For backbone and riser multifiber cable, installers should always follow the color code and numbering system below for A-B polarity, as defined in TIA-598-C Optical Fiber Cable Color Coding. 0 Standard (Commercial Building Telecommunications Cabling Standard) defines the A-B polarity scenario for discrete duplex patch cords, with the premise that transmit (Tx) should always go to receive (Rx) — or "B" should always connect to "A" — no matter how many segments there are. Fiber polarity is the direction that light signals travel from one end of a fiber optic cable (link) to the other. A link's transmit signal (Tx) must match its corresponding receiver (Rx) at the other end. Although it may seem obvious, fiber optic polarity is a frequent source of confusion and. Since most fiber optic links use two fibers transmitting in opposite directions to create a full duplex link, you need to ensure that transmitters are connected to receivers and vice versa. This ensures consistent Tx/Rx matching across all connections, making it possible for complex network systems to operate without interruptions. For duplex transmission, this is relatively straightforward to accomplish. An A-B duplex. TIA-568-C standards recommend an A-B polarity scenario for duplex patch cords.
