Optical Receiver Filtering With Visible-Light Parallel Channels
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Solution Overview
Problem
Conventional fibre-optic communication systems are costly due to the need for precise alignment of optical fibres and expensive components like single-mode and multi-mode lasers and silicon-germanium receivers, and face issues with chromatic dispersion limiting transmission distance and bandwidth.
Innovation Solution
An optical transmitter unit with an array of micro-LEDs and a controller using OOK coding, coupled with an optical filter to reduce chromatic dispersion, and a photodetector array with CMOS sensors, enables parallel data transmission across multiple channels using commodity components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fibre-optic communication systems use single-mode lasers and silicon-germanium receivers with precise alignment, then transmission bandwidth and reliability are improved, but manufacturing cost and device complexity increase significantly
Solution Approach 1:
The patent replaces expensive single-mode lasers and silicon-germanium receivers with cheaper visible light LEDs and CMOS photodetectors. While individual components are less durable or performance-limited, the system achieves reliability through redundancy and parallel channels rather than through expensive single-point components.
Solution Approach 2:
The patent divides the transmission system into multiple parallel communication channels using multiple LEDs and photodetector pairs. Each channel operates independently at lower speeds (e.g., 2.5 Gbps), and the aggregate bandwidth is achieved through parallel processing. This segmentation allows the use of simpler, less expensive components while maintaining overall system reliability through redundancy.
2Productivity
If conventional systems use complex coding schemes like PAM4 or OFDM to maximise bandwidth per lane, then data transmission speed is improved, but device complexity and cost of digital circuitry increase
Solution Approach 1:
Instead of using complex modulation schemes on a single channel, the patent segments the data stream across multiple simpler parallel channels. Each channel uses basic on-off keying (OOK) modulation, which requires minimal digital circuitry. The aggregate throughput is achieved through parallel processing rather than through complex single-channel modulation.
Solution Approach 2:
The patent changes the fundamental parameters of the optical transmission by using visible light instead of infrared, and by using LED modulation rather than laser modulation. This allows the use of simpler digital circuitry for encoding and decoding, as the modulation depths can be kept relatively low while still achieving adequate signal-to-noise ratios through the parallel channel architecture.
3Productivity
If visible light signals are transmitted at higher speeds, then data bandwidth is improved, but chromatic dispersion increases and limits transmission distance
Solution Approach 1:
The patent segments the optical transmission across multiple parallel channels, each operating at lower speeds (e.g., 2.5 Gbps per channel). This segmentation allows each individual channel to maintain lower chromatic dispersion while the aggregate bandwidth is achieved through parallel processing. The lower speeds per channel reduce the differential group delay and minimize pulse broadening.
Solution Approach 2:
The patent changes the optical parameters by using visible light LEDs with relatively narrow spectral widths compared to laser sources. This parameter change reduces the inherent chromatic dispersion of the light source itself. Additionally, the use of optical filters to narrow the spectral bandwidth of each channel further reduces chromatic dispersion, enabling longer transmission distances at the reduced per-channel speeds.
4Reliability
If precise alignment of optical fibres is implemented, then signal transmission quality is improved, but manufacturing precision requirements and production complexity increase
Solution Approach 1:
The patent uses inexpensive LED light sources and CMOS photodetectors that are more tolerant of misalignment compared to laser sources and specialized detectors. The lower coherence and narrower spectral width of LEDs reduce the sensitivity to alignment errors, allowing for relaxed manufacturing precision requirements while maintaining acceptable signal transmission quality.
Solution Approach 2:
The patent employs multiple parallel channels with redundant transmitter-receiver pairs. This segmentation provides tolerance to alignment errors through redundancy; if one channel experiences misalignment or signal degradation, other channels can compensate. The system can dynamically switch between channels or use error correction codes to maintain overall transmission reliability despite varying alignment conditions.
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 reduces manufacturing costs and mitigates chromatic dispersion, allowing high-bandwidth communication over longer distances with cost-effective components and simplified digital signal processing.
Implementation Method 1
a dispersive optical element, configured to separate the received modulated visible light into a plurality of optical signals based on wavelength
Implementation Method 2
an optical filter configured to reduce chromatic dispersion. The optical filter may comprise an optical band-pass filter configured to narrow pulses of modulated light emitted by the light sources
Implementation Method 3
a photodetector array, each photodetector in the photodetector array configured to receive modulated visible light from an array of light sources
Data Source
AI summary
A filtering unit includes a dispersive optical element that receives modulated visible light from an optical transmitter unit, separates the received modulated visible light into a plurality of optical signals based on wavelength; and direct the plurality of optical signals to a photodetector array of an optical receiver unit, each photodetector in the photodetector array comprising a plurality of filters and a plurality of corresponding photodiodes each arranged to receive light from a respective one of the plurality of filters. The filtering unit can be included in the optical receiver unit including the photodetector array to receive the modulated visible light from the multicore fibre optic cable; and a controller to receive the output of the photodetectors; decode data from the received output, and provide the decoded data to a receiving computer system.