Provided are a monitoring device, a monitoring method, an optical amplifier, and an optical transmission system that are adapted for an increase in the number of cores in a multi-core optical fiber transmission path, and that are suitable for crosstalk monitoring. The monitoring device monitors a multi-core optical fiber transmission path comprising a plurality of use core and at least one or more non-use cores. The monitoring device comprises: an applying means for applying dithering to signal light propagating in the use cores; a monitoring means for monitoring the power of the non-use cores; and a separating means for separating a monitoring result from the monitoring means into power components from the plurality of use cores.

In various embodiments, multiple laser emitters are arranged in one or more linear stacks and emit beams to one or more linear stacks of interleaving mirrors. The interleaving mirrors direct the beams to a shared exit point, thereby forming an output beam stack. The optical distances traversed by each beam from its emitter to the shared exit point are all equal to each other.

A method for providing spectral beam combining (SBC) including generating a plurality seed beams each having a central wavelength and a low fill factor profile, where the wavelength of all of the seed beams is different; amplifying the seed beams; causing the amplified beams to expand as they propagate so as to be converted from the low fill factor profile to a high fill factor profile where the high fill factor profile tapers to a lower value at a perimeter of each beam; causing a wavefront of the converted beams to flatten to provide a plurality of adjacent SBC beams having different wavelengths with minimal overlap and a minimal gap between the beams; collimating the SBC beams; and directing the collimated SBC beams onto an SBC element that spatially diffracts the individual beam wavelengths and directing the beams in the same direction as a combined output beam.

An apparatus is provided, the apparatus comprising: (i) a diode-pumped solid-state laser oscillator configured to generate a pulsed laser beam having predefined beam characteristics corresponding to a current setting selection of a controller; and (ii) an amplifier configured to amplify an energy and modify a beam profile of the pulse laser beam. A beam detector is coupled to the generated beam to monitor a combination of: (i) a beam pulse width; (ii) a beam diameter; and (iii) an energy level, and generates an error signal to be sent back as a feedback signal to the controller. The controller configures the current source to output a correction current to tune the DPSSL oscillator, the wave plate, and the first polarizer to rotate a correction polarization angle and adjust the energy amplification or temporal profile to within a defined performance tolerance.

A single-frequency laser apparatus comprises a mirror and a volume Bragg grating (VBG) reflector defining a laser cavity therebetween and an optical gain material for emitting and amplifying an intra-cavity beam in the laser cavity. The optical gain material comprises a transition-metal doped crystal such as a crystal doped with transition-metal ions selected from one or more of Ti.sup.3+ ions, Cr.sup.2+ ions, Cr.sup.3+ ions or Cr.sup.4+ ions. A reflectivity spectrum of the VBG reflector and an optical length of the laser cavity are selected so that a beam output from the laser cavity is a single-frequency output beam and/or includes only one longitudinal mode of the laser cavity. The laser apparatus may provide a robust, compact, low cost, high-power wavelength adjustable (from approximately 650 to 950 nm), narrow linewidth (<100 kHz), single frequency laser source which is suitable for a wide range of applications from laser sensing, spectroscopy, and high precision frequency metrology sectors.

There is provided a laser controller comprising: an electromagnetic radiation source operable to transmit radiation into the environment; a backscatter detector operable to detect backscattered radiation from the environment; and a processor operable to generate a laser control signal based on characteristics of the detected backscattered radiation.

A high-precision repetition rate locking apparatus for an ultra-fast laser pulse includes: an electronic controlling component comprising: a standard clock, configured to provide a high-precision frequency standard; a pulse generator (PG), configured to provide an electrical pulse signal with adjustable repetition rate, pulse width and voltage magnitude; and a signal generator (SG), connected to the standard clock and the PG, and configured to provide a stable frequency signal for the PG, a phase-shift adjusting component, connected to the electronic controlling component and configured to implement phase modulation through electrically induced refractive index change; a resonant cavity component, comprising a phase shifter, a doped fiber, a laser diode, a wavelength division multiplexer and a reflector, and configured to generate a mode-locked pulse; and a detection system, configured to measure a repetition rate of an output pulse.

A laser system for amplifying laser light generated from a laser light source and emitting the laser light includes an optical element in an optical path of the laser light and transmits the laser light, a control device to control power to be supplied to the laser system, an imager to capture an image of the optical element, and an image processing circuitry to process the image of the optical element captured by the imager. The image processing circuitry in which reference images of the optical element corresponding to power information relating to the power are prepared in advance includes a comparison unit to compare a captured image of the optical element captured by the imager with a reference image selected by a reference image selection unit, the reference image corresponding to the power information at a time of image capturing by the imager.

A method for providing spectral beam combining (SBC) including generating a plurality seed beams each having a central wavelength and a low fill factor profile, where the wavelength of all of the seed beams is different; amplifying the seed beams; causing the amplified beams to expand as they propagate so as to be converted from the low fill factor profile to a high fill factor profile where the high fill factor profile tapers to a lower value at a perimeter of each beam; causing a wavefront of the converted beams to flatten to provide a plurality of adjacent SBC beams having different wavelengths with minimal overlap and a minimal gap between the beams; collimating the SBC beams; and directing the collimated SBC beams onto an SBC element that spatially diffracts the individual beam wavelengths and directing the beams in the same direction as a combined output beam.

A hybrid coherent beam combining (CBC) and spectral beam combining (SBC) fiber laser amplifier system including a beam shaper array assembly and a beam source that provides a plurality of beams having a low fill factor profile. The assembly includes an input beam shaper array having a plurality of rectilinear input cells positioned adjacent to each other that are shaped to cause the beam to expand as it propagates away from the input array to be converted from the low fill factor profile to a high fill factor profile. The assembly further includes an output beam shaper array having a plurality of output cells positioned adjacent to each other that are shaped to cause the beam to stop expanding so that the output array provides a plurality of adjacent beams with minimal overlap and a minimal gap between the beams.