Optical apparatus for optical communication terminal and optical communication system

An optical apparatus for use in bidirectional optical communication comprising:

• a common terminal used to receive diverging light with a short wavelength and to output light with a long wavelength which is longer than the short wavelength;
• an input terminal used to receive diverging light with the long wavelength from a light source;
• an output terminal used to send out light with the short wavelength to a light receiver;
• a wavelength selecting filter adapted to cause said light with the short wavelength transmitted from said common terminal to pass toward said output terminal and to reflect said light with the long wavelength transmitted from said input terminal to selectively direct said light with the long wavelength to said common terminal;
• first and second computer-generated holograms used to guide said diverging light with the long wavelength transmitted from said input terminal to said common terminal via said wavelength selecting filter and to cause said light with the long wavelength to converge;
• and
• a third computer-generated hologram used to cause said light with the short wavelength transmitted from said common terminal through said second computer-generated hologram to converge to said output terminal,
• wherein said light receiver and said third computer-generated hologram are located on one side of said wavelength selecting filter, and said common terminal, said input terminal for said light source, and said first and second computer-generated holograms are located on the other side of said wavelength selecting filter.