Fiber optic patch cable, also called fiber optic patch cord or fiber patch cord, is one of the most basic and important parts in optical communication. Fiber optic patch cable is generally used for linking the equipment and components in the fiber optic network, eg. linking between the fiber optic converter and termination box. At the ends of fiber optic patch cable, there are fiber optic connectors. In general, the fiber optic patch cable types are classified by the fiber optic connector types. The commonly used fiber optic patch cable types include SC fiber patch cord, ST fiber optic patch cord, LC fiber optic patch cord, FC fiber optic patch cord etc. In addition, if fiber optic patch cable has the same type of connector on both ends, we call it the same connector type fiber patch cable, otherwise, it is called hybrid fiber optic patch cables. According to its fiber cable mode or fiber cable structure, fiber optic patch cable can be divided into singlemode fiber optic patch cable and multimode fiber optic patch cable or simplex fiber optic patch cable and duplex fiber optic patch cable. Fiber optic patch cords are the simplest fiber optic elements, consisting of a short length of optical fiber with a connector on either end (Fig. 12.2). Since they are used to connect various componets and instruments in a fiber optic system, their characteristics in terms of loss and aging determine the overall performance of the system. In principle, when two patch cords are connected, if the fibers are identical, it should result in almost zero loss. In actual practice the loss may not be very small since the fiber may not be completely concentric with the connector center, there could be dust at the tip of the connector, or there could be misalignments when two patch cords are mated. Fiber Optic Patch Cord with different types of fibers and different connector types are available. Typical insertion loss of patch cords are about 0.4 dB, with a return loss of better than 50 dB. Actually, before starting this topic, it is necessary for us to review the basic knowledge of the fiber optic patch cable. Fiber optic patch cable, also known as fiber jumper or fiber optic patch cord, is a cable terminated with fiber connectors at both ends that allow it to be rapidly and conveniently connected to CATV (cable television), an optical switch or other telecommunication equipment. According to different optical connector types, fiber optic patch cables can be classified into LC, SC, ST, FC fiber optic patch cables, etc. And if the fiber optic patch cable has the same type of connectors at both ends, we call it the same connector type fiber optic patch cable, otherwise, it is called hybrid fiber optic patch cable. Furthermore, based on optical fiber mode, fiber optic patch cables can be categorized to single-mode fiber optic patch cable and multimode fiber optic patch cable. Moreover, from fiber cable structure aspect, fiber optic patch cables can be divided into simplex patch cable and duplex patch cable. Fiber optic patch cables have good repeatability, and interchange as well as excellent environmental adaptability. Thus they are widely deployed in most types of industries. Fiber optic patch cables are used in medical imaging, mechanical engineering, LAN applications, CATV networks, telephone lines, and so on. It has revolutionized the total network industry of telephones, cables, Internet, auto applications, etc. Here is an image of fiber optic patch cable shown below.