Asymmetric Optical Power Splitters for Polarization Loss Compensation

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Solution Overview

Problem

The integration of polarization multiplexing optical transmission and reception circuits faces challenges due to excessive loss caused by asymmetric branching ratios in optical power splitters, which complicates the distribution of optical power and results in unbalanced losses depending on the polarization path, especially when trying to minimize circuit size and power consumption.

Innovation Solution

The use of optical power splitters with a minimum asymmetry branching ratio to compensate for unbalanced losses between polarization paths, optimizing the distribution of optical power among transmission and reception circuits, and integrating these components onto a single chip using silicon light waveguides to achieve superior loss characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If optical power splitters with asymmetric branching ratios are used to distribute optical power to transmission and reception circuits, then the optical power distribution is optimized, but excessive loss and unbalanced losses between polarization paths occur

Engineering Contradiction:
Improveoptical power distributionVSAvoidoptical loss
Core Design Contradiction:
PowerVSLoss of energy

Solution Approach 1:

The patent applies asymmetry by using optical power splitters with asymmetric branching ratios (e.g., 70:30 or 80:20) rather than symmetric 50:50 splitting. This asymmetric design compensates for the inherent unbalanced losses between polarization paths in integrated circuits, where one polarization path typically experiences higher loss than the other. By adjusting the branching ratio asymmetrically, the patent optimizes optical power distribution to account for these differential losses, ensuring balanced signal levels at the output despite the asymmetric power division.

Inventive Principle:
Principle #4Asymmetry

2Loss of energy

If optical power splitters with high asymmetry branching ratios are used to compensate for unbalanced losses, then loss compensation is achieved, but the complexity of optimizing power distribution increases

Engineering Contradiction:
Improveloss compensationVSAvoidpower distribution optimization
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The patent employs parameter changes by systematically varying the branching ratios of optical power splitters to achieve optimal loss compensation. Different embodiments use different asymmetric ratios (70:30, 80:20, etc.) depending on the specific loss characteristics of the polarization paths. This parameter optimization approach allows the system to compensate for unbalanced losses while maintaining a relatively simple structure, as the complexity is confined to the selection and adjustment of splitter ratios rather than requiring complex active control mechanisms.

Inventive Principle:
Principle #35Parameter changes

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

This approach allows for the compensation of unbalanced losses and optimal power distribution, resulting in a more efficient and integrated polarization multiplexing optical transmission and reception circuit with improved loss characteristics, enhancing the performance of digital coherent polarization multiplexing methods.

Implementation Method 1

a first optical power splitter for branching the optical power of continuous light outputted from a light source

Methodology Applied
Scientific EffectOptical power splitting:

Implementation Method 2

The optical modulator 9103 receives a transmission electric signal and a continuous light from the light source 9101 branched by the first optical power splitter 9102. The optical modulator 9103 functions as a polarization multiplexing optical transmission circuit to modulate the continuous light based on the transmission electric signal

Methodology Applied
Scientific EffectOptical modulation:

Implementation Method 3

a polarization beam combiner connected to the polarization rotation circuit and an output of the other polarization optical modulation circuit, and outputting polarization multiplexing modulation light

Methodology Applied
Scientific EffectPolarization beam combining:

Implementation Method 4

The optical demodulator 9104 receives a polarization multiplexed signal light from the transmission path and a continuous light from the light source 9101 branched by the first optical power splitter 9102. The optical demodulator 9104 functions as the polarization multiplexing optical reception circuit that performs a coherent optical demodulation processing

Methodology Applied
Scientific EffectCoherent detection:

Implementation Method 5

a photo detector connected to an output of the first optical coherent mixer; and a photo detector connected to an output of the second optical coherent mixer

Methodology Applied
Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentEP3285420B1Polarization multiplexing optical transmission circuit and polarization multiplexing optical reception circuit
Publication Date: 2020.05.06 NIPPON TELEGRAPH & TELEPHONE CORP
  • EP3285420B1 patent drawingFigure 1
  • EP3285420B1 patent drawingFigure 2
  • EP3285420B1 patent drawingFigure 3

AI summary

A one chip-integrated digital coherent polarization multiplexing optical transmission and reception circuit with optimal optical power distribution between sending and receiving is provided by using an optical power splitter having a branching ratio of a lower asymmetry property so that the unbalanced loss depending on the polarization path can be compensated. A polarization multiplexing optical transmission and reception circuit includes a polarization multiplexing optical transmission circuit, including: the first optical power splitter for branching the optical power of continuous light outputted from a light source; one polarization optical modulation circuit at the side of a path having a higher loss connected to one output of the first optical power splitter; the second optical power splitter connected to the other output of the first optical power splitter; and the other polarization optical modulation circuit connected to one output of the second optical power splitter.