Single mode patch cables are normally used in long distance fiber application. For example, today all long distance telephone lines are all in Single Mode fiber as this fiber is designed for the highest Bandwidth and very long distances. The Single mode core is only 9 µm and therefore it is of the utmost importance that its center is very well aligned in order to guarantee a quality connectivity. The most important technical element in a Single mode patch cable is the Return Loss. Yesterdays standard of -40 dB loss are no longer acceptable and a minimum of -50dB or a -60dB for APC finish is required.