Tag Archives: UPC Polish

Selecting Right Fiber Optic Patch Cables

There are various fiber optic patch cables for different applications. Fiber optic jumper cables are available in OS1, OS2 single-mode types and OM1, OM2, OM3, OM4 multimode types. Fiber optic jumper cables are terminated on both ends with a high performance hybrid or single type fiber optic connector, such as SC, ST, FC, LC, MTRJ, or E2000 connector in simplex or duplex. How to choose right fiber optic patch cables for your networks? Here are 6 factors that you need to take into consideration.

Connector Type

A fiber optic patch cable is terminated on both ends with a fiber optic connector, such as LC connector, SC connector, ST connector, FC connector, or MPO/MTP connector. Different connectors are used to plug into different devices. If ports of devices in the both ends are the same, we can use fiber optic patch cables with the same type of connectors on both ends, such as LC LC cables, SC SC fiber patch cord, ST ST fiber patch cable, or MPO-MPO patch cables. If you want to connect different ports type devices, fiber optic patch cables with different types of connectors on both ends, like LC SC fiber patch cable, LC to ST fiber patch cable, or SC to ST fiber cable, may suit you.


Connector Polish Type

Other than choosing the right connector type, you also need to choose the right connector polish type, whether the same polish type of the same connector type or different polish types of different connector types on both ends, such as SC APC fiber patch cord, SC/APC to LC patch cable. The loss of APC connectors is lower than UPC connectors. Usually, the optical performance of APC connectors is better than UPC connectors. APC connectors are widely used in applications such as FTTx, passive optical network (PON) and wavelength-division multiplexing (WDM) that are more sensitive to return loss. But APC connector is usually more expensive than UPC connector. With those applications that call for high precision optical fiber signaling, APC should be the first consideration, but less sensitive digital systems will perform equally well using UPC.

Single-mode or Multimode?

Fiber optic patch cable has two propagation modes: multi-mode and single-mode. Single-mode fiber patch cord uses 9/125um glass fiber. It is designed for the transmission of a single ray or mode of light as a carrier and is used for long-distance signal transmission. Multimode fiber patch cord usually uses 50/125um or 62.5/125um glass fiber. It can carry multiple light rays or modes, each at a slightly different reflection angle within the optical fiber core. Multimode fiber optic patch cables is used for relatively short distances because the modes tend to disperse over longer lengths. Typical single-mode fiber optic patch cable used yellow fiber cable and multi mode fiber optic patch cable used orange or aqua fiber cable.


Simplex or Duplex?

Do you need simplex or duplex fiber optic patch cords? There is only one single strand of glass or plastic fiber in a simplex fiber optic patch cord. It is often used where only a single transmit and/or receive line is required between devices. A simplex fiber optic patch cord has only one fiber optic connector at each end, often used for Bidirectional (BiDi) fiber optic transceivers. A duplex fiber patch cord consists of two strands of glass or plastic fiber which are typically found in a tight-buffered and jacketed “zipcord” construction format. The duplex fiber is most often used for duplex communication between devices where a simultaneous and separate transmit and receive are required. Duplex fiber patch cords are used for common transceivers. Simplex and duplex fiber patch cords both are available in single mode and multi-mode.


Cable Jacket

Usually, there are three types of cable jacket: Polyvinyl Chloride (PVC), Low Smoke Zero Halogen (LSZH) and Optical Fiber Nonconductive Plenum (OFNP). You can see there features in figure below and choose the right one for your network.


Besides those three cable jacket types above, there is another common cable, armored cable. The double tubing and steel sleeve construction make these patch cables completely light tight, even when they are bent. These cables can withstand high crushing pressures, which makes them suitable for running along floors and other areas where they may be stepped on. The tubing also provides excellent cutting resistance, abrasion resistance, and high tensile strength.


Cable Length

Fiber optic jumper cables are made in different lengths, usually from 0.5m to 50m. You can choose an appropriate cable length according to the distance between the devices you want to connect.


When choosing a right fiber optic patch cord, you need to consider all these six factors carefully. Single-mode or multimode, simplex or duplex, APC or UPC connector polish type, which one is right for your networks? Which kind of fiber optic connector do you need, SC, ST, FC, LC, MTRJ, or E2000 connector? By figuring out what you need exactly and consider all these six factors, you can make appropriate choices for your applications.

Polish Types of Fiber Optic Connector Ferrule

Whenever a connector is installed on the end of fiber, light loss will be incurred. Some of this light loss is reflected directly back down the fiber towards the light source that generated it. These back reflections, or optical return loss (ORL), will damage the laser light sources and also disrupt the transmitted signal. Various polish profiles are used to accommodate different types of applications. The polish types of fiber optic ferrules we’ll discuss here are the flat surface, physical contact (PC), ultra physical contact (UPC), and angled physical contact (APC).

Flat Polish

The original fiber connector is a flat-surface connection, or a flat connector. The primary issue with flat fiber connectors is that when two of them are mated it naturally leaves a small air gap between the two ferrules; this is partly because the relatively large end face of the connector allows for numerous slight but significant imperfections to gather on the surface. A flat polish of the connector surface will result in a back reflection of about 16 dB. This is not much use for single mode fiber cables with a core size of just 8 or 9 ┬Ám, hence the necessary evolution to PC connectors.

flat fiber connector

PC Polish

The fiber ends are typically polished with a slight curvature, such that when the connectors are mated the fibers touch only at their cores. This is known as a “physical contact” (PC) polish. In a PC connector, the two fibers meet, as they do with the flat connector, but the end faces are polished to be slightly curved or spherical. This eliminates the air gap and forces the fibers into contact. PC type is usually required at least 40dB return loss or higher. The PC polish is the most popular connector end-face preparation, used in most applications.

UPC Polish

An improvement to the PC connector is the UPC connector. Ultra physical contact polishing refers to the radius of the end face polishing administered to the ferrule, the precision tube used to hold a fiber in place for alignment. A UPC polish results in a dome-shaped end face that aids in optimizing the connections between two jacketed fibers. The end faces are given an extended polishing for a better surface finish. UPC type is usually required at least 50dB return loss or higher. These connectors are often used in digital, CATV, and telephony systems.

APC Polish

An APC connector has a curved end face which is angled at an industry-standard eight degrees. Some instances require return losses of 60dB, only APC connectors can consistently achieve such performance. This is because adding a small 8 degree angle to the end-face allows for even tighter connections and smaller end face radii. APC type is usually required at least 60dB return loss or higher. These connectors are preferred for CATV and analogue systems. Single mode fiber optic cables can be with PC, UPC or APC polished connectors, while multi-mode there has no APC ones. The picture below shows PC, UPC and APC polish types.

fiber back reflection

By polishing and curving or angling the face of the fiber ends, the light loss is reduced. The different polishes of the fiber optic connector ferrules result in different performances of the cables, mainly on the back reflection. Each connector has a “polished face” that mates with the other connector. Sometimes you will see fiber optic patch cords advertised as LC/UPC multi-mode duplex fiber optic patch cord, or FC/APC single mode simplex fiber patch cable, etc. The latter acronyms tell the buyer the type of polished face. Knowing more about these four polish types of fiber optic ferrules may be beneficial to your organization.

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