Optical Module Link Training Using Out-of-Band Synchronization
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Solution Overview
Problem
Existing link training methods for optical modules and host devices face interoperability issues and race conditions due to unsynchronized clock timings and untrained links, particularly when auto-negotiation is not performed, leading to repeated timeouts and inefficient synchronization.
Innovation Solution
Implementing out-of-band link training for in-band links between host devices and optical modules, using out-of-band signals to independently train each link, and utilizing IDLE signals to maintain synchronization until both links are fully operational.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional in-band link training is used, then the link training process is simple, but race conditions and timeouts occur due to unsynchronized clock timings
Solution Approach 1:
The patent divides the link training process into two independent phases: out-of-band link training (for clock synchronization and parameter adjustment) and in-band link training (for data transmission). This segmentation allows the transmission link and reception link to be trained independently and asynchronously, eliminating race conditions while maintaining manageable complexity through structured separation of concerns.
Solution Approach 2:
The patent performs out-of-band link training before in-band link training. The out-of-band training establishes synchronized clock timings and optimized parameters in advance, ensuring that when in-band training occurs, the foundations are already solidified. This preliminary action prevents race conditions during the subsequent in-band training phase.
2Adaptability or versatility
If auto-negotiation is not performed, then device complexity is reduced, but interoperability issues arise due to unsynchronized clock timings
Solution Approach 1:
The patent introduces out-of-band signals as an intermediary mechanism for clock synchronization and parameter adjustment. These out-of-band signals act as a mediator between the transmission and reception links, enabling coordinated synchronization without requiring complex auto-negotiation protocols. The intermediary layer simplifies the overall system while ensuring interoperability.
3Loss of time
If links are trained simultaneously, then time efficiency is improved, but race conditions occur due to unsynchronized timing
Solution Approach 1:
The patent segments the training process into sequential phases: first out-of-band training for both links to establish synchronization, then independent in-band training for transmission and reception links. This segmentation eliminates race conditions by ensuring synchronization is established before data transmission training begins, while the independent in-band training allows parallel processing to maintain time efficiency.
Solution Approach 2:
The patent performs out-of-band training as a preliminary action before in-band training. This preliminary synchronization phase ensures that clock timings are aligned and parameters are optimized before the actual data transmission training occurs. The preliminary action prevents race conditions while the subsequent parallel in-band training maintains time efficiency.
Data Source
AI summary
A first optical module includes an optical transceiver and a chip. The optical transceiver, subsequent to completion of link training of an in-band transmission link between the first optical module and a host device, waits for a second optical module to come up including transmitting a first awake signal from the first optical module to the second optical module, and receives a second awake signal from the second optical module when the second optical module is up. The chip i) based on a first out-of-band signal transmitted via an out-of-band link, performs the link training of the in-band transmission link independently of an in-band reception link between the first optical module and the host device, and ii) based on the second awake signal and a second out-of-band signal transmitted via the out-of-band link, performs link training of the in-band reception link independent of the in-band transmission link.