Joint MAP Transmitter Pre-Distortion for Bandwidth-Limited Optical Systems
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Solution Overview
Problem
Optical communication systems face challenges in minimizing signal interference and improving signal-to-noise ratio due to bandwidth limitations, leading to intersymbol interference and high costs associated with using multiple optical carriers.
Innovation Solution
A joint maximum a posteriori (MAP)-based transmitter pre-distortion and receiver correction method is employed, involving iterations between transmitter-side and receiver-side look-up-tables to compensate for signal distortion and enhance tolerance to bandwidth filtering effects, using weighted summation for stable operation and refinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple optical carriers are used to achieve high-speed transmission rates, then transmission capacity is improved, but system cost increases due to high cost of optical components
Solution Approach 1:
The patent applies preliminary predistortion to the transmit signal before transmission through the optical channel. A look-up table is built during calibration to store predistortion values that pre-compensate for channel effects. This preliminary action at the transmitter side reduces the need for complex post-processing at the receiver and enables the system to achieve high transmission rates with fewer optical carriers, thereby reducing system cost.
2Speed
If high-baudrate electrical signals are used to increase transmission speed, then transmission rate is improved, but intersymbol interference increases due to limited bandwidth of electronic components
Solution Approach 1:
The patent applies predistortion as a preliminary anti-action to counteract the bandwidth filtering effect before it occurs. By pre-compensating the transmit signal using look-up table based predistortion, the system anticipates and counteracts the intersymbol interference that would otherwise be caused by the limited bandwidth of electronic components. This allows high-baudrate signals to be transmitted with minimal ISI.
3Reliability
If traditional receiver sensitivity improvement methods are used to improve signal-to-noise ratio, then signal quality is improved, but system complexity increases
Solution Approach 1:
The patent moves the complexity from the receiver side to the transmitter side by applying predistortion preliminarily. Instead of requiring complex receiver processing to improve signal-to-noise ratio, the system pre-compensates signals at the transmitter using a calibrated look-up table. This preliminary action simplifies the receiver design while maintaining or improving signal quality through the predistorted transmission.
Data Source
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AI summary
A system for optimizing signal quality in an optical communication system is provided including a transmitter (100) for converting digital signals to optical signals, the transmitter (100) including a transmitter digital signal processing chip (103) including a predistortion logic (105) and a transmitter look-up table (LUT) (108). A receiver (200) is operatively coupled to the transmitter (100) for receiving and converting the optical signals from the transmitter (100) to digital signals (117). The receiver (200) includes a receiver digital signal processing chip (213) including a correction logic (211) and a receiver look-up table (LUT) (208). The transmitter LUT (108) is constructed by scaling the receiver LUT (208) by a weight factor and is iteratively updated based on a weighted sum of the receiver LUT (208).