Optical waveguides – With optical coupler – Particular coupling function
Patent
1994-07-11
1995-09-05
Lee, John D.
Optical waveguides
With optical coupler
Particular coupling function
359308, 385 1, 385 7, 385 37, G02B 634
Patent
active
054486653
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an optical grating device, for instance for use in wavelength separation, and in particular to in a wavelength-selective filter for use in wavelength demultiplexing in optical communications.
Gratings are known in optical technology, particularly for communications, for instance in reflecting optical radiation in a selective manner. The pitch of a grating can introduce a wavelength-discriminatory element into the grating's interaction with optical radiation.
It is also known to modulate the amplitude of an optical signal by using an electro-optic overlay to modify the wavelength or wavelengths of optical radiation travelling in a waveguide. Such an arrangement is disclosed in a paper entitled "Optical Fibre Modulator Using Electro-Optic Polymer Overlay", published in Electronic Letters on 23rd May 1991, Volume 27 number 11, by M. Wilkinson et al. The electro-optic overlay comprises a polymer material applied to a polished half-coupler block. By varying the voltage applied across the electro-optic overlay, its refractive index can be changed and the wavelengths coupled out of a waveguide in the block into the overlay can be altered. This provides amplitude modulation in the waveguide in the block at selected wavelengths.
It has now been found, in making the present invention, that it is possible to produce a grating, for use in optical technology such as communications, whose pitch is not only comparable to the wavelength of optical radiation in relevant propagation media such as optical fibres, but which is also controllably variable.
Such a grating might be applied for instance as a tunable filter, for selecting a wavelength or wavelengths of optical radiation propagating in a transmission medium from a range of available wavelengths. A tunable filter of this sort might be particularly useful in co-operation with a receiver receiving an output from an optical communications fibre carrying a plurality of signals which are wavelength multiplexed. In order to demultiplex the signal so that optical radiation reaching a particular receiver as an output from that fibre should have a carrier wavelength or wavelength range dedicated to that receiver, the filter could be used to select only the wavelength required. This situation might arise for instance at a customer receiver in an optical communications network, where that customer has been allocated a wavelength slot in a wavelength division multiplexed system.
A tunable filter can offer a number of advantages in this situation. Most obviously, perhaps, a communications fibre output can be "tuned" to suit any one of a plurality of different receiver criteria, and subsequently "retuned" for use in other circumstances. Thus, effectively, the associated receiver is tuned and retuned so that it can be for instance modified from receiving a first allocated wavelength to receive a second, different allocated wavelength.
The present invention provides a wavelength-selective arrangement for interacting with optical radiation propagating in a transmission medium, the arrangement comprising a selector member made of a polar organic material which exhibits piezoelectric properties, the selector member having an interaction surface for interacting with said radiation, the selector member being provided with means for propagating surface acoustic waves along the interaction surface so as to create a grating and thereby determine its interacting properties in relation to the wavelength of said radiation, in a selectively variable manner.
Although such a grating might potentially be provided on inorganic material, such as lithium miobate, the low permittivity and elastic constants of a polar organic material can offer a potential improvement in electromechanical coupling coefficient of a factor of the order of ten times that of lithium niobate. Moreover, the surface acoustic waves propagate at significantly lower velocities, such that for a given acoustic grating pitch, drive frequencies will be proportionately less. A polar organic material i
REFERENCES:
patent: 3919669 (1975-11-01), Hartemann
patent: 4026632 (1977-05-01), Hill et al.
patent: 4761833 (1988-08-01), Epworth
patent: 5007705 (1991-04-01), Morey et al.
patent: 5166992 (1992-11-01), Cassidy et al.
Yennadhiou et al, "D-Fiber Grating Reflection Filters", Optical Fiber Communication Conference, 1990 Technical Digest Series, vol. 1, Conference Edition 22 Jan. 1990, San Francisco, US, p. 27.
Patent Abstracts of Japan, vol. 4, No. 163 (P-36) 13 Nov. 1980 & JP,A,58 111 920 (Ricoh) 29 Aug. 1980.
Patent Abstracts of Japan, vol. 15, No. 227 (C-839) 10 Jun. 1991 & JP,A,03 069599 (Furukawa) 25 Mar. 1991.
Chen et al, "Grating-Assisted Couplers", Optics Letters, vol. 16, No. 4, Feb. 1991, pp. 217-219.
Gilmour et al, "First Demonstration of Saw Propagation in Organic Crystal", Electronics Letters, 12th Mar. 1992, vol. 28, No. 6, pp. 593-594.
Harris et al, "Theory and Design of Periodic Couplers", Applied Optics, vol. 11, No. 10< Oct. 1972, pp. 2234-2241.
Syms, "Optical Directional Coupler with a Grating Overlay", Applied Optics, vol. 24, No. 5, Mar. 1985, pp. 717-726.
Wilkinson et al, "Optical Fibre Modulator Using Electro-Optic Polymer Overlay", Electronics Letters, 23rd May 1991, vol. 27, No. 11, pp. 979-981.
Yennadhiou et al, a paper given at OFC 1990 in San Francisco entitled "D-Fibre Grating Reflection Filters", 4 pages No Month.
Wagers, "Saw Transduction on Silicon Substrates with PVF.sub.2 Films", 1979 Ultrasonics Symposium, pp. 645-648 No Month.
Carome et al, "PVF.sub.2 Surface Wave Transducers", 1979 Ultrasonics Symposium, pp. 641-644 No Month.
Sen et al, "Fabrication of Low-Stress Silicon Stencil Masks for ion Beam Lithography", Journal of Vacuum Science Technology B, vol. 7, No. 6, Nov. 1989, pp. 1802-1805.
Kondo et al, "A Nonlinear Optical Organic Crystal For Waveguiding SHG Devices: (-)2-(.alpha.-Methylbenzylamino)-5-Nitropyridine (MBANP)", Japanese Journal of Applied Physics, vol. 28, No. 9, Sep. 1989, pp. 1622-1628.
Sherwood, "Molecular Nonlinear Optical Materials", Phil. Trans. Royal Society of London, Part A 1989, 13 pages.
Halfpenny et al, "Optical Materials", date unknown, 6 pages.
Bailey et al, "The Quality and Performance of the Organic Non-Linear Optical Material (-)2-(.alpha.-Methylbenzylamino)-5-Nitropyridine (MBA-NP)", Optics Communications, vol. 65, No. 3, Feb. 1988, pp. 229-232.
Bailey et al, "Organic Electro-Optic and Nonlinear Materials", International Journal of Opto-Electronics 1990, vol. 5, No. 2, pp. 89-102.
Cassidy Stephen A.
Gilmour Sandra
Kershaw Stephen V.
Pantelis Philippos
Pethrick Richard A.
British Telecommunications public limited company
Lee John D.
LandOfFree
Wavelength-selective optical device utilizing a selectively vari 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-selective optical device utilizing a selectively vari, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wavelength-selective optical device utilizing a selectively vari will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-479690