All-Optical Mode Division Demultiplexing via Coherent Detection
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Solution Overview
Problem
Mode coupling in multimode optical fibers leads to signal scrambling, which existing technologies like MIMO communication with coherent transmission and electronic compensation struggle to effectively address due to complex component requirements.
Innovation Solution
A system and methodology that decodes N superimposed coherent optical transmission modes by measuring output principal states and vector field matrices using coherent detection hardware and digital signal processors, allowing for the extraction of input signals without the need for time-dependent multiplexing and demultiplexing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MIMO communication with coherent transmission and electronic compensation is used to address mode coupling, then signal scrambling can be handled, but device complexity increases due to extensive fast forward error correction and electronic compensation requirements
Solution Approach 1:
The patent replaces complex electronic compensation systems with an all-optical solution using mode selective switches and optical circulators. The mechanical/optical switching mechanism substitutes for extensive electronic signal processing, achieving mode demultiplexing through optical path routing rather than electronic compensation algorithms.
Solution Approach 2:
The patent divides the demultiplexing process into N separate time slots, with each mode being switched to a different output port in sequential time slots. This temporal segmentation allows simple optical switches to achieve what would otherwise require complex simultaneous processing of all modes.
2Reliability
If principal states approach is used to limit mode coupling, then signal scrambling is reduced, but device complexity increases due to complex components needed for generating, combining, and splitting states
Solution Approach 1:
The patent replaces complex principal state generation and manipulation components with mode selective switches that operate in the time domain. Instead of generating and maintaining complex principal states through sophisticated optical components, the system uses simple switching mechanisms to achieve mode separation.
Solution Approach 2:
The patent introduces time-dependent switching dynamics to achieve mode demultiplexing. The mode selective switches dynamically route different modes to different output ports based on time slot, replacing static complex optical components with dynamic simple switching elements.
3Reliability
If time-dependent multiplexing and demultiplexing components are used to decode modal signals, then signal extraction is achieved, but device complexity and difficulty of control increase
Solution Approach 1:
The patent segments the signal transmission into N distinct time slots, with each time slot dedicated to transmitting a specific mode to a specific output port. This temporal segmentation simplifies control logic, as each switch only needs to route one mode at a time rather than managing all modes simultaneously.
Solution Approach 2:
The patent employs periodic switching action where mode selective switches cycle through different modes in a predetermined sequence. This periodic operation simplifies control compared to arbitrary time-dependent switching, as the switching pattern repeats regularly and can be easily synchronized.
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
Effectively deconvolves N output modes, reducing the complexity of signal processing and eliminating the need for time-dependent multiplexing and demultiplexing components, thereby improving signal clarity and transmission efficiency in multimode optical fibers.
Implementation Method 1
Multimode optical fibers have been introduced to increase transmission capacity in optical communications networks
Implementation Method 2
utilizing the coherent detection hardware to measure the phase and amplitude of the output optical signals as a vector field matrix
Data Source
Figure 1
AI summary
Methods of decoding N superimposed coherent optical transmission modes transmitted along a multimode optical fiber are provided where the optical signal detector comprises coherent detection hardware and a digital signal processor. The optical signals are split into N optical detection channels of the coherent detection hardware, which is used to measure the phase and amplitude of the output optical signals as a vector field matrix [ê]1 xn . The digital signal processor determines the output principal states [PS out ] 1xn of the output optical signals from the principal state eigenvectors of an output matrix corresponding to the N propagating optical signals at the receiving portion of the data transmission link and extracts the input optical signals [M]In from the output optical signals using the output principal states [PS out ] 1xn , the vector field matrix [ê] 1xn of the output optical signals, and a time delay τ of each output signal. Optical signal receivers for the execution of the methodology disclosed and contemplated herein are also provided.