De-skewing Electrical Signals Using Optical Loopbacks
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Solution Overview
Problem
The high cost and limited robustness of using a digital communications analyzer (DCA) for determining transmit and receive PHY skews in network elements with optical interfaces, making it unsuitable for long-term use in manufacturing environments and increasing production costs.
Innovation Solution
A method and apparatus that use electrical or optical loopbacks to measure and compute transmit and receive skew times between pairs of lanes in a network element's electrical interface, allowing for de-skewing without the need for expensive and precise DCA instruments, by employing different loopback configurations to determine individual skew times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a digital communications analyzer (DCA) is used to determine transmit and receive PHY skews, then measurement precision is improved, but manufacturing cost increases and device robustness deteriorates
Solution Approach 1:
The patent replaces the expensive DCA instrument with inexpensive loopback configurations that can be easily manufactured and disposed of. The loopback method uses simple electrical or optical connections that are already present in the device under test, eliminating the need for costly external measurement equipment while maintaining adequate measurement precision for skew determination.
Solution Approach 2:
The device measures its own skew characteristics using internal loopback paths. By configuring transmit and receive lanes to loop back through the device itself, the system performs self-diagnosis without requiring external sophisticated instruments. The skew measurement is derived from the device's own signal paths, making the measurement process self-sufficient and cost-effective.
2Measurement precision
If a digital communications analyzer (DCA) is used to determine transmit and receive PHY skews, then measurement precision is improved, but device robustness in manufacturing environment deteriorates
Solution Approach 1:
The loopback configuration uses simple, robust electrical or optical connections that are inherently more durable than the精密 DCA instrument. These loopback paths are designed to withstand manufacturing environment stresses and can be repeatedly used without degradation, unlike the fragile high-precision measurement equipment.
Solution Approach 2:
The loopback configuration acts as an intermediary that bridges the transmit and receive lanes within the device. This internal mediator is more robust to manufacturing variations and environmental conditions compared to external DCA equipment, while still enabling accurate skew measurement through the device's own signal paths.
3Ease of manufacture
If multiple loopback configurations are used to measure skew times, then manufacturing cost is reduced, but device complexity increases
Solution Approach 1:
The skew measurement process is segmented into multiple independent loopback configurations, each measuring specific lane pairs. By dividing the overall measurement task into separate, manageable segments (different loopback patterns), the system can use simple individual measurements that combine to provide complete skew characterization, avoiding the need for a single complex measurement system.
Solution Approach 2:
The loopback configurations are dynamically reconfigured to measure different lane pairs sequentially. The system adapts the loopback pattern based on which skew measurements remain to be taken, optimizing the measurement process while using simple static loopback structures. This dynamic reconfiguration allows complete skew measurement with minimal hardware complexity.
Data Source
AI summary
A method and apparatus of a device that determines transmit and receive skew times between pairs of lanes of an electrical interface of a network element is described. In an exemplary embodiment, the device couple an optical loopback to transmit and receive interfaces of an optical interface, the optical loopback capable of transporting a first optical signal with a plurality of polarization and quadrature combinations. In addition, the device determines the receive skew time by transmitting a second optical signal on the optical loopback with one of the plurality of polarization and quadrature combinations. Furthermore, the device determines the transmit skew time by, tuning transmission delays on the transmit interface for a third optical signal with components corresponding to a pair of the plurality of polarization and quadrature combinations such that the third optical signal is recoverable on the receive interface.