985 results about "Brillouin scattering" patented technology

Suppression of stimulated Brillouin scattering (SBS) by broadening the energy spectrum of participating SBS photons and/or phonons is achieved in an optical fiber having a core with both radially nonuniform viscosity and CTE profiles provided by alternating layers of glass modifying dopants such as phosphorous and fluorine. The nonuniform thermal expansion and viscosity profiles impart a residual, permanent, nonuniform stress in the fiber. The SBS suppressing effect provided by the nonuniform stress can be controlled and enhanced by applying a uniform or nonuniform tensile force to the fiber as it is being drawn. A preform for the fiber is also disclosed.

The invention discloses super-far distributed fiber Raman and Brillouin photon sensors; by using the stimulated Raman scattering effect of fiber, the self Raman scattering effect of fiber, the Brillouin scattering effect of fiber and the light time-field reflection principle, distributed fiber Raman photon temperature sensors, distributed fiber Brillouin photon strain sensors and distributed fiber Raman amplifier are integrated together. Fiber consumption is overcome by using the gain of amplifier, and strengths of self Raman scattering light and Brillouin scattering light in fiber is enhanced, the signal to noise ratio of the system of distributed fiber Raman photon sensor and distributed fiber Brillouin photon strain sensor is enhanced, meanwhile, the transmission distances of distributed fiber Raman photon sensor and distributed fiber Brillouin photon strain sensor are increased, finally, the temperature and stress measuring accuracy is enhanced.

A distributed fiber optic sensor simultaneously interrogates the sensing fiber with two counter propagating light beams. One beam is set to a constant frequency. The second beam is modified to contain a “comb” of frequencies, with each frequency component in the comb offset by a predetermined amount. Each of the frequency components in the comb, herein referred to as teeth, is able to interact with the counter-propagating beam through the Brillouin scattering process. With proper selection of the comb characteristics such as the number of teeth, the frequency spacing of teeth, the spectral width of teeth, and the relative amplitude of the teeth, a representation of the Brillouin spectrum at each point in the fiber can be obtained simultaneously with a single pass through the fiber.

An optical waveguide fiber having a high threshold for stimulated Brillouin scattering. The optical fiber preferably has large optical effective area, and further preferably has a low zero dispersion wavelength.

The present invention relates to an analog transmitter using an external cavity laser (ECL) in which specific characteristics of the ECL are enhanced and exploited to improve 2nd and 3rd order distortion while increasing the threshold for the occurrence of deleterious stimulated Brillouin scattering (SBS). The performance of the ECL shows a substantial reduction in distortion occurring over certain narrow ranges of operating temperatures. Optical, electronic, thermal and/or mechanical methods are described that cause this “distortion dip” to be moved to, or created at, stable regions of ECL operation, away from mode hops. Methods are also described that allow the distortion dip to be moved to, or created at, ECL operating regions in which sufficiently high chirp occurs, thereby reducing SBS. Transmitters and other devices employing these and related techniques are also described.

Apparatus and method for suppressing modal instabilities (MI) in fiber-amplifier systems. In some embodiments, thermal effects drive the MI process, and in some such embodiments, the present invention provides a plurality of options for mitigating these thermal effects. In some embodiments, the present invention provides a hybrid fiber with a smaller core in the initial length where the thermal loads are highest, followed by a larger-core fiber. In some embodiments the length of the smaller-core section is chosen to keep the core heat-per-unit-length of the second section below a critical value for the onset of MI. In some embodiments, the hybrid fiber of the present invention avoids modal instabilities while yielding almost the same performance as compared to conventional fibers with regard to minimizing fiber nonlinearities such as Stimulated Brillouin Scattering (SBS). In some embodiments, the hybrid fiber outputs a signal beam with at least 1 kW of power.

The invention discloses a method for a measuring sea water temperature profile based on an optical fiber Brillouin scattering principle. A Brillouin optical time domain reflection principle-based measurement system consists of a narrow line-width laser, an optical coupler, a pulse generator, an optical modulator, a circulator, an optical switch, a photoelectric detector, a Brillouin frequency shift detection unit and a sensing optical cable. The sensing optical cable used by the invention has a small size and sea water corrosion resistance, and is convenient to use. The measurement system has high reliability and high measuring sensitivity, can provide continuous temperature field distribution of the sea water profile, and is particularly suitable for real-time continuous measurement of the sea water temperature profile.

Methods and systems for increasing the threshold for stimulated Brillouin scattering are described. A seed source may generate one or more chirped seed pulses characterized by a pulse duration τ, and a frequency chirp. The pulse duration τ may be greater than about 2 nanoseconds. A photonic crystal amplifier amplifies the seed pulses to produce one or more amplified pulses characterized by a peak power P greater than about 1 kilowatt. The pulse duration τ, frequency chirp, and the photonic crystal fiber may be selected such that a threshold for stimulated Brillouin scattering (SBS) in the photonic crystal fiber is greater than the peak power P.

The invention discloses a sensing device of optical fiber distribution type temperature and stress and mainly comprises a light source module (1), a frequency discriminator module (2), and a thermo tank module (3), which are all connected with one another by polarization-preserving fiber. The invention is a direct detection method which is based on optical fiber Raman scattering used as a carrier wave of temperature information, brillouin scattering used as a carrier wave of stress, rayleigh scattering used for measuring relative frequency of a outgoing laser beam to a frequency discriminator and Fabry-Perot etalon used for discriminating frequency and distributing sensing temperature and stress. The invention has the advantages of simple structure, fine stability, avoidance of outgoing power of the light source during coherent detection, outgoing frequency of the light source. Instability of acoustic modulation or electro-optic modulation frequency is directly referred to measure errors and the direct detection technology of the frequency discrimination is not sensitive to frequency drift of the light source and fluctuation of signal intensity.

A distributed optical fiber sensor based on Raman and Brillouin scattering is provided. The distributed optical fiber sensor includes a semiconductor FP cavity pulsed wideband optical fiber laser (11), a semiconductor external-cavity continuous narrowband optical fiber laser (12), a wave separator (13), an electro-optic modulator (14), an isolator (15), an Er-doped optical fiber amplifier (16), a bidirectional coupler (17), an integrated wavelength division multiplexer (19), a first photoelectric receiving and amplifying module (20), a second photoelectric receiving and amplifying module (21), a direct detection system (22), a narrowband optical fiber transmission grating (23), a circulator (24) and a coherence detection module (25). The temperature and the strain can be measured simultaneously, and the signal-to-noise ratio of the system is enhanced.

A reinforcement element, comprises at least one sensor fiber adapted for strain measurements based on stimulated Brillouin scattering within said sensor fiber. Furthermore, a system for monitoring strain within a structure comprises a reinforcement element comprising at least one sensor fiber adapted for strain measurements based on stimulated Brillouin scattering within said sensor fiber, a pump laser for coupling in laser radiation of a pump frequency into said at least one sensor fiber, a Stokes laser for coupling in laser radiation of a Stokes laser radiation into said at least one sensor fiber, wherein the pump frequency and the Stokes frequency are different from one another and wherein the frequency difference between the pump and Stokes frequencies is within the range of acoustical phonons within said sensor fiber, a sensor adapted to obtain a stimulated Brillouin backscattering signal, and a network analyzer adapted for determining the complex transfer function of the sensor fiber to determine a spatially resolved strain measurement.

The invention discloses a broadband tunable single-passband microwave photon filter generating system. The system comprises a laser, an optical coupler, a polarization modulator, a dispersion displacement optical fiber, a photoelectric detector, a vector network analyzer, a strength modulator and an optical fiber; the laser is used for providing continuous light signals; the optical coupler is used for dividing the continuous light signals into the first path of light signals and the second path of light signals; the polarization modulator is used for modulating the polarization state of the first path of light signals; the dispersion displacement light fiber is used for performing stimulated Brillouin scattering on the detection light signals under the induction effect of pump light signals; the photoelectric detector is used for receiving the detection light signals which are processed in a stimulated Brillouin scattering mode and output by the dispersion displacement optical fiber and generating microwave signals; the vector network analyzer is used for receiving microwave signals output by the photoelectric detector, performing measurement frequency response on the microwave signals, and outputting the microwave signals to the a first polarization modulator at the same time; the strength modulator is used for modulating the polarization state of the first path of light signals and outputting the first path of light signals which are modulated; the optical fiber is used for filtering the first path of light signals which are modulated, and the first path of light signals serve as the pump light signals.

A method to increase the output power of narrow-linewidth rare earth-doped fiber amplifiers by suppressing simulated Brillouin scattering. The fiber amplifier is seeded with two or more lasers having frequencies and input powers that are sufficiently different. The seed signal with the highest emission cross section (e.g., signal 2) initially experiences the greatest gain. If signal 2 is also given sufficiently greater input power than signal 1, it will be amplified to its maximum value before the seed signals have reached the midpoint of the gain fiber. Beyond that point, the signal having the lower emission and absorption cross sections (signal 1) and significantly lower input power will continue to experience gain by power transfer from both signal 2 and the pump light, attaining a power output well beyond what the maximum output would have been had the amplifier been illuminated with a single frequency beam. This technique effectively reduces the Stokes light of signal 1, whereby higher power narrow-linewidth optical fiber amplifiers may be realized.