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. Each of the one or more inserts 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 fiber can include a core comprising silica co-doped with nitrogen and chlorine and an outer cladding surrounding the core. In some aspects, the core can be characterized by an annealing temperature of less than or equal to about 1150° C. and/or the core can include a relative refractive index Δ.sub.core in a range of from about 0.15% to about 0.45%.

An optical fiber includes: a core; and a cladding layer disposed on an outer circumference of the core. A Cl concentration in the cladding layer is 0.029 wt % to 0.098 wt %. In the optical fiber, Δ2−Δ1≤0 dB/km is satisfied at a wavelength of 430 nm where Δ1 is a value of transmission loss before exposure of the optical fiber to hydrogen and Δ2 is a value of transmission loss after the exposure.

One described aspect is an optical fiber comprising: a fiber core that extends along a fiber axis, is configured to transmit a laser energy along the fiber axis, and terminates at a distal end; a first cladding that extends along the fiber axis, is adjacent to the fiber core, and terminates at a distal end; a coating that extends along the fiber axis and terminates at a distal end, wherein the coating is a gold coating; a second cladding that surrounds a portion of the gold coating along the fiber axis, and terminates at a distal end; an outer jacket that extends along the fiber axis and terminates at a distal end; and a fiber tip. Associated laser systems are also disclosed.

The present invention relates to an optical fiber having a core extending parallelly along a central axis of the optical fiber, an inner cladding surrounding the core and an outer cladding surrounding the inner cladding. In particular, the core is up-doped with first and second up-dopants and the inner cladding is up-doped with the second up-dopant. Moreover, the outer cladding is un-doped. Further, the optical fiber has an attenuation of less than 0.2 at a wavelength of 1625 nanometres (nm), the attenuation of less than 0.18 at a wavelength of 1550 nm, or the attenuation of less than 0.32 at a wavelength of 1310 nm and a cable cutoff in a range of 1186 nanometres (nm) to 1194 nm.

A low-crosstalk large-capacity few-mode optical fiber includes an optical fiber cladding. Few-mode units are arranged in the optical fiber cladding, each few-mode unit sequentially includes a few-mode fiber core, an inner cladding and a trench from inside to outside, and a high-refractive-index ring is arranged in the few-mode fiber core. The few-mode units include first few-mode subunits, second few-mode subunits and third few-mode subunits, where the first few-mode subunits, the second few-mode subunits and the third few-mode subunits are arranged at intervals. The first few-mode subunit includes a first few-mode fiber core, the second few-mode subunit includes a second few-mode fiber core, and the third few-mode subunit includes a third few-mode fiber core, the radii and refractive indexes of the first few-mode fiber cores, the second few-mode fiber cores and the third few-mode fiber cores being different, respectively.

A low-dispersion single-mode fiber includes a core and claddings covering the core. The core layer has a radius in a range of 3-5 μm and a relative refractive index difference in a range of 0.15% to 0.45%. The claddings comprise a first depressed cladding, a raised cladding, a second depressed cladding, and an outer cladding arranged sequentially from inside to outside. The first depressed cladding has a unilateral width in a range of 2-7 μm and a relative refractive index difference in a range of −0.4% to 0.03%. The raised cladding has a unilateral width in a range of 2-7 μm and a relative refractive index difference in a range of 0.05% to 0.20%. The second depressed cladding has a unilateral width in a range of 0-8 μm and a relative refractive index difference in a range of 0% to −0.2%. The outer cladding is formed of pure silicon dioxide glass.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein Th is at least about 50° C., preferably 50° C.<Th.sub.h<250° C.

Certain aspects of the present disclosure generally relate to an optical reference element having a wavelength spectrum comprising a plurality of wavelength functions having wavelength peaks spaced over a range of wavelengths, wherein adjacent wavelength functions are due to two orthogonal birefringence axes in the optical reference element. Aspects of the present disclosure may eliminate the drift issues associated with residual polarization and polarization dependent loss (PDL) with respect to grating-based sensor and reference element measurements.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50° C., preferably 50° C.<T.sub.h<250° C.