An optical fiber, such as in some instances a high-power, diode-pumped, dual-clad, ytterbium-doped fiber amplifier (YDFAs), having a fundamental mode and at least one higher order mode, wherein the higher order mode or modes have mode areas that are substantially larger than a mode area of the fundamental mode.

A uniform temperature profile is provided across the width of the core of a ribbon fiber laser or amplifier by the use of insulating elements at the core edges and a spatially variable gain in the fiber core. High average power ribbon fibers, enable a variety of applications such as practical laser cutting and beam combining.

A mode-locked fiber laser device is provided in the disclosure. The mode-locked fiber laser device includes a non-linear loop mirror, an optical splitter and a uni-directional loop. The uni-directional loop includes a polarization beam splitter and a Faraday rotator. The uni-directional loop is coupled to the non-linear loop mirror by the optical splitter to form a figure-8 optical path. A first output laser pulse output by the optical splitter is propagated to the polarization beam splitter. After being rotated 45 degrees by a Faraday rotator, the first output laser pulse is propagated back to the non-linear loop mirror to form a laser resonator. A second output laser pulse output by the optical splitter is propagated to the Faraday rotator to rotate the second output laser pulse 45 degrees, and the polarization beam splitter reflects the second output laser pulse to the outside of the mode-locked fiber laser device.

An apparatus includes an optical fiber configured to transport an optical signal. A cross-section of the optical fiber has a longer slow-axis dimension and a shorter fast-axis dimension. The optical fiber includes a core configured to receive and amplify the optical signal, end features optically coupled to the core at opposite ends of the core, and a cladding surrounding the core and end features. The core has a height in the slow-axis dimension and a width in the fast-axis dimension. Each end feature has a height in the slow-axis dimension and a width in the fast-axis dimension. The core has a lower bend loss than the end features. The optical fiber is configured to confine optical power of a fundamental mode in the core and allow optical power of higher-order mode(s) to leak from the core into the end features. Each end feature's height is less than the core's width.

Aspects of an optical communications network are described that include two or more optical fibers arranged to allow communication in the same or in opposite directions. The optical network includes a first optical amplifier coupled to the first optical fiber, a second optical amplifier coupled to the second optical fiber, and an optical coupler that allows excess optical power from the first optical fiber to be provided for amplification of signals traversing the second optical fiber. The disclosed systems and devices thus enable excess power from one channel to be utilized to enable amplification of signals traveling on a different channel.

In an example, a tandem pumped fiber amplifier may include a seed laser, one or more diode pumps, and a single or plural active core fiber. The single or plural active core fiber may include a first section to operate as an oscillator and a second different section to operate as a power amplifier. The one or more diode pumps may be optically coupled to the first section of the single or plural active core fiber, and the seed laser may be optically coupled to the single active core or an innermost core of the plural active core fiber.

In an example, a tandem pumped fiber amplifier may include a seed laser, one or more diode pumps, and a plural core fiber including a first core and a second core, the second core surrounding the first core. The plural core fiber may include a first section to operate as an oscillator and a second different section to operate as a power amplifier. The one or more diode pumps may be optically coupled to the first section of the plural core fiber, and the seed laser may be optically coupled to the first core.

A multi-clad optical fiber design is described in order to provide low optical loss, a high numerical aperture (NA), and high optical gain for the fundamental propagating mode, the linearly polarized (LP) 01 mode in the UV and visible portion of the optical spectrum. The optical fiber design may contain dopants in order to simultaneously increase the optical gain in the core region while avoiding additional losses during the fiber fabrication process. The optical fiber design may incorporate rare-earth dopants for efficient lasing. Additionally, the modal characteristics of the propagating modes in the optical core promote highly efficient nonlinear mixing, providing for a high beam quality (M.sup.2<1.5) output of the emitted light.

An apparatus includes an optical fiber configured to transport an optical signal. The optical fiber includes a core configured to receive and amplify the optical signal. The optical fiber also includes end features optically coupled to opposite ends of the core. The core has a lower bend loss than the end features. The optical fiber further includes a cladding surrounding the core and the end features. The optical fiber is configured to confine optical power of a fundamental mode in the core. The optical fiber is also configured to allow optical power of one or more higher-order modes to leak from the core into the end features.

Aspects of an optical communications network are described that include two or more optical fibers arranged to allow communication in the same or in opposite directions. The optical network includes a first optical amplifier coupled to the first optical fiber, a second optical amplifier coupled to the second optical fiber, and an optical coupler that allows excess optical power from the first optical fiber to be provided for amplification of signals traversing the second optical fiber. The disclosed systems and devices thus enable excess power from one channel to be utilized to enable amplification of signals traveling on a different channel.