Feasibility Analysis of Single-mode Dual-core Fiber Connected to Only One Core

　　In most cases, single-mode dual-core optical fibers cannot be used normally due to the following reasons:

　　1. Optical fiber coMMunication principle limitations

　　Duplex communication requirements:

　　Network devices (such as optical modules and switches) usually use duplex mode, which requires two optical fibers at the same time: one to send the signal (Tx) and one to receive the signal (Rx). If only one core is connected, two-way communication cannot be achieved, resulting in network interruption.

　　Exception to simplex mode:

　　Only in certain scenarios (e.g. one-way data tranSMission, testing environment), if the device supports simplex mode, a single fiber can be used temporarily. However, such devices are rare and require additional configuration.

　　2. Device compatibility

　　Optical module design:

　　Standard optical modules (such as SFP, QSFP) are all duplex designs and need to use optical fibers in pairs. If only one core is connected, the optical module may report an error or turn off the laser because it cannot detect the peer signal.

　　Switch/router interface:

　　The electrical or optical port of the network device requires duplex communication by default. Connecting only 1 core will cause the link negotiation to fail, and the port status is displayed as "Down".

　　3. Practical application risk

　　Performance loss:

　　The attenuation and dispersion of a single fiber can affect signal quality, especially over long distances.

　　Maintenance risks:

　　The use of a single core may violate wiring specifications, increasing the difficulty of subsequent investigation.

　　Conclusions and recommendations

　　Conventional scenario: Dual-core fiber must be used to ensure duplex communication.

　　Special scenarios: For single-core temporary transmission (e.g. testing), confirm that the device supports simplex mode and accepts performance limitations.

　　Long-term solution: It is recommended to route in standard duplex mode to avoid compatibility issues.

　　Summary: Single-mode dual-core fiber with only one core cannot be used in the vast majority of cases because network equipment relies on duplex communication. It may only be temporarily feasible in specific test or unidirectional transmission scenarios, but equipment support is required.