Pulsed Optical Beam Detection via Photodetector Array
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Solution Overview
Problem
Existing non-line-of-sight (NLOS) free-space optical communication (FSOC) systems have limited range and are challenged by background radiation, especially during daylight, which affects the signal-to-noise ratio (SNR) and communication distance.
Innovation Solution
A method using a photodetector array to detect light scattered progressively from a pulsed optical beam as it propagates through a scattering medium, improving the signal-to-noise ratio (SNR) and enabling NLOS FSOC over longer distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If UV-C light is used for NLOS FSOC to reduce background radiation, then signal detection is improved during daytime, but communication range is limited
Solution Approach 1:
The patent employs pulsed optical beams instead of continuous wave transmission. By transmitting optical pulses with specific timing and duration, the system achieves better signal-to-noise ratio through temporal gating, allowing detection of scattered photons from each pulse while rejecting background radiation. This periodic transmission mode enables extended communication range while maintaining daytime operability.
2Measurement precision
If a single photodetector is used to detect scattered light, then device complexity is low, but signal-to-noise ratio is insufficient
Solution Approach 1:
The patent divides the detection function across multiple photodetectors arranged in an array, where each photodetector monitors a specific spatial region or time window. By segmenting the detection process both spatially and temporally, the system can integrate signals from multiple detectors while rejecting background noise, achieving superior signal-to-noise ratio without requiring a single complex detector.
Solution Approach 2:
The patent combines signals from multiple photodetectors through coherent integration, where the individual detector outputs are summed or processed together to enhance the detected signal. This merging of multiple detection channels allows the system to accumulate photons from the scattered optical beam while averaging out random background fluctuations, improving measurement precision.
3Measurement precision
If light is scattered progressively through multiple regions of the scattering medium, then detection contrast is improved, but signal attenuation increases
Solution Approach 1:
The patent uses time-gated detection where the photodetectors are activated only during the expected arrival time window of scattered photons from each optical pulse. This preliminary timing synchronization allows the system to capture scattered light from multiple regions of the scattering medium while rejecting later-arriving background photons, improving detection contrast without requiring increased transmission power.
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 method enhances the contrast and SNR of detected pulsed optical beams, facilitating NLOS FSOC over greater ranges than prior art methods, even in daylight conditions.
Implementation Method 1
detect light which is scattered progressively from the same optical pulse as the optical pulse propagates through a plurality of regions of the scattering medium
Implementation Method 2
using a plurality of photodetectors of a photodetector array to detect light
Data Source
AI summary
A method is disclosed for use in detecting a pulsed optical beam when the pulsed optical beam is transmitted through a scattering medium, wherein the pulsed optical beam comprises a plurality of optical pulses and the method comprises using a plurality of photodetectors of a photodetector array to detect light which is scattered progressively from the same optical pulse as the optical pulse propagates through a plurality of regions of the scattering medium and which is then received progressively on different photodetectors of the photodetector array. The method may be used in particular, though not exclusively, for non-line-of-sight free-space optical communications. An optical receiver for use in detecting the pulsed optical beam and an associated optical system are also disclosed.