352 results about "Erbium doped fiber amplifier" patented technology

An approach for automatic Raman gain and tilt control for a WDM (Wavelength Division Multiplexing) optical communication systems is disclosed. An optical fiber carries a plurality of optical signals, in which at least one of the optical signals are reference signals. An optical gain unit (e.g., Raman pump unit) couples to the optical fiber and adjusts the reference signals to compensate, in part, for losses associated with the optical fiber and gain tilt accumulation. Upon detecting and analyzing the reference signals, a controller controls the optical gain unit and outputs a control signal to the optical gain unit based upon the analyzed reference signals. An optical amplifier is connected to the optical fiber and amplifies the optical signals. The optical gain unit provides a nearly constant power per channel at an input of the optical amplifier. Under this approach, a Raman gain control mechanism, combined with the use of gain controlled EDFA (Erbium Doped Fiber Amplifier), allows high transmission capacity over ultra-long distances without optical regeneration and with high flexibility.

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.

The invention relates to a serial-parallel connection modulation optical frequency multiplication millimeter-wave RoF (Radio Over Fiber) system and a QPSK (Quadrature Phase Shift Keying)/16QAM (Quadrature Amplitude Modulation) modulation method thereof. The system comprises a central station, a base station and fiber connection thereof, wherein the central station comprises a single longitudinal mode laser, a double-electrode Mach-Zehnder optical modulator, an IQ optical modulator, two microwave signal sources, a pi phase shifter, a pi/2 phase shifter and an erbium doped fiber amplifier; and the base station comprises an optical detector, a front low-noise amplifier, two millimeter-wave bandpass filters, two millimeter-wave amplifiers, a millimeter-wave duplexer and a millimeter-wave antenna. In the method, the cascading of the double-electrode Mach-Zehnder optical modulator and the IQ optical modulator is adopted, and a balanced optical waveguide structure formed by integrating the two optical modulators avoids the influence of optical source phase interference noise caused by support arm optical delay inequality on modulation signals.

The invention discloses a microwave photon mixing method and system based on local oscillator frequency doubling, and belongs to the fields of optical communication and microwave photonics. The microwave photon mixing system based on local oscillator frequency doubling is formed by utilizing a double-polarization double-parallel mach-zehnder modulator through combination with devices such as a laser, a front polarization controller, a microwave 90-degree coupler, a rear polarization controller, an optical fiber polarizer, an adjustable optical band-pass filter, an erbium-doped fiber amplifier,a photoelectric detector and the like. The system adopts second-order local oscillator sideband and first-order radio frequency sideband beat frequencies, and mixing processing based on local oscillator frequency doubling can be realized; on one hand, the frequency requirement of a mixing system on a local oscillator signal is reduced, and on the other hand, due to the fact that a single-sidebandmodulation mode is adopted, stray signals can be effectively reduced. In addition, the mixing method can realize switching of up conversion and down conversion by changing a direct current bias voltage, and can be used for time-sharing transmitting and receiving of radio frequency.

A real-time scattering type terahertz quasi-time-domain near field polarization spectrograph comprises a multimode laser module, an erbium-doped fiber amplifier, an optical fiber beam splitter, a photoconduction transmitting antenna, a polarization module, a focusing lens A, an atomic force microscope, a focusing lens B, an optical fiber extension module, a photoconduction receiving antenna and a phase-locked amplifier. The multimode laser module emits a multimode laser, the multimode laser passes through the erbium-doped fiber amplifier and is split into a pumping light beam and a detection light beam, the pumping light beam stimulates the photoconduction transmitting antenna module to radiate a quasi-time-domain terahertz signal, the terahertz signal is transmitted to an oscillating probe tip of the atomic force microscope, the detection light beam enters the photoconduction receiving antenna, and finally the signal is extracted and amplified through the phase-locked amplifier. The spectrograph has the advantages of being low in cost, small in size and not prone to hurting eyes, having the real-time performance, and the like, and can be widely applied to the field of super-resolution detection on terahertz signals in scientific research and industry.

The invention relates to the technical field of fiber sensing, and especially to a pre-pumped pulse and Gray code based BOTDA instrument. The BOTDA instrument comprises a narrow-linewidth semiconductor sensor, a coupler, a first erbium doped fiber amplifier, a first polarization controller, a single sideband modulator, a microwave source, an optical isolator, a sensing fiber, an optical annular device, a second erbium doped fiber amplifier, a polarization scrambler, an electro-optical intensity modulator, a second polarization controller, an arbitrary waveform generator, an optical filter, a photoelectric detector and a signal collecting and processing system. On the premise that the high spatial resolution of a BOTDA system is maintained, the BOTDA instrument ensures the sensing distance and the measuring precision of the system, and improves the sensing performance of the system.

An all-optical true random number generator with a Tbps code rate comprises an all-optical true random number entropy source and an all-optical quantizer, wherein the all-optical true random number entropy source adopts an rational harmonic mode-locked Er-doped fiber ring laser, actually a ring-shaped cavity formed by a lithium niobate electro-optic modulator, an optical band pass filter I, an erbium-doped fiber amplifier, an opto-isolator and an optical coupler which are connected through fiber; and the all-optical quantizer is a quantum dot quarter wave phase-shift distributed feedback type laser. The generator provided by the invention solves the problems that the code rate is too low and untunable in the prior art, has a Tbps-level code rate, is in direct compatible with an optical network, and meets the safety requirements of modern high-speed secure communication.

The invention discloses a backscattering enhanced fiber distribution type temperature and strain dual-parameter sensing device and a demodulation method thereof. The sensing device is composed of a narrow-linewidth light source, a coupler, an acousto-optic modulation module, a driver, an erbium-doped fiber amplifier, a circulator, a Raman wavelength division multiplexer, a sensing fiber having a plurality of continuous scattering enhanced point, a filter device, a photoelectric detector, a data acquisition card, and an upper computer. The implementation principle of dual-parameter measurementis as follows: on the basis of the sensitivity to the external environment change by a phase of a backscattering Rayleigh light signal in a sensing fiber and sensitivity to a temperature change by a Raman scattered light intensity, an implementation scheme of absolute temperature stress distributed measurement is provided by using an optical time domain reflection technology, a coherent detectiontechnology, a beat frequency signal cross correlation technology, a phase demodulation technology, a wavelength division multiplexing technique, and a temperature stress decoupling technique. Therefore, simultaneous measurement of a temperature field and a stress field continuously distributed along the optical fiber is realized. Moreover, the measuring distance is long; the spatial resolution ishigh; the sensitivity is high; the response speed is fast; and the error is small.

The invention is suitable for the technical field of optical communication and provides a hybrid optical fiber amplifier as well as a method and device for adjusting the gain and the gain slope of the amplifier. The hybrid optical fiber amplifier comprises an RFA (Raman fiber amplifier) and an EDFA (erbium doped fiber amplifier), wherein the EDFA excludes a variable attenuator; the RFA comprises a pump signal multiplexer, a pump laser group, an out-of-band narrow-band filter and a photoelectric detector; the EDFA comprises an input coupler, an erbium doped fiber, an output coupler, an input photoelectric detector and an output photoelectric detector, all of which are connected in sequence; and the hybrid optical fiber amplifier further comprises a control module for controlling the RFA and/or EDFA to adjust the gain and/or the gain slope according to an excepted amplification requirement. Due to the fact that the RFA and the EDFA are controlled and coordinated by the control module according to the technical scheme, an excepted amplification effect can be achieved; in addition, a series of problems caused by the variable attenuator can be avoided due to the fact that the EDFA excludes the variable attenuator.

The invention discloses a sensing device based on Raman-Brillouin distributed temperature and stress dual-parameter detection. The sensing device is composed of a laser, a first coupler, a polarization controller, a pulse generator, a semiconductor optical amplifier, an erbium-doped fiber amplifier, a band-pass filter, a second coupler, an optical attenuator, a first circulator, a third coupler, a multi-core fiber, a second circulator, a Raman filter, a first d photoelectric detector, a second photoelectric detector, an oscilloscope, a polarization controller, a modulator, a microwave generator, a polarization switch, a fourth coupler, a third photoelectric detector, a power spectrum analyzer and a data processing module. Because a spatial-division multiplexing system is formed by using a single-mode multi-core fiber, a problem of mode coupling of a mode -division multiplexing system and power mismatching of a wavelength-division multiplexing system can be solved and thus an effect of precise and simultaneous temperate and stress obtaining can be realized.

The invention discloses a microwave signal photonic frequency conversion and multichannel fiber transmission device and method realized by a polarization multiplexing modulator. The device, as shown by a figure, comprises a laser diode (LD), a polarization multiplexing Mach-Zehnder modulator (PDM-MZM), an erbium doped fiber amplifier (EDFA), a 1:N light splitter (Splitter), a polarizer (Pol), a polarization controller (PC), and a standard single-mode fiber (SMF) and a photoelectric detector (PD). The PDM-MZM is used to carry out carrier suppressed double side band modulation on radio frequency (RF) and local oscillation (LO) signals and then implement frequency mixing, and the RF and LO isolation degree of frequency conversion gain and frequency conversion signals is improved. Optical signals output by the modulator can be divided into multiple paths to implement fiber transmission, each path is adjusted via an independent polarization state, and power attenuation caused by dispersion can be compensated.

Erbium doped fiber amplifiers (ERDAs) optically couple optical signals between free-space and fiber optic links of a terrestrial optical communication network. The optical gain of transmitting and receiving ERDAs is controlled to achieve good optical signal communication. Control occurs in response to signals received at the transmitting and receiving ends of the links. Control, status and management information may be communicated optically between link head stations. The physical position of transceivers at opposite ends of the link optical signal paths is also controlled.

The invention relates to the field of an ROF (Radio Frequency Oscillator). The embodiment of the invention discloses a quadruplicated frequency millimeter wave generation method based on a double-parallel MZ (Mach-zehnder) modulator (DPMZM). The method comprises the main steps of: taking a laser source as a carrier, and loading the carrier on two arms of a main modulator; driving two MZ sub-modulators of an integrated modulator through the same radio frequency local oscillator, wherein a phase difference is pai; and amplifying through an EDFA (Erbium Doped Fiber Amplifier), beating frequency through PD (Potential Difference), and obtaining a quadruplicated radio source frequency millimeter wave signal.

The invention discloses a method for realizing photonic frequency conversion and multi-channel phase shift of a microwave signal by using a dual-polarization quadrature phase shift keying (DP-QPSK) modulator, relates to the technical field of microwaves and the technical field of optical communication, and can be mainly applied to beam forming, IQ demodulation and the like of the signal. As shownin an attached drawing, the scheme comprises a light source, a local oscillation source, an erbium-doped optical fiber amplifier, an optical splitter, a polarization controller, a polarizer and a photoelectric detector. According to the invention, the DP-QPSK modulator is used for carrying out modulation and polarization multiplexing on a radio frequency signal and a microwave local oscillator, after light amplification, power is divided into multiple paths, each path controls the amplitude and phase of an output signal through the polarization controller and the polarizer, and finally a phase-changed intermediate frequency signal is obtained through the photoelectric detector. According to the invention, the up-down frequency conversion and phase shift functions of signals can be realizedat the same time, the influence caused by periodic power fading is avoided, the system gain is large, and the system has the characteristics of simple structure, flexible tuning, large bandwidth, multiple functions and the like.

The invention provides a device for automatically testing the performance of an erbium doped fiber amplifier (EDFA). Special software is adopted to automatically control and operate the detection device so as to realize the automatic tests of the gain flatness, transient response and signal-to-noise ratio of the EDFA. Manual intervention is not needed in the whole test process. The automatic test device of the EDFA can largely reduce device setting time, optical path switching time and the test recording and analysis time which are consumed by manual operation, and can further avoid human error caused by manually recording test data. The automatic test mode of the device causes the operation of EDFA performance test to be simple, fast and reliable, which greatly improves the efficiency of the EDFA performance test, and can fully meet the application requirement of enterprises for mass EDFA tests.

A system includes an optical transmitter that outputs an optical signal having a substantially Gaussian waveform and an optical receiver that is optically coupled to the optical transmitter and has an impulse response essentially matching the waveform. The impulse response and waveform preferably match in the time domain. The transmitter and receiver may be average-power-limited, using, for example, an erbium-doped fiber amplifier. To achieve a high signal-to-noise ratio, the waveform may be designed to minimize jitter, sample duration, matching parasitics, and inter-symbol interference (ISI). Such a waveform may be a return-to-zero (RZ) Gaussian or Gaussian-like waveform and may be transmitted in a variety of modulation formats. Further, the system may be used in WDM or TDM systems. A method for characterizing the time domain impulse response of an optical element used in the optical receiver is provided, where the method is optionally optimized using deconvolution and/or cross-correlation techniques.

The present invention discloses a method for measuring the gain and noise coefficients of the erbium-doped optical amplifier; the measurement comprises the following steps that a DFB light source can be input into a filter through a variable optical attenuator; the output end of the filter is connected with an optical power meter to obtain the input power Pin of EDFA; the input end of the EDFA is suspended and the flat region of the ASE spectrum in the EDFA is utilized for obtaining the ASE power PASE which is in the filter band width from the optical power meter; the DFB light resource signal can be emitted into the EDFA through the variable optical attenuator and the signal amplified by the EDFA and the ASE mixing power Pout are obtained from the optical power meter through the filter; by alternating the variable optical attenuator value, the EDFA gain and noise coefficient curves can be calculated and described. The beneficial effect is that the present invention utilizes the flat region of the ASE spectrum in the EDFA to match with a band-pass filter which can fast and accurately calculate EDFA gain and noise coefficients. The test method of the present invention is simple which greatly reduces measurement cost.

The invention discloses a distributed optical fiber temperature and stress sensing device, and belongs to the technical field of optical fiber sensing. The device comprises a pulse laser and the like. The pulse laser is connected with an optical switch and a relay. A semiconductor laser is sequentially connected with an optical isolator A and an optical coupler, the optical coupler is sequentially connected with an acoustic optical modulator, an erbium-doped fiber amplifier and a scrambler, the scrambler is connected with the optical switch, and the optical switch is connected with a circulator A. The other output of the optical coupler is sequentially connected with a polarization controller, an electro-optical modulator and an optical isolator B, and then is connected with the circulator A through sensor fibers. A signal generator is sequentially connected to the acoustic optical modulator, the optical switch, a data collection card, a microwave source and a relay. The microwave source is connected with the electro-optical modulator. The circulator A is connected with the circulator B which is sequentially connected with a fiber Bragg grating, a Raman filter and a photoelectric detector A, and the photoelectric detector A is connected with the data collection card. The circulator B is sequentially connected with a photoelectric detector B and the data collection card. The distributed optical fiber temperature and stress sensing device can achieve simultaneous measurement on temperature and stress in a long-distance and distributed mode.