Space-integrated mixed pumping injection multi-core optical fiber amplifier

Abstract

The invention discloses a spatially integrated multi-core optical fiber amplifier with mixed pumping injection. The multi-core rare earth doped optical fiber at least comprises more than two independent fiber cores; the multi-core collimation assembly is used for carrying out collimation coupling on multiple paths of signal light on the multi-core rare earth doped optical fiber; the pump light is obliquely injected into a fiber core and a cladding in the multi-core rare earth-doped optical fiber through the multi-core collimation assembly to form a bidirectional mixed pump mechanism, and the multi-mode optical fiber is connected with a pump laser; the spatial wavelength division multiplexing crystal is located at the intersection of a signal light path and a pump light path; and the spatial optical platform is used for integrally installing the multi-core collimation assembly and the spatial wavelength division multiplexing crystal. Core pump light is injected into the fiber core area of the multi-core rare earth-doped optical fiber, and the cladding is injected backwards after the pumping light reflecting mirror, so that collaborative coverage of a forward core pump and a backward cladding pump is realized, a mixed pumping scheme which is asymmetrical in space and complementary in light path is formed, and the coverage uniformity and the absorption utilization rate of pump light in each amplification channel are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber amplifiers, and in particular to a spatially integrated hybrid pump-injected multi-core optical fiber amplifier. Background Art

[0002] As fiber-optic communication systems evolve toward ultra-large capacity and ultra-high channel density, multi-core fiber (MCF) has gradually become a viable gain medium to enhance channel expansion capabilities. By integrating multiple independent cores within a single fiber, MCF enables parallel transmission and processing of multiple signals within a single module. However, existing technologies still rely on complex side-coupled pumping or fused structures, which are limited in terms of pumping efficiency, structural complexity, and optical path stability. Furthermore, they fail to combine the advantages of core pumping and cladding pumping, making it difficult to achieve multi-channel amplification balance and system integration optimization. In terms of pumping efficiency, the side-coupled structure usually introduces the pump light into the cladding region through the side wall or outer cladding of the optical fiber. The pump light propagates in the cladding in a non-directional manner, resulting in low energy utilization. The fused structure, on the other hand, will destroy the optical fiber structure and ion concentration changes at high temperatures, which is prone to mode mismatch and loss. In terms of structural complexity, the side-coupling structure requires precision machining of the fiber sidewall or the addition of waveguide patches, which places high demands on manufacturing accuracy and mechanical strength, resulting in complex processes and low yields. The fused taper method requires fusing the multi-core fiber with the pump fiber under high-temperature conditions, placing extremely high demands on the consistency of the multi-core arrangement, alignment accuracy, and process window, making it difficult to integrate and mass-produce on a large scale. In addition, most traditional pump coupling methods are based on injection into the internal structure of the optical fiber, which cannot achieve modular and maintainable spatial integration design. Often, a multi-core optical fiber contains 4, 7, 19 or even more cores, and the core spacing is generally only 30~50 μm. This requires that the spatial light beam must be accurately aligned with the center of each core one by one, otherwise it is very easy to cause differences in coupling efficiency and signal mismatch between channels. However, existing spatial collimation systems generally use multiple independent microlenses or manual fine-tuning brackets, which not only have low alignment efficiency, but are also easily affected by factors such as thermal drift, platform vibration, and installation errors. Any slight offset in the optical path will disrupt the geometric matching of the overall collimation structure; The difficulty in combining signal and pump light stems from the fact that traditional wavelength division (WDM) devices are not designed for the parallel combining of multiple spatial beams. Conventional WDM components are mostly based on single-beam coupling designs (such as fiber-based or single-beam spatial types), making it difficult to cope with the angular differences, positional offsets, and inconsistent spot shapes between multiple signal beams and pump light in space. This is especially true in multi-core systems, where each signal beam must spatially overlap and match the spot of the same pump beam. Any deviation in angle or incident position can lead to pump energy concentration in certain fiber cores, deviated combined spot, and increased coupling loss. The reflective surface size, bandwidth, and reflection / transmission efficiency of WDM crystals are prone to "edge effects" or uneven reflection distribution in multi-beam operation, making it difficult to maintain efficient and stable spatial combining in a multi-core structure, becoming another core bottleneck affecting system performance. To this end, a spatially integrated hybrid pump-injected multi-core fiber amplifier is proposed, in which the multi-core signal light and the pump light are coupled into the multi-core fiber through spatial collimation, and the core pump and the packet pump are hybrid pumped at the same time to improve the pumping efficiency and amplification performance. Summary of the Invention

[0003] The purpose of the present invention is to solve the above problems and to provide a spatially integrated hybrid pump-injected multi-core fiber amplifier.

[0004] In order to achieve the above-mentioned objectives, the present invention provides the following technical solution: a spatially integrated hybrid pump-injected multi-core fiber amplifier, characterized in that it includes a multi-core rare-earth-doped fiber containing at least two independent fiber cores, a multi-core collimation component for collimating and coupling multi-path signal light on the multi-core rare-earth-doped fiber, a multimode fiber for obliquely injecting pump light into the core and cladding of the multi-core rare-earth-doped fiber through the multi-core collimation component to form a bidirectional hybrid pumping mechanism and connected to a pump laser, a spatial wavelength division multiplexing crystal located at the intersection of the signal light path and the pump light path, and a spatial optical platform for integrating and mounting the multi-core collimation component and the spatial wavelength division multiplexing crystal.

[0005] Preferably, after the pump light and the signal light are collimated and combined in space, their axial overlap distance is not less than 20 mm to ensure the stability and coupling efficiency of the two beams before entering the multi-core rare-earth-doped optical fiber, and a centrally symmetrical collinear structure is adopted, with a central axis deviation of less than ±50 μm.

[0006] Preferably, the pump light includes core pump light entering the core of the multi-core rare-earth doped optical fiber and cladding pump light entering the cladding after being reflected by a spatial wavelength division multiplexing crystal.

[0007] Preferably, the core pump laser and the packet pump laser come from pumping paths in different directions, wherein the core pump light is injected forward in the same direction as the signal light to preferentially excite the core region, while the packet pump light is injected backward into the cladding of the multi-core rare-earth-doped optical fiber through a spatial wavelength division crystal or a reflector to provide backward energy compensation, thereby achieving composite gain excitation of the core and cladding in two directions.

[0008] Preferably, the cladding pump light is injected at an inclined angle and forms a reflective optical path in the cladding, covering the entire gain section cladding structure, and its injection angle range is 15° to 45° to enhance the backward pumping uniformity; and the axial incidence deviation of the core pump beam is less than ±0.5° to ensure colinearity and efficient coupling with the signal beam.

[0009] Preferably, the multi-core collimation assembly includes a multi-channel spherical microlens array or a cylindrical Glan lens array that matches the core arrangement in the multi-core rare-earth-doped optical fiber, for achieving spatial beam collimation and efficient coupling of multiple signal channels.

[0010] Preferably, the angle between the reflection surface of the spatial wavelength division multiplexing crystal and the signal light path is 45°±5°, and a reflectivity greater than 99% is achieved at a wavelength of 980 nm or 1480 nm through high-reflection coating.

[0011] Preferably, the multi-core rare earth doped optical fiber comprises a 4-core, 7-core or 19-core structure, the center distance between any two cores is not less than 30 μm to maintain optical isolation, and the cladding numerical aperture NA is greater than 0.36 to enhance the cladding pump light capture rate.

[0012] Preferably, the length of the spatial optical platform does not exceed 120 mm, the overall thermal drift is controlled within ±0.5°C, and an aluminum alloy or ceramic substrate is used to enhance thermal stability.

[0013] The beneficial effects of the present invention are as follows: by integrating the spatial wavelength division multiplexing crystal and the multi-core collimation component on the spatial optical platform, the integrated modular installation is improved; The core pump light is collimated by the multi-core collimation component and injected forward into the core area of ​​the multi-core rare-earth-doped optical fiber in the same direction as the signal light. The packet pump light is backward injected into the cladding of the multi-core rare-earth-doped optical fiber through the spatial wavelength division crystal or reflector, thereby realizing the coordinated coverage of the forward core pump and the backward packet pump, forming a hybrid pumping scheme that is spatially asymmetric and complementary in the optical path, and enhancing the coverage uniformity and absorption utilization rate of the pump light in each amplification channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the structure of the spatially integrated multi-core optical fiber amplifier system of the present invention.

[0015] Figure 2This is a structural diagram of the combination of a multi-core collimator component and a wavelength division multiplexing crystal according to the present invention.

[0016] Figure 3 Schematic diagram of the pump injection package of the present invention.

[0017] Figure 4 Schematic diagram of the pump injection of the core pump of the present invention.

[0018] Figure 5 This is a schematic diagram of the cross-sectional structure of the four-core rare earth-doped multi-core optical fiber used in the present invention.

[0019] Legend: 1. Multi-core rare-earth-doped optical fiber; 2. Multi-core collimation assembly; 3. Multimode optical fiber; 4. Spatial wavelength division multiplexing crystal; 5. Spatial optical platform; 6. Core pump light; 7. Packet pump light; DETAILED DESCRIPTION

[0020] Next we combine Figure 1-Figure 5 The spatially integrated hybrid pump-injected multi-core optical fiber amplifier of the present invention is further described.

[0021] It should be noted that all directional indications in the embodiments of the present invention, such as up, down, left, right, front, back, etc., are only used to explain the relative position relationship, movement status, etc. between the various components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0022] See Figure 1-Figure 5 As shown, a spatially integrated hybrid pump-injection multi-core fiber amplifier is characterized by comprising a multi-core rare-earth-doped optical fiber 1 comprising at least two independent optical cores, a multi-core collimation assembly 2 for collimating and coupling multi-path signal light on the multi-core rare-earth-doped optical fiber 1, a multimode optical fiber 3 for obliquely injecting pump light into the core and cladding of the multi-core rare-earth-doped optical fiber 1 through the multi-core collimation assembly 2 to form a bidirectional hybrid pumping mechanism and connected to a pump laser, a spatial wavelength division multiplexing crystal 4 located at the intersection of the signal light path and the pump light path, and a spatial optical platform 5 on which the multi-core collimation assembly 2 and the spatial wavelength division multiplexing crystal 4 are integrally mounted. By integrally mounting the spatial wavelength division multiplexing crystal 4 and the multi-core collimation assembly 2 on the spatial optical platform 5, the integrated modular installation is improved. The core pump light 6 is collimated through the multi-core collimation component 2 and injected forward into the core area of ​​the multi-core rare-earth-doped optical fiber 1 in the same direction as the signal light. The packet pump light 7 is backward injected into the cladding of the multi-core rare-earth-doped optical fiber 1 through the spatial wavelength division crystal or the reflector, thereby realizing the coordinated coverage of the forward core pump and the backward packet pump, forming a spatially asymmetric and complementary hybrid pumping scheme on the optical path, and enhancing the coverage uniformity and absorption utilization rate of the pump light in each amplification channel.

[0023] After the pump light and the signal light are collimated and combined in space, the axial overlap distance is not less than 20 mm to ensure the stability and coupling efficiency of the two beams before entering the multi-core rare-earth-doped optical fiber 1. A centrally symmetrical collinear structure is adopted, and the central axis deviation is less than ±50 μm. The pump light includes core pump light 6 that enters the core of the multi-core rare-earth-doped optical fiber 1 and packet pump light 7 that enters the cladding after being reflected by the spatial wavelength division multiplexing crystal 4. By using the core pump light 6 to be injected into the core region along the signal propagation direction, and the packet pump light 7 to be injected into the optical fiber cladding region by adopting a reverse incidence method, irradiating and injecting the optical fiber cladding region at an inclined angle, the forward core pump and the backward packet pump are coordinated to form a spatially asymmetric and optically complementary hybrid pumping scheme. The pump light source can use typical pump wavelengths such as 980 nm and 1480 nm, and its divergence angle is controlled within 2°. The spot size and incident angle can be precisely matched according to the fiber cross-sectional parameters to ensure the stability and high coupling efficiency of the core-clad joint injection.

[0024] The core pump laser and the packet pump laser come from pumping paths in different directions, wherein the core pump light 6 is injected forward in the same direction as the signal light to preferentially excite the core region, while the packet pump light 7 is injected backward into the cladding of the multi-core rare-earth-doped optical fiber 1 through a spatial wavelength division crystal or a reflector to provide backward energy compensation, thereby achieving composite gain excitation of the core and cladding in both directions; The cladding pump light 7 is injected at an inclined angle and forms a reflective optical path in the cladding, covering the entire gain section cladding structure. The injection angle range is 15° to 45° to enhance the uniformity of backward pumping. The axial incidence deviation of the core pump light 6 is less than ±0.5° to ensure colinearity and efficient coupling with the signal light beam.

[0025] The multi-core collimation component 2 includes a multi-channel spherical microlens array or a cylindrical Glan lens array that matches the core arrangement within the multi-core rare-earth-doped optical fiber 1, and is used to achieve spatial beam collimation and efficient coupling of multiple signal channels; by utilizing the multi-core collimation component 2 to match the core arrangement within the multi-core rare-earth-doped optical fiber 1, spatial beam collimation and efficient coupling of multiple signal channels are achieved.

[0026] The angle between the reflection surface of the spatial wavelength division multiplexing crystal 4 and the signal light path is 45°±5°, and a reflectivity greater than 99% is achieved at a wavelength of 980 nm or 1480 nm through high-reflection coating.

[0027] The multi-core rare earth-doped optical fiber 1 includes a 4-core, 7-core or 19-core structure, and the center spacing between any two cores is not less than 30 μm; the center spacing between the cores is not less than 30 μm to maintain optical isolation, and the cladding numerical aperture NA is greater than 0.36 to enhance the capture rate of the cladding pump light 7.

[0028] The length of the spatial optical platform 5 does not exceed 120 mm, the overall thermal drift is controlled within ±0.5°C, and an aluminum alloy or ceramic substrate is used to enhance thermal stability.

[0029] In one embodiment, to enhance system stability, a high-precision temperature control module (temperature control accuracy ±0.3°C) and an inclination fine-tuning platform (adjustment accuracy 0.01°) can be integrated between the spatial wavelength division multiplexing crystal and the optical fiber end face to compensate for alignment errors caused by thermal drift and spatial posture changes, thereby ensuring long-term operational performance.

[0030] The use process of the present invention is as follows: first, multi-channel signal lights are collimated and coupled into each independent core of the multi-core rare-earth-doped optical fiber 1 through the multi-core collimation component 2, and then the pump laser outputs core pump light 6 through the multi-mode optical fiber 3 and the multi-core collimation component 2. The multi-channel signal light and the core pump light 6 are combined by the multi-core collimation component 2 and then injected into the core area of ​​the multi-core rare-earth-doped optical fiber 1 along the signal propagation direction. Then, the pump laser outputs packet pump light 7 through the multi-mode optical fiber 3 and the multi-core collimation component 2. The packet pump light 7 is reflected by the spatial wavelength division multiplexing crystal 4 and enters the cladding of the multi-core rare-earth-doped optical fiber 1, so that the core pump light 6 and the packet pump light 7 of the pump light act on the core and cladding at the same time, forming a core pump and packet pump mixed pumping mechanism, and then realizing stimulated radiation of rare earth ions in the multi-core rare-earth-doped optical fiber 1, realizing spatial parallel amplification of the signal light; finally, the signal light after multi-channel amplification is extracted and output through the output collimation component, realizing a high-gain, high-isolation, and highly integrated multi-core amplification process; Measured data show that with this coordinated pumping design, the pump light absorption ratios are: approximately 65% ​​in the core pump section, and over 85% of the remaining energy is absorbed by the envelope pump section, resulting in an overall pump utilization rate exceeding 88%. The gain deviation between multiple channels is controlled within ±0.3 dB.

[0031] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention falls within the protection scope of the present invention.

Claims

1. A spatially integrated hybrid pump-injected multi-core fiber amplifier, characterized by It includes a multi-core rare-earth-doped optical fiber containing at least two independent optical cores, a multi-core collimation component for collimating and coupling multi-path signal lights on the multi-core rare-earth-doped optical fiber, a multi-mode optical fiber for obliquely injecting pump light into the core and cladding of the multi-core rare-earth-doped optical fiber through the multi-core collimation component to form a bidirectional hybrid pumping mechanism and connected to a pump laser, a spatial wavelength division multiplexing crystal at the intersection of the signal light path and the pump light path, and a spatial optical platform for integrating the multi-core collimation component and the spatial wavelength division multiplexing crystal.

2. The spatially integrated hybrid pump-injection multi-core fiber amplifier according to claim 1, characterized in that: After the pump light and the signal light are collimated and combined in space, the axial overlap distance is not less than 20 mm to ensure the stability and coupling efficiency of the two beams before entering the multi-core rare-earth-doped optical fiber. A centrally symmetrical collinear structure is adopted, and the central axis deviation is less than ±50 μm.

3. The spatially integrated hybrid pump-injection multi-core fiber amplifier according to claim 2, characterized in that: The pump light includes core pump light entering the core of the multi-core rare earth doped optical fiber and cladding pump light entering the cladding after being reflected by the spatial wavelength division multiplexing crystal.

4. The spatially integrated hybrid pump-injection multi-core fiber amplifier according to claim 3, characterized in that: The core pump laser and the packet pump laser come from pumping paths in different directions, wherein the core pump light is injected forward in the same direction as the signal light to preferentially excite the core region, while the packet pump light is injected backward into the cladding of the multi-core rare-earth-doped optical fiber through a spatial wavelength division crystal or a reflector to provide backward energy compensation, thereby achieving composite gain excitation of the core and cladding in two directions.

5. The spatially integrated hybrid pump-injection multi-core fiber amplifier according to claim 4, characterized in that: The cladding pump light is injected at an inclined angle and forms a reflective optical path in the cladding, covering the entire gain section cladding structure. The injection angle range is 15° to 45° to enhance the backward pumping uniformity; and the axial incidence deviation of the core pump beam is less than ±0.5° to ensure colinearity and efficient coupling with the signal beam.

6. The spatially integrated hybrid pump-injection multi-core fiber amplifier according to claim 1, characterized in that: The multi-core collimation component includes a multi-channel spherical microlens array or a cylindrical Glan lens array that matches the core arrangement in the multi-core rare-earth-doped optical fiber, and is used to achieve spatial beam collimation and efficient coupling of multiple signal channels.

7. The spatially integrated hybrid pump-injection multi-core fiber amplifier according to claim 1, characterized in that: The angle between the reflection surface of the spatial wavelength division multiplexing crystal and the signal light path is 45°±5°, and a reflectivity greater than 99% is achieved at a wavelength of 980 nm or 1480 nm through high-reflection coating.

8. The spatially integrated hybrid pump-injection multi-core fiber amplifier according to claim 1, characterized in that: The multi-core rare earth doped optical fiber includes a 4-core, 7-core or 19-core structure, the center distance between any two cores is not less than 30 μm to maintain optical isolation, and the cladding numerical aperture NA is greater than 0.36 to enhance the cladding pump light capture rate.

9. The spatially integrated hybrid pump-injection multi-core fiber amplifier according to claim 1, characterized in that: The length of the spatial optical platform does not exceed 120 mm, the overall thermal drift is controlled within ±0.5°C, and an aluminum alloy or ceramic substrate is used to enhance thermal stability.

Images