Optical Loopback in Co-Packaged Optics
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Solution Overview
Problem
Optical ports in network switches with co-packaged optics are susceptible to damage during loopback testing due to contamination and mechanical forces from external cables or modules, leading to inefficiencies and potential port damage.
Innovation Solution
Integrate an optical loopback functionality into the photonic integrated circuit (PIC) associated with each optical port, allowing loopback testing without the need for external cables or modules, using variable optical attenuators to switch between standard communications and loopback testing modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external optical loopback cables or modules are used for testing optical ports, then loopback testing can be performed to ensure switch operation, but optical ports are susceptible to damage from contamination and mechanical forces
Solution Approach 1:
The loopback testing function is extracted from the external domain and integrated into the photonic integrated circuit itself. The PIC now contains internal loopback paths that allow testing without external cables, eliminating the harmful mechanical connections and contamination risks associated with external loopback modules.
Solution Approach 2:
An optical switch within the PIC acts as an intermediary that can route optical signals either to external optical ports for normal communication or to internal loopback paths for testing. This intermediary mechanism enables seamless switching between operational modes without requiring external loopback cables.
2Productivity
If manual plugging and unplugging of external loopback cables is performed to complete testing, then testing can be completed, but the process is time-consuming and increases risk of port damage
Solution Approach 1:
The system performs self-testing through integrated loopback paths within the PIC. The optical switch automatically routes signals for testing without requiring external intervention or manual cable manipulation, enabling rapid automated testing that eliminates time losses and reduces human error.
Solution Approach 2:
The loopback testing capability is pre-configured within the photonic integrated circuit during manufacturing. This preliminary integration of testing functionality allows for immediate testing upon device activation without requiring subsequent manual setup of external loopback cables, significantly reducing testing time.
3Measurement precision
If external optical loopback modules are used for testing, then transmitter and receiver functionality can be tested, but the optical ports are more susceptible to damage compared to electrical ports
Solution Approach 1:
The testing functionality is merged with the normal operational functionality within the same photonic integrated circuit. The optical switch can dynamically route signals to either external ports or internal loopback paths, combining both operational and testing functions in a single integrated device that eliminates the need for separate external loopback modules.
Data Source
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AI summary
A photonic integrated circuit (PIC) includes an optical transmitter and an optical receiver. An optical loopback is coupled to the optical transmitter and to the optical receiver and is configurable to provide in a communications mode a transmitted optical signal from the optical transmitter to an optical output node and to provide a received optical signal on an optical input node to the optical receiver. The optical loopback is further configurable in a loopback testing mode to optically isolate the received optical signal on the optical input node from the optical receiver and to provide the transmitted optical signal from the optical transmitter to the optical receiver. A PIC including the optical loopback enables improved optical loopback testing of optical ports that will be present on network devices including co-packaged optics.