden changes caused by mode jumps can result in sudden changes in the spot size, which can result in phase shifts being imprinted into the recorded data, which exceeds the recovery capabilities of the HDD's read channel, resulting in data written during the mode jump being corrupted. In such examples, the system can identify that a mode jump has occurred that exceeds a previously determined allowable threshold, and rewrite the damaged sector before clearing the data buffer. If this corrective action is not taken before clearing the data buffer, the data may not be retrievable, making adequate mode hop detection an important feature in HAMR systems.

[0006] When the HDD transitions from a read operation in which data is read from the HDD to a write operation in which data is written to the HDD, the laser power output may 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, within a certain time after a read / write (R2W) transition (e.g., within tens or hundreds of nanoseconds after the transition), a power monitoring device, for example, may output a signal similar to a mode jump to a preamplifier of the HDD system, making it difficult to determine whether a true mode jump has occurred or whether the signal is due to the R2W transition. As a result, it may be challenging to reliably detect a true mode jump event of the laser when the true mode jump event of the laser coincides with a time period immediately after the R2W mode transition (e.g., approximately 1 to 2 microseconds). The present solution overcomes this challenge by allowing more reliable and accurate jump detection in the time period immediately following the R2W mode transition, by providing a circuit that subtracts a signal that matches the frequency response of the detector from the laser detector signal, allowing the mode jump signal to be reliably detected throughout the entire duration of the 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 of a storage device to a write operation of 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 output a second signal according to a second time period of a frequency response of the filter. The system may include a second circuit system for receiving a measurement of an optical output of the laser of the storage device undergoing the transition and having a mode hop 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 hop of the laser.

[0008] The first signal may include 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 time of the start of the transition. The difference between the first voltage and the second voltage is typically in the range of 1 mV and 1000 mV. The value may be adjusted according to a first control signal for controlling the first circuit system.

[0009] The system may include a delay circuit of the first circuit system to align 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. The first time period may be adjusted to a duration value typically in the range of between 5ns and 10us according to a second control signal for controlling the delay circuit of the first circuit system.

[0010] The system may include a resistor of the filter. The resistor may be coupled to an output of the delay circuit of the first circuit system. The system may include a capacitor of 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 configure 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 of the sensor corresponding to the optical output of the laser. The system may include an amplification circuit of the second circuit system to amplify the signal of the sensor and produce the measurement. The sensor may be a photoelectric transducer, such as a bolometer or a photodetector. The amplification 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 a duration in which the measurement from the sensor of the second circuit system transitions from a first level of the measurement corresponding to the read operation to a second level of the measurement corresponding to the write operation. The measurement may include a first portion corresponding to a perturbation in the optical output of the laser caused by an increase in power input into the laser in response to the transition and a second portion corresponding to the mode hop of the laser occurring during or after the perturbation.

[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 identifying the occurrence of the mode hop of the laser. The mode hop of the laser can occur at any time after or about the start of the transition.

[0014] The third signal may be input into a third circuit system. The third circuit system includes at least: a bandpass filter, an amplifier, and a peak detector, wherein the peak detector is used to detect the occurrence of the mode jump event in response to a peak value in the signal output from the amplifier and filtered by the bandpass filter exceeding a threshold 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 of a storage device to a write operation of the storage device. The method may include the first circuit that delays the first signal according to a first time period. The method may include a filter that is coupled to the first circuit system and filters out frequencies above a threshold from the delayed first signal to output a second signal according to a second time period of a frequency response of the filter. The method may include a second circuit system that receives a measurement of an optical output of the laser of the storage device undergoing the transition and having a mode hop 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 hop of the laser.

[0016] The first signal may include 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 time of the start of the transition. The difference between the first voltage and the second voltage is typically between 1 mV and 1000 mV. The value may be adjusted using a first control signal for controlling the first circuit system.

[0017] The method may include a delay circuit of the first circuit system that 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. The first time period may be a value in a range between 5 nanoseconds and 10 microseconds. The value may be adjusted according to a second control signal for controlling the delay circuit of the first circuit system.

[0018] The method may include a resistor of the filter and a capacitor of the filter that configures the frequency response of the filter to match 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, by a sensor of the second circuit system, a signal of the sensor corresponding to the optical output of the laser. The method may include an amplification circuit of the second circuit system that amplifies the signal of the sensor and produces the measurement. The sensor may be one of a bolometer 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 a duration in which the measurement from the sensor of the second circuit system transitions from a first level of the measurement corresponding to the read operation to a second level of the measurement corresponding to the write operation. The measurement may include a first portion corresponding to a perturbation in the optical output of the laser caused by an increase in power input into the laser in response to the transition and a second portion corresponding to the mode hop of the laser occurring during or after the perturbation.

[0020] The method may include the second circuitry subtracting the second signal from the measurement to eliminate from the third signal a first portion of the measurement identifying an occurrence of the mode hop of the laser. The mode hop of the laser may 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 of a storage device 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 a 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 of an optical output of the laser of the storage device undergoing the transition and having a mode jump of the laser from a sensor. The measurement may indicate a frequency response of the second circuit system that matches 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 jump of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] These and other aspects and features of the present embodiments will become apparent to those of ordinary skill in the art when the following description of specific embodiments is read in conjunction with the accompanying drawings.

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

[0024] Figure 2 are example waveforms of the operation or results of a mode hop detection system.

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

[0026] Figure 4 is an example of a waveform that is a result of the operation of a mode hop detection system.

[0027] Figure 5 is an example of a waveform that is a result of the operation of a mode hop detection system.

[0028] Figure 6 is an example block diagram of a mode hop detection system using a transducer sensor that uses a preamplification circuit to model the sensor response in the mode hop detection system.

[0029] Figures 7 to 12 is an example of a waveform of the operation or result of the mode hopping detection system of the present solution.

[0030] Figures 13 to 17 It is an example of a table or operation result of the mode jump detection system of the present solution.

[0031] Fig.18 An example flow chart illustrating a method for providing mode hop detection according to an embodiment of the present solution. DETAILED DESCRIPTION

[0032] The present embodiment should now be described in detail with reference to the accompanying drawings, which are provided as illustrative examples of the embodiments so that those skilled in the art can practice embodiments and alternatives that are obvious to those skilled in the art. The following drawings and examples are not meant to limit the scope of the present embodiment to a single embodiment, but other embodiments are possible by exchanging some or all of the elements described or illustrated, or those that are obvious to those skilled in the art. Certain elements of the present embodiment may be implemented partially or completely using known components, and only those parts of such known components necessary for understanding the present embodiment should be described, and detailed descriptions of other parts of such known components will be omitted to avoid confusing the present embodiment. The embodiments described in the illustrated context of the embodiments should not be limited thereto. For example, embodiments described as being implemented in hardware or in software should not be limited to such implementations, but they may include embodiments implemented in hardware, software, or any combination of software and hardware, which 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 restrictive; on the contrary, unless otherwise explicitly stated herein, the present disclosure is intended to cover other embodiments including multiple identical components, and vice versa. Furthermore, applicant does not intend that any term in the specification or claims be assigned an unusual or special meaning unless expressly so set forth. Further, the present embodiments encompass present and future known equivalents to the known components mentioned herein by way of illustration.

[0033] While the HAMR system may include different styles of power monitoring transducers or sensors, such as photodiodes and bolometers, the present technical solution may be applicable to any power monitoring device. While bolometers may be used in the illustrated examples, any other monitoring transducer may 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. In addition, the mode hop may not have a preferred polarity, and thus the event may result in an increase or decrease in laser power. While the illustrated examples may discuss examples of mode hops with positive polarity, it should be understood that the solution may be similarly applicable to either polarity.

[0034] Because the technical solution provided herein can adapt to the characteristics of any power monitoring device, the present solution can solve the problem of timely laser jump detection (or any other electrically or electronically time-constrained detection) for a variety of applications, including any fast or time-constrained detection. The technical solution can improve power monitor sensitivity and frequency response over a range of amplitude, delay, and frequency response tuning. HAMR systems can use power changes between read and write operations (e.g., read and write modes), and the technical solution can use it to provide improvements to HAMR HDD devices and related applications. The technical solution provides improved and accurate mode jump detection for a larger portion of a write event, including covering the entire write event or a time period during which a write operation occurs.

[0035] Figure 1 An example of a block diagram illustrating a mode hop detection system 100. The mode hop detection system 100 may include a circuit or circuitry that may include and utilize a transducer sensor 105 that measures an optical output 155 from a laser 150 and provides the sensor measurement 125 to a filter 130. The filter 130 may filter the received sensor measurement 125 and provide its output to a peak detector that may utilize a threshold 160 to provide a mode hop 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 a magnetic recording medium of a HDD, producing a localized heated region. The optical output 155 of laser 150 may include any emitted light or electromagnetic radiation produced 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 the heat reduces the coercivity of the medium, the HDD may more easily write data to the disk, allowing for higher recording density and improved storage capacity in the HDD. Laser 150 may operate at a power range between one or more milliwatts to one or more watts. Optical output 155 may include any optical output range between 400nm and 10um, including, for example, a range of 800 to 1000nm.

[0037] The sensor 105 may be placed or positioned near the laser 150 or its optical output 155, monitoring a small portion of the optical output 155. The sensor 105 may include any sensor for measuring the optical output 155 from the laser 150. The sensor 105 may be any device that converts one type of energy to another type of energy, including, for example, an optoelectronic transducer (e.g., a bolometer or a photodetector). The sensor 105 may include or be characterized by a resistance RSensor 120, which may be inherent in the sensor 105. Since the sensor 105 may be driven with a DC bias current ISensor 110, the voltage VSensor 115 (e.g., the voltage across the sensor 105) may be detected, measured, and monitored. Monitoring ISensor 110 and / or VSensor 115 may allow the present technology solution to react when sensor 105 (e.g., a bolometer or photodetector) is exposed to optical output 115 (e.g., a change in optical output due to a change in laser power input). For example, a power disturbance may cause a disturbance in RSensor 120 and may affect the VSensor voltage, resulting in a change in sensor measurement 125.

[0038] The VSensor 115 voltage of the sensor 105, which may reflect any changes in the optical output 155 signal, may be input into or passed through the filter 130 as the sensor measurement 125. In some examples, depending on the type of sensor 105, the Isensor 110 current may be input into the filter 130 as the sensor measurement 125. The filter 130 that receives the sensor measurement 125 may include a bandpass filter and may include gain circuitry with a programmable gain for amplifying or boosting the sensor measurement 125. The filter 130 may have a corner frequency (e.g., a frequency pole) to remove DC signals or content (which may be large) and to remove any high frequency signals or noise. The output of the filter 130 (e.g., a bandpass filter) may be fed to or passed to a peak detection circuit or peak detector 135. The peak detector 135 may include and utilize a programmable threshold 150 to detect whether the filtered sensor measurement includes a peak indicating the occurrence of a mode jump event. A mode jump event may include any rapid and unexpected change in the operating mode or characteristics of the laser 150 (e.g., a disturbance) resulting in a sudden shift in the output properties of the laser (e.g., frequency, mode, or power). The programmable threshold 160 may include or may be coupled to a circuit that may send a digital output to a fault monitoring control circuit system. The peak detector 135 may detect a mode jump event that may 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 jump detection signal 140 indicating that a mode jump event has been detected. This, in turn, may allow the HDD system to utilize circuit systems or functions to correct any corrupted data, or take corrective action with the laser 150.

[0039] Figure 2 exhibit Figure 1200 of waveforms illustrating the operation or results of system 100 in FIG. 205. In this example, a mode jump may occur at time = 20 us. The mode jump event may 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 bolometer 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 bolometer may have a bandwidth of only 1 MHz, it will respond with a delay of approximately 1 microsecond (us). Therefore, the bolometer will take approximately 1 us to fully respond to such a mode jump event, as indicated by plotted waveform 205. If the signal is then amplified or gain 50 V / V (e.g., via an amplifier) ​​and passed through a 2 kHz high pass filter 130, the result may be expressed by plotted waveform 220 (e.g., “Vp_PkDet”). If the user sets the mode jump detection threshold 160 to 200 mV (e.g., as shown by the plotted waveform 225) with reference to the input of the peak detector 135, then a fault condition (e.g., plotted waveform 215) may be reported as long as the waveform 220 is greater than the waveform 225 (e.g., Vp_PkDet>Vn_PkDet). This digital signal, where "1" represents a logic high and "0" represents a logic low, may then be latched and reported to the system controller so that a rewrite may be initiated (e.g., to repair any corrupted data caused by the mode jump event).

[0040] As shown in example 200, the system 100 may require 1 us to detect a mode hopping event, and this amount of time may be equivalent to a large portion of the recording duration. This may be a result of the low bandwidth of the sensor 105. The 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 result of the low HPC may be that the peak detector input requires >200us to return to its steady state value. This can create challenges in accurately detecting a hopping mode event after the first.

[0041] A read operation in an HDD may include the process of retrieving data from a storage medium, such as by using a read / write head to access and read information stored on a disk. A write operation in an HDD may include the process of storing data on a magnetic storage medium by encoding the data using a magnetic write head. The technical solution of the present disclosure overcomes the challenges of current mode jump detection systems that use preamplifier circuit solutions to allow detection of mode jump events even during the time period around a read / write (R2W) transition.

[0042] A read / write (R2W) transition may include any switching of a storage device, such as a hard disk drive (HDD), from a read mode of operation to a write mode of operation, which may involve a change in the power output of the laser (e.g., from a lower power in a read mode to a higher power in a write mode), or a change in other parameters to achieve data recording. For example, when a preamplifier circuit is commanded to enter a write mode (e.g., from a read mode), the laser power may be rapidly increased to achieve a recording threshold. In the case of such an R2W transition, if the laser output power is not increased in time, previously recorded data may be partially erased, resulting in insufficient storage duration (e.g., the laser bias current is too high during reading), or new data may not be recorded at all (e.g., the laser bias voltage is too low during writing). However, as an artifact of the sudden increase in laser power, the laser may experience a disturbance at about the time of the R2W transition, making it difficult to detect the actual mode jump event during the disturbance.

[0043] Figure 3 Depicts an example 300 of a plotted waveform 305 showing an R2W transition occurring at time = 10us. When the R2W transition occurs, the sensor 105 (e.g., a bolometer) may output an increase in signal output from 50mV (e.g., sensor measurement 125 during a read mode operation of the HDD) to 100mV (e.g., sensor measurement 125 during a write mode operation of the HDD). The sensor 105 may make this transition from 50mV to 100mV over the course of 1us. This may be a response to a command for additional laser bias current (i.e., power) used by the HDD system to record data.

[0044] refer to Figure 4 , illustrating an example 400 of the input and output of the peak detector 135 while maintaining a mode jump detection threshold of 200mV (e.g., as shown by the dashed line). For example, the system may set (e.g., increase) the HPC of the detection path by multiple orders of magnitude (e.g., from 2kHz to 20MHz) upon R2W transition in order to minimize disturbances at the input of the peak detector 135. If this is not done (e.g., waveform 405), then an erroneous mode jump of >200us may be reported (e.g., waveform 405 of the lower right plot). An erroneous mode jump of 200us may last longer than an entire written sector, providing insufficient mode jump protection during that time period. Since increasing the HPC can have the effect of attenuating the signal at lower frequencies and achieving faster baseline stabilization, it can be used to "suppress" disturbances. Suppression may also involve other techniques, such as using switches to disconnect, using switches to short the inputs of the peak detector, and using cross-coupled differential pairs to reroute / eliminate signals. For Figure 4 and 5, techniques can be used to increase HPC to ~20MHz.

[0045] The waveform 410 may show that if the HPC remains high (~20MHz) for a minimum of 450ns after the R2W transition, then no false events will be reported due to the bias change. However, in this example, write mode jump detection may be compromised because the residual perturbation remaining after moving 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 over-reporting a problem via a minor mode jump event that had previously been determined to be non-problematic.

[0046] Furthermore, if the duration of the ~20 MHz HPC suppression interval were to be extended to 1 us (waveform 415), then the entire bias change event could be effectively suppressed. This could be beneficial for the remainder of the write. However, coverage of the entire 1 us could be lost, and mode hopping could occur at any time within the write, even within the first 1 us. In some examples, the initial 1 us after the R2W transition could be the time when a mode hopping event is most likely to occur, since this is when the operating point of the laser changes (e.g., from a lower power level to a higher power level).

[0047] In some examples, a suppression (or masking) interval of approximately 1 us may be used to allow robust, accurate mode jump detection (ie, no false reporting) for the remainder of the write. Figure 5 The illustration shows an example 400 of a plot utilizing this masking interval and a mode jump event occurring at 200ns into write mode (e.g., waveform 505) and a mode jump event occurring at 1us into write mode (e.g., waveform 510). In such an implementation, only events at 1us after the R2W transition may be detected. Data from a write where the mode jump occurs at 200ns may be unrecoverable, and the HDD controller may not be aware of this. Therefore, for a preamplifier designed to provide maximum mode jump detection coverage, suppression alone may be an insufficient solution, and the present technology solution may provide coverage of the entire write interval.

[0048] Figure 6An example of a system 600 that provides or facilitates improved laser mode jump detection for the entire operation of a HDD (e.g., including within 1us of a read / write mode transition event) is described. The example system 600 may be referred to as a compensation circuit having a preamplifier that matches the frequency response of the sensor 105. The frequency response may include any characteristic behavior of a circuit, 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 a circuit, device, or system transmits, attenuates, or amplifies a signal depending on the frequency within a given frequency range.

[0049] The example system 600 may include a voltage generator 605 that provides a generated voltage signal (GVS) 635 (e.g., VComp) that is input into 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. The DVS 640 may be input into a filter 615 that may include one or more resistors and capacitors (e.g., a 1 kilo-ohm (1K) R4 resistor and a capacitor C10 having a capacitance C of 1 / (2π*BW_Bolo), where π is 3.14159 and BW_Bolo is the bandwidth of the sensor 105 signal output. The filter 615 may output a preamplifier signal output (PSO) 645 (e.g., VComp_filt), which may be fed into an amplifier 620, which may also receive a sensor measurement 125 (e.g., a V_Bolo signal) from the sensor 105. The amplifier 620 may combine the two signals (eg, subtract the PSO 645 from the amplified sensor measurement 125) and generate or output a signal 630 with a mode jump. The signal 630 with a mode jump (eg, V_Bolo_Comp) may be sent as an input to Figure 1 The signal is filtered by the filter 130 and then processed by the peak detector 135 to generate the mode jump detection signal 140 when the threshold 160 is exceeded.

[0050] exist Figure 6At , example system 600 may include or correspond to a preamplifier circuit, which may include voltage generator 605, delay circuit 610, and filter 615. The preamplifier circuits (e.g., 605, 610, and 615) may collectively generate a frequency response that corresponds to (e.g., correlates, aligns, or matches) the frequency response of sensor 105. For example, the preamplifier circuits (e.g., 605, 610, and 615) may match the frequency response of sensor 105 and any circuitry and contacts of sensor 105 to amplifier 620. In some aspects, system 600 includes or corresponds to a preamplifier circuit having a reciprocal of the frequency response that corresponds to (e.g., correlates, aligns, or matches) sensor 105 and its circuitry and contacts that provide sensor measurements 125 to system 600.

[0051] The system 600 may include a voltage generator 605, which may include any combination of hardware and software, devices or circuit systems for generating voltages. 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 in a range between external power supplies. The voltage generator 605 may include or utilize programmable switching circuitry to adjust the voltage level output and also provide a response within a time range of about 1ns, such as 0.1ns, 0.5ns, 10ns, 20ns, or longer. The 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 the delay circuit 610.

[0052] The 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-shifted) version of the GVS 635, referred to as a delayed voltage signal (DVS) 650. The delay circuit 610 may include a programmable delay element that provides a version of the input signal that is delayed by a set amount of time, such as any time value between 1 ns and 20 us, such as up to 500 ns, 1 us, 3 us, 5 us, 10 us, or 20 us. The delay circuit 610 may have a resolution to adjust the time in steps of about 10 to 100 ns, such as at least 10 ns, 20 ns, 30 ns, 50 ns, 70 ns, or 100 ns. The delay circuit 610 may provide a delayed output version of the input signal (e.g., VComp_Del) that may be input into the filter 615.

[0053] Filter 615 may include any filter (e.g., low pass, band pass, or high pass) that may be used to filter frequency DVS 640 output from delay circuit 610 and input into filter 615. Filter 615 may include a programmable low pass filter that may have a frequency response that matches the frequency response or characteristics of sensor 105 (e.g., a bolometer or photodetector for detecting optical output 155 of laser 150). Filter 615 may have a frequency response that matches the frequency response of sensor 105 and its contact lines and any processing circuitry, such as connection lines or amplification circuitry that increases the gain of sensor measurement 125 prior to combining the amplified sensor measurement 125 with the amplified PSO 645. For example, PSO 645 may be subtracted from sensor measurement 125 prior to or without any gain adjustment being made 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 ​​may be adjusted, modified, or altered to match the frequency response of sensor 105 and its signal path to amplifier 620, where PSO 645 is to be subtracted from sensor measurement 125. System 60 may implement subtracting the delayed and filtered step voltage from the bolometer response at the R2W transition.

[0055] The present solution may include a feed-forward arrangement where the matching frequency response of the sensor 105 (e.g., bolometer) may be regenerated in the preamplifier (e.g., voltage generator 605, delay circuit 610, and filter 615) and then subtracted from the actual sensor 105 response. The laser mode hop event may appear as a perturbation in the optical output 155 and may be easily detected because the bulk sensor 105 response due to the non-hopping laser power change (e.g., the optical output 155 perturbation caused by the R2W mode transition) may now be cancelled (e.g., by subtracting the PSO 645 from the sensor measurement 125). As a result, the residual signal 630 with mode hop may not include the residual perturbation due to the R2W transition, leaving only the true mode hop event for the system to detect.

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

[0057] Figure 7 A plot 700 is shown illustrating performance when amplitude, delay, and filter match sensor 105 frequency response or characteristics. The preamplifier circuitry (e.g., 605, 610, and 615) can produce a frequency response that matches the frequency response of the sensor 105 within an acceptable threshold tolerance, 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, since the transient behavior of the PSO 645 at the R2W transition (e.g., 710 or VComp_filt) accurately matches the transient behavior of the 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) can remain undisturbed during the entire transition. This can be achieved with a static 2kHz setting of the HPF (ie, no suppression / masking interval).

[0058] Figure 8An example plot 800 showing example performance and advantages of a compensation circuit (e.g., system 600) when a 5 mV mode jump occurs into a write event at 200 ns (e.g., waveforms 805, 815, 825, and 835) and 1 us (e.g., waveforms 810, 820, 830, and 840) (e.g., after an R2W transition). Because the expected baseline shift can be compensated and the hold-down interval is not activated, both mode jumps can be detected. The voltage at waveforms 815 and 820 (e.g., V_Bolo_Comp) can increase by 5 mV due to the mode jump. In addition, 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 system perturbations can be compensated and the HPF corner can be kept at its steady-state value (2kHz), mode jump detection can be available without any spurious activity from the beginning to the end of writing.

[0059] In one embodiment, 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 matches or matches within a predetermined tolerance threshold with characteristics of the sensor 105 or sensor measurement 125, a technical solution may be implemented. For example, the 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 the sensor measurement 125. When the PSO 645 may be mapped (e.g., one-to-one) for the entire sensor measurement 125 to match the characteristics of the sensor measurement 125 corresponding to the optical output 155 signal artifact or disturbance caused by the R2W transition, when the PSO 645 is subtracted from the sensor measurement 125, all optical disturbances, artifacts, or other properties caused by the R2W transition may be removed, providing a signal 630 with mode jumps that only include mode jump events. For example, such mode hop 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 mass production of the system there may be system variations, there may be variations in design and / or performance. Fig. 9 , 10 The sensitivity for each parameter can be provided by referring to the discussion of FIG. 11. For these three figures, the detection threshold can be set to 200 mV, since it can be measured at the signal 630 with the mode jump or at the input of the peak detector 135.

[0061] Fig. 9900 is illustrated showing that an error of almost + / -20% in the filter frequency can be tolerated before an error event is reported. For example, when the error (e.g., in the filter frequency) is -20%, waveform 905 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in the filter frequency) is -10%, waveform 910 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in the filter frequency) is 0%, waveform 915 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in the filter frequency) is +10%, waveform 920 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in the filter frequency) is +20%, waveform 925 corresponds to the Vp_PkDet signal. As shown in plot 900, correctly matching the signals and reducing the percentage error can benefit the output of the system.

[0062] Fig.10 A plot 1000 showing the effect of amplitude error on the performance of the system 600 is illustrated. For example, the plot 1000 can show the degree to which the system 600 can tolerate amplitude error (e.g., about + / - 20%) because signals greater than that degree can generate an error event (e.g., the implementation detection can detect both polarities). For example, when the error (e.g., in amplitude) is -20%, the waveform 1005 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in amplitude) is -10%, the waveform 1010 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in amplitude) is 0%, the waveform 1015 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in amplitude) is +10%, the waveform 1020 corresponds to the Vp_PkDet signal. For example, when the error (e.g., in amplitude) is +20%, the waveform 1025 corresponds to the Vp_PkDet signal.

[0063] at last, Fig.11Plot 1100 is illustrated, which shows that propagation delay difference can be a sensitive parameter because an error of 20 ns can cause an error event. For example, plot 1100 can show the degree to which system 600 can tolerate delay mismatches or errors (e.g., about + / - 20 ns relative to the measured signal) because a time mismatch at about 20 ns can produce an error 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 +20ns, waveform 1125 corresponds to the Vp_PkDet signal. As shown in waveform 1125, the +20ns time mismatch results in an erroneous mode hop detection, while waveform 1115 shows a flat mode hop curve (e.g., no mode hop event is accurately detected).

[0064] Another aspect of the present solution may include an effective and practical calibration solution, algorithm or technique. Calibration may be used when producing HDDs so as to fine tune the system 600 to account for any manufacturing variations. For example, a calibration solution may 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 may be calibrated, such as voltage amplitude, which may be the first parameter to be calibrated, and which may be measured before any high-pass filtering. For example, calibration may be started by measuring the DC output of sensor 105 (e.g., a bolometer or photodetector) in both the 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) may fully represent a true write event. To avoid affecting any recorded data, this may be performed when the preamplifier is idle or in standby (e.g., parked on a ramp). At this same measurement point, the user can switch to monitoring the calibration voltage and sweep its control DAC until its output matches the previously measured difference (V_Bolo_write-V_Bolo_read) in the sensor 105 output from read to write (e.g., sensor measurement 125). As the calibrated (e.g., optimal) compensation amplitude is 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 of the peak detector) can be the monitoring point.

[0065] Fig.12 Illustrated is a plot 1200 showing several waveforms (e.g., 1205-1230), the first of which may include the original response (e.g., waveform 1230) at the input (black) of the positive peak detector without compensation applied. Below waveform 1230, there may be two sets of waveforms, both of which sweep the filter error from 80% to 120% (e.g., from -20% to +20%). The dashed set of waveforms (e.g., 1205-1225) may show the response when the compensation signal (e.g., PSO 645) leads the original signal (e.g., sensor measurement 125) by 20ns (i.e., -20ns error). The solid waveforms (e.g., 1235-1255) may include the same filter error sweep, 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 aligned in time to within 1 ns), subtracting the two signals can result in a flat response, which can allow detection of any mode jump events reflected therein. If the compensation voltage (e.g., PSO 645) starts too early (e.g., waveform 1210), the voltage can drop quickly after the 10us R2W transition. If the filter setting is too high (e.g., Filt_Error=1.2, such as in waveforms 1220 and 1225), the voltage may overshoot (i.e., return to above 0mV). Plot 1200 can show that because event detection can be bidirectional, the outputs of the positive and negative peak detectors can be monitored together as the user performs a full factor sweep of delay and filter settings via firmware.

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

[0067] Fig.13 Table 1300 with the results is shown. In table 1300, when the delay is matched within + / -1ns and the filter frequency is matched within + / -2.5%, both the positive and negative comparators (and their logical OR) are operable to not report an event. This is evident in the MH_P, MH_N, and MH measurements reported respectively in graph / table 1300. Table 1300 may reflect or refer to a solution, technique, or algorithm that may effectively allow a user to correctly optimize both the delay and filter frequency values ​​after having a first optimized amplitude. For example, this amplitude of the sensor 105 is scanned and the compensation signal matches.

[0068] Fig.13 It is also disclosed that amplitude, delay, and filter frequency matching can use a 20mV threshold to eliminate false events. This implies that implementations can provide high resolution scanning capabilities. A wide tuning range can also be used if the sensor 105 amplitude and frequency response exhibits changes greater than the threshold (e.g., false readings may occur). The range of delay tuning can be wide enough to cover the expected full path propagation delay changes over process, voltage, and temperature.

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

[0070] In some aspects, the calibration results may or may not use a clamping interval, and the technical solution may allow mode jump detection to be available in less than 1ns or 0.1ns from the start of the write operation, thus functionally covering the entire duration of the write mode. In some aspects, the system 600 may include a short clamping interval to relax the matching requirements of the compensation signal with the signal from the sensor 105, because the peak amplitude of the offset may occur at about the beginning of the R2W transition. In addition to increasing the HPC to a higher frequency (e.g., 20MHz), another effective clamping method may include shorting the input of the peak detector at the beginning of the write until the clamping interval ends. This additional technique may be combined with Fig.16 Table 1600 and Fig.17 The solution reflected in Table 1700 of , which shows the results of using a 20mV calibration threshold. Fig.13 , 16 From the results in Table Examples 1300, 1600, and 1700 of FIG. 17, we can see the tradeoff between compensation signal accuracy and suppression times of 0 ns, 50 ns, and 100 ns, respectively. Thus, a calibrated (e.g., optimal) solution may employ a compensation signal, calibration, and some programmable suppression intervals, with "no suppression" being an option.

[0071] Fig.18 is an example flow chart of a method 1800 for providing laser mode jump detection in a hard disk drive according to an embodiment of the present solution. The method 1800 may include actions 1805 to 1825, which may be used, for example, in conjunction with Figures 1 to 17A combination of systems 100 and 600 shown or described may be implemented. 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 of a memory device to a write operation of the memory device. The first circuit system may include a voltage generator that may generate 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., generated voltage signal) may include a first voltage corresponding to a read operation to a second voltage corresponding to a write operation. The difference between the first voltage and the second voltage may include a value of a voltage within a range between 10 mV and 100 mV. The value corresponding to the difference between the first voltage and the second voltage may be adjusted using a control signal 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 that receives a generated voltage signal from a voltage generator. The delay circuit may delay, time-shift, or time-shift the generated voltage signal for a duration of the first time period.

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

[0076] The method may include a delay circuit of the first circuit system using a first time period to align a time of a transition indicated by the second signal with a time of a transition indicated by a measurement from the sensor. For example, the first time period may be adjusted to match a delay of one or more circuits, such as a propagation delay of a preamplifier, a propagation delay of the sensor, or a propagation delay of any one or more of the following: the sensor, any of the filters, a peak detector, a voltage generator, a delay circuit, and / or an amplifier. The first time period may be a value in a range between 500 picoseconds and 10 microseconds. The 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 the first circuit system, the filter filtering out frequencies above a threshold from the delayed first signal according to a second time period of the frequency response of the filter to output a 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 a resistor and a capacitor, such as a resistor placed in parallel or in series with a capacitor. The filter may include a resistor and an inductor, such as a resistor placed in parallel or in series with an inductor. The filter may include a combination of a resistor, an inductor, and a capacitor, which may be arranged in parallel, in series, or in any combination of a combination of parallel and series arrangements.

[0078] The filter may include one or more frequency poles defined, set, or controlled based on its components or parts, such as its resistors, capacitors, and / or inductors. The filter may be a low pass filter that may attenuate, reduce, block, or filter out 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 the delayed first signal to cause it to rise from a lower voltage level to a higher voltage level that extends, expands, or spreads over a second time period defined by the frequency response of the filter. The second time period may correspond to a duration in which a change in the delayed voltage signal (e.g., a voltage signal generated by a time shift) is scaled in time or spread over time. The second time period may include or correspond to a duration in which a measurement from a sensor of the 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 an optical output of a laser of a storage device undergoing a transition and having a mode hop of the laser. The second circuit system may include any combination of a sensor, a conductor for a sensor, a filter (e.g., a low pass, band pass, or high pass filter), and / or an amplifier. The second circuit system may receive a measurement of the optical output of the laser by monitoring a portion of the optical output (e.g., a reflection of the optical signal). The storage device may undergo or be undergoing a transition, such as a read / write transition. The signal may indicate, undergo, or reflect a mode hop of the laser. The measurement may reflect, include, indicate, or be shaped based on at least a frequency response of the second circuit system. The frequency response of the second circuit system may correspond to a frequency response of the filter.

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

[0081] The received measurement may include a first portion and a second portion of the signal or measurement. The first portion 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 a read mode to a write mode of an HDD). The received measurement may include a second portion corresponding to a mode jump of the laser that occurs during or after the disturbance. The second portion may include, reflect, or indicate a mode jump event within a 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 0.1ns and 20us, such as a range of 20us, 10us, 5us, 3us, 2us, 1us, 0.5us, 0.3us, 0.2us, 0.1us, 50ns, 40ns, 20ns, 10ns, 1ns, or 0.1ns.

[0082] The method may include a sensor of a second circuit system that provides a signal of a sensor corresponding to an optical output of the laser. The signal may correspond to a specific fraction of the optical output of the laser, such as a portion of a laser beam or a measurement of a reflection of a 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 of the filter and a capacitor of the filter that configures a frequency response of the filter to match a frequency response of the second circuit system. The resistor may be coupled to an output of a delay circuit of 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 into the resistor. For example, the capacitor may have a value that is or corresponds to the inverse of 2π times a bandwidth of a sensor output or sensor measurement (e.g., 2*3.14159*bandwidth of the sensor response).

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

[0085] At 1825, the method may include subtracting the second signal from the measurement to output a third signal. The method may include a second circuit system subtracting the second signal from the measurement (e.g., from a sensor) to output a third signal identifying the occurrence of a mode hop of the laser. The second circuit system may include, for example, an amplification circuit or amplifier to combine the measurement signal and the second signal from the filter of the preamplifier. For example, the second circuit system may include a differential amplifier or a 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 the measurement to eliminate a first portion of the measurement identifying the occurrence of a mode jump of the laser from a (resulting) third signal. The second circuit system may subtract the sensor measurement from the second signal output from the filter of the preamplifier to eliminate a perturbation or artifact of the read / write transition from the sensor measurement signal, thereby generating a third signal in which a mode jump event may be detected. The mode jump of the laser may occur at any time after the start of the transition, for example within 0.6us, 0.3us, 0.1us, or 0.05us.

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

[0088] It should be noted that certain paragraphs of the present disclosure may refer to terms such as "first" and "second" in connection with a subset of transmission spatial streams, sounding frames, responses, and devices for the purpose of identifying or distinguishing one from another or otherwise. These terms are not intended to relate entities (e.g., first device and second device) only in time or according to a sequence, although in some cases, these entities may include such a relationship. These terms also do not limit the number of possible entities (e.g., delay circuits, filters, peak detectors) that can operate in a system or environment. It should be understood that the system described above may provide multiple of any one or each of those components, and these components may be provided on a stand-alone machine, or in some embodiments, on multiple machines in a distributed system. Further, bit field positions may vary, and multi-bit words may be used. In addition, the above-described systems and methods may be provided as one or more computer-readable programs or executable instructions embodied on or in one or more articles of manufacture (e.g., floppy disks, hard disks, CD-ROMs, flash memory cards, PROMs, RAMs, ROMs, or tapes). At least part of the technical solution may be implemented in any programming language (eg LISP, PERL, C, C++, C#) or in any bytecode language (eg JAVA). The software program or executable instructions may be stored as object code on or in one or more articles of manufacture.

[0089] Although the foregoing written description of the methods and systems enables one of ordinary skill in the art to make and use embodiments thereof, one of ordinary skill 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 the present disclosure.

Claims

1. A system comprising: a first circuit system for generating a first signal indicating a transition from a read operation of a memory device to a write operation of the memory device and delaying 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 output a second signal according to a second time period of a frequency response of the filter; second circuitry for receiving a measurement of an optical output of the laser of the storage device undergoing the transition and having a mode hop of the laser, the frequency response of the second circuitry being indicated by the measurement and corresponding to the frequency response of the filter; wherein the second circuit system is operable to subtract the second signal from the measurement to output a third signal identifying the occurrence of the mode hop of the laser.

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

4. The system according to claim 1, comprising: A delay circuit of the first circuitry is configured to align a time of the transition indicated by the second signal with a time of the transition indicated by the measurement using the first time period.

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

6. The system according to claim 1, comprising: a resistor of the filter, the resistor coupled to an output of the delay circuit of the first circuitry; and A capacitor of the filter has 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 circuitry.

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

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

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

10. The system of claim 1, wherein the measurement includes a first portion corresponding to a perturbation in the optical output of the laser caused by an increase in power input into the laser in response to the transition and a second portion corresponding to the mode hop of the laser occurring during or after the perturbation.

11. The 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 identifying an occurrence of the mode hop of the laser.

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

13. The system according to claim 1, wherein the third signal is input into a third circuit system, the third circuit system comprising at least: A bandpass filter, an amplifier, and a peak detector for detecting the occurrence of the mode hopping event in response to a peak value in a signal output from the amplifier and filtered by the bandpass filter exceeding a threshold of the peak detector.

14. A method comprising: generating, by a first circuit system, a first signal indicating a transition from a read operation of a memory device to a write operation of the memory device; delaying, by the first circuit system, the first signal according to a first time period; filtering frequencies above a threshold from the delayed first signal by a filter coupled to the first circuit system to output a second signal according to a second time period of a frequency response of the filter; receiving, by a second circuit system, a measurement of an optical output of the laser of the storage device undergoing the transition and having a mode hop of the laser, the measurement indicating a frequency response of the second circuit system corresponding to the frequency response of the filter; and The second signal is subtracted from the measurement by the second circuitry to output a third signal identifying the occurrence of the mode hop of the laser.

15. A method according to claim 14, wherein the first signal includes 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 time of the start of the transition, and wherein the difference between the first voltage and the second voltage is a value in a range between 1mV and 1000mV, which can be adjusted using a first control signal for controlling the first circuit system.

16. The method according to claim 14, 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 a range between 500 picoseconds and 20 microseconds, and the value can be adjusted according to a second control signal used to control the delay circuit of the first circuit system.

17. The method according to claim 14, comprising: configuring the frequency response of the filter to match the frequency response of the second circuit system by a resistor of the filter and a capacitor of the filter, wherein the resistor is coupled to an 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; providing, by a sensor of said second circuit system, a signal of said sensor corresponding to said optical output of said laser; and The signal of the sensor is amplified by an amplification circuit of the second circuit system and produces 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 corresponding to a duration in which the measurement from the sensor of the second circuit system transitions from a first level of the measurement corresponding to the read operation to a second level of the measurement corresponding to the write operation; and The measurement includes a first portion corresponding to a perturbation in the optical output of the laser caused by an increase in power input into the laser in response to the transition and a second portion corresponding to the mode hop of the laser occurring during or after the perturbation.

19. The method according to claim 14, comprising: The second signal is subtracted from the measurement by the second circuitry to eliminate a first portion of the measurement identifying an occurrence of the mode hop of the laser from the third signal, wherein the mode hop of the laser occurs within 1 microsecond after the start of the transition.

20. A storage device system, comprising: a voltage generator for generating a first signal indicating a transition from a read operation of a memory device to a write operation of the memory device; a delay circuit, configured 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 output a second signal according to a second time period of a frequency response of the filter; and Amplifiers for: receiving the second signal from the filter; receiving from a sensor a measurement of an optical output of the laser of the storage device undergoing the transition and having a mode hop of the laser, the measurement indicating a frequency response of the second circuitry that matches the frequency response of the filter; and The second signal is subtracted from the measurement to output a third signal identifying the occurrence of the mode hop of the laser.

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