Orbital Angular Momentum Multiplexing in Optical Fibers
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Solution Overview
Problem
Current optical fiber communication methods face challenges in efficiently multiplexing multiple optical channels with different or same wavelengths without interference, particularly in maintaining independent trajectories and orbital angular momentum within a single fiber.
Innovation Solution
The method involves projecting light beams into an optical fiber at opposite angles within a numerical aperture, generating counter cyclical orbital angular momentum, allowing multiple beams to propagate in helical paths without interference, and using a segmented detector to distinguish between clockwise and counterclockwise rotating beams based on their orbital angular momentum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple light beams are launched into a single optical fiber at different incidence angles and positions, then spatial domain multiplexing is achieved and transmission capacity is improved, but interference between beams occurs and trajectory independence is compromised
Solution Approach 1:
The patent introduces orbital angular momentum as an additional degree of freedom for multiplexing. Instead of only using spatial position and launch angle, the invention adds the dimension of orbital angular momentum (OAM) to distinguish and separate multiple optical channels. This allows beams with different OAM values to propagate independently even when they share the same spatial path, resolving the interference problem while maintaining high transmission capacity.
Solution Approach 2:
The patent changes the parameter of orbital angular momentum to achieve beam separation. By assigning different OAM values (e.g., +1, -1, +2, -2) to different optical channels, the system can distinguish between beams that would otherwise interfere with each other. This parameter change enables independent trajectory maintenance through OAM conservation during propagation.
2Reliability
If light beams are projected at opposite angles within numerical aperture to achieve counter cyclical orbital angular momentum, then non-interfering propagation is achieved, but device complexity increases due to precise angle control requirements
Solution Approach 1:
The patent uses opposite angles of incidence to generate counter cyclical orbital angular momentum. By launching beams at symmetric opposite angles (e.g., +θ and -θ), the system naturally generates OAM states with opposite signs. This inversion approach simplifies the control mechanism because the symmetry automatically ensures non-interfering propagation without requiring complex active stabilization systems.
3Measurement precision
If segmented detectors are used to distinguish clockwise and counterclockwise rotating beams, then detection precision is improved, but manufacturing complexity increases
Solution Approach 1:
The patent employs segmented detectors divided into multiple sections (e.g., four quadrants) that can independently detect light intensity. Each segment measures the intensity of beams with specific orbital angular momentum directions. By comparing signals from different segments, the system can distinguish between clockwise and counterclockwise rotating beams with high precision. The segmentation approach is manufacturable using standard photodetector array technology.
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 simultaneous transmission of multiple optical channels with the same or different wavelengths in the same fiber, preserving bandwidth and allowing for non-interfering, counter-rotating helical paths with the same or complementary radii, facilitating efficient detection and data transmission.
Implementation Method 1
The respective multi-beam excitation and separation in a single optical fiber... each light beam is able to propagate independently according to its own trajectory inside the fiber... the projection of the light beam is in an annular ring with a respective radius dependent on the launch angle or skew angle
Implementation Method 2
a plurality of separate respective light beams are projected or inserted into an end of the optic fiber, with opposite angles of incidence or projection... The resultant light beams propagate with respective counter cyclical orbital angular momentum in respective helical paths in the longitudinal direction of the optic fiber
Implementation Method 3
using a segmented detector to distinguish between clockwise and counterclockwise rotating beams based on their orbital angular momentum
Data Source
AI summary
Multiple light beams are launched into a single optical fiber, each respective light beam with a corresponding signal. Each of the respective multi-beams are separated by launching each of the light at a different incidence angle and/or input position, into the optical fiber. In this way, each light beam is able to propagate independently according to its own trajectory inside the fiber. The resultant multi light beams propagate with respective counter cyclical orbital angular momentum with respective helical paths.