Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1998-05-20
2000-07-25
Epps, Georgia
Optical: systems and elements
Optical modulator
Light wave temporal modulation
385 2, 385 3, G02F 103, G02F 1035
Patent
active
060942916
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to an optical modulator for use in waveguides such as optical fibres or planar substrate devices.
2. Related Art
Hitherto, an optical multi-waveguide interference filter has been proposed in which a first waveguide capable of single mode transmission, is coupled to a second waveguide capable of supporting at least two transmission modes. A third waveguide supporting a single mode is used to pick up light from the second, multimode waveguide. In use, light in a single mode passes from the first waveguide into the second waveguide where it is transmitted in two modes, which interfere with one another. By an appropriate selection of the is length of the second waveguide and its optical characteristics, the interfering modes produce an amplitude peak at the entrance to the third waveguide, which shifts diametrically across the input to the third waveguide as a function of wavelength. The filter is described in detail in "An Optical Multi-waveguide Interference Filter" M. Earnshaw et al, Optics Communications 116 (1995), 339-342, May 1, 1995.
Similar two mode fibre interferometric devices have been proposed by D. Kreit et al in "Two-mode fibre interferometer/amplitude modulator" Applied Optics, December 1996, Vol 25, No 23, pp 4433-4438, which involve stretching the fibre to vary the interference between the modes, so that the optical output is a function of applied stress.
Reference is also directed to M. A. Abore et al "Analysis of the insertion loss and extinction ratio of two-mode fibre interferometric devices" which discloses an optically pumped bi-moded fibre in which an input optical signal switches the interference between the modes in the fibre, so as to switch the output.
It has also been proposed to sense temperature by sensing mode-mode interference in a birefringent optical fibre, as described by W. Eickoff, Optics Letters, Vol. 6, No. Apr. 4, 1981 pp 204-206.
Electro-optic modulation of a silica-based fibre has been proposed by T. Fujiwara et al, Electronics Letters, Mar. 30, 1995, Vol. 31 No. 7, pp 573-575. In order to pole the fibre and provide it with an electro-optic coefficient, a voltage was applied to wires inserted into the fibre whilst irradiating it with ultraviolet radiation. Thereafter, the application of a voltage to the wires produced a phase shift for optical radiation transmitted through the fibre.
SUMMARY OF THE INVENTION
The present invention provides a new approach for producing modulation in an optical waveguide.
In accordance with the invention there is provided an optical modulator comprising: a waveguide for supporting first and second different optical transmission modes, an output for optical radiation from the waveguide, the intensity of the radiation that passes through the output being a function of the relative phases of the first and second modes at the output, and modulating means operable to apply an electric field to the waveguide so as to change the phase difference between the modes at the output and thereby control the intensity of optical radiation that passes through the output.
The waveguide may be formed of electrically poled material, which may be thermally poled.
The modulator according to the invention may be formed in an optical fibre, such as silica-based fibre, which has been thermally poled. The fibre may include electrode means running along the length thereof to permit a modulating voltage to be applied.
A modulator according to the invention may also be embodied in a planar waveguide device.
The invention also includes a method of modulating optical radiation travelling in a waveguide that has an output for optical radiation therefrom, and that supports first and second different optical transmission modes such that the intensity of the radiation that passes through the output is a function of the relative phases of the first and second modes at the output, the method comprising applying an external electric field to the waveguide so as to change the phase difference b
REFERENCES:
patent: 4791388 (1988-12-01), Sanford et al.
patent: 5082349 (1992-01-01), Cordova-Plaza et al.
patent: 5239407 (1993-08-01), Brueck et al.
patent: 5247601 (1993-09-01), Myers et al.
patent: 5617499 (1997-04-01), Brueck et al.
patent: 5867615 (1999-02-01), Shi
Arbore et al, "Analysis of the Insertion Loss and Extinction Ratio of Two-Mode Fiber Interferometric Devices", Optical Fiber Technology 2, 400-407 (1996), Article No. 0046.
Fujiwara et al, "UV-Excited Poling and Electrically Tunable Bragg Gratings in a Germanosilicate Fiber", Optical Fiber Communication . . . Summaries OFC '95, San Diego, Feb. 26-Mar. 3, 1995, Institute of Electrical and Electronics engineers, The University of Sydney, pp. 347-350.
Kreit et al, "Two-Mode Fiber Interferometer/Amplitude Modulator" Applied Optics, Dec. 1, 1986, USA, vol. 25, No. 23, ISSN 0003-6935, pp. 4433-4438, XP002039365.
Zhao et al, "Zero-Gap Directional Coupler Switch Integrated into a Silicon-on Insulator for 1.3-.mu. m Operation", Optics Letters, Oct. 15, 1996, Opt. Soc. America, USA, vol. 21, No. 20, ISSN 0146-9592, pp. 1664-1666, XP000630400.
British Telecommunications public limited company
Epps Georgia
Spector David N.
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