Fiber optic inter-mode coupling single side band frequency shifter
First Claim
1. An apparatus for coupling light between optical propagation modes in an optical fiber, comprising:
- an optical fiber having a first optical propagation mode and a second optical propagation mode for light propagating therein; and
a generator, connected to said fiber such that said generator produces a flexural wave which propagates in said optical fiber, the energy of said flexural wave confined to said optical fiber, said flexural wave having a frequency, a propagation velocity and a wavelength, said wavelength of said flexural wave being a function of said frequency and said propagation velocity, and being selected to cause coupling of light from one of said first an secon moes to the other of said first an secon moes.
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Accused Products
Abstract
An optical fiber is subjected to a series of traveling flexural waves propagating along a length of the fiber. At least a portion of an optical signal propagating within the optical fiber in a first propagation mode is coupled to a second propagation mode. The optical signal in the second propagation mode has a frequency which is equal to either the sum of or the difference between the frequency of the optical signal in the first propagation mode and the frequency of the traveling flexural waves. The frequency of the optical signal in the second propagation mode is shifted upward or downward from the frequency of the optical signal in the first propagation mode as determined by the direction of propagation of the first optical signal with respect to the direction of propagation of the traveling flexural waves, and as also determined by whether the phase propagation velocity of the optical signal in the first propagation mode is greater than or less than the propagation velocity of the optical signal in the second propagation mode.
66 Citations
61 Claims
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1. An apparatus for coupling light between optical propagation modes in an optical fiber, comprising:
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an optical fiber having a first optical propagation mode and a second optical propagation mode for light propagating therein; and a generator, connected to said fiber such that said generator produces a flexural wave which propagates in said optical fiber, the energy of said flexural wave confined to said optical fiber, said flexural wave having a frequency, a propagation velocity and a wavelength, said wavelength of said flexural wave being a function of said frequency and said propagation velocity, and being selected to cause coupling of light from one of said first an secon moes to the other of said first an secon moes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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42. An apparatus for coupling light, comprising:
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an optical fiber having two propagation modes; and an acoustic horn, acoustically coupled to said optical fiber and an acoustic transducer for generating surface acoustic waves on a surface of said horn, said horn configured to adiabatically transform said surface waves into longitudinal waves for exciting a flexural wave in said fiber to cause coupling of light between said modes. - View Dependent Claims (43)
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44. An apparatus for coupling light between optical propagation modes in an optical fiber, comprising:
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an optical fiber having a first optical propagation mode and a second optical propagation mode for light propagating therein, the cross-sectional dimensions of said fiber varying along the length of said fiber; and a generator for producing an acoustic wave which propagates in said optical fiber, the energy of said traveling acoustic wave confined to said optical fiber, said acoustic wave having an acoustic frequency, said acoustic wave having a propagation velocity which varies with said varying cross-sectional imensions of said fiber and having a wavelength determined by said acoustic frequency and said propagation velocity, said wavelength of said acoustic wave selected to cause light to be coupled from one of said modes to the other of said modes. - View Dependent Claims (45, 46)
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47. An apparatus for transforming low amplitude acoustic oscillations into high amplitude acoustic oscillations, comprising:
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an acoustic medium having first and second ends, the cross-sectional area of said first end larger than the cross-sectional area of said second end; and a transducer for producing surface acoustic waves in said first end which propagate to said second end, said medium having a transition region between said first and second ends, said transition region configured to substantially adiabatically transform said surface acoustic waves into longitudinal acoustic waves as said waves propagate from said first end to said second end. - View Dependent Claims (48, 49, 50, 51, 52)
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53. A method of transforming surface acoustic waves into longitudinal acoustic waves comprising the steps of:
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inducing a surface acoustic wave in a cylinder, said cylinder having first and second end portions with a transition portion therebetween, said first end portion having a larger diameter than said second end portion; propagating said surface acoustic waves from said first end portion in the direction of said second end portion; utilizing said transition portion to substantially adiabatically transform said surface acoustic waves into longitudinal mode acoustic waves; and utilizing said transition portion to concentrate the energy of said surface acoustic waves such that the dominant acoustic wave mode at said second end of said cylinder is a longitudinal acoustic wave, having oscillations of higher amplitude than said oscillations of said surface acoustic wave induced at said first end portion. - View Dependent Claims (54)
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55. A method of coupling light between optical propagation modes in an optical fiber comprising the steps of:
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inputting light into an optical fiber having first and second optical propagation modes for light propagating therein; and propagating a flexural wave in said optical fiber, said flexural wave having a frequency, propagation velocity and wavelength, said wavelength determined by said frequency and said propagation velocity, said wavelength selected so that a portion of said light propagating in one of said first and second propagation modes is coupled to the other of said first and and second propagation modes. - View Dependent Claims (56, 57, 58, 59, 60, 61)
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Specification