80 results about "Optical fiber amplifiers" patented technology

The invention discloses a signal-to-noise ratio improvement method based on a multi-core optical fiber 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; based on a dual-channel DAS system, a multi-core optical fiber is used as a 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 pressure suppression effect of the seven-core space division signals is analyzed, after noise correlation is removed through a time domain dislocation-frequency domain phase shift method, the signal-to-noise ratio gain can be increased to 8.65 dB, and the signal-to-noise ratio gain can be increased to 8.65 dB. And the detection capability of the system on low-frequency weak signals can be improved.

The utility model discloses a distributed sound wave sensing system for multi-frequency pulse modulation, and relates to the technical field of distributed sound wave sensing. The system comprises a narrow linewidth laser, an optical fiber coupler, a polarization-maintaining optical isolator, an acousto-optic modulator, a polarization-maintaining delay optical fiber, an erbium-doped optical fiber amplifier, a polarization-maintaining dense wavelength division multiplexer, an optical fiber circulator, an optical fiber Bragg grating, a piezoelectric transducer, a polarization controller, a photoelectric balance detector, a data acquisition card, an arbitrary waveform generator and the like. According to the utility model, the multi-frequency delay ring is utilized to carry out multi-frequency modulation, the frequency number of light waves is increased along with the circulation times of the light waves in the delay ring, and under the condition that the utilization of a large-bandwidth electro-optical modulator is not increased, the flexible modulation of the frequency is realized by utilizing a low-bandwidth acousto-optical modulator without being influenced by carrier frequency and sidebands of each order; the low-bandwidth acousto-optic modulator is used for frequency modulation in the multi-frequency delay ring, and compared with an electro-optical modulation or multi-acousto-optic / multi-light source modulation scheme, the modulation cost is effectively saved.

The invention provides an optical path structure for improving the fineness of interference fringes of a Fabry-Perot sensor, which belongs to the technical field of optical fiber sensing and comprises a laser, a 2 * 1 optical fiber combiner, an optical fiber circulator, the Fabry-Perot sensor, a 1 * 2 optical fiber splitter, a photoelectric detector and an erbium-doped optical fiber amplifier. The laser generates a stable light source, and an optical signal enters the Fabry-Perot sensor through the 2 * 1 optical fiber combiner and the optical fiber circulator to generate interference fringes. Then, the 1 * 2 optical fiber beam splitter divides the optical signal into two parts, one part is transmitted to a photoelectric detector for signal detection, and the other part enters an erbium-doped optical fiber amplifier for amplification and is circulated back to the system through a feedback optical path. The optical path structure realizes multi-beam interference by introducing an optical path design of signal amplification and multiple feedback, the fineness of interference fringes is remarkably improved, and the sensitivity of the Fabry-Perot sensor in displacement and phase detection is further improved.

The invention belongs to the technical field of microwave photons and optical communication, particularly relates to a tunable narrow-linewidth microwave photonic oscillator based on forward Brillouin scattering, and solves the technical problems that an existing microwave photon generation method is complex in structure and poor in tunability, and linewidth cannot meet requirements. The erbium-doped optical fiber amplifier is connected to a first optical fiber coupler through a filter, two output ends of the first optical fiber coupler are respectively connected to a third optical fiber coupler and a second optical fiber coupler, and two output ends of the second optical fiber coupler are respectively connected to a spectrograph and are sequentially connected with a photoelectric detector and a spectrum analyzer; two output ends of the third optical fiber coupler are respectively connected to an input end c of a fourth optical fiber coupler through a first polarization controller and a first single-mode optical fiber and connected to an input end b of the fourth optical fiber coupler through a second polarization controller and a second single-mode optical fiber in sequence; and the fourth optical fiber coupler is connected to an erbium-doped optical fiber amplifier through a third polarization controller.

The invention discloses an optical time domain reflectometer based on ring structure modulation and a working method thereof, and relates to the technical field of optics. The optical time domain reflectometer comprises a laser, an optical fiber coupler, a semiconductor optical amplifier, an acoustic optical modulator, an optical isolator, a delay optical fiber, an erbium-doped optical fiber amplifier, a dense wavelength division multiplexer, a circulator, a Raman laser, piezoelectric ceramics, an arbitrary function generator, an arbitrary waveform generator, a polarization controller, a photoelectric balance detector, a data acquisition card, a computer and the like. Multi-frequency modulation is carried out based on an annular structure, the multi-frequency modulation range is only limited by the bandwidth of a detector and the sampling rate of an acquisition card, a pulse sequence is generated through modulation of the optical annular structure, dependence on the bandwidth performance of a microwave signal source and a modulator is reduced, and the bandwidth is improved; and by injecting the Raman light, the sensing distance is also increased, the equipment cost is effectively controlled, and meanwhile, a new scheme is provided for time sequence pulse sequence modulation.

The application relates to a method of an electric field sensor based on an optoelectronic oscillator, belonging to the field of optical devices and optical fiber sensing. The device comprises a laser source, a polarization controller, a phase modulator, a fiber Bragg grating with an acrylate glue cavity, a stacked piezoelectric ceramic, an electric field generator, an erbium-doped fiber amplifier, a photodetector, a power divider and an electric amplifier. The stacked piezoelectric ceramic is combined with the fiber Bragg grating with the acrylate glue cavity as a sensing head, the wavelength change of the fiber Bragg grating with the acrylate glue cavity caused by the piezoelectric effect is mapped to the frequency change of the microwave signal generated by the optoelectronic oscillator, and the electric field change value can be obtained by monitoring the microwave signal of the optoelectronic oscillator. In the loop of the optoelectronic oscillator, the electric spectrum analysis technology is used for demodulation, and high-speed and high-resolution electric field measurement can be obtained. The method has the advantages of simple structure, high measurement sensitivity and easy practicability.

A device comprises a quantum random number generator, and further comprises following device parts: a first SPAD diode, a second SPAD diode, an optical fiber which optically couples the first SPAD diode and the second SPAD diode to one another, an amplifier and / or filter, an analog-to-digital converter, a comparator, a time-to-digital converter, and an entropy extraction device converting output values of the time-to-digital converter into first and second values and generates random bits therefrom.

The present invention is applicable to the field of pulsed laser technology and provides a pulsed laser modulation system. The system includes: a laser seed source for emitting a laser signal; a polarization-maintaining circulator having an incident end, a first emission end, and a second emission end, with the laser seed source and the incident end of the polarization-maintaining circulator being located on the same optical path; a fiber preamplifier and a laser pulse stretcher, with the first emission end, the fiber preamplifier, and the laser pulse stretcher being sequentially arranged on the same optical path; and an acousto-optic modulator and a fiber amplifier, with the second emission end, the acousto-optic modulator, and the fiber amplifier being sequentially arranged on the same optical path. The present invention proposes a design scheme for a pulsed laser modulation device that integrates stretching, preamplification, and frequency selection. By using this scheme, a low-repetition-rate pulsed laser output with a compact structure, good stability, and a high signal-to-noise ratio can be achieved.

The invention provides a coherent optical time domain reflection sensing device and a method thereof, and relates to the technical field of distributed optical fiber acoustic wave detection. The device comprises a light source, a 1 * 2 coupler, a control and signal processing unit, an arbitrary waveform generator, a double-path parallel Mach-Zehnder electro-optical modulator, a reference arm optical fiber, an erbium-doped optical fiber amplifier, an optical filter, a circulator, a sensing optical fiber, a 90-degree optical mixer, a photoelectric detector and a data acquisition card. A detection light sequence containing positive and negative frequency shift light pulse sequences is injected into a sensing optical fiber, returned signal light which carries light phase information of each detection point and has superposed frequencies is mixed with local reference light, signal separation is achieved after the signal light is multiplied by complex factors corresponding to each frequency shift pulse and integration of a periodic integral multiple window is carried out, and the detection point light phase information is obtained. And optical phase information demodulation is carried out, and then fusion of detection results of optical signals of various frequencies is carried out, so that high-sampling-rate sensing of acoustic vibration is realized.

The invention provides a method for generating high-peak-power intermediate infrared ultrafast laser based on pulse / continuous wave system parametric conversion. Comprising a pumping source 1 which is used for providing mu J-level energy and 10ps-level pulse width near-infrared pulse laser. Pump light is focused and subjected to path adjustment through the high reflectors 2, 3 and 5 and the lens 4, the pump light and signal light are combined through the dichroscope 15, and optical parametric conversion is carried out through the nonlinear crystal 16. Comprising a signal source 6 which is used for providing near-infrared continuous waves, signal light power and polarization direction are accurately regulated and controlled through an erbium-doped optical fiber amplifier 7, an attenuator 8, a polarization maintaining optical fiber circulator 9, a collimator 10 and a half-wave plate 11, and focusing and path adjustment are carried out through a lens 12 and high reflectors 13 and 14. Comprising a dichroscope 17 and long-pass filters 18 and 19 and is used for filtering out mid-infrared laser.

The invention discloses an optical fiber collimator, isolator and circulator in an orbital angular momentum mode, and belongs to the field of optoelectronic communication devices. Based on a special optical fiber collimator design scheme, the OAM optical fiber collimator which is simple in structure and excellent in performance is realized. On the basis of an OAM optical fiber collimator, an isolation core and an annular core are combined, and an OAM optical fiber isolator and an OAM optical fiber circulator which are low in cost, low in processing complexity, small in occupied size and excellent in performance are respectively realized through a special packaging process. The isolator and the circulator have the characteristics of low insertion loss, high isolation degree, high quality of a transmitted OAM mode and the like. The OAM optical fiber collimator, isolator and circulator realized by the invention can replace free space optical devices with consistent functions in systems such as an OAM mode optical fiber communication system, an OAM optical fiber amplifier and the like. The cost of the mode division multiplexing optical fiber communication system based on the OAM mode is reduced, the flexibility of the system is improved, and the method has important significance for promoting the practicability and miniaturization of the optical fiber communication system.

The invention provides a pure solid-state scanning type absolute ranging system and a target detection method thereof. The pure solid-state scanning type absolute ranging system comprises a light source, an optical fiber amplifier, a spatial light polarization controller, a pure solid-state light beam scanning and interference module, a spectrum acquisition module and a control and calculation module, the pure solid-state light beam scanning and interference module is based on the wavefront regulation and control principle, dynamic modulation of incident light wavefront is achieved by loading a two-dimensional programmable grating phase on a spatial light modulator, and therefore light beams are controlled to complete pure solid-state scanning in space according to a set path. When a scanning light beam irradiates a target pyramid, a strong return light signal is generated, the spectrum acquisition module captures two-dimensional spectrum resolution and two-dimensional spectrum image imaging of an interference signal, and the control and calculation module performs high-precision distance calculation of a target absolute distance through phase extraction and interference fringe analysis based on a dispersion interference principle.

According to the laser detection system for detecting the health condition of the underground comprehensive pipe gallery provided by the invention, the narrow-linewidth high-stable-frequency laser is combined with a balance detection technology, so that the capability of detecting weak ultrasonic signals of a pipe wall is remarkably improved, and environmental common-mode noise is effectively inhibited; the attenuation problem of laser in long-distance transmission is overcome by using an erbium-doped optical fiber amplifier light amplification technology, and continuous health monitoring of a several-kilometer-level pipe gallery is realized; through cooperative work of the 180-degree mixer and the signal acquisition system, high-precision analysis of phase change of reflected light is realized, and the position of a damage or disturbance source can be accurately positioned without contact with a pipe wall; furthermore, through feature analysis of the ultrasonic frequency spectrum, the system can sensitively capture early hidden defects such as internal cracks and corrosion of the pipe gallery structure and threats such as external construction excavation, and reliable data support is provided for health assessment and risk early warning of the pipe gallery structure.

A photonic crystal fiber (10) comprises: a core region (11) having a rare earth element added thereto; and a cladding region (12) including a plurality of refractive index reduction parts (13) provided around the core region (11). Each of the refractive index reduction parts (13) is formed of a glass rod having a refractive index lower than that of the cladding region (11) or a hole. The mode field diameter of the basic mode at a wavelength of 1.55 µm is not less than 16.4 µm.

The invention provides a gain flattening filter, an optical fiber amplifier and a wavelength division multiplexing communication system, relates to the technical field of optical communication, and is used for realizing gain flattening filtering. The gain flattening filter comprises N first optical fibers in a first fiber core mode, N second optical fibers in the first fiber core mode, M second optical fibers in the second fiber core mode and N third optical fibers in the first fiber core mode, the second optical fiber comprises a plurality of cascaded fiber bragg gratings, and the plurality of cascaded fiber bragg gratings are used for coupling at least one first fiber core mode in the N first fiber core modes to at least one second fiber core mode in the M second fiber core modes, the mode order of at least one second fiber core mode in the M second fiber core modes is higher than the mode order of at least one first fiber core mode in the N first fiber core modes; the first optical fiber, the second optical fiber and the third optical fiber are sequentially connected. According to the scheme, the gain flattening of the optical signal can be realized through the gain flattening filter with a simple structure.

This invention discloses a high-efficiency nonlinear optical frequency converter based on high-power continuous optical transmission using quartz micro / nano fiber, comprising a wavelength-tunable laser, an optical fiber amplifier, a quartz micro / nano fiber, a sealed cavity, and an optical fiber low-pass filter; the quartz micro / nano fiber includes a first untapered portion, a second untapered portion, a first tapered transition region, a second tapered transition region, and a waist region, transmitting an optical field TE. 01 The mode cutoff method precisely controls the waist diameter of micro / nano fiber and accurately tunes the input light wavelength. The nonlinear light frequency conversion process excited by high-power continuous light transmitted in quartz micro / nano fiber satisfies perfect phase matching. The fundamental mode of the input light and the higher-order mode fields of the harmonic signal light have high overlap in the waveguide mode, which can efficiently generate continuous second and third harmonic signal light. The device has high stability, high efficiency, and low cost, and can be applied in fiber lasers, all-optical signal processing, fiber optic sensing and other fields.

The invention discloses an optical fiber sensing integrated system based on a phase coding optical carrier. The optical fiber sensing integrated system is composed of an optical path detection part and a circuit demodulation part. The whole system is composed of a continuous wave laser, an optical fiber coupler, an acousto-optic modulator, a multi-phase coding generator, a polarization controller, an intensity modulator, a communication signal generator, an optical fiber amplifier, a dispersion compensation module, an optical fiber circulator, an optical fiber, a photoelectric detector, a data acquisition module, a data processing module and a high-sensitivity coherent receiver. The system is simple, only one single-wavelength laser is adopted as a light source, and the system is highly integrated, simple, easy to implement and easy to adjust; the whole system adopts a common time frequency integrated signal to realize a communication sensing integrated system, and has high spectrum efficiency; the whole system can flexibly adjust the system communication and distributed sound wave sensing performance only by adjusting the carrier signal power ratio, the flexibility of the system is improved, and more application scenes are covered.

The invention discloses a microwave photon frequency hopping signal generation method based on double optical combs, and relates to the technical field of microwaves and the field of optical communication. The method is shown in a figure 1 in the specification, and comprises a laser, an optical coupler, a signal source, a radio frequency source, a Mach-Zehnder modulator, a double-parallel Mach-Zehnder modulator, an optical band-pass filter, an optical switch, an erbium-doped optical fiber amplifier, a double-parallel Mach-Zehnder modulator, a 90-degree bridge, a photoelectric detector and a transmitting antenna. According to the invention, an electro-optical modulator is utilized to generate an optical frequency comb and modulate a frequency hopping local oscillator signal in an upper path, a double-parallel Mach-Zehnder modulator is utilized to shift frequency in a lower branch, then the electro-optical modulator is utilized to generate the optical frequency comb, the upper path and the lower path are combined, channels where different optical frequency combs are located are separated through an optical filter, different channels are selected through an optical switch, and the frequency hopping local oscillator signal is modulated. And finally, a frequency hopping signal is obtained through a photoelectric detector. According to the invention, large-bandwidth and high-precision frequency hopping signal generation can be realized, and the requirement on an optical filter is reduced.

The invention relates to a high-nonlinearity photonic crystal fiber and an optical fiber amplifier, the fiber comprises a core layer and cladding layers, the cladding layers comprise an inner cladding layer and an outer cladding layer, the high-nonlinearity photonic crystal fiber is characterized in that the refractive index profile of the core layer is in alpha power exponential function distribution, the distribution index alpha of the core layer is 2.0-8.0, the radius a of the core layer is 0.8-2 microns, and the refractive index alpha of the core layer is 2.0-8.0. The maximum relative refractive index difference delta 1max is 2-5%, the inner cladding layer is an air hole dot matrix inner cladding layer, the outer cladding layer is arranged outside the inner cladding layer, and the outer cladding layer is a pure silicon dioxide glass outer cladding layer. According to the invention, the large refractive index difference between the high refractive index core layer and the low refractive index air hole cladding is beneficial to improving the binding ability of the fiber core to light on one hand and promoting the reduction of the effective mode field area of the optical fiber on the other hand, thereby improving the nonlinear performance. The gradient high-nonlinearity photonic crystal fiber provided by the invention is mainly used in the field of communication and can be used as an optical gain medium of an optical fiber amplifier, and a corresponding device has the advantages of low noise, high gain and the like.

1. Name of the designed product: optical fiber amplifier. 2. Use of the designed product: power amplification and output of inputted laser of specific wavelength and power range. 3. Design points of the designed product: combination of shape and pattern. 4. Picture or photo best indicating the design points: perspective view.

The utility model relates to a two-way polarization-maintaining amplification laser light source, which comprises a seed source, a first isolator, a polarization splitting prism, an optical path separation device, an optical filter, a double-optical-fiber collimator, a pumping source, a non-polarization-maintaining single-mode gain optical fiber, a single-optical-fiber collimator, a polarization rotator, a reflection device and a second isolator. The polarization-maintaining optical fiber amplifier can solve the problems of high cost and secondary pulse of a polarization-maintaining optical fiber amplifier in the prior art.

The invention discloses an optical frequency domain reflection distributed measurement system based on complex beat frequency signal reconstruction and an application method thereof. The system comprises a linear sweep frequency laser, a first optical coupler, an erbium-doped optical fiber amplifier, an optical circulator, an optical waveguide to be measured, a polarization controller, a second optical coupler, a photoelectric detector and a data acquisition and processing module. According to the invention, the reconstruction of the complex beat frequency signal can be realized without introducing a new photoelectric device, the coherent fading and cross interference noise in the low-frequency range of the OFDR can be effectively suppressed, the interference of positive and negative spectrum aliasing noise can be avoided, and the measured signal-to-noise ratio and the measurement precision can be obviously improved without increasing the system hardware complexity.

This application provides a Raman fiber amplifier and an optical communication system, relating to the field of optical communication technology, to address the increased cost caused by the need to develop and use two different Raman fiber amplifiers. The Raman fiber amplifier includes a first port, an optical coupler, a pump laser, a second port, a third port, and a mode control device. The first port and the pump laser are both connected to the optical coupler. The pump laser generates pump light that is transmitted to the optical coupler, which then transmits the pump light to the first port. The second port, the third port, and the optical coupler are all connected to the mode control device. The mode control device controls unidirectional conduction between the optical coupler and the second port in the direction toward the optical coupler, and controls unidirectional conduction between the optical coupler and the third port in the direction toward the third port. This Raman fiber amplifier can be applied to optical communication systems.

The utility model provides a double-color optical fiber amplifier, which comprises an outer shell, a display, a control key and a display lamp signal, a PCB (printed circuit board) arranged in the outer shell is electrically connected with the parts and is also electrically connected with an LED (light-emitting diode) receiving and transmitting inner module, a first inner detection unit and a second inner detection unit, and the first inner detection unit and the second inner detection unit are electrically connected with the PCB. Through the combination of the control keys, various parameters can be set and detection modes can be adjusted, so that an accurate detection result can be quickly obtained, the problems of signal confusion and complicated operation in a traditional detection method are solved, and the purposes of simplicity in operation, convenience and practicability are achieved.

The present disclosure is an optical fiber amplifier including: an amplification optical fiber doped with a rare earth element, in which a pump light combiner for injecting multimode pump light into a cladding region of the amplification optical fiber is connected to an input end or an output end of the amplification optical fiber, and a reflective device for reflecting the pump light and transmitting signal light is connected to an end part, of the amplification optical fiber, to which the pump light combiner is not connected.

The invention provides a system for widening a bismuth-doped optical fiber fluorescence range based on short wave pumping, the system comprises a laser pumping source, a bismuth-doped optical fiber, a spectrometer, a wavelength division multiplexer and an optical isolator, the laser pumping source is 900-1000nm, and a bismuth-doped optical fiber core takes quartz-based glass doped with a bismuth element and one or more elements of phosphorus, germanium and aluminum as a main body. By optimizing optical fiber spectrum excitation conditions, under high-energy short-wavelength pumping, various bismuth active centers are effectively excited, 1000-1800 nm ultra-wideband near-infrared fluorescence output is achieved, and the 6dB bandwidth can reach 150 nm or above. The method has wide application prospects in the fields of ultra-wideband optical fiber amplifiers, wideband tunable lasers, super-continuum spectrum light sources and the like.

The invention relates to the technical field of optical fiber communication and optical fiber sensing, and particularly provides a small-signal-input multi-wavelength optical fiber amplifier which comprises a filtering assembly, a first-stage amplification optical path and a second-stage amplification optical path. The first-stage amplification light path comprises a first optical fiber isolator, a first wavelength division multiplexer, a first-section erbium optical fiber, a second wavelength division multiplexer and a second optical fiber isolator which are connected in sequence, and the second-stage amplification light path comprises a third wavelength division multiplexer, a second-section erbium optical fiber and a third optical fiber isolator which are connected in sequence. The input end of the filtering assembly is connected with the second optical fiber isolator, the output end of the filtering assembly is connected with the third wavelength division multiplexer, a plurality of wavelength division multiplexers are used for forming the filtering structure, signal light of different wavelengths can be amplified, and attenuation of optical signals caused by using an optical fiber coupler and a filter is avoided; meanwhile, one pump laser is used for two erbium optical fibers, so that the power consumption and the size are reduced.

The invention discloses a communication and remote sensing integrated forest fire prevention laser radar system and a use method thereof. The laser radar comprises a continuous light laser, a beam splitter, an analog signal generator, an electro-optical modulator, a pulse optical fiber amplifier, a circulator, a variable-focus transceiver telescope, a coupler, an acousto-optic frequency shifter, a balance detector, a receiving telescope, an avalanche diode detector, a multi-channel data acquisition system and a computer. According to the invention, the electro-optical modulator is adopted to modulate a high-frequency pulse signal, and an atmospheric detection signal and a communication signal can be generated; signal frequency shift is realized by adopting an acousto-optic frequency shifter, and wind field direction information is obtained; a variable-focus transceiving telescope, a receiving telescope and laser radars are adopted for networking, and optical information transmission between the laser radars is achieved. The system can realize information communication of the laser radar in a non-signal area, and is especially suitable for being applied to the field of forest fire prevention based on the advantages of multi-parameter detection, high resolution and wide coverage of the laser radar.

The present application provides an optical fiber amplifier, comprising: a gain optical path, configured to amplify signal light; a first filter, configured to filter backward spontaneous emission light generated by the amplification of the signal light by the gain optical path, and retain auxiliary light that meets a preset requirement; and a coupler, configured to combine the auxiliary light with new signal light to be amplified by the gain optical path, so as to enhance population inversion generated when the combined new signal light is amplified by the gain optical path.

The application discloses a low-noise high-gain 1550nm single-frequency optical fiber amplifier, which comprises an input end cap, a tap isolator, a preamplifier and a power amplifier; the input end cap is connected with one end of the tap isolator and is used for monitoring the power and spectrum of a signal and preventing the preamplifier from returning light in the 1.5mu m wave band; the other end of the tap isolator is connected with the preamplifier; the preamplifier is connected with one end of a first tap band-pass isolator in sequence and is used for filtering out broadband ASE and monitoring the preamplifier output through the first tap band-pass isolator; the other end of the first tap band-pass isolator is connected with the power amplifier; compared with the prior art, the single-pump double-stage double-channel master oscillator power amplifier structure is adopted in the application, the tap band-pass isolator and the polarization beam splitter are combined to replace the conventional Faraday reflector in the power amplification stage, and the spectral signal-to-noise ratio of the output signal light is effectively improved.