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.

The present disclosure discloses a degassing-free underwater dissolved carbon dioxide detection device and a detection method. The degassing-free underwater dissolved carbon dioxide detection device includes a computer, which is used to provide the driving signal and controlling parameters for the power tuning unit; the computer is connected with a laser driving control module and the power tuning unit, respectively; the laser driving control module is connected with a laser; the laser is connected with a photo-isolator; the photo-isolator is connected with a thulium-doped fiber vertical-cavity laser system; the thulium-doped fiber vertical-cavity laser system is connected with a photoacoustic cell system through a fiber collimator; the photoacoustic cell system is connected with a pre-amplifier circuit and a lock-in amplifier in sequence, and the lock-in amplifier is connected with the computer.

Systems and methods are provided for creating a sequence of turn-up processes for amplifiers. A method, according to one implementation, includes determining when a fiber span is initially installed in an optical line system or when an Optical Line Failure (OLF) in the fiber span has recovered. The optical line system includes a first set of amplifiers deployed at an upstream node and a second set of amplifiers deployed at a downstream node, the upstream node connected to the downstream node via the fiber span. In response to determining that the fiber span is initially installed in the optical line system or that an ORL in the fiber span has recovered, the method also includes sending a flag from the upstream node to the downstream node to allow the first set of amplifiers to perform a first turn-up process before the second set of amplifiers perform a second turn-up process.

A device for generating laser pulses is provided, the device having an optical parametric oscillator converts the laser pulses of a pump laser to laser pulses at a signal wavelength and at an idler wavelength. The optical parametric oscillator has an optical resonator with a non-linear wavelength converter. It is an object of the invention to provide a device that makes efficient generation of synchronous laser pulse trains with two different central wavelengths possible. To this end, the invention proposes that the pump laser is tunable with respect to the pump wavelength and the repetition frequency, wherein the resonator has an optical fibre with a dispersion in the range of 10-100 ps/nm and a length of 10-1000 m. The invention furthermore relates to a method for generating laser pulses using such a device.

A device for generating laser pulses is provided, the device having an optical parametric oscillator converts the laser pulses of a pump laser to laser pulses at a signal wavelength and at an idler wavelength. The optical parametric oscillator has an optical resonator with a non-linear wavelength converter. It is an object of the invention to provide a device that makes efficient generation of synchronous laser pulse trains with two different central wavelengths possible. To this end, the invention proposes that the pump laser is tunable with respect to the pump wavelength and the repetition frequency, wherein the resonator has an optical fibre with a dispersion in the range of 10-100 ps/nm and a length of 10-1000 m. The invention furthermore relates to a method for generating laser pulses using such a device.

A laser device includes a seed laser, a plurality of optical amplifiers, and an optical distribution assembly. The seed laser is configured to emit seed laser light. The plurality of optical amplifiers is configured to generate amplified laser light by amplifying the seed laser light. The optical distribution assembly is configured to distribute the seed laser light to an input of each of the optical amplifiers in the plurality and each of the optical amplifiers is configured to direct its respective amplified laser light to a common target.

An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The quantum well active layer is doped with 0.3 to 1×10.sup.18/cm.sup.3 of n-type impurity.

An object of the present disclosure is to allow gain compensation with a simple configuration without adding a new device to the outside. The present disclosure discloses a rare earth doped fiber including a core doped with a rare earth and a cladding region around the core, wherein one or more cavities are provided inside the core, and at least one of the cavities are provided along a longitudinal direction of the rare earth doped fiber.

An optical fiber amplification. system includes: a first optical fiber amplifier including a first optical amplifying fiber including a core portion doped with a first rare-earth. element, a first input unit configured to receive first signal light, an excitation-light source configured to output pump light, a pump light combiner configured to input the pump light to the first optical amplifying fiber, and a residual pump light recovery device configured to recover residual pump light; and a second optical fiber amplifier including a second optical amplifying fiber including a core portion doped with a second rare-earth. element, a second input unit configured to receive second signal light, and a residual pump light combiner configured to input, to the second optical amplifying fiber, the residual pump light recovered by the residual pump light recovery device.

An optical fiber connector includes: amplifying fibers in which an active element activated by excitation light is added to a core of each of the amplifying fibers. The amplifying fibers are connected together such that an absorption amount of excitation light per unit length increases with an increase of a distance from an incident end of the excitation light. A mode field diameter of laser light propagating through the core is same among the amplifying fibers.