Fiber-Coupled Balanced Receiver With Single-Detector Signal Isolation
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Solution Overview
Problem
Current balanced receivers face limitations due to imperfectly matched detectors and amplification electronics, high costs, and sensitivity to temperature drift and air currents, particularly in free-space implementations with large path-length differences.
Innovation Solution
A single-element balanced receiver design using optical fiber paths with a beam splitter to split light into target and reference paths, where the difference in optical path lengths and refractive indices are used to isolate the signal of interest, achieving common mode rejection ratios of at least 50 dB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two carefully matched photodiodes are used to measure slightly different signals simultaneously, then the differential signal can be isolated by electronically canceling the common signal, but the performance is limited by imperfectly matched detectors and amplification electronics
Solution Approach 1:
The invention segments the optical path into two separate fiber optic paths (reference path and measurement path) that converge at a single photodiode. This segmentation allows each path to be independently controlled and matched in length, while using a single detector eliminates detector matching issues entirely.
Solution Approach 2:
The invention merges the reference signal and measurement signal paths at a single photodiode detector. By combining the optical paths before detection and using electronic signal processing to subtract the reference signal, the system achieves differential measurement without requiring multiple matched detectors.
2Measurement precision
If closely matched detector pairs are used, then measurement precision can be maintained, but the cost of matching detectors and electronics increases
Solution Approach 1:
The invention extracts the matching requirement from the detector pair and applies it only to the fiber optic path lengths. By using a single photodiode, the system eliminates the need for expensive matched detector pairs while maintaining measurement precision through path length matching and electronic reference subtraction.
3Ease of manufacture
If free-space single-element receiver designs are used, then difficulties with matching detector and electronic pairs are ameliorated, but the designs require path-length differences of more than a few cm which come with a large footprint requirement
Solution Approach 1:
The invention replaces the free-space optical path with fiber optic cables. This substitution allows precise control of path lengths within compact spaces, eliminating the need for large physical separations between reference and measurement paths while maintaining the single-element receiver advantage of using one detector.
4Ease of manufacture
If free-space single-element receiver designs are used, then detector matching is simplified, but the designs become sensitive to temperature drift and small air currents
Solution Approach 1:
The invention introduces fiber optic cables as intermediaries between the optical sources and the photodiode detector. These fibers are insensitive to temperature drift and air currents, providing stable light transmission paths that eliminate the environmental sensitivities inherent in free-space optical designs.
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 design achieves improved sensitivity and reduced noise interference by isolating the differential signal effectively, overcoming the limitations of previous technologies.
Implementation Method 1
a beam splitter configured to receive a sample light and split the sample light into a target light comprising a signal of interest and a reference light
Implementation Method 2
a first optical fiber path configured to receive the target light, a second optical fiber path having a different length than the first optical fiber path and configured to receive the reference light
Implementation Method 3
a light detector configured to receive the light from the first optical fiber path and the second optical fiber paths at effectively the same point on a surface of the light detector
Data Source
AI summary
A single-element balanced receiver system that includes a beam splitter configured to receive a simple light and split the sample light into a target light and a reference light, a first optical fiber path configured to receive the target light, and a second optical fiber path having a different length than the first optical fiber path and configured to receive the reference light, and a light detector configured to receive the light from the first optical path and the second optical path at effectively same point on a surface of the light detector.