When a high-speed signal enters or exits a component, such as a fiber optic connector, discontinuities and impedance mismatches will cause a reflection, or echo, which is know as return loss.

While insertion loss is measured as the resultant signal after it encounters a loss, return loss is seen as data enters the connector or is leaving the other end of the connector, and is a measurement of the signal that is reflected back. Ideally, a fiber connector in a system wants to have a very clean passage of a signal so return loss is desired to be minimal.

Return Loss values are expressed as dB. A typical specification could range from -15 to -60 dB, Most designers target –10dB as the critical value of connector performance and try to keep return loss lower than -10dB at the desired signal speeds. In most cases, -60 is more desirable.

The graph shows that via architecture has a large affect on the return loss of a connector. 

Therefore, designers can minimize via effects to optimize connector performance. The thru via has a worse effect on the signal reflection, or return loss, than the blind via.

In an optical fiber system, insertion loss is introduced by things such as Fibre Optic Pach Leads, Fibre Pigtails, fibre optic connectors, splices, and couplers.
According to industry standard, Ultra PC polished fiber optic connectors return loss should be more than 50dB,Angled polished generally return loss is more than 60dB. PC type should be more than 40dB.

During the fiber optic products manufacturing procedure, Exfiber have professional equipment to test the fiber optic products insertion loss and return loss, our products are 100% tested on each single piece before shipment, and they are fully compliant or exceed the industry standard.