Fiber optic adaptors (Also known as a fiber optic coupler or mating sleeve) are designed to connect two fiber optic cables together. Fiber optic adaptors are designed for multimode or single mode cables and have various features that help distinguish them from one another. When looking at adaptors there are several options and styles that can help determine which one will be appropriate. There are material differences. Different colors help to distinguish between fiber cable types, connector types and hybrid adaptors. Adaptors come in various versions to connect single fibers together (simplex), two fibers together (duplex), or sometimes four fibers together (quad). All adaptors play a vital role in fiber optics, which helps to carry optical signals all over the world.
Alignment Sleeve Material
One main difference between single mode and multimode adaptors is the material used for the sleeve that mates two male connectors together. Single mode typically uses a zirconia sleeve and multimode uses a phosphorus bronze inner sleeve. More recently, zirconia is even being used for multimode applications as well. This is important, as tolerances play a vital role when mating a fiber connector, especially those with a small core size. Since single mode connectors have a smaller core size, usually 9um, the tolerance for the two cores to be lined up has to be very tight. This is achieved by using the zirconia sleeves which have very tight tolerances. With multimode connectors having a bigger core size, they are usually 50um or 62.5um; the tolerance level can have more play than in single mode applications. Another difference that explains this is the type of light source being used on the network. Single mode fiber uses a laser light source and traditional multimode optic cable uses LED light to pass the signal. To go even further, OM3 and OM4 are laser optimized fibers, and they use VCSELs (Vertical Cavity Surface Emitting Laser) which are also a laser source.
Color is helpful in determining what type of fiber cabling you have, but it also can help when looking at adaptors. Not only does the color helps you identify if it is single mode or multimode, it also helps you distinguish the type of polish on the connector or coupler endface. Mainly, this applies to single mode connectors.
Multimode fiber has several different size cores and it also has different bandwidth capacities for the 50um core fibers. For 62.5um fiber the color associated with this is beige, therefore beige adaptors are typically used for 62.5. Dealing with 50um fiber is when you have to pay attention to all details.
There are four different types of 50um fiber OM2, OM3, OM4 and OM5. Let’s start with OM2 as this one can be difficult to comprehend since it has the same orange color jacket as 62.5 fibers. The color that is typically used for OM2 is black for adaptors but beige is also used as well. That’s why it is safest to always look at the printed markings on the fiber optic cable jacket to know which fiber optic cabling you have. OM3 and OM4 can also get confusing as they both use aqua and so you will have to read the jacket as well to be sure. OM4 however does have another color that is being used – magenta. Magenta is not the industry standard color, but it can help you distinguish which type of fiber optic cable is in place.
For single mode it is a little easier as there are only two color adaptors that are typically used. There is blue which lets you know you have a single mode connector but it also lets you know that it is a UPC (Ultra Physical Contact) polished connector or slightly rounded on the edges. There are also the color green adaptors, which indicate it is an APC (Angled Physical Contact) polished connector. On the APC polish, this connector has an 8 degree angle that helps lower the amount of back reflection the connector has. Applications such as FTTx use these optical fiber connectors that require very low back reflection to achieve signals over long distances.
Fiber Connector Styles
Just like optical connectors have different styles, adaptors have several different style types as well. Such as the number of connectors the adaptor can accommodate. Starting with simplex adaptors; which means that it will mate one fiber to another fiber. There are duplex adaptors; which allows you to mate a pair of fibers to another pair. This is vital as many systems use one fiber for transmitting and one fiber for receiving signals. Also with smaller connectors such as the LC fiber connector, there are also quad adaptors which help save space, so more connectors fit into a smaller space. These are also known as high density applications – where the object is to try to pack as many connectors as possible into the smallest area.
There are flanged adaptors. This means that they have little tabs on each side that allow you to screw the adaptor down so it doesn’t move. On the other side there are adaptors that are called no flange. They really do have a flange, but it is smaller than a regular flanged adaptor and does not allow you to put any screws in.
Another style of adaptor is shutter adaptors. Shutter adaptors help to prevent dust from getting in and causing havoc on your optical connectors. There are adaptors that have external shutters and there are some out there that have internal shutters.
Another solution that can be used rather than shutters are dust caps. These caps cover unused ports, and they also play a couple vital roles for your fibers. Not only are they helping to prevent material and other objects that could damage your fiber connector endface from getting inside the mating sleeve, but they also help provide safety for the technicians. When working with single mode fiber you are using light sources that are lasers, these lasers are powerful and if you look directly into them, they can cause damage to your eyes. Moral of story is – Better to be Safe than Sorry.
Along with the traditional adaptors that mate two of the same style connectors together, there are also hybrid adaptors. These can be a couple different varieties that can include female to female and male to female. Typically hybrid adaptors help to mate two different style connectors together. For example, you have a piece of equipment that has a patch cord with a male SC connector on it. The switch that you need to plug into has a female LC port. In this instance, you would get a SC female to a LC male adaptor so you can connect the patch cord with the switch port.