PCIe Active Optical Cable Detection Circuit
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Solution Overview
Problem
Existing PCIe links face challenges in detecting the presence of active optical cables (AOCs) due to the absence of input stage terminals with resistors referenced to the ground level in electrical-to-optical PCIe transceivers, which hinders effective receiver detection.
Innovation Solution
Incorporating a detection condition circuit with decoupling capacitors and inductive impedances referenced to the ground level within the electrical-to-optical PCIe transceivers, allowing for the creation of a receiver detection condition that enables the detection of AOCs by forming equivalent terminals with single-end direct current impedance, even in the absence of common mode voltage output terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an electrical-to-optical PCIe transceiver is used in an AOC, then optical signal transmission is enabled, but the transceiver lacks input stage terminals with resistors referenced to ground level, preventing receiver detection
Solution Approach 1:
The patent introduces an intermediary detection condition circuit that includes a capacitor and inductor, which creates an equivalent terminal with terminating impedance. This intermediary circuit acts as a mediator between the AOC transceiver and the receiver detection circuit, enabling detection without requiring the transceiver to have native input stage terminals with resistors.
2Difficulty of detecting and measuring
If input stage terminals with resistors are added to the transceiver, then receiver detection is enabled, but the transceiver structure becomes more complex
Solution Approach 1:
The detection condition circuit is designed to serve multiple functions: it creates the necessary terminating impedance for detection, works with existing AOC transceiver structures, and maintains compatibility with current PCIe protocols. By making the circuit universal, the patent avoids adding complex dedicated detection hardware while still achieving reliable detection.
Data Source
AI summary
A peripheral component interconnect-express (PCIe) link with presence of an active optical cable (AOC) that couples between an electrical PCIe (E-PCIe) transmitter and an E-PCIe receiver may include the AOC. The AOC may include an electrical-to-optical PCIe (EO-PCIe) transceiver coupled to the E-PCIe transmitter. The EO-PCIe transceiver may include a laser diode driver that includes a common mode voltage output terminal. The EO-PCIe transceiver may include a detection condition circuit that includes a decoupling capacitor. The decoupling capacitor may be referenced to a ground level and may connect to the common mode voltage output terminal of the laser diode driver. The detection condition circuit may create a receiver detection condition for a receiver detection circuit of the E-PCIe transmitter to detect presence of the AOC.