Is there one word for "fade in, fade out"?
Are you referring to one scene fading out and another fading in in its place? If so, for video, that is called a dissolve. Wikipedia describes it as:
... a gradual transition from one image to another. [...] A dissolve overlaps two shots for the duration of the effect, usually at the end of one scene and the beginning of the next.
The Oxford Living Dictionaries concur:
dissolve
NOUN
An act or instance of moving gradually from one image or scene in a film to another.
‘the alternatives to a cut are fades or dissolves’
In the audio world, that's typically called a cross-fade. Per the Oxford Living Dictionaries:
cross-fade
VERB
[NO OBJECT]
(in sound or film editing) make a picture or sound appear or be heard gradually as another disappears or becomes silent.
‘there's some imaginative use of cross-fading’
NOUN
An instance of cross-fading.
If you're thinking of one scene fading out and then the same scene fading in, I'm not sure what that would be called other than to pulse:
pulse
VERB
[no object] Throb rhythmically; pulsate.
‘a knot of muscles at the side of his jaw pulsed’
Although I suspect folks would understand fade in and out much better.