Apparatus and method for connecting an optical fiber preform to a pressure supply system

Abstract

The present invention provides a device for connecting an optical fiber preform (FP) including a plurality of elongated holes to a pressure supply system (PSS), the device comprising: a. a first surface (FS) to which the end face at which the plurality of elongated holes of the optical fiber preform (FP) terminate is to be connected; b. a second surface including at least two ports (P1, P2) configured to be in fluid connection with the pressure supply system (PSS); and c. a channel system located within the device that connects the plurality of elongated holes at the first surface (FS) to the at least two ports (P1, P2) such that at least one elongated hole is connected to one port and at least one other elongated hole is connected to the other port, wherein the density of the at least two ports at the second surface is less than the corresponding density of the channel system at the first surface (FS).

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to European Application No. 19213094.6, filed on December 3, 2019, the entire content of which is incorporated herein by reference. Technical field

[0003] The present invention relates to an apparatus and method for connecting an optical fiber preform to a pressure supply system, the optical fiber preform including a plurality of elongated holes extending generally parallel to a longitudinal axis of the optical fiber preform. Background art

[0004] Solid - core optical fibers are generally known and widely used, for example, in data communication applications. Solid - core optical fibers can be designed for low - loss, single - mode transmission within the broadband transmission range of the optical fiber material (such as silica glass). So - called endless - single - mode guiding (ESM, i.e., all higher - order modes HOM are leaky while the fundamental LP01 mode is fully confined) is achieved in solid - core photonic crystal fibers (PCFs) by designing a cladding structure around the solid core, as Figure 1 shown in A (prior art), such that the diameter d of the channels in the cladding structure and their center - to - center spacing (pitch) Λ satisfy the geometric condition d / Λ < 0.41. However, due to the light guiding in a solid - fiber material, there are drawbacks in terms of increased data - transmission delay, optical nonlinear effects resulting in new optical frequencies, and relatively low damage thresholds.

[0005] Hollow - core photonic crystal fibers (HC - PCFs) have unique advantages over solid - core optical fibers due to their ability to guide light in non - solid - core regions (the non - solid - core regions are evacuated (hollow core), filled with gas or filled with liquid), leading to application areas such as low - latency data transmission, high - power beam delivery, gas - based nonlinear optical devices, and optical waveguides with ultra - low nonlinearity and chemical sensing. Depending on the physical guiding mechanism, HC - PCFs are typically divided into two types: hollow - core photonic - bandgap fibers (HC - PBFs) and hollow - core anti - resonant reflecting fibers (HC - AFs).

[0006] Figure 1 B to Figure 1 I (prior art) shows a selection of scanning electron micrographs of different types of conventional HC - PCFs. Figure 1 B and Figure 1C shows an HC-PBF that confines the mode in the central hollow core by means of a photonic bandgap in the cladding. These types of PCFs typically have relatively low losses (around <20 dB / km) at telecommunication wavelengths. However, due to the wavelength-specific effects of the photonic bandgap, they only guide light within a relatively narrow bandwidth (around <15 THz). Although generally HC-PBFs support HOMs, it has been shown that a bent HC-PBF can be effectively made single-mode by including "satellite" hollow cores in the cladding ( Figure 1 B). These satellites strongly suppress the HOMs in the core by being phase-matched with them, resulting in higher HOM losses. If a sufficiently small core is used, the HC-PBG can also be made truly single-mode within a narrow spectral range (around <7 THz), but this leads to difficulties in fabrication and significantly higher losses for the desired fundamental mode.

[0007] Figure 1 D to Figure 1 I shows the selection of HC-AF structures (i.e., optical fibers with guiding mechanisms) mainly based on the anti-resonant effect. Figure 1 D and Figure 1 E have a Kagomé-lattice cladding and Figure 1 F and Figure 1 G have a single (F) or nested (G) ring of anti-resonant elements (AREs). Figure 1 H shows an HC-AF with a square core and Figure 1 I depicts an HC-AF with guiding properties in the ultraviolet. Compared with HC-PBFs, the losses of HC-AFs are generally greater due to non-ideal confinement, but the transmission window is wider.

[0008] HC-PCFs are typically prepared from glass preforms during the fiber drawing process. The transverse structure of these preforms is similar to the transverse structure of the final fiber material, i.e., a plurality of elongated holes in a well-defined pattern that is generally parallel to the longitudinal axis of the fiber preform. During the drawing process, the transverse structure is scaled down from the original preform diameter (typically a few millimeters) to the diameter of the optical fiber (typically 100 microns to 500 microns). To prevent the collapse of the elongated holes during the fiber drawing process, the elongated holes are pressurized, as disclosed, for example, in EP3136143A1.

[0009] The drawback of the current drawing process is that connecting the plurality of elongated holes to a pressure supply system is a complex and time-consuming process. Summary of the Invention

[0010] In view of the above, it is an object of the present invention to provide an apparatus and method for connecting an optical fiber preform to a pressure supply system in a simple and rapid manner.

[0011] According to an embodiment of the present invention, there is provided an apparatus for connecting an optical fiber preform to a pressure supply system, the optical fiber preform including a plurality of elongated holes extending substantially parallel to a longitudinal axis of the optical fiber preform, the apparatus comprising:

[0012] a. a first surface to be connected to an end face of the optical fiber preform, the plurality of elongated holes terminating at the end face;

[0013] b. a second surface including at least two ports configured to be in fluid connection with the pressure supply system; and

[0014] c. a channel system located within the apparatus, the channel system connecting the plurality of elongated holes at the first surface to the at least two ports such that at least one of the plurality of elongated holes is connected to one of the at least two ports and such that at least one other of the plurality of elongated holes is connected to the other of the at least two ports,

[0015] wherein a density of the at least two ports at the second surface is less than a corresponding density of the channel system at the first surface.

[0016] By providing an apparatus having an integrally formed channel system and a first surface connected to the end face of the optical fiber preform, a complex structure of the optical fiber preform as disclosed, for example, in US2011 / 0121474A1 (in US2011 / 0121474A1, tubes having different lengths extending from the end face are used) and time-consuming operations such as connecting pressure tubes to elongated holes as disclosed in US2019 / 0135679A1 can be avoided. The density of the at least two ports at the second surface being less than the corresponding density of the channel system at the first surface has the advantage that more space is provided at the second surface for connecting the at least two ports to the pressure supply system and, for example, conventional connectors can be used. The density is defined as the number of ports or holes per unit surface area. In the embodiment, the channel system is configured such that the total number of ports at the second surface is distributed over a region larger than a region limiting its corresponding elongated holes.

[0017] In an embodiment, the second surface includes a first surface portion that is substantially opposite to the first surface and a second surface portion that extends substantially non-parallel to the first surface, and wherein at least one port is arranged at the first surface portion of the second surface and at least one other port is arranged at the second surface portion of the second surface. This can provide more space between the at least two ports because the ports are arranged at surface portions that extend in different directions and thus have different orientations.

[0018] In an embodiment, the end face of the optical fiber preform has a circular shape, the circular shape having a center and a radius, wherein the device has a longitudinal axis that coincides with the center of the optical fiber preform, wherein the second surface includes a first surface portion that is substantially opposite to the first surface and a second surface portion that extends substantially perpendicular to the first surface, and wherein at least one port is arranged at the second surface portion of the second surface at a distance from the longitudinal axis of the device that is greater than the radius of the optical fiber preform.

[0019] The optical fiber preform typically has a radius in the range of a few millimeters. By arranging the second surface portion at a distance from the longitudinal axis of the device that is greater than the radius of the optical fiber preform, more space can be obtained for connecting the ports to the pressure supply system.

[0020] In an embodiment, the device has a cylindrical shape, the cylindrical shape having the first surface as an end surface of the cylindrical shape, wherein the second surface includes a first surface portion that is an end surface of the cylindrical shape opposite to the first surface and a second surface portion that is a side surface of the cylindrical shape. Preferably, the cylindrical shape corresponds to a straight cylinder or a straight elliptical cylinder.

[0021] In an embodiment, the first surface is provided with one or more nozzles for cooperating with corresponding tubular elements that form elongated holes in the optical fiber preform. The advantages of the nozzles can be to improve the seal between the elongated holes and the channel system, and / or to improve the mechanical strength, and / or to simplify the alignment process between the first surface of the device and the end face of the optical fiber preform.

[0022] In an embodiment, the channel system occupies a cross-sectional area at a distance from the first surface that is larger than the cross-sectional area occupied by the channel system at the first surface. Such a diverging channel system allows additional space to be easily created for connecting the at least two ports to the pressure supply system.

[0023] In an embodiment, the device comprises an assembly of a plurality of device parts that are separately fabricated and assembled together to form the device. This is advantageous, for example, when a relatively complex channel system is desired or required while utilizing a relatively easy fabrication process, because these device parts can be easily fabricated and the complexity is obtained after assembly.

[0024] In an embodiment, the device comprises a stack of at least three device parts including the channel system that extends from the first surface, the stack of at least three device parts including a bottom device part, a top device part, and at least one intermediate device part, wherein the intermediate device part has one or more of the following features:

[0025] a. A port located at a side surface of the intermediate device part;

[0026] b. One or more unbranched channels extending through the intermediate device part;

[0027] c. Multiple channels combined into a single channel;

[0028] d. One or more channels that taper or otherwise have a changing cross-section, such that the size of the cross-section of the one or more channels increases toward the top device part side of the intermediate device part,

[0029] and wherein the bottom device part includes the first surface.

[0030] Feature a. above allows for easy fabrication of the port by easily incorporating the port located at the side surface of the device into the intermediate device part. Such a port can be fabricated, for example, as an opening that extends over the entire height of the intermediate device defined by adjacent device parts on the bottom side and the top side.

[0031] Feature c. above allows channels that need to be pressurized with the same pressure to be combined to reduce the number of ports required to connect the optical fiber preform to the pressure supply system.

[0032] Feature d. above allows, for example, increasing the cross-section of the channel to match the size of the port or the connection piece to the pressure supply system.

[0033] In an embodiment, the top device part includes a port disposed at a side surface of the top device part and / or a port disposed at a surface facing away from the at least one intermediate device part.

[0034] According to another embodiment of the present invention, a set of device parts is provided, which is configured to form two different configurations of the device according to the present invention, wherein at least one device part is used in both configurations, and wherein the two configurations may allow two different fiber preforms to be connected to the same pressure supply system, or may allow two identical fiber preforms to be connected to the pressure supply system in different ways. This allows the reuse of the device or at least a plurality of its parts for other fiber preforms or other pressure supply systems, or pressurizing the fiber preform in another way.

[0035] According to a further embodiment of the present invention, a method for connecting a fiber preform to a pressure supply system is provided, the fiber preform including a plurality of elongated holes extending substantially parallel to the longitudinal axis of the fiber preform, the method comprising the steps of:

[0036] a. attaching the end face of the fiber preform, at which the plurality of elongated holes terminate, to a first surface of a device according to the present invention; and

[0037] b. connecting the at least two ports to the pressure supply system.

[0038] In an embodiment, the end face of the fiber preform is attached to the first surface of the device using a sealant to provide a substantially airtight connection between the elongated holes in the fiber preform and the channel system of the device.

[0039] In an embodiment, the method comprises the steps of:

[0040] i. before step a., inserting a temporary blocking member into one or more of the elongated holes in the fiber preform, the temporary blocking member being configured to prevent blocking the passage between the channel system of the device and the corresponding elongated hole during step a.; and

[0041] ii. removing the temporary blocking member during or after step a.

[0042] In an embodiment, the device includes an assembly of a plurality of device parts that are separately prepared and assembled together to form the device, wherein step a. includes attaching the end face of the fiber preform to the device part including the first surface, and wherein step ii. is performed by the device part including the first surface before other device parts are connected to the device part including the first surface.

[0043] In an embodiment, the device is separated from a previously drawn fiber preform before step a. Description of the Drawings

[0044] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0045] - Figure 1 depicts a cross-section of a conventional solid or hollow core optical fiber (prior art);

[0046] - Figure 2 schematically depicts the connection between an optical fiber preform and a pressure supply system;

[0047] - Figure 3 schematically depicts an exploded view of an optical fiber preform and a device according to an embodiment of the present invention;

[0048] - Figure 4 schematically depicts Figure 3 a cross-sectional view of the device; and

[0049] - Figure 5 schematically depicts a cross-sectional view of a device according to another embodiment of the present invention. DETAILED DESCRIPTION

[0050] Figure 2 schematically depicts an optical fiber preform FP, the optical fiber preform FP including a plurality of elongated holes extending generally parallel to a longitudinal axis LA, the plurality of elongated holes being, for example, similar to Figure 1 any one of the examples B-I shown in. The plurality of elongated holes terminate at an end face of the preform FP, for example Figure 1 as shown for example B-I in.

[0051] Figure 2 schematically depicts how the optical fiber preform FP is connected to a pressure supply system PSS. To this end, a device D according to the present invention is provided, an example of the device D being explained in more detail hereinafter. The device D includes a first surface FS and a second surface, the first surface FS being connected to the end face at which the plurality of elongated holes of the optical fiber preform FP terminate, the second surface including a first surface portion FSP that is substantially opposite to the first surface FS, and a second surface portion SSP that extends between the first surface FS and the first surface portion FSP.

[0052] The first port P1 is arranged at the first surface portion FSP, and the first port P1 is connected to the pressure supply system PSS via a first fluid communication pipeline FL1. The second port P2 is arranged at the second surface portion SSP, and the second port P2 is connected to the pressure supply system PSS via a second fluid communication pipeline FL2. At least one of the plurality of elongated holes in the optical fiber preform FP is connected to the first port P1, and at least one other of the plurality of elongated holes is connected to the second port P2 via a channel system within the device D, examples of which will be explained in more detail hereinafter. Due to the channel system, these two ports P1, P2, and these two fluid communication pipelines FL1, FL2, different pressures can be provided to different elongated holes using the pressure supply system.

[0053] According to the present invention, the density of these two ports P1, P2 at the second surface is less than the corresponding density of the channel system at the first surface, as will be explained in more detail hereinafter. The density is defined as the number of channels per unit area of the surface. The first density may refer to the number of channels within the channel system per unit area at the first surface FS that are connected to holes, and the second density may refer to the number of ports per unit area at the second surface portion SSP that are connected to their corresponding one or more elongated holes.

[0054] Reference will be made to Figures 3 to 5 to describe exemplary embodiments of the device D suitable for use in Figure 2 embodiments.

[0055] Figure 3 and Figure 4 respectively schematically depict an exploded view and a cross-sectional view of a device D and an optical fiber preform FP according to an embodiment of the present invention. The optical fiber preform FP is schematically depicted as an outer tube OT surrounding four smaller inner tubes IT. Thus, the preform FP includes five elongated holes H1 to H5, namely four elongated holes H1 to H4 corresponding to these four inner tubes IT respectively, and an elongated hole H5 corresponding to the space between these four inner tubes IT within the outer tube OT.

[0056] The optical fiber preform FP has at least near the device D a cylindrical shape defined by the side wall SW of the outer tube OT and bounded at one end by an end face EF, which is also the face at which the elongated holes H1 to H5 terminate. Thus, the end face EF has a circular shape with a radius R and a center coinciding with the longitudinal axis LA of the preform FP.

[0057] The end face EF of the preform FP is connected to the device D. As can be seen inFigure 3 As can be clearly seen in the exploded view, the device D includes a bottom device part BD, a middle device part ID, and a top device part TD. The device D has a cylindrical shape with a longitudinal axis DLA such that these device parts BD, ID, TD form sections of the cylindrical shape, and these sections are stacked on top of each other to form the device D.

[0058] The bottom device part BD includes a first surface FS which is connected, for example using a sealant, to the end face EF of the optical fiber preform FP to provide a substantially airtight connection. The top device part TD includes a first surface part FSP which is opposite to the first surface FS and which is part of the second surface of the device D. These device parts BD, ID, TD all include a part of the second surface part SSP which extends between the first surface SP at the bottom device part BD and the first surface part FSP and which is part of the second surface of the device D.

[0059] The second surface of the device D includes a first port P1 and a second port P2 for connecting the device D to a pressure supply system. In this embodiment, the first port P1 is arranged at the first surface part FSP and the second port P2 is arranged at the second surface part SSP.

[0060] The first surface SF of the device D includes an opening O for each of the elongated holes H1 to H5, and these five openings O are connected via five corresponding channels of a channel system to the first port P1 or the second port P2, and only the channels CH1, CH3, and CH5 of these five corresponding channels are Figure 4 visible in

[0061] In this embodiment, the opening O associated with the inner tube IT is provided with a nozzle N to facilitate alignment with the holes H1 to H4 and to provide an airtight connection. The corresponding channels CH1, CH3 extend from the bottom device part BD through the middle device part ID to the top device part TD to be combined into a single channel SCH connected to the first port P1. The channel CH5 extends from the bottom device part BD to the middle device part ID, where the channel CH5 is connected to the second port P2. As a result, by applying different pressures to the first port P1 and the second port P2, the pressure in the inner tube IT can be different from the pressure in the hole H5.

[0062] Those skilled in the art will appreciate that the distance between the first port P1 and the second port P2 at the second surface of the device D can be greater than the distance between the openings O at the first surface FS of the device D. In other words, by making the density of the ports at the second surface less than the density of the channel system at the first surface FS, space is created for connecting the first port P1 and the second port P2 to the pressure supply system.

[0063] Figure 5 A cross-sectional view of a device D connected to an optical fiber preform FP identical to the optical fiber preform in the embodiment of Figure 3 and Figure 4 is depicted according to another embodiment of the present invention. To avoid unnecessary repetition, like reference numerals are used to indicate like components of the device D, and the description below focuses on the differences between the two embodiments, such that for the similarities, the description of the embodiment of Figure 3 and Figure 4 also applies to the embodiment of Figure 5

[0064] The main difference between the embodiments shown is that Figure 5 the device D in

[0065] has a cylindrical shape with a radius DR greater than the radius R of the optical fiber preform FP. Thereby, more surface area or surface region at the second surface of the device D can be used for ports, such as the first port P1 and the second port P2, allowing for an increase in the number of ports while generally maintaining the same port density, or increasing the size of the ports, or using larger connectors to connect the ports to the pressure supply system. Figure 3 and Figure 4 The intermediate device portion ID and the top device portion TD have a similar construction as compared to the embodiment of

[0066] Although the above embodiments have been described as having a limited number of elongated holes, a limited number of ports, and a limited number of device portions in the optical fiber preform to keep these examples simple and easy to understand, those skilled in the art will understand that any suitable number of elongated holes (such as those shown in Examples 1B to 1I), any suitable number of ports (depending on the pressure requirements during the drawing process), and any suitable number of device portions can be used in the optical fiber preform when necessary.

[0067] Although the above embodiments describe the device D as modular and made up of multiple device portions, a single-piece device D can also be used. Such a device D can be manufactured, for example, using 3D printing technology.

[0068] The features, drawings, and claims of the invention disclosed in the above description can be meaningful in separate, combined, or sub-combined ways to implement the invention in its different embodiments.

[0069] Additional embodiments of the invention are disclosed in the following numbered list of aspects:

[0070] 1. A device for connecting an optical fiber preform to a pressure supply system, the optical fiber preform including a plurality of elongated holes extending generally parallel to the longitudinal axis of the optical fiber preform, the device comprising:

[0071] a. A first surface to be connected to an end face of the optical fiber preform, the plurality of elongated holes terminating at the end face;

[0072] b. A second surface including at least two ports configured to be in fluid connection with the pressure supply system; and

[0073] c. A channel system located within the device, the channel system connecting the plurality of elongated holes at the first surface to the at least two ports such that at least one of the plurality of elongated holes is connected to one of the at least two ports and such that at least one other of the plurality of elongated holes is connected to the other of the at least two ports,

[0074] wherein the density of the at least two ports at the second surface is less than the corresponding density of the channel system at the first surface.

[0075] 2. The device according to aspect 1, wherein the second surface includes a first surface portion that is substantially opposite to the first surface and a second surface portion that extends substantially non-parallel to the first surface, and wherein at least one port is arranged at the first surface portion of the second surface and at least one other port is arranged at the second surface portion of the second surface.

[0076] 3. The device according to aspect 1 or 2, wherein the end face of the optical fiber preform has a circular shape, the circular shape having a center and a radius, wherein the device has a longitudinal axis that coincides with the center of the optical fiber preform, wherein the second surface includes a first surface portion that is substantially opposite to the first surface and a second surface portion that extends substantially perpendicular to the first surface, and wherein at least one port is arranged at the second surface portion of the second surface at a distance greater than the radius of the optical fiber preform from the longitudinal axis of the device.

[0077] 4. The device according to any one of aspects 1 to 3, wherein the device has a cylindrical shape, the cylindrical shape having the first surface as an end surface of the cylindrical shape, wherein the second surface includes a first surface portion that is an end surface of the cylindrical shape opposite to the first surface and a second surface portion that is a side surface of the cylindrical shape.

[0078] 5. The device according to aspect 4, wherein the cylindrical shape corresponds to a straight cylinder or a straight elliptical cylinder.

[0079] 6. The device according to any one of aspects 1 to 5, wherein the first surface is provided with one or more nozzles for matching corresponding tubular elements that form elongated holes in the optical fiber preform.

[0080] 7. The device according to any one of aspects 1 to 6, wherein the channel system occupies a cross-sectional area that is larger than the cross-sectional area occupied by the channel system at the first surface at a distance from the first surface.

[0081] 8. The device according to any one of aspects 1 to 7, wherein the device includes an assembly of a plurality of device parts that are separately prepared and assembled together to form the device.

[0082] 9. The device according to aspect 8, wherein the device includes a stack of at least three device parts that include the channel system and extend from the first surface, the stack of at least three device parts including a bottom device part, a top device part, and at least one intermediate device part, wherein the intermediate device part has one or more of the following characteristics:

[0083] a. A port located at a side surface of the middle device portion;

[0084] b. One or more unbranched channels extending through the middle device portion;

[0085] c. Multiple channels combined into a single channel;

[0086] d. One or more channels that taper, for example such that the dimensions of the cross-section of the one or more channels increase towards the top device portion side of the middle device portion,

[0087] and wherein the bottom device portion includes the first surface.

[0088] 10. The device according to aspect 9, wherein the top device portion includes a port arranged at a side surface of the top device portion and / or a port arranged at a surface facing away from the at least one middle device portion.

[0089] 11. A set of device portions configured to form two different configurations of the device according to any one of aspects 1 to 10, wherein at least one device portion is used in both configurations, and wherein the two configurations may allow two different fiber preforms to be connected to the same pressure supply system or may allow two identical fiber preforms to be connected to the pressure supply system in different ways.

[0090] 12. A method for connecting a fiber preform to a pressure supply system, the fiber preform including a plurality of elongated holes extending substantially parallel to the longitudinal axis of the fiber preform, the method comprising the steps of:

[0091] e. Attaching an end face of the fiber preform to a first surface of the device according to any one of aspects 1 to 10, the plurality of elongated holes terminating at the end face; and

[0092] f. Connecting the at least two ports to the pressure supply system.

[0093] 13. The method according to aspect 12, wherein the end face of the fiber preform is attached to the first surface of the device using a sealant to provide a substantially airtight connection between the elongated holes in the fiber preform and the channel system of the device.

[0094] 14. The method according to aspect 12 or 13, wherein the method comprises the steps of:

[0095] i. Prior to step a., insert a temporary blocking member into one or more elongated holes in the optical fiber preform, the temporary blocking member being configured to prevent blocking of the passage between the channel system of the device and the corresponding elongated hole during step a.; and

[0096] ii. During or after step a., remove the temporary blocking member.

[0097] 15. The method according to aspect 14, wherein the device is the device according to any one of aspects 8 to 10, wherein step a. comprises attaching the end face of the optical fiber preform to the device part comprising the first surface, and wherein step ii. is carried out by the device part comprising the first surface before the other device parts are connected to the device part comprising the first surface.

[0098] 16. The method according to any one of aspects 12 to 15, wherein the device is separated from a previously drawn optical fiber preform prior to step a.

[0099] Although specific embodiments of the invention have been described above, it will be understood that the invention may be practiced in a manner different from that described. The above description is intended to be exemplary and not restrictive. Thus, those skilled in the art will appreciate that the described invention may be modified without departing from the scope of the claims set forth below.

Claims

1. An apparatus for connecting an optical fiber preform to a pressure supply system, the optical fiber preform including a plurality of elongated holes extending generally parallel to a longitudinal axis of the optical fiber preform, the apparatus comprising: a. A first surface to be connected to an end face of the optical fiber preform, the plurality of elongated holes terminating at the end face; b. A second surface including at least two ports configured to be in fluid connection with the pressure supply system, wherein the second surface includes a first surface portion opposite the first surface, and at least one of the at least two ports is arranged at the first surface portion; and c. A channel system within the apparatus that connects the plurality of elongated holes at the first surface to the at least two ports such that at least one of the plurality of elongated holes is connected to one of the at least two ports and such that at least one other of the plurality of elongated holes is connected to another of the at least two ports, wherein a density of the at least two ports at the second surface is less than a corresponding density of the channel system at the first surface, the corresponding density of the channel system being a number of channels within the channel system at the first surface that are connected to the plurality of elongated holes per unit area at the first surface.

2. The apparatus according to claim 1, wherein the second surface further includes a second surface portion extending generally non-parallel to the first surface, and wherein at least one other port is arranged at the second surface portion of the second surface.

3. The apparatus according to claim 1 or 2, wherein the end face of the optical fiber preform has a circular shape having a center and a radius, wherein the apparatus has a longitudinal axis coinciding with the center of the optical fiber preform, wherein the second surface further includes a second surface portion extending generally perpendicular to the first surface, and wherein at least one port is arranged at the second surface portion of the second surface at a distance from the longitudinal axis of the apparatus, the distance being greater than the radius of the optical fiber preform.

4. The apparatus according to claim 1 or 2, wherein the apparatus has a cylindrical shape having the first surface as an end surface of the cylindrical shape, wherein the second surface includes a first surface portion as an end surface of the cylindrical shape opposite the first surface and a second surface portion as a side surface of the cylindrical shape.

5. The apparatus according to claim 4, wherein the cylindrical shape corresponds to a straight cylinder or a straight elliptical cylinder.

6. The apparatus according to claim 1, wherein the first surface is provided with one or more nozzles for mating with corresponding tubular elements constituting the elongated holes in the optical fiber preform.

7. The device according to claim 1, wherein the channel system occupies a cross-sectional area that is larger at a distance from the first surface than the cross-sectional area occupied by the channel system at the first surface.

8. The device according to claim 1, wherein the device comprises an assembly of a plurality of device parts that are prepared separately and assembled together to form the device.

9. The device according to claim 8, wherein the device comprises a stack of at least three device parts extending from the first surface and including the channel system, the stack of at least three device parts including a bottom device part, a top device part, and at least one intermediate device part, wherein the intermediate device part has one or more of the following features: a. Ports located at a side surface of the intermediate device part; b. One or more unbranched channels extending through the intermediate device part; c. A plurality of channels combined into a single channel; d. One or more channels that taper such that the dimensions of the cross-section of the one or more channels increase towards the top device part side of the intermediate device part; and wherein the bottom device part includes the first surface.

10. The device according to claim 9, wherein the top device part includes ports arranged at a side surface of the top device part and / or ports arranged at a surface facing away from the at least one intermediate device part.

11. A set of device parts configured to form two different configurations of the device according to claim 1, wherein at least one device part is used in both configurations, and wherein the two configurations are capable of allowing two different optical fiber preforms to be connected to the same pressure supply system or capable of allowing two identical optical fiber preforms to be connected to the pressure supply system in different ways.

12. A method for connecting an optical fiber preform to a pressure supply system, the optical fiber preform including a plurality of elongated holes extending generally parallel to the longitudinal axis of the optical fiber preform, the method comprising the steps of: a. attaching an end face of the optical fiber preform at which the plurality of elongated holes terminate to the first surface of the device according to claim 1; and b. connecting the at least two ports to the pressure supply system.

13. The method according to claim 12, wherein the end face of the optical fiber preform is attached to the first surface of the device using a sealant to provide an airtight connection between the elongated holes in the optical fiber preform and the channel system of the device.

14. The method according to claim 12 or 13, wherein the method comprises the steps of: i. Before step a., inserting a temporary blocking member into one or more of the elongated holes in the optical fiber preform, the temporary blocking member being configured to prevent blocking of the passage between the channel system of the device and the corresponding elongated holes during step a.; and ii. Removing the temporary blocking member during or after step a.

15. The method according to claim 14, wherein the device is the device according to claim 8, wherein step a. comprises attaching the end face of the optical fiber preform to a device part including the first surface, and wherein step ii. is performed by the device part including the first surface before other device parts are connected to the device part including the first surface.

Images