Optical Signal Interference Cancellation for IMDD Bandwidth
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Solution Overview
Problem
Conventional optical communication systems, particularly those using Intensity-Modulation Direct Detection (IMDD), face limitations in bandwidth efficiency due to RF power fading and signal interference, which restricts high-speed transmission in next-generation passive optical networks (NGPON).
Innovation Solution
The method involves receiving optical signals with subcarrier to subcarrier intermixing interference (SSII) components, converting them into a frequency domain, estimating and cancelling the interference using dynamic and static chirp components, thereby enhancing the useful bandwidth of IMDD systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional IMDD technique is used, then device cost is low and design is simple, but transmission rate and bandwidth efficiency fall short of next-generation standards
Solution Approach 1:
The patent extracts and removes the harmful SSII interference component from the received optical signal through digital signal processing. By identifying and eliminating this specific interference source in the frequency domain, the system achieves higher transmission rates without requiring complex hardware modifications, thus resolving the contradiction between productivity improvement and device complexity.
Solution Approach 2:
The patent changes the processing domain from time domain to frequency domain analysis, and adjusts signal parameters through digital filtering and interference cancellation algorithms. This parameter transformation allows conventional IMDD devices to achieve next-generation transmission rates by modifying signal processing parameters rather than hardware architecture.
2Productivity
If OFDM modulation technique is used instead of OOK, then bandwidth efficiency is improved, but RF power fading and SSII interference worsen
Solution Approach 1:
The patent converts the harmful SSII interference into a detectable and removable component by transforming the signal to the frequency domain. The interference, which initially degrades OFDM performance, becomes identifiable through its characteristic spectral signature, allowing the system to extract and eliminate it, thereby converting a harmful factor into a manageable parameter.
Solution Approach 2:
The patent introduces digital signal processing algorithms as an intermediary between the OFDM modulation and the optical detection. This intermediary layer performs frequency domain analysis and interference cancellation, mediating the harmful effects of RF power fading and SSII interference while preserving the bandwidth efficiency benefits of OFDM.
3Object-affected harmful factors
If single sideband modulation is used to eliminate RF fading, then RF power fading is reduced, but device cost increases twenty times due to MZM modulator requirement
Solution Approach 1:
The patent creates a digital copy of the SSII interference component in the frequency domain and uses this copy to cancel the actual interference from the signal. This copying approach in the digital domain achieves interference mitigation without requiring expensive hardware modifications like MZM modulators, thus resolving the cost contradiction.
Solution Approach 2:
The patent replaces the mechanical/optical single sideband modulation approach (requiring expensive MZM modulators) with a digital signal processing approach. By substituting hardware-based interference mitigation with software-based algorithms in the frequency domain, the system eliminates RF power fading effects without the prohibitive cost increase.
4Object-affected harmful factors
If guard band is added to accommodate SSBI in single sideband system, then SSBI is managed, but transmission bandwidth doubles
Solution Approach 1:
Instead of preventing SSII interference through conventional guard bands, the patent inverts the approach by allowing the interference to exist and then actively cancelling it through frequency domain processing. This inversion strategy eliminates the need for bandwidth-wasting guard bands while effectively managing SSII interference.
Data Source
AI summary
A method for receiving optical signals and a device using the same method are provided herein. The method includes the elements of receiving an input signal which includes a signal component and an interference component, wherein the interference component is subcarrier to subcarrier intermixing interference (SSII). The input signal is first converted into a frequency domain signal. The interference component of the input signal is estimated based on a mathematical model according to at least a dynamic chirp component and a static chirp component. The interference component is then cancelled from the input signal to obtain an output signal.