Multi-Lane Optical Transceiver Clocking for Error-Free Lane Switching
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Solution Overview
Problem
Existing multi-lane optical transceivers face challenges in seamlessly switching lanes without causing bit errors due to high silicon area and power consumption from multiple on-chip phase interpolators or phase locked loops, and they struggle to maintain accurate frequency information transfer during configuration changes.
Innovation Solution
Implement a firmware-based feedback loop in multi-lane optical transceivers that uses a tunable oscillator and a master lane to dynamically track frequency errors, allowing seamless lane switching with reduced hardware and power consumption by utilizing a single phase-locked loop per transmitter path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple on-chip phase interpolators or phase locked loops are used per lane, then seamless lane-switching capability with independent tracking is achieved, but silicon area and power consumption increase
Solution Approach 1:
The patent merges multiple independent PPM tracking circuits into a single shared PPM tracking circuit that serves all lanes. The phase interpolator and phase locked loop are implemented as shared resources that can be dynamically allocated to different lanes through firmware control, eliminating the need for separate hardware instances per lane while maintaining seamless lane-switching capability
Solution Approach 2:
The system implements dynamic lane assignment where a single phase interpolator/PLL can be flexibly assigned to track different lanes based on current operational requirements. The firmware dynamically configures which lane is being tracked and updates the PPM information accordingly, enabling adaptive resource utilization without hardware redundancy
2Reliability
If multiple on-chip phase interpolators or phase locked loops are used per lane, then independent PPM tracking per lane is achieved, but power consumption increases
Solution Approach 1:
Multiple PPM tracking functions are merged into a single power-efficient circuit implementation. The shared phase interpolator and PLL consume significantly less power than multiple independent instances would require, while firmware orchestration ensures that PPM tracking is maintained for all active lanes through time-multiplexed operation
Solution Approach 2:
The system uses firmware-based resource management to self-allocate the single PPM tracking circuit to different lanes as needed. The firmware monitors lane activity and dynamically directs the shared hardware resources to the appropriate lane, eliminating the need for dedicated hardware per lane while maintaining tracking accuracy
3Adaptability or versatility
If configuration changes are made in multi-lane transceivers, then adaptability is improved, but frequency information transfer accuracy deteriorates due to bit errors
Solution Approach 1:
The system performs preliminary PPM tracking and frequency error correction on the master lane before configuration changes are applied. By pre-characterizing the frequency offset and applying corrective phase adjustments in advance, the system ensures that frequency information remains accurate during and after configuration transitions, preventing bit errors
Data Source
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AI summary
Frequency error tracking and lane monitoring techniques for multi-lane optical transceivers are provided. In one aspect, a method includes capturing phase and frequency information recovered by clock-and-data recovery circuits from data traveling along a plurality of lanes of an optical transceiver, with one of the lanes being a master lane; determining a frequency error based on the phase and frequency information of the master lane; outputting, by a tunable oscillator, a reference clock based on the frequency error; and controlling the optical transceiver based on i) a transmitter clock signal generated by a transmitter phase-locked loop (PLL) using the reference clock signal, and ii) a receiver clock signal generated by a receiver PLL using the reference clock signal.