High-speed electro-optic modulator
First Claim
1. A light modulator comprising:
- an input optical fiber;
a polarization separator that separates incident light from the input optical fiber, said incident light having a wavelength in the range of 1200 nm to 1600 nm, into two polarization components along separate pats within the modulator, said paths defining a separation plane;
a crystalline ceramic electro-optic phase retarder having electrodes that provide an electric field across the paths, said electric field having a voltage of less than 500 volts across said phase retarder to provide relative phase retardation with respect to the two polarization components from the separator;
a polarization recombinor that combines the polarization components from the retarder to form a modulated optical signal; and
an output fiber optically coupled to the recombinor and that receives the modulated optical signal.
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Accused Products
Abstract
An optical modulator is provided to control the intensity of a transmitted or reflected light. In a transmission mode, a separator splits arbitrarily polarized light into two polarization rays and one is made to travel a separate path from the other. A recombiner causes the two rays to recombine at an output unless an electro-optic phase retarder changes the polarization of the two rays, in which case, both of them miss the output by an amount which is a function of the voltage on the retarder. A normally-off version with low polarization mode dispersion is obtained by changing the orientation of the recombiner. A normally-on version with low polarization mode dispersion is obtained with a passive polarization direction rotator. Similar results can be obtained in a reflection mode where the input and output are on the same side of the modulator. Versions using a GRIN lens are particularly suited to modulation of light out of and back into fiber-optic cables. The device can be operated as a variable optical attenuator, an optical switch, or a high speed modulator and is insensitive to polarization of the input light. A preferred material for the phase retarder is a hot-pressed ceramic lead lanthanum zirconate titanate composition.
45 Citations
38 Claims
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1. A light modulator comprising:
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an input optical fiber; a polarization separator that separates incident light from the input optical fiber, said incident light having a wavelength in the range of 1200 nm to 1600 nm, into two polarization components along separate pats within the modulator, said paths defining a separation plane; a crystalline ceramic electro-optic phase retarder having electrodes that provide an electric field across the paths, said electric field having a voltage of less than 500 volts across said phase retarder to provide relative phase retardation with respect to the two polarization components from the separator; a polarization recombinor that combines the polarization components from the retarder to form a modulated optical signal; and an output fiber optically coupled to the recombinor and that receives the modulated optical signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A light intensity modulator comprising:
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a polarization separator receiving light at an input area and that separates the light into two polarization components that transit the modulator along separate paths, said paths defining a separation plane; a polarization recombiner from said polarization separator and receiving the light at the output area with an orientation with respect to said polarization separator selected to produce either a normally-on type modulator or a normally-off type modulator; a solid-state electro-optic phase retarder having electrodes arranged to provide a transverse electric field that produces relative phase retardation with respect to components of each of the two polarization components produced by the polarization separator and having substantially equal effect on the two components such that the components are interchanged after a transit in a forward and reverse direction; and a reflector oriented to direct light transmitting said separator and said retarder in the forward direction back through said retarder and said recombiner in the reverse direction to the output area. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method of modulating an optical signal comprising:
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coupling light having a wavelength in the range of 1200 nm to 1600 nm from an input optical fiber to a polarization separator to separate the light into a plurality of polarization components; applying an electric field in a direction across an optical path of the polarization components within a crystalline ceramic electro-optic phase retarder to provide relative phase retardation between the components, the electric field having a voltage of less than 500 volts across the phase retarder; combining the polarization components to form a modulated output signal. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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Specification