Methods and systems for generating a laser beam with different beam profile characteristics are provided. In one aspect, a method includes coupling an input laser beam into one fiber end of a multi-clad fiber, in particular a double-clad fiber and emitting an output laser beam from the other fiber end of the multi-clad fiber. To generate different beam profile characteristics of the output laser beam, the input laser beam is electively coupled either at least into the inner fiber core of the multi-clad fiber or at least into at least one outer ring core of the multi-clad fiber, or a first sub-beam of the input laser beam is coupled into at least into the inner fiber core of the multi-clad fiber and a second, different sub-beam of the input laser beam is coupled at least into the at least one outer ring core of the multi-clad fiber.

A vortex optical fiber for use in an illumination subsystem of an optical imaging system (e.g., a stimulated emission depletion (STED) microscopy system) includes an elongated optically transmissive medium having a set of regions including a core region, a trench region surrounding the core region, a ring region surrounding the trench region, and a cladding region, the set of regions having a doping profile providing a n.sub.eff for vector modes in an LP.sub.11 mode group of greater than 110.sup.4 in the visible spectral range so as to simultaneously guide stable Gaussian and orbital angular momentum (OAM) carrying modes at corresponding visible wavelengths.

An optical fiber includes a core, a depressed inner cladding surrounding the core, and an outer cladding surrounding the inner cladding, where a refractive index profile of the core includes an power distribution in which an index is 3.5 or more and 6 or less, a relative refractive index difference .sup. of the inner cladding with respect to the adding is set such that an absolute value |.sup.| thereof is 0.01% or more and 0.045% or less, a radius r1 of the core and an outer circumference radius r2 of the inner cladding are set such that a ratio r1/r2 thereof is 0.2 or more and 0.6 or less, a cable cutoff wavelength .sub.cc of 22 m is 1260 nm or less, and a mode field diameter MFD at a wavelength of 1310 nm is 8.6 m or more and 9.5 m or less.

The present disclosure provides an optical fiber. The optical fiber includes a core region. The core region is defined by a region around central longitudinal axis of the optical fiber. In addition, the core region has a first annular region. The first annular region is defined from the central longitudinal axis to a first radius r.sub.1 from the central longitudinal axis. Moreover, the core region has a second annular region. The second annular region is defined from the first radius r.sub.1 to a second radius r.sub.2. Further, the core region has a third annular region. The third annular region is defined from the second radius r.sub.2 to a third radius r.sub.3. Also, the optical fiber includes a cladding. The cladding region has a fourth radius r.sub.4.

Methods and systems for generating a laser beam with different beam profile characteristics are provided. In one aspect, a method includes coupling an input laser beam into one fiber end of a multi-clad fiber, in particular a double-clad fiber and emitting an output laser beam from the other fiber end of the multi-clad fiber. To generate different beam profile characteristics of the output laser beam, the input laser beam is electively coupled either at least into the inner fiber core of the multi-clad fiber or at least into at least one outer ring core of the multi-clad fiber, or a first sub-beam of the input laser beam is coupled into at least into the inner fiber core of the multi-clad fiber and a second, different sub-beam of the input laser beam is coupled at least into the at least one outer ring core of the multi-clad fiber.

In some embodiments, a data center optical communications system includes: a transmitter comprising a light source, wherein the light source is configured to provide light; an optical fiber operably connected to said transmitter and configured to receive light from the light source, wherein the optical fiber has a length L of 50 km or greater; a receiver configured to receive light from the optical fiber, wherein the receiver includes a detector for detecting the light, wherein the system has a power consumption of 15 W or less.

In some embodiments, an optical fiber transmission link, includes a length of dispersion compensating fiber (DCF), the dispersion compensating fiber coupled to a length of single-mode fiber (SMF) having a zero dispersion wavelength of 1300 nm to 1324 nm; wherein the optical fiber transmission link comprising the dispersion compensating fiber coupled to the single-mode fiber and operating at wavelengths between 1265 nm and 1375 nm increases maximum link lengths of the optical fiber transmission link by more than 60% as compared to the link length of the optical fiber transmission link with the single-mode fiber only; and wherein the maximum link length is calculated from the maximum allowed positive and negative accumulated dispersion at wavelengths between 1265 nm and 1375 nm.

According to some embodiments a fiber sensor comprises: an optical fiber configured for operation at a wavelength from about 300 nm to about 2000 nm, and further defined by a transmission end, another end, a fiber outer diameter and a fiber length, the fiber comprising: (a) a hybrid core comprising a single mode core portion and a multi-mode core portion; and (b) a cladding surrounding the hybrid core.

Provided is a few-mode optical fiber. The optical fiber includes: a core and a cladding enclosing the core. The cladding includes: a first inner cladding surrounding the core; a first high-refractive-index mode filter layer surrounding the first inner cladding; a second inner cladding surrounding the first high-refractive-index mode filter layer; a second high-refractive-index mode filter layer surrounding the second inner cladding; and an outer cladding surrounding the second high-refractive-index mode filter layer.

The present disclosure provides an optical fiber. The optical fiber includes a core region. The core region is defined by a region around central longitudinal axis of the optical fiber. In addition, the core region has a first annular region. The first annular region is defined from the central longitudinal axis to a first radius r.sub.1 from the central longitudinal axis. Moreover, the core region has a second annular region. The second annular region is defined from the first radius r.sub.1 to a second radius r.sub.2. Further, the core region has a third annular region. The third annular region is defined from the second radius r.sub.2 to a third radius r.sub.3. Also, the optical fiber includes a cladding. The cladding region has a fourth radius r.sub.4.