219 results about "Nonlinear optical fiber" patented technology

An apparatus generates femtosecond pulses from laser amplifiers by nonlinear frequency conversion. The implementation of nonlinear frequency-conversion allows the design of highly nonlinear amplifiers at a signal wavelength (SW), while still preserving a high-quality pulse at an approximately frequency-doubled wavelength (FDW). Nonlinear frequency-conversion also allows for limited wavelength tuning of the FDW. As an example, the output from a nonlinear fiber amplifier is frequency-converted. By controlling the polarization state in the nonlinear fiber amplifier and by operating in the soliton-supporting dispersion regime of the host glass, an efficient nonlinear pulse compression for the SW is obtained. The generated pulse width is optimized by utilizing soliton compression in the presence of the Raman-self-frequency shift in the nonlinear fiber amplifier at the SW. High-power pulses are obtained by employing fiber amplifiers with large core-diameters. The efficiency of the nonlinear fiber amplifier is optimized by using a double clad fiber (i.e., a fiber with a double-step refractive index profile) and by pumping light directly into the inner core of this fiber. Periodically poled LiNbO3 (PPLN) is used for efficient conversion of the SW to a FDW. The quality of the pulses at the FDW can further be improved by nonlinear frequency conversion of the compressed and Raman-shifted signal pulses at the SW. The use of Raman-shifting further increases the tuning range at the FDW. For applications in confocal microscopy, a special linear fiber amplifier is used.

The polarization direction of an optical signal is changed by a polarization controller so as to be orthogonal to a main axis of a polarizer. A control pulse generator generates control pulses from control beam with a wavelength which is different from the wavelength of the optical signal. The optical signal and the control pulse are input to a nonlinear optical fiber. In the nonlinear optical fiber, the optical signal, during a time period in which the optical signal and the control pulse coincide, is amplified with optical parametric amplification around a polarization direction of the control pulse. The optical signal, during the time period in which the optical signal and the control pulse coincide, passes through the polarizer.

The polarization direction of a signal is rotated by a polarization controller so as to be orthogonal to the main axis of a polarizer. A control pulse generator generates control pulses from control source with a wavelength which is different from the wavelength of the signal. The signal and the control pulse are input to a nonlinear optical fiber. In the nonlinear optical fiber, the signal, during the time period in which the signal and the control pulse coincide, has its polarization direction rotated by cross phase modulation, and is amplified by optical parametric amplification. The signal, during the time period in which the signal and the control pulse coincide, passes through the polarizer.

Enhancement of the supercontinuum generation performance of a highly-nonlinear optical fiber (HNLF) is accomplished by performing at least one post-processing treatment on the HNLF. Particularly, UV exposure of the HNLF will modify its dispersion and effective area characteristics so as to increase its supercontinuum bandwidth, without resorting to techniques such as tapering or introducing unwanted reflections into the HNLF. The UV exposure can be uniform, slowly varying or aperiodic along the length of the HNLF, where the radiation will modify the nonlinear properties of the HNLF. Various other methods of altering these properties may be used. The output from the HNLF can be monitored and used to control the post-processing operation in order to achieve a set of desired features in the enhanced supercontinuum spectrum.

A method of and device for generating an amplified optical signal directly in an optical fiber by way of phase-sensitive amplification based on one or more four-wave mixing (FWM) processes. In one embodiment, an input signal and two pump waves are applied to a highly nonlinear fiber (HNLF). The input signal is amplified in the HNLF due to energy transfer from the pump waves to the input signal via a degenerate phase-conjugation (PC) process. In another embodiment, an input signal and first and second pump waves are applied to a first HNLF to generate, via a Bragg scattering (BS) process, an idler signal corresponding to the input signal. The second pump wave is then filtered out and the first pump wave, a third pump wave, and the input and idler signals are applied to a second HNLF, where they interact via a non-degenerate PC process to produce an amplified output signal.

An optical waveguide fiber having a high threshold for stimulated Brillouin scattering is disclosed which is suitable as a nonlinear fiber. The optical fiber has a core with one or more core segments. The optical effective area at a wavelength of 1550 nm is less that 30 μm².

Enhancement of the supercontinuum generation performance of a highly-nonlinear optical fiber (HNLF) is accomplished by incorporating at least one Bragg grating structure in the HNLF. The Bragg grating results in reflecting a core-guided signal into signal which also remains core-guided. The supercontinuum radiation generated by such an arrangement will exhibit a substantial peak in its energy at the grating resonance of the Bragg grating and a region of increased radiation in a narrow wavelength band on the long wavelength side of the peak. A number of such Bragg gratings may be formed so as to “tailor” the enhancements provided in the supercontinuum radiation. Various, well-known Bragg grating modifications (tuning, chirped, blazed, etc.) may also be used in the inventive structure to enhance the generated supercontinuum.

Apparatus and method for producing quantum entangled signal and idler photon pairs is provided. The apparatus makes use of a nonlinear optical fiber to generate the entangled photons. The use of an external broad band light source for alignment of any downstream measurement apparatuses is disclosed. One or more polarized output signals can be generated at both the signal and idler wavelengths using the alignment source, allowing the downstream measurement apparatuses to be aligned using classical light. Multiple signal and idler wavelengths can be generated and aligned using such a system.

An arrangement for generating beat notes with a relatively high signal-to-noise ratio (SNR) utilizes a pulsed laser source coupled into a section of post-processed highly-nonlinear optical fiber (HNLF) to generate a frequency comb having one or more regions of enhanced spectral power. A second laser signal source is overlapped with the frequency comb to form one or more “beat notes” at difference frequencies(y) between the second source and the continuum comb. By virtue of the post-processing, areas of spectral enhancement are formed along the comb, and are positioned to interact with the second laser signal to generate optical beat notes. The second laser signal may be from an external source (forming beat notes from a signal “outside” of the comb), or may be a frequency-multiplied version of the generated supercontinuum (forming beat notes from a signal “within” the comb).

The invention relates to a femtosecond laser carrier envelope offset frequency lock system based on a heterodyne interferometric method. The system is characterized by comprising a femtosecond laser light source system, an acousto-optic modulator, a controllable optical path retardation device, a light splitting prism, a first photoelectric detector, a phase lock amplifier, a phase difference voltage conversion device and a PID controller. Heterodyne interferometry can be conducted on first-level phase-shift diffraction light modulated by the acousto-optic modulator and zero-level diffraction light which is not modulated, and after mixing of interference signals with different wavelengths, direct-current level lock pulse envelope alignment is achieved; optical frequency comb envelope offset frequency is locked by means of interference signal phase, the linear process does not exist, high non-linear optical fibers, frequency doubling crystals and the like are not needed, and the system is simple in structure and low in requirement for laser energy.

The invention relates to SI (Spectrum Inversion)-based nonlinear fiber damage compensation method and device in an O-OFDM (Optical-Orthogonal Frequency Division Multiplexing) system, belonging to the field of optical communication and applied to the O-OFDM system for nonlinear fiber damage compensation. The whole compensation module is arranged in front of a receiver of the O-OFDM system and comprises an SI unit and an HNLF (Highly Non-Linear Fiber) which has a certain length and is arranged behind the SI unit, wherein SI is realized by an SOA (Semiconductor Optical Amplifier) based on FWM (Four Wave Mixing) effect.

The invention discloses an optically controlled optical PAM signal regeneration device comprising a power adapting unit, an optical clock control unit and a PAM reshaping unit, wherein the PAM reshaping unit is the core of a regenerator and is composed of a Mach-Zehnder interferometer MZI and a highly nonlinear fiber ring NOLM, for a to-be-regenerated degraded optical PAM signal, the level matching between the input degraded optical PAM signal and the PAM reshaping unit is accomplished by the power adapting unit, the optical clock signal power and the delay output by the optical clock control unit and a phase shifter in the MZI structure are adjusted, so that the PAM reshaping unit works normally, the loss coefficient, the optical fiber length, the nonlinear coefficient and other parameters of a highly nonlinear optical fiber in the NOLM structure, and the coupling coefficients of front and back couplers in the MZI structure are changed to design PAM reshaping units with different level numbers, and then the regeneration of the degraded optical PAM signal is accomplished. Therefore, the optically controlled optical PAM signal regeneration device disclosed by the invention can execute a reshaping and a re-timing function and has the advantages of flexible design of regeneration level numbers.

The invention relates to a fiber optical parametric oscillator for achieving Fourier domain mode-locked laser output. Seed light output by two semiconductor lasers is modulated by phase and amplified by a high power optical amplifier to serve as pump light, the pump light is output from the pump output end of a wavelength division multiplexer and enters high nonlinear fiber through a polarization controller, and a part of the pump light is transferred into signal light in the high nonlinear fiber due to fiber nonlinear effect. After the signal light passes through a second optical isolator, dispersion-shifted fiber and a tunable filter, most energy is fed back to the high nonlinear fiber from a high power shunt ratio output end of an optical coupler with 9:1 power shunt ratio through the wavelength division multiplexer so as to form resonance laser output. When modulation frequency of the tunable filter is equal to fundamental frequency of a laser resonant cavity, the Fourier domain mode-locked laser output can be obtained. The fiber optical parametric oscillator achieves the Fourier domain mode-locked laser output, has significant application value in the fields of optical tomography, fiber bragg grating sensing and the like, and has the advantages of being high in wavelength scanning frequency, flexible in laser output spectrum tuning range control and the like.

The invention discloses a multi-frequency microwave signal photon instantaneous frequency measuring device with a super-wide frequency range, and belongs to the technical field of microwave photonics. The multi-frequency microwave signal photon instantaneous frequency measuring device with the super-wide frequency range comprises a laser, a coupler, a phase modulator, a polarization controller, a highly nonlinear optical fiber, a circulator, a first double-parallel MZ modulator, a second double-parallel MZ modulator, an intensity modulator, a microwave coupler, a photoelectric detector and a network analysis instrument. First-order upper side band signals output by the phase modulator are strengthened or weakened through the stimulated Brillouin scattering effect of the highly nonlinear optical fiber, the intensity balance of the first-order upper side band and the first-order lower side band of the output signals of the phase modulator is broken, and therefore instantaneous frequency measurement of multi-frequency microwave signals to be measured is achieved.

The invention relates to a multifunctional optical signal processing system. In the system, continuous detection light and signal light are combined through a first coupler and injected into a high nonlinear optical fiber; idle light generated in the high nonlinear optical fiber due to a fourwave mixing effect is divided into two paths through an optical filter and an optical coupler and are output, wherein one output path is connected to an optical power meter, the optical power output performs feedback control on a tunable dispersion compensator so as to realize dynamic dispersion compensation, while the other output path is used as a system output signal to generate an optical signal with high extinction ratio and no dispersion; and the wavelength of the output optical signal is changed by regulating the wavelength of the detection light, so that tunable wavelength conversion is realized. The multifunctional optical signal processing system can realize HNLF (High Nonlinear Fiber), dispersion detection, extinction ratio enhancement and wavelength conversion, has the advantages of multifunction integration, high response speed, high sensitivity of dispersion detection, wide working wave band and transparency to signal speed and modulation format and can be applied to an optical transmission system with channel rate of over 40Gb/s.

The invention discloses a safety monitoring system of a long-distance pipeline, comprising a transmitted and received light signal processing module 1, a light delay component 2, a single-line optical fiber 3 and a nonlinear optical environment 4 with a probing blind area, which are all formed into a variant-type optical fiber Sagnac interferometer. A polarization control element is used for ensuring the maximum interference intensity, and at least three wavelengths and three coherent light pulse signals are used for independently obtaining data to inhibit noise produced by the light source fluctuation and the polarization state change. The preservation time of A/D sampling is greater than the value of a pulse width, and the A/D sampling frequency is greater than the light source repetition frequency. A probe completely transforms each returned coherent light pulse so that an electric signal is undistorted. A single detection system has no relay to detect the distance of over 100 km.

The invention discloses a microwave photon up-conversion device and method based on a photoelectric oscillator and belongs to the technical field of microwave photonics. The device is composed of a laser source, a first coupler, a first circulator, a first high nonlinearity dispersion displacement optical fiber, an erbium-doped optical fiber amplifier, a first photoelectric detector, a second coupler, a first Mach-Zehnder modulator, a first microwave signal source, a first direct current voltage-stabilized power supply, an optical filter, a second Mach-Zehnder modulator, a second direct current voltage-stabilized power supply, a second circular, a second high nonlinearity dispersion displacement optical fiber, a second photoelectric detector, a microwave amplifier, a double-parallel Mach-Zehnder modulator, a third direct current voltage-stabilized power supply, a fourth direct current voltage-stabilized power supply, a fifth direct current voltage-stabilized power supply, an optical isolator and a spectrum analyzer. A Brillouin frequency shift value f of the high nonlinearity optical fiber is 9.2GHz, and a signal with frequency of f<m> can be up converted to f<m>+18.4GHz, so alow quality and low frequency intermediate signal is converted into a high quality and high frequency signal.