325 results about "Fiber amplifier" patented technology

The invention provides a high-concentration ytterbium-doped double-clad silicate optical fiber single-frequency amplifier which comprises a single-frequency laser seed source, a double-clad optical fiber pre-amplifier and a high-concentration ytterbium-doped double-clad silicate optical fiber main amplifier which are connected in sequence. The single-mode optical fiber pre-amplifier is used for primarily amplifying the single-frequency laser; the double-clad optical fiber pre-amplifier is used for further amplifying the optical signal output from the single-mode pre-amplifier; and the high-concentration ytterbium-doped double-clad silicate optical fiber main amplifier is used for performing high-power amplification on the signal light amplified by the double-clad optical fiber pre-amplifier and outputting specific high-power narrow-linewidth single-frequency laser. Single-frequency laser seed source low-noise coefficient pre-amplification is achieved through a front multi-stage pre-amplification system, a high-concentration ytterbium-doped double-clad silicate optical fiber is adopted in a final main amplifier, the length of a needed active optical fiber is shortened through provided high gain, the stimulated Brillouin scattering effect is restrained, and the optical fiber is high in gain and high in power consumption. And the output power of the single-frequency narrow-linewidth optical fiber amplifier is improved.

The invention discloses an equivalent self-noise pressure suppression method and device based on a multi-core optical fiber space division multiplexing signal, light emitted by a narrow linewidth laser is split through a first coupler C1, one path of light passes through an acousto-optic modulator AOM to generate a pulse signal, and then the pulse signal passes through a second coupler C2 to generate a pulse signal; the pulse light is divided into two beams of transmission light, the two beams of transmission light are injected into a connected sensing optical fiber through two groups of erbium-doped optical fiber amplifiers (EDFA), two groups of filters, two groups of circulators and a fan-in coupler Fan-in Coupler, and the pulse light is subjected to backward Rayleigh scattering in the sensing optical fiber; based on the dual-channel DAS system, the multi-core optical fiber serves as the sensing optical fiber, three cores and four cores of the multi-core optical fiber are connected in series to form two sensing channels, seven-core space division signals are multiplexed, the equivalent self-noise suppression effect of the seven-core space division signals is analyzed, and the detection capacity of the system for low-frequency weak signals can be improved.

A bismuth-doped (BI) fiber (BIDF) and a bismuth-doped fiber amplifier (BIDFA) are shown and described. The BiDF includes a gain band and an auxiliary band. The gain band has a first center wavelength (λ1) and a first six decibel (6 dB) gain bandwidth. The auxiliary band has a second center wavelength (λ2), λ2<λ1. The system also includes a signal source and a pump source optically coupled to the BiDF. The signal source provides an optical signal at λ1, and the pump source provides pump light at a pump wavelength (λ3).

A 2-micron large-energy solid two-way amplifier based on a single-frequency pulse optical fiber preceding stage can make full use of the small signal amplification capacity of optical fiber laser and the energy extraction capacity of solid laser, and meanwhile the problem that energy is difficult to improve due to the stimulated Brillouin scattering effect in an optical fiber is solved. And high-stability, high-repetition-frequency and large-energy single-frequency pulse laser output can be realized. The all-fiber cascade amplifier comprises an all-fiber cascade amplifier and a solid two-way amplifier, according to the all-fiber cascade amplifier, a continuous narrow-linewidth fiber laser is adopted as a seed source, continuous light is modulated into pulse light through an acousto-optic modulator, and the waveform, the pulse width and the repetition frequency of output pulse laser are adjusted; the modulated pulse light adopts a main oscillation power amplification structure and is preliminarily amplified by a polarization maintaining optical fiber amplifier; the solid-state amplifier adopts a two-way amplification structure, and further high-efficiency amplification is realized through solid-state two-way amplification. The whole laser system is compact in structure, stable, adjustable in parameter and capable of meeting application requirements of different scenes.

The present invention discloses an L-band extended hybrid fiber amplifier, which belongs to the technical field of broadband fiber amplifiers. The system includes a first amplifying module and a second amplifying module; the first amplifying module is used to amplify the signal power of a conventional signal band; the second amplifying module is provided with an erbium-doped fiber, which is used to eliminate the backward ASE generated by the first amplifying module and amplify the signal power of an extended wavelength band. The present invention connects a section of highly-absorbent thulium-doped fiber to the front end of the first amplifying module including an erbium-doped fiber and a wavelength division multiplexer, and utilizes its absorption and emission characteristics in the C+L band to eliminate the backward 1.5μmASE generated in the system, thereby improving the L-band extended band amplification performance. The system of the present invention has a simple structure, high cost-effectiveness, and high efficiency, and at the same time meets the urgent demand for communication capacity of the current optical fiber communication system.

The present invention provides an automatic EDFA signal power control method and apparatus based on real-time ASE compensation. Target output signal power is set; when input optical power fluctuates, a real-time gain is obtained on the basis of the target output signal power and real-time input optical power; corresponding ASE power is obtained by means of the real-time gain, and the target output signal power and the ASE power are added to obtain expected total output power; and when current real-time total output power is adjusted to be the expected total output power, it can be ensured that output signal power in the real-time total output power is locked as the target output signal power while the current ASE power is compatible, thereby ensuring that the output signal power of a fiber amplifier is not affected by the fluctuations of the input optical power.

The invention discloses an equivalent self-noise pressure suppression method based on a dual-channel distributed acoustic sensing system, and the method comprises the steps: carrying out the light splitting of light emitted by a narrow-linewidth laser through a first coupler C1, enabling one path of light to generate a pulse signal through an acoustic optical modulator (AOM), enabling the other path of light to pass through a second coupler C2, and enabling the other path of light to pass through a second coupler C1; the pulse light is divided into two beams of transmission light, the two beams of transmission light are injected into a connected sensing optical fiber through two groups of erbium-doped optical fiber amplifiers (EDFA), two groups of filters, two groups of circulators and a fan-in coupler Fan-in Coupler, and the pulse light is subjected to backward Rayleigh scattering in the sensing optical fiber; according to the invention, based on a dual-channel DAS system, two fiber cores of the multi-core optical fiber are used as sensing optical fibers, and the space division signals of the two cores are multiplexed, so that the performance that the equivalent self-noise pressure drop is 2.54 dB in the frequency band of 100-1000Hz is realized under the condition that the noise correlation coefficient of the dual-core signals is 0.11, and the detection capability of the system on low-frequency weak signals can be improved.

The invention discloses a communication optical axis autonomous correction method based on tracking point nutation, which comprises the following steps: controlling a fine-following fast reflector to scan, monitoring the output power of an erbium-doped fiber amplifier (EDFA) within scanning residence time, searching the position of the maximum power by adopting a sliding window average algorithm, and recording the position; and after scanning for one period, returning to the tracking point with the maximum recorded power, thereby realizing rapid and accurate calibration of the tracking optical axis of the laser communication terminal. According to the invention, a closed loop is formed based on tracking point nutation and a pre-amplification output signal, so that high-precision correction of a camera tracking point is realized, the stability of precise tracking of the system can be improved, and the signal-to-noise ratio received by the laser communication system can also be improved; the traditional receiving optical axis calibration convergence speed and precision are improved; higher real-time performance and automation degree are achieved, relevant data can be acquired and processed in real time, and correction of a receiving optical axis is achieved; the method has wide applicability and expandability, and can be applied to other spacecraft systems needing high-precision tracking control.

The invention discloses a distributed aperture OPA array co-phase system based on a phase measurement chip, and belongs to the field of laser radars, the output end of a laser generating device is connected with an optical fiber beam splitter, output laser is divided into two paths, one path is a main light path, and the other path is a reference light path; after being amplified by the optical fiber amplifier, the main optical path laser is equally divided into N paths by the optical fiber beam splitter, and each path of sub light beam enters the integrated optical chip through the optical fiber-waveguide coupler and is emitted through the OPA module; the reference light path laser enters the phase identification twin chip through the optical fiber-waveguide coupler; and an on-chip interference result is fed back to the phase measurement compensation module, and active measurement and real-time correction are performed on a phase error by adopting an in-waveguide co-phase synthesis technology. According to the invention, a plurality of main laser non-common-path phase error measurement methods are used, and the overall emission aperture, emission power and detection distance of the laser phased array are greatly improved in a multi-aperture cooperative coherence mode.

The invention belongs to the technical field of microwave photon links, and particularly relates to a high-resolution microwave photon frequency measurement system based on real-time Fourier transform. The link comprises a mode-locked laser, a first dispersion compensation module, a second dispersion compensation module, a dual-drive Mach-Zehnder modulator, a Mach-Zehnder modulator, a dispersion optical fiber, a time lens, an erbium-doped optical fiber amplifier, a photoelectric detector and an oscilloscope; the mode-locked laser outputs femtosecond Gaussian light pulses, and the femtosecond Gaussian light pulses are injected into the first dispersion compensation module and then stretched into chirp light pulses; modulating the chirp light pulse through electro-optical modulators which are connected in parallel; the modulated optical signal is subjected to time amplification processing through a dispersion optical fiber, a time lens, a second dispersion compensation module and an erbium-doped optical fiber amplifier in sequence; and the optical signal after time amplification processing is converted into a microwave pulse carrying frequency information of the signal to be detected by a photoelectric detector, and the microwave pulse is observed by an oscilloscope.

The present invention relates to a lidar system including: laser transmitter and receiver systems, the laser transmitter system including: a wavelength-tunable seed laser which emits pulses at selected wavelength points, and switches between wavelengths within a switching time of <200 ns; a fiber amplifier which amplifies the laser pulses up to 200 kW to a transmitter grating; and a transmitter telescope including primary and secondary mirrors. The laser beam is directed from the transmitter grating to the secondary then primary mirrors, and the first transmitter grating is imaged on the primary mirror to minimize laser beam wander thereon. The transmitter grating diffracts and steers the laser beam by wavelength to a surface, to an arbitrary subset of <2000 resolvable footprints along a cross-track direction at a beam pointing angle switching time of <200 ns, such that footprints illuminated by the laser beam on the surface are imaged in 3D.

The invention provides a satellite-borne EDFA on-orbit performance degradation monitoring method and system. The satellite-borne EDFA on-orbit performance degradation monitoring method comprises the steps that a health baseline is preset; closing input light and a first-stage pump of the satellite-borne EDFA; driving a second-stage pump of the satellite-borne EDFA to maintain fixed power output, and recording the working temperature of the second-stage pump; acquiring the monitoring optical power of the second-stage pump and the spontaneous radiation power of the output end of the satellite-borne EDFA; calculating to obtain spontaneous radiation conversion rate; and carrying out satellite-borne EDFA degradation determination. The method has the beneficial effects that the interference of temperature fluctuation on a monitoring result is greatly reduced through the spontaneous radiation conversion rate which is a relative parameter, and the method is adaptive to a complex thermal environment of a satellite; degradation is judged based on a preset health baseline, precise monitoring of the performance state of the satellite-borne EDFA is achieved, and a reliable basis is provided for maintenance. Precise positioning of a degraded part is realized, a fault source is clear, blind maintenance is avoided, and the maintenance efficiency is improved; monitoring can be completed in a second level and can be arranged to be carried out in a communication intermittent period, and normal communication service of the satellite is not affected.

The invention relates to the technical field of multi-network connection, in particular to a Raman optical fiber amplifier remote monitoring system based on multi-network connection. Multiple different network connection modes are achieved through the multiple network connection units, flexible transmission and remote monitoring of data are achieved, a proper network interface can be automatically selected for data transmission according to the current network environment, and the flexibility and stability of network connection are guaranteed. According to the method for packaging the data frames of the different network media on the data link layer, the integrity and effectiveness of the data on the different transmission media are ensured, the system complexity is reduced, and the data transmission efficiency and the system response speed are improved. Especially in a multi-network connection environment, the optimized data link layer processing module can effectively reduce data delay and improve the real-time monitoring capability of the system. Wide area network transmission of data is realized through an MQTT protocol, and safe transmission and real-time monitoring of remote data are ensured.

The invention belongs to the technical field of optical fiber optical frequency transmission, and provides a large-gain low-phase noise bidirectional amplification system and method.The system comprises a first input unit, a second input unit, a forward amplification unit, a reverse amplification unit and a filtering compensation unit; the input end of the forward amplification unit is connected with the first input unit, the input end of the reverse amplification unit is connected with the second input unit, the output ends of the forward amplification unit and the reverse amplification unit are jointly connected to the filtering compensation unit, and the filtering compensation unit is connected with the reverse amplification unit; the forward amplification unit and the reverse amplification unit are respectively used for generating beat frequency signals, and the filtering compensation unit is used for receiving the beat frequency signals and compensating the reverse amplification unit after filtering. The one-way erbium-doped optical fiber amplifiers are connected through the circulator, and a two-way amplification path is constructed. The gain of each one-way erbium-doped fiber amplifier can be independently controlled, the self-excitation effect is effectively avoided, and therefore the gain of the one-way erbium-doped fiber amplifier is improved.

An on-chip integrated microwave photonic phase-coded signal generation system relates to the field of microwave photonic technology. The system includes a laser, a power splitter, a radio frequency (RF) switch, a 90° hybrid coupler (HC), a dual-parallel dual-polarization Mach-Zehnder modulator (DP-DPMZM), a polarization-dependent cascaded phase modulator (PDC-PM), a polarization beam splitter, an erbium-doped fiber amplifier, and a photodetector. In this method, the local oscillator (LO) signal is split into two parts by a power splitter. One part is input into the X-DPMZM to obtain the carrier suppression +1st order sideband of the LO signal. The other part is controlled by an RF switch. When the RF switch is off, the Y-DPMZM only outputs an optical carrier; when the RF switch is on, the Y-DPMZM outputs the -1st order sideband of the LO signal. Then, two orthogonally polarized signals are input into the PDC-PM, which is driven by two independent coding signals. When the amplitude and mode of the coding signals are changed, a binary or quaternary phase-coded signal with a carrier frequency equal to or twice that of the LO signal can be obtained through a photodetector.

The invention discloses a power cable laying stress monitoring device which comprises a stress sensing module, a signal processing module, a data transmission module and a power supply module. The stress sensing module adopts an integrated FBG (Fiber Bragg Grating) sensor array of a flexible mounting belt, and realizes non-damage coating of a cable with the diameter of 3-200mm through an adjustable fastening device; the signal processing module comprises a low-noise optical fiber amplifier and a self-adaptive noise reduction algorithm, and is used for realizing + / -0.5 mu epsilon strain resolution and 5ms dynamic response; the data transmission module adopts a multi-band 4G / 5G communication module and supports AES-256 encryption and edge calculation; and the power supply module adopts a solar energy-lithium iron battery hybrid power supply system to realize 30-day uninterrupted operation. Through collaborative design of the FBG sensing array and the flexible mounting belt, the device solves the problems of poor mounting adaptability, low precision, response lag and the like of a traditional stress monitoring device, and is particularly suitable for real-time stress monitoring in the power cable laying process.

The present application provides a laser generation circuit and an erbium-doped fiber amplifier, relating to the field of optical communication technologies. The jitter signal generation circuit includes: a jitter signal module, an analog signal module, and a clock signal module; the first input end of the jitter signal module is connected to the output end of the analog signal module, the control end of the jitter signal module is connected to the output end of the clock signal module, and the output end of the jitter signal module is used to output a jitter signal. By connecting the jitter signal module to the analog signal module and the clock signal module respectively, the present application can adjust the amplitude of the analog signal output by the analog signal module to achieve the adjustment of the amplitude of the jitter signal, and can adjust the frequency of the clock signal output by the clock signal module to complete the adjustment of the frequency of the jitter signal, so as to be compatible with lasers provided by multiple manufacturers, without adding optical attenuation devices at the output end of the laser, and effectively reducing the cost of preparing the EDFA.

An amplifier operable with an electric drive signal can amplify signal light having a signal wavelength. A laser diode has an active section with input and output facets. The facets are in optical communication with the signal light and are configured to pass the signal light through the laser diode. The active section is configured to generate pump light in response to injection of the electrical drive signal into the active section. The pump light has a pump wavelength different from the signal wavelength. A doped fiber doped with an active dopant is in optical communication with the signal light and is in optical communication with at least a portion of the pump light from the laser diode. The pump wavelength of the pump light is configured to interact with the active dopant of the fiber and thereby amplify the signal light.

The present invention discloses a variable beam divergence angle laser communication terminal and a rapid acquisition method thereof, belonging to the technical field of optical communication devices, including a main telescope, a fine tracking fast steering mirror, a beam splitter, a filter, a beam splitter, a beacon receiving lens group, a beacon detector, a signal transmitting mirror group, a pre-aiming fast steering mirror, a signal receiving mirror group, a receiving fiber amplifier, a multi-core fiber splitter, an optical switch, and a transmitting fiber amplifier, which constitute a signal light transmitting optical path, a beacon light receiving optical path, and a signal light receiving optical path; the signal light transmitting optical path provides a transmitting beam through different mode field fibers, and uses different paths of the transmitting mirror group to shape and variably beam-divergence emit the transmitted light, the signal light receiving optical path is used to collect, shape, couple, and optically amplify the input signal light, and the beacon light receiving optical path is used to collect, shape, converge the input signal light, and use an image positioning detector to position the target light spot. The present invention can improve the efficiency of long-distance acquisition.

The invention relates to the technical field of optical fiber lasers, and provides a middle-infrared band large-range accurate tunable optical fiber laser light source which adopts a large-range tunable 1 [mu] m laser pumping source to obtain ultra-wideband middle-infrared laser output larger than 1000 nm. Comprising a 1 [mu] m wave band tunable pulse seed source, an optical fiber amplifier module, an optical fiber end cap, an end cap coupling device, a hollow-core optical fiber and a small gas cavity, and the 1 [mu] m wave band tunable pulse seed source is a nanosecond pulse laser with the tuning range covering 1024-1080 nm. Based on the direct tuning of the pumping source of the 1 [mu] m wave band, the accurate tuning of the wavelength of the laser of 3 [mu] m-4 [mu] m is directly realized, the tuning is convenient, and a seed source does not need to be added. The pumping source at the 1 [mu] m waveband can obtain high-power laser output more easily, the damage threshold of the hollow-core optical fiber is high, and the mid-infrared output power can be effectively improved. The line width of the gas Raman laser is narrower, and the dispersion of the hollow-core optical fiber is small, so that the output mid-infrared laser has the characteristic of narrow line width.

The invention discloses a multi-core optical fiber amplifier with a large core-to-cladding ratio and a gain method. The multi-core optical fiber amplifier is characterized by comprising a multi-core optical fiber formed by a plurality of independent rare earth-doped fiber cores and a cladding structure located on the outer side of the multi-core optical fiber, the cladding structure is internally provided with at least one layer of low-refractive-index isolation region which is used for remarkably compressing the effective cladding area of pumping propagation and improving the capturing efficiency of the whole pumping energy, and the ratio of the total cross sectional area of the multi-core optical fiber to the effective cladding area is not less than 0.1. The low-refractive-index isolating layer is embedded in a conventional cladding structure, so that a pump light propagation area can be effectively compressed on an optical path, the relative proportion of the fiber core in the cross section is increased, the proportion (CCAR is larger than or equal to 0.1) of the total area of the fiber core to the cladding area is remarkably increased, and therefore the pump capture efficiency is improved.

The invention provides a C + L + S wave band multi-device configuration optimization method and device, and the method comprises the steps: calculating the approximate optimal transmission power of an optical fiber entrance part through employing a local optimal approximate global optimal algorithm; taking the approximate optimal transmitting power as the receiving power of each span section, and recalculating the transmitting signal power at the starting position of the span section by reversely solving a stimulated Raman scattering effect power evolution equation; the gain and gain slope of the optical fiber amplifier are set, so that the signal power which begins to be input in each span segment approaches the transmitting signal power; constructing a loss function based on the generalized signal-to-noise ratio of each wave band; and the gain and the gain slope set after inversion of the stimulated Raman scattering effect are used as initial values, and the gain and the gain slope of the optical fiber amplifier and the channel loss value of the wavelength selection switch are iteratively optimized by using a gradient rising algorithm and taking the loss function improvement as a target. According to the method provided by the invention, only a small amount of iteration is needed, the operation speed is high, and multi-device second-level configuration optimization of the broadband optical transmission system can be realized.

A system for amplifying optical signals includes a first isolator configured to generate a first isolated signal, a first pump, a first coupler for generating a first pumped signal, a first ytterbium doped fiber for receiving the first pumped signal and converting the first pumped signal to a first amplified signal, a second isolator for converting the first amplified signal into a second isolated signal, a second pump, a second coupler for generating a second pumped signal, a second ytterbium doped fiber configured to receive the second pumped signal and convert the second pumped signal into a second amplified signal, and a third isolator configured to receive the second amplified signal and convert the second amplified signal into an amplified optical signal. The first pump and the second pump are configured as co-propagating in-band asymmetrical pump sources for the first and second photons.

The invention discloses an OCC-BOTDA / TGD-OFDR fusion system capable of simultaneously measuring multiple parameters and a working method of the OCC-BOTDA / TGD-OFDR fusion system, and relates to the technical field of optical fiber sensors. The system comprises a narrow linewidth laser, an optical fiber coupler, an electro-optical modulator, an optical fiber circulator, a polarization maintaining fiber bragg grating, a semiconductor optical amplifier, a random scrambler, a delay optical fiber, an erbium-doped optical fiber amplifier, an adjustable grating filter, an optical attenuator, a photoelectric balance detector, a photoelectric detector, a data acquisition card, an arbitrary waveform generator, a direct-current power supply and the like. According to the integrated OCC-BOTDA system and the TGD-OFDR system provided by the invention, simultaneous detection of vibration and temperature / strain along the line can be simultaneously realized through a single sensing optical fiber; the device has the advantages of high fusion degree and low cost, cross aliasing and power competition between pulse light are effectively avoided, and simultaneous measurement of multiple parameters is achieved; the system is high in fusion degree and low in cost.

The invention belongs to the technical field of optical fiber optical frequency transmission, and provides a large-gain bidirectional amplification system and method based on a unidirectional erbium-doped optical fiber amplifier, and the system comprises a first input unit, a second input unit, a forward amplification unit, a reverse amplification unit, and a frequency mixing compensation unit. The input end of the forward amplification unit is connected with the first input unit, the input end of the reverse amplification unit is connected with the second input unit, and the output ends of the forward amplification unit and the reverse amplification unit are jointly connected to the frequency mixing compensation unit; the forward amplification unit and the reverse amplification unit are respectively used for generating beat frequency signals, and the frequency mixing compensation unit is used for receiving the beat frequency signals and compensating the reverse amplification unit after frequency mixing. The gain of each amplifier is independently controlled, so that the self-excitation effect is avoided. In the scheme, the two amplifiers are independently controlled, so that the situation can be effectively avoided, and the stability and the gain performance of the whole amplification system are improved.

The invention discloses an ultrahigh repetition frequency adjustable ultrashort pulse cluster generator which comprises a mode-locked fiber laser, a first fiber coupler, a fiber delay line, a dispersion compensation fiber, a second fiber coupler, a fiber amplifier and an acousto-optic modulator. The first optical fiber coupler, the optical fiber delay line, the dispersion compensation optical fiber, the second optical fiber coupler and the optical fiber amplifier are sequentially connected end to end to form an optical fiber annular cavity, and the annular cavity is used as a frequency increasing device for pulse multiplication; the length difference between the optical fiber annular cavity and a mode-locked cavity in the mode-locked optical fiber laser is adjusted through the optical fiber delay line, and frequency increasing is carried out by using a vernier effect generated by time delay; the ultrahigh repetition frequency ultrashort pulse cluster laser output with adjustable parameters is realized through gain adjustment in the optical fiber annular cavity and synchronous pulse pickup outside the cavity. According to the technical scheme, the structural design is reasonable, the structure is simple, stability is good, sub-pulses are strictly equidistant, parameters are flexible and adjustable, and practicability is good.

The invention provides an optical feedback resonance enhanced forward Brillouin demodulation structure, which comprises a tunable laser, a first polarization controller, an erbium-doped optical fiber amplifier, an optical coupler, an optical isolator, a forward Brillouin gain optical fiber, a band-pass filter and a photoelectric detector, a second polarization controller; and a spectrum analyzer. The first polarization controller is connected with a port a of the optical coupler, a port b of the optical coupler is connected with an input end of the erbium-doped optical fiber amplifier, an output end of the erbium-doped optical fiber amplifier is connected with the optical isolator, the optical isolator is connected with the band-pass filter, the band-pass filter is connected with the forward Brillouin gain optical fiber, and the optical fiber is fed back to a port c of the coupler through the second polarization controller. The output power of the erbium-doped optical fiber amplifier is controlled, and the polarization states of the pump light and the feedback laser are controlled by the first polarization controller and the second polarization controller, so that the forward Brillouin effect is amplified.

The utility model belongs to the field of distributed optical fiber sensing, and particularly relates to a compact high-signal-to-noise-ratio dark pulse BOTDR (Brillouin Optical Time Domain Reflectometer) system for engineering, which comprises a laser, and the output end of the laser is connected with a first photoelectric coupler which is used for dividing light emitted by the laser into upper light and lower light. The dark pulse modulation system module is arranged, descending pump light is equivalent to a dark pulse through modulation, a computer controls dark pulse time slots so as to change pump pulse characteristics, a corresponding demodulation method is adopted in rear-end data processing, Brillouin frequency shift along a sensing optical fiber is obtained, and the Brillouin frequency shift is converted into Brillouin frequency shift along the sensing optical fiber. The lower limit of the spatial resolution of the method is equal to the fall time of the modulation system, and the spatial resolution can be greatly improved under the condition of improving the signal-to-noise ratio. In addition, due to narrow pulse width and low energy of the traditional bright pulse, an erbium-doped fiber amplifier (EDFA) is generally needed for signal amplification. Dark pulses are close to continuous light in most cases, and EDFA is not needed, so that the system design is simplified, and the cost is reduced.

The present invention discloses a double-clad fiber pump return filter, which relates to the technical field of fiber amplifiers and fiber lasers. The filter includes an input fiber collimator, a triangular prism, a supporting glass tube, a filter, an output fiber collimator, and a bridge glass tube; the supporting glass tube is fixedly installed in the middle position inside the bridge glass tube, and the triangular prism and the filter are respectively fixedly installed at both ends of the supporting glass tube; the input fiber collimator and the output fiber collimator are respectively inserted into the two ends of the bridge glass tube and fixed after optical debugging; the present invention uses the dispersion effect to cause the transmission angles of the pump light and signal light transmitted on the same optical fiber to deviate, and then the residual pump light can be returned to the original path while maintaining high return loss of the signal light, effectively improving the utilization efficiency of the pump light and having positive significance for improving the conversion rate of fiber amplifiers and fiber lasers.

A pulse light generation device 1 comprises: an oscillator 2 for oscillating an ultrashort pulse light L; a stretcher fiber 7 for widening the time width of the ultrashort pulse light L; a fiber amplifier 8 for amplifying the ultrashort pulse light L the time width of which has been widened by the stretcher fiber 7; and a compressor 9 for compressing the time width of the ultrashort pulse light L which has been amplified by the fiber amplifier 8. The stretcher fiber 7 is configured by combining a first fiber 71 for widening the time width of the ultrashort pulse light L with a first characteristic, and a second fiber 72 for widening the time width of the ultrashort pulse light L with a second characteristic which is different from the first characteristic.