PCIe Retimer Optical Cable Protocol Stability
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Solution Overview
Problem
PCIe protocols are disrupted by the transition from electrical to optical interfaces due to issues with signal termination, noise interference, and lack of support for side band signals, which affects data rate changes and link equalization.
Innovation Solution
Introduction of new ordered sets such as Optical Idle Ordered Set (OIOS) and High Z Ordered Set (HZOS) across the optical interface, along with modified SKPOS for side band data, to manage electrical idle states and impedance propagation, ensuring proper data rate changes and link stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If O/E (Optical/Electrical) interfaces are used to transmit PCIe signals over optical cable, then transmission distance is extended, but the interface does not provide correct termination on the electrical side and does not provide a mechanism over the optical side, which interferes with the PCIe protocol
Solution Approach 1:
The patent introduces a retimer device as an intermediary component between the electrical PCIe interface and the optical cable. The retimer provides proper electrical termination for differential signals and converts them to optical signals, while also generating artificial idle signals to maintain protocol compatibility. This mediator resolves the contradiction by enabling long-distance transmission while preserving PCIe protocol integrity.
Solution Approach 2:
The patent modifies the signal parameters by introducing new ordered sets (OIOS, HZOS) that are specifically designed for optical transmission. These parameter changes allow the system to maintain electrical idle states during optical transmission, ensuring protocol compatibility while enabling extended transmission distance through optical cable.
2Stability of the object's composition
If electrical Idle (differential signal below 65 mV) is transmitted over optical cable, then electrical idle state is maintained, but random noise is detected and sent over the cable, which interferes with the PCIe protocol
Solution Approach 1:
The patent converts the harmful effect of random noise generation into a beneficial solution by introducing artificial idle ordered sets (OIOS) that are specifically designed for optical transmission. Instead of allowing random noise to be generated from electrical idle signals, the system transmits controlled optical idle signals that maintain the electrical idle state without generating harmful noise, thus converting the problem into a solution.
3Device complexity
If Optical/Electrical interfaces behave like a simple repeater with fixed de-emphasis, then device complexity is reduced, but the 8.0 GT/s link equalization procedure is interfered with
Solution Approach 1:
The patent introduces dynamic equalization capabilities into the retimer device, allowing it to adapt its de-emphasis settings based on the specific link conditions and data rate requirements. This dynamic adjustment enables proper 8.0 GT/s link equalization while maintaining reasonable device complexity through programmable equalization parameters rather than fixed hardware settings.
4Adaptability or versatility
If side band signals are used to support hot plug and PERTSN in CEM specification, then adaptability is improved, but these signals are not supported over optical interface
Solution Approach 1:
The patent implements multi-functionality in the retimer device by integrating both the primary PCIe data path and the side band signal path within a single optical interface. The device can handle hot plug events, PERTSN signals, and data transmission through the same optical connection, eliminating the need for separate signal paths and reducing overall system complexity while maintaining adaptability.
Data Source
AI summary
Operation of a PCIe Retimer over an Optical Cable has been disclosed. In one implementation a Optical Idle ordered set (OIOS) is introduced as well as a high Z ordered set (HZOS).