An arrangement and method that compensates for variation in grating strength associated with forming multiple gratings in multicore fiber is proposed where the writing efficiency of the beam(s) used to form the gratings is controlled to compensate for fiber lensing effects. In one case, a spacing between the multicore optical fiber and the beam source is controlled such that the writing efficiency (which decreases as a function of the space between the source and the fiber) compensates (at least in part) for the increased beam intensity attributed to the lensing effect of the fiber itself. The width of beam itself may also be controlled to modify the writing efficiency.

A sensor system includes a femtosecond infrared (fs-IR) laser to generate a laser beam; a reflecting mirror optically receiving the laser beam; a lens optically coupled to the reflecting mirror to focus the laser beam; a phase mask receiving the laser beam from the lens to generate an index modulated pattern; and a few-mode fiber (FMF) receiving the index modulated pattern.

Improved Raman Fiber Laser (RFL) generators may include a mid-infrared fiber, e.g., a fiber comprising a tellurite glass, a chalcogenide glass, a fluoride glass, or similar material. A phase-shifted fiber Bragg grating may be inscribed in the fiber. A pump laser generator may be coupled with the fiber in order to supply a pump laser to the fiber. When stimulated by the pump laser, the RFL generator may emit an output laser having a mid-infrared wavelength. A tuner may be used to tune the output laser.

There is provided an alignment system and method for use in an ultrashort pulse duration laser-based Fiber Bragg Grating (FBG) writing system, the alignment system comprising: clamps configured to hold a coated optical fiber in a position perpendicular to a beam path of an ultrashort pulse duration laser-based FBG writing station; an optical detector; and a control system with an input from the optical detector and an output to adjust parameters of an optical source and the FBG writing station adjust a distance between the optical fiber and an optical source of the writing station based on luminescence generated in a core of the optical fiber as indicated in a signal received at the input from the optical detector.

A technique is described for fabricating one or more optical devices in a carbon-coated optical fiber. A photosensitive optical fiber is provided having a hermetic carbon coating. Further provided is a laser having a beam output that is configured to inscribe one or more refractive index modulations into the optical fiber through the hermetic carbon layer while leaving the hermetic carbon layer intact. The laser is used to inscribe one or more optical devices into the optical fiber through the hermetic carbon layer.

A method for obtaining transient Bragg gratings in optical waveguides and several different applications of the transient Bragg gratings obtained using this method are presented. The basic mechanisms for obtaining the transient gratings in the waveguides are refractive index change due to Kerr nonlinearity, free carrier generation, and gratings formed by linear or non-linear absorption of thermal energy. The exemplary applications include an ultra-fast fiber laser source at any central wavelength, a fast spectral switch/modulator, transient pulse stretchers based on transient chirped gratings, Q-switching based on transient gratings, and time reversal of ultra-short pulses and low power sub-nanosecond pulse generations.

A method and a system for providing a low absorption Bragg grating along a grating region of an optical fiber are presented. The Bragg grating is written along the grating region by multiphoton absorption of ultrafast light pulses impinged on this grating region through a polymer coating of the optical fiber. The Bragg grating is then photobleached by propagating a photobleaching light beam along the optical fiber. The photobleaching light beam has optical parameters selected to reduce defects in the grating region induced by the writing of the Bragg grating in a substantially non-thermal regime.

A method and apparatus for inscribing a Bragg grating in an optical waveguide, comprising: providing electromagnetic radiation from an ultrashort pulse duration laser, wherein the electromagnetic radiation has a pulse duration of less than or equal to 5 picoseconds, and wherein the wavelength of the electromagnetic radiation has a characteristic wavelength in the wavelength range from 150 nanometers (nm) to 2.0 microns (m): providing cylindrical focusing optics corrected for spherical aberration: providing a diffractive optical element that when exposed to the focused ultrashort laser pulse, creates an interference pattern on the optical waveguide, wherein the irradiation step comprises irradiating a surface of the diffractive optical element with the focused electromagnetic radiation, the electromagnetic radiation incident on the optical waveguide, from the diffractive optical element, being sufficiently intense to cause the permanent change in the index of refraction in the core of the optical waveguide.

Improved Raman Fiber Laser (RFL) generators may include a mid-infrared fiber, e.g., a fiber comprising a tellurite glass, a chalcogenide glass, a fluoride glass, or similar material. A phase-shifted fiber Bragg grating may be inscribed in the fiber. A pump laser generator may be coupled with the fiber in order to supply a pump laser to the fiber. When stimulated by the pump laser, the RFL generator may emit an output laser having a mid-infrared wavelength. A tuner may be used to tune the output laser.

A delay line interferometer comprising an optical waveguide having a distributed Bragg reflector, e.g. Bragg grating, fabricated therein. The distributed Bragg reflector has a refractive index modulation with a period variation (z) along its length z that is arranged to output in transmission an output optical signal f.sub.out(t) in response to a input optical signal f.sub.in(t), wherein the output optical signal f.sub.out(t) is the result of temporal interference between one or more time-delayed replicas of the input optical signal f.sub.in(t). In other words, the distributed Bragg reflector is operable to generate and permit temporal interference between two or more time-delayed replicas of the input optical signal f.sub.in(t). The invention may thus mimic the behaviour of one or more MZIs.