Rotatable Optical Resonator for Flexible Signal Demodulation

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Solution Overview

Problem

Conventional optical demodulation methods are either complex and expensive or limited in flexibility, particularly in fiber-based and short-range free-space optical communications, due to fixed data rates and modulation formats.

Innovation Solution

A passive modulation approach using a rotatable optical cavity resonator, such as an etalon, to dynamically adjust its operating condition based on the angle of arrival of optical signals, allowing for variable data rates and different modulation formats.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional demodulation methods using local oscillators are used, then demodulation capability is achieved, but device complexity and cost increase

Engineering Contradiction:
Improvedemodulation capabilityVSAvoidcomplexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the local oscillator component from the demodulation system. By using a passive optical resonator that naturally provides the reference signal through its resonance characteristics, the complex active local oscillator is removed, simplifying the device while maintaining demodulation capability

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The optical resonator serves itself by generating the reference signal through its own resonance properties. The resonator's natural oscillation at specific frequencies provides the reference needed for demodulation without requiring an external active oscillator, reducing system complexity

Inventive Principle:
Principle #25Self-service

2Ease of manufacture

If fixed demodulation systems are used, then manufacturing simplicity is maintained, but adaptability to different data rates and modulation formats deteriorates

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidadaptability
Core Design Contradiction:
Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent introduces dynamic tuning capability to the optical resonator through mechanical adjustment mechanisms. This allows the resonator's resonance frequency to be dynamically adjusted to match different incoming signal frequencies, enabling adaptation to various data rates and modulation formats while maintaining a relatively simple manufacturing base

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system changes the physical parameters of the optical resonator (such as cavity length or refractive index) to adjust its resonance characteristics. By modifying these parameters, the demodulator can adapt to different operating conditions and signal types without requiring complete system redesign

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

Provides a flexible and low-cost solution capable of demodulating optical signals with variable data rates and modulation formats, suitable for fiber-based and short-range free-space optical communications.

Implementation Method 1

an optical resonator, such as a Fabry-Perot etalon, an optical delay line, or other bulk optical cavity that accumulates energy, as a modulation converter

Methodology Applied
Scientific EffectOptical resonance: Resonance

Implementation Method 2

The arriving optical signals may be phase modulated, amplitude modulated, or frequency modulated, and the optical resonator assembly converts the received phase, amplitude, and/or frequency modulated optical signal into a directly detectable intensity modulated output signal

Methodology Applied
Scientific EffectPhase change detection: Interference

Data Source

PatentEP3994808B1Optical receiver comprising a rotatable optical resonator, and method for demodulating an optical signal using said receiver
Publication Date: 2026.04.15 RAYTHEON CO
  • EP3994808B1 patent drawingFigure 1
  • EP3994808B1 patent drawingFigure 2
  • EP3994808B1 patent drawingFigure 3

AI summary

Apparatus, systems, and methods include leveraging the angular dependence of the angle of arrival of the incoming optical signal at an optical resonator of an optical receiver and the output response signal to adjust the operating condition of the optical resonator. The optical resonator is dynamically tuned by rotating the optical resonator to optimize signal-to-noise ratio or other parameters for different modulation formats of the incoming optical signal or other different operating conditions.