Method and apparatus for providing multiport free-space wavelength-division multiplexing (wdm) device using a prism

A method of demultiplexing an optical light beam for a wavelength-division multiplexing (“WDM”) device, comprising:

• receiving an optical beam passing through free-space inside of a subassembly and guiding the optical beam to enter a first surface of a prism coupled with the subassembly;
• turning the optical beam in a first ninety (90) degree turn when the optical beam strikes a first side surface of the prism to generate a 90-degree optical beam traveling toward a second surface of the prim;
• turning the 90-degree optical beam in a second ninety (90) degree turn when the 90-degree optical beam hits the second surface of the prim to generate a first optical beam which is a 180 degree turned around optical beam;
• and
• extracting a first wavelength (“λ1”) from the first optical beam to form a first light signal with λ1 when the first optical beam reaches at the first optical filter, and forming a second optical beam with remaining wavelengths of the first optical beam.

A wavelength-division multiplexing (“WDM”) block able to receive a light beam from a WDM network, comprising:

• a subassembly having a first end and a second end wherein the second end is situated from opposite of the first end, the subassembly configured to be hollow in center of the subassembly for facilitating optical free-space communication;
• a plurality of thin film filters (“TFFs”) coupled to the first end of the subassembly and configured to separate a plurality of optical signals from a light beam and to reflect a portion of remaining optical signals in the light beam to predefined directions;
• and
• a prism coupled to the second end of the subassembly with a predefined angle and configured to guild the light beam to at least one of the plurality of TFFs in response to the predefined angle.