Optical waveguides – With optical coupler – Particular coupling structure
Patent
1996-11-14
1999-03-16
Sanghavi, Hemang
Optical waveguides
With optical coupler
Particular coupling structure
G02B 628
Patent
active
058839925
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optical waveguide couplers, such as optical fiber couplers, with low wavelength sensitivity, as well as to the method of their manufacture. The invention is particularly concerned with wavelength insensitive single-mode fiber couplers.
2. Brief Description of the Prior Art
Single-mode optical fibers form the backbone of optical communication networks. Such networks need passive components, such as power dividers, to distribute optical signals to different routes. To benefit from the large bandwidth of the fiber, several wavelengths are used to send the optical signals. The star couplers, used as 1 to N power splitters, have to be wavelength insensitive for the system to benefit from the full bandwidth of the optical fibers. The two main windows of operation for telecommunications systems are around the wavelengths of 1.3 .mu.m and 1.55 .mu.m. Typically, the window widths are considered to be approximately 80 to 100 nm wide around those wavelengths. A coupler operating in those windows is called a dual window coupler, while a coupler operating from about 1.2 .mu.m to 1.6 .mu.m is called wavelength insensitive coupler.
Several solutions have been proposed. to build dual window and wavelength insensitive couplers. The smallest split number for a coupler is two. Dual window 2.times.2 all-fiber couplers are made either by using an asymmetrical coupler or a Mach-Zehnder structure. Wavelength insensitive 1.times.2 splitters can also be made with a Y junction in integrated optics. Once there is the basic 1.times.2 or 2.times.2 structure, one can make a large port number star coupler 1.times.2M (1.times.4, 1.times.8, 1.times.16, 1.times.32, etc.) by concatenation. With integrated optics, these concatenated star splitters can be made on a single chip. In fused fiber technology, dual window 1.times.3, 1.times.4, . . . , 1.times.7 can be produced.
One of the ways of making a 1.times.N coupler where N<8, is to place N-1 fibers symmetrically around a central fiber in which the power is injected at the beginning of or entry to the coupler. The simple model of placing N cores in a single cladding and calculating coupled mode equations to determine power transfer between the guides shows the possibility of fabricating 1.times.N couplers. The power launch in the central core, at the beginning of the coupler, couples to the outer cores in an equally distributed fashion because of symmetry. If the coupling parameters are right, there comes a point along the coupler where the power is equally distributed in all the cores, creating a 1.times.N coupler at a given wavelength. Since coupling is an oscillatory process, if the coupler is longer, there will be a second cross point between the power in the central and outer cores, making it possible to operate the device at two wavelengths. Using this type of geometry, Mortimore, for example in U.S. Pat. No. 5,175,779 dated Dec. 29, 1992 has shown that by controlling the fusion between the fibers, one could realize a dual window 1.times.N coupler.
One problem with this design, which is similar to that of the asymmetric 2.times.2 coupler, is that the bandwidth is limited by the oscillatory aspect of the transmission as a function of wavelength, the transmission of the central fiber having the greatest variation. A good control of the fabrication parameters is required to first make the equipartition cross points in the transmission at the correct wavelengths, by controlling the maximum exchange power and the wavelength period, and, second, to minimize the wavelength sensitivity, which according to the theory provided by Mortimore, can never be completely suppressed.
International PCT Application WO 90/08968 discloses a wide band single-mode fiber optic coupler in which at least two fibers are joined in a fused and tapered coupling region wherein the taper is asymmetrical in the longitudinal extent about the mid point of the geometric centre of the fused coupling region with the difference in the
REFERENCES:
patent: 4765816 (1988-08-01), Bjornlie et al.
patent: 5054874 (1991-10-01), Hill et al.
patent: 5058979 (1991-10-01), Yamauchi et al.
patent: 5175779 (1992-12-01), Mortimore
patent: 5644666 (1997-07-01), Campbell et al.
patent: 5671309 (1997-09-01), Abe et al.
Framatome Connectors Canada Inc.
Sanghavi Hemang
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