A fiber optic patch cord is a fiber optic cable having connectors at either end, which let it to be quickly and easily connected to optical transceiver in switch, router, or any other telecommunication equipment like optical line termination (OLT) or optical network terminal (ONT).
A fiber optic patch cord is made with a core having high refractive index, which is surrounded by a coating called cladding having low refractive index. That cladding again is reinforced and surrounded by a shielding cover for protection purpose. The core allows the transfer of optic signals with very little loss for great distances. The lower refractive index of cladding let the light back into the core. The light is reflected back into to core by phenomenon called total internal reflection. The protective shield over the cladding reduces physical damage to the core and cladding.
Regular fiber cable cladding measure 125 µm in diameter. As shown in the figure the core (inner diameter) measures 9 µm for single-mode cables, and 50 or 62.5 µm in multi-mode cables. Fiber cords can be categorized by transmission medium (shorter or longer distance) and by connector construction. Single mode fibers are generally yellow in color, having a blue connectors, and can achieve a longer transmission path. Whereas, multi-mode fibers are usually orange in color, having a cream color connector, and they can cover shorter transmission distance.
Standard connector design have LC, ST, SC, FC, MTRJ, MPO, MU, SMA, FDDI, E2000, DIN4, and D4. Fiber path cords are often classified by the connectors on the cable; some of the most common cable formations include FC-FC, SC-SC, FC-LC, FC-SC, FC-ST, and SC-ST.
LC known as Little Connectors, are small in size and are widely used in SFPs. ST knows as straight tip are similar to BNC connectors, widely used in fiber ODF. SC known as subscriber channel, these are larger in size as compare to LC, widely used in GBIC transceivers. MTRJ are the same as the size of RJ45 connectors. MU fiber optic connector have push-pull function, composed of plastic housing. It is almost half the size of SC connector. E2000 connector have push-pull connection mechanism, they have an automatic shutter inside for protection from dust. Fiber optic patch cords are formed in different ways, like SC-LC or SC-FC these types of cable are common connecting SFP transceivers from routers or switches to the fiber ODF. SC-SC, FC-FC and LC-LC simplex cables can be used to provide physical level optical loops. There are also different types of fiber optic patch cords, some of the types are mentioned below.
Armored Fiber Patch Cord:
Flexible stainless steel is used inside the outer lacked as the armor to protect fiber inside armored fiber optic patch cord. It holds all the features of typical fiber patch cord, however is quite stronger. These type of cable are widely used in longer distance transmission systems. Direct buried fibers, aerial fibers and undersea fiber optic cables are example of armored fiber optic cables. Each having their extra protection according to their application.
Bend Insensitive Fiber Optic Patch Cord:
Bend insensitive fiber patch cords are widely used in FTTH. This type of fiber is not sensitive to pressure and bending. As the fiber patch is not sensitive to pressure and bending, it can be easily used in cable ducts, or inside cable covers along with the walls. Bend insensitive fiber patch cord are sub divided into two categories, category A include G657A1 and G657A2, category B include G657B2 and G657B3 types of fiber. Bending radius for G657A1 fibers can be as low as 10 mm, for G657A2 and G657B2 it is 7.5 mm, the G657B3 can work on bending radius of 5 mm. this is to be noted here that G.657 Series fibers are single mode fibers.
Mode Conditioning Patch Cord:
Mode conditioning patch cords are necessary where Gigabit 1000 Base-LX switches and routers are installed into present multimode cable plants. When a single mode signal is launched into multimode fiber a phenomenon called Differential Mode Delay (DMD) can create multiple signals within the multimode fibers. This effect can confuse the receiver and produce the errors. These multiple signals, caused by DMD, severely limit the cable distance lengths for operating Gigabit Ethernet. A mode conditioning patch cord eliminates these multiple signals by letting the single-mode launch to be offset away from center of the multimode fiber. This offset point creates a launch that is similar to typical multimode LED launch and the resulting multiple signals allowing the use of 1000base-LX over existing multimode cable system.
Fiber optic patch cords are widely used from telecommunication networks to cable TV, from Local Area Network (LAN) to Wide Area Network (WAN), from transmission networks to data centers. As far as the right type of fiber optic patch cord is used, they have vast number of applications.