Optical discriminator for transmitting and receiving in both optical fiber and free space applications

Abstract

A bi-directional communication assembly is provided with commonly available optoelectronic components in a compact package. Diplex functionality is achieved by orienting the receiving detector at an angle with respect to the transmitting beam. An interference coating inside the detector, on the detector surface, or on a surface in intimate contact with the detector, reflects the transmitted beam while simultaneously allowing the receiving beam to pass through the coating to the light absorbing region. The combined function of the receiving detector, providing advantages of a common beam path and close proximity of the components, enable a compact package that can be placed within the space usually occupied by the transmitter light source alone.

1 . A discriminator for an electromagnetic signal moving in a direction along a path, the discriminator comprising: 
 a photodetector having an active region and at least one interference coating lying along the path and adapted for having the electromagnetic signal incident thereon, said interference coating adapted for apportioning the electromagnetic signal into a first sub-signal adapted for transmitting through said interference coating and to said active region and a second sub-signal adapted to be reflected by said interference coating.    
   
   
       2 . The discriminator according to  claim 1 , wherein the second subsignal is adapted to be incident on said interference coating at an oblique angle.  
   
   
       3 . The discriminator according to  claim 1 , wherein the photodetector and the interference coating are monolithic.  
   
   
       4 . The discriminator according to  claim 1 , wherein the interference coating is grown on an atomic level to form a part of said discriminator.  
   
   
       5 . The discriminator according to  claim 1 , wherein said interference coating is adapted to apportion the electromagnetic signal based on at least one of electromagnetic signal power, electromagnetic signal wavelength, and electromagnetic signal polarization.  
   
   
       6 . The discriminator according to  claim 1 , wherein a set of interference coatings define a Fabry-Perot filter.  
   
   
       7 - 25 . (canceled)  
   
   
       26 . The discriminator according to  claim 1 , further comprising a source adapted for emitting the second sub-signal at an oblique angle with respect to said interference coating; wherein said source is adapted for emitting the second sub-signal so as to be incident on said interference coating and to be reflected by said interference coating.  
   
   
       27 . The discriminator system according to  claim 26 , wherein said interference coating is of the type described as dichroic, bandpass, edge, notch, or comb, whereby said interference coating is adapted to at least partially reflect the second sub-signal and adapted to at least partially transmit the first first sub-signal.  
   
   
       28 . The discriminator according to  claim 26 , wherein said interference coating is adapted for reflecting at least 90% of the second sub-signal and adapted for transmitting at least 60% of the first sub-signal wavelength.  
   
   
       29 . The discriminator according to  claim 26 , wherein said interference coating is substantially polarization independent at said oblique angle.  
   
   
       30 . The discriminator according to  claim 26 , wherein said oblique angle is 45 degrees.  
   
   
       31 . The discriminator according to  claim 26 , wherein said source is a laser.  
   
   
       32 . The discriminator according to  claim 1 , wherein said photodetector is a PIN diode photodetector.  
   
   
       33 . The discriminator according to  claim 26 , further comprising a lens interposed between said source and said photodetector, said lens adapted to focus the second sub-signal onto said interference coating.  
   
   
       34 . The discriminator according to  claim 1 , further comprising a lens adapted to focus the a first sub-signal onto said interference coating.  
   
   
       35 . The discriminator according to  claim 1 , further comprising at least one modifying element adapted to be disposed in a beam of electromagnetic radiation, said modifying element being selected from the group consisting of at least one of a birefringent wave plate, a Faraday rotator, and a polarizing element.