Automatic polarization controller having broadband, reset-free operation

Claim 2

A polarization transformer for controlling polarization and phase of an optical signal propagating in a waveguide having an electrooptically induced birefringence at a desired wavelength of operation, the polarization transformer comprising, first means for varying the orientation of linear birefringence of the waveguide and for introducing a first predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the first predetermined phase retardation is substantially equal to π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, second means coupled to the waveguide at an output of the first means for varying the orientation of linear birefringence of the waveguide and for introducing a second predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the second predetermined phase retardation is substantially equal to π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, and third means coupled to the waveguide at an output of the second means for varying the orientation of linear birefringence of the waveguide and for introducing a third predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the third predetermined phase retardation is substantially equal to π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, wherein an angular difference ε exists between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means and 0≦ε≦2π.

Claim 3

The polarization transformer as defined in claim 1 wherein the angular difference ε is substantially equal to 0.

Claim 4

The polarization transformer as defined in claim 1 wherein the angular difference ε is substantially equal to π.

Claim 5

A polarization transformer for controlling polarization and phase of an optical signal propagating in a waveguide having an electrooptically induced birefringence at a desired wavelength of operation, the polarization transformer comprising, first means for varying the orientation of linear birefringence of the waveguide and for introducing a first predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the first predetermined phase retardation is substantially equal to π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence. second means coupled to the waveguide at an output of the first means for varying the orientation of linear birefringence of the waveguide and for introducing a second predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the second predetermined phase retardation is substantially equal to π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, third means coupled to the waveguide at an output of the second means for varying the orientation of linear birefringence of the waveguide and for introducing a third predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the third predetermined phase retardation is substantially equal to π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, and control means coupled at least to the first and third means for maintaining a substantially constant angular difference ε between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0≦ε≦2π.

Claim 6

A polarization transformer for controlling polarization and phase of an optical signal propagating in a waveguide having an electrooptically induced birefringence at a desired wavelength of operation, the polarization transformer comprising, first means for varying the orientation of linear birefringence of the waveguide and for introducing a first predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the first predetermined phase retardation is substantially equal to π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence. second means coupled to the waveguide at an output of the first means for varying the orientation of linear birefringence of the waveguide and for introducing a second predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the second predetermined phase retardation is substantially equal to π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, third means coupled to the waveguide at an output of the second means for varying the orientation of linear birefringence of the waveguide and for introducing a third predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the third predetermined phase retardation is substantially equal to π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, and control means coupled at least to the first and third means for maintaining a substantially constant angular difference ε between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0≦ε≦2π.

Claim 7

The polarization transformer as defined in claim 4 wherein the angular difference ε is substantially equal to 0.

Claim 8

The polarization transformer as defined in claim 4 wherein the angular difference ε is substantially equal to π.

Claim 9

The polarization transformer as defined in claim 4 wherein the control means includes means for dithering synchronously the orientations of linear birefringence in the first and third means during first time intervals and wherein the control means is coupled to the second means for dithering the orientation of linear birefringence therein during second time intervals, the first time intervals being substantially mutually exclusive of the second time intervals.

Claim 10

The polarization transformer as defined in claim 7 wherein the control means dithers the orientations of linear birefringence of the first, second, and third means in a periodic manner at substantially equal dither frequencies so that changes in orientation of linear birefringence for the first and third means occurs in a quadrature phase relationship with changes in orientation of linear birefringence for the second means.

Claim 11

A polarization transformer for controlling polarization and phase of an optical signal propagating along a wavepath having an controllable birefringence at a desired wavelength of operation, the polarization transformer comprising first, second, and third means connected in cascade, each means for varying the orientation of linear birefringence of the wavepath and for introducing a predetermined phase retardation between orthogonal first and second polarization states of the optical signal, the predetermined phase retardation of the first means is substantially equal to π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the first means, the predetermined phase retardation of the second means is substantially equal to π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the second means, the third predetermined phase retardation for the third means is substantially equal to π/2 radians when at least one of the polarization states is substantially equal to π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the third means, and control means coupled at least to the first and third means for maintaining a substantially constant angular difference ε between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0≦ε≦2π.

Claim 12

A polarization transformer for controlling polarization and phase of an optical signal propagating along a wavepath having an controllable birefringence at a desired wavelength of operation, the polarization transformer comprising first, second, and third means connected in cascade, each means for varying the orientation of linear birefringence of the wavepath and for introducing a predetermined phase retardation between orthogonal first and second polarization states of the optical signal, the predetermined phase retardation of the first means is substantially equal to π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the first means, the predetermined phase retardation of the second means is substantially equal to π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the second means, the third predetermined phase retardation for the third means is substantially equal to π/2 radians when at least one of the polarization states is substantially equal to π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the third means, and control means coupled at least to the first and third means for maintaining a substantially constant angular difference ε between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0≦ε≦2π.

Claim 13

The polarization transformer as defined in claim 9 wherein the first and third means each include a bulk optic quarter-wave plate element and the second means includes a bulk optic half-wave plate element.

Claim 14

The polarization transformer as defined in claim 10 wherein the control means includes means for rotating the quarter-wave plate elements of the first and third means in synchronism.

Claim 15

The polarization transformer as defined in claim 9 wherein the angular difference ε is substantially equal to 0.

Claim 16

The polarization transformer as defined in claim 9 wherein the angular difference ε is substantially equal to π.

Claim 17

The polarization transformer as defined in claim 9 wherein the control means includes means for dithering synchronously the orientations of linear birefringence in the first and third means during first time intervals and wherein the control means is coupled to the second means for dithering the orientation of linear birefringence therein during second time intervals, the first time intervals being substantially mutually exclusive of the second time intervals.

Claim 18

The polarization transformer as defined in claim 14 wherein the control means dithers the orientations of linear birefringence of the first, second, and third means in a periodic manner at substantially equal dither frequencies so that changes in orientation of linear birefringence for the first and third means occurs in a quadrature phase relationship with changes in orientation of linear birefringence for the second means.

Claim 19

A polarization transformer for controlling polarization and phase of an optical signal propagating in a waveguide having an electrooptically induced birefringence at a desired wavelength of operation, the polarization transformer comprising, first means for varying the orientation of linear birefringence of the waveguide and for introducing a first predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the first predetermined phase retardation is substantially equal to (2m+1)π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, second means coupled to the waveguide at an output of the first means for varying the orientation of linear birefringence of the waveguide and for introducing a second predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the second predetermined phase retardation is substantially equal to (2n+1)π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, and third means coupled to the waveguide at an output of the second means for varying the orientation of linear birefringence of the waveguide and for introducing a third predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the third predetermined phase retardation is substantially equal to (2p+1)π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, wherein n, m, and p are integers greater than or equal to zero and wherein an angular difference ε exists between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means and 0≦ε≦2π.

Claim 20

A polarization transformer for controlling polarization and phase of an optical signal propagating in a waveguide having an electrooptically induced birefringence at a desired wavelength of operation, the polarization transformer comprising, first means for varying the orientation of linear birefringence of the waveguide and for introducing a first predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the first predetermined phase retardation is substantially equal to (2m+1)π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, second means coupled to the waveguide at an output of the first means for varying the orientation of linear birefringence of the waveguide and for introducing a second predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the second predetermined phase retardation is substantially equal to (2n+1)π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, and third means coupled to the waveguide at an output of the second means for varying the orientation of linear birefringence of the waveguide and for introducing a third predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the third predetermined phase retardation is substantially equal to (2p+1)π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, wherein n, m, and p are integers greater than or equal to zero and wherein an angular difference ε exists between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means and 0≦ε≦2π.

Claim 21

The polarization transformer as defined in claim 16 wherein the angular difference ε is substantially equal to 0.

Claim 22

The polarization transformer as defined in claim 16 wherein the angular difference ε is substantially equal to π.

Claim 23

The polarization transformer as defined in claim 16 wherein the control means includes means for dithering synchronously the orientations of linear birefringence in the first and third means during first time intervals and wherein the control means is coupled to the second means for dithering the orientation of linear birefringence therein during second time intervals, the first time intervals being substantially mutually exclusive of the second time intervals.

Claim 24

The polarization transformer as defined in claim 19 wherein the control means dithers the orientations of linear birefringence of the first, second, and third means in a periodic manner at substantially equal dither frequencies so that changes in orientation of linear birefringence for the first and third means occurs in a quadrature phase relationship with changes in orientation of linear birefringence for the second means.

Claim 25

A polarization transformer for controlling polarization and phase of an optical signal propagating in a waveguide having an electrooptically induced birefringence at a desired wavelength of operation, the polarization transformer comprising, first means for varying the orientation of linear birefringence of the waveguide and for introducing a first predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the first predetermined phase retardation is substantially equal to (2n+1)π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, second means coupled to the waveguide at an output of the first means for varying the orientation of linear birefringence of the waveguide and for introducing a second predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the second predetermined phase retardation is substantially equal to (2n+1)π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, third means coupled to the waveguide at an output of the second means for varying the orientation of linear birefringence of the waveguide and for introducing a third predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the third predetermined phase retardation is substantially equal to (2p+1)π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, wherein m, n, and p are integers greater than or equal to zero, and control means coupled at least to the first and third means for maintaining a substantially constant angular difference ε between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0≦ε≦2π.

Claim 26

A polarization transformer for controlling polarization and phase of an optical signal propagating in a waveguide having an electrooptically induced birefringence at a desired wavelength of operation, the polarization transformer comprising, first means for varying the orientation of linear birefringence of the waveguide and for introducing a first predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the first predetermined phase retardation is substantially equal to (2n+1)π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, second means coupled to the waveguide at an output of the first means for varying the orientation of linear birefringence of the waveguide and for introducing a second predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the second predetermined phase retardation is substantially equal to (2n+1)π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, third means coupled to the waveguide at an output of the second means for varying the orientation of linear birefringence of the waveguide and for introducing a third predetermined phase retardation between orthogonal first and second polarization states of the optical signal wherein the third predetermined phase retardation is substantially equal to (2p+1)π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence, wherein m, n, and p are integers greater than or equal to zero, and control means coupled at least to the first and third means for maintaining a substantially constant angular difference ε between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0≦ε≦2π.

Claim 27

The polarization transformer as defined in claim 21 wherein the angular difference ε is substantially equal to 0.

Claim 28

The polarization transformer as defined in claim 21 wherein the angular difference ε is substantially equal to π.

Claim 29

The polarization transformer as defined in claim 21 wherein the control means includes means for dithering synchronously the orientations of linear birefringence in the first and third means during first time intervals and wherein the control means is coupled to the second means for dithering the orientation of linear birefringence therein during second time intervals, the first time intervals being substantially mutually exclusive of the second time intervals.

Claim 30

The polarization transformer as defined in claim 24 wherein the control means dithers the orientations of linear birefringence of the first, second, and third means in a periodic manner at substantially equal dither frequencies so that changes in orientation of linear birefringence for the first and third means occurs in a quadrature phase relationship with changes in orientation of linear birefringence for the second means.

Claim 31

A polarization transformer for controlling polarization and phase of an optical signal propagating along a wavepath having an controllable birefringence at a desired wavelength of operation, the polarization transformer comprising first, second, and third means connected in cascade, each means for varying the orientation of linear birefringence of the wavepath and for introducing a predetermined phase retardation between orthogonal first and second polarization states of the optical signal, the predetermined phase retardation of the first means is substantially equal to (2n+1)π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the first means, the predetermined phase retardation of the second means is substantially equal to (2m+1)π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the second means, the third predetermined phase retardation for the third means is substantially equal to (2p+1)π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the third means, wherein m, n, and p are integers greater than or equal to zero, and control means coupled at least to the first and third means for maintaining a substantially constant angular difference ε between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0≦ε≦2π.

Claim 32

A polarization transformer for controlling polarization and phase of an optical signal propagating along a wavepath having an controllable birefringence at a desired wavelength of operation, the polarization transformer comprising first, second, and third means connected in cascade, each means for varying the orientation of linear birefringence of the wavepath and for introducing a predetermined phase retardation between orthogonal first and second polarization states of the optical signal, the predetermined phase retardation of the first means is substantially equal to (2n+1)π/2 radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the first means, the predetermined phase retardation of the second means is substantially equal to (2m+1)π radians when at least one the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the second means, the third predetermined phase retardation for the third means is substantially equal to (2p+1)π/2 radians when at least one of the polarization states is substantially parallel to at least one of the principal axes of the linear birefringence for the third means, wherein m, n, and p are integers greater than or equal to zero, and control means coupled at least to the first and third means for maintaining a substantially constant angular difference ε between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0≦ε≦2π.

Claim 33

The polarization transformer as defined in claim 26 wherein the first and third means each include a bulk optic quarter-wave plate element and the second means includes a bulk optic half-wave plate element.

Claim 34

The polarization transformer as defined in claim 27 wherein the control means includes means for rotating the quarter-wave plate elements of the first and third means in synchronism.

Claim 35

The polarization transformer as defined in claim 27 wherein the angular difference ε is substantially equal to 0.

Claim 36

The polarization transformer as defined in claim 26 wherein the angular difference ε is substantially equal to π.

Claim 37

The polarization transformer as defined in claim 26 wherein the control means includes means for dithering synchronously the orientations of linear birefringence in the first and third means during first time intervals and wherein the control means is coupled to the second means for dithering the orientation of linear birefringence therein during second time intervals, the first time intervals being substantially mutually exclusive of the second time intervals.

Claim 38

The polarization transformer as defined in claim 31 wherein the control means dithers the orientations of linear birefringence of the first, second, and third means in a periodic manner at substantially equal dither frequencies so that changes in orientation of linear birefringence for the first and third means occurs in a quadrature phase relationship with changes in orientation of linear birefringence for the second means.