Full-Duplex Laser Communication via Modulating Retro-Reflector
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current free-space optical communication systems using modulating retro-reflectors are either half-duplex or require additional optical transmitters and filtering, increasing size, weight, power, and cost, especially when bidirectional data transmission is needed.
Innovation Solution
A system utilizing a modulating retro-reflector terminal with an interrogator that intensity modulates a laser signal with a digitally modulated RF signal using QPSK, allowing for full-duplex communication over a single wavelength, where the interrogator and MRR terminal exchange data using intensity and re-modulation techniques without the need for additional optical transmitters or filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bidirectional data transmission is implemented using different optical wavelengths, then full-duplex communication is achieved, but optical filtering and additional optical transmitters are required, increasing size, weight, power, and cost
Solution Approach 1:
The patent changes the modulation parameter from wavelength differentiation to temporal differentiation. By using intensity modulation at different time slots on the same wavelength, the system achieves bidirectional communication without requiring optical filters or additional transmitters, thus reducing device complexity while maintaining full-duplex capability
Solution Approach 2:
The single optical transmitter is made multi-functional by enabling it to handle both uplink and downlink transmissions on the same wavelength through intelligent temporal multiplexing. This universal approach eliminates the need for separate transmitters and filters for different directions, reducing overall system complexity
2Device complexity
If a modulating retro-reflector link is used for low data rate requirements, then size, weight, and power are reduced, but the link becomes half-duplex or requires additional equipment for full-duplex operation
Solution Approach 1:
The patent implements periodic time-division multiplexing where the optical transmitter alternates between uplink and downlink transmission slots. This periodic action enables full-duplex communication capability in the lightweight MRR system without requiring additional hardware, thus maintaining low SWAP while achieving bidirectional data transmission
Solution Approach 2:
The system dynamically switches transmission directions in time slots, making the communication mode flexible and adaptable. This dynamic time-division approach allows the same physical infrastructure to support full-duplex operation, transforming a inherently half-duplex MRR link into a full-duplex system without additional equipment
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
Enables efficient, full-duplex data transmission with high data rates and reduced complexity and cost, maintaining low power consumption and size, while maintaining low probability of intercept and detection, as demonstrated by laboratory experiments achieving error-free transmission with minimal power penalty.
Implementation Method 1
The interrogator intensity modulates a laser using the modulated RF signal to produce an intensity modulated laser beam
Implementation Method 2
This beam is passively retroreflected back to the interrogator as a retroreflected beam with a data signal imposed on it by the modulator
Data Source
AI summary
Methods, systems and other embodiments associated with a laser communication system using a single wavelength are presented. A first data is modulated onto an RF carrier to produce a modulated RF carrier. A laser is intensity modulated using with the modulated RF carrier. The intensity modulated laser beam is transmitted from an interrogator to a modulating retro-reflector (MRR) terminal. A portion of the laser beam is received at a receiver at the MRR terminal. Another portion of the laser is modulated at the MRR terminal with a second data to produce a re-modulated laser beam. The re-modulated laser beam is reflected back to the interrogator.