A double-clad fiber pump return filter

Abstract

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

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber amplifiers and optical fiber lasers, and in particular to a double-clad optical fiber pump return filter. Background Art

[0002] Fiber amplification technology is a key technology in both fiber-optic communications and laser technology. Its emergence has made long-distance fiber-optic communications possible, significantly advancing the development of fiber-optic communications. Since its introduction into the industrial laser field, it has rapidly developed due to its excellent heat dissipation performance and maintenance-free optical path. It has been hailed as a revolutionary advancement in solid-state lasers.

[0003] The basic principle of fiber amplification is to dope an optical fiber with rare-earth ions, imparting stimulated absorption and emission characteristics to form a gain material. Pump light is then injected into the fiber, causing stimulated emission within the fiber, amplifying the signal light. Adding a resonant cavity to this structure creates a fiber laser. Typically, to achieve high optical quality, the signal light must be single-mode. However, due to its small numerical aperture and physical size, single-mode fiber struggles to carry high-energy pump light. Therefore, double-clad fiber was invented. This fiber has a core and two claddings: the core transmits the signal light, while the first cladding transmits the pump light, effectively resolving this issue.

[0004] In double-clad optical fibers, the dopant ions reside in the core. Pump light propagates within the first cladding and, due to waveguiding, travels back and forth through the core, where it is absorbed by the dopant ions. However, this structure can lead to incomplete absorption, resulting in residual pump power and poor output performance. In this case, a pump stripper is typically used to release the residual pump power. However, due to the high residual pump power and the resulting heat generation, pump strippers require a heat dissipation system, which is relatively bulky.

[0005] Some have attempted to coat the end faces of double-clad fibers to reflect the pump light back into the fiber, allowing the signal light to be output. This approach, while avoiding the effects of residual pump light, also increases pump efficiency. However, due to residual reflections from the multilayer dielectric film filter, this approach failed to achieve the required return loss for the signal light, rendering the system unstable and, therefore, unacceptable. Summary of the Invention

[0006] In view of this, the present invention discloses a double-clad fiber pump return filter. By introducing a triangular prism, the transmission angles of pump light and signal light are separated, so that the pump light can be reflected separately, effectively improving the utilization rate of the pump light, which is of great help in improving the conversion efficiency of fiber amplifiers and fiber lasers.

[0007] According to the purpose of the present invention, a double-clad fiber-pumped return filter is proposed, comprising an input fiber collimator, a triangular prism, a supporting glass tube, a filter, an output fiber collimator, and a bridge glass tube. The supporting glass tube is fixedly mounted in the middle of the bridge glass tube, and the triangular prism and filter are respectively fixedly mounted at both ends of the supporting glass tube. The input fiber collimator and the output fiber collimator are respectively inserted into the two ends of the bridge glass tube and fixed after optical adjustment. The input fiber collimator outputs a signal having two wavelengths. The two different wavelengths of the output signals enter the triangular prism and are dispersed at different angles. After reaching the filter, one wavelength is transmitted and the other is reflected. The transmitted wavelength is coupled into the output fiber collimator for output, and the reflected wavelength is re-coupled into the input fiber collimator.

[0008] Preferably, the optical fiber type of the input optical fiber collimator is a double-clad optical fiber, the core transmits signal light, the first cladding transmits pump light, and the two optical signals have different wavelengths.

[0009] Preferably, the optical fiber model of the output optical fiber collimator is a single-clad optical fiber.

[0010] Preferably, the outer diameter a of the input optical fiber collimator is smaller than the inner diameter b of the bridge glass tube, and b=1mm <a<b-0.1mm。

[0011] Preferably, the outer diameter d of the output fiber collimator is smaller than the inner diameter b of the bridge glass tube, and b=1mm <d<b-0.1mm。

[0012] Preferably, the outer diameter c of the supporting glass tube is smaller than the inner diameter b of the bridging glass tube, and b=0.2mm <c<b-0.01mm。

[0013] Compared with the prior art, the advantages of the double-clad fiber pump return filter disclosed in the present invention are:

[0014] (1) The dispersion effect of the triangular prism causes the signal light and pump light of different wavelengths to have different deflection angles. The two signal beams are then filtered, so that the signal light is coupled to the output single-clad fiber through the filter, and the pump light is reflected and coupled into the input double-clad fiber along the original path. Since the signal light and pump light have different transmission angles after passing through the triangular prism, when the pump light is reflected along the original path, the residual signal light will not be able to return to the input fiber along the original path, thereby achieving the purpose of improving the signal light return loss, effectively solving the system stability problem, and improving the conversion efficiency of the entire system.

[0015] (2) The solution of the present invention has a simple structure, low cost, and is easy to mass-produce, which is of great significance for promoting the progress of fiber amplification technology and fiber laser technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a structural diagram of a double-clad fiber pump return filter disclosed by the present invention.

[0018] In the figure: 1 - input fiber collimator; 2 - triangular prism; 3 - filter; 4 - output fiber collimator; 5 - support glass tube; 6 - bridging glass tube. Specific Embodiments

[0019] The following briefly describes the specific embodiments of the present invention in conjunction with the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0020] Figure 1 Illustrates a preferred embodiment of the present invention, which is analyzed in detail.

[0021] As Figure 1 shown, a double-clad fiber pump return filter includes an input fiber collimator 1, a triangular prism 2, a support glass tube 5, a filter 3, an output fiber collimator 4, and a bridging glass tube 6.

[0022] The support glass tube 5 is inserted into the bridging glass tube 6 and fixed in the middle position with glue. The outer diameter c of the support glass tube 5 is smaller than the inner diameter b of the bridging glass tube 6, and b - 0.2 mm < c < b - 0.01 mm. The triangular prism 2 and the filter 3 are respectively pasted at both ends of the support glass tube 5. The triangular prism 2 is an isosceles triangular prism 2 with dimensions of 1.4 x 1.4 x 0.6 mm, the apex angle α is 30°, and the material is N-SF11 glass from Schott. The filter 3 is a T1064R980 filter purchased from EOC.

[0023] The optical fiber of the input optical fiber collimator 1 uses the SM-GDF-6 / 125-M double-clad optical fiber of Coherent Corporation. The core transmits the signal light, and the first cladding transmits the pump light. The two optical signals have different wavelengths. The outer diameter a of the input optical fiber collimator 1 is smaller than the inner diameter b of the bridging glass tube 6, and b - 1mm < a < b - 0.1mm. The optical fiber of the output optical fiber collimator 4 uses the HI1060 single-clad optical fiber of Corning Corporation. The outer diameter d of the output optical fiber collimator 4 is smaller than the inner diameter b of the bridging glass tube 6, and b - 1mm < d < b - 0.1mm. The input optical fiber collimator 1 and the output optical fiber collimator 4 are respectively inserted into the bridging glass tube 6 from both ends of the bridging glass tube 6 and fixed after optical debugging. The 980nm optical signal is used to monitor and debug the reflection port so that the 980nm signal can return along the original path. Glue is used to fix the input optical fiber collimator 1 on the bridging glass tube 6. The 1064nm optical signal is used to monitor and debug the transmission port so that the 1064nm signal can be coupled into the output optical fiber. Glue is used to fix the output optical fiber collimator 4 on the bridging glass tube 6.

[0024] Assemble the above materials and conduct optical coupling debugging to finally obtain a double-clad fiber pumped return filter. The output signal of the input optical fiber collimator 1 has two wavelengths. The two output signals with different wavelengths enter the triangular prism 2 and have different deflection angles after dispersion. When reaching the filter 3, one wavelength passes through and the other wavelength is reflected. The transmitted wavelength is coupled into the output optical fiber collimator 4 for output, and the reflected wavelength is recoupled into the input optical fiber collimator 1. Since the signal light and the pump light have different transmission angles after passing through the triangular prism 2, when the pump light returns along the original path, the transmitted residual signal light cannot return along the original path, achieving the purpose of improving the return loss of the signal light.

[0025] The measured output coupling loss of the 1064nm signal light is 0.7dB, the return loss (RL) of the 1064nm signal light is 54dB, and the reverse coupling loss of the 980nm pump light is 0.4dB. The overall performance is excellent.

[0026] The above description of the disclosed embodiments enables those skilled in the art to implement and use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit and scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A double-clad fiber pump return filter, characterized in that: The optical fiber collimator comprises an input optical fiber collimator (1), a triangular prism (2), a supporting glass tube (5), a filter (3), an output optical fiber collimator (4), and a bridge glass tube (6); the supporting glass tube (5) is fixedly mounted in the middle position inside the bridge glass tube (6), and the triangular prism (2) and the filter (3) are respectively fixedly mounted at both ends of the supporting glass tube (5); the input optical fiber collimator (1) and the output optical fiber collimator (4) are respectively inserted into both ends of the bridge glass tube (6) and fixed after optical debugging; the optical fiber type of the input optical fiber collimator (1) is a double-clad optical fiber, the core transmits signal light, and the first cladding transmits pump light, and the two optical signals have different wavelengths; The optical fiber model of the output optical fiber collimator (4) is a single-clad optical fiber; the output signals of the two different wavelengths of the input optical fiber collimator (1) enter the triangular prism (2) and are deflected at different angles by the dispersion effect. After reaching the filter (3), the signal light is transmitted, the pump light is reflected, the transmitted wavelength is coupled into the output optical fiber collimator (4) for output, and the reflected wavelength is re-coupled into the input optical fiber collimator (1).

2. A double-clad fiber pumped return filter according to claim 1, characterized in that: The outer diameter a of the input optical fiber collimator (1) is smaller than the inner diameter b of the bridge glass tube (6), and b=1mm <a<b-0.1mm。 3. The double-clad fiber pumped return filter according to claim 1, characterized in that: The outer diameter d of the output optical fiber collimator (4) is smaller than the inner diameter b of the bridge glass tube (6), and b=1mm <d<b-0.1mm。 4. A double-clad fiber pumped return filter according to any one of claims 1 to 3, characterized in that: The outer diameter c of the supporting glass tube (5) is smaller than the inner diameter b of the bridging glass tube (6), and b=0.2 mm <c<b-0.01mm。

Images