Optical Fiber Coupling Stability Without Position Detector
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Solution Overview
Problem
Existing methods for coupling spatial light to optical fibers in coherent laser communication systems require position detectors, which complicates the process and reduces efficiency, especially in long-distance, high-code-rate, miniaturized, lightweight, and low-power applications.
Innovation Solution
A method and device that utilize mode field matching, a four-point tracking algorithm, and fiber nutation to calculate and correct position deviations without a position detector, ensuring a stable optical axis and high coupling efficiency through an optical fiber coupler and a two-dimensional fast scanning galvanometer, using amplified orthogonal sine signals and a drive signal control board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position detector is used to couple spatial light to optical fiber, then coupling efficiency can be monitored and optimized, but the device complexity increases and the system becomes more cumbersome
Solution Approach 1:
The patent removes the position detector from the coupling system entirely. Instead of using external detection equipment, the system uses the optical signal itself (through fiber nutation and four-point tracking algorithm) to determine alignment status and guide adjustments, achieving coupling optimization without additional detection hardware
Solution Approach 2:
The system uses its own optical signal and fiber nutation characteristics to perform self-diagnosis and self-alignment. The fiber coupling system monitors its own coupling efficiency through the nutation signal variations and automatically adjusts the galvanometer to maintain optimal alignment, eliminating the need for separate position detectors
2Measurement precision
If traditional coupling methods with position detectors are used, then alignment can be achieved, but the system weight increases and power consumption increases
Solution Approach 1:
The patent eliminates heavy position detector components and their associated support structures, power supplies, and signal processing equipment. The alignment function is achieved through lightweight software algorithms (four-point tracking) processing optical signal variations, dramatically reducing terminal weight while maintaining alignment precision
3Measurement precision
If traditional coupling methods with position detectors are used, then alignment can be achieved, but the system power consumption increases
Solution Approach 1:
The patent removes power-hungry position detectors, their signal processing circuits, and associated electronics. The optical axis stability is maintained through low-power software-based four-point tracking algorithms that analyze natural fiber nutation signals, eliminating the need for continuous active detection and significantly reducing power consumption
Solution Approach 2:
Instead of continuous monitoring and adjustment, the system uses periodic fiber nutation excitation combined with four-point sampling. This intermittent measurement approach, performed at specific phases of the nutation cycle, maintains optical axis stability with minimal power consumption compared to continuous detection systems
4Device complexity
If the system structure is simplified by removing position detectors, then miniaturization is achieved, but maintaining high coupling efficiency becomes more difficult
Solution Approach 1:
The patent implements a feedback mechanism using fiber nutation signals. The four-point tracking algorithm continuously monitors coupling efficiency variations during nutation and provides feedback to the galvanometer control system, which automatically adjusts the spatial light position to maintain optimal coupling, achieving high precision without complex external detection equipment
Solution Approach 2:
The system transitions from static alignment to dynamic alignment maintenance. By exciting fiber nutation and using real-time signal analysis with the four-point tracking algorithm, the system dynamically adjusts the galvanometer to compensate for drift and environmental changes, maintaining high coupling efficiency in a simplified structure
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 enables high-efficiency coupling of spatial light to optical fibers without a position detector, providing a stable optical axis, simple structure, reliable performance, strong background light filtering, and improved anti-interference capabilities, enhancing the quality of spatial light communication channels.
Implementation Method 1
according to the principle of fiber nutation, a four-point tracking algorithm is used to calculate the fiber nutation trajectory
Implementation Method 2
the two-dimensional fast scanning galvanometer is deflected to two preset positions in x-direction and y-direction under constant voltage
Data Source
AI summary
An apparatus and method herein efficiently couple spatial light to optical fiber light for achieving stability of an optical axis without a position sensor. The basic concept of the method includes: first, obtaining, according to a theoretical coupling efficiency model, a model parameter by means of fitting calculation; second, using a four-point tracking algorithm to calculate an optical fiber nutation trajectory according to the optical fiber nutation principle; and finally, using the nutation trajectory to calculate the position deviation of a central point. The optical axis is ensured to be stable by correcting the position deviation, and the high coupling efficiency remains. The method is used for the stability of the optical axis in a space coherent laser communication DPSK link. The high efficiency coupling is a key technology of long-distance, high bit rate transmission in space laser communication, and is significant in the development of inter-satellite optical communications.