System and Method for Using Combining Couplers with Asymmetric Split Ratios in a Lidar System

Abstract

A laser radar, or “lidar” system, employs an asymmetric single-ended detector to detect received signals reflected back from targets. The asymmetric single-ended detector benefits from a reduced part count and fewer optical splices while nearly achieving a same gain as a symmetric differential detector.

What is claimed is: 
     
         1 . A lidar comprising:
 a laser source configured to generate a laser output;   a splitter configured to split the laser output into a transmit signal and a mixing signal; and   a single-ended detector comprising:
 an asymmetric combiner configured to combine a received signal and the mixing signal and output a combined signal, wherein the received signal is a reflected portion of the transmit signal reflected back from a target and received by the lidar, wherein the asymmetric combiner has a split ratio greater than 0.5, and 
 a detector configured to detect the combined signal. 
   
     
     
         2 . The lidar of  claim 1 , wherein the asymmetric combiner has a split ratio greater than or equal to 0.6. 
     
     
         3 . The lidar of  claim 1 , wherein the asymmetric combiner has a split ratio greater than or equal to 0.7. 
     
     
         4 . The lidar of  claim 1 , wherein the asymmetric combiner has a split ratio greater than or equal to 0.8. 
     
     
         5 . The lidar of  claim 1 , wherein the asymmetric combiner has a split ratio greater than or equal to 0.9. 
     
     
         6 . The lidar of  claim 1 , wherein the asymmetric combiner has an empirical split ratio of 0.8. 
     
     
         7 . The lidar of  claim 1 , wherein the asymmetric combiner has an empirical split ratio of 0.9. 
     
     
         8 . The lidar of  claim 1 , wherein the asymmetric combiner comprises an asymmetric combining coupler. 
     
     
         9 . The lidar of  claim 1 , wherein the detector comprises a PIN diode. 
     
     
         10 . The lidar of  claim 1 , further comprising a gain stage or an attenuation stage configured to adjust a power level of the mixing signal prior to input to the asymmetric combiner. 
     
     
         11 . A method for detecting a reflected signal from a target, the method comprising:
 receiving the reflected signal from the target;   combining the received signal with a mixing signal using an asymmetric combiner having a split ratio greater than 0.5 to generate a combined signal; and   detecting the combined signal using a single-ended detector.   
     
     
         12 . The method of  claim 11 , wherein the asymmetric combiner has a split ratio greater than or equal to 0.6. 
     
     
         13 . The method of  claim 11 , wherein the asymmetric combiner has a split ratio greater than or equal to 0.7. 
     
     
         14 . The method of  claim 11 , wherein the asymmetric combiner has a split ratio greater than or equal to 0.8. 
     
     
         15 . The method of  claim 11 , wherein the asymmetric combiner has a split ratio greater than or equal to 0.9. 
     
     
         16 . The method of  claim 11 , wherein the asymmetric combiner has an empirical split ratio of 0.8. 
     
     
         17 . The method of  claim 11 , wherein the asymmetric combiner has an empirical split ratio of 0.9.