Is it OK to contact authors of the research paper requesting an implementation?
That is three questions, i.e. two more than the allowed quota for a
post :-)

Seeking more information on a topic, within legal limits, is your privilege.

It is always OK to write to an author about any aspect of his works,
as long as it remains a civilized exchange (which is sometimes not
the case). It should be preferably clear that you have a technical level that justifies taking his time. This should show in the style of your request, not by listing degrees and achievements.  Just be very simple, clear, and direct.

He may reply or not, or tell you what are the limits on what he can
tell you if some of the work is confidential.

But you should first try to see what is available on the net from him
or others who may have collaborated.  People are usually friendly, but
sometimes swamped with requests, and try to save time by preparing
answers on their web site, or the web site of their organization.

So, writing is encouraged. Asking for more papers or implementation,
or experimental results, is fine. But always try to spare the time of
the people you write to, and avoid asking idle questions or using the
exchange of mail as free tutoring.

All papers, all writings are intellectual property (IP), including this
answer to you, which I happen to put under a creatve common licence,
so that you do not even notice it is intellectual property.

An IEEE paper is also IP, usually owned mostly by IEEE, but there are
many more detais to this (search the web for "open access" and "Berlin
declaration").

But the IP concerns only the text of the papers, not the ideas you can
find in it.  So you are quite free to rewrite the content of a
scientific paper (not a novel) in your own words and distribute it ...
with due acknowledgement to the original author as the creator of the
ideas, and reference to his original paper.

IEEE may own IP rights on a paper, but that implies in no way any
right on the implementation of the ideas, on the experimental results or other preliminary work conducted to produce the paper, or on derived work,
including the notes a teacher can write for his class on the topic of
the paper.

Does this answer your questions?