Optical Resonator Alignment for Free-Space Optical Communications

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Solution Overview

Problem

Existing free-space optical communication systems face challenges in maintaining transmitter-receiver alignment without mechanical rotation, which increases system size, weight, and complexity, and imparts momentum, especially when dealing with varying angles of incidence.

Innovation Solution

An optical receiver system utilizing an optical resonator assembly, such as a Fabry-Perot etalon or micro-ring resonator, with a controller to tune the resonator's optical thickness or path length to maintain alignment over a range of angles without mechanical movement, using piezoelectric materials and electro-optical components to adjust the resonator's parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mechanical gimbal solutions or beam-steering solutions with movable mirrors are used to maintain transmitter-receiver alignment, then alignment is maintained, but system size, weight, cost and complexity increase

Engineering Contradiction:

Improvetransmitter-receiver alignmentVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical gimbal systems and movable mirror beam-steering systems with a fixed optical resonator assembly. The resonator maintains alignment through its fixed structural design rather than mechanical movement, eliminating complex mechanical components while preserving alignment functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention extracts and eliminates the mechanical movement components (gimbals, movable mirrors) from the alignment system. By using a fixed resonator assembly with a specific geometric configuration, the patent removes the need for these complex mechanical subsystems while maintaining the ability to track angle-of-arrival variations.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If mechanical gimbal solutions or beam-steering solutions with movable mirrors are used to maintain transmitter-receiver alignment, then alignment is maintained, but size and weight increase

Engineering Contradiction:

Improvetransmitter-receiver alignmentVSAvoidsystem weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent substitutes heavy mechanical gimbal systems and movable mirror assemblies with a lightweight fixed optical resonator assembly. The fixed structure eliminates the need for motors, bearings, and other heavy mechanical components, significantly reducing system weight while maintaining alignment capability through optical resonance principles.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If mechanical gimbal solutions or beam-steering solutions with movable mirrors are used to maintain transmitter-receiver alignment, then alignment is maintained, but momentum is imparted to the platform

Engineering Contradiction:

Improvetransmitter-receiver alignmentVSAvoidimparted momentum

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces mechanical systems that impart momentum during movement with a fixed optical resonator assembly. Since the resonator is stationary and maintains alignment through its fixed geometric configuration and optical resonance properties, no momentum is imparted to the platform, eliminating this harmful effect.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If conventional solutions with movable components are used, then alignment is maintained, but tuning speed is limited

Engineering Contradiction:

Improvealignment maintenanceVSAvoidtuning speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent replaces mechanical tuning systems with an electrically controllable optical resonator assembly. The resonator can be rapidly tuned by adjusting electrical parameters (such as voltage applied to piezoelectric actuators or electro-optic materials) rather than mechanically moving components, achieving much higher tuning speeds while maintaining alignment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 high-speed tuning and reduced system complexity while maintaining alignment without imparting momentum, enabling a large field of regard without the need for gimbal systems or steering mirrors.

Implementation Method 1

accumulate resonant optical signal energy inside the at least one optical resonator

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

the material is a piezoelectric material the controller is configured to apply the control signal to the piezoelectric material to tune an optical thickness of the at least one optical resonator

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 3

a first semi-reflective surface positioned to receive the input optical signal, a second semi-reflective surface positioned facing the first semi-reflective surface and arranged to emit the output optical signal

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS11303356B1Methods and apparatus for maintaining receiver operating point with changing angle-of-arrival of a received signal

Publication Date: 2022.04.12 RAYTHEON CO

AI summary

Methods and apparatus for maintaining transmitter-receiver alignment in a free space optical communications system without substantially moving the receiver element and with very little to no imparted momentum, while also allowing for higher tuning speeds and less system complexity than conventional solutions. The methods and apparatus allow for a large field of regard at the optical receiver, without the need for electromechanical gimbals to move the entire receiver unit and without the need for steering mirrors to move and align the incoming optical beam.