Abstract: The present disclosure provides systems and methods for optically coupling a solid-core fiber (SCF) with a hollow-core fiber (HCF). Briefly described, one embodiment of the system comprises a graded-index (GRIN) fiber and a hollow fiber (HF) that optically couple the SCF with the HCF. The combination of the GRIN with the HF permits mode matching between the SCF and the HCF, while concurrently increasing return loss from the HCF to the SCF.

Abstract: Embodiments of the present disclosure generally relate to systems, methods, and articles of manufacture for using a fiber laser with wavelength division multiplexers (WDMs) for a variety of purposes. For example, implementations described herein may be used with high-power Raman fiber laser (RFL) systems, or the like. A laser system is provided that may include a fiber laser; a laser path comprising optical fiber; and a plurality of wavelength division multiplexers (WDMs) positioned within the laser path coupling the optical fiber; wherein at least one of the plurality of WDMs has the widest wavelength spacing and is positioned first in the laser path, thereby providing increased power stability.

Abstract: An all-fiber supercontinuum (SC) optical source utilizes a combination of a seed pulse supply of short-duration optical pulses with a highly non-linear optical medium in the form of two or more concatenated sections of highly non-linear optical fiber (HNLF) of different dispersion values and lengths. The two or more sections of HNLF are configured to include at least one section that exhibits a positive dispersion value and one section that exhibits a negative dispersion value. Non-linear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), Raman amplification, and the like, cause the seed pulses to broaden as they propagate through each section of HNLF, where the differences between the dispersion values, as well as the lengths of each fiber section, are particularly configured to create an SC output that is wide and smooth, exhibiting a stable intensity and high coherence level.

Abstract: Disclosed herein is an all-fiber, easy to use, wavelength tunable, ultrafast laser based on soliton self-frequency-shifting in an Er-doped polarization-maintaining very large mode area (PM VLMA) fiber. The ultrafast laser system may include an all polarization-maintaining (PM) fiber mode-locked seed laser with a pre-amplifier; a Raman laser including a cascaded Raman resonator and an ytterbium (Yb) fiber laser cavity; an amplifier core-pumped by the Raman laser, the amplifier including an erbium (Er) doped polarization maintaining very large mode area (PM Er VLMA) optical fiber and a passive PM VLMA fiber following the PM Er VLMA, the passive PM VLMA for supporting a spectral shift to a longer wavelength.

Abstract: An all-fiber supercontinuum (SC) optical source utilizes a combination of a seed pulse supply of short-duration optical pulses with a highly non-linear optical medium in the form of two or more concatenated sections of highly non-linear optical fiber (HNLF) of different dispersion values and lengths. The two or more sections of HNLF are configured to include at least one section that exhibits a positive dispersion value and one section that exhibits a negative dispersion value. Non-linear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), Raman amplification, and the like, cause the seed pulses to broaden as they propagate through each section of HNLF, where the differences between the dispersion values, as well as the lengths of each fiber section, are particularly configured to create an SC output that is wide and smooth, exhibiting a stable intensity and high coherence level.

Abstract: The disclosed subject matter relates to a polarization-maintaining very large mode area (PM VLMA) Erbium-doped fiber and a polarization maintaining, Er-doped VLMA amplifier.

Abstract: A self-starting, passively modelocked figure-8 fiber laser is specifically configured to self-start into a low noise mode by controlling one or more operating parameters of the laser including, but not limited to, the coupling ratio between the uni-directional fiber loop and the bi-directional mirror loop, the accumulated dispersion within the figure-8 structure, and the amount of power present in the laser cavity. A self-starting passive modelocked figure-8 laser may also be made to self-start by initially increasing the pump current above its lasing threshold. Including a band-pass filter in the uni-directional loop has been found to ensure that the laser will enter a low noise lasing mode.

Abstract: A self-starting, passively modelocked figure-8 fiber laser is specifically configured to self-start into a low noise mode by controlling one or more operating parameters of the laser including, but not limited to, the coupling ratio between the uni-directional fiber loop and the bi-directional mirror loop, the accumulated dispersion within the figure-8 structure, and the amount of power present in the laser cavity. A self-starting passive modelocked figure-8 laser may also be made to self-start by initially increasing the pump current above its lasing threshold. Including a band-pass filter in the uni-directional loop has been found to ensure that the laser will enter a low noise lasing mode.

Abstract: A length of a coating on an optical fiber is cut and stripped from an end of the fiber by supporting the fiber in confronting relation to a cutting edge on one or more blades. Each blade is positioned so that its cutting edge cuts into the coating without delaminating the coating from an underlying fiber cladding by providing the cutting edge with sufficient sharpness. The coating is sliced around the circumference of the fiber by either rotating the fiber about its axis so that the cutting edge of each blade slices the coating around a corresponding portion of the circumference of the fiber, or rotating the cutting edge of each blade about the fiber axis so that the cutting edge slices the coating around a corresponding portion of the circumference of the fiber. A cut length of the coating is then removed from the end of the fiber.

Abstract: The disclosed subject matter relates to a polarization-maintaining very large mode area (PM VLMA) Erbium-doped fiber and a polarization maintaining, Er-doped VLMA amplifier.

Abstract: In a TDM- and WDM-based FBG sensor array system, a source emits a light covering a selected wavelength range. The light is amplified and then used to generate a series of pulses that are fed into an array of sensor gratings. The propagation of a pulse through the sensor array results in a time-domain-multiplexed output, comprising a series of output pulses in which each output pulse comprises a reflection of the input pulse at a respective grating in the sensor array. Raman amplification is used to amplify both the pulse input into and the time-domain multiplexed output from the sensor array, which is then coupled into an output processing stage for receiving the sensor output and for reconstructing the wavelength output of each grating in the sensor array. The wavelength change for each grating is then used to calculate a physical parameter(s) to be measured, such as temperature and/or strain.

Abstract: A length of a coating on an optical fiber is cut and stripped from an end of the fiber by supporting the fiber in confronting relation to a cutting edge on one or more blades. Each blade is positioned so that its cutting edge cuts into the coating without delaminating the coating from an underlying fiber cladding by providing the cutting edge with sufficient sharpness. The coating is sliced around the circumference of the fiber by either rotating the fiber about its axis so that the cutting edge of each blade slices the coating around a corresponding portion of the circumference of the fiber, or rotating the cutting edge of each blade about the fiber axis so that the cutting edge slices the coating around a corresponding portion of the circumference of the fiber. A cut length of the coating is then removed from the end of the fiber.

Abstract: Described is a general strategy of bend-compensated, single-mode LMA fibers extended into a regime with higher total index contrast and where a larger gradient is used to cancel the perturbation of a tighter anticipated bend.

Abstract: A technique is described for eliminating feedback light in a high-power optical device. An optical device is provided that generates, along an optical pathway, an output light at a desired signal wavelength, wherein the generation of the output light at the signal wavelength results in the generation of a feedback light at an undesired feedback wavelength. A port is provided at a selected location along the optical fiber pathway. The port is terminated with a length of a filter fiber, wherein the filter fiber has loss characteristics at the feedback wavelength that result in the elimination of feedback light from the optical fiber pathway through the port.

Abstract: A hollow core fiber exhibiting selective birefringence is provided. The selective birefringence is induced by harnessing properties of surface modes that cause transmission loss and are otherwise considered as detrimental. Birefringence and signal loss in a preferred polarization state are engineered by fabricating an asymmetrical web structure surrounding the core. In one implementation the asymmetry in the web structure is induced by a thicker core web preferably at the core inner cladding interface, by selectively introducing defect cells at the hollow core inner cladding interface. The hollow core fiber further includes shunt cores to facilitate near single-mode transmission by additionally using intermittent bend-induced index matching to resonantly couple unwanted core modes including one or more, higher order modes to shunt modes.

Abstract: A mode converter for use with a higher-order mode (HOM)-based fiber amplifiers takes the form of axicon-based configuration that is able to convert high power (tens of mW and higher) optical signals propagating in higher-order mode form into a diffraction-limited beam without experiencing the nonlinear effects (such as self-phase modulation) that are found when using a long-period grating (LPG) to create a diffraction-limited beam by performing mode conversion. The axicon may comprise a bulk optic device, a fiber-based device, or a GRIN-based configuration (where the refractive index profile of the GRIN element is formed to create a diffraction-limited signal).

Abstract: A Raman distributed feedback (DFB) fiber laser is disclosed. It includes a pump source and a Raman gain fiber of a length smaller than 20 cm containing a distributed feedback (DFB) grating with a discrete phase structure located within no more than 10% off the center of the grating and wherein the Raman DFB fiber laser generates a laser signal with an optical spectrum, which has an optical bandwidth at half maximum optical intensity of less than 1 gigahertz (GHz) (wherein a maximum intensity frequency is different from the frequency of the pump laser). The Raman laser includes compensation for the nonlinear phase change due to Kerr effect and thermal effect resulting from absorption of the optical field, thus enhancing the conversion efficiency.

Abstract: An optical fiber includes a core region having a longitudinal axis. At least a portion of the core region has a substantially helical shape about a helical axis. The longitudinal axis may be substantially tangential to a helical bend in the optical fiber. A cladding region surrounds the core region. The core region and cladding region may be configured to support and guide the propagation of signal light in a fundamental transverse mode in the core region in the direction of the longitudinal axis. The fiber has a bend-induced gradient in its equivalent index of refraction over the portion of the core region. The fiber has a bend-induced equivalent index of refraction. At least a portion of cladding region has a graded refractive index opposite that of the bend-induced gradient. The cladding region may be configured to have a substantially flat equivalent index in response to a helical bend of the optical fiber.

Abstract: Techniques for analyzing output modal content of optical fibers that support more than one spatial mode are disclosed. These techniques are based on spatially resolving interference between co-propagating modes and constructing a spatial beat pattern between the co-propagating modes. By doing so, these techniques provide information about the modes that propagate along the optical fiber.

Abstract: In a TDM- and WDM-based FBG sensor array system, a source emits a light covering a selected wavelength range. The light is amplified and then used to generate a series of pulses that are fed into an array of sensor gratings. The propagation of a pulse through the sensor array results in a time-domain-multiplexed output, comprising a series of output pulses in which each output pulse comprises a reflection of the input pulse at a respective grating in the sensor array. Raman amplification is used to amplify both the pulse input into and the time-domain multiplexed output from the sensor array, which is then coupled into an output processing stage for receiving the sensor output and for reconstructing the wavelength output of each grating in the sensor array. The wavelength change for each grating is then used to calculate a physical parameter(s) to be measured, such as temperature and/or strain.