Optical waveguides – With optical coupler – Particular coupling function
Patent
1997-12-11
1999-08-31
Bovernick, Rodney
Optical waveguides
With optical coupler
Particular coupling function
372 6, G02B 626, G02B 642
Patent
active
059464321
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to wavelength-selective devices usable in optical communication systems.
Optical fiber communication systems utilize wavelength-selective devices for various purposes as, for example, for routing light beams of different wavelengths to different destinations or as optical filters which allow light in a desired band of wavelengths to pass along the communication channel while removing or attenuating light at wavelengths outside of the desired band.
Wavelength-selective devices must meet demanding requirements for use in practical communications systems. The devices should be capable of separating wavelengths differing from one another by only a few nanometers. The wavelength-selective device should be environmentally stable, reliable and durable. Also, the wavelength-selective device should operate with a relatively low loss of optical power, i.e., the device should not dissipate substantial amounts of the optical power supplied to it in the desired wavelength bands.
Mach-Zehnder interferometers have been utilized as wavelength-selective devices in optical communication systems. As depicted in FIG. 1, a conventional Mach-Zehnder interferometer includes a pair of fibers F1 and F2. The fibers are coupled to one another at a first coupler C1 and a second coupler C2. The couplers are arranged to transfer light from one fiber to the other. As further explained below, the couplers may be so-called overclad tapered couplers in which narrowed, elongated portions of the fibers are closely juxtaposed with one another within a matrix or outer cladding. The couplers may be 3 dB couplers, arranged to transfer approximately one-half of the optical power supplied on one fiber to the other fiber. Fibers F1 and F2 have phase shift regions with different optical path lengths disposed between the couplers. Thus, the optical path length over the phase shift region in fiber F1 is different from the optical path length over the phase shift region in fiber F2. As used in this disclosure, the term "optical path length" is a measure of the time required for light at a given wavelength and in a given propagation mode to pass through the fiber from one end to the other. The optical path length difference has been provided by making the phase shift region of one fiber physically longer than the other, by making the two fibers F1 and F2 with different propagation constants so that the phase velocity of light within the two fibers is different, or both. The fibers can be provided with different propagation constants by making the fibers with different refractive index profiles. Where the fibers are "step-index" fibers, incorporating a core having a relatively high refractive index and a cladding with a relatively low refractive index overlying the core, the two fibers may have cores of different refractive indices, different core diameters, different cladding refractive indices or some combination of these. Regardless of the particular mechanism used to produce the optical path length difference, the single stage Mach-Zehnder filter depicted in FIG. 1 will direct light supplied through input 1 either to output 3 or to output 4 depending upon the wavelength of the light.
A typical single stage Mach-Zehnder filter has a substantially periodic transfer function relating the proportion of light directed to a particular output port to the wavelength of the light. That is, the amount of light appearing at any particular output port varies repetitively as the wavelength of the light varies. A typical transfer function for a single stage Mach-Zehnder device is illustrated in FIG. 2. It includes a series of alternating pass bands 5 and notches 6. At wavelengths within the pass bands, a substantial portion of the light supplied through port 1 is present at port 3; at wavelengths in notches 6, little or none of the light supplied through port 1 reaches port 3. The transfer function is periodic in that the pass bands and notches recur at substantially regular intervals along the wavelength
REFERENCES:
patent: 5295205 (1994-03-01), Miller et al.
patent: 5351325 (1994-09-01), Miller et al.
patent: 5400417 (1995-03-01), Allie et al.
patent: 5537671 (1996-07-01), Toyama et al.
patent: 5557442 (1996-09-01), Huber
patent: 5703975 (1997-12-01), Miller et al.
Fiber Optic Communications, Third Edition, Joseph C. Palais, "Light Sources", pp. 162-163.
Keck Donald B.
Miller William J.
Modavis Robert A.
Nolan Daniel A.
Bovernick Rodney
Corning Incorporated
Murphy Edward F.
Wise Robert E.
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