CN115963593A - Core-to-core distance converter of multi-core optical fiber and preparation method thereof - Google Patents

Abstract

The present disclosure relates to a core pitch converter for a multi-core optical fiber and a method of manufacturing the same. The core pitch converter includes: a fiber segment, the fiber segment comprising: a first end and a second end; and a plurality of cores formed within the fiber segment between the first and second ends and being waveguide structures formed via laser induction; wherein the plurality of cores have a first core pitch at the first end and a second core pitch at the second end, the first core pitch being different than the second core pitch. The core-to-core distance converter has the advantages of low loss, low manufacturing cost, good repeatability, simple and reliable structure and no time delay difference.

Description

Core-to-core distance converter of multi-core optical fiber and preparation method thereof

Technical Field

The present application relates to the field of optical fiber communication technology, and more particularly, to a core pitch converter for a multi-core optical fiber and a method of fabricating the same.

Background

With the continuous development of optical fiber communication technology, the supportable capacity of a common single-core single-mode optical fiber has approached the shannon limit, and the technology bottleneck is continuously increased. Space division multiplexing is widely considered to be the direction of next-generation optical fiber communication systems, and especially, a multi-core optical fiber technical path is more attractive in terms of engineering practice.

According to the difference of the fiber core spacing, the multi-core fiber can be divided into a weak coupling multi-core fiber, a random coupling multi-core fiber and a super-mode multi-core fiber. The fiber core interval of the weak coupling multi-core fiber is large, the modes carried by the fiber cores are independent, and the crosstalk of signals among the fiber cores is weak or even negligible. The distance between the cores of the super-mode multi-core optical fiber is small, the density of spatial channels is high, and the energy of the same mode is distributed in different cores; the different mode propagation constants differ greatly, resulting in large spatial modal dispersion (spatial modal dispersion accumulation is linear with transmission distance) and small crosstalk coupling between spatial modes. The core spacing of the random coupling multi-core fiber is between the weak coupling multi-core fiber and the super-mode multi-core fiber, the spatial channel density is high, and coupling crosstalk exists between the spatial modes, so that the spatial mode dispersion accumulation is in direct proportion to the root-mean-square of the transmission distance, the spatial mode dispersion is obviously lower than that of the super-mode multi-core fiber, and the MIMO demodulation complexity of a receiving end can be obviously reduced; in recent years, by designing a proper core interval and utilizing torsion in a drawing process, energy between different modes can generate more frequent random exchange in a transmission process, so that on one hand, modal dispersion is reduced by hundreds of times, on the other hand, loss difference of different modes is reduced to be negligible, and the random coupling multi-core optical fiber is closer to engineering application and is considered as the most competitive evolution direction.

For the transmission fiber, low loss (reducing ASE noise accumulation), large effective area (reducing nonlinear noise accumulation) and proper bending resistance are required, and the optimal core distance of the random coupling multi-core quartz fiber for long-distance transmission is between 18 and 25 mu m according to the research in the industry. However, for other optical functional modules, such as fiber amplifiers and optical branching multiplexers, it is desirable to process optical signals individually for each core, so as to avoid crosstalk between cores and the like. In order to achieve this function, it is necessary to insert a core-to-core converter between the transmission fiber and the optical function unit to achieve transition between, for example, a random coupling fiber and a weak coupling fiber.

Disclosure of Invention

It is an object of the present disclosure to provide a novel core-to-pitch converter and a method for manufacturing the same, which may overcome at least the technical problems of the prior art, including complex manufacturing, high losses and/or high costs.

According to a first aspect of the present disclosure, there is provided a core pitch converter for a multi-core optical fiber. The core pitch converter includes: a fiber segment, the fiber segment comprising: a first end and a second end; and a plurality of cores formed within the fiber segment between the first and second ends and being waveguide structures formed via laser inducement; wherein the plurality of cores have a first core pitch at the first end and a second core pitch at the second end, the first core pitch being different than the second core pitch.

Through the core spacing converter disclosed by the invention, the converter can be conveniently applied between multi-core optical fibers with different core spacings, so that the conversion of the different core spacings is realized. Due to the fact that the fiber core structure is generated through laser induction, the core-to-core distance converter has the advantages of being low in loss, low in manufacturing cost (good in repeatability), simple and reliable in structure and free of time delay difference.

In some embodiments, the first core pitch of the first end smoothly transitions to the second core pitch of the second end along an axial direction of the optical fiber segment. In still other embodiments, the core diameter or refractive index of at least one of the plurality of cores varies smoothly along an axial or radial direction of the optical fiber segment. In this smooth manner, the loss of light propagating in the core can be reduced.

In some embodiments, further comprising a first multi-core fiber segment having the first core pitch and a second multi-core fiber segment having the second core pitch, the first multi-core fiber segment being fusion spliced to the first end of the fiber segment; and the second multicore optical fiber segment is fusion spliced to the second end of the optical fiber segment. In such embodiments, using the first multicore fiber segment and the second multicore fiber segment may help extend the length of the core pitch converter. In particular, the first multi-core fiber segment and the second multi-core fiber segment may both be pigtails, which may facilitate optical coupling of the core pitch converter between multi-core fibers of different core pitches.

In some embodiments, the optical fiber segment is at least comprised of a silica glass material, such as alkali-doped metal ion fused silica glass.

According to a second aspect of the present disclosure, a method of fabricating a core pitch converter for a multi-core optical fiber is provided. The preparation method comprises the following steps: providing a section of coreless optical fiber including a first end and a second end; creating, via laser induction, a plurality of waveguide structures within a cladding of the coreless fiber section between the first end and the second end to form a plurality of fiber cores, wherein the plurality of fiber cores have a first core pitch at the first end and a second core pitch at the second end, the first core pitch being different than the second core pitch.

In some embodiments, creating a plurality of waveguide structures within the cladding via laser induction comprises: writing a plurality of waveguide structures within the cladding layer using a femtosecond, picosecond, or attosecond laser.

In some embodiments, creating a plurality of waveguide structures within the cladding layer via laser induction further comprises: controlling at least a focus position of the laser such that the first core pitch of the first end smoothly transitions to the second core pitch of the second end.

In some embodiments, creating a plurality of waveguide structures within the cladding layer via laser induction further comprises: controlling at least writing laser intensity and focus of the laser such that a core diameter or refractive index of at least one of the plurality of cores varies smoothly along an axial or radial direction of the optical fiber segment.

In some embodiments, the method further comprises: welding a first multi-core fiber segment to the first end and a second multi-core fiber segment to the second end prior to generating the plurality of waveguide structures within the cladding via laser induction.

In some embodiments, the method further comprises: after creating the plurality of waveguide structures within the cladding via laser induction, welding a first multi-core fiber segment to the first end, and welding a second multi-core fiber segment to the second end.

In some embodiments, the first multi-core fiber segment and the second multi-core fiber segment are both pigtails.

In some embodiments, the method further comprises: annealing the fiber segment after the plurality of waveguide structures are created within the cladding via laser induction.

According to a third aspect of the present disclosure, a light device is provided. The optical device includes the core-pitch converter according to the first aspect, or the core-pitch converter manufactured according to the manufacturing method of the second aspect.

According to a fourth aspect of the present disclosure, a communication system is provided. The communication system includes the core-to-core distance converter according to the first aspect, or the core-to-core distance converter prepared according to the preparation method of the second aspect.

Drawings

The above and other features, advantages and aspects of embodiments of the present disclosure will become more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings. In the drawings, like or similar reference characters denote like or similar elements, and wherein:

fig. 1 shows a schematic diagram of a first conventional solution for a core pitch converter;

FIG. 2 shows a schematic diagram of a structure of an etched clad butt-type fan-in fan-out device suitable for use in a first conventional approach;

fig. 3 shows a schematic structural view of a lens-coupled fan-in fan-out device suitable for the first conventional solution;

fig. 4 shows a schematic view of a lens-coupled core-pitch converter as an example of a second conventional technique;

fig. 5 shows a schematic diagram of a core pitch converter according to an example embodiment of the present disclosure;

fig. 6 illustrates an example flow diagram of a method of making a core-to-pitch converter in accordance with an example embodiment of the present disclosure;

FIG. 7 shows a fabrication example of a core pitch converter according to an example embodiment of the present disclosure;

fig. 8 shows another example of a preparation of a core pitch converter according to an example embodiment of the present disclosure; and

fig. 9 shows a schematic diagram of a fiber optic communication system in which a core-to-pitch converter according to an example embodiment of the present disclosure is applied.

Detailed Description

Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present disclosure are shown in the drawings, it is to be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather are provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the disclosure are for illustration purposes only and are not intended to limit the scope of the disclosure.

As described in the background, core-to-core converters have important applications in fiber optic communication systems. Fig. 1 shows a schematic diagram of a first conventional solution of a core pitch converter. The principle of this first conventional solution is to use two fan-in/fan-out devices to achieve the conversion of the core pitch. Specifically, as shown in fig. 1, the core pitch converter may include a first fan-in/fan-out FIFO 1 and a second fan-in/fan-out FIFO 2, wherein a first multi-core fiber having a first core pitch X may be connected to a second multi-core fiber having a second core pitch Y via both the first fan-in/fan-out FIFO 1 and the second fan-in/fan-out FIFO 2, thereby achieving conversion of the first core pitch X to the second core pitch Y.

There are a number of implementations of the fan-in/fan-out, with both etched fiber coupling and lens coupling schemes being common.

The principle of the etching optical fiber coupling scheme is that a single-core optical fiber corrodes the cladding of the optical fiber to a smaller diameter approximately equal to the core distance of the multi-core optical fiber in a chemical etching mode, then a plurality of corroded thin optical fibers are fixed together according to the arrangement mode of the multi-core optical fiber, wherein the end face fiber core is aligned with the connected multi-core optical fiber in a coupling mode, and the conversion between the multi-core optical fiber and the single-core optical fiber is achieved. By way of example, fig. 2 shows a schematic of a structure of an etched cladding butt-type fan-in fan-out device for implementing an etched fiber coupling scheme.

The principle of the lens coupling scheme is that single-core optical fibers are arranged in a geometric arrangement mode as multi-core optical fibers, and then the single-core optical fibers and the multi-core optical fibers are arranged through a group of lenses. As an example, fig. 3 shows a schematic of a lens-coupled fan-in fan-out device for implementing a lens coupling scheme.

The first conventional technical solution described above has the following disadvantages: a) Complicated process technologies such as micro-lens coupling and optical fiber etching are adopted, so that the inherent manufacturing cost of the device is high, and the batch manufacturing is difficult; b) In the aspect of performance, the ideal loss performance is difficult to achieve due to the limited device structure or process; c) A complex process is adopted, so that higher reliability risk is faced; d) Two FI/FO devices are butted, single-core optical fibers are butted through fusion welding, and time delay difference among channels is caused by the length difference of tail fibers.

The core pitch converter may also employ a second conventional solution of lens direct coupling. Fig. 4 shows a schematic diagram of a lens-coupled core-pitch converter as an embodiment of the second conventional technique. As shown in fig. 4, a lens 1 with a focal length f1 may be directly coupled to the multi-core fiber 1 with the first core pitch Y1, and a lens 2 with a focal length f2 may be directly coupled to the multi-core fiber 2 with the second core pitch, wherein the lens 1 may convert the output light of each core in the multi-core fiber 1 into parallel light; and the lens 2 may receive the parallel light from the output of the lens 1 and then focus the multi-core fiber 2 coupled to the second core pitch Y2, wherein a focal length f1/f2 of the lens 1 and the lens 2 may be designed to be approximately equal to a ratio Y1/Y2 of the core pitches of the multi-core fiber 1 and the multi-core fiber 2.

The second conventional technical solution overcomes the problem of delay inequality accumulation of the first conventional technical solution, but still has technical shortcomings or limitations, including: a) Complicated process technologies such as microlens coupling are adopted, which causes the inherent manufacturing cost of the device to be higher and the batch manufacturing to be difficult; b) In terms of performance, it is also difficult to achieve ideal loss performance, subject to device structure or process limitations; c) A complex coupling process is adopted, so that higher reliability risk is faced; d) In practical application, the effective area of the optical fiber with large core spacing is small, the effective area of the optical fiber with small core spacing is large, and due to the inherent limitation of the lens group amplification system (when the optical fiber with small core spacing passes through the lens group to expand the core spacing, the mode spot is also expanded), the mode field mismatch reason is difficult to achieve low coupling insertion loss.

It is an object of the present disclosure to provide a novel core-to-core converter, which has at least the advantages of low loss, low manufacturing cost (simple manufacturing process and good repeatability), simple and reliable structure, and no delay difference, so as to overcome or alleviate some of the disadvantages of the conventional technical solutions. The idea of the present disclosure is to use laser induced means to write a waveguide structure within a coreless fiber section, thereby creating a plurality of cores with variable pitch within the cladding, wherein the plurality of cores may have a first core pitch at a first end and a second core pitch at a second end, wherein the first core pitch is different from the second core pitch. In particular, the core pitch between the plurality of cores smoothly transitions from a first core pitch at the first end to a second core pitch at the second end along the axial direction of the optical fiber segment. In particular, the first core pitch may remain the same as a core pitch of a first multicore fiber to be butted to the first end, while the second core pitch may remain the same as a core pitch of a second multicore fiber to be butted to the second end.

As used herein, the term "smooth" means that the light has relatively little loss in the laser-induced waveguide so that it is not significantly attenuated to propagate.

For a better understanding of the structure of the core pitch converter of the present disclosure, fig. 5 shows a schematic diagram of a core pitch converter according to an example embodiment of the present disclosure.

As shown in fig. 5, the core-to-pitch converter 10 includes an optical fiber segment 20. For example only, the fiber segment 20 may have dimensions on the order of centimeters. Further, the optical fiber span 20 includes a first end 21 and a second end 22. In some embodiments, the fiber segment 21 may include only the cladding 23, and a plurality of cores 24, 25 formed within the cladding 23. By way of example, the cladding 23 may be formed of, for example, quartz glass (such as alkali-doped metal ion glass). In still other embodiments, the fiber segment 21 may further include a coating or jacket 26 formed on the outside of the cladding 23 for protecting the cladding 23 and the core structure therein. The sheath may be in the form of a heat shrink, for example. Here, fig. 5 shows two cores 24, 25 within the cladding 23, however, it should be understood that the number of multiple cores is merely an example and that in other embodiments there may be a greater number of cores.

Unlike conventional multi-core optical fibers, the plurality of fiber cores 24, 25 within the optical fiber segment 20 in the core pitch converter 10 of the present disclosure have a first core pitch at the first end 21 and a second core pitch at the second end 22, wherein the first core pitch is different from the second core pitch. As an example, the first core pitch may be, for example, a core pitch of 40um or more, and the second core pitch may be, for example, a core pitch in a range of 17 to 25 um.

While two cores are illustrated in fig. 5 as an example of a first core pitch at the first end and a core pitch at the second end, it should be understood that where more than two cores are included in the core segment 20, the first core pitch may be expressed as the core pitch of any two adjacent cores at the first end (assuming that the core pitch of any two adjacent cores is constant), or as the average core pitch of a plurality of cores at the first end, or as the average distribution density of a plurality of cores at the first end; and the second core pitch may be expressed as a core pitch of any two adjacent cores at the second end (assuming that the core pitch of any two adjacent cores is constant), or an average core pitch of the plurality of cores at the second end, or a distribution density representing the plurality of cores at the second end. Further, in some embodiments, the plurality of cores 24, 25 may gradually or smoothly transition from the first core pitch at the first end 21 to the second core pitch at the second end 22 in the axial direction within the optical fiber segment 20. In still other embodiments, the core diameter or refractive index of at least one of the plurality of cores may vary smoothly along the axial or radial direction of the optical fiber segment. The loss of light in the core can advantageously be reduced by the smooth design described above. It will be appreciated that with the single fiber segment 20 described above, conversion to different core pitches can be achieved.

More particularly, the formation of the multiple cores 24, 25 within the fiber segment 20 is different from the formation of the cores of conventional multicore fibers. Here, at least one of the plurality of cores 24, 25 is a waveguide structure formed by laser induction. In some embodiments, the refractive index profile of the waveguide can be controlled as a function of the axial position of the optical fiber segment by controlling the writing of the laser (e.g., controlling the intensity and/or focus of the writing laser). Here, the plurality of cores may be formed by irradiating the coreless fiber with laser light to induce a refractive index change in the cladding. In some embodiments, the laser may be generated using a laser such as a femtosecond or picosecond laser. In some embodiments, the output power, repetition frequency, scanning times, scanning position, scanning speed, and/or focusing spot size of the laser may be controlled according to the mode field of the fiber core of the multi-core fiber to be butted at two ends of the core-to-core distance converter to control the mode field of the waveguide to be written, so that the mode field thereof can be matched with the mode field of the fiber core of the multi-core fiber to be butted, thereby achieving lower device loss. In some embodiments, the plurality of cores may be formed sequentially by successive writing of a single laser beam. In still other embodiments, the multiple cores may even be formed simultaneously using the writing of multiple laser beams.

In some embodiments, in addition to the fiber segment 20 described above, the core-spacing converter 10 may further include a first multi-core fiber segment (not shown) and a second multi-core fiber segment (not shown) respectively butted against both ends of the fiber segment 20, wherein the first multi-core fiber segment may have a first core spacing, which may be fusion spliced to the first end 21 of the fiber segment; and the second multi-core fiber segment may have a second core pitch, which may be fusion spliced to the second end of the fiber segment. Further, the first multicore fiber segment and the second multicore fiber segment may both be pigtails. In this manner, the end of the core pitch converter may be integrated with a fiber optic connector, thereby facilitating optical coupling of the core pitch converter with other optical devices.

The specific structure of the core pitch converter 10 of the multi-core optical fiber of the present disclosure has been described above in detail. An exemplary method of manufacturing the core pitch converter 10 of the multi-core optical fiber will be described in detail below with reference to fig. 6.

As shown in fig. 6, the method 100 of manufacturing the core pitch converter 10 may include: at block 110, a coreless fiber segment is provided that includes a first end and a second end.

In some embodiments, the coreless fiber section may be a silica glass material, such as an alkali metal ion-doped silica glass material. In some embodiments, the provided coreless fiber segment may be a coreless fiber segment that includes only cladding; in still other embodiments, the provided coreless fiber segment may include, in addition to the cladding, a coating or jacket (e.g., a heat shrink) formed over the cladding. In embodiments where the provided coreless fiber section has a coating or jacket, the step of framing 110 may further include stripping the coating or jacket and cleaning.

At block 120, a plurality of waveguide structures are created within the cladding between the first end and the second end via laser induction to form a plurality of cores, wherein the plurality of cores have a first core pitch at the first end and a second core pitch at the second end, the first core pitch being different than the second core pitch.

In some embodiments, the writing of the waveguide structure described above to form the plurality of cores may be performed by a laser provided by a laser, such as a femtosecond or picosecond laser. For example, the mode field of the waveguide to be written can be controlled by controlling the output power, repetition frequency, scanning times, scanning position, scanning speed, and/or focused spot size of the laser, so that the mode field can be matched with the core mode field of the multi-core fiber to be spliced, thereby realizing lower device loss. In some embodiments, the plurality of cores may be formed sequentially by successive writing with a single laser beam. In still other embodiments, the multiple cores may even be formed simultaneously using the writing of multiple laser beams.

In some embodiments, the writing of the laser (e.g., controlling the intensity and/or focus of the writing laser) may be controlled such that the core diameter or refractive index of at least one of the plurality of cores varies smoothly along the axial or radial direction of the optical fiber segment. In some embodiments, the writing of the laser (e.g., the focal position/focal spot size of the laser) may be controlled such that the plurality of cores gradually or smoothly transitions axially from a first core pitch at the first end to a second core pitch at the second end. The loss of light in the core can be advantageously reduced by the above-described smoothing feature.

In still other embodiments, the preparation method 100 may further include: welding a first multicore fiber segment to the first end and a second multicore fiber segment to the second end prior to forming a plurality of waveguide structures within a cladding via laser induction. Alternatively, in still other embodiments, the preparation method 100 may further include: after forming a plurality of waveguide structures within the cladding via laser induction, a first multicore fiber segment is fusion spliced to the first end, and a second multicore fiber segment is fusion spliced to the second end. The solution of fusion bonding before the waveguide structure is formed can reduce the manufacturing cost increase caused by fusion bonding failure compared to the solution of fusion bonding after the waveguide structure is formed, but the challenge is that precise scan path planning/correction capability is required to achieve accurate butt joint between the cores.

In the above manner, the prepared core-to-pitch converter may thus comprise a first multi-core fiber segment and a second fiber segment. In particular, the first multi-core fiber segment and the second multi-core fiber segment may both be pigtails. It will be readily appreciated that a core-to-core converter with pigtails may be more convenient to implement connections between different optical devices.

In some embodiments, the above preparation method 100 may further include: after forming the plurality of waveguide structures, the fiber segment is annealed, which may help to enhance the stability of the written waveguide. In some embodiments, the above preparation method 100 may further include: the cladding of the fiber segment in which the plurality of waveguide structures or the plurality of cores are formed is coated to protect the cladding or otherwise protected (e.g., with a heat shrink). As an example, the coating layer may be an acrylic material, for example.

In order to better understand the method of manufacturing the core pitch converter of the present disclosure, an exemplary method of manufacturing the core pitch converter will be described below by referring to two examples of fig. 7 and 8. It should be understood that these two examples should not be construed as limiting the scope of the present disclosure in any way.

Example 1

Example 1 is a method for manufacturing a practical core-to-core pitch converter, and as can be seen from fig. 7, the method may include at least the following steps:

a) Stripping a coating layer and cleaning by using a section of alkali metal ion-doped fused quartz glass coreless optical fiber;

b) Fixing the cleaned coreless optical fiber on a workpiece table of a femtosecond direct writing system, and adjusting the position;

c) The high index waveguide is scanned and written on the planned path of the coreless fiber cladding by using a femtosecond laser (such as 1030nm, pulse with the magnitude of 200mJ, repetition frequency of more than 100 kHz) and focusing through an objective lens. The waveguide smoothly changes along the axial direction and the radial direction, and the loss is reduced. Controlling the mode field size of the written waveguide by controlling the output power, repetition frequency, scanning times, scanning position, scanning speed and/or focusing spot size;

d) Repeating the step c), and completing the writing of the plurality of fiber core waveguides;

e) Cutting one side of the written waveguide fiber, and welding the cut waveguide fiber with the tail fiber of the multi-core fiber (multi-core fiber 1) with the corresponding core interval; cutting the other side of the written waveguide fiber, and welding with the tail fiber of another multi-core fiber (multi-core fiber 2) with corresponding core spacing;

f) The exposed portion of the cladding is coated or otherwise protected (e.g., heat shrink).

It is easily understood that the core-to-core distance converter of the multi-core optical fiber of this example 1 is simple in manufacturing method and good in repeatability. In addition, no complex packaging is involved. Therefore, the method can be used for preparing the low-loss high-performance multicore fiber core spacing device in batch.

Example 2

This example 2 is another practical method for manufacturing a core-to-core pitch converter, and as can be seen from fig. 8, the method may include at least the following steps:

a) Stripping a coating layer and cleaning by using a section of alkali metal ion-doped fused quartz glass coreless optical fiber;

b) Cutting one side of the coreless fiber, and welding the coreless fiber with the multicore fiber 1 (for example, a pigtail); cutting one side of the coreless fiber, welding the coreless fiber with the multi-core fiber 2 (such as a tail fiber), and keeping the core arrangement of the multi-core fiber 1 and the multi-core fiber 2 parallel;

c) Fixing the welded coreless optical fiber on a workpiece table of a femtosecond direct writing system, and adjusting the position;

d) Focusing by using a femtosecond laser (such as 1030nm,200mJ pulse, repetition frequency of more than 100 kHz) through an objective lens, scanning and writing a high-refractive-index waveguide on a planned path of the coreless fiber cladding, and connecting the cores of the multicore fibers on two sides. Controlling the size of a mode field written into the waveguide by controlling the output power or the repetition frequency/the scanning times/the scanning position/the scanning speed/the size of a focusing light spot;

e) Repeating the step d) to complete the writing of the plurality of fiber core waveguides, thereby realizing the connection of the plurality of fiber cores;

f) The exposed portion of the cladding is coated or otherwise protected (e.g., heat shrink).

It is easy to understand that the method for manufacturing the core-to-core distance converter of the multi-core optical fiber of example 2 is also relatively simple and has good repeatability. At the same time, no complicated packaging is involved. Therefore, the method can be used for preparing the low-loss high-performance multi-core optical fiber core spacing device in batch. Furthermore, example 2 may also reduce the increase in manufacturing costs caused by fusion failures compared to example 1, but presents the challenge of requiring precise scan path planning/correction capabilities to achieve accurate interfacing between the cores.

As can be seen from the above description, the present disclosure can manufacture the core-to-pitch converter with low manufacturing cost, and at the same time, the core-to-pitch converter has low loss, simple and reliable structure, and does not introduce delay inequality.

It will also be understood that the core-to-pitch converter of the present disclosure may be incorporated into or included with other optical devices as part of the optical device. Furthermore, the core-to-core converter of the present disclosure may also be applied in an optical fiber communication system, thereby being a part of the optical fiber communication system.

Fig. 9 shows a schematic diagram of an exemplary optical fiber communication system in which a core-to-pitch converter according to an exemplary embodiment of the present disclosure is applied.

As shown in fig. 9, the exemplary optical fiber communication system (for convenience, only one transmission direction is shown) may include a plurality of optical termination multiplexing sites (OTM sites) and a plurality of optical amplification sites (OLA sites), wherein a core pitch converter may be applied to and form a part of the optical termination multiplexing sites or the optical amplification sites to realize conversion between different core pitches.

The structure and/or function of the optical terminal multiplexing station and the optical playback station will be briefly described below.

For example, an optical terminal multiplexing site may include an optical forwarding unit (TX 1 \8230; TXn is the transmit side of the optical forwarding unit, RX1 \8230; RXn is the receive side of the optical forwarding unit), a wavelength multiplexer/demultiplexer array, a fan-in/fan-out, a multi-core fiber amplifier, and a core pitch converter. The optical amplifier station may contain a multi-core fiber amplifier and a core pitch converter. And the stations are connected through the multi-core optical fiber. In particular, the core pitch of the multicore fibers employed between the respective sites may be different from the core pitch of the multicore fibers coupled at the input or output of the multicore fiber amplifier, and a core pitch converter may be disposed between the two, thereby performing the conversion of the core pitch.

The function of the optical forwarding function unit is to make the service signal be carried on the signal light with a specific wavelength. For a multi-core fiber transmission system, if the transmission fiber is a randomly-coupled/strongly-coupled multi-core fiber, it may adopt a spatial super-channel form (i.e., multiple subcarriers adopt the same wavelength and are input/output from different cores of the multi-core fiber), and at this time, a multi-input multi-output (MIMO) algorithm may be used on the receiving side to equalize crosstalk between carriers; if the transmission fiber is a weakly coupled multi-core fiber, it may be in a spatial super channel form (i.e., multiple subcarriers use the same wavelength and are input/output from different fiber cores), a frequency super channel form (i.e., the same fiber core is input and the subcarriers use different wavelengths), or a single carrier form.

The function of the wavelength multiplexer/demultiplexer is to multiplex or demultiplex signals of different wavelengths into or from a single mode optical fibre. The function of the fan-in/fan-out is to multiplex a plurality of single mode fibers into one multi-core fiber or to demultiplex individual cores from one multi-core fiber into different single mode fibers. The multicore fiber amplifier (multicore optical amplifier) functions to amplify optical signals in respective cores in a multicore fiber, and for example, in the scenario of fig. 9, the multicore optical amplifier may be referred to as a weakly coupled multicore fiber amplifier. Thus, no or negligible crosstalk is generated from core to core signals.

It is easily understood that by arranging the core-to-core converter of the present disclosure in the above optical fiber communication system, the optical fiber communication system to be applied may also sufficiently obtain the advantages brought by the core-to-core converter of the present disclosure, such as low loss and reduced delay inequality.

Various embodiments of the present disclosure have been described above in detail. It will be understood that the above-described embodiments are illustrative or exemplary only, and are not limiting; the present invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

Further, it should be understood that the above described flow is also only an example. Although the steps of a method are described in a particular order in the specification, this does not require or imply that all of the illustrated operations must be performed in the particular order to achieve desirable results, but rather that the steps depicted may be performed in an order that varies. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions.

In the claims, the word "comprising" does not exclude other elements, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain features are recited in mutually different embodiments or dependent claims does not indicate that a combination of these features cannot be used to advantage. The scope of protection of the present application covers any possible combination of features recited in the various embodiments or in the dependent claims, without departing from the spirit and scope of the application.

Furthermore, any reference signs in the claims shall not be construed as limiting the scope of the invention.

Claims (15)

1. A core pitch converter for a multi-core optical fiber, comprising:

a fiber segment, the fiber segment comprising:

a first end and a second end; and

a plurality of cores located within the fiber segment between the first and second ends and being waveguide structures formed via laser induction;

wherein the plurality of fiber cores have a first core pitch at the first end and a second core pitch at the second end, the first core pitch being different than the second core pitch.

2. The core-to-core converter of claim 1, wherein the first core pitch of the first end smoothly transitions to the second core pitch of the second end along an axial direction of the optical fiber segment.

3. The core-to-core converter of claim 1, wherein a core diameter or refractive index of at least one of the plurality of cores varies smoothly along an axial or radial direction of the optical fiber segment.

4. The core-spacing converter of claim 1, further comprising a first multi-core fiber segment having the first core spacing and a second multi-core fiber segment having the second core spacing,

the first multi-core fiber segment is fusion spliced to the first end of the fiber segment; and the second multi-core fiber segment is fusion spliced to the second end of the fiber segment.

5. The core-to-space converter of any one of claims 1-4, said fiber segment being composed of at least a silica glass material.

6. A method of making a core-to-pitch converter for a multi-core optical fiber, comprising:

providing a section of coreless optical fiber including a first end and a second end;

creating, via laser induction, a plurality of waveguide structures within a cladding of the coreless fiber section between the first end and the second end to form a plurality of fiber cores, wherein the plurality of fiber cores have a first core pitch at the first end and a second core pitch at the second end, the first core pitch being different than the second core pitch.

7. The method of claim 6, wherein generating a plurality of waveguide structures within the cladding via laser induction comprises: writing a plurality of waveguide structures within the cladding layer using a femtosecond, picosecond, or attosecond laser.

8. A method of manufacturing as defined in claim 7, wherein generating a plurality of waveguide structures within the cladding via laser induction further comprises: controlling at least a focus position of the laser such that the first core pitch of the first end smoothly transitions to the second core pitch of the second end.

9. A method of making as defined in claim 7, wherein creating, via laser induction, a plurality of waveguide structures within the cladding layer further comprises: controlling at least writing laser intensity and focus of the laser such that a core diameter or refractive index of at least one of the plurality of cores varies smoothly along an axial or radial direction of the optical fiber segment.

10. The method of manufacturing according to claim 6, further comprising: welding a first multi-core fiber segment to the first end and a second multi-core fiber segment to the second end prior to generating the plurality of waveguide structures within the cladding via laser induction.

11. The method of manufacturing according to claim 6, further comprising: after creating the plurality of waveguide structures within the cladding via laser induction, welding a first multi-core fiber segment to the first end, and welding a second multi-core fiber segment to the second end.

12. The method in claim 10 or 11, the first and second multicore fiber segments each being a pigtail.

13. The production method according to any one of claims 6 to 11, further comprising: annealing the fiber segment after the plurality of waveguide structures are created within the cladding via laser induction.

14. A light device comprising the core-to-core distance converter according to any one of claims 1 to 5, or the core-to-core distance converter prepared by the preparation method according to any one of claims 6 to 13.

15. A communication system comprising the core-to-core converter according to any one of claims 1 to 5 or the core-to-core converter prepared by the preparation method according to any one of claims 6 to 13.

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