The correct answer is replacing the transceiver with one that matches the fiber type. Transceivers are designed to work with specific fiber types, such as multimode or single-mode, and using a mismatched transceiver can cause signal loss or complete link failure. Ensuring the correct transceiver is used for the specific fiber type will likely resolve the connectivity issue. Choosing a higher bandwidth transceiver or cleaning the transceiver will not correct a fundamental incompatibility between transceiver and fiber type. Updating the firmware might resolve software-related issues but would not correct a physical mismatch between the transceiver and the fiber.