Multi-Channel Optical Phase Locking Controller for Vibration Noise
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Solution Overview
Problem
Existing multi-channel phase-locking controllers for coherent beam combined fiber laser arrays are limited in scalability to high control speeds and channel counts due to the limited information content of a single beam sample, particularly in vibrationally noisy environments where internal phase noise is overshadowed by platform-induced vibrational noise.
Innovation Solution
A high-speed multi-channel optical phase locking controller that modifies each input using a setpoint and dither magnitude, with measurements taken before and after dither application to calculate adjustment values, updating setpoints and dither magnitudes to optimize output characteristics, allowing for accurate phase-locking of large arrays without vibration isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing multi-channel phase-locking controllers (such as LOCSET or SPGD) are used, then internal phase noise can be suppressed, but controller bandwidth is limited to only a few tens of krad/s and cannot handle high-level vibrational noise
Solution Approach 1:
The patent segments the control problem by separating the estimation of vibrational noise characteristics from the phase-locking control. The vibrational noise parameters (amplitude, frequency, phase) are estimated independently using accelerometer data and signal processing, then used to generate compensating dither signals. This segmentation allows the controller to operate at high bandwidth by reacting to predicted vibrations rather than waiting for phase errors to manifest.
Solution Approach 2:
The patent applies preliminary action by using accelerometers to detect and characterize vibrational noise before it significantly impacts the laser phases. The system pre-computes compensating dither signals based on measured vibration characteristics, allowing the phase-locking controller to proactively counteract vibrations rather than reactively correcting phase errors after they occur. This preliminary characterization enables the system to maintain phase-locking accuracy in high-vibration environments.
2Quantity of substance
If the number of laser channels is increased to improve beam combining power, then the information content of a single beam sample becomes insufficient and controller scalability is limited
Solution Approach 1:
The patent introduces accelerometers as intermediary sensors that measure platform vibrations independently of the optical beam samples. These vibrational measurements serve as a mediator that provides information about phase disturbances affecting all laser channels, allowing the controller to infer and compensate for phase errors without requiring additional direct optical measurements from each channel. This intermediary measurement approach enables scalability to high channel counts.
Solution Approach 2:
The patent changes the measurement parameters by shifting from direct optical phase measurements (which have limited information content) to mechanical vibration measurements using accelerometers. By measuring the root cause (platform vibrations) rather than the effect (optical phase errors), the system gains richer information about the disturbance characteristics, enabling effective control of large numbers of channels through parameter transformation.
3Reliability
If dither magnitudes are increased to improve phase-locking in vibration environments, then convergence time increases and control stability deteriorates
Solution Approach 1:
The patent applies dynamics by making the dither magnitudes adaptive rather than static. The dither signal parameters (amplitude, frequency, phase) are dynamically adjusted based on real-time vibration measurements and the current phase-locking error. During transient conditions or high vibration, larger dither magnitudes improve robustness, while during stable operation, smaller magnitudes reduce convergence time and maintain stability. This dynamic adaptation resolves the trade-off between robustness and convergence speed.
Data Source
AI summary
An output characteristic of a monotonic system is controlled using a plurality of adjustable inputs. The adjustments are controlled using a set of setpoints and a set of dither magnitudes. Each input's adjustment is controlled simultaneously using a setpoint and a dither around the setpoint. The dither values for each input have a zero mean and there is zero correlation between the dithers applied to different inputs. The changes in the output characteristic that result from the dithers are measured, and are used to create an adjustment value. The adjustment value is used to create a set of adjusted dither magnitudes. The set of adjusted dither magnitudes are added to a set of integrated prior adjusted dither magnitudes to create a set of setpoint adjustments. Adding the setpoint adjustments to corresponding setpoints creates a set of updated setpoints. This process is repeated so that the setpoints converge on a value that maximizes the output characteristic being controlled.