Single-End Optical Fiber Transfer Matrix Measurement
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Solution Overview
Problem
Current methods for characterizing mode coupling in optical fibers require access to both ends for transfer matrix measurement, making them time-consuming and cumbersome, especially in non-telecom applications where fiber disturbances are common, and do not allow for efficient single-end measurements.
Innovation Solution
The use of spatial pilots, varying in time and/or frequency, to differentiate spatial and polarization propagation modes at a single end of the optical fiber, enabling measurement of the mode transfer matrix for both propagation directions without the need for dual-end access, utilizing compact spatial multiplexers, optical delay lines, and frequency filtering to separate and reflect modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual-end access is used for transfer matrix measurement, then measurement accuracy is improved, but measurement time and operational complexity increase
Solution Approach 1:
The patent inverts the conventional dual-end measurement approach by performing transfer matrix measurement from a single end. It uses round-trip propagation where light travels forward through the optical fiber, reflects at the far end, and returns backward to the measurement end, enabling single-end characterization of mode coupling in both propagation directions
Solution Approach 2:
The patent introduces spatial pilots as intermediary signals with distinct spatial profiles that facilitate mode coupling characterization. These spatial pilots serve as mediators between the single measurement end and the fiber's mode structure, enabling extraction of transfer matrix information without requiring physical access at both ends
2Measurement precision
If dual-end access is used for transfer matrix measurement, then complete mode coupling characterization is improved, but device complexity and ease of operation worsen
Solution Approach 1:
The patent makes the single measurement end perform multiple functions: it launches spatial pilots, receives reflected signals, and characterizes mode coupling in both forward and backward propagation directions. This multi-functional approach eliminates the need for separate measurement systems at both ends, reducing overall device complexity
3Productivity
If spatial pilots are used for single-end measurement, then measurement efficiency is improved, but signal processing complexity increases
Solution Approach 1:
The patent segments the optical signal into distinct spatial modes using spatial pilots with different lateral intensity profiles. Each spatial pilot corresponds to a specific mode or mode combination, allowing independent characterization of mode coupling effects. This segmentation enables efficient extraction of transfer matrix elements through spatial mode decomposition of the reflected signal
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 single-end measurement of the optical fiber's mode transfer matrix, allowing for improved data recovery and transmission capacity in SDM systems by compensating for mode coupling, reducing the complexity of receivers and enhancing transmission capacity without increasing hardware complexity.
Implementation Method 1
Space-division multiplexing (SDM) employs optical propagation modes with different lateral intensity and/or phase profiles in a multimode optical fiber (MMF) or multicore optical fiber (MCF)
Data Source
AI summary
Various embodiments relate to a method including: coupling one or more optical spatial pilot signals into a first end of optical fiber, wherein the optical fiber is a multimode optical fiber; Reflecting and modifying each mode of the optical pilot signals at a second end of the optical fiber; receiving a reflected portion of the one or more optical spatial pilot signals at the first end of the of the optical fiber in response to the reflected portion having propagated through the optical fiber in both directions; processing the reflected spatial pilot to determine components of one of a round-trip transfer matrix of the optical fiber and a single-direction transfer matrix of the optical fiber.