In contrast, a dual-fiber optical module features two ports: TX (transmit) for emitting optical signals and RX (receive) for receiving optical signals. Two. The secret lies in fiber optic technology, and understanding the basics—1-core, 2-core, Single Mode (SM), and Multi-mode (MM)—is key to mastering this field. Let's break down these terms in simple, clear language with practical examples. When the optical signals reach the receive optical bore through an optical fiber, they are converted back into electrical signals by the. Although both dual fiber SFP and simplex SFP modules are used to convert electrical signals to light signals, they differ in several ways, including transmission distance, fiber utilization, and use methods.