Integrated Polarization Controller With Attenuator for PDL Compensation

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Solution Overview

Problem

Polarization dependent loss (PDL) in polarization controllers leads to power fluctuations and crosstalk in optical systems, particularly in dual polarization systems, due to varying polarization states during transmission.

Innovation Solution

An integrated polarization controller with a polarization splitter rotator and optical attenuators, such as variable optical attenuators (VOAs), is used to balance the loss between orthogonal polarizations, compensating for PDL and reducing crosstalk by adjusting phase shifts and attenuating light signals to maintain orthogonal states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a polarization splitter rotator is used to separate orthogonal polarizations, then polarization multiplexing capability is improved, but polarization dependent loss causes power fluctuations and crosstalk

Engineering Contradiction:

Improvepolarization multiplexing capabilityVSAvoidpower fluctuation stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces variable optical attenuators that can dynamically adjust their attenuation levels to compensate for polarization dependent loss. By changing the attenuation parameter in response to polarization state variations, the system maintains stable power levels across both polarization channels, resolving the contradiction between polarization multiplexing capability and power fluctuation stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements a feedback mechanism where polarization state information is monitored and used to control the variable optical attenuators. This closed-loop control allows the system to automatically adjust attenuation levels to compensate for PDL variations, thereby reducing power fluctuations while maintaining the polarization multiplexing function.

Inventive Principle:

Principle #23Feedback

2Reliability

If variable optical attenuators are added to compensate for polarization dependent loss, then power fluctuation is reduced, but device complexity increases

Engineering Contradiction:

Improvepower fluctuation stabilityVSAvoidnumber of optical components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent integrates the variable optical attenuators directly into the polarization controller architecture, merging the attenuation function with the polarization control function. This integration reduces the need for separate, standalone attenuation devices and simplifies the overall system architecture while still providing effective PDL compensation and power fluctuation reduction.

Inventive Principle:

Principle #5Merging (Combining)

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

The solution effectively reduces power fluctuations and crosstalk by ensuring balanced optical power and orthogonal polarization states, enhancing system performance and efficiency.

Implementation Method 1

a polarization splitter rotator configured to receive an input light signal and separate the input light signal into a first light signal having a first insertion loss and a second light signal having a second insertion loss

Methodology Applied

Scientific EffectPolarization splitting: Polarisation

Implementation Method 2

a first optical attenuator arranged in a first one of the first optical path to attenuate the first light signal or in the second optical path to attenuate the second light signal in order to compensate for at least a first portion of a polarization dependent loss between the first light signal and the second light signal

Methodology Applied

Scientific EffectOptical attenuation: Absorption (EM radiation)

Implementation Method 3

a first phase shifter arranged in the first optical path and configured to apply a first phase shift to the first light signal to tune at least a first portion of a relative phase difference between the first light signal and the second light signal

Methodology Applied

Scientific EffectPhase shifting:

Data Source

PatentUS20250300732A1Integrated polarization controller with optical attenuator for crosstalk and power fluctuation reduction

Publication Date: 2025.09.25 WELLS FARGO BANK NA

AI summary

A method includes separating, by a polarization splitter rotator, an input light signal into a first light signal having a first insertion loss and a second light signal having a second insertion loss that is different than the first insertion loss; and attenuating, by an optical attenuator, the first light signal or the second light signal in order to compensate for a polarization dependent loss between the first light signal and the second light signal such that a total optical power of the first light signal and the second light signal is independent of a polarization state of the input light signal.