A specialized, dispersion-controlled fiber is particularly configured to exhibit a relatively uniform dispersion (D) over a broad spectral range (for example, 1000 nm to 2000 nm). The specialized fiber exhibits an essentially constant attenuation () over this same spectral range so that the fiber is defined as having a high figure of merit (FoM) where FoM is defined as |D|/. The specialized fiber is well-suited for use as a pulse stretcher, providing the ability to separate out wavelength constituents of an extremely short (fs, ps) broadband pulse into the ns range, for example.

An embodiment of a system for performing measurements in a downhole environment includes an optical interrogation assembly configured to emit a pulsed optical signal, the pulsed optical signal including a selected wavelength, and an optical fiber configured to be disposed in a borehole in an earth formation and configured to receive the pulsed optical signal, the optical fiber having at least one measurement location disposed therein and configured to at least partially reflect the pulsed optical signal. The optical fiber has a core and a cladding, at least a portion of the core made from at least substantially pure silica, and the optical fiber has a refractive index profile configured to have a zero dispersion wavelength that is greater than the selected wavelength.

Methods, apparatus, and systems comprising a fiber-coupled laser and time-varying beam characteristics. A laser may generate an optical beam that is launched into one or more lengths of fiber, at least one of which comprises a confinement region that is optically coupled to an output. A perturbation device may modulate, through action upon the one or more lengths of fiber, a beam characteristic over a time period during which the laser is energized. A controller may cause the perturbation device to act upon the one or more lengths of fiber to impart a time-averaged beam characteristic and/or to induce a continuous variation in one or more beam characteristics during system use. A process monitor may sense a metric external to the optical system, and a feedback signal from the process monitor may be coupled into the controller. Dynamic beam characteristics may be modulated based on the feedback signal.

A low attenuation optical fiber having a core doped with Ge is offered. The optical fiber consists of a glass part and a covering part formed around the glass part. The glass part is made of silica glass and includes: a Ge-doped center core region; an optical cladding layer formed around the center core region; and an optical cladding layer formed around the cladding layer. The relationship of 1>32 holds, where 1, 2, and 3 are the relative refractive index differences of the center core region, the cladding layer, and the cladding layer 30, respectively with respect to pure silica glass. The average outer diameter of the glass part is in the range of 1250.5 m in the longitudinal direction, and 3 is in the range of 0.1 m to 0.5 m, where is the standard deviation of the outer diameter in the longitudinal direction.

Disclosed herein are methods, apparatus, and systems for a multi-operation optical beam delivery device having a laser source to generate the optical beam. A beam characteristic conditioner that, in response to a control input indicating a change between the different laser process operations, controllably modifies the beam characteristics for a corresponding laser process operation of the different laser process operations. A delivery fiber has an input end coupled to the beam characteristic conditioner and an output end coupled to a process head for performing the corresponding laser process operation.

A low attenuation optical fiber having a core doped with Ge is offered. The optical fiber consists of a glass part and a covering part formed around the glass part. The glass part is made of silica glass and includes: a Ge-doped center core region; an optical cladding layer formed around the center core region; and an optical cladding layer formed around the cladding layer. The relationship of 1>32 holds, where 1, 2, and 3 are the relative refractive index differences of the center core region, the cladding layer, and the cladding layer 30, respectively with respect to pure silica glass. The average outer diameter of the glass part is in the range of 1250.5 m in the longitudinal direction, and 3 is in the range of 0.1 m to 0.5 m, where is the standard deviation of the outer diameter in the longitudinal direction.

Single mode optical fibers with a chlorine doped core and a cladding having a fluorine doped trench region are disclosed. The optical fiber includes a chlorine doped silica core having a core alpha 10, a core radius r.sub.1 and maximum refractive index delta .sub.1max % and a Cl concentration0.9 wt %. The optical fiber also has a cladding surrounding the core, the cladding having an inner and an outer cladding. The inner cladding has first and second cladding regions. The optical fiber has mode field diameter at 1310 nm of larger than 9 microns, a cable cutoff wavelength of 1260 nm, a zero dispersion wavelength .sub.0, where 1300 nm.sub.01324 nm, and bend loss at 1550 nm for a 20 mm mandrel of less than 0.5 dB/turn.

The invention concerns a multimode optical fiber, with a graded-index core co-doped with at least fluorine F and germanium GeO.sub.2 and a refractive index profile with at least two -values. According to the invention, the concentration of fluorine F at the core center ([F].sub.r=0) is between 0 and 3 wt % and the concentration of fluorine F at the core outer radius ([F].sub.r=) is between 0.5 wt % and 5.5 wt %, with [F].sub.r=[F].sub.r=0>0.4 wt %. For wavelengths comprised between 850 nm and 1100 nm, said multimode optical fiber has an overfilled launch bandwidth (OFL-BW) greater than 3500 MHz.Math.km and a calculated effective modal bandwidth (EMBc) greater than 4700 MHz.Math.km over a continuous operating wavelength range greater than 150 nm.

A low-loss few-mode fiber relates to the technical field of optical communications and related sensing devices, and includes, from inside to outside, a core layer (1), a fluorine-doped quartz inner cladding (2), a fluorine-doped quartz second core layer (3), a fluorine-doped quartz depressed cladding (4) and a fluorine-doped quartz outer cladding (5); germanium element is not doped within the core layer (1), the refractive index of the core layer (1) is in gradient distribution, and the distribution is a power-exponent distribution; the maximum value of difference in relative refractive index between the core layer (1) and the fluorine-doped quartz inner cladding (2) is 0.3% to 0.9%; the relative refractive index difference of the fluorine-doped quartz inner cladding (2) with respect to synthetic quartz is 0.3% to 0.5%; the difference in relative refractive index between the fluorine-doped quartz second core layer (3) and the fluorine-doped quartz inner cladding (2) is 0.05% to 0.2%; the difference in relative refractive index between the fluorine-doped quartz depressed cladding (4) and the fluorine-doped quartz inner cladding (2) is 0.1% to 0.5%; the relative refractive index difference of the fluorine-doped quartz outer cladding (5) with respect to synthetic quartz is 0.3% to 0.5%. The transmission loss of optical signals of the linear polarization modes that are supported by the few-mode fiber and the relay cost are reduced.

A low-loss few-mode fiber relates to the technical field of optical communications and related sensing devices, and includes, from inside to outside, a core layer (1), a fluorine-doped quartz inner cladding (2), a fluorine-doped quartz second core layer (3), a fluorine-doped quartz depressed cladding (4) and a fluorine-doped quartz outer cladding (5); germanium element is not doped within the core layer (1), the refractive index of the core layer (1) is in gradient distribution, and the distribution is a power-exponent distribution; the maximum value of difference in relative refractive index between the core layer (1) and the fluorine-doped quartz inner cladding (2) is 0.3% to 0.9%; the relative refractive index difference of the fluorine-doped quartz inner cladding (2) with respect to synthetic quartz is 0.3% to 0.5%; the difference in relative refractive index between the fluorine-doped quartz second core layer (3) and the fluorine-doped quartz inner cladding (2) is 0.05% to 0.2%; the difference in relative refractive index between the fluorine-doped quartz depressed cladding (4) and the fluorine-doped quartz inner cladding (2) is 0.1% to 0.5%; the relative refractive index difference of the fluorine-doped quartz outer cladding (5) with respect to synthetic quartz is 0.3% to 0.5%. The transmission loss of optical signals of the linear polarization modes that are supported by the few-mode fiber and the relay cost are reduced.