Phase Plate Spatial Mode Overlap Reduction in MDM Systems
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Solution Overview
Problem
Conventional mode-division multiplexing (MDM) technologies face challenges in demultiplexing spatial modes with significant overlap, leading to deteriorated demultiplexing characteristics and low signal-to-noise ratios (SNR) when dealing with spatial modes whose orders are close to each other, limiting the potential capabilities of MDM communication systems.
Innovation Solution
An optical communication system that employs a phase plate to modulate the phases of signal light before entering a multiplex hologram recording section, reducing spatial overlap between spatial modes, thereby improving demultiplexing characteristics by using a phase plate with a spatial phase modulation distribution tailored to specific combinations of spatial modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spatial mode demultiplexing technologies (phase plate or planar lightwave circuit) are used, then spatial modes can be demultiplexed, but demultiplexing characteristics deteriorate when spatial modes have significant overlap, resulting in low signal-to-noise ratios
Solution Approach 1:
The patent changes the spatial distribution parameters of signal light by introducing a phase plate that applies spatial phase modulation. This transforms the intensity distribution of spatial modes to reduce overlap, thereby improving demultiplexing characteristics and signal-to-noise ratio when using conventional holographic demultiplexing technologies
Solution Approach 2:
The patent introduces a phase plate as an intermediary component between the multi-mode fiber and the holographic demultiplexer. This phase plate pre-modulates the spatial phases of signal light to reduce mode overlap, enabling better performance of the subsequent demultiplexing process
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
The solution enhances the demultiplexing characteristic for spatial modes with orders close to each other by approximately 5 dB to 10 dB, effectively bringing out the potential capabilities of MDM communication systems by reducing spatial overlap and improving SNR.
Implementation Method 1
a phase plate modulating phases of the respective plurality of spatial modes of the signal light so as to reduce a spatial overlap between the plurality of spatial modes
Implementation Method 2
interference fringes between spatial modes and reference light which propagates at a different angle are recorded in the hologram medium
Implementation Method 3
an optical fiber (a multi-mode fiber etc.) capable of transmitting signal light containing a plurality of spatial modes
Data Source
AI summary
An optical communication system is arranged to bring out potential capabilities of mode-division multiplexing (MDM). The optical communication system includes a hologram medium in which holograms are multiplex-recorded so as to correspond to respective spatial modes of signal light transmitted by a multi-mode fiber (MMF). A phase plate modulates phases of the respective spatial modes so as to reduce a spatial overlap between the spatial modes, and is provided on a side of the hologram medium on which signal light enters the hologram medium.