Preamplifier Laser Current Calibration for HAMR BER
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Solution Overview
Problem
Current heat-assisted magnetic recording (HAMR) systems face challenges in optimizing laser current settings for optimal Bit Error Rate (BER) performance during data writing, as various factors such as write current waveform and total laser current impact BER, and existing calibration methods are not efficient in dynamically adjusting these parameters.
Innovation Solution
A preamplifier circuit and method for fine laser current calibration, which configures the laser current to multiple settings, detects gaps in the write power signal, and adjusts the laser current and write heater current to maintain optimal fly height and BER performance by writing and reading data at various settings, selecting the optimal laser current based on average BER analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser current is increased to improve write power and BER performance, then Bit Error Rate performance is improved, but fly height stability deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting laser current based on detected fly height conditions. The system monitors fly height and modifies laser current parameters accordingly - increasing current when fly height is excessive to improve BER, while decreasing current when fly height is appropriate to maintain stability. This dynamic parameter adjustment resolves the contradiction between BER performance and fly height stability.
Solution Approach 2:
The patent implements feedback control by continuously monitoring fly height during writing operations and using this information to adjust laser current. The system detects fly height variations and feeds this information back to the laser current control mechanism, creating a closed-loop system that automatically balances BER performance requirements with fly height stability requirements.
2Reliability
If laser current is dynamically adjusted to optimize BER, then BER performance is improved, but system complexity increases
Solution Approach 1:
The patent applies universality by integrating multiple functions into the fly height detection system. The same system that detects fly height for positioning purposes is also used to trigger laser current adjustments for BER optimization. This multi-functional approach allows BER optimization without requiring a separate dedicated calibration system, thereby limiting the increase in system complexity.
Solution Approach 2:
The patent implements self-service by enabling the system to automatically adjust laser current based on its own fly height detection capabilities. The system uses its inherent fly height monitoring functionality to self-regulate laser current parameters, eliminating the need for external calibration equipment or complex additional control systems.
3Measurement precision
If multiple laser current settings are used for calibration, then calibration precision is improved, but calibration time increases
Solution Approach 1:
The patent applies preliminary action by performing fly height detection and laser current optimization during the normal writing operation itself. Rather than conducting separate calibration procedures before writing, the system uses the writing process as the calibration opportunity, detecting fly height and adjusting current in real-time. This eliminates dedicated calibration time while maintaining precision through multiple current setting evaluations.
Solution Approach 2:
The patent implements continuity of useful action by ensuring that the calibration process does not interrupt the writing operation. The system continuously performs fly height detection and laser current optimization throughout the writing process, making the calibration action continuous rather than discrete. This allows multiple current settings to be evaluated without stopping or pausing the productive writing activity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise calibration of laser current settings, improving BER performance and maintaining consistent fly height, thereby enhancing the overall data writing efficiency and areal data density in HAMR systems.
Implementation Method 1
Current heat-assisted magnetic recording (HAMR) systems face challenges in optimizing laser current settings
Data Source
AI summary
Systems and methods of laser bias calibration are presented. A preamplifier circuit may configure a laser current supplied to a laser emitter to be a first laser current of the plurality of laser currents during the writing of one or more first sectors. The preamplifier may further detect one or more gaps in a write power signal while the laser current of the laser emitter is configured to be the first laser current. In response to the detection of the one or more gaps in the write power signal, the preamplifier may configure the laser current supplied to the laser emitter to be a second laser current of the plurality of laser currents during the writing of one or more second sectors. The preamplifier circuit may be utilized in a heat assisted magnetic recording device.