Method and apparatus for optical beam alignment detection and control
AssigneeGlimmerglass Networks, Inc.
InventorWilliam C. Dickson
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Abstract
Methods and apparatus are provided for detection and control of multiple-axis active alignment for a free-space-coupled single-mode fiber-optic transmission system that automatically optimizes the coupling through the system. In a specific embodiment, a measurement of coupled power is made and error signals are used to control actuation via four axes of beam steering elements to null four generally orthogonal alignment errors (combinations of two lateral errors and two angular errors) of the beam between the input and output fibers. The four alignment errors are detected using a synchronous-detection approach. A feedback control system nulls the four errors.
Claims25
In an optical beam alignment system with output of a measurement of coupled power of a beam without access to direct measurement of beam alignment, the alignment system having a beam directing controller, a method for detecting alignment errors in an alignment element for the beam comprising:
- applying a plurality of orthogonal excitation signals to the alignment element in order to move the alignment element to cause the beam directed through the alignment element to produce orthogonal variations in measured coupled power of the beam;
- detecting said variations in the measured coupled power;
- and
- correlating the measured coupled power with the orthogonal excitation signals to produce orthogonal error signals, each orthogonal error signal corresponding to an alignment parameter for the beam directing controller.
In an optical beam alignment system with output of a measurement of coupled power of a beam without access to direct measurement of beam alignment, the alignment system having a beam directing controller, a method for correcting alignment errors in an alignment element for the beam comprising:
- applying a plurality of orthogonal excitation signals to the alignment element to move the alignment element in order to cause the beam directed through the alignment element to produce orthogonal variations in measured coupled power of the beam;
- detecting said variations in the measured coupled power;
- correlating the measured coupled power with the orthogonal excitation signals to produce orthogonal error signals, each orthogonal error signal corresponding to an alignment parameter for the beam directing controller;
- applying said orthogonal error signals to servo control means;
- and
- applying output of said servo control means to said alignment element to correct alignment of said alignment element.
In an optical beam alignment system with output of a measurement of coupled power of a beam without access to direct measurement of beam alignment, an alignment error detector for the beam comprising:
- means for applying a plurality of orthogonal excitation signals to an alignment element to move the alignment element in order to cause the beam directed through the alignment element to produce orthogonal variations in measured coupled power of the beam;
- an optical power detector for detecting said variations in the measured coupled power;
- and
- means for correlating the measured coupled power with the orthogonal excitation signals to produce orthogonal error signals, each orthogonal error signal corresponding to an alignment parameter for the beam directing controller.
In an optical beam alignment system with output of a measurement of coupled power of a beam without access to direct measurement of beam alignment, an alignment error controller for the beam comprising:
- means for applying a plurality of orthogonal excitation signals to an alignment element to move the alignment element in order to cause the beam directed through the alignment element to produce orthogonal variations in measured coupled power of the beam;
- an optical power detector for detecting said variations in the measured coupled power;
- means for correlating the measured coupled power with the orthogonal excitation signals to produce orthogonal error signals, each orthogonal error signal corresponding to an alignment parameter for the beam directing controller;
- means for applying said orthogonal error signals to servo control means;
- and
- means for applying output of said servo control means to said alignment element to correct alignment of said alignment element.
Dependencies are inferred from the claim text.