Abstract: A method for testing optical fibers includes using an optical testing instrument to measure a characteristic, such as clad non-circularity, of an optical fiber at a multiple angles of rotation of an optical fiber around its optical axis. From the measurements data points indicative of measured values of the characteristic at the respective angles of rotation are generated. A model is created of the optical fiber having the characteristic as a variable parameter, and from the model a functional relationship between an expected measured value of the characteristic and the angle of rotation and the variable parameter is generated. By varying the parameter a fit of the functional relationship to the data points is made according to one or more predetermined criteria, such as least-squares fit. The value of the characteristic can be found based on the fit. Instrumental parameters, such as fiber misalignment and cleave angle, can also be ascertained by the method.

Abstract: A fiber optic cable and connector assembly is disclosed. In one aspect, the assembly includes a cable optical fiber, an optical fiber stub and a beam expanding fiber segment optically coupled between the cable optical fiber and the optical fiber stub. The optical fiber stub has a constant mode field diameter along its length and has a larger mode field diameter than the cable optical fiber. In another aspect, a fiber optic cable and connector assembly includes a fiber optic connector mounted at the end of a fiber optic cable. The fiber optic connector includes a ferrule assembly including an expanded beam fiber segment supported within the ferrule. The expanded beam fiber segment can be constructed such that the expanded beam fiber segment is polished first and then cleaved to an exact pitch length. The expanded beam fiber segment can be fusion spliced to a single mode optical fiber at a splice location behind the ferrule.

Abstract: A GRIN fiber lens connection system particularly suited for high-power laser applications is disclosed. In one aspect, a GRIN fiber lens expanded beam system that is efficient over a wide spectral region, e.g., a range of about 200 nm, 300 nm or 400 nm, is disclosed for coupling one optical fiber (such as a single-mode fiber) to another. For example, a GRIN fiber lens expanded beam system is efficient over a range of wavelengths from about 400 nm to about 800 nm, from about 190 nm to about 390 nm, or from about 1270 nm to about 1650 nm. A method for designing such a coupling system is also disclosed. In another example, the cores of the GRIN fiber lenses are substantially devoid of germanium, and the cladding is doped with an element, such as fluorine, that lowers the refractive index of the cladding.

Abstract: A fiber optic cable and connector assembly is disclosed. In one aspect, the assembly includes a cable optical fiber, an optical fiber stub and a beam expanding fiber segment optically coupled between the cable optical fiber and the optical fiber stub. The optical fiber stub has a constant mode field diameter along its length and has a larger mode field diameter than the cable optical fiber. In another aspect, a fiber optic cable and connector assembly includes a fiber optic connector mounted at the end of a fiber optic cable. The fiber optic connector includes a ferrule assembly including an expanded beam fiber segment supported within the ferrule. The expanded beam fiber segment can be constructed such that the expanded beam fiber segment is polished first and then cleaved to an exact pitch length. The expanded beam fiber segment can be fusion spliced to a single mode optical fiber at a splice location behind the ferrule.

Abstract: A GRIN fiber lens connection system particularly suited for high-power laser applications is disclosed. In one aspect, a GRIN fiber lens expanded beam system that is efficient over a wide spectral region, e.g., a range of about 200 nm, 300 nm or 400 nm, is disclosed for coupling one optical fiber (such as a single-mode fiber) to another. For example, a GRIN fiber lens expanded beam system is efficient over a range of wavelengths from about 400 nm to about 800 nm, from about 190 nm to about 390 nm, or from about 1270 nm to about 1650 nm. A method for designing such a coupling system is also disclosed. In another example, the cores of the GRIN fiber lenses are substantially devoid of germanium, and the cladding is doped with an element, such as fluorine, that lowers the refractive index of the cladding.

Abstract: A method and system using GRIN fibers with a large core radius (such as twice that of the optical fibers which the GRIN fibers are used to interconnect) to expand incident beam are disclosed. In certain examples, the GRIN fibers expand the incident beams to near-collimation. In certain examples, the beam expansion reduces the connection's sensitivity (i.e., power attenuation) to lateral displacement between the optical fibers at the cost of increased sensitivity to angular misalignment between the fibers. With certain fiber connection hardware that provides precision angular alignment, beam expansion provides improved connection performance. In certain examples, a multi-fiber connector module (such as MPO), with MT-style ferrules, is used to interconnect multiple fiber pairs, each with GRIN fiber endings. In certain examples, the near-collimation of the incident beams allows efficient transmission between fibers without the need for physical contact between the fibers.