Integrated Polarization Splitter Rotator PDL Tuning

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Solution Overview

Problem

Current optical waveguide devices with polarization splitters and rotators suffer from high insertion loss, wavelength sensitivity, and increased component complexity, which degrades polarization extinction ratio and increases device footprint, limiting their efficiency in long-haul optical transmission systems.

Innovation Solution

The development of an integrated optical device with a high-index contrast semiconductor waveguide structure, featuring a tapered rotator and Y-splitter configuration that rotates TE0 mode to TE1 mode and splits both TE0 and TE1 modes into distinct portions, eliminating the need for directional couplers and reducing polarization-dependent loss through a PDL tuning section.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional polarization splitters and rotators are used, then polarization handling is achieved, but insertion loss increases and device footprint increases

Engineering Contradiction:

Improvepolarization extinction ratioVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent combines the polarization splitter and polarization rotator into a single integrated device. The splitter separates orthogonal polarizations while the rotator simultaneously rotates the polarization state of one output, eliminating the need for separate components and reducing overall insertion loss.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated device performs multiple polarization handling functions (splitting and rotating) within a single component structure. This multi-functionality reduces the number of components needed in the optical system, thereby reducing total insertion loss and device footprint.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If conventional polarization splitters and rotators are used, then polarization handling is achieved, but device footprint increases

Engineering Contradiction:

Improvepolarization extinction ratioVSAvoiddevice footprint

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

3Ease of operation

If directional couplers are used in polarization handling, then polarization splitting is achieved, but component complexity increases

Engineering Contradiction:

Improvepolarization splittingVSAvoidcomponent complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the directional coupler from the polarization handling system. By using an integrated splitter-rotator design based on different coupling mechanisms, the complex directional coupler component is removed, simplifying the overall system architecture.

Inventive Principle:

Principle #2Taking out (Extraction)

4Adaptability or versatility

If broadband performance is achieved, then wavelength range is extended, but polarization extinction ratio may degrade

Engineering Contradiction:

Improvewavelength rangeVSAvoidpolarization extinction ratio

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent employs parameter changes in the waveguide structure (such as varying width, height, or material composition along the propagation direction) to achieve broadband operation. These gradual parameter changes allow the device to maintain high polarization extinction ratio across a wide wavelength range by adapting the mode coupling conditions.

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 configuration achieves broadband performance with high polarization extinction ratio across a wide wavelength range, minimizing insertion loss and device footprint, thereby enhancing the efficiency and reliability of polarization handling in optical transmission systems.

Implementation Method 1

a tapered rotator and Y-splitter configuration that rotates TE0 mode to TE1 mode

Methodology Applied

Scientific EffectAdiabatic mode conversion:

Implementation Method 2

Y-splitter configuration that rotates TE0 mode to TE1 mode and splits both TE0 and TE1 modes into distinct portions

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

reducing polarization-dependent loss through a PDL tuning section

Methodology Applied

Scientific EffectPolarization-dependent loss reduction:

Data Source

PatentUS10809459B2Integrated polarization splitter and rotator including a PDL tuning region

Publication Date: 2020.10.20 NOKIA SOLUTIONS & NETWORKS OY

AI summary

An integrated polarization splitter and rotator (PSR) employs the TE0 and TE1 modes of propagating light, rather than the TE0 and TM0 modes used in conventional prior art PSR. The integrated PSR exhibits appreciably flatter wavelength response because it does not require a directional coupler to de-multiplex incoming polarizations. The PSR allows tuning of the TM0 loss to reduce polarization dependent loss (PDL). This integrated polarization splitter and rotator is applicable to all integrated platforms including Silicon-on-Insulator (SOI) and III-V semiconductor compound systems. The PSR may be very compact (12×2 μm2), and provides low loss (<0.3 dB across the C-band) and ultra-broadband operation. The PSR also affords better control of polarization dependent losses.