Method and apparatus for stretching an optical pulse

Abstract

A method and apparatus for stretching a pulse, shaping a stretched pulse, and modeling a stretched and/or shaped pulse are disclosed. An etalon has a port, a partially reflective surface, and a fully reflective surface. A base pulse is introduced into the etalon, and a plurality of portions of the base pulse propagating from the etalon are collected. The collected portions are then combined to generate a stretched pulse whose width is proportional to the width of the base pulse. This can be modeled by assigning a transmission factor value to each one of a plurality of tags and a reflection factor value to each one of the taps, excepting only one tap. A transport delay for is assigned to each tap to which a reflection factor value was assigned, wherein the transport delay is proportional to the width of a base pulse.

1. An etalon, comprising:
 a port through which a base pulse may be introduced;  
 a partially reflective surface against which the base pulse may impinge; and  
 a fully reflective surface spaced apart from the partially reflective surface in operative relationship to the partially reflective surface, the distance between the fully reflective and partially reflective surfaces being a function of predetermined proportionality between the width of an output pulse and the width of the base pulse.  
 
     
     
       2. The etalon of  claim 1 , wherein the partially reflective surface is graded. 
     
     
       3. The etalon of  claim 1 , wherein the distance is determined so that the time for an optical signal to reflect off the partially reflective surface, propagate to the fully reflective surface, reflect off the fully reflective surface, and propagate to the partially reflective surface is equal to an integer multiple of the width of the base pulse. 
     
     
       4. The etalon of  claim 1 , wherein at least one of the partially reflective surface and the fully reflective surface includes:
 a substrate; and  
 a coating on the substrate.  
 
     
     
       5. The etalon of  claim 4 , wherein the coating on the substrate is graded. 
     
     
       6. The etalon of  claim 4 , wherein the coating comprises a Ti/Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       7. The etalon of  claim 4 , wherein the coating comprises a Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       8. An etalon, comprising:
 means for introducing a base pulse into a cavity defined by the etalon;  
 means for partially reflecting the base pulse; and  
 means for fully reflecting the partially reflected base pulse spaced apart from the partially reflecting means in operative relationship thereto, the fully reflecting means being spaced apart from the partially reflective means a distance being a function of predetermined proportionality between the width of an output pulse and the width of the base pulse.  
 
     
     
       9. The etalon of  claim 8 , wherein the partially reflective means is graded. 
     
     
       10. The etalon of  claim 8 , wherein the distance is determined so that the time for an optical signal to reflect off the partially reflective means, propagate to the fully reflective means, reflect off the fully reflective means, and propagate to the partially reflective means is equal to an integer multiple of the width of the base pulse. 
     
     
       11. The etalon of  claim 8 , wherein at least one of the partially reflective means and the fully reflective means includes:
 a substrate; and  
 a coating on the substrate.  
 
     
     
       12. An optical pulse stretcher, comprising:
 a port through which a base pulse may be introduced;  
 a partially reflective surface against which the base pulse may impinge;  
 a fully reflective surface spaced apart from the partially reflective surface a distance that is a function of predetermined proportionality between the width of an output pulse and the width of the base pulse and in operative relationship to the partially reflective surface;  
 an optical collector capable of collecting a plurality of base pulse components propagating through the partially reflective surface; and  
 a combiner capable of combining the collected base pulse components and outputting a stretched pulse.  
 
     
     
       13. The optical pulse stretcher of  claim 12 , wherein the partially reflective surface is graded. 
     
     
       14. The optical pulse stretcher of  claim 12 , wherein the distance is determined so that the time for an optical signal to reflect off the partially reflective surface, propagate to the fully reflective surface, reflect off the fully reflective surface, and propagate to the partially reflective surface is equal to an integer multiple of the width of the base pulse. 
     
     
       15. The optical pulse stretcher of  claim 12 , wherein at least one of the partially reflective surface and the fully reflective surface includes:
 a substrate; and  
 a coating on the substrate.  
 
     
     
       16. The optical pulse stretcher of  claim 15 , wherein the coating on the substrate is graded. 
     
     
       17. The optical pulse stretcher of  claim 15 , wherein the coating comprises a Ti/Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       18. The optical pulse stretcher of  claim 15 , wherein the coating comprises a Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       19. The optical pulse stretcher of  claim 12 , wherein the optical collector comprises a lens. 
     
     
       20. An optical system, comprising:
 an optical receiver capable of receiving an optical signal;  
 an optical pulse stretcher, including: 
 a port through which a base pulse of the optical signal may be introduced;  
 a partially reflective surface against which the base pulse may impinge;  
 a fully reflective surface spaced apart from the partially reflective surface a distance that is a function of predetermined proportionality between the width of an output pulse and the width of the base pulse and in operative relationship to the partially reflective surface;  
 an optical collector capable of collecting a plurality of base pulse components propagating through the partially reflective surface; and  
 a combiner capable of combining the collected base pulse components and outputting a stretched pulse; and  
 
 a detector capable of processing the stretched pulse.  
 
     
     
       21. The optical system of  claim 20 , wherein the partially reflective surface is graded. 
     
     
       22. The optical system of  claim 20 , wherein the distance is determined so that the time for an optical signal to reflect off the partially reflective surface, propagate to the fully reflective surface, reflect off the fully reflective surface, and propagate to the partially reflective surface is equal to an integer multiple of the width of the base pulse. 
     
     
       23. The optical system of  claim 20 , wherein at least one of the partially reflective surface and the fully reflective surface includes:
 a substrate; and  
 a coating on the substrate.  
 
     
     
       24. The optical system of  claim 23 , wherein the coating on the substrate is graded. 
     
     
       25. The optical system of  claim 23 , wherein the coating comprises a Ti/Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       26. The optical system of  claim 23 , wherein the coating comprises a Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       27. The optical system of  claim 20 , wherein the optical collector comprises a lens. 
     
     
       28. A method for stretching an optical pulse, comprising:
 introducing a base pulse into an etalon, the etalon including a fully reflective surface spaced apart from a partially reflective surface a distance that is a function of a predetermined proportionality between the width of an output pulse and the width of the base pulse;  
 collecting a plurality of portions of the base pulse propagating from the etalon; and  
 combining the plurality of portions to generate a stretched pulse whose width is proportional to the width of the base pulse.  
 
     
     
       29. The method of  claim 28 , wherein collecting the plurality of portions includes focusing the portions on a combiner. 
     
     
       30. The method of  claim 28 , wherein combining the portions to generate a stretched pulse includes combining the portions to generate a shaped, stretched pulse. 
     
     
       31. The method of  claim 30 , wherein combining the collected portions to generate the shaped, stretched pulse includes combining the collected portions to generate a pulse having a shape selected from the group consisting of a staircase, a square, and a sinusoid. 
     
     
       32. The method of  claim 28 , further comprising grading the partially reflective surface. 
     
     
       33. The method of  claim 32 , wherein grading the partially reflective surface includes varying the thickness or density of a coating on a substrate. 
     
     
       34. An etalon, comprising:
   a partially reflective surface against which a base pulse may impinge; and        a fully reflective surface spaced apart from the partially reflective surface in operative relationship to the partially reflective surface, the distance between the fully reflective and partially reflective surfaces being a function of predetermined proportionality between the width of an output pulse and the width of the base pulse.     
     
     
       35. The etalon of  claim 34 , wherein the partially reflective surface is graded. 
     
     
       36. The etalon of  claim 34 , wherein the predetermined proportionality is equal to an integer multiple of the width of the base pulse. 
     
     
       37. The etalon of  claim 34 , wherein the partially reflective surface includes:
   a substrate; and        a coating on the substrate.     
     
     
       38. The etalon of  claim 37 , wherein the coating on the substrate is graded. 
     
     
       39. The etalon of  claim 37 , wherein the coating comprises a Ti/Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       40. The etalon of  claim 37 , wherein the coating comprises a Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       41. The etalon of  claim 34 , wherein the etalon is based on an etalon design having a plurality of taps, each tap having a selected transmission factor value, each tap except one having a selected reflection factor value, and each tap having a selected reflection factor value having a selected transport delay value. 
     
     
       42. An etalon, comprising:
   means for partially reflecting a base pulse; and        means for fully reflecting the partially reflected base pulse spaced apart from the partially reflecting means in operative relationship thereto, the fully reflecting means being spaced apart from the partially reflective means a distance being a function of predetermined proportionality between the width of an output pulse and the width of the base pulse.     
     
     
       43. The etalon of  claim 42 , wherein the plurality reflective means is graded. 
     
     
       44. The etalon of  claim 42 , wherein the predetermined proportionality is equal to an integer multiple of the width of the base pulse. 
     
     
       45. The etalon of  claim 42 , wherein the partially reflective means includes:
   a substrate; and        a coating on the substrate.     
     
     
       46. The etalon of  claim 42 , wherein the etalon is based on an etalon design having a plurality of taps, each tap having a selected transmission factor, each tap except one having a selected reflection factor, and each tap having a selected reflection factor having a selected transport delay, the selected transport delay being proportional to the width of a base pulse. 
     
     
       47. An optical pulse stretcher, comprising:
   a partially reflective surface against which a base pulse may impinge;        a fully reflective surface spaced apart from the partially reflective surface a distance that is a function of predetermined proportionality between the width of an output pulse and the width of the base pulse and in operative relationship to the partially reflective surface; an optical collector capable of collecting a plurality of base pulse components propagating through the partially reflective surface; and        a combiner capable of combining the collected base pulse components and outputting a stretched pulse.     
     
     
       48. The optical pulse stretcher of  claim 47 , wherein the partially reflective surface is graded. 
     
     
       49. The optical pulse stretcher of  claim 47 , wherein the predetermined proportionality is equal to an integer multiple of the width of the base pulse. 
     
     
       50. The optical pulse stretcher of  claim 47 , wherein the partially reflective surface includes:
   a substrate; and        a coating on the substrate.     
     
     
       51. The optical pulse stretcher of  claim 50 , wherein the coating on the substrate is graded. 
     
     
       52. The optical pulse stretcher of  claim 50 , wherein the coating comprises a Ti/Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       53. The optical pulse stretcher of  claim 50 , wherein the coating comprises a Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       54. The optical pulse stretcher of  claim 47 , wherein the optical collector comprises a lens. 
     
     
       55. The optical pulse stretcher of  claim 47 , wherein the optical pulse stretcher is based on an optical pulse stretcher design having a plurality of taps, each tap having a selected transmission factor value, each tap except one having a selected reflection factor value, and each tap having a selected reflection factor value having a selected transport delay value. 
     
     
       56. An optical system, comprising:
   an optical receiver capable of receiving an optical signal;        an optical pulse stretcher, including:      a partially reflective surface against which a base pulse may impinge;        a fully reflective surface spaced apart from the partially reflective surface a distance that is a function of predetermined proportionality between the width of an output pulse and the width of the base pulse and in operative relationship to the partially reflective surface;        an optical collector capable of collecting a plurality of base pulse components propagating through the partially reflective surface; and        a combiner capable of combining the collected base pulse components and outputting a stretched pulse; and          a detector capable of processing the stretched pulse.     
     
     
       57. The optical system of  claim 56 , wherein the partially reflective surface is graded. 
     
     
       58. The optical system of  claim 56 , wherein the predetermined proportionality is equal to an integer multiple of the width of the base pulse. 
     
     
       59. The optical system of  claim 56 , wherein the partially reflective surface includes:
   a substrate; and        a coating on the substrate.     
     
     
       60. The optical system of  claim 59 , wherein the coating on the substrate is graded. 
     
     
       61. The optical system of  claim 59 , wherein the coating comprises a Ti/Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       62. The optical system of  claim 59 , wherein the coating comprises a Au coating and the substrate comprises an optical glass or a sapphire. 
     
     
       63. The optical system of  claim 56 , wherein the optical collector comprises a lens. 
     
     
       64. The optical system of  claim 56 , wherein the optical pulse stretcher is based on an etalon design having a plurality of taps, each tap having a selected transmission factor value, each tap except one having a selected reflection factor value, and each tap having a selected reflection factor value having a selected transport delay value. 
     
     
       65. A method for stretching an optical pulse, comprising:
   introducing a base pulse into an etalon, the etalon including a fully reflective surface spaced apart from a partially reflective surface a distance that is a function of a predetermined proportionality between the width of an output pulse and the width of the base pulse; and        combining a plurality of portions of the base pulse propagating from the etalon to generate a stretched pulse whose width is proportional to the width of the base pulse.     
     
     
       66. The method of  claim 65 , wherein collecting the plurality of portions includes focusing the portions on a combiner. 
     
     
       67. The method of  claim 65 , wherein combining the portions to generate a stretched pulse includes combining the portions to generate a shaped, stretched pulse. 
     
     
       68. The method of  claim 65 , wherein combining the collected portions to generate the shaped, stretched pulse includes combining the collected portions to generate a pulse having a shape selected from the group consisting of a staircase, a square, and a sinusoid. 
     
     
       69. The method of  claim 65 , further comprising grading the partially reflective surface. 
     
     
       70. The method of  claim 69 , wherein grading the partially reflective surface includes varying the thickness or density of a coating on a substrate. 
     
     
       71. The method of  claim 65 , wherein the partially reflective surface is a graded, partially reflective surface,
   wherein collecting a plurality of portions of the base pulse propagating from the etalon includes collecting a plurality of portions of the base pulse propagating through the graded, partially reflective surface, and        wherein combining the plurality of portions includes generating a shaped, stretched pulse.     
     
     
       72. The method of  claim 65 , wherein collecting the plurality of portions includes focusing the portions on a combiner. 
     
     
       73. The method of  claim 65 , wherein combining the collected portions to generate the shaped, stretched pulse includes combining the collected portion to generate a pulse having a shape selected from the group of a staircase, a square and a sinusoid. 
     
     
       74. The method of  claim 65 , further comprising grading the partially reflective surface. 
     
     
       75. The method according to  claim 74 , wherein grading the partially reflective surface includes varying the thickness or density of a coating on a substrate. 
     
     
       76. The method of  claim 65 , wherein the etalon is based on an etalon design having a plurality of taps,
   the method further comprising modeling the etalon comprising:        assigning a selected transmission factor value to each one of a plurality of taps;        assigning a selected reflection factor value to each one of the taps, excepting only one tap; and        assigning a selected transport delay for each tap to which a reflection factor value was assigned.