Automatic polarization controller having broadband, reset-free operation

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 .pi./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 .pi. 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 .pi./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 .epsilon. between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0.ltoreq..epsilon..ltoreq.2.pi..

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 .pi./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 .pi. 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 .pi./2 radians when at least one of the polarization states is substantially equal to .pi./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 .epsilon. between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0.ltoreq..epsilon..ltoreq.2.pi..

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).pi./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).pi. 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).pi./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 .epsilon. exists between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means and 0.ltoreq..epsilon..ltoreq.2.pi..

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).pi./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).pi. 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).pi./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 .epsilon. between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0.ltoreq..epsilon..ltoreq.2.pi..

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).pi./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).pi. 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).pi./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 .epsilon. between the orientation of linear birefringence for the first means and the orientation of linear birefringence for the third means wherein 0.ltoreq..epsilon..ltoreq.2.pi..