Fiber patch cords must use the same core diameter as the trunk cable. A large attenuation penalty will occur when using a 62. Traditionally, fiber links are made where pairs of fibers are crossed between patch panels so fiber 1 at one. ANSI/TIA/EIA, The Fiber Optic Association, Panduit, and Leviton recommend having every segment crossed: crossed patch cable : crossed permanent cable : crossed patch cable. Even. Polarity in fiber optic networks refers to the alignment of transmit (Tx) and receive (Rx) signals between interconnected devices. For this signal alignment to work. In any installation, it is important to ensure that the optical transmitter at one end is connected to the optical receiver at the other.