[Guy Harris <guy@xxxxxxxxxx>]

> I have been unable to open a capture file with tethereal and export it to a
> different file format.  I read the following snippet form the tethereal man
> page and assume that the bold words are the possible values for the -F
> argument.

Yes - well, I see no boldface in your message, but the list of capture
file formats it writes are:

> libpcap format (standard libpcap format, a modified
> format used by some patched versions of libpcap, or the format used by Red
> Hat Linux 6.1), snoop format, uncompressed Sniffer format, Microsoft Network
> Monitor 1.x format, and the format used by Windows-based versions of the
> Sniffer software
>  
> The only value that has worked for me is libpcap.

What do you mean by "has worked for me"?  Were you unable to use, say,
"-F ngsniffer" and get something readable by a Sniffer?

> I would like to export
> the file to one that is readable by Optimal.

Well, then, you'll have to figure out which of those formats is readable
by Optimal (whatever "Optimal" is).

If the answer is "none of them", then you *can't* export the file as
something readable by Optimal.