Echelle grating dense wavelength division multiplexer/demultiplexer

Abstract

An apparatus for use in optical communication systems to multiplex/demultiplex an optical signal consisting of an optical channel(s) of distinct wavelength(s) having a select channel spacing within a select wavelength range. The apparatus includes a plurality of optical waveguides aligned generally along the same optical axis with each having a propagating end. At least two of the optical waveguides each propagate a distinct multiplexed optical signal comprising a plurality of channels, with the multiplexed optical waveguides being arranged in a multiplexed linear array. The others of the optical waveguides are single channel waveguides arranged in a two dimensional array with linear rows perpendicular to the multiplex linear array and with each linear row corresponding to a multiplex optical waveguide. A reflective echelle grating is optically coupled to the plurality of optical waveguides along the optical axis and receives an optical signal emitted from at least one of the optical waveguides and detracts the optical signal(s) to at least one other of the optical waveguide(s).

1. A dense wavelength multiplexer/demultiplexer for use in optical communications systems using optical signals in a select near infrared wavelength range and a select channel spacing, the multiplexer/demultiplexer comprising:
 at least two multiplex optical waveguides each propagating a distinct multiplexed optical signal comprising a plurality of channels, the multiplex optical waveguides being arranged in a linear array;    a two dimensional array of single channel waveguides, the two dimensional array being arranged in linear rows perpendicular to the multiplex linear array with each linear row corresponding to a multiplex optical waveguide; and    a reflective echelle grating optically coupled to the multiplex optical waveguides and the single channel optical waveguides, the echelle grating having a groove spacing of between about 50-300 grooves per millimeter and a blaze angle of between about 51-53 degrees.    
     
     
       2. The dense wavelength multiplexer/demultiplexer of  claim 1  further comprising a collimating/focusing optic having a select focal length optically coupled between the multiplex and single channel waveguide arrays. 
     
     
       3. The dense wavelength multiplexer/demultiplexer of  claim 2  wherein the echelle grating is formed in a concave substrate having a focal length of 152.4 millimeters or less and the echelle grating comprises the collimating/focusing optic. 
     
     
       4. The dense wavelength multiplexer/demultiplexer of  claim 2  wherein the select focal length is less than 152.4 millimeters. 
     
     
       5. The dense wavelength multiplexer/demultiplexer of  claim 1  wherein the select near infrared wavelength range is between about 1520-1610 nanometers and the select channel spacing is 0.8 nanometers or less. 
     
     
       6. An apparatus for use in optical communications systems to multiplex or demultiplex an optical signal comprising optical channel(s) of distinct wavelength(s) having a select channel spacing within a select wavelength range, the apparatus comprising:
 a plurality of optical waveguides aligned generally along the same optical axis each having a propagating end, at least two of the optical waveguides each propagating a distinct multiplex optical signal comprising a plurality of channels, the multiplex optical waveguides being arranged in a multiplex linear array and the others of the optical waveguides being single channel waveguides arranged in a two dimensional array with linear rows perpendicular to the multiplex linear array with each linear row corresponding to a multiplex optical waveguide; and    a reflective echelle grating optically coupled to the plurality of optical waveguides along the optical axis receiving an optical signal emitted from at least one of the single channel or multiplex optical waveguides and diffracting the optical signal(s) into at least one other of the multiplex or single channel optical waveguides, respectively.    
     
     
       7. The apparatus of  claim 6  wherein the reflective echelle grating has a groove spacing of between about 50 and 300 grooves per millimeter and blaze angle of between about 51-53 degrees. 
     
     
       8. The apparatus of  claim 7  wherein the blaze angle provides a channel separation of at least 40 microns for a focal length of 152.4 mm or less for an order of diffraction between 4-7. 
     
     
       9. The apparatus of  claim 6  wherein the optical waveguides propagating the single channels have a core center, the core centers of adjacent single channel waveguides being spaced 125 microns or less. 
     
     
       10. The apparatus of  claim 6  wherein select wavelength range is between 1520 and 1610 nanometers, the select channel spacing is 0.8 nanometers or less. 
     
     
       11. The apparatus of  claim 6  further comprising a collimating/focusing optic having a select focal length optically coupled between the plurality of optical waveguides and the reflective echelle grating, the collimating/focusing optic being optically coupled to the plurality of optical waveguides at the select focal length. 
     
     
       12. The apparatus of  claim 6  wherein the echelle has a groove spacing of about 171.4 grooves per millimeter and a blaze angle of about 52.6 degrees. 
     
     
       13. The apparatus of  claim 6  wherein a number of single channel waveguides in each row is at least equal to the plurality of channels in the multiplexed optical signals. 
     
     
       14. The apparatus of  claim 6  wherein the reflective echelle grating is formed in a concave substrate which focuses the optical signal received from the at least one optical waveguide into the at least one other of the optical waveguides. 
     
     
       15. A method of multiplexing or demultiplexing an optical signal in an optical communications system, the optical signal comprising optical channel(s) of a 0.8 nanometer or less channel spacing and different wavelength within a wavelength range between 1520 and 1610 nanometers, the method comprising:
 a) providing a plurality of optical waveguides aligned generally along the same optical axis, at least two of the waveguides propagating a plurality of multiplexed channels, the at least two multiplex waveguides being aligned in a multiplex linear array and the others of the optical waveguides propagating single channels;    b) aligning the others of the optical waveguides in a two dimensional array having linear rows perpendicular to the multiplex linear array with each multiplex waveguide corresponding to a distinct linear row of single channel waveguides;    c) directing an optical signal from at least one of the optical waveguides to a reflective echelle grating optically coupled to the plurality of optical waveguides along the optical axis;    d) diffracting the optical signal(s) generally along the optical axis; and    e) optically coupling the optical signal(s) into the at least one other of the optical waveguides at a select focal length.    
     
     
       16. The method of  claim 15  wherein step c) the reflective echelle grating has a blaze angle of between about 51-53 degrees and a groove spacing of between about 50-300 grooves/millimeter. 
     
     
       17. A bulk optic echelle grating for use in multiplexing and demultiplexing optical signals in optical communications systems operating in a near infrared wavelength range, the grating comprising a groove spacing of between about 50-300 grooves/millimeter and a blaze angle of between about 51-53 degrees. 
     
     
       18. An apparatus to multiplex or demultiplex an optical signal comprising:
   a plurality of optical waveguides aligned generally along the same optical axis each having a propagating end; and        a reflective echelle grating having a groove spacing of between about  50  and  300  grooves per millimeter and blaze angle of between about  51 - 53  degrees optically coupled to the plurality of optical waveguides along the optical axis receiving an optical signal within a wavelength range of  1520  to  1610  nanometers emitted from at least one of the optical waveguides and diffracting the optical signal ( s )  into at least one other of the optical waveguides.     
     
     
       19. The apparatus of  claim 18  wherein the plurality of optical waveguides comprise at least one of the optical waveguides propagating a plurality of multiplexed channels and the others of the optical waveguides propagating single channels, the optical waveguides propagating the single channels being in a linear array and having a core center, the core centers of the adjacent waveguides being spaced  125  microns or less. 
     
     
       20. The apparatus of  claim 18  wherein the groove space is about  171 . 4  grooves per millimeter and the blaze angle is about  52 . 6  degrees. 
     
     
       21. A dense wavelength multiplexer/demultiplexer comprising:
   a multiplex optical waveguide propagating a plurality of optical channels of a select channel spacing multiplexed as a single optical signal within a select near infrared wavelength range;        a collimating/focusing optic optically coupled to the multiplex optical waveguide at a select focal length;        a reflective echelle grating optically coupled to the collimating/focusing optic, the echelle grating comprising a groove spacing of between about  50 - 300  grooves per millimeter and a blaze angle between about  51 - 53  degrees providing a channel separation between adjacent channels of the multiplexed optical signal at the select focal length for an order of diffraction between  4 - 7 ; and        a linear array of optical demultiplex waveguides each propagating a single channel within the near infrared wavelength range, each optical demultiplex waveguide having a center and a propagating end which is optically coupled to the collimating/focusing optic, the propagating ends being spaced the focal length from the collimating/focusing optic and the centers of adjacent demultiplex waveguides being spaced a distance corresponding to a channel separation between corresponding adjacent channels.     
     
     
       22. The dense wavelength multiplexer/demultiplexer of  claim 21  wherein the groove spacing is about  171 . 4  grooves per millimeter and the blaze angle is about  52 . 6  degrees. 
     
     
       23. The dense wavelength multiplexer/demultiplexer of  claim 21  wherein the near infrared wavelength range is between about  1520  and  1610  nanometers. 
     
     
       24. The dense wavelength multiplexer/demultiplexer of  claim 21  wherein the echelle grating has a free spectral range at least as large as the near infrared wavelength range. 
     
     
       25. The dense wavelength multiplexer/demultiplexer of  claim 21  wherein the select order of diffraction is  5  or  6 . 
     
     
       26. The dense wavelength multiplexer/demultiplexer of  claim 21  wherein the reflective echelle grating is formed in a concave substrate and the reflective echelle grating comprising the collimating focusing optic. 
     
     
       27. The dense wavelength multiplexer/demultiplexer of  claim 21  wherein the select channel spacing is  0 . 8  nanometers or less and, the channel separation is at least  40  microns. 
     
     
       28. A method of multiplexing of demultiplexing an optical signal comprising:
   a )  providing a plurality of optical waveguides aligned generally along the same optical axis, at least one of the waveguides propagating a plurality of multiplexed channels and the others of the optical waveguides propagating single channels;        b )  aligning the others of the optical waveguides in a linear array;        c )  directing an optical signal from at least one of the optical waveguides to a reflective echelle grating optically coupled to the plurality of optical waveguides along the optical axis, the grating comprising a groove spacing of between about  50 - 300  grooves/millimeter and a blaze angle providing a channel separation equal to a distance between core centers of adjacent optical waveguides in the linear array at a select focal length for a select order of diffraction between  4 - 7 ;        d )  diffracting the optical signal ( s )  generally along the optical axis; and        e )  focusing the optical signal ( s )  into the at least one other of the optical waveguides at the select focal length.     
     
     
       29. A bulk optic echelle grating for use in multiplexing and demultiplexing optical signals comprising a groove spacing of between about  50 - 300  grooves/millimeter and a blaze angle between about  51 - 53  degrees providing an angular dispersion of between  0 . 091  and  0 . 11  degrees/nm for a select order of diffraction between  4 - 7 . 
     
     
       30. The bulk optic grating of  claim 29  wherein the groove spacing is about  171 . 4  grooves per millimeter and the blaze angle is about  52 . 74  degrees. 
     
     
       31. The bulk optic grating of  claim 29  wherein the grooves are formed in a planar substrate. 
     
     
       32. The bulk optic grating of  claim 29  wherein the grooves are formed in a concave substrate having a focal length less than  152 . 4  millimeters.