A Fabry-Perot cavity is the standard run of the mill cavity with two highly reflecting mirrors bouncing the light back and forth, forming a standing wave.
(A Fabry-Perot cavity; is; the standard run of the mill cavity with two highly reflecting mirrors bouncing the light back and forth, forming a standing wave)
A Fabry-Perot cavity
is
the standard run of the mill cavity with two highly reflecting mirrors bouncing the light back and forth, forming a standing wave