A low-noise amplifier includes a gain medium and two or more amplifier stages. Each amplifier stage includes an optical filter to pass all wavelengths of a respective input optical signal in a given propagation direction over the gain medium and reflect wavelengths above a respective threshold wavelength received in the opposite direction, and a respective Raman pump to inject a pump light centered at a wavelength lower than the threshold wavelength onto the gain medium for transmission in the given direction. A first amplifier stage outputs a first combined optical signal including all wavelengths of the respective input optical signal and a pump light injected by the respective Raman pump. The second amplifier stage receives the first combined optical signal as its input and outputs a second combined optical signal including all wavelengths of the first combined optical signal and a pump light injected by the respective Raman pump.

A fibre laser assembly includes a pump laser assembly for optical pumping of an active fibre with first pump radiation of a first pump wavelength and means for the generation of second pump radiation at a second pump wavelength, which lies between the first pump wavelength and the wavelength of the seed laser. Doping concentration, length of the active fibre, and power of the first pump radiation are coordinated such that the active fibre absorbs the first pump radiation in the first fibre portion to >90%, the radiation of the second pump wavelength in the first fibre portion is amplified by the first pump radiation to generate the second pump radiation, and the laser radiation of the seed laser is amplified in the remaining second fibre portion by the second pump radiation.

The present disclosure generally relates optical amplifier modules. In one form for example, an optical amplifier module includes a booster optical amplifier configured to increase optical power of a first optical signal. The module also includes a preamp optical amplifier configured to increase optical power of a second optical signal and a pump laser optically coupled to the booster optical amplifier and the preamp optical amplifier. The pump laser is configured to provide a booster power to the booster optical amplifier and a preamp power to the preamp optical amplifier, the preamp power is effective to induce a gain in optical power to provide a target optical power of the second optical signal from the preamp optical amplifier, and the booster power is dependent on the preamp power.

A method of propagating a laser signal through an optical waveguide and a waveguide laser system provide a novel way of stabilizing the beam emitted by a fiber laser system above the mode instability threshold wherein the beat length of two or more interfering transverse modes of the laser signal in the optical waveguide is modulated in time.

An Nd.sup.3+ optical fiber laser and amplifier operating in the wavelength range from 1300 to 1450 nm is described. The fiber includes a rare earth doped optical amplifier or laser operating within this wavelength band is based upon an optical fiber that guides light in this wavelength band. The waveguide structure attenuates light in the wavelength range from 850 nm to 950 nm and from 1050 nm to 1150 nm.

A system (e.g., an optical amplifier) comprising gain fibers (e.g., Bismuth-doped optical fiber) for amplifying optical signals. The optical signals have an operating center wavelength (?0) that is centered between approximately 1260 nanometers (?1260 nm) and ?1360 nm (which is in the O-Band). The gain fibers are optically coupled to pump sources, with the number of pump sources being less than or equal to the number of gain fibers. The pump sources are (optionally) shared among the gain fibers, thereby providing more efficient use of resources.

A mid-infrared cascading fiber amplifier device having a source configured to generate a first electromagnetic wave output at a first frequency, a fiber coupled to the source and a pump coupled to the fiber and configured to generate a second electromagnetic wave output at a second frequency, wherein the second frequency is higher than the first frequency and causes the fiber to undergo two or more transitions in response to stimulation by the first electromagnetic wave output at the first frequency, wherein the first transition generates the first electromagnetic wave output approximately at the first frequency and the second transition generates the first electromagnetic wave output approximately at the first frequency.

Disclosed herein is an optical fiber laser device including a seed unit for providing at least two seed lights having different wavelengths; and an amplifying unit for amplifying the at least two seed lights. The amplifying unit includes: a preamplifying unit for amplifying the at least two seed lights by using excitation light of which the wavelength is shorter than the wavelengths of the seed lights; and a final amplifying unit to which no separate excitation light source is provided. The final amplifying unit amplifies the seed light having the longest wavelength by using the other seed light as excitation light with respect to the seed light having the longest wavelength among the at least two seed light.

A mid-infrared cascading fiber amplifier device having a source configured to generate a first electromagnetic wave output at a first frequency, a fiber coupled to the source and a pump coupled to the fiber and configured to generate a second electromagnetic wave output at a second frequency, wherein the second frequency is higher than the first frequency and causes the fiber to undergo two or more transitions in response to stimulation by the first electromagnetic wave output at the first frequency, wherein the first transition generates the first electromagnetic wave output approximately at the first frequency and the second transition generates the first electromagnetic wave output approximately at the first frequency.

An optical amplifier may comprise a first gain stage and a second gain stage. Each of the first and second gain stages may comprise a laser pump and an active fiber. A liquid crystal device may be coupled between an output of the first gain stage and an input of the second gain stage. A control unit may be coupled to the first and second gain stages, liquid crystal device and configured to control the first and second gain stages, and the liquid crystal device to provide a switchable gain. Light may pass through the first and second gain stages and be amplified by the first and second gain stages. The light amplified by the first gain stage may pass through the liquid crystal device and may be filtered by the liquid crystal device.