In most cases you will find standard boots on the connectors. That being said, when examining the connector boots know that singlemode boots are generally blue or white in color. Multimode connector boots are usually beige or black. Looking at the boot color can be the first indication to you of that particular fiber optic connector mode type. You can save yourself further investigation time if you look for these obvious color differences in the boot. Be aware that, fiber optic connector boots can be custom ordered and there is a small chance you could be looking at a special ordered boot and this could throw off your investigation.

The main difference between singlemode and multimode fiber optic connectors is the ferrule of the connector. Singlemode connectors will almost always have a Zirconia (ceramic) ferrule while multimode connectors can be made of stainless steel (Nickel-Silver), composite (plastic), or Zirconia. identifying the material in which these ferrules are made of can also sale you time in investigating your connector types. Lastly, the size of the hole in the center of the ferrule will be the end all determining factor to identify the correct fiber type that the connector is designed for. A standard singlemode Zirconia ferrule will usually have a ferrule hole of about 126 microns, while standard multimode ferrules will be closer to 127-128 microns. The difference is very small, but can make a large impact on insertion loss if the larger multimode ferrule is used on singlemode fiber. We are talking about microns here so it could be hard to accurately identify the diameters of these holes with the naked eye.

If you find yourself faced with the task of identifying fiber optic mode types be sure to follow these steps and it might save you a bunch of time calling around for support or researching for information on the web. Always remember the best way to tell the two connectors apart is to keep them in their original packaging until ready for use.