There is the problem that, in a multicore optical fiber amplifier based on a clad excitation method, it is difficult to suppress the occurrence of an optical surge due to input of signal light into a core with no signal light, without the occurrence of fluctuation in the gain of a core into which signal light is inputted; therefore, a multicore optical fiber amplifier according to an exemplary aspect of the present invention includes a multicore optical fiber amplification medium including, in a clad, a plurality of cores doped with a rare earth element; signal light introduction means for introducing, into each of the plurality of cores, signal light with a wavelength included in a gain band of the multicore optical fiber amplification medium; excitation light introduction means for introducing, into the clad, excitation light for exciting the multicore optical fiber amplification medium; and control light introduction means for introducing control light into each of the plurality of cores, wherein the control light introduction means introduces the control light into a non-signal core into which the signal light is not being introduced, among the plurality of cores, only when the excitation light is being introduced.

An optical fiber amplifier comprising a first optical fiber, a second optical fiber, a third optical fiber, and an excitation light source, is disclosed. Each optical fiber has cores and a cladding surrounding the cores. The third optical fiber transmits excitation light used for signal amplification in the second optical fiber. A rare-earth element is doped to the second optical fiber that amplifies an optical signal propagating therein by the excitation light. The third optical fiber includes a reduced-diameter portion. A distance between the cores of the third optical fiber in the reduced-diameter portion is shorter than a distance between the cores in other portion of the third optical fiber, and the excitation light entering from the excitation light source to one of the cores of the third optical fiber is mode-coupled with another core of the third optical fiber to distribute the excitation light in the reduced-diameter portion.

[Object] There is provided a wideband extended pulsed light source that maintains uniqueness of an elapsed time with respect to a wavelength and does not collapse the uniqueness of an elapsed time with respect to a wavelength even when an output is increased.

[Solution] Light L1 from a pulsed laser source 11 is converted into supercontinuum light by a nonlinear element 12, is output as wideband pulsed light L2, and is caused to enter a pulse extension element 2. The pulse extension element 2 that is a multi-core fiber performs pulse extension in each of cores 211 and outputs wideband extended pulsed light L3. In the wideband extended pulsed light L3, an elapsed time and a wavelength in a pulse correspond to each other on one-to-one basis, and the wideband extended pulsed light L3 is used as light for spectrometry.

The present technology provides large mode area optical fibers engineered to have normal dispersion around 1600 nm, enabling high power Raman amplification at eye safer wavelengths. The fibers can have a main core and one or more side cores disposed relative to the main core so that modes of the main core and the one or more side cores hybridize into supermodes with modified dispersion.

The optical transmission system of the present invention includes a multi-core transmission path which includes a plurality of cores, and in which optical signals propagate through the plurality of cores, a first optical repeating means for amplifying the optical signals by individually exciting first multi-core optical amplification mediums, and a second optical repeating means for amplifying the optical signals by collectively exciting second multi-core optical amplification mediums, wherein the first optical repeating means is positioned spaced apart from the second optical repeating means by a distance determined on the basis of either a first transmissible distance due to the first optical repeating means and a second transmissible distance due to the second optical repeating means.

A method of making a multi-composition fiber is provided, which includes providing a precursor laden environment, and forming a fiber in the precursor laden environment using laser heating. The precursor laden environment includes a primary precursor material and an elemental precursor material. The formed fiber includes a primary fiber material and an elemental additive material, where the elemental additive material has too large an atom size to fit within a single crystalline domain within a crystalline structure of the fiber, and is deposited on grain boundaries between adjacent crystalline domains of the primary fiber material to present an energy barrier to atomic diffusion through the grain boundaries, and to increase creep resistance by slowing down growth between the adjacent crystalline domains of the primary fiber material.

Fiber laser amplification systems and methods are disclosed for use with a chirally coupled core (3C) optical fiber enabling the generation of a high-power output beam having a controlled stable polarization state. Vector modulation instabilities which typically induce undesirable sidebands in 3C fiber optics are greatly reduced even at high peak powers, enabling operation of the up to power levels limited mainly by stimulated Raman scattering (SRS). Polarization extinction ratios (PER) demonstrate long-term stability and minimal degradation due to changes in system temperature. Delays in reaching stable operation during start-up are also greatly reduced.

An optical amplifier uses, in a gain medium, a multicore optical fiber having a plurality of cores, and comprises: an input-light power monitor that monitors the optical power of input light to the plurality of cores of the multicore optical fiber; an output-light power monitor that monitors the optical power of medium-passed output light from the plurality of cores that has passed through the multicore optical fiber; a crosstalk monitor that monitors the amount of inter-core crosstalk among the plurality of cores; and a controller that controls the pump-light power of pump light superimposed on the input light to the plurality of cores on the basis of the monitored optical power of input light, the monitored optical power of output light, and the monitored amount of inter-core crosstalk.

According to one aspect, a few-mode amplifying fiber in a given spectral band of use is provided. The few-mode amplifying fiber comprises a cladding having a given refractive index (n.sub.0) and at least one core of refractive index and of dimensions suited to the propagation of a finite number of spatial modes in the spectral band of use of the fiber, a spatial propagation mode corresponding to a channel for transporting information. The core comprises a first solid material having a given first refractive index (n.sub.1) strictly greater than the refractive index of the cladding (n.sub.0), and, within said first material, inclusions spatially separated from one another, formed by longitudinal bars comprising a second solid material having a second refractive index (n.sub.2) strictly greater than the first refractive index (n.sub.1), at least one of said inclusions being actively doped.

An optical connection structure includes a first spatial multiplex transmission line, a second spatial multiplex transmission line, a first lens arrangement, a second lens arrangement and a first beam diameter conversion portion. The first spatial multiplex transmission line has a plurality of first transmission lines. The second spatial multiplex transmission line has a plurality of second transmission lines. The first lens arrangement is optically coupled with the first spatial multiplex transmission line. The second lens arrangement is optically coupled with the second spatial multiplex transmission line. The first beam diameter conversion portion has a first end face and a second end face and arranged between the first spatial multiplex transmission line and the first lens arrangement. The first beam diameter conversion portion is configured such that an optical diameter at the second end face is larger than an optical diameter at the first end face.