50results about How to "Gain flat" patented technology

The invention relates to a double-ring feedback gain flattening erbium-doped optical fiber amplifier and belongs to the technical field of optical fiber amplifiers. The double-ring feedback gain flattening erbium-doped optical fiber amplifier structurally comprises a basic amplification optical path, a first three-port circulator (13), an optical fiber loop mirror (14), a second three-port circulator (15), a grating (16), a fourth optoisolator (17), an optical attenuator (18), a photoelectric converter (19), a PID control circuit (20) and a voltage-controlled current source (21), wherein the basic amplification optical path is composed of a signal source (1), a first optoisolator (2), a first coupler (3), a first wavelength division multiplexer (4), a first erbium-doped optical fiber (5), a second wavelength division multiplexer (6), a second optoisolator (7), a gain flattening filter (8), a second coupler (9), a second erbium-doped optical fiber (10), a third optoisolator (11), a first optical splitter (12) and a pumping module (22). The double-ring feedback gain flattening erbium-doped optical fiber amplifier has the advantages of being flat in gain, high in responding speed, controllable in output power and the like.

An ultra-wide-band low-noise amplifier adopting the inductance compensation technology comprises an amplification unit, a feedback unit and an output matching unit, wherein the output end of the amplification unit is directly connected with the input end of the feedback unit and the output matching unit, and the output end of the feedback unit is connected with the input end of the amplification unit. The amplification unit adopts a self-biased phase inverter structure, the bias resistance is large so that the input resistance of the amplification unit can be very large, and input matching is not affected. According to the feedback unit, a source follower drives a medium resistor to finish input matching. The output matching unit adopts a source follower structure and can keep good output matching within a wide frequency band. The amplification unit adopts the split load inductance compensation technology, and an inductor is connected with the grid end of an MOS pipe in series. The 3dB band width of the low-noise amplifier is largely improved, the low-noise amplifier can keep smooth grains within a wide frequency band, and meanwhile the compensating inductance has a certain inhibiting effect on noise.

An optical communication system according to the invention comprises: a transmitting station 11; an optical transmission line 12 for transmitting an optical signal sent from the transmitting station 11; a receiving station 13 for receiving the optical signal outputted from the optical transmission line 12; a repeater station 14 provided at one point or more in the optical transmission line 12; and pump light sources 21 provided in at least two of the stations 11, 13, 14, for supplying pump light to the optical transmission line 12, wherein the pump light has two types or more of wavelength. It is possible to obtain a substantially flat gain as a function of wavelength in the whole optical communication system since the pump lights with different wavelengths are supplied from a plurality of points in the optical transmission line 12 and an optical signal is amplified with various Raman gain coefficients.

The invention discloses a filtering patch antenna without additional arrangement of filter circuit, and an adjustment method thereof. The antenna comprises a bottom metal reflection floor, an intermediate feed patch and a top parasitic patch. The two sides of the feed patch are each provided with a short circuit probe, the feed patch is provided with a U-shaped groove, a short circuit probe is arranged in front of an opening of the U-shaped groove, and a feed point is arranged behind a closing position of the U-shaped groove. The top parasitic patch is fixed right above the feed patch at an interval of a certain height. According to the invention, the filtering patch antenna itself has a filtering function and realizes a bandpass filtering characteristic without additional arrangement of the filter circuit. The passband edge is deep, the sideband suppression is obvious, the frequency selectivity is good, adjacent frequency interference can be inhibited, the bandpass filtering characteristic and an antenna radiation function are integrated together, the plat grain at a passband position is quite high, and the filtering patch antenna is applied to such mobile communication scenes as WCDMA, 4G-LTE, WLAN and the like.

The invention discloses a flat-gain broadband neodymium glass amplifier based on birefringence filtering. The flat-gain broadband neodymium glass amplifier comprises a polarization controller, a birefringence filtering spectrum equalizer and a neodymium glass amplifier. The polarization controller is composed of a quarter wave plate and a half-wave plate which are successively arranged in an optical path. The birefringence filtering spectrum equalizer is composed of a polarizer, a phase delayer and a polarization analyzer, wherein the polarizer, the phase delayer and the polarization analyzer are successively arranged in the optical path. The polarization passing direction of the polarizer is same with that of the polarization analyzer. The phase delayer is fixed on a rotating adjusting frame. The neodymium glass amplifier comprises neodymium glass and a pumping light source. According to the flat-gain broadband neodymium glass amplifier, the neodymium glass broadband laser amplifier with the flat gain is constructed based on the birefringence filtering spectrum equalizer and the neodymium glass amplifier. Particularly, spectrum transmittance is adjusted by means of birefringence spectrum filtering technology; counter compensation is performed on the gain spectrum of a traditional neodymium glass amplifier; and finally a flat gain spectral line in a relatively wide spectrum range is realized.

The invention discloses a few-mode erbium-doped optical fiber. A fiber core of the few-mode erbium-doped optical fiber comprises a first layer, a second layer and a third layer from inside to outside,the first layer is round, the second layer is in a first annular shape, the third layer is in a second annular shape, and the refractive index of the second layer is larger than the refractive indexof the first layer and larger than the refractive index of the third layer. The erbium ion doping concentration of the second layer is less than the erbium ion doping concentration of the first layerand less than the erbium ion doping concentration of the third layer. According to the scheme provided by the invention, gain flatness among transmission modes can be realized only through single-fundamental-mode pumping, and weak coupling transmission of a to-be-amplified signal in the few-mode erbium-doped fiber is realized at the same time.

The invention discloses an optical fiber communication transmission system and method applied to multi-wavelength pumping high-order bidirectional Raman amplification, which are applied to an ultra-long span optical fiber communication system and a common optical fiber communication system, can reduce one pump light in a multi-wavelength pumped bidirectional high-order Raman amplifier, and solve the problems of high relative intensity noise and low gain efficiency in a current multi-wavelength pumped high-order Raman amplification process and meanwhile reduce the system cost. A pump light closest to a signal light wavelength is reduced on a forward high-order Raman amplifier; and a reflection-type fiber grating filter is inserted respectively at an output end of the forward high-order Raman amplifier and an input end of a backward high-order Raman amplifier, and the central wavelength of the fiber grating is the wavelength of the pump light that has been reduced. The method of the invention can reduce the number of pump lights of the high-order Raman amplifier and reduce cost, and at the same time, reduce the relative intensity noise of the high-order Raman amplifier, greatly improve the backward gain and forward gain efficiency of the high-order Raman amplifier, and extend the transmission distance of a bidirectional high-order Raman fiber communication system.

The invention discloses a broadband filtering antenna based on grid slotted patches. The antenna comprises a first dielectric plate, a second dielectric plate and a third dielectric plate which are sequentially arranged from bottom to top; a first air layer exists between the first dielectric plate and the second dielectric plate; a second air layer exists between the second dielectric plate and the third dielectric plate; a third copper-clad layer is formed on the upper surface of the third dielectric plate, and a grid slotted patch is arranged on the third copper-clad layer; a second copper-clad layer is formed on the upper surface of the second dielectric plate, and a rectangular patch is arranged on the second copper-clad layer; the upper surface of the first dielectric plate is provided with a grounding plate, the lower surface of the first dielectric plate is provided with a first copper-clad layer, the grounding plate is provided with a coupling aperture, the first copper-clad layer is provided with first, second and third half-wavelength U-shaped resonators and a coupling feeder line, and the upper and lower surfaces of the first dielectric plate are provided with input ports. The four-order filtering antenna is comprehensively designed on the basis of a filter and stably works within the range of 2.27 GHz to 2.57 GHz, S11 is smaller than -10 dB, the gain is kept about7.5 dBi, and the whole antenna is simple and compact in structure, convenient to machine and low in cost.

The invention relates to small broadband antennae, in particular to a bow-tie slot antenna based on coplanar waveguide feed. The antenna comprises an earth plate (1) and a dielectric substrate (2), wherein the earth plate (1) is etched with bow-tie slots (3), the two bow-tie slots are bilaterally symmetrical to the X-axis with the center of the dielectric substrate as the origin of coordinates, asymmetrical coplanar waveguide feed is adopted, and annular conduction bands (7) are loaded inside the bow-tie slots. By lengthening and bending one feed slot, impedance matching of the antenna is improved, and the bandwidth of the antenna is increased. Due to the fact that the triangular annular conduction bands are loaded inside the bow-tie slots, low-frequency gains of the antenna are improved, and the gains of the antenna in a working band are made flatter. The antenna works at 2.76-8.1 GHz, relative bandwidth reaches 150.84%, the gains in the working band are all larger than 1.5dBi, and the maximum gain can reach 5.53dBi. The bow-tie slot antenna based on coplanar waveguide feed is simple in design, easy to machine, and suitable for a broadband wireless communication system.

A distributed Raman amplification subsystem for configuring and automatically controlling the pump power on network management interface and its devices are disclosed. The pump power values needed by different optical fibres under different Raman gains are preset in the subsystem. The actual output power of each pump laser is indirectly measured and then compared with the given value by a feedback-ring controller in order to regulate its output power for meeting requirement.

The invention discloses a double-frequency circularly polarized combined antenna with a wide wave beam and a high gain. The antenna comprises a metal pedestal, which is provided with a metal frustum and a cross dipole antenna; and a microstrip antenna is arranged at the metal frustum. The metal frustum is composed of a metal base plate, a medium substrate and a metal paster, wherein the metal base plate, the medium substrate and the metal paster are superposed orderly. The metal paster is in a square shape whose two equal angles on a diagonal are cut off; and a coaxial cable is connected to the metal paster and an inner core of the coaxial cable is connected with the metal paster. A through hole is arranged at the center of the microstrip antenna. Besides, the cross dipole antenna comprises a rigid coaxial cable is arranged on the metal pedestal; the rigid coaxial cable passes through the metal frustum and the through hole of the microstrip antenna; and an end of the rigid coaxial cable is provided with a slit and a length of the slit is a quarter of an operating wavelength. In addition, a cross oscillator is also arranged at the end of the rigid coaxial cable as well as is composed of two short arms and two long arms; and the inner core of the rigid coaxial cable is connected with one short arm and one long arm.

The invention provides a semiconductor device and a preparation method thereof. According to the semiconductor device, in the first direction, the extension length of the electric injection region is smaller than the extension length of the waveguide groove, carriers cannot be massively accumulated on the edge of the electric injection region, peaks with high power in the edge region in near-field light spots are eliminated, cavity surface damage caused by too strong local light field is avoided, and the reliability of the device is improved; 2, in the first direction, the second groove region is closer to the cavity surface on the same side than the first groove region; the second groove region in the stacking direction is shallower than the first groove region, the limiting effect of the vicinity of the cavity surface on the light field is reduced, therefore, high-order modes in the multimode laser limited in the ridge waveguide are diffused in the second groove region and consumed to a certain degree, the number of the modes is reduced, and the horizontal far-field divergence angle of the light beam is reduced. 3, in the first direction, the third groove region is closer to the cavity surface on the same side than the second groove region; in the stacking direction, the third groove region is deeper than the second groove region, and the third groove region plays a stronger role in limiting carriers when electric injection is carried out on the semiconductor device.

The invention discloses a duplex filtering antenna based on a central short circuit T-shaped resonator, and the antenna comprises an upper dielectric substrate, a lower dielectric substrate, stacked square parasitic patches printed on the upper surface of the upper dielectric substrate, a square microstrip patch printed on the upper surface of the lower dielectric substrate, a transmitting channelfeed network and a receiving channel feed network which are loaded at two sides of the square microstrip patch, a transmitting port which is disposed at the same side as the transmitting channel feednetwork and is connected with the transmitting channel feed network, a receiving port which is disposed at the same side as the receiving channel feed network and is connected with the receiving channel feed network, and a reflection grounding plate which is printed on the lower surface of the lower dielectric substrate. The central short circuit T-shaped resonator is introduced as a feed network, and the stacked patches serve as a radiation unit. The antenna has a function of frequency division duplex, can achieve the simultaneous transmitting and receiving, and the electromagnetic weaves employed by the transmitting and receiving operations of the antenna are linearly polarized electromagnetic waves.

The invention belongs to the technical field of ultra-wide-band, special optical fibers and optical appliances, and particularly relates to a fluorotellurite er-doped optical fiber. The fluorotellurite er-doped optical fiber consists of a fiber core and a coating layer coated at outside of the fiber core; the fluorotellurite er-doped optical fiber is characterized by being prepared by mole TeO2: ZnF2: Na2CO3, Er2O3; the coating layer is prepared by a third raw material with the mole ratio of TeO2: ZnF2: Na2CO3=(53-57): (33-37): (4-6); the diameter of the fiber core is (5.0+ / -0.4) miu m; the diameter of the coating layer is (125+ / -0.5) miu m. The invention further discloses a preparation method of the optical fiber, a terminal formation method and an ultra-wide-band optical fiber amplifier with the optical fiber. The fluorotellurite er-doped optical fiber has a softer optical fiber signal channel with wider band width, flatter gain, and more storage, and can reduce the input of light devices, greatly reduces the system cost, and others.

The invention discloses a broadband patch antenna based on differential resonator feed. The antenna comprises a metal bottom plate, an L-shaped folding sheet located above the metal bottom plate, a radiation patch which is arranged at the top of the L-shaped folding sheet and is parallel to the metal bottom plate, a dielectric substrate which is arranged on the lower surface of the metal bottom plate in an attached mode, a resonance unit which is formed on the dielectric substrate, and a the feeder line connected with the resonance unit. One horizontal folding face of the L-shaped folding sheet perpendicularly passes through the metal bottom plate and the dielectric substrate to be connected with the resonance unit through a metal probe. According to the invention, the antenna reduces thecross polarization by using differential feed, and works in four resonant modes. The bandwidth reaches 63.7%, and the profile height of the antenna is only 0.158 vacuum wavelengths; and a flat gain and a stable radiation pattern are kept right above the antenna in the pass band.

A photovoltaic module including a transparent first layer forming a front face, plural photovoltaic cells, and an assembly encapsulating the photovoltaic cells. The first layer includes plural plates independent from each other, each plate located opposite a photovoltaic cell. Rigidity of the encapsulating assembly is defined by a Young's modulus of encapsulation material greater than or equal to 75 MPa at ambient temperature and a thickness of the encapsulating assembly between 0.4 and 1 mm. The first layer includes at least one transparent polymer material of acrylic block copolymers or a composition including at least one acrylic block copolymer having formula (A)nB, in which: n is an integer greater than or equal to 1; A is an acrylic or methacrylic homo- or copolymer having a glass transition temperature greater than 50° C.; and B is an acrylic or methacrylic homo- or copolymer having a glass transition temperature less than 20° C.

The invention discloses a temperature compensation attenuator, which is applied to a radio frequency system along with temperature rise and attenuation drop under the condition of keeping matching, and can realize the effect of compensating high and low temperature gain changes of other radio frequency modules, so that the high and low temperature gain of a transceiving link is flat, and the design difficulty of high and low temperature application of the radio frequency system is reduced.

The invention discloses an II-shaped groove antenna. The II-shaped groove antenna comprises a medium substrate, a feed network which is arranged on the medium substrate and consists of microstrip lines, a ground plate and an I-shaped groove formed in the lower surface of the ground plate. The feed network comprises an emission channel feed network arranged on the left part of the upper surface ofthe medium substrate and a receiving channel feed network arranged on the right side of the upper surface of the medium substrate. The emission channel feed network comprises a C type microstrip line,an L type open-circuit branch line connected to the middle position of the C type micro-strip line and a feed micro-strip line performing end coupling feeding on the L type open circuit branch line;the feed micro-strip line is connected to an emission port; the receiving channel feed network comprises the C type micro-strip line, the L type open circuit branch line arranged in the middle position of the C type micro-strip line, an open circuit branch line connected to the L type open circuit branch line, a feed micro-strip line performing end coupling feeding on the L type open circuit branch line; the feed micro-strip line is connected to the receiving port; and the I-shaped groove consists of three rectangle grooves of different sizes which form in an I shape.

The invention discloses a pyramid horn filtering antenna based on a waveguide structure. The filtering antenna has a filtering characteristic and a radiation characteristic at the same time, wherein the filtering characteristic is generated by four rectangular resonant cavities, and the radiation characteristic is generated by the last stage of resonant cavity and a pyramid horn together. The coupling strength between the adjacent resonant cavities, the external quality factor of a filter and the radiation quality factor of the antenna can be controlled by adjusting the width of an inductance diaphragm window. When the external quality factor of the filter is equal to the radiation quality factor of the antenna, mutual influence of a filtering unit and a radiation unit can be avoided. By introducing the pyramid horn, the radiation gain and directionality of the antenna can be improved, and the minor lobe is reduced. The filtering antenna provided by the invention has the advantages of gain flatness, high selectivity, low minor lobe, low cross polarization, simple and reliable structure and easiness integration, and is applicable to various communication systems.

The invention relates to an antenna, in particular to a non-cross-feeding log-periodic antenna. The contradiction of a traditional log-periodic antenna ultra wide band feature and antenna size is solved, and limitation on system integration application from a feeding mode is avoided. The non-cross-feeding log-periodic antenna comprises a dielectric plate, two first horizontal metal belt strips, two second horizontal metal belt strips, two third horizontal metal belt strips, two fourth horizontal metal belt strips, two fifth horizontal metal belt strips, two sixth horizontal metal belt strips, two seventh horizontal metal belt strips, two eighth horizontal metal belt strips, two ninth horizontal metal belt strips, two tenth horizontal metal belt strips, two eleventh horizontal metal belt strips, two twelfth horizontal metal belt strips and two vertical metal belt strips. The non-cross-feeding log-periodic antenna is used for the field of wireless communication.

There is provided a technique for improving the flatness at the surface of members embedded in a plurality of recesses without resulting in an increase in the time required for the manufacturing processes. According to this technique, the dummy patterns can be placed up to the area near the boundary BL between the element forming region DA and dummy region FA by placing the first dummy pattern DP1 of relatively wider area and the second dummy pattern DP2 of relatively small area in the dummy region FA. Thereby, the flatness of the surface of the silicon oxide film embedded within the isolation groove can be improved over the entire part of the dummy region FA. Moreover, an increase of the mask data can be controlled when the first dummy patterns DP1 occupy a relatively wide region among the dummy region FA.

The invention discloses a reflection array antenna unit, a reflection array antenna and a manufacturing method. An upper dielectric substrate and a lower dielectric substrate of the reflective array antenna unit are in press fit connection, and a radiation patch is arranged at the corner of the top surface of the upper dielectric substrate. The upper foil plate is provided with a first coupling gap, a second coupling gap and a third coupling gap which are located below the radiation patch; the lower dielectric substrate comprises a metallized via hole, and the lower dielectric substrate, the upper foil plate and the lower foil plate jointly form a dielectric integrated waveguide; the metallized through holes comprise first metallized through holes which are uniformly distributed around theantenna unit and on at least one side of the radiation patch; the three slots and the radiation patch play a role of a resonator, are coupled and cross-coupled with each other, have filtering characteristics, and can effectively suppress out-of-band interference; the reflective array antenna feeds each antenna unit in an empty feed mode, has the characteristics of low loss, low profile and high gain, is good in signal quality, and has the characteristics of miniaturization and integration.

The invention discloses a Raman multi-wavelength converter and method for realizing gain flatness by connecting two fibers in series. The converter comprises a signal light generator, an erbium doped fiber amplifier, a plurality of detecting light lasers, a continuous pump laser and a first wave combiner, wherein the output end of the first wave combiner is connected with a first wave separator through a third optical fiber; the output end of the first wave separator is connected with a second wave combiner; and the output end of the second wave combiner is connected with a second wave separator through a sixth fiber. The method comprises the following steps of: selecting a signal light generator, to form a pump signal light; selecting the plurality of detecting light lasers, wherein the pump signal light is coupled with a plurality of continuous detecting light for wavelength conversion to output a plurality of detecting light with different light powers; and selecting the continuous pump laser, wherein the continuous pump light is coupled with a plurality of detecting light for gain compensation to output a plurality of detecting light with equal light powers. The Raman multi-wavelength converter is reasonable in design, high in conversion rate, good in output signal extinction ratio, and can realize cross-waveband and multi-wavelength simultaneous conversion and gain flatness.

The invention discloses a coaxial waveguide filtering antenna with adjustable frequency. The coaxial waveguide filtering antenna comprises a standard WR-90 waveguide, wherein a waveguide excitation port and an antenna radiation port are formed in the two ends of the standard WR-90 waveguide respectively, a first tuning screw, a second tuning screw, a third tuning screw and a fourth tuning screw which are arranged in a row in the direction from one end to the other end of the standard WR-90 waveguide are vertically inserted into the upper surface of the standard WR-90 waveguide, the insertion depths of the first tuning screw and the fourth tuning screw are the same, the insertion depths of the second tuning screw and the third tuning screw are the same, a fifth tuning screw, a sixth tuning screw and a seventh tuning screw which are on the same straight line with the first tuning screw, the second tuning screw, the third tuning screw and the fourth tuning screw are vertically inserted into the lower surface of the standard WR-90 waveguide, the fifth tuning screw is located between the first tuning screw and the second tuning screw, the sixth tuning screw is located between the second tuning screw and the third tuning screw, the seventh tuning screw is located between the third tuning screw and the fourth tuning screw, and the insertion depths of the fifth tuning screw and the seventh tuning screw are the same. The center frequency of the antenna can be adjusted by adjusting the insertion depths of the screws, and the coaxial waveguide filtering antenna has the advantages of being simple and reliable in structure, convenient to process, low in loss, high in performance and the like.

The invention discloses a waveguide filtering antenna array based on a resonant cavity in a mixed resonant mode. The waveguide filtering antenna array comprises a first metal block, a second metal block, a third metal block, a fourth metal block, a fifth metal block, a sixth metal block, a seventh metal block and an eighth metal block, wherein a gap array is arranged in the center of the first metal block; a first rectangular resonant cavity is formed in the center of the second metal block; a first coupling slot is formed in the center of the third metal block; a second rectangular resonant cavity is formed in the center of the fourth metal block, and the center of the second rectangular resonant cavity is provided with a cuboid metal column with one end connected with the fourth metal block; a second coupling slot is formed in the center of the fifth metal block; a third rectangular resonant cavity is formed in the center of the sixth metal block; a third coupling slot is formed in the center of the seventh metal block; and the center of the eighth metal block is provided with a waveguide excitation port. Different modes are combined to improve the bandwidth of the antenna and introduce a radiation zero point, the filtering antenna designed by cavity resonance is utilized to realize the characteristic of low loss, and the whole antenna array is reliable in structure, convenient to process, high in selectivity and low in cost.

The invention discloses a broadband MIMO differential filter slot antenna comprising an antenna board and four differential filter slot antenna units; the four differential filter slot antenna units are symmetric about a center point of the antenna board, and each two adjacent differential filter slot antenna units are perpendicular to each other; the antenna board comprises a dielectric substrate, an upper metal layer and a lower metal layer; each differential filter slot antenna unit comprises a slot radiator, a dual mode resonator and two microstrip feeders; the dual mode resonator comprises a closed loop microstrip line and two short-circuit stubs; and each of the short-circuit stubs is provided with a metal through-hole. The antenna of the invention has a steep skirt band and overallefficiency of in-band flatness, maintains good stability and low cross polarization at different frequencies, and has strong suppression of common mode signals. Meanwhile, high isolation is realized without adoption of a decoupling network, so that the filter antenna is miniaturized.

Device for the emission or amplification of a signal, comprising an optical fibre (1) having a solid core (2) of refractive index nc, made of a silica glass doped with a rare earth, such as erbium, ytterbium or neodymium, said core being surrounded by an optical cladding (3, 4, 5, 6, 7, 8) comprising at least a pair of silica layers composed of a first, inner layer (3), having a refractive index greater than the refractive index nc of the core (2), covered by a second, outer layer (4). The optical fibre (1) comprises several pairs of silica layers (3, 4; 5, 6; 7, 8) around the core (2), each pair comprising an inner layer (3, 5, 7) of refractive index ni and an outer layer (4, 6, 8) of refractive index ne, the refractive index ne of the outer layer being lower that the refractive index ni of the inner layer of the same pair.

The invention discloses a double-segment complementary type erbium-doped fiber amplifier. The double-segment complementary type erbium-doped fiber amplifier comprises an input module, an erbium-doped fiber module, a radiation module and a feedback module, wherein the feedback module comprises a micro-processor and a detection module, the erbium-doped fiber module comprises a first erbium-doped optical fiber and a second erbium-doped optical fiber which are connected in series, the input module is used for sequentially inputting an input laser signal to the first erbium-doped fiber and the second erbium-doped optical fiber and then outputting an amplification signal, the radiation module is used for outputting radiation dosage and radiating the second erbium-doped optical fiber, the detection module is used for detecting whether gain of the amplification signal is flat or not and outputting a control signal to the micro-processor if the gain is not flat, and the micro-processor is used for controlling the radiation dosage output from the radiation module so as to achieve grain flatness of the amplification signal. With the utilization of a radiation effect of the erbium-doped fiber amplifier, the gain characteristic of the erbium-doped optical fibers which are not radiated and the grain characteristic of the erbium-doped optical fibers which are radiated are complementary, and the effect of improving the grain spectrum flatness of the erbium-doped optical fibers is achieved.