Carrier Suppression in Frequency Referenced PON
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Solution Overview
Problem
Conventional passive optical networks with time-division multiplexing face challenges in scaling to support high data rates due to latency, jitter, and the high cost and complexity of carrier suppression in frequency division multiplexing-based systems.
Innovation Solution
The proposed solution involves an apparatus and method for carrier suppression in frequency referenced passive optical networks, using a periodic optical filter unit and a control unit to suppress residual optical carriers in the combined uplink signal by filtering a portion of the downlink frequency comb signal and the combined uplink signal, and spectrally aligning the periodic optical filter unit with the frequency comb signal based on the power of the filtered portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency division multiplexing is used to enable simultaneous transmission from multiple users, then the system capacity and data rate are improved, but residual optical carrier frequencies aggregate and overload the receiver components
Solution Approach 1:
The patent extracts and removes the harmful residual optical carrier frequencies from the frequency division multiplexed signal using optical filtering techniques. The comb filter structure selectively attenuates carrier frequencies at specific wavelengths while allowing the modulated signal components to pass through, thereby separating the harmful carrier component from the useful signal.
Solution Approach 2:
The patent introduces an optical filter as an intermediary component between the frequency division multiplexing stage and the receiver. This filter acts as a mediator that processes the signal by removing carrier frequencies before they reach the receiver, preventing overload while maintaining the multiplexed data signals.
2Object-affected harmful factors
If conventional optical filters are used for carrier suppression, then residual carriers are removed, but the device complexity and cost increase significantly
Solution Approach 1:
The patent merges multiple filtering functions into a single integrated comb filter structure. Instead of using multiple separate filters tuned to different carrier frequencies, the comb filter uses a periodic structure that simultaneously addresses multiple carrier frequencies through its frequency-selective properties, reducing the number of discrete components required.
Solution Approach 2:
The comb filter structure provides universal carrier suppression capability across multiple wavelength channels through its periodic transfer function. A single filter design can suppress carriers at different frequencies by adjusting the periodicity parameter, making the filter multi-functional for various carrier frequencies without requiring separate specialized filters for each.
3Reliability
If time-division multiplexing is used in passive optical networks, then data collision is avoided, but latency and jitter increase limiting scalability
Solution Approach 1:
The patent transitions from static time-division multiplexing to dynamic frequency-division multiplexing with carrier suppression. This allows multiple users to transmit simultaneously at different frequencies rather than taking turns in time slots, eliminating the inherent latency and jitter of TDM while maintaining collision avoidance through frequency separation.
Solution Approach 2:
The patent employs periodic optical filtering with a comb filter structure that creates periodic notches in the frequency response. This periodic action selectively removes carrier frequencies at regular intervals across the spectrum, enabling structured frequency allocation for multiple users without the time-based constraints of traditional multiplexing.
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 improves the suppression of residual optical carriers, reduces complexity and cost, and enables efficient carrier suppression in frequency division multiplexing passive optical network systems, supporting higher data rates and emerging applications.
Implementation Method 1
a periodic optical filter unit configured for suppressing residual optical carriers in the combined uplink signal by filtering a portion of the downlink frequency comb signal and the combined uplink signal
Implementation Method 2
a control unit configured for monitoring a power of the filtered portion of the downlink frequency comb signal and spectrally aligning the periodic optical filter unit with the frequency comb signal based on the power of the filtered portion
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
An apparatus for carrier suppression in a frequency referenced passive optical network (PON) with point to multi-point (P2MP) topology includes central node and end nodes. The central node includes central node transmitter and single coherent receiver. The apparatus is arranged in central node and includes periodic optical filter unit and control unit. The periodic optical filter unit suppresses residual optical carriers in combined uplink signal by filtering portion of downlink frequency comb signal and combined uplink signal, which includes intensity-modulated optical uplink signals from end nodes. The control unit monitors power of filtered portion of downlink frequency comb signal and spectrally aligns periodic optical filter unit with frequency comb signal based on power of filtered portion of downlink frequency comb signal. The apparatus provides improved suppression which is cost efficient and has reduced complexity to suppress residual optical carriers.