Coherent Optical Receiver Simplification Through Alamouti Polarization Coding

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Solution Overview

Problem

Coherent optical receivers with dual polarization structures face challenges in reducing complexity, cost, and integration due to the use of numerous optical components and difficulty in integrating polarization components, exacerbated by random polarization changes in optical fibers.

Innovation Solution

Implementing a polarization time block coding scheme using an Alamouti code to encode symbols in the time domain, allowing for a single polarization structure in the coherent optical receiver, which reduces the number of optical components and simplifies the digital signal processing by using a multi-tap or single-tap digital filter configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a dual polarization structure is used in the coherent optical receiver to handle random polarization changes, then the receiver can receive signals regardless of polarization state, but the number of optical components increases and integration becomes difficult

Engineering Contradiction:

Improvepolarization state reception capabilityVSAvoidnumber of optical components

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by performing polarization encoding at the transmitter before signal transmission. The polarization time block code encodes two adjacent symbols in the time domain to be orthogonal for X and Y polarization modes, preparing the signal in advance so that the receiver only needs a single polarization structure to decode it, avoiding the need for dual polarization reception components

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses copying by creating orthogonal copies of signal symbols through polarization encoding. The Alamouti code generates orthogonal signal representations that can be transmitted through different polarization modes, allowing the receiver to reconstruct the original signal using only a single polarization channel instead of requiring both polarization channels

Inventive Principle:

Principle #26Copying

2Adaptability or versatility

If a dual polarization structure is used in the coherent optical receiver, then the receiver can handle polarization changes, but the cost increases due to many optical components

Engineering Contradiction:

Improvepolarization diversity functionVSAvoidimplementation cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The polarization time block code performs preliminary polarization encoding at the transmitter, organizing signal symbols into orthogonal pairs that can be transmitted through a single polarization channel. This preliminary action eliminates the need for expensive dual polarization reception components at the receiver端

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts the polarization handling function from the receiver and relocates it to the transmitter through polarization encoding. By taking out the polarization diversity requirement from the receiver side and implementing it at the transmitter through Alamouti coding, the system eliminates the need for multiple polarization-sensitive optical components in the receiver

Inventive Principle:

Principle #2Taking out (Extraction)

3Volume of moving object

If polarization components are integrated in the coherent optical receiver, then the receiver size may be reduced, but integration difficulty increases due to component compatibility issues

Engineering Contradiction:

Improvereceiver sizeVSAvoidintegration difficulty

Core Design Contradiction:

Volume of moving objectVSEase of manufacture

Solution Approach 1:

The polarization time block code performs preliminary encoding that simplifies the receiver structure to a single polarization channel, eliminating the need to integrate multiple polarization components. This preliminary action at the transmitter side avoids the integration challenges that would arise from combining multiple polarization-sensitive components in the receiver

Inventive Principle:

Principle #10Preliminary action

4Measurement precision

If multiple digital filters and channel equalizers are used in the polarization time block code decoder, then decoding accuracy is improved, but the complexity of the coherent optical receiver increases

Engineering Contradiction:

Improvedecoding accuracyVSAvoidnumber of digital filters

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The polarization time block code performs preliminary orthogonal encoding that simplifies the decoding process. The orthogonal structure of the encoded symbols allows for simpler digital signal processing with fewer filters and equalizers compared to conventional decoding methods, reducing receiver complexity while maintaining decoding accuracy

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12438621B2Coherent optical communication system using polarization time block code

Publication Date: 2025.10.07 ELECTRONICS & TELECOMM RES INST

AI summary

Provided is a coherent optical communication system including a coherent optical transmitter and a coherent optical receiver, and more particularly, when a polarization time block code is used, the complexity for performing a polarization time block decoding scheme of the coherent optical receiver is minimized.