A laser system and method. In one example, the laser system includes an optical pulse stretcher configured to stretch pulse durations of an input train of input pulses to produce a train of stretched laser pulses, a pulse replicator module configured to increase a pulse repetition rate of the train of stretched laser pulses to produce a modified pulse train of laser light, a fiber power amplifier configured to amplify the modified pulse train to produce amplified laser pulses, and a pulse compressor that temporally compresses the amplified laser pulses to produce amplified and compressed laser pulses. The system may further include a nonlinear frequency conversion stage comprising at least one nonlinear crystal.

An optical communication system is disclosed. The optical communication system may include a first fiber pump laser system having a first single mode (SM) fiber output configured to output a first pump laser radiation, a second fiber pump laser system having a second SM fiber output configured to output a second pump laser radiation, at least one combiner-splitter element configured to combine the first pump laser radiation and the second pump laser radiation and to transmit N portions of pump laser radiation, and N doped fiber amplifiers, where N is at least four, each doped fiber amplifier configured to receive one portion of the N portions of pump laser radiation and an input optical signal to be amplified, amplify the input optical signal into an amplified optical signal, and to transmit the amplified optical signal.

In a draw tower for producing a length of optical fiber, a preform feed accepts a preform into the draw tower and a furnace downstream of the preform feed heats the preform. Fiber shaping hardware downstream of the thermal furnace is controlled by fiber shaping control electronics to produce along the fiber at least one low-absorption fiber section having a first cross-sectional geometry of the inner cladding layer corresponding to a first level of absorption of input pump light from the inner cladding layer to the core and at least one high-absorption fiber section having a second cross-sectional geometry of the inner cladding layer corresponding to a second level of absorption of input pump light from the inner cladding layer to the core that is greater than the first level of absorption. A tractor downstream of shaping hardware pulls the preform through the furnace and shaping hardware.

An optical fiber may comprise a core doped with one or more active ions to guide signal light from an input end of the optical fiber to an output end of the optical fiber, a cladding surrounding the core to guide pump light from the input end of the optical fiber to the output end of the optical fiber, and one or more inserts formed in the cladding surrounding the core. The core may have a geometry (e.g., a cross-sectional size, a helical pitch, and/or the like) that varies along a longitudinal length of the optical fiber, which may cause an absorption of the pump light to be modulated along the longitudinal length of the optical fiber.

An optical module comprising a first optical fiber corresponding to an incidence side for laser light a second optical fiber corresponding to an emission side for the laser light; and a connection protecting portion that is provided and located so as to cover a connection site for optically connecting the first optical fiber and the second optical fiber, wherein the second optical fiber has a larger core diameter than the first optical fiber, the connection site is a site where a core portion of the first optical fiber and a core portion of the second optical fiber are connected to each other in a discontinuous shape, and the connection protecting portion is formed of a thermally conductive protective material and/or a photorefractive protective material includes refractive index that is equal to or higher than that of a clad portion of the first optical fiber.

An active waveguide including active and passive rods which have respective polymeric claddings mechanically and optically coupled to one another so as to define a side pumping scheme. One or a plurality of elements are embedded in one of or both active and passive rods and have a refractive index lower than the lowest of refractive indices of the respective active and passive rods at least 1*10.sup.−3. The MM core of the active rod includes inner and outer concentric regions with a concentration of light emitters in the outer region being lower than that of the inner region at more than 50% and, a radius of the inner region being at most 92% of that of the outer region. The unabsorbed pump light at the output of the active waveguide constitutes less than 1% of the delivered pump light which in combination with the refractive index of the embedded elements and selectively doped core regions contribute to laser efficiency of at least 86%.

A wave guide may have an index profile including at least one maximum. The maximum or maxima of the index profile may correspond respectively to at least one maximum intensity of the outlet radiation with a mode of desired order. The wave guide may also have at least one doping ion configured to absorb the pump radiation. The doping ion or ions may have a concentration profile of doping ions including at least one maximum.

Stimulated Brillouin scattering (SBS) limits the maximum power in fiber lasers with narrow linewidths. SBS occurs when the power exceeds a threshold proportional to the beam area divided by the effective fiber length. The fiber lasers disclosed here operate with higher SBS power thresholds (and hence higher maximum powers at kilohertz-class linewidths) than other fiber lasers thanks to several techniques. These techniques include using high-absorption gain fibers, operating the laser with low pump absorption (e.g., ≤80%), reducing the length of un-pumped gain fiber at the fiber output, foregoing a delivery fiber at the output, foregoing a cladding light stripper at the output, using free-space dichroic mirrors to separate signal light from unabsorbed pump light, and using cascaded gain fibers with non-overlapping Stokes shifts. The upstream gain fiber has high absorption and a larger diameter for high gain, and subsequent gain fiber has a smaller diameter to improve beam quality.

An optical fiber may include a core in which core-guided light generated by one or more light sources propagates along a length of the at least one optical fiber, one or more claddings, surrounding the core, to guide cladding-guided light generated by the one or more light sources along the length of the at least one optical fiber, and a reflector structure machined into the at least one optical fiber. The reflector structure may include multiple angled facets arranged at one or more respective angles relative to an axis of the optical fiber to reflect at least a portion of the core-guided light and/or the cladding-guided light passing through the optical fiber.

An optical device includes: first optical fibers, a second optical fiber, a fiber connection portion, a fiber support portion; and a fixation resin that fixes the first optical fibers to the fiber support portion. The first optical fibers form a tapered portion including a taper initiation portion and a taper body reduced in diameter toward the fiber connection portion. The core of the second optical fiber has a core exposure area exposed outside of the first optical fibers. At least a portion of a periphery of the fixation resin is disposed closer to an optical axis of the second optical fiber than to a first reference line that is an extension of a line that passes through a closest point of the taper initiation portion to the optical axis on a plane perpendicular to the optical axis.