Radiant energy – Ionic separation or analysis – Static field-type ion path-bending selecting means
Patent
1989-09-11
1991-01-08
Lee, John D.
Radiant energy
Ionic separation or analysis
Static field-type ion path-bending selecting means
25022724, G02B 626
Patent
active
049830074
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to optical coupling devices. It finds particular application in maintenance, or fault finding, in optical communications systems,
BACKGROUND AND SUMMARY OF THE INVENTION
It is sometimes advantageous to couple optical radiation into or out of a waveguide at a point other than at an end. For instance, which jointing optical fibres it is known to align the fibre ends to be jointed by feeding light from one fibre end into the other and maneuvering them relative to one another to maximise coupling between the fibre ends. To do so, a bend is produced in the fibres to each side of the jointing region and the light is injected at the bend in one fibre and monitored by picking it off at the bend in the other fibre.
Although this technique for injecting and picking off light has the advantage that little preparation of the fibre has to be done, that is, it can be carried out for instance through a protective polymer coating carried by a fibre, there are circumstances in which it is unsuitable. The technique injects a relatively high power level of light and picks off as high a proportion of the light injected as possible. There are applications in which it is still advantageous to pick off radiation at a point along a fibre other than at an end, but in which it is preferable that only low power levels are picked off. For instance, in an optical fibre communications system, one may wish to detect a malfunctioning fibre amongst working fibres. If one were to test for the malfunctioning fibre by picking off high power levels from random fibres, the transmission of one or more working fibres is likely to be interfered with.
Optical couplers are known which can be used to couple an adjustable power level of light into or from an optical fibre but they rely on careful preparation of the fibre. For instance, in one type, the core glass of the fibre has to be brought close to the fibre surface by mounting the fibre in a curved position and polishing away the cladding glass on the outside of the curve until fibre core glass is almost exposed. Light is then coupled into and out of the exposed core of the fibre by controlling the relative position of a second fibre which has been polished in the same manner.
Optical couplers of this type suffer from the disadvantages that they are time-consuming and expensive to produce. A monomode fibre typically has an outer diameter of 125 .mu.m and a core diameter of only 9 .mu.m. Hence it is difficult to control the polishing steps with sufficient accuracy. The couplers are also limited in that they can only be used at predetermined fixed positions along a prepared fibre. Further, the fact that the arrangement tends to be vulnerable and unsuitable for use in the field.
It is an object of the present invention to provide an optical coupling device which can conveniently be used to test optical fibres in use in an optical communications system.
According to the present invention there is provided an optical coupling device, for coupling low power levels of optical radiation out of an optical waveguide having a refractive index of n.sub.1 at or near its surface, comprising a pick-up element having a refractive index n.sub.3 and providing a curved optical waveguiding path therein, and clamping means for clamping the optical waveguide into a curved position which at least substantially conforms to the inner side of the curved path, the refractive indices of the pick-up element and the surface of the optical waveguide, n.sub.3 and n.sub.1, and the radius of curvature, R, in mm of the inner surface of the curved path portion of the pick-up element being chosen such that n.sub.3 >n.sub.1 (1-0.125/R): such that optical radiation is leaked from the optical waveguide in use, and coupled into the curved path.
It has been found that a relatively simple coupling device can be designed according to embodiments of the present invention which will pick up sufficient radiation from for instance an optical fibre to check whether the fibre is functi
REFERENCES:
patent: 3910677 (1975-06-01), Becker et al.
patent: 3931518 (1976-09-01), Miller
patent: 3936631 (1976-10-01), Muska
patent: 4436365 (1984-07-01), Hodgins et al.
patent: 4679907 (1987-04-01), Campbell et al.
patent: 4881791 (1989-11-01), Mallison et al.
patent: 4889403 (1989-12-01), Zucker et al.
patent: 4914665 (1990-04-01), Sorin
Masayuki Fujise et al.--"Core Alignments by a Simple Local Monitoring Method"--Aug. 1, 1984/vol. 23, No. 15/Applied Optics, pp. 2643-2648.
Review of the Electrical Communications Laboratories, vol. 31, No. 3, 1983, "Measurement Technique for Single-Mode . . . ", Nakazawa et al., pp. 290-298.
Electronics Letters, Nov. 11, 1982, vol. 18, No. 23, "Fibre-Optic Variable Delay Lines", Bowers et al., pp. 999-1000.
Applied Optics, vol. 15, No. 10, Oct. 1976, "Single Mode Optical Fiber Pickoff Coupler", Hsu et al., pp. 2310-2312.
Electronics and Communications in Japan, vol. 66-B, No. 11, 1983, "Design and Charac. of Optical Power Meter, etc.", Maekawa et al., pp. 94-100.
IEE Proceedings, vol. 132, Pt. J, No. 5, Oct. 1985, "Low-Loss Single-Mode Optical Couplers", Georgiou et al., pp. 297-302.
J. Opt. Soc. Am. A., vol. 2, No. 5, May 1985, "Evanescent-Field Coupling Between Monomode Fiber, etc.", Lamouroux et al., pp. 759-964.
Davison Mark
Hornung Stephen
James Simon M
Reeve Michael H.
British Telecommunications
Heartney Phan T.
Lee John D.
LandOfFree
Optical coupling device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical coupling device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical coupling device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-930338