Mode Permutation Unit for Optical Signal Dispersion

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Solution Overview

Problem

Existing optical transmission systems experience information errors due to mode dispersion when using digital signal processing for signal division in mode multiplexing optical transmission.

Innovation Solution

An optical transmission system with mode permutation units that cyclically permute modes among multiple optical signals, allowing for improved signal separation and reduction of errors by interchanging modes used in the transmission path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If digital signal processing is used for signal division in mode multiplexing optical transmission, then signal processing capability is improved, but information errors occur due to mode dispersion

Engineering Contradiction:

Improvesignal processing capabilityVSAvoidinformation accuracy

Core Design Contradiction:

Extent of automationVSReliability

Solution Approach 1:

The mode permutation unit performs mode permutation on optical signals before they are transmitted through the transmission path. By pre-permuting the modes, the system prepares the signals in advance to counteract the effects of mode dispersion that will occur during transmission, thereby reducing information errors at the receiver without requiring complex post-processing corrections

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The mode permutation unit acts as an intermediary device between the signal source and the transmission path. It transforms the optical signals by permuting modes before transmission, serving as a mediator that modifies the signal characteristics to be more resilient to mode dispersion effects in the transmission medium

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If mode multiplexing is used to increase communication capacity, then productivity is improved, but mode dispersion causes signal separation errors

Engineering Contradiction:

Improvecommunication capacityVSAvoidsignal separation accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

By performing mode permutation before transmission, the system pre-configures the modal distribution of multiplexed signals to minimize the impact of mode dispersion. This preliminary arrangement ensures that even as modes disperse during transmission, the original signals can be more accurately recovered at the receiver

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The mode permutation unit changes the modal parameters of optical signals by interchanging modes before transmission. This parameter transformation modifies how signals propagate through the transmission medium, making them less susceptible to mode dispersion-induced separation errors while maintaining high communication capacity

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11101914B2Optical transmission system and optical transmission method

Publication Date: 2021.08.24 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

An optical transmission system includes a plurality of transmission paths that transmit a mode multiplexing signal, and one or more mode permutation units provided between the transmission paths. The mode permutation unit performs mode permutation to interchange modes to be used between at least some optical signals among respective optical signals of a plurality of types of modes that are multiplexed to the mode multiplexing signal input from the transmission path on an input side, and outputs the mode multiplexing signal subjected to the mode permutation to the transmission path on an output side.