In article 2,
John Schutkeker wrote:
I wanted to build an optical imaging interferometer that worked over a
phone line.

How were you planning on downconverting the terahertz frequency
optical frequencies to a bandwidth a phone line could handle?

I'm not a heterodyne savant, but somebody told me that lasers might do it,
although I'm still open to suggestions.

You apparently missed my point, which is no one knows how to
downconvert an optical frequency to something lower.

Radio interferometers such as the VLA have detectors that make use of
the wave nature of the radiation, so they mix with with a local
oscillator, convert to voltages, and then combine the signals in a
correlator.

Optical interferometers have vaccuum delay lines, mix the light beams
physically, and then have APD or CCD detectors to measure the fringes.

The reason I asked you how you were planning on downconverting the
signal was a hint that the technology of doing what you asked for
doesn't exist.

I'm willing to sacrifice bandwidth for twisted pair (or shielded twisted
pair) because the heart of the idea is to gain distance (which translates
to aperture size) cheaply.

What is the bandwidth you think you can get out of twisted pair? If
you express that as a fraction bandwidth of an optical signal (a few
hundred terahertz) what sort of fractional bandwidths are you seeing?
If too low you'd need the Keck telescope to measure Sirius.