Lucent Technologies Inc.

Jinendra Kumar Ranka

Robert Scott Windeler

William Alfred Reed

Andrew John Stentz

Optical fiber communication system employing wavelength converter for broadband transmission

A properly designed MOF can simultaneously exhibit large anomalous dispersion at visible and near infrared wavelengths and support numerous transverse spatial modes that are essentially decoupled from one another, even in the presence of significant perturbations. In a MOF that includes an inner cladding region comprising at least one thin layer of air holes surrounding a core region, the key is to achieve a relatively large wave vector mismatch between the lowest order modes by appropriate design of the size of the core region and of the effective refractive index difference between the core region and the inner cladding region. In accordance with one aspect of our invention, MOFs are designed to exhibit simultaneously relatively large anomalous dispersion and essentially decoupled transverse spatial modes by making the diameter of the core region less than about 6 &mgr;m and the difference in effective refractive index between the core and cladding regions greater than about 0.1 (10%). Preferably, the cladding region contains no more than 2 layers of air holes, and the distance between the nearest edges of adjacent air holes is less than about 1 &mgr;m. MOFs with these features enable several embodiments of our invention.

Decoupling of transverse spatial modes in microstructure optical fibers

A fiber optic system comprises an optical transmitter, an optical receiver, and an optical fiber transmission path that optically couples the transmitter and the receiver to one another. The transmission path includes a first section that has negative dispersion at an operating wavelength &lgr; greater than about 1300 nm and a second section that includes a MOF. The MOF has relatively large anomalous dispersion at &lgr; and is sufficiently long to compensate the accumulated negative dispersion in the first section. In one embodiment the MOF comprises a core, a lower index cladding that includes one or more layers of air holes surrounding the core, characterized in that the diameter of the core is less than about 8 &mgr;m and the difference in effective refractive index between the core and cladding is greater than about 0.1 (10%). Preferably, the cladding contains no more than 2 layers of air holes and the distance between the nearest edges of adjacent air holes is less than about 1 &mgr;m.

Microstructure optical fibers for dispersion management in optical communication systems

Properly designed optical waveguides exhibit anomalous (positive) dispersion over a continuum of visible and near infrared wavelengths and, in one embodiment, the fiber has zero-dispersion at a visible wavelength (e.g., about 760 nm). Preferably, the zero-dispersion point occurs at a vis-nir wavelength where the normal (negative) material dispersion is relatively high and the effective refractive index difference between the core and the cladding is sufficiently large that the anomalous (positive) waveguide dispersion compensates the normal material dispersion. Illustratively, the optical waveguide is a microstructured fiber comprising a solid silica core surrounded by an inner cladding that includes a plurality of capillary air holes that allow for index-guiding within the core. The pattern formed by the cross-sections of the air holes, typically circles, may take on a variety geometric configurations, such as a closely packed hexagon or triangle. Alternatively, the cross-section of the air holes may form two mating, essentially semicircular regions on either side of a core that is supported by a pair of radial webs. As a result of the novel dispersion characteristics of the microstructured fibers combined with small effective area cores, we have demonstrated several applications of the invention that, in the prior art of standard single-mode fibers, have been possible only at wavelengths greater than about 1300 nm, including pulse compression, bright soliton propagation, fundamental mode-to-fundamental mode second harmonic generation, and broadband continuum generation in the visible.

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Brookline, MA, United States of America

Jinendra Kumar Ranka