Abstract: An optical transmission system with two counter propagating wavelength division multiplexed (WDM) optical signals carried by an optical fiber transmission line, has a first Raman pump for launching a first beam of pump energy for amplifying both WDM signals so that the first beam counter-propagates with respect to a first WDM signal The system also includes a second Raman pump for launching a second beam of pump energy for amplifying both WDM signals so that the second beam counter-propagates with respect to a second WDM signal.

Abstract: A method and apparatus for detecting if an optical module has been disconnected from a fiber span or if there has been a break in the span, and for automatically reducing the output signal level of the optical module such that the output signal level is within an acceptable safety limit. Also disclosed is a system and technique for automatically resetting a Raman pump unit once the source of an optical leak has been located and addressed.

Abstract: The present invention uses wavelength conversion to increase the bandwidth of optical communication systems. In an exemplary embodiment, a combination of wavelength conversion and amplification with a discrete optical amplifier (OA) to allow communications systems to operate in wavelength bands &lgr;′ outside the gain bandwidth of the OA. A transmitter launches signal channels (&lgr;1′, &lgr;2′, . . . , &lgr;′N) that are outside the gain bandwidth &lgr;. A wavelength conversion device upstream of the amplifier maps channels &lgr;′1, &lgr;′2, . . . &lgr;′N to corresponding wavelengths &lgr;1, &lgr;2, . . . &lgr;N within &lgr;. The OA directly amplifies the converted signals and a second wavelength conversion device downstream of the amplifier maps the amplified signals back to the original channels &lgr;′1, &lgr;′2, . . . &lgr;′N.

Abstract: 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%).

Abstract: 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;0 greater than about 1300 nm and a second section that includes a MOF. The MOF has relatively large anomalous dispersion at &lgr;0 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.

Abstract: 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;0 greater than about 1300 nm and a second section that includes a MOF. The MOF has relatively large anomalous dispersion at &lgr;0 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 II nearest edges of adjacent air holes is less than about 1 &mgr;m.

Abstract: 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%).

Abstract: 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.