It can be hard to tell them apart.
MPO, or "multi-fiber push on", is defined as such by International Electrotechnical Commision (IEC) and Telecommunications Industry Association/Electronic Industries Alliance (TIA/EIA) standards.
Specifically the IEC 61754-7 which defines the standard interface dimensions for the MPO family of connectors and the FOCIS 5 which presents the intermateablility standard for connectors with the designation of MPO.
MTP is a trademarked name used to describe a brand of MPO connectors, MTP is fully compliant with the above MPO specific standards, much like the difference between Kleenex® and facial tissue.
In conclusion, MTP connectors are created using a patented process while MPO connectors are created using a different, always advancing process. All MTP parts are MPO, but not all MPO are MTP. While there are slight differences in the branded MTP connectors they are still essentially MPO connectors.
Make sure to use our connector tool to help you narrow it down.