Optical Link Architecture Using Wireline Equalization
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Solution Overview
Problem
High-speed optical communication systems face challenges in maintaining bandwidth requirements, leading to increased power dissipation and design complexities due to the need for high bandwidth components, particularly in the transmitter and receiver units, which also limits the effectiveness of equalization techniques.
Innovation Solution
The implementation of a SerializerDeserializer (SerDes) apparatus with feed-forward equalization and other equalization techniques, such as decision-feedback and continuous time linear equalizers, operating at lower bandwidths than required for the target data rate, using low bandwidth optical components like Mach-Zehnder interferometers and silicon photonic chips, to reduce power dissipation and simplify design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high bandwidth components are used in the transmitter and receiver units, then the target data rate can be maintained, but power dissipation increases and design complexity increases
Solution Approach 1:
The patent applies feed-forward equalization (FFE) at the transmitter side before the optical signal is sent through the fiber. This preliminary equalization action pre-compensates for the bandwidth limitations and signal distortions that will occur in the optical link, allowing the receiver to operate at lower bandwidth while still achieving the target data rate. The FFE filter adjusts the transmitted signal characteristics in advance to counteract expected channel impairments.
Solution Approach 2:
The patent implements decision-feedback equalization (DFE) at the receiver side, which uses feedback from previously detected symbols to compensate for inter-symbol interference. The DFE continuously adjusts its equalization parameters based on the detected signal quality, enabling the receiver to maintain accurate data recovery at lower bandwidth operations. This feedback mechanism allows the system to adapt to channel variations without requiring high bandwidth components.
2Speed
If high bandwidth components are used in the transmitter and receiver units, then the target data rate can be maintained, but device complexity increases
Solution Approach 1:
By implementing feed-forward equalization at the transmitter, the patent performs signal conditioning in advance, which simplifies the receiver design. The FFE pre-compensates for channel effects, reducing the equalization burden on the receiver and allowing the use of simpler, lower-bandwidth receiver components. This preliminary action shifts complexity from the receiver to the transmitter, where it can be more efficiently managed.
Solution Approach 2:
The patent divides the equalization function into two separate segments: feed-forward equalization at the transmitter and decision-feedback equalization at the receiver. This segmentation allows each side to use optimized, lower-complexity equalization techniques rather than requiring a single high-bandwidth component to handle all equalization requirements. The segmented approach distributes the complexity across both ends of the link.
3Reliability
If equalization techniques are applied to correct for fiber imperfections, then signal quality improves, but the bandwidth requirements for E/O TX and E/O RX components increase
Solution Approach 1:
The feed-forward equalization applied at the transmitter pre-compensates for fiber imperfections and bandwidth limitations before the signal enters the optical channel. This preliminary correction maintains signal quality throughout transmission, allowing the use of lower-bandwidth E/O TX and E/O RX components while still achieving reliable signal recovery. The FFE adjusts the transmitted signal to counteract expected fiber-induced distortions.
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 enables high data rate, low power optical communication with improved sensitivity and reduced component costs, allowing for effective equalization across the entire optical link, including modulators and transimpedance amplifiers, while maintaining the desired data rate.
Implementation Method 1
an optical modulator having an optical modulator electrical input port in communication with the SerDes TX electrical output port and having an optical modulator optical output port
Implementation Method 2
the optical signal is converted back into the electrical domain by the optical receiver (Optical RX)
Data Source
AI summary
A high data rate, high sensitivity, low power optical link using low-bandwidth components and low-bandwidth E/O drivers and receivers and method of building same. The method is based on the idea of making the optical part of the link look like a bandwidth limited lossy electrical channel, so that the powerful equalization methods used in the wireline electrical links can be applied to recover the transmitted data in a situation with low bandwidth and/or high loss and strong inter-symbol interference. Linear and non-linear optical channel components, E/O drivers and receivers can benefit from the apparatus and the methods of the invention.