A high extinction ratio fiber amplifier and its operating method

Abstract

The application provides a high-extinction-ratio optical fiber amplifier, which is composed of a first gain optical fiber, an optical blocker and a second gain optical fiber arranged in sequence along an optical path direction, and a pump source is connected to the second gain optical fiber through a beam combiner, wherein the optical path direction of the pump source is opposite to the signal light direction of the optical fiber amplifier; the optical blocker is composed of a double-fiber collimator, a roof prism, a first combination prism, a rotator and a second combination prism arranged in sequence with intervals, and a signal light filter is further arranged in the optical blocker; and the double-fiber collimator is connected with the first gain optical fiber and the second gain optical fiber respectively. The application has a reasonable structure design, filters out the amplified spontaneous emission light generated in the amplification process, reduces the index requirement and cost of the filter through the signal light filter twice, uses the residual pump light in the second amplification as the pump light in the first amplification, realizes the reverse optical isolation protection between the two-stage amplifiers, and improves the extinction ratio of the amplifier as a whole.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser radar, and particularly relates to a high-extinction-ratio optical fiber amplifier. BACKGROUND

[0002] The higher the extinction ratio of the pulse laser fiber amplifier for the laser radar is, that is, the smaller the noise is, the better the detection performance of the laser radar is, and the noise of the pulse laser fiber amplifier mainly comes from amplified spontaneous emission light. At present, the pulse laser fiber amplifier usually adopts a continuous light-emitting pump source. Due to the gain saturation effect of the gain fiber, a small-power signal light is easy to reach the gain saturation state in the amplification process, and useless amplified spontaneous emission light for the laser radar is generated. The amplified spontaneous emission light will cause the gain of the signal light to decrease, so that the optical-to-optical conversion efficiency of the pulse laser fiber amplifier is significantly reduced, and the noise performance is deteriorated. The common methods for suppressing the amplified spontaneous emission light are: a multi-stage amplification mode is adopted to reduce the generation of the amplified spontaneous emission, or a filter is added at the end of the amplifier to filter out the amplified spontaneous emission. Both of the two conventional modes need to introduce more devices, and the system is relatively complex, which is not conducive to miniaturization. SUMMARY

[0003] Therefore, the purpose of the application is to provide a high-extinction-ratio optical fiber amplifier and a working method thereof, so as to solve the problems in the prior art.

[0004] The application adopts the following scheme: a high-extinction-ratio optical fiber amplifier, which is composed of a first gain fiber, an optical blocker and a second gain fiber arranged in sequence along the light path direction, a pump source is connected to the second gain fiber through a beam combiner, the light path direction of the pump source is opposite to the signal light direction of the optical fiber amplifier, the optical blocker is composed of a double-fiber collimator, a roof prism, a first combination prism, a rotator and a second combination prism arranged in sequence with intervals, and a signal light filter is further arranged in the optical blocker, and the double-fiber collimator is connected with the first gain fiber and the second gain fiber respectively.

[0005] Further, the double-fiber collimator comprises a glass sleeve, a capillary and a lens are arranged in the glass sleeve at intervals, the capillary is coated with a first double-clad optical fiber and a second double-clad optical fiber arranged in parallel, one end of the first double-clad optical fiber and the second double-clad optical fiber extends out of the glass sleeve and is connected with the first gain fiber and the second gain fiber respectively, and the other end faces the lens, and the cladding of the first double-clad optical fiber and the second double-clad optical fiber is used for transmitting pump light, and the core is used for transmitting signal light.

[0006] Further, the ridge side of the roof prism faces the first combined prism, the far side of the roof prism from the ridge side faces the lens, the first combined prism is composed of a first parallelogram prism and a second parallelogram prism arranged in sequence from top to bottom, the rotator is composed of a Faraday rotator and a half-wave plate, the second combined prism is composed of a third parallelogram prism and an isosceles right prism arranged in sequence from top to bottom, the first parallelogram prism is connected with the second parallelogram prism by gluing, the lower surface of the third parallelogram prism and the non-waist surface of the isosceles right prism are connected by gluing, and the signal light filter is placed at an angle of 0.5-8 degrees with the signal light incident direction.

[0007] Further, the roof prism is coated with a film that reflects the pump light and transmits the signal light on the upper surface of the side facing the lens, the first parallelogram prism, the second parallelogram prism are coated with a signal light anti-reflection film on the side facing the lens and the side away from the lens, the upper surface of the first parallelogram prism and the lower surface of the second parallelogram prism are coated with a signal light high-reflection film, the gluing surface of the first parallelogram prism and the second parallelogram prism is coated with a polarization light splitting film, the side facing the lens of the third parallelogram prism and the isosceles right prism and the bottom side of the isosceles right prism are coated with a signal light anti-reflection film, the side of the top surface of the third parallelogram prism is coated with a signal light high-reflection film, and the gluing surface of the third parallelogram prism and the isosceles right prism is coated with a polarization light splitting film.

[0008] Further, the signal light filter is located between the roof prism and the first combined prism, the signal light filter is coated with a narrow-band light filter film on both surfaces, and the side of the third parallelogram prism away from the lens is coated with a signal light high-reflection film.

[0009] Further, the signal light filter is located between the double-fiber collimator and the roof prism, the surface of the signal light filter facing the double-fiber collimator is coated with a film that reflects the pump light and transmits the signal light, and the other surface is coated with a signal light narrow-band light filter film, and the side of the third parallelogram prism away from the lens is coated with a signal light high-reflection film.

[0010] Further, the signal light filter is located behind the side of the second combined prism away from the lens, a mirror is further arranged behind the signal light filter, the surface of the signal light filter facing the second combined prism is coated with a signal light narrow-band light filter film, and the side of the second combined prism away from the lens is coated with a signal light transmission film.

[0011] A kind of high extinction ratio optical fiber amplifier pump light path working method: the pump light of pump source enters second gain optical fiber by combiner, after partial absorption, the remaining pump light is transmitted to second double-clad fiber, is collimated after being input to roof prism by lens, pump light is reflected by the plane of roof prism and returns to lens, lens is coupled into first double-clad fiber, then is transmitted to the first gain optical fiber.

[0012] A kind of high extinction ratio optical fiber amplifier amplification signal light path working method: the input signal light is transmitted to first double-clad fiber after the first amplification of first gain optical fiber, then is collimated after being input to roof prism by lens, parallel collimated light is formed after being refracted by roof prism, after passing through signal filter, signal light wavelength is transmitted but amplified spontaneous emission light is reflected, the transmitted signal light is input to the side of first parallelogram prism close to lens, is reflected by the top surface of first parallelogram prism and is input to the cemented surface of first combination prism, is divided into s polarized signal light component 1 and p polarized signal light component 2 by the polarization beam splitter film in cemented surface.

[0013] S polarized signal light component 1 is reflected by cemented surface and is transmitted to Faraday rotator by the side of first parallelogram prism away from lens, Faraday rotator realizes the rotation of s polarized signal light component 1 by 45 degrees counterclockwise, after passing through half wave plate, signal light realizes the rotation of 45 degrees clockwise, signal light becomes s polarized signal light component 1 again, then is input to third parallelogram prism, is reflected by the top surface of third parallelogram prism after being transmitted through the side of third parallelogram prism close to lens, is input to the side of third parallelogram prism away from lens after being reflected by the cemented surface of second combination prism, is reflected by the side of third parallelogram prism away from lens and returns to half wave plate along the original light path, s polarized signal light component 1 is input to Faraday rotator after the polarization direction of s polarized signal light component 1 is rotated by 45 degrees counterclockwise, the polarization direction of signal light after rotation is rotated by 45 degrees counterclockwise again, so as to become p polarized signal light component 1, p polarized signal light component 1 is input to second parallelogram prism after being transmitted through the side of first parallelogram prism close to lens and cemented surface, then is transmitted by the side of second parallelogram prism close to lens, after passing through signal filter, signal light wavelength is transmitted but amplified spontaneous emission light is reflected, p polarized signal light component 1 is input to lens after passing through roof prism, is coupled into the core of second double-clad fiber by lens, is transmitted to second gain optical fiber and is amplified by second stage, then is output by the combiner, so as to realize two-stage amplification of signal light.

[0014] The p-polarized signal light component 2 is transmitted by the cemented surface of the first combined prism, reflected by the bottom surface of the second parallelogram prism and transmitted by the side far from the lens of the second parallelogram prism, and then is incident on the Faraday rotator. The Faraday rotator rotates the p-polarized signal light component 2 by 45 degrees counterclockwise. After the rotated signal light component 2 passes through the half-wave plate, it is rotated by 45 degrees clockwise, and becomes the p-polarized signal light component 2 again. Then the p-polarized signal light component 2 is incident on the isosceles right-angle prism, transmitted by the side close to the lens of the isosceles right-angle prism and the cemented surface of the second combined prism, and then is incident on the third parallelogram prism. The third parallelogram prism reflects the p-polarized signal light component 2 by the side far from the lens, and then the p-polarized signal light component 2 returns to the half-wave plate along the original light path. The p-polarized signal light component 2 is rotated by 45 degrees counterclockwise, and then is incident on the Faraday rotator. The polarization direction of the rotated signal light is rotated by 45 degrees counterclockwise again, and thus becomes the s-polarized signal light component 2. The s-polarized signal light component 2 is transmitted by the side far from the lens of the second parallelogram prism, reflected by the bottom surface and the cemented surface, and then is transmitted by the side close to the lens of the second parallelogram prism. After passing through the signal filter, the signal light is transmitted, but the amplified spontaneous emission light is reflected. The transmitted s-polarized signal light component 2 is incident on the lens through the roof prism, and is coupled into the core of the second double-clad fiber by the lens. The s-polarized signal light component 2 is transmitted into the second gain fiber, amplified by the second stage, and then is output from the combiner 4, so that the two-stage amplification of the signal light is realized.

[0015] A method for operating the high-extinction-ratio optical fiber amplifier in the direction of light: the backward light generated by the amplification in the second gain fiber is transmitted through the second double-clad fiber, collimated by the lens into the roof prism, and then is refracted into parallel collimated light by the roof prism. The parallel collimated light is incident on the signal filter, and then is incident on the second parallelogram prism. The second parallelogram prism transmits the parallel collimated light by the side close to the prism, and divides the parallel collimated light into the s-polarized signal light component 3 and the p-polarized signal light component 4 by the polarization beam splitter film of the cemented surface.

[0016] The s-polarized signal light component 3 is reflected by the cemented surface, the bottom surface and the side far from the lens of the second parallelogram prism in sequence, and then is incident on the Faraday rotator. The Faraday rotator rotates the s-polarized signal light component 3 by 45 degrees counterclockwise. After the rotated signal light passes through the half-wave plate, it is rotated by 45 degrees clockwise, and becomes the s-polarized signal light component 3 again. The s-polarized signal light component 3 is incident on the isosceles right-angle prism, transmitted by the side close to the lens of the isosceles right-angle prism, reflected by the cemented surface, and then is transmitted by the bottom surface. Thus, the s-polarized signal light component 3 is transmitted out of the light path of the entire amplifier, and thus the isolation of the backward light is realized.

[0017] The p-polarized signal light component 4 is transmitted by the cemented surface of the first parallelogram prism in turn, transmitted by the side far from the lens, and then incident to the Faraday rotator. The Faraday rotator rotates the p-polarized signal light component 4 counterclockwise by 45 degrees. The rotated signal light is rotated clockwise by 45 degrees by the half-wave plate, and the signal light becomes the p-polarized signal light component 4 again and is incident to the third parallelogram prism. The signal light is transmitted by the side close to the lens, reflected by the top surface, and transmitted by the cemented surface in turn, and finally transmitted by the bottom surface of the isosceles right prism, so that the signal light is transmitted to the optical path outside the entire amplifier, and the reverse light is isolated.

[0018] Compared with the prior art, the application has the following beneficial effects: the structure design is reasonable, the amplified spontaneous emission light generated in the amplification process can be filtered out, the index requirement of the filter and the cost thereof can be reduced by twice filtering of the signal light, the residual pump light in the second amplification is used as the pump light in the first amplification, the reverse light isolation protection between the two amplifiers is realized, and the overall structure effectively improves the extinction ratio of the amplifier. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Fig. 1 is a schematic diagram of the overall structure of the embodiment 1 of the application.

[0020] Figure 2 Fig. 2 is a schematic diagram of the light blocking device of the embodiment 1 of the application.

[0021] Figure 3 Fig. 3 is a schematic diagram of the double-fiber collimator of the embodiment 1 of the application.

[0022] Figure 4 Fig. 4 is a schematic diagram of the first combined prism of the embodiment 1 of the application.

[0023] Figure 5 Fig. 5 is a schematic diagram of the optical rotator of the embodiment 1 of the application.

[0024] Figure 6 Fig. 6 is a schematic diagram of the second combined prism of the embodiment 1 of the application.

[0025] Figure 7 Fig. 7 is a schematic diagram of the pump light path of the embodiment 1 of the application.

[0026] Figure 8 Fig. 8 is a schematic diagram of the amplified signal light path of the embodiment 1 of the application.

[0027] Figure 9 Fig. 9 is a schematic diagram of the reverse light path of the embodiment 1 of the application.

[0028] Figure 10 Fig. 10 is a schematic diagram of the embodiment 2 of the application.

[0029] Figure 11 is a structural schematic diagram of embodiment 3 of the present application.

[0030] In the figure: 1 - first gain optical fiber; 2 - optical blocker; 3 - second gain optical fiber; 4 - beam combiner; 5 - pump source; 201 - double fiber collimator; 202 - roof prism; 203 - signal light filter; 204 - first combination prism; 205 - rotator; 206 - second combination prism; 201a - first double-clad fiber; 201b - second double-clad fiber; 201c - capillary; 201d - lens; 201e - glass sleeve; 204a - first parallelogram prism; 204b - second parallelogram prism; 205a - third parallelogram prism; 205b - isosceles right prism; SA1 - first parallelogram prism near the lens side; SA2 - first parallelogram prism top surface; SA3 - first parallelogram prism away from the lens side; SA4 - first parallelogram prism cement surface; SB1 - second parallelogram prism near the lens side; SB2 - second parallelogram prism cement surface; SB3 - second parallelogram prism away from the lens side; SB4 - first parallelogram prism bottom surface; SC1 - third parallelogram prism near the lens side; SC2 - third parallelogram prism top surface; SC3 - third parallelogram prism away from the lens side; SC4 - third parallelogram prism cement surface; SD1 - isosceles right prism near the lens side; SD2 - isosceles right prism cement surface; SD3 - isosceles right prism bottom surface. DETAILED DESCRIPTION

[0031] The present application will be further described below in conjunction with the accompanying drawings and examples.

[0032] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0033] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It is also to be understood that the term "comprising" as used herein is intended to mean "including" but not "consisting of." It is further to be understood that the use of the term "including" as well as "comprising" is not limiting.

[0034] Example 1, as Figures 1-9As shown, a high extinction ratio fiber amplifier is composed of a first gain fiber 1, an optical blocker 2 and a second gain fiber 3 arranged in sequence along the optical path direction, the second gain fiber is connected with a pump source 5 through a beam combiner 4, the optical path direction of the pump source is opposite to the signal light direction of the fiber amplifier, the optical blocker is composed of a double fiber collimator 201, a roof prism 202, a first combination prism 204, a rotator 205 and a second combination prism 206 arranged in sequence with intervals, a signal light filter 203 is further arranged in the optical blocker, the double fiber collimator is connected with the first gain fiber and the second gain fiber respectively; the pump source is used for generating pump light; the beam combiner is used for coupling the pump light into the second gain fiber and outputting amplified signal light; the second gain fiber is used for absorbing pump light and performing second-stage amplification on the output signal light; the optical blocker is used for filtering out amplified spontaneous emission and coupling the remaining pump light in the second gain fiber into the first gain fiber, while isolating the reverse light generated in the second gain fiber from entering the first gain fiber; the first gain fiber is used for absorbing pump light and performing first-stage amplification on the input signal light.

[0035] In the embodiment, the double fiber collimator comprises a glass sleeve 201e, a capillary 201c and a lens 201d are arranged in the glass sleeve in intervals, the capillary is coated with a first double-clad fiber 201a and a second double-clad fiber 201b arranged in parallel, one end of the first double-clad fiber and the second double-clad fiber extends out of the glass sleeve and is connected with the first gain fiber and the second gain fiber respectively, and the other end faces the lens, the cladding of the first double-clad fiber and the second double-clad fiber is used for transmitting pump light, and the core is used for transmitting signal light, the capillary is used for fixing the first double-clad fiber and the second double-clad fiber, and the three components form a double fiber head; the lens is used for collimating and coupling pump light and signal light; the glass sleeve is used for fixing the double fiber head and the lens; the first gain fiber and the first double-clad fiber are connected through fusion; and the second gain fiber and the second double-clad fiber are connected through fusion.

[0036] In the embodiment, the ridge side of the roof prism faces the first combined prism, the far side of the roof prism from the ridge faces the lens, the first combined prism is composed of the first parallelogram prism 204a and the second parallelogram prism 204b arranged in sequence from top to bottom, the rotator is composed of a Faraday rotator and a half-wave plate, the Faraday rotator is used to rotate the polarization direction of the signal light by 45 degrees in a non-reciprocal manner; the half-wave plate is used to rotate the polarization direction of the signal light by 45 degrees; the rotator is used to not rotate the polarization direction of the signal light transmitted from left to right, and the rotator is used to rotate the polarization direction of the signal light transmitted from right to left by 90 degrees, the second combined prism is composed of the third parallelogram prism 205a and the isosceles right prism 205b arranged in sequence from top to bottom, the first parallelogram prism is glued to the second parallelogram prism, the lower surface of the third parallelogram prism is glued to the non-waist surface of the isosceles right prism, and the signal light filter is placed at an angle of 0.5-8 degrees with the signal light incident direction.

[0037] In the embodiment, a film that reflects pump light and transmits signal light is coated on the plane of the roof prism facing the lens, and this plane is on the focal plane of the lens, for reflecting pump light and transmitting signal light, the roof prism is used to refract signal light into parallel collimated light, the first parallelogram prism and the second parallelogram prism are coated with a signal light antireflection film on the side facing the lens and the side away from the lens, the upper surface of the first parallelogram prism and the lower surface of the second parallelogram prism are both coated with a signal light high-reflection film, the glued surface of the first parallelogram prism and the second parallelogram prism is coated with a polarization beam splitting film, the side facing the lens of the third parallelogram prism and the bottom side of the isosceles right prism are both coated with a signal light antireflection film, the side of the top surface of the third parallelogram prism is coated with a signal light high-reflection film, and the glued surface of the third parallelogram prism and the isosceles right prism is coated with a polarization beam splitting film.

[0038] In the embodiment, the signal light filter is located between the roof prism and the first combined prism, the signal light filter is coated with a narrow-band filter film on both sides, allowing signal light to pass and amplified spontaneous emission light to be reflected; the far side of the third parallelogram prism from the lens is coated with a signal light high-reflection film.

[0039] In the embodiment, the cross sections of the first parallelogram prism, the second parallelogram prism and the third parallelogram prism are 45-degree parallelograms; the planes on the side of the prisms facing the lens are perpendicular to the length direction of the light blocker; the first parallelogram prism and the second parallelogram prism are prisms of the same shape, the bottom surface of the third parallelogram prism is completely attached to the non-waist surface of the isosceles right prism, and the two mutually perpendicular waist surfaces of the isosceles right prism, one of which is perpendicular to the length direction of the light blocker, and the other is located on the bottom surface.

[0040] A working method of a pump light path of a high-extinction-ratio optical fiber amplifier: pump light of a pump source enters a second gain optical fiber through a beam combiner, after partial absorption of the second gain optical fiber, the remaining pump light is transmitted into a second double-clad optical fiber, is collimated by a lens and is input into a roof prism, the pump light is reflected by a plane of the roof prism and returns to the lens, the lens is coupled into a first double-clad optical fiber and is then transmitted into the first gain optical fiber.

[0041] A working method of an amplified signal light path of a high-extinction-ratio optical fiber amplifier: input signal light is amplified by a first stage of a first gain optical fiber, is transmitted into a first double-clad optical fiber, is collimated by a lens and is incident on a roof prism, is refracted by the roof prism into parallel collimated light, after passing through a signal filter, signal light is transmitted but amplified spontaneous emission light is reflected, the transmitted signal light is incident on a first parallelogram prism on the side close to the lens, is reflected by a top surface of the first parallelogram prism and is incident on a cemented surface of a first combination prism, is separated by a polarization beam splitter film in the cemented surface into an s-polarized signal light component 1 and a p-polarized signal light component 2.

[0042] The s-polarized signal light component 1 is reflected by the cemented surface and transmitted by the first parallelogram prism away from the side of the lens to the Faraday rotator, the Faraday rotator rotates the s-polarized signal light component 1 counterclockwise by 45 degrees, the rotated signal light rotates clockwise by 45 degrees after passing through the half-wave plate 205b, the signal light becomes the s-polarized signal light component 1 again, and then is incident on the third parallelogram prism. The s-polarized signal light component 1 is transmitted by the third parallelogram prism close to the side of the lens, is reflected by the top surface of the third parallelogram prism, is reflected by the cemented surface of the second combined prism, and is incident on the side of the third parallelogram prism away from the lens. The s-polarized signal light component 1 is reflected by the side of the third parallelogram prism away from the lens, returns to the half-wave plate along the original light path, and is incident on the Faraday rotator after the polarization direction of the s-polarized signal light component 1 is rotated counterclockwise by 45 degrees. The polarization direction of the rotated signal light is rotated counterclockwise by 45 degrees again, so that the signal light becomes the p-polarized signal light component 1. The p-polarized signal light component 1 is transmitted by the first parallelogram prism close to the side of the lens and the cemented surface, enters the second parallelogram prism, and is transmitted by the side of the second parallelogram prism close to the lens. After passing through the signal filter, the signal light wavelength is transmitted but the amplified spontaneous emission light is reflected. The transmitted p-polarized signal light component 1 is incident on the lens after passing through the roof prism, is coupled into the core of the second double-clad optical fiber by the lens, is transmitted into the second gain optical fiber to be amplified by the second stage, and is output by the combiner, so that two-stage amplification of the signal light is realized.

[0043] The p-polarized signal light component 2 is transmitted by the cemented surface of the first combined prism, reflected by the bottom surface of the second parallelogram prism and transmitted by the side far from the lens of the second parallelogram prism, and then is incident on the Faraday rotator. The Faraday rotator rotates the p-polarized signal light component 2 by 45 degrees counterclockwise. After the rotated signal light component 2 passes through the half-wave plate, it is rotated by 45 degrees clockwise, and becomes the p-polarized signal light component 2 again. Then the p-polarized signal light component 2 is incident on the isosceles right-angle prism, transmitted by the side close to the lens of the isosceles right-angle prism and the cemented surface of the second combined prism, and then is incident on the third parallelogram prism. The third parallelogram prism reflects the p-polarized signal light component 2 by the side far from the lens, and then the p-polarized signal light component 2 returns to the half-wave plate along the original light path. The p-polarized signal light component 2 is rotated by 45 degrees counterclockwise, and then is incident on the Faraday rotator. The polarization direction of the rotated signal light is rotated by 45 degrees counterclockwise again, and thus becomes the s-polarized signal light component 2. The s-polarized signal light component 2 is transmitted by the side far from the lens of the second parallelogram prism, reflected by the bottom surface and the cemented surface, and then is transmitted by the side close to the lens of the second parallelogram prism. After passing through the signal filter, the signal light is transmitted, but the amplified spontaneous emission light is reflected. The transmitted s-polarized signal light component 2 is incident on the lens through the roof prism, and is coupled into the core of the second double-clad fiber by the lens. The s-polarized signal light component 2 is transmitted into the second gain fiber, amplified by the second stage, and then is output by the combiner 4. Thus, the two-stage amplification of the signal light is realized.

[0044] A method for operating a high-extinction-ratio optical fiber amplifier in a direction light mode: the backward light generated by the amplification in the second gain fiber is transmitted through the second double-clad fiber, collimated by the lens into the roof prism, and then is refracted into parallel collimated light by the roof prism. The parallel collimated light is incident on the signal filter, and then is incident on the second parallelogram prism. The second parallelogram prism transmits the parallel collimated light by the side close to the prism, and the cemented surface divides the parallel collimated light into the s-polarized signal light component 3 and the p-polarized signal light component 4 by the polarization beam splitter film.

[0045] The s-polarized signal light component 3 is reflected by the cemented surface, the bottom surface and the side far from the lens of the second parallelogram prism in sequence, and then is incident on the Faraday rotator. The Faraday rotator rotates the s-polarized signal light component 3 by 45 degrees counterclockwise. After the rotated signal light passes through the half-wave plate, it is rotated by 45 degrees clockwise, and becomes the s-polarized signal light component 3 again. The s-polarized signal light component 3 is incident on the isosceles right-angle prism, transmitted by the side close to the lens, reflected by the cemented surface and transmitted by the bottom surface of the isosceles right-angle prism in sequence. Thus, the s-polarized signal light component 3 is transmitted out of the light path of the entire amplifier, and thus the isolation of the backward light is realized.

[0046] The p-polarized signal light component 4 is transmitted by the cemented surface of the first parallelogram prism, transmitted by the side surface far from the lens, and then incident on the Faraday rotator. The Faraday rotator rotates the p-polarized signal light component 4 counterclockwise by 45 degrees. The rotated signal light is rotated clockwise by 45 degrees by the half-wave plate, and the signal light becomes the p-polarized signal light component 4 again and is incident on the third parallelogram prism. The signal light is transmitted by the side surface close to the lens, reflected by the top surface, and transmitted by the cemented surface, and then transmitted by the bottom surface of the isosceles right prism, so as to be transmitted to the optical path outside the entire amplifier, thereby realizing the isolation of the reverse light.

[0047] Embodiment 2, as described above, is different from embodiment 1 in that the signal light filter is located between the double-fiber collimator and the roof prism, the surface of the signal light filter facing the double-fiber collimator is coated with a film reflecting the pump light and transmitting the signal light, and the other surface is coated with a signal light narrow-band filter film for transmitting the signal light and reflecting the amplified spontaneous emission light. The side surface far from the lens of the third parallelogram prism is coated with a high-reflection film for the signal light, and the roof prism is coated with a signal light transmission film. The remaining parts of embodiment 2 are the same as those of embodiment 1, and thus will not be described herein. Figure 10 Embodiment 3, as described above, is different from embodiment 1 in that the signal light filter is located on the side far from the lens of the second combined prism, i.e., the last side. A mirror is arranged on the rear side of the signal light filter for reflecting the signal light. The surface of the signal light filter facing the second combined prism is coated with a signal light narrow-band filter film, and the side surface far from the lens of the second combined prism is coated with a signal light transmission film. The remaining parts of embodiment 2 are the same as those of embodiment 1, and thus will not be described herein.

[0048] Figure 11 Any of the technical solutions disclosed in the present application, unless otherwise stated, if a numerical range is disclosed, the disclosed numerical range is a preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is only one of the many implementable values with more obvious technical effects or representative values. Since there are many values, it is impossible to enumerate all, so the present application discloses some values to illustrate the technical solutions of the present application, and the above-mentioned enumerated values should not constitute a limitation on the protection scope of the present application.

[0049] If the terms "first", "second", etc. are used to limit the components in the present application, those skilled in the art should know that the use of "first", "second" is only for the convenience of distinguishing the components, and the above-mentioned terms have no special meaning unless otherwise stated.

[0050] If the terms "first", "second", etc. are used to limit the components in the present application, those skilled in the art should know that the use of "first", "second" is only for the convenience of distinguishing the components, and the above-mentioned terms have no special meaning unless otherwise stated.

[0051] ​If the present application discloses or relates to mutually fixedly connected parts or structural members, unless otherwise stated, the fixed connection can be understood as: detachably fixedly connected (for example, connected using bolts or screws), and can also be understood as: non-detachable fixed connection (for example, riveting, welding), of course, the mutually fixed connection can also be replaced by an integral structure (for example, manufactured by integral forming using casting process) (except for obvious cases that cannot use integral forming process).

[0052] In addition, the above-mentioned application discloses any technical solution applied to indicate the position relationship, such as "vertical", "horizontal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. The orientation or position relationship is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the patent, and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the patent, and the above-mentioned application discloses any technical solution applied to indicate the shape, and the meaning includes shapes similar, similar or close to the shape unless otherwise stated.

[0053] Any component provided by the present application can be assembled from multiple individual components, or can be a single component manufactured by integral forming process.

[0054] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit them; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones; without departing from the spirit of the technical solutions of the present application, they should be covered in the technical solution range of the present application.

Claims

1. A high extinction ratio fiber amplifier, characterized in that, The fiber amplifier consists of a first gain fiber, an optical blocker, and a second gain fiber arranged sequentially along the optical path. A pump source is connected to the second gain fiber via a combiner. The optical path direction of the pump source is opposite to the signal light direction of the fiber amplifier. The optical blocker is composed of a dual fiber collimator, a roof prism, a first combined prism, a rotator, and a second combined prism arranged sequentially at intervals. A signal light filter is also provided inside the optical blocker. The dual fiber collimator is connected to the first gain fiber and the second gain fiber, respectively. The dual-fiber collimator includes a glass sleeve, in which a capillary tube and a lens are spaced apart, and the capillary tube is covered with a first double-clad fiber and a second double-clad fiber arranged in parallel. The ridge prism faces the first combined prism on its ridge side, and the ridge-away side of the ridge prism faces the lens. The first combined prism consists of a first parallelogram prism and a second parallelogram prism arranged sequentially from top to bottom. The optical rotator consists of a Faraday rotator and a half-wave plate. The second combined prism consists of a third parallelogram prism and an isosceles right-angle prism arranged sequentially from top to bottom. The first parallelogram prism and the second parallelogram prism are glued together. The lower surface of the third parallelogram prism is glued together with the non-square surface of the isosceles right-angle prism. The signal light filter is placed at an angle of 0.5 to 8 degrees to the incident direction of the signal light. The roof prism has a coating on its upper surface facing the lens that reflects pump light and transmits signal light. The first parallelogram prism and the second parallelogram prism have anti-reflection coatings on their lenses and away from the lens. The third parallelogram prism and the isosceles right prism have anti-reflection coatings on their lenses and on their bottom surfaces. The first parallelogram prism, the second parallelogram prism, the third parallelogram prism, and the ridge prism have their planes facing the lens perpendicular to the length direction of the light blocker.

2. The high extinction ratio fiber amplifier according to claim 1, characterized in that, One end of the first double-clad fiber and the second double-clad fiber extends out of the glass sleeve and is connected to the first gain fiber and the second gain fiber, respectively, while the other end faces the lens. The cladding of the first double-clad fiber and the second double-clad fiber is used for the transmission of pump light, and the fiber core is used for the transmission of signal light.

3. The high extinction ratio fiber amplifier according to claim 2, characterized in that, The upper surface of the first parallelogram prism and the lower surface of the second parallelogram prism are coated with a high-reflectivity film for signal light. A polarizing beam splitting film is coated on the bonding surface of the first parallelogram prism and the second parallelogram prism. A polarizing beam splitting film is coated on the bonding surface of the third parallelogram prism and the isosceles right-angle prism. A high-reflectivity film for signal light is coated on one side of the top surface of the third parallelogram prism.

4. The high extinction ratio fiber amplifier according to claim 3, characterized in that, The signal light filter is located between the roof prism and the first combined prism. Both sides of the signal light filter are coated with narrow-band filter films, and the side of the third parallelogram prism away from the lens is coated with a high-reflection film for the signal light.

5. The high extinction ratio fiber amplifier according to claim 4, characterized in that, The signal light filter is located between the dual-fiber collimator and the roof prism. The side of the signal light filter facing the dual-fiber collimator is coated with a film that reflects pump light and transmits signal light, and the other side is coated with a narrow-band signal light filter film. The side of the third parallelogram prism away from the lens is coated with a high-reflection film for signal light.

6. The high extinction ratio fiber amplifier according to claim 5, characterized in that, The signal light filter is located on the side of the second combined prism away from the lens. A reflector is also provided behind the signal light filter. A narrow-band signal light filter film is coated on the surface of the signal light filter facing the second combined prism. A signal light transmission film is coated on the side of the second combined prism away from the lens.

7. A method for operating the pump optical path of a high extinction ratio fiber amplifier, employing the high extinction ratio fiber amplifier as described in claim 4, characterized in that, The pump light from the pump source enters the second gain fiber through the combiner. After partial absorption in the second gain fiber, the remaining pump light is transmitted into the second double-clad fiber. After being collimated by the lens, it is input into the roof prism. The pump light is reflected by the plane of the roof prism and returns to the lens. The lens couples to the first double-clad fiber and then transmits to the first gain fiber.

8. A method for operating the amplified signal optical path of a high extinction ratio fiber amplifier, employing the high extinction ratio fiber amplifier as described in claim 4, characterized in that, The input signal light is amplified by the first stage of the first gain fiber and transmitted to the first double-clad fiber. After being collimated by the lens, it is incident on the roof prism. After being refracted by the roof prism, it becomes parallel collimated light. After passing through the signal filter, the signal light wavelength is transmitted, but the amplified spontaneous emission light is reflected. The transmitted signal light is incident on the side of the first parallelogram prism near the lens. After being reflected by the top surface of the first parallelogram prism, it is incident on the cemented surface of the first combined prism. It is then split into s-polarized signal light component 1 and p-polarized signal light component 2 by the polarization beam splitter in the cemented surface. The s-polarized signal light component 1 is reflected by the cemented surface and transmitted through the side of the first parallelogram prism away from the lens to the Faraday rotator. The Faraday rotator rotates the s-polarized signal light component 1 counterclockwise by 45 degrees. After passing through the half-wave plate, the rotated signal light is rotated clockwise by 45 degrees, and the signal light is transformed back into the s-polarized signal light component 1. It then enters the third parallelogram prism, passes through the side of the third parallelogram prism near the lens, is reflected by the top surface of the third parallelogram prism, is reflected again by the cemented surface of the second combined prism, and enters the side of the third parallelogram prism away from the lens. After being reflected by the side of the third parallelogram prism away from the lens, it returns to the half-wave plate along the original optical path. The s-polarized signal light component 1... The polarization direction of the signal light is rotated counterclockwise by 45 degrees before entering the Faraday rotator. The polarization direction of the rotated signal light is then rotated counterclockwise by another 45 degrees, thus becoming a p-polarized signal light component 1. The p-polarized signal light component 1 passes through the first parallelogram prism and the lens side and the cemented surface, then enters the second parallelogram prism. It is then transmitted through the second parallelogram prism near the lens side. After passing through the signal filter, the signal light wavelength is transmitted, but the amplified spontaneous emission light is reflected. The transmitted p-polarized signal light component 1 passes through the roof prism and enters the lens. It is coupled by the lens into the core of the second double-clad fiber and transmitted into the second gain fiber. After being amplified in the second stage, it is output by the combiner, thus realizing two-stage amplification of the signal light. The p-polarized signal light component 2 is transmitted through the cemented surface of the first combined prism, reflected by the bottom surface of the second parallelogram prism, and transmitted through the side of the second parallelogram prism away from the lens. It then enters the Faraday rotator, which rotates the p-polarized signal light component 2 counterclockwise by 45 degrees. After passing through the half-wave plate, the rotated signal light component 2 is rotated clockwise by 45 degrees, becoming p-polarized again. It then enters the isosceles right-angle prism, is transmitted through the side of the isosceles right-angle prism near the lens, and through the cemented surface of the second combined prism, before entering the third parallelogram prism. Reflected by the side of the third parallelogram prism away from the lens, it returns to the half-wave plate along its original path. The polarization of the p-polarized signal light component 2... After being rotated 45 degrees counterclockwise, the signal light is incident on the Faraday rotator. The polarization direction of the rotated signal light is then rotated 45 degrees counterclockwise again, thus becoming the s-polarized signal light component 2. The s-polarized signal light component 2 is transmitted through the side of the second parallelogram prism away from the lens, reflected from the bottom surface, reflected from the cemented surface, and transmitted out of the second parallelogram prism from the side closer to the lens. After passing through the signal filter, the signal light wavelength is transmitted, but the amplified spontaneous emission light is reflected. The transmitted s-polarized signal light component 2 is then incident on the lens after passing through the roof prism and coupled by the lens into the core of the second double-clad fiber. It is then transmitted into the second gain fiber and amplified in the second stage before being output by the combiner 4, thus realizing two-stage amplification of the signal light.

9. A method for directional light operation of a high extinction ratio fiber amplifier, wherein the high extinction ratio fiber amplifier according to claim 5 is characterized in that, The backlight generated by the amplification in the second gain fiber passes through the second double-clad fiber, is collimated by the lens to the roof prism, and is refracted into parallel collimated light after passing through the roof prism. It then enters the second parallelogram prism after passing through the signal filter. It is transmitted by the side of the second parallelogram prism close to the prism and is split into s-polarized signal light component 3 and p-polarized signal light component 4 by the polarization beam splitter on the cemented surface. The s-polarized signal light component 3 is successively reflected by the cemented surface of the second parallelogram prism, reflected by the bottom surface, and transmitted by the side away from the lens, and then incident on the Faraday rotator. The Faraday rotator rotates the s-polarized signal light component 3 counterclockwise by 45 degrees. After the rotation, the signal light passes through a half-wave plate and is rotated clockwise by 45 degrees. The signal light is then transformed back into the s-polarized signal light component 3 and incident on the isosceles right-angle prism. It is successively transmitted by the side of the isosceles right-angle prism near the lens, reflected by the cemented surface, and transmitted by the bottom surface, thus transmitting it outside the optical path of the amplifier, thereby achieving isolation of the reverse light. The p-polarized signal light component 4 is transmitted sequentially through the cemented surface of the first parallelogram prism and the side away from the lens, before entering the Faraday rotator. The Faraday rotator rotates the p-polarized signal light component 4 counterclockwise by 45 degrees. After passing through a half-wave plate, the rotated signal light is rotated clockwise by 45 degrees, and the signal light is transformed back into the p-polarized signal light component 4. It then enters the third parallelogram prism, is transmitted sequentially through the side near the lens, reflected from the top surface, and transmitted through the cemented surface, and finally transmitted from the bottom surface of the isosceles right-angle prism, thus transmitting it outside the optical path of the amplifier and achieving isolation of the reverse light.

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