1988-03-21
1989-09-19
Sikes, William L.
350 9629, G02B 628
Patent
active
048675229
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to wavelength sensitive optical devices and in particular to optical devices for use in optical signal modulation or filtering.
BACKGROUND AND SUMMARY OF THE INVENTION
A permanently modulated index overlay on a waveguide such as a D-fibre will act as a wavelength filter by selectively reflecting a specific wavelength within the waveguide. Gratings scribed on the surface of a D-fibre have also been used as wavelength filters with the guided light impinging on to the grating from within the fibre and the grating sensitive wavelength being reflected.
However the devices produced have the disadvantage that they operate at fixed wavelengths and do not allow for tuning. The techniques employed also relate to optical signals already within a waveguide and do not allow for interfacing with external optical signal sources.
Dynamic diffraction gratings have been generated in a two dimensional slab waveguide of semiconducting material irradiated by two interfering light beams. Bykovskii et al describe such gratings in an article in the Soviet Journal of Quantum Electronics, Vol. 12, No. 4, Apr. 1982, entitled "Investigation of light wave diffraction in a waveguide plane by optically induced dynamic gratings". Techniques for producing dynamic transmission gratings are also described by Sincerbox in published European patent application EP 95563. The devices described both by Bykovskii et al and by Sincerbox are designed to provide angular dispersion of different input wavelengths. As such these devices may be useful, for example, for spectral analysis of a composite optical input.
However, these devices do not address or solve the problem of interfacing a spatially multiplexed optical processor with a one dimensional wavelength multiplexed waveguide.
With wavelength division multiplexed (WDM) systems or coherent systems it is usual to use external modulators each with a separate narrow bandwidth source. It is generally difficult to obtain a large number of sources of slightly different wavelength. WDM implementation may require, for example, grading of a large number of nominally identical lasers or the use of turnable lasers and multiple filters.
The present invention is directed towards providing optical devices which may be used for the desired interfacing function, for example as modulators or filters, and which do not require a large number of separate sources.
For the avoidance of doubt within the context of this specification `optical` includes not only the visible spectrum but also all wavelengths extending into the ultra violet and into the infra red and transmissible by an optical waveguide.
According to the present invention an optical device comprises a one-dimensional optical waveguide including a portion having a refractive index that varies with optical intensity and means for providing at least two coherent waves directed at said portion to form a standing wave therein, thereby to create a modulated refractive index within the waveguide portion.
The term `one-dimensional` is used here to imply that an optical signal will propagate through the waveguide substantially in one-dimension only. This is in particular contrast with slab waveguides, sometimes referred to as `planar` waveguides, where propagation in at least two dimensions is possible.
Preferably, the wavefronts of the waves are arranged to be substantially orthogonal to the longitudinal axis of the variable refractive index portion of the waveguide and the standing wave is created longitudinally in that portion, such that lines of constant refractive index run transversely across the direction of signal propagation along the waveguide.
Conveniently the coherent waves will be plane waves, at least substantially plane where the waves are indicent on the variable refractive index portion of the waveguide.
Preferably the one-dimensional waveguide will comprise an optical fibre. Alternatively, for example, the one-dimensional waveguide may comprise an integrated optical waveguide (eg using InGaAs or
REFERENCES:
patent: 4634215 (1987-01-01), Reule
patent: 4636031 (1987-01-01), Schmadel, Jr. et al.
patent: 4723829 (1988-02-01), Koonen
patent: 4746186 (1988-05-01), Nicia
patent: 4773063 (1988-09-01), Hunsperger et al.
Applied Optics, vol. 20, No. 23, 12/1/81.
Applied Physics Letters, vol. 37, No. 10, 11/15/80.
Soviet Journal of Quantum Electronics, vol. 12, No. 4, Apr. 1982, American Institute of Physics (New York, US), Yu. A. Bykovskil et al: "Investigation of Light Wave Diffraction in a Waveguide Plane by Optically Induced Dynamic Gratings"-pp. 418-421.
Applied Physics Letters, vol. 32, No. 10, May 15, 1978, American Institute of Physics (New York, US), K. O. Hill et al: "Photosensitivity in Optical Fiber Waveguides: Application to Reflection Filter Fabrication", pp. 647-648.
Applied Optics, vol. 22, No. 5, Mar. 1983, Optical Society of America (New York, US), G. T. Sincerbox et al: "Opto-Optical Light Deflection", pp. 690-697.
Applied Physics Letters, vol. 48, No. 1, Jan. 6, 1986 (New York, US), E. S. Goldburt et al: "Electro-Optical Response of a Liquid-Crystalline Fiber Coupler", pp. 10-12.
Proceedings of the 6th European Conference on Optical Communications, University of York (GB), Sep. 16-19, 1980, I. Bennion et al: "Grating Components in Birefringent Photochromic Optical Waveguides", pp. 260-263.
British Telecommunications public limited company
Sikes William L.
Ullah Akm E.
LandOfFree
Wavelength sensitive optical devices does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wavelength sensitive optical devices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wavelength sensitive optical devices will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-364173