Repeaterless POADM Network Using Distributed Raman Amplification

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Solution Overview

Problem

Conventional optical communication networks employing wavelength division multiplexing (WDM) require optical amplifiers to compensate for loss, leading to increased costs and electrical power consumption at nodes, despite advancements in coherent detection technologies.

Innovation Solution

The implementation of repeaterless passive optical add/drop multiplexed network systems using distributed Raman amplification and remote optically pumped amplifiers (ROPAs) for inline optical amplification, eliminating the need for electrical power at amplifier sites and reducing active elements, along with special wavelength routing mechanisms to bypass optical pumps and minimize loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If optical amplifiers are used to compensate for loss in WDM networks, then link performance is maintained, but device complexity and cost increase due to active modules

Engineering Contradiction:

Improvelink performanceVSAvoidactive modules

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces active optical amplifiers with Raman scattering-based distributed amplification, where the fiber itself acts as the gain medium. This substitution eliminates the need for separate active amplifier modules while maintaining signal amplification, directly reducing device complexity and cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The optical fiber serves dual functions: as the transmission medium and as the gain medium through Raman scattering. The fiber automatically provides distributed amplification without requiring external active components, making the system self-sufficient and reducing the need for additional active modules.

Inventive Principle:

Principle #25Self-service

2Loss of energy

If optical amplifiers are deployed at nodes, then signal loss is compensated, but electrical power consumption increases significantly

Engineering Contradiction:

Improvesignal lossVSAvoidelectrical power

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The patent replaces electrically-powered optical amplifiers with a system that uses optical pumping through Raman scattering. High-power laser diodes pump the fiber, and the Raman effect converts this optical energy into distributed signal amplification along the fiber length, eliminating the need for electrical power at remote nodes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses periodic optical pumping with laser diodes to maintain distributed amplification along the fiber. The pump lasers operate continuously to sustain the Raman gain, providing steady-state signal compensation without requiring electrical power infrastructure at remote locations.

Inventive Principle:

Principle #19Periodic action

3Device complexity

If passive splitters are used for add/drop multiplexing, then device complexity is reduced, but signal loss increases due to splitting

Engineering Contradiction:

Improvepassive componentsVSAvoidsignal loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent combines passive optical splitting with distributed Raman amplification in a single system. The passive splitters maintain low device complexity while the simultaneously activated Raman amplification compensates for the splitting losses, achieving both simplicity and low loss.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The distributed Raman amplification provides continuous signal boosting along the entire fiber length, including at the points where passive splitters introduce loss. This continuous amplification ensures that signal levels are maintained throughout the network despite the presence of passive splitting components.

Inventive Principle:

Principle #20Continuity of useful action

4Adaptability or versatility

If ROADM nodes with configurable filtering are implemented, then wavelength routing flexibility is improved, but cost and device complexity increase

Engineering Contradiction:

Improvewavelength routing flexibilityVSAvoidconfigurable optical filtering

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces configurable optical filters and wavelength selective switches with coherent detection technology. Transponders at each node perform digital signal processing to selectively receive and route specific wavelengths, eliminating the need for physical optical filtering components while maintaining routing flexibility.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent moves the wavelength selection function from the optical domain (using filters and switches) to the digital domain (using coherent detection and digital signal processing). This dimensional shift from optical to electrical/digital processing provides routing flexibility without requiring complex optical filtering hardware.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS10404398B2Repeaterless passive optical add/drop multiplexed fiber network

Publication Date: 2019.09.03 NEC CORP

AI summary

Aspects of the present disclosure describe systems, methods, and structures for passive optical add/drop multiplexing (POADM) architectures that remove the prior art requirement of an optical amplifier (i.e., repeater-less) at the POADM nodes.