System comprising optical semiconductor waveguide device

Abstract

An improved optical communication system is provided, the system particularly suited for so-called short-haul applications, e.g., applications involving transmission over distances less than 100 km, such as metro applications. The system uses an external cavity laser made up of a gain medium that comprises an active region, a beam expanding region, and an antireflective layer, an optical waveguide located adjacent the gain medium, and a Bragg grating integral with or coupled to the optical waveguide. The medium and the optical waveguide, due to the beam expanding region, exhibit a coupling efficiency of at least 40%, advantageously at least 50%, even in the absence of coupling optics, and the laser is configured and operated to emit at least two modes.

What is claimed is:  
     
         1 . An optical communication system comprising an external cavity laser that comprises: 
 a gain medium comprising an active region, a beam expanding region, and an antireflective layer on a first surface of the gain medium.    an optical waveguide located adjacent the gain medium such that at least a portion of the electromagnetic energy generated by the active region passes through the beam expanding region and through the antireflective layer into the optical waveguide; and    a Bragg grating integral with or coupled to the optical waveguide,    wherein the medium and the optical waveguide exhibit a coupling efficiency of at least 40% with or without the presence of coupling optics located between the gain medium and the optical waveguide, and    wherein the laser is configured and operated to provide a multimode output of at least two modes.    
     
     
         2 . The system of  claim 1 , wherein the coupling efficiency is at least 40% with or without the presence of coupling optics located between the gain medium and the optical waveguide.  
     
     
         3 . The system of  claim 1 , wherein the gain medium comprises a cavity less than 1 cm in length.  
     
     
         4 . The system of  claim 1 , wherein the length of the system is less than 100 km.  
     
     
         5 . The system of  claim 1 , wherein the laser is operated by direct modulation.  
     
     
         6 . The system of  claim 1 , wherein the bit error rate of the system is less than 10 −9 .  
     
     
         7 . The system of  claim 6 , wherein the bit error rate of the system is less than 10 −12 .  
     
     
         8 . The system of  claim 1 , wherein the laser is operated at 2.5 GHz or greater.  
     
     
         9 . The system of  claim 1 , wherein the laser is operated in the absence of a temperature-compensating apparatus.  
     
     
         10 . The system of  claim 1 , wherein the gain medium and optical waveguide are coupled in the absence of coupling optics.  
     
     
         11 . An optical communication system comprising an external cavity laser that comprises: 
 a gain medium comprising an active region, a beam expanding region, and an antireflective layer on a first surface of the gain medium;    an optical waveguide located adjacent the gain medium such that at least a portion of the electromagnetic energy generated by the active region passes through the beam expanding region and through the antireflective layer into the optical waveguide; and    a Bragg grating integral with or coupled to the optical waveguide,    wherein the medium and the optical waveguide exhibit a coupling efficiency of at least 40% in the absence of coupling optics located between the gain medium and the optical waveguide,    wherein the laser is configured and operated to provide a multimode output of at least two modes,    wherein the laser is operated by direct modulation,    wherein the laser is operated in the absence of a temperature-compensating apparatus,    wherein the gain medium comprises a cavity less than 1 cm in length, and    wherein the length of the system is less than 100 km.    
     
     
         12 . The system of  claim 11 , wherein the coupling efficiency is at least 40% with or without the presence of coupling optics located between the gain medium and the optical waveguide.  
     
     
         13 . The system of  claim 11 , wherein the bit error rate of the system is less than 10 −9 .  
     
     
         14 . The system of  claim 13 , wherein the bit error rate of the system is less than 10 −12 .  
     
     
         15 . The system of  claim 13 , wherein the laser is operated at 2.5 GHz or greater