Direct-Detection Optical Receiver In-Band Interference Mitigation
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Solution Overview
Problem
Optical communication systems face interference issues due to reflections from connectors, leading to multi-path interference (MPI) and in-band noise, which conventional methods like higher order modulation and error correction techniques are ineffective in mitigating.
Innovation Solution
An optical receiver system comprising a photodetector, analog-to-digital converter, and digital signal processor that detects frequency and bandwidth of interference signals, using notch or band-pass filters to suppress interference, and in transmitters, dynamically tuning the carrier frequency to move interference out of the signal bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods like higher order modulation and error correction techniques are used, then data transmission capacity is improved, but they are ineffective in mitigating in-band optical interference
Solution Approach 1:
The patent extracts and removes the interference signal from the received optical signal by detecting its frequency and bandwidth characteristics, then applying notch or band-pass filters to eliminate the harmful in-band interference while preserving the data signal
Solution Approach 2:
The patent changes the carrier frequency parameter dynamically to move the data signal away from the interference frequency band, transforming the frequency domain parameters to achieve separation between signal and interference
2Object-affected harmful factors
If notch or band-pass filters are applied to remove interference signals, then interference suppression is improved, but there is a risk of affecting the original data signal
Solution Approach 1:
The patent replaces traditional mechanical or fixed filtering approaches with adaptive digital signal processing that dynamically detects interference characteristics and adjusts filter parameters accordingly, allowing precise removal of interference without affecting the data signal
Solution Approach 2:
The patent employs feedback mechanisms where the received signal is continuously monitored, interference parameters are detected and fed back to adjust the filtering operation, ensuring that the filter adapts to changing interference conditions while protecting the data signal
3Object-affected harmful factors
If carrier frequency is dynamically tuned to move interference out of signal bandwidth, then interference mitigation is improved, but device complexity increases
Solution Approach 1:
The patent makes the carrier frequency dynamic rather than fixed, allowing it to be tuned automatically in response to detected interference conditions, enabling the system to adapt to changing environments while managing complexity through integrated control
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
Effectively mitigates in-band interference by accurately identifying and filtering out interference signals without significantly affecting the original data signal, improving data transmission reliability and reducing error rates.
Implementation Method 1
The at least one photo detector is configured to generate a first electrical analog receiver signal in response to receiving an optical signal
Implementation Method 2
The digital signal processor is also configured to filter the first digital receiver signal using a notch filter having a center frequency and bandwidth substantially equal to the frequency and bandwidth, respectively, of the interference signal
Data Source
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AI summary
This disclosure provides systems, methods, and apparatus for mitigating the effects of interference signals on optical signals received at a direct-detection optical receivers. The optical receivers are capable of attenuating interference noise signals resulting from the interference between a transmitted optical signal transmitted from a transmitter to the optical receiver and one or more additional signals received at the optical receiver. The interference can be due to multi-path interference or due to in-band interference. The receivers include a tunable filter for filtering the received optical signal to remove the interference. A frequency offset module processes the received optical signal to determine a frequency offset indicative of the difference between the carrier frequencies of a modulated optical signal and an interference optical signal. The offset frequency and a bandwidth determined by the frequency offset module can be used to adjust the tunable filter to remove the interference signal from the received signal.