An up-taper is applied by a mode adapter to increase a signal mode area prior to tapering and combining.

An optical beam delivery device includes: a first length of fiber having a first refractive index profile (RIP) to enable modification of one or more beam characteristics of an optical beam having a first beam shape; an a second length of fiber having at least one beam-shaping confinement region and situated to receive the optical beam from the first length of fiber, wherein the at least one beam shape-modifying confinement region has a quadrilateral cross-section.

A mode division multiplexing system that includes a transmitter system, a receiver system and an optical link that optically connects the transmitter and receiver systems. The optical link includes a rectangular-core optical fiber having a rectangular core with a short dimension and a long dimension. The rectangular-core optical fiber supports only a single mode in the short dimension and multiple modes in the long dimension. A method of transmitting optical signals includes converting single mode optical signals to respective multimode optical signals each having a select spatial mode as defined by the rectangular-core optical fiber. The multimode optical signals are multiplexed and transmitted from the transmitter system to the receiver system over the rectangular-core optical fiber where the multimode optical signals are demultiplexed and converted back to single mode optical signals, which are then detected by respective receivers. A rectangular-core optical fiber is also disclosed.

An optical fiber having both low macrobend loss and low microbend loss. The fiber has a central core region, a first (inner) cladding region surrounding the central core region and having an outer radius r.sub.2>16 microns and relative refractive index .sub.2, and a second (outer) cladding region surrounding the first cladding region having relative refractive index, .sub.3, wherein .sub.1>.sub.3>.sub.2. The difference between .sub.3 and .sub.2 is greater than 0.12 percent. The fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm, and r.sub.1/r.sub.2 is greater or equal to 0.24 and bend loss at 1550 nm for a 15 mm diameter mandrel of less than 0.5 dB/turn.

A bend-resistant mini optical fiber and manufacturing method thereof, first, preparing a preform via a modified chemical vapor deposition process, and manufacturing an optical fiber via drawing at a certain temperature. The advantageous of the present invention are as following, the bend-resistant mini optical fiber is primarily formed by a core layer, a platform layer, a depression layer, an outer cladding layer and a coating layer, and the relative refractive index and radius of each of the layers is reasonably controlled; and a cutoff wavelength is effectively controlled by employing an automatic temperature and tension monitoring procedure during the drawing process, such that the cutoff wavelength and a mode field diameter are maintained in a relatively stable range, and the cutoff wavelength is adjusted upward while the mode field diameter remains stable, thus facilitating a decrease of bend loss of the optical fiber.

A multi-core optical fiber includes four cores arranged in a shape along a longitudinal direction, each of the four cores having a step-index type refractive index distribution with a radius, and a cladding region having a lower refractive index than that of each core and a diameter of 125?1 ?m and provided on an outer portion of each core. An absolute value of a relative refractive index difference between each core and the cladding region is ?. The four cores are arranged so that a relationship between a minimum distance from the center of each core to an outer periphery of the cladding region, a minimum value A of spacing between the cores, and the MFD at a set wavelength satisfies a Formula C1, and the radius of each core and the relative refractive index difference ? between the core and the cladding region are set.

An MCF of the present embodiment has eight or more cores. A diameter of a common cladding is not more than 126 m. Optical characteristics of each core are as follows: a TL at a predetermined wavelength of 1310 nm is not more than 0.4 dB/km; an MFD at the predetermined wavelength is from 8.0 m to 10.1 m; a BL in a BR of not less than 5 mm or in the BR of not less than 3 mm and, less than 5 mm is not more than 0.25 dB/turn at the predetermined wavelength; 0 is from 1300 nm to 1324 nm; cc is not more than 1260 nm; an XT or XTs at the predetermined wavelength is not more than 0.001/km.

The present embodiment relates to an MCF having a low transmission loss and having a structure for reducing a transmission loss and effectively suppressing an inter-core XT. The uncoupled MCF includes alkali metal having a predetermined concentration in which each of a plurality of cores contributes to reduction in the transmission loss, and a core pitch is set so that a sum h_total of power coupling coefficients of a specific core and the remaining all cores of the plurality of cores is 2.310.sup.4/km or less.

An optical fiber (10) capable of minimizing strength deterioration includes a core (11) and a clad (12) arranged around the core (11) such that part of the core (11) is exposed. A rough surface portion is provided at least at part of an outer surface of the exposed portion (11a) of the core (11) exposed through the clad (12). The arithmetic surface roughness Ra of the rough surface portion is equal to or greater than 0.2 m. The average length Rsm of a rough curve element of the rough surface portion is equal to or greater than 17 m.

A method for forming an article includes providing a material having a first material property; forming a melt pool by exposing the material to an optical beam having at least one beam characteristic, wherein the melt pool has at least one melt pool property determinative of a second material property of the material; and modifying the at least one beam characteristic in response to a change in the melt pool property.