Self-adapting Phasing Device for Fiber Optical Amplifiers
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Solution Overview
Problem
High-power fiber lasers face limitations in beam quality and temporal coherence due to nonlinear effects and damage from guided mode dimensions, with existing phase measurement and correction methods becoming complex and costly as power increases, and are not applicable in cascaded amplification systems where optical isolators prevent probe propagation.
Innovation Solution
A self-adaptive technique using a probe beam co-propagated with the signal, differentiated by temporal differentiation, allowing phase pre-compensation at low optical power and minimizing modulator constraints, compatible with cascaded fiber amplifiers and high channel counts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a probe beam is used to measure phase in traditional counter-propagation systems, then phase measurement is possible, but the method becomes inapplicable in cascaded amplification systems with optical isolators
Solution Approach 1:
The patent inverts the traditional counter-propagation approach by implementing co-propagation of probe and signal beams through the amplification stages. This inversion allows the probe beam to pass through optical isolators in the same direction as the signal, making the system compatible with cascaded amplification architectures while maintaining phase measurement capability
Solution Approach 2:
The patent employs periodic modulation of the probe beam intensity to distinguish it from the signal beam during co-propagation. By modulating the probe beam at a specific frequency and using synchronous detection, the system can extract phase information even when both beams travel together through the amplification stages
2Manufacturing precision
If active phase compensation with feedback loops is used, then phase correction is achieved, but the measurement and control system becomes complex and expensive
Solution Approach 1:
The patent implements a self-adaptive phase compensation system where the probe beam automatically measures the phase distribution, and the spatial light modulator directly applies the necessary correction without requiring complex external measurement and control systems. The system serves itself by using the probe beam's own interaction with the amplification media to generate the correction signal
Solution Approach 2:
The patent extracts only the essential phase information from the probe beam using simple interference measurement with a reference beam, avoiding the need for complex wavefront sensing systems. By separating the phase measurement function from the signal amplification function, the system achieves beam quality correction with minimal added complexity
3Adaptability or versatility
If probe and signal beams are co-propagated, then compatibility with cascaded amplifiers is achieved, but differentiation of probe from signal at output becomes difficult
Solution Approach 1:
The patent modulates the probe beam intensity periodically at a known frequency during its co-propagation with the signal beam through the amplification stages. At the output, synchronous detection at this modulation frequency allows easy differentiation and extraction of the probe beam signal from the much stronger signal beam, solving the identification problem
Solution Approach 2:
The patent applies preliminary intensity modulation to the probe beam before it enters the amplification system. This pre-encoded temporal signature allows the probe beam to be easily distinguished from the unmodulated signal beam at the output, even though they travel together through the same optical path
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
Enables efficient phase compensation across multiple amplification stages with reduced modulator constraints and power losses, maintaining high beam quality and coherence, even in high-power systems with cascaded amplifiers.
Implementation Method 1
means for causing the probe beam and the reference beam to interfere at the output of all of the amplifying fibers so as to define an interferogram
Implementation Method 2
a spatial phase modulator supplied by said digital hologram for diffracting in order -1 the beam called the signal at the input of the set of amplifying fibers
Data Source
Figure 1~2
Figure 3
AI summary
The device has a co-propagation unit to alternatively co-propagate a probe beam (R1) and a signal beam (R3) into amplifying fibers (30), and an interfering unit to interfere the probe and the signal beams at output of the fibers so as to define an interferogram. A matrix detector (50) e.g. charge coupled device matrix sensor, generates a digital hologram from the interferogram. A spatial phase modulator (60) i.e. LCD modulator, is supplied with the hologram to diffract the signal beam in order of 1 at input of the fibers. The modulator has cooling rate characteristics of phase law.