阅读说明：本技术 一种光纤隔离器 (Optical fiber isolator ) 是由 任红艳 吴明 周士云 冷雨欣 刘志文 刘家顺 蔡一鸣 周士安 于 2021-09-10 设计创作，主要内容包括：本发明涉及一种光纤隔离器,包括放大模块、泵浦耦合模块、隔离模块；该放大模块包括增益光纤,第一准直器；泵浦耦合模块包括第一无源光纤,第二准直器；隔离模块包括第一偏振分光棱镜、法拉第旋光器、1/2玻片、第二偏振分光棱镜、第三准直器,以及第二无源光纤。信号光经过增益光纤在泵浦激励下,被放大,放大光经过隔离模块。该光纤隔离器集成了泵浦反向耦合、放大和隔离功能,其结构减少了光纤合束器无源光纤的使用,减少熔接点,损耗小,提高了系统的集成度和稳定性；同时减少了脉冲激光传输光纤的长度,减小非线性效应,优化了脉冲光纤激光放大特性和放大结构。(The invention relates to an optical fiber isolator which comprises an amplifying module, a pumping coupling module and an isolating module; the amplifying module comprises a gain optical fiber and a first collimator; the pump coupling module comprises a first passive fiber and a second collimator; the isolation module comprises a first polarization beam splitter prism, a Faraday rotator, 1/2 glass slides, a second polarization beam splitter prism, a third collimator and a second passive optical fiber. The signal light is amplified under the pump excitation through the gain fiber, and the amplified light passes through the isolation module. The optical fiber isolator integrates the functions of pump reverse coupling, amplification and isolation, reduces the use of passive optical fibers of an optical fiber combiner, reduces welding points, has low loss and improves the integration level and stability of a system; meanwhile, the length of the pulse laser transmission optical fiber is reduced, the nonlinear effect is reduced, and the laser amplification characteristic and the amplification structure of the pulse optical fiber are optimized.)

1. An optical fiber isolator is characterized by comprising an amplifying module, a pumping coupling module and an isolating module, wherein the amplifying module, the pumping coupling module and the isolating module are used for pulse laser amplification, pumping coupling and isolation protection;

the amplification module comprises a gain optical fiber and a first collimator;

the pump coupling module comprises a passive optical fiber and a second collimator;

the isolation module comprises a first polarization beam splitter prism, a Faraday rotator, 1/2 glass slides, a second polarization beam splitter prism and a third collimator; the first polarization beam splitter prism and the second polarization beam splitter prism are respectively positioned at two ends of the Faraday rotator, and the 1/2 glass slide is positioned between the Faraday rotator and the second polarization beam splitter prism.

2. The fiber isolator of claim 1, wherein the gain fiber is connected to the first collimator, and the signal light enters the isolation module through the first polarization splitting prism.

3. The fiber isolator of claim 2, wherein signal light passing through the gain fiber enters the isolation module directly in space.

4. The fiber isolator of claim 1, wherein the second collimator has an input end connected to the passive fiber and an output end connected to the second polarization splitting prism.

5. The optical fiber isolator as claimed in claim 4, wherein the pump light passing through the second collimator is incident on the second polarization splitting prism, reflected, and then reversely coupled into the gain fiber via the 1/2 glass slide, the Faraday rotator, and the first polarization splitting prism in sequence.

6. The fiber isolator of claim 1, wherein the faraday rotator rotates the polarization direction of reflected light by 45 ° with respect to incident light.

7. The fiber isolator of claim 1, wherein the 1/2 slide rotates the polarization direction of the light to a polarization direction that the second polarization splitting prism can pass through.

8. The optical fiber isolator according to claim 1, wherein the pump coupling module further comprises a dichroic lens, the dichroic lens is disposed between the amplifying module and the isolating module, the pump light passes through the second collimator, the dichroic lens and the first collimator in sequence, and is reversely coupled to enter the gain fiber, the gain fiber is connected to the first collimator, and the signal light enters the isolating module through the dichroic lens.

9. The fiber isolator of any one of claims 1 to 8, wherein the output of the fiber isolator is a fiber output or a spatial output.

10. The fiber isolator of claim 9, wherein the spatial output is a collimated beam spread output.

Technical Field

The invention belongs to the field of laser devices, and particularly relates to an optical fiber isolator.

Background

In an optical fiber laser oscillation or amplification system, in order to prevent the amplified energy from reflecting back to cause the damage of the devices at the front stage or form self-oscillation, an optical fiber isolator is generally used for optical isolation protection to prevent the energy at the rear stage from reflecting back to the front stage.

Referring to fig. 1, in a conventional fiber laser and amplification system, a fiber combiner (cladding pump) or a wavelength division multiplexer (core pump) is generally used to couple pump light into a gain fiber for amplification, and then an optical fiber isolator is used to perform isolation protection. However, whether the beam combiner or the wavelength division multiplexer is used as a passive optical coupling device, various losses (caused by loss conditions such as numerical aperture deformation, end face mismatching, fusion point loss, bending loss, process defects and the like) are inevitably introduced in the manufacturing and using processes, so that the loss of optical power input from each arm is caused, the loss in an optical path is further caused, the system is complex, the integration level is low, and meanwhile, the system loss is increased due to multiple melting points among optical fiber devices.

The patent application No. CN201910098565.0, entitled bidirectional pump double-clad fiber laser amplifier with SBS inhibiting effect, discloses a bidirectional pump double-clad fiber laser amplifier with SBS inhibiting effect, which is characterized by comprising: the device comprises a laser seed source, an amplifier unit, a first optical fiber combiner, a first double-cladding active optical fiber, a cladding light stripper, a second double-cladding active optical fiber, a second optical fiber combiner, an optical fiber end cap and a pumping source; the laser seed source emits signal light, the seed light enters the fiber core of the first double-cladding active optical fiber through the amplifier unit and then enters the fiber core of the second double-cladding active optical fiber through the cladding light stripper; the pump light emitted by the pump source respectively enters the cladding of the first active fiber and the cladding of the second active fiber through the forward and backward coupling of the pump ends of the first fiber combiner and the second fiber combiner to realize bidirectional pumping; the double-clad active optical fiber absorbs the pump light to form population inversion, and gain is provided for the signal light; and amplifying the signal light, and outputting the amplified signal light through the signal end of the second optical fiber beam combiner and the optical fiber end cap. The defects are that optical fiber devices in an optical path are more, the system structure is still complex, and longer tail fibers are arranged at two ends of the device, so that the transmission distance of pulse laser is longer, the nonlinear effect is easily caused, and the pulse amplification is limited.

Therefore, a fiber isolator is needed to solve the above-mentioned problems of complex system structure and low integration level caused by many fiber devices, high melting point, large loss.

Disclosure of Invention

In view of the above, in order to solve the above problems, the present invention provides an optical fiber isolator, which integrates pump reverse coupling, amplification and isolation functions through an amplification module, a pump coupling module and an isolation module, and reduces the use of an optical fiber combiner and a passive optical fiber compared with the prior art, thereby achieving the beneficial effects of reducing a fusion point, reducing loss, and improving the integration level and stability of a system, and further solving the problems of more optical fiber devices, more melting points, large loss, complex system structure and low integration level in the prior art.

In order to achieve the above and other related objects, the present invention provides an optical fiber isolator, which includes an amplifying module, a pump coupling module and an isolation module, for pump coupling, pulse laser amplification and isolation protection; the amplification module comprises a gain optical fiber and a first collimator, and the input end of the first collimator is connected with the gain optical fiber; the pump coupling module comprises a passive optical fiber and a second collimator, and the input end of the second collimator is connected with the passive optical fiber; the isolation module comprises a first polarization beam splitter prism, a Faraday rotator, 1/2 glass slides, a second polarization beam splitter prism and a third collimator; the first polarization beam splitter prism and the second polarization beam splitter prism are respectively positioned at two ends of the Faraday rotator, and the 1/2 glass slide is positioned between the Faraday rotator and the second polarization beam splitter prism. The first polarization beam splitter prism, the Faraday rotator, the 1/2 glass slide, the second polarization beam splitter prism and the third collimator are sequentially arranged.

Furthermore, the gain fiber is connected with the first collimator, and the signal light enters the isolation module through the first polarization splitting prism.

Further, the signal light space passing through the gain fiber directly enters the isolation module.

And further, the pump light passing through the second collimator is incident to the second polarization beam splitter prism, reflected, and then passes through the 1/2 glass slide, the Faraday rotator and the first polarization beam splitter prism in sequence, and is reversely coupled to enter the gain fiber, so that the gain fiber is used in the middle of a fiber laser system, is suitable for a polarization-maintaining fiber core pumping amplification mode, and plays roles of coupling pumping, amplification and isolation.

Further, the pump coupling module further comprises a bicolor lens, the bicolor lens is arranged between the amplification module and the isolation module, and the pump light passes through the second collimator, the bicolor lens and the first collimator in sequence and is reversely coupled to enter the gain optical fiber.

Further, the gain optical fiber is connected with the first collimator, and the signal light enters the isolation module through the bicolor lens.

Further, the Faraday rotator rotates the polarization direction of the reflected light by 45 DEG with respect to the incident light.

Further, the 1/2 slide rotates the polarization direction of the light into a polarization direction that the second polarization splitting prism can pass through.

Further, the output of the optical fiber isolator is an optical fiber output, the output end of the third collimator is connected with the second passive optical fiber, the signal light is amplified under the pumping excitation of the pumping coupling module through the amplifying module, and the signal light is output through the second passive optical fiber connected with the third collimator.

Further, the output of the optical fiber isolator is spatial output, and the signal light is output through the third collimator in a collimating manner.

Furthermore, the spatial output is a collimated beam expanding output, the output end of the third collimator is connected with an integrated beam expanding lens, and signal light is output through the beam expanding lens connected with the third collimator, so that the collimated beam expanding output is realized.

Further, the integrated beam expander is disposed inside the integrated fiber isolator.

Furthermore, the gain fiber is a rare earth ion doped fiber, the concentration of rare earth elements doped in the fiber core of the fiber is in non-uniform distribution, and the concentration of the rare earth elements doped in the fiber core is low and high, so that the fiber core non-uniform doped fiber amplifier can effectively improve the amplification efficiency, inhibit ASE, reduce noise and improve the signal-to-noise ratio.

Furthermore, the material for realizing polarization rotation in the optical fiber isolator adopts TGG crystal.

As described above, the present invention provides an optical fiber isolator integrating the functions of coupling pumping, amplifying and isolating, which has the following advantages:

1. the optical fiber combiner is not adopted, various losses introduced by the optical fiber combiner are reduced, meanwhile, the loss of welding points and welding points is reduced, the number of optical fiber devices in an optical path is reduced, and the production cost is reduced.

2. By the aid of the amplifying module, the pumping coupling module and the isolating module, coupling, amplifying and isolating functions are integrated, the structure is simplified, integration level and stability of a system are improved, and loss and manufacturing cost are reduced.

3. The use of passive optical fibers among all devices is reduced, welding through the passive optical fibers is avoided, welding points are reduced, loss is reduced, the length of the pulse laser transmission optical fiber is reduced, the nonlinear effect is effectively reduced, and the laser amplification characteristic and the amplification structure of the pulse optical fiber are optimized.

4. The second collimator is connected to the second polarization beam splitter prism, so that the pump light passing through the second collimator is incident on the second polarization beam splitter prism and then reflected, and then passes through the 1/2 glass slide, the Faraday optical rotator and the first polarization beam splitter prism in sequence and is reversely coupled to enter the beneficial optical fiber.

5. The pump light passes through the second collimator, the two-color lens and the first collimator in sequence through the two-color lens of the pump coupling module, and is reversely coupled into the gain optical fiber.

Drawings

FIG. 1 is a schematic diagram of a layout structure of a conventional device for laser pumping isolation;

FIG. 2 is a schematic structural diagram of an arrangement of an amplifying module, a pump coupling module and an isolating module according to a first embodiment of the present invention;

fig. 3 is a schematic structural diagram of another scheme of the amplifying module, the pump coupling module and the isolation module in the second embodiment of the present invention;

fig. 4 is a schematic diagram of an internal structure of an optical fiber output of a third embodiment of the present invention, in which an output end of a second collimator is connected to a second polarization splitting prism;

fig. 5 is a schematic diagram of an internal structure of an optical fiber output of the second collimator output end connected to the dichroic mirror according to the fourth embodiment of the present invention;

fig. 6 is a schematic diagram of an internal structure of a spatial output of a fifth embodiment of the present invention, in which an output end of a second collimator is connected to a second polarization splitting prism;

fig. 7 is a schematic diagram of an internal structure of a spatial output of a second collimator output end connected to a dichroic mirror according to a sixth embodiment of the present invention;

Detailed Description

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

It should be noted that, unless the directions indicated are individually defined, the directions of up, down, left, right, inner, outer, etc. referred to herein are based on the directions of up, down, left, right, inner, outer, etc. indicated in fig. 1 of the embodiments of the present application, and if the specific posture is changed, the directional indication is changed accordingly. The terms "plurality," "plurality," and "a number" mean two or more, and are used herein collectively to describe "first," "second," "third," and the like, and do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Further, in the various embodiments of the present disclosure, the same or similar reference numerals denote the same or similar components.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part, unless otherwise expressly stated or limited. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the scope of the present invention as claimed.

The invention provides an optical fiber isolator which is used as one of pulse optical fiber amplifier integrated components and is applied to an optical fiber laser system and an amplifying system to effectively amplify pulse laser.

Example one

As shown in fig. 2, the optical fiber isolator in the present embodiment includes an amplifying module, a pump coupling module, and an isolating module; the amplifying module comprises a gain optical fiber and a collimator 1 which are connected in sequence; the pump coupling module comprises a passive optical fiber 1 and a second collimator which are connected in sequence; the isolation module comprises a first polarization beam splitter prism (PBS1), a Faraday rotator (Core), a 1/2 glass slide, a second polarization beam splitter prism (PBS2), a third collimator and a passive optical fiber 2 which are connected in sequence; the pump coupling module is arranged at the rear end of the isolation module, is suitable for a polarization maintaining fiber core pump amplification mode, and plays roles of pump reverse coupling, amplification and isolation.

Example two

As shown in fig. 3, unlike the first embodiment, the pump coupling module in the optical fiber isolator in the present embodiment is disposed at the front end of the isolation module, and is suitable for core pumping and cladding pumping, and the pump light does not pass through the faraday rotator.

EXAMPLE III

As shown in fig. 4, on the basis of the first embodiment, the output mode of the optical fiber isolator in this embodiment is optical fiber output, that is, an on-line optical fiber isolator, which is generally used in the middle of an optical fiber laser system to perform the functions of coupling, pumping, amplifying, and isolating; the structure includes: a gain fiber, a collimator 1 (first collimator), a PBS1 (first polarization splitting prism), a Core (faraday rotator), a 1/2 glass slide, a PBS2 (second polarization splitting prism), and a collimator 2 (second collimator); wherein, the gain optical fiber, the collimator 1, the PBS1, the Faraday rotator, the 1/2 glass slide, the PBS2, the collimator 3 and the passive optical fiber 2 are connected in sequence; the passive optical fiber 1 is directly connected with the input end of the collimator 2, the output end of the collimator 2 is connected with the PBS2, and the amplified signal light is collimated by the collimator 3 and then output through the passive optical fiber 2. The first polarization beam splitter prism and the second polarization beam splitter prism are respectively positioned at two ends of the Faraday rotator, and the 1/2 glass slide is positioned between the Faraday rotator and the second polarization beam splitter prism.

It should be noted that the output end of the collimator 2 in this embodiment is connected to the PBS2, and is used in the middle of the fiber laser system, and is suitable for a polarization maintaining core pumping amplification mode, and plays roles of coupling pumping, amplifying, and isolating. Wherein, the pump light passes through the passive optical fiber 1, is collimated by the collimator 2, is reflected by the PBS2, then passes through the 1/2 glass slide and the Faraday rotator, and enters the gain optical fiber. The signal light passes through the gain fiber and is amplified under pump excitation. The PBS1 is mainly used to pass signal light and reflect pump light. The PBS2 is mainly used to pass signal light whose polarization is rotated after passing through the faraday rotator and 1/2 wave plate; the pump light is reflected after being collimated by the collimator 2 and incident on the PBS2, and is back-coupled into the gain fiber through the 1/2 wave plate, faraday rotator, PBS 1. 1/2 slide rotated the polarization direction of the light to the polarization direction that PBS2 could pass through; the faraday rotator rotates the polarization of the reflected light reflected by PBS2 by 45 degrees relative to the incident light.

The collimator converts the laser light into collimated light; the passive optical fiber is used for welding other optical fiber devices; furthermore, the collimator is an optical device for converting divergent light into parallel light, belongs to an optical element for input and output of an optical fiber communication optical device, and has a simple structure, the divergent light transmitted by an optical fiber is converted into parallel light (gaussian light beam) through a similar convex lens arranged in front, the collimator is used for coupling the light into a required device with maximum efficiency, so that the collimator has an important parameter: insertion loss, the existing process technology can reach below 0.15 dB; PBS is the english abbreviation of polarization splitting prism.

By using the technical solution of this embodiment, when the optical fiber isolator in this embodiment works, signal light is input into the amplification module, and passes through the gain optical fiber, the collimator 1, the PBS1, the faraday rotator, the 1/2 glass slide, and the PBS 2; the pump light is input into a pump coupling module, enters a collimator 2, a PBS2, a 1/2 glass slide, a Faraday rotator and a PBS1 through a passive optical fiber 1, and is reversely coupled and enters a gain optical fiber; the PBS1 reflects the pump light, and the signal light passes through the PBS2 and the collimator 3 in this order, and is output from the passive optical fiber 2 of the optical fiber isolator.

The optical fiber isolator in the embodiment couples, amplifies and isolates input signal light and pump light, and the input signal light and the pump light are output through the collimator 3 and the passive optical fiber 2, so that the coupling, amplification and isolation functions are directly integrated, the use of a conventional wavelength division multiplexer or beam combiner is reduced, the use number of optical fiber devices in the existing optical path is reduced, the optical fiber fusion points are reduced, the optical path loss is reduced, the system integration level and stability are improved, the structure is simple, and the manufacturing cost is effectively reduced.

Example four

The difference between this embodiment and the third embodiment is that, as shown in fig. 5, the pump coupling module in this embodiment further includes a two-color lens, the two-color lens is disposed between the amplification module and the isolation module, and the pump light passes through the second collimator, the two-color lens, and the first collimator in sequence, and is reversely coupled into the gain fiber. The gain optical fiber is connected with the first collimator, and the signal light enters the isolation module through the bicolor lens. Further, a bicolor lens is arranged between the first collimator (collimator 1) and the first polarization splitting prism (PBS1), and the bicolor lens is connected with the output end of the second collimator (collimator 2).

The two-color mirror has a reflection function and a projection function. The function of the bicolor lens is as follows: the pump light is coupled back through the dichroic mirror into the collimator 1 of the signal light and then into the gain fiber. The technical scheme of the embodiment is suitable for fiber core pumping and cladding pumping, and the pumping light does not pass through a Faraday optical rotator.

EXAMPLE five

The difference between the present embodiment and the third and fourth embodiments is that the signal output mode of the optical fiber isolator is different, and as shown in fig. 6, the signal output mode of the optical fiber isolator in the present embodiment is spatial output. Further, the spatial output is a collimated beam spread output.

It should be noted that, as can be seen from a comparison between fig. 4 and fig. 6, the spatial output fiber isolator in this embodiment is mostly used in a fiber laser system and an amplification system, and finally, the collimating and beam expanding output is directly performed through the collimator 3 and the beam expanding lens without installing the passive fiber 2, so as to perform the functions of coupling, pumping, amplifying, and isolating. And the optical fiber splicing device also reduces the use of the conventional wavelength division multiplexing or beam combiner, reduces the use number of optical fiber devices in the existing optical path, reduces optical fiber fusion points, reduces optical path loss, improves the integration level and stability of the system, has a simple structure, and effectively reduces the manufacturing cost.

EXAMPLE six

The difference between this embodiment and the fifth embodiment is that, as shown in fig. 7, a dichroic mirror is disposed between the first collimator (collimator 1) and the first polarization splitting prism (PBS1), and the dichroic mirror is connected to the output end of the second collimator (collimator 2).

It should be noted that the pump light is back-coupled into the collimator 1 of the signal light through the collimator 2 and the dichroic mirror, and then enters the gain fiber. The technical scheme of the embodiment is suitable for fiber core pumping and cladding pumping, and the pump light does not pass through a Faraday rotator.

In summary, the optical fiber isolator provided by the invention enables input signal light to be effectively amplified through the optical fiber isolator, pump light is coupled into the signal optical fiber through the optical fiber isolator and amplified through the passive optical fiber, passive optical fiber welding is not needed among the devices, coupling, amplifying and isolating functions are simultaneously integrated through the optical fiber isolator amplifying module, the pump coupling module and the isolating module, the use of a conventional wavelength division multiplexer or beam combiner is reduced, the use of the pump isolator is reduced, the use number of optical fiber devices is reduced, optical fiber welding points are reduced, the optical path loss is reduced, the system integration level and stability are improved, the structure is simple, and the manufacturing cost is effectively reduced. Meanwhile, the length of the laser transmission optical fiber can be shortened, the nonlinear effect is effectively reduced, and the laser amplification characteristic and the amplification structure of the pulse optical fiber are optimized. Compared with the prior art, the passive optical fiber of the optical fiber beam combiner is reduced, so that the beneficial effects of reducing welding points, reducing loss and improving the integration level and stability of the system are achieved, and the problems of more optical fiber devices, more melting points, high loss, complex system structure and low integration level in the prior art are solved.

Therefore, the fiber isolator provided by the invention integrates the functions of the coupler, the active fiber and the isolator, namely, the functions of coupling pumping, laser amplification and laser isolation transmission are realized, so that the length of the laser transmission fiber is reduced, the number of used devices is reduced, the laser amplification characteristic and the amplification structure of the pulse fiber are optimized, the nonlinear effect is reduced, the system integration level and stability are improved, the cost is reduced, and the application and the integration level of the conventional fiber isolator are expanded.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.