Blind Equalization for Optical Signal Distortion Mitigation
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Solution Overview
Problem
Fiber optic networks face limitations in data throughput and distance due to amplitude degradation and temporal distortions, particularly with increasing frequency transmission, which constrain the performance of Passive Optical Networks (PONs) and other optical communication systems.
Innovation Solution
The method involves using blind equalization techniques to determine and store coefficients for equalizing optical signals in m-ary modulation formats, allowing for demodulation and multiplexing of data streams across multiple optical links, thereby reducing temporal distortions and enhancing data throughput and reach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency transmission is increased to improve data throughput, then data throughput rate is improved, but temporal distortions increase
Solution Approach 1:
The patent applies m-ary modulation formats (such as QAM, QPSK, OFDM, PAM) that change the modulation parameters to encode multiple bits per symbol, thereby increasing data throughput without proportionally increasing the symbol rate and associated temporal distortions. Blind equalization coefficients are adjusted to compensate for the temporal distortions introduced by higher frequency transmissions
Solution Approach 2:
The patent introduces blind equalization as an intermediary processing step that compensates for temporal distortions. The equalization coefficients are determined without requiring a known training sequence, and are used to equalize the received optical signal before demodulation, thereby mitigating the harmful effects of temporal distortions on signal quality
2Length of stationary object
If distance between OLT and ONU/ONT is increased to extend network reach, then network reach is improved, but amplitude degradation increases
Solution Approach 1:
The patent uses m-ary modulation formats that allow for more efficient use of signal amplitude variations. By encoding multiple bits per symbol, the system can maintain reliable communication over longer distances where amplitude degradation occurs, as the higher-order modulation schemes are more resilient to amplitude variations when combined with blind equalization
Solution Approach 2:
The blind equalization process implements a feedback mechanism where the received signal is continuously equalized using previously determined coefficients, and these coefficients are updated based on the statistical properties of the received signal. This adaptive feedback loop compensates for amplitude degradation over distance, maintaining signal quality even as network reach is extended
3Productivity
If blind equalization is used to eliminate training sequences, then protocol efficiency is improved, but equalization complexity increases
Solution Approach 1:
The patent implements blind equalization where the system determines equalization coefficients autonomously without requiring external training sequences. The equalizer uses the statistical properties of the received m-ary modulated signal itself to adaptively determine the coefficients, making the system self-sufficient and eliminating the need for separate training phases, thereby improving protocol efficiency despite the increased computational complexity
Data Source
AI summary
Processing a received optical signal in an optical communication network includes equalizing a received optical signal to provide an equalized signal, demodulating the equalized signal according to an m-ary modulation format to provide a demodulated signal, decoding the demodulated signal according to an inner code to provide an inner-decoded signal, and decoding the inner-decoded signal according to an outer code. Other aspects include other features such as equalizing an optical channel including storing channel characteristics for the optical channel associated with a client, loading the stored channel characteristics during a waiting period between bursts on the channel, and equalizing a received burst from the client using the loaded channel characteristics.