Optical fibre assembly

Abstract

An optical fibre assembly for dispersing light, the assembly comprising: a first optical fibre section having a proximal end and a distal end, the distal end comprising a first down-taper in which the diameter of the optical fibre decreases; and a second optical fibre section having a proximal end and a distal end, the proximal end comprising a first up-taper in which the diameter of the optical fibre increases; wherein the assembly is arranged such that when light is directed into the proximal end of the first optical fibre section, at least a portion of the light is emitted from the first down-taper and is dispersed by the first up-taper.

Description

[0001] Optical Fibre Assembly

[0002] Field of the invention

[0003] The present disclosure relates to optical fibre technology, and more specifically to an optical fibre assembly configured to aid in the dispersal of light from the end of an optical fibre.

[0004] Background

[0005] Typically, optical fibres make use of total internal reflection in order to carry light that is directed into one end of the optical fibres such that it may be emitted out of the other end of the optical fibre. Optical fibres may be used in a wide range of applications, including in the transmission of light. One application is for transmitting light such that it may be dispersed into biological tissues in otherwise hard to reach locations. An example of such a location is the distal portion of a lung.

[0006] In some examples, the light carried by an optical fibre may be used in order to treat a medical condition. When applying light to diseased biological tissues (for example tumours) the light may be used to heat, thermally kill, and / or or ablate the tissue. During such procedures, it is generally beneficial to the patient, the clinical operator, and overall clinical throughput, to channel as much optical power into the tissue as possible. This allows the treatment to increase the temperature of the biological tissue as quickly as possible past the threshold of cell death, and in as large a volume as possible. This also allows for the procedure time to be minimised, and can also help to avoid heat sink effects caused by blood flow.

[0007] However, it has been observed that delivering excessive power to a small volume may carbonise the tissue. This can be detrimental because it may prevent the heat from dispersing into surrounding tissues, thereby limiting the volume of tissue that is subjected to the therapy. Furthermore, the carbonised tissue may absorb more light than the surrounding tissue, thereby retaining the heat in a small volume and leading to a positive feedback loop where the energy is not properly dispersed and instead "tunnels" through the tissue.

[0008] These issues may be caused, or exacerbated, by uneven dispersion and distribution of the light from the optical fibre. Such uneven dispersion can thereby limit the effectiveness of the treatment. There is a need, therefore, for an improved method of evenly and effectively dispersing light from an optical fibre.

[0009] Summary of the invention

[0010] According to a first aspect of the disclosure, there is provided an optical fibre assembly for dispersing light, the assembly comprising: a first optical fibre section having a proximal end and a distal end, the distal end comprising a first down-taper in which the diameter of the optical fibre decreases; and a second optical fibre section having a proximal end and a distal end, the proximal end comprising a first up-taper in which the diameter of the optical fibre increases; wherein the assembly is arranged such that when light is directed into the proximal end of the first optical fibre section, at least a portion of the light is emitted from the first down-taper and is dispersed by the first up-taper.

[0011] In use, light is directed into the proximal end of the first optical fibre section, which is carried along the first optical fibre section and is then dispersed by the optical fibre assembly. The rapid decrease in the diameter of the optical fibre in the first downtaper causes a portion of the light to escape from the optical fibre in the first downtaper, which is then radially dispersed by the first up-taper. In combination, the first down-taper and the first up-taper thereby ensure even and efficient dispersal of the light. As noted above, this is particularly advantageous in applications where even dispersal of light is beneficial, for example when such light is used to deliver therapy to biological tissue.

[0012] In an embodiment, there is provided an optical fibre assembly wherein the first downtaper is configured to disperse at least a portion of the light. Configuring the first down-taper to disperse light ensures that a portion of the light is dispersed without needing to interact with the up-taper, thereby improving overall light distribution.

[0013] In an embodiment, there is provided an optical fibre assembly wherein the taper angle of the first down-taper relative to the longitudinal axis of the first optical fibre section is 60 degrees or less and, optionally, 50 degrees or less. Limiting the taper angle of the first down-taper in this manner helps control the dispersion angle from the first down-taper, optimizing light spread.

[0014] In an embodiment, there is provided an optical fibre assembly wherein the taper angle of the first down-taper relative to the longitudinal axis of the first optical fibre section is 10 degrees or more and, optionally, 30 degrees or more. These limitations of the minimum taper angle ensures that at least a portion of the light escapes from the first down-taper, and that the portion that does escape is adequately dispersed.

[0015] In an embodiment, there is provided an optical fibre assembly wherein the taper angle of the first up-taper relative to the longitudinal axis of the second optical fibre section is 60 degrees or less and, optionally, 50 degrees or less. Limiting the taper angle of the first up-taper in this way ensures that the light is redirected efficiently, enhancing the radial dispersion.

[0016] In an embodiment, there is provided an optical fibre assembly wherein the taper angle of the first up-taper relative to the longitudinal axis of the second optical fibre section is 10 degrees or more and, optionally, 30 degrees or more. Limiting the taper angle of the first up-taper in this way ensures that the light is redirected efficiently, enhancing the radial dispersion.

[0017] In an embodiment, there is provided an optical fibre assembly wherein in the first down-taper the diameter of the optical fibre decreases by at least half. Reducing the diameter by at least half in the first down-taper increases the efficiency of light dispersion.

[0018] In an embodiment, there is provided an optical fibre assembly wherein after the first up-taper the diameter of the second optical fibre section is substantially the same as the diameter of the first optical fibre section. This ensures that the second optical fibre section can efficiently transmit any light that has not been dispersed by the first downtaper or the first up-taper, and also helps with ease of manufacture.

[0019] In an embodiment, there is provided an optical fibre assembly wherein the first downtaper and the first up-taper are substantially symmetrical. Symmetrical tapers help to provide even light dispersion, enhancing the efficiency and predictability of the optical fibre assembly.

[0020] In an embodiment, there is provided an optical fibre assembly wherein the first optical fibre section and the second optical fibre section are formed from a single continuous optical fibre. This may beneficially improve transmission of light between the first optical fibre section and the second optical fibre section, which has not first been dispersed by the first down-taper and the first up-taper. Further, by forming the optical fibre assembly form a single optical fibre in this manner may improve the ease of construction. In an embodiment, there is provided an optical fibre assembly wherein the first optical fibre section and the second optical fibre section are formed from separate optical fibres. This may improve the accuracy with which the first down-taper and first up- taper may be formed, by allowing for these components to be formed before they assembled into an optical fibre assembly.

[0021] In an embodiment, there is provided an optical fibre assembly wherein the first downtaper and the first up-taper are joined at their respective narrowest diameters, to form a continuous optical fibre. This may beneficially improve transmission of light between the first optical fibre section and the second optical fibre section, which has not first been dispersed by the first down-taper and the first up-taper.

[0022] In an embodiment, there is provided an optical fibre assembly wherein distal end of the second optical fibre section comprises a second down-taper in which the diameter of the optical fibre decreases. Adding a second down-taper at the distal end of the second section further enhances light dispersion capabilities.

[0023] In an embodiment, there is provided an optical fibre assembly further comprising a third optical fibre section having a proximal end and a distal end, the proximal end comprising a second up-taper in which the diameter of the optical fibre increases. Adding a third optical fibre section comprising a second up-taper further enhances light dispersion capabilities.

[0024] In an embodiment, there is provided an optical fibre assembly wherein the assembly is arranged such that when light is directed into the proximal end of the first optical fibre section, at least a portion of the light is emitted from the second down-taper and is dispersed by the second up-taper. Arranging the assembly to disperse light from the second down-taper and up-taper enhances the light dispersion capabilities.

[0025] In an embodiment, there is provided an optical fibre assembly wherein the second down-taper is configured to disperse at least a portion of the light. Arranging the assembly to disperse light from the second down-taper enhances the light dispersion capabilities.

[0026] In an embodiment, there is provided an optical fibre assembly wherein after the second up-taper the diameter of the third optical fibre section is substantially the same as the diameter of the second optical fibre section. This ensures that the third optical fibre section can efficiently transmit any light that has not been dispersed by the preceding down and up-tapers, and also helps with ease of manufacture.

[0027] In an embodiment, there is provided an optical fibre assembly wherein the second down-taper and the second up-taper are substantially symmetrical. Symmetrical tapers help to provide even light dispersion, enhancing the efficiency and predictability of the optical fibre assembly.

[0028] In an embodiment, there is provided an optical fibre assembly further comprising a dispersal tip disposed at the opposite end of the optical fibre assembly to the first optical fibre section, the dispersal tip being configured to disperse light that is directed into the proximal end of the first optical fibre section and that is not dispersed by any of the preceding down-tapers or up-tapers. Including a dispersal tip ensures that any remaining light is effectively dispersed, maximizing the efficiency of the assembly.

[0029] In an embodiment, there is provided an optical fibre assembly wherein the optical fibre comprises glass and / or polymer. Using glass and / or polymer for the optical fibre provides flexibility in material choice, allowing for optimization based on specific application requirements.

[0030] In an embodiment, there is provided an optical fibre assembly wherein the glass comprises silica glass and / or doped silica glass. Using silica glass and / or doped silica glass enhances the optical properties of the fibre, improving light transmission and dispersion.

[0031] In an embodiment, there is provided an optical fibre assembly wherein the doped silica glass comprises one or more dopants selected from: germanium, fluorine, and boron. Including such dopants allows for fine-tuning of the optical properties, enhancing performance.

[0032] In an embodiment, there is provided an optical fibre assembly wherein the first optical fibre section comprises a multi-modal optical fibre. Using a multi-modal optical fibre increases the capacity for light transmission, improving the overall efficiency of the assembly. In an embodiment, there is provided an optical fibre assembly wherein the first optical fibre section comprises a cladding. Including cladding helps contain and guide the light within the fibre, improving transmission efficiency.

[0033] In an embodiment, there is provided an optical fibre assembly wherein the cladding at least partially distributes light that is directed into the proximal end of the first optical fibre section. Using cladding to at least partially distribute light ensures even light dispersion, enhancing the performance of the optical fibre assembly.

[0034] Brief description of the drawings

[0035] There now follows a brief description of embodiments of the present disclosure, by way of non-limiting examples, with reference made to the following figures in which:

[0036] Figure 1 illustrates an example of an optical fibre assembly according to the present disclosure;

[0037] Figure 2 illustrates how light may be dispersed by an optical fibre assembly according to the present disclosure;

[0038] Figure 3 illustrates how a taper angle may be determined in an optical fibre assembly according to the present disclosure;

[0039] Figure 4 illustrates an optical fibre assembly according to the present disclosure, comprising a second down-taper and a second up-taper;

[0040] Figure 5 illustrates an optical fibre assembly according to the present disclosure, comprising a cladding with varying thickness;

[0041] Figure 6 illustrates an optical fibre assembly according to the present disclosure, comprising a dispersal tip; and

[0042] Figure 7 illustrates an optical fibre assembly according to the present disclosure, further comprising a sheath.

[0043] Detailed description

[0044] As discussed above, there is a need to provide an improved method for dispersing light from an optical fibre. The present disclosure solves this problem by providing an optical fibre assembly that is configured such that when light is directed into a proximal end of the optical fibre assembly, the light is evenly and efficiently dispersed from the distal end of the optical fibre assembly. Examples of an optical fibre assembly according to the present disclosure are described in more detail below.

[0045] Figure 1 illustrates an example of an optical fibre assembly 100 according to the present disclosure. The optical fibre assembly 100 comprises a first optical fibre section 101 and a second optical fibre section 105. The first optical fibre section 101 has a proximal end 102 into which, in use, optical light may be directed. At the distal end of the first optical fibre section 101 there is disposed a first down-taper 104. The first down-taper 104 is a section of the first optical fibre section 101 in which the diameter of the first optical fibre section 101 decreases.

[0046] The optical fibre assembly 100 further comprises a second optical fibre section 102. The second optical fibre section 102 has a proximal end, which comprises a first up- taper 108. The first up-taper 108 is a section of the second optical fibre portion 105 in which the diameter of the second optical fibre section 105 increases. In the illustrated example, the diameter of the first optical fibre section 101 before the first down-taper 104, and the diameter of the second optical fibre section 105 after the first up-taper 108 is substantially the same, although in other examples these diameters may be different.

[0047] In the illustrated example, the first down-taper 104 and the first up-taper 108 are connected to one another at their respective narrowest point, which in the illustrated example is the distal end of the first optical fibre section 101 and the proximal end of the second optical fibre section 105.

[0048] In some examples, the connection between the first optical fibre section 101 and the second optical fibre section 105 is arranged such that a portion of light directed into the proximal end of the first optical fibre section 101 may be transmitted from the first optical fibre section 101 to the second optical fibre section 105. In some examples, the connection may be formed by a substantially continuous portion of the optical fibre. In other examples, the connection may be formed by bonding the respective optical fibre sections together, and / or the respective optical fibre sections may be arranged such they simply abut one another.

[0049] In the illustrated example, the first optical fibre section 101 and the second optical fibre section 105 each comprise a core 109 and a cladding 110. In such examples, the core is configured to transmit light that is directed into the proximal end of the first optical fibre assembly 101 along the optical fibre assembly 100. The core 109 may comprise any suitable material, including glass and polymer. In some examples, the glass may comprise comprises silica glass and / or doped silica glass. In some examples, the doped silica glass may comprise one or more dopants selected from: germanium, fluorine, and boron. In some examples, the core 109 may be configured to facilitate the transmission of multi-modal light. In some examples, the material of the core of each respective optical fibre section may the same. In some examples, material of the core of one or more optical fibre sections may be different to the others. By comprising different materials, dispersion may be optimised for particular use cases.

[0050] In some examples, the cladding 110 may be configured to protect the outer surface of the core 109. The cladding may also be configured to improve the mechanical properties of the respective optical fibre sections. In some examples, the cladding 110 may be configured to aid in the transmission and / or dispersion of light directed into the proximal end of the first fibre optic section 101. The cladding 110 may comprise any suitable material, including silica glass, doped silica glass, and polymer. In some examples, the doped silica glass may comprise one or more dopants selected from: germanium, fluorine, and boron. In some examples, the material of the cladding 110 may be substantially the same as the material of the core 109. In other examples, the cladding 110 may comprise a different material to the core 109.

[0051] Figure 2 illustrates an example of an optical fibre assembly 100 according to the present disclosure. The illustration is substantially the same as in Figure 1, however three example light paths have been added to illustrate how light may be dispersed from the optical fibre assembly 100. Each of the three light paths begin at the proximal end 102 of the first optical fibre section 101.

[0052] The first light path 111 shows light being dispersed by the first down-taper 104 and the first up-taper 108. Light travelling along the first light path 111 is at least partially dispersed by the first down-taper 104, as shown by the change of direction of the first light path 111 as is passes out of the first down-taper 104. In the illustrated examples, the dispersion in the first down-taper 104 is shown as substantially occurring when the light exists the core 109 of the first optical fibre section 104. However, as noted above, in some examples the cladding 110 may additionally, or alternatively, contribute to the dispersion of light from the first down-taper 104.

[0053] After the light has been at least partially dispersed by the first down-taper 104, it may interact with the first up-taper 108 thereby to further disperse the light. As shown in the illustrated example, after light travelling along the first light path 111 has been at least partially dispersed by the first down-taper 104, it is further dispersed by the first up-taper 108. In the illustrated example, the dispersion by the first up-taper 108 occurs substantially by reflection. However, other means of dispersion are contemplated. In the illustrated example, the dispersion of light by the first up-taper 108 is performed substantially by the cladding 110. However, in some examples the dispersion may be performed at least partially (or entirely) by the core 109 of the second optical fibre section 105.

[0054] In the illustrated example, the second light path 112 illustrates a situation where light directed towards the proximal end 102 of the first optical fibre section 101 is not dispersed by either the first down-taper 104 or the first up-taper 108. Light following this second light path 112 will substantially travel into the proximal end of the second optical fibre section 105 and will be transmitted through the second optical fibre section 105.

[0055] The third light path 113 is substantially the same as the first light path 111, although on the opposite side of the optical fibre assembly 100. Light travelling along this third light path 113 will be dispersed in a direction substantially opposite to light travelling along the first light path 111. This illustrates how when light is directed into a substantially equal are of the proximal end of the first optical fibre section 101, it is dispersed substantially evenly by the optical fibre assembly.

[0056] As illustrated in figure 3, the first down-taper 104 comprises a taper angle 115, which may be measured as the angle between the slope of the first down-taper 104 and the axis of the first optical fibre section 101. Each respective down-taper and up-taper comprise a taper angle, however for simplicity only the taper angle 115 of the first down-taper 104 is shown in figure 3.

[0057] The taper angle 115 of the first down-taper 104 may be configured in order to provide optimal dispersion for any particular use case. For example, different wavelengths of light may require different taper angles in order to achieve optimal dispersion of the light from the optical fibre assembly. Some use cases (for example, particular therapies) may require particular wavelengths of light and so the taper angle 115 of the first down-taper 104 may be adjusted accordingly.

[0058] In some examples, the taper angle 115 of the first down-taper may be 60 degrees or less and, optionally, 50 degrees or less. In some examples, the taper angle 115 of the first optical fibre section may be 10 degrees or more and, optionally, 30 degrees or more. In some example, the taper able of each respective down-taper and up-taper (for example, the first up-taper 108) may each be configured in order to provide optimal dispersion for any given use case.

[0059] Although not shown, the taper angle of the first up-taper (and any other down- or up- tapers) may be determined similarly to the illustration in figure 3. For example, the taper angle of the first up-taper 108 may be measured as the angle between the slope of the first up-taper 108 and the axis of the second optical fibre section 105. In some examples, the taper angle of the first up-taper 108 may be 60 degrees or less and, optionally, 50 degrees or less. In some examples, the taper angle of the first up-taper 108 may be 10 degrees or more and, optionally, 30 degrees or more.

[0060] In the examples illustrated in figures 1 to 3, the taper angle of the first down-taper 104 and the first up-taper 108 are substantially equal. However, in some examples the respective taper angles may be different. In some examples, different respective down- and up-tapers comprising different taper angles may facilitate optimal dispersion in particular use cases.

[0061] Figure 4 illustrates a further example of an optical fibre assembly 100 according to the present disclosure. In the illustrated example, the second optical fibre section 105 comprises a second down-taper 116. The optical fibre assembly 100 also comprises a third optical fibre section 117, which comprises a second up-taper disposed at the proximal end of the third optical fibre section 117.

[0062] The second down-taper 116 and second up-taper 120 are each configured to disperse at least a portion of light directed into the proximal end of the first optical fibre section 101. By comprising a second down-taper 116 and a second up-taper 120, dispersion of light from the optical fibre assembly 100 may be optimised for a particular use case.

[0063] In the illustrated examples, the optical fibre assembly 100 comprises either one downtaper and up-taper portion, or two down-taper and up-taper portions. However, in some examples the optical fibre assembly may further comprise a third down-taper and a third up-taper. In some examples, still further down-tapers and up-tapers may be included. In some examples, the number of down-tapers and up-tapers may be selected in order to optimise the dispersal of light for a particular use case. For example, a particular therapy and / or a particular wavelength (or combination of wavelengths) of light may require three or more down-tapers and up-tapers in order to optimally distribute light. In the examples illustrated in figures 1 to 4, the cladding 110 is shown to maintain substantially the same thickness through the various tapered portions of the optical fibre assembly 100. However, as illustrated in figure 5, in some examples the cladding 110 may vary in thickness thereby to maintain the diameter of the optical fibre assembly 100 substantially constant. This may be advantageous in improving the structural strength and / or stability of the optical fibre assembly 100, which may otherwise be impaired particularly in the various tapered portions.

[0064] Figure 6 illustrates a further example of an optical fibre assembly 100 according to the present disclosure. In the illustrated example, a dispersal tip 121 is disposed at the opposite end of the optical fibre assembly 100 to the first optical fibre section 101. In some examples, the dispersal tip may be configured to disperse light that is directed into the proximal end of the first optical fibre section and that is not dispersed by any of the preceding down-tapers or up-tapers. The dispersal tip 121 may comprise any suitable shape configured to provide optimal dispersal of light. In some examples the dispersal tip 121 is substantially spherical in shape. The example illustrated in figure 6 comprises a varying thickness cladding 110, although this is merely an example and any suitable cladding thickness may be used.

[0065] In the illustrated example, the radius of the dispersal tip is substantially the same as the radius of the cross section of the optical fibre section immediately preceding the dispersal tip 121 (in the illustrated example, this is the second optical fibre section 105). However, in some examples the radius of the dispersal tip 121 may be larger than the radius of the cross section of the optical fibre section immediately preceding the dispersal tip 121. In such examples, the increased radius of the dispersal tip 121 may have a lensing effect, thereby enhancing the dispersion of light from the dispersal tip 121.

[0066] As noted above, an optical fibre assembly 100 according to the present disclosure may comprise any number of down-tapers and up-tapers. In any such example, the optical fibre assembly 100 may comprise a dispersal tip 121 disposed at the distal end of the optical fibre assembly 100, such that light that is not dispersed by any of the preceding down-tapers or up-tapers may be dispersed by the dispersal tip 121.

[0067] Figure 7 illustrates an example of an optical fibre assembly 100, further comprising a sheath 122. In the illustrated example, the sheath 122 substantially surrounds the optical fibre assembly. In the illustrated example, the sheath 122 comprises a body portion 123 and a tip portion 124. The body portion 123 is substantially straight, and is configured to surround the optical fibre sections and the tapered sections (i.e., the respective down-tapers and up-tapers).

[0068] The tip portion 124 may be curved, and is configured to cover the distal end of the optical fibre assembly 100. In the illustrated example, the optical fibre assembly does not comprise a dispersal tip, however in examples where the optical fibre assembly does comprise a dispersal tip 121, the tip portion 124 of the sheath 122 may be configured to substantially cover and protect the dispersal tip 121. In some examples, the tip portion 124 may be configured to facilitate the dispersal of light.

[0069] The sheath 122 is primarily configured to protect the optical fibre assembly, at least in part by providing additional structural support to the optical fibre assembly. In some examples, the sheath 122 may be further configured to aid with the dispersal of light.

[0070] The sheath 122 may comprise any suitable materials, including glass and polymer. In some examples, the glass may comprise comprises silica glass and / or doped silica glass. In some examples, the doped silica glass may comprise one or more dopants selected from: germanium, fluorine, and boron. In some examples, the sheath 122 may comprise substantially the same materials as one or more of the core 109 and, if present, the cladding 110. In other examples, different materials may be used for each component.

[0071] A sheath 122 may be particularly beneficial in examples where the optical fibre assembly does not comprise a cladding 110, and / or where it comprises a cladding 110 with a thickness that remains substantially the same in the down-taper and up-taper sections (as illustrated in figures 1 to 4). In such examples, the sheath 122 may beneficially provide additional structural support to the tapered sections (i.e., the down-tapers and up-tapers) of the optical fibre assembly.

[0072] An optical fibre assembly 100 according to the present disclosure, and as illustrated in figures 1 to 7, may be formed using any suitable manufacturing methods.

[0073] In some examples, the respective optical fibre sections may be formed separately. In such examples, the respective down-taper and up-taper portions may be formed on the respective ends of the respective optical fibres sections prior to assembly of the optical fibre assembly. In such examples, the respective down-tapers and up-tapers may be joined through any suitable means, or may simply abut one another. In examples where the respective optical fibre sections are formed separately and then are joined together, the joining may be performed using any suitable method. In some examples, the joining may be performed by heating the respective down-taper and up- taper portions such that they are at least partially molten, and then bringing them together such that a substantially continuous optical fibre is formed.

[0074] In examples where the respective optical fibre sections are not formed separately, the respective down-tapers and up-tapers may be formed from a single optical fibre using any suitable method. For example, a portion of the optical fibre may be heated such that it is at least partially molten, with tension then being applied in order to form the tapers.

[0075] Although the invention has been described in considerable detail in language specific to structural features, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific features described. Rather, the specific features are disclosed as exemplary forms of implementing the claimed invention. Stated otherwise, it is to be understood that the phrases and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. Therefore, while exemplary illustrative embodiments of the invention have been described, numerous variations and alternative embodiments will occur to those skilled in the art. Such variations and alternate embodiments are contemplated, and can be made without departing from the spirit and scope of the invention.

Claims

CLAIMS1. An optical fibre assembly for dispersing light, the assembly comprising: a first optical fibre section having a proximal end and a distal end, the distal end comprising a first down-taper in which the diameter of the optical fibre decreases; and a second optical fibre section having a proximal end and a distal end, the proximal end comprising a first up-taper in which the diameter of the optical fibre increases; wherein the assembly is arranged such that when light is directed into the proximal end of the first optical fibre section, at least a portion of the light is emitted from the first down-taper and is dispersed by the first up-taper.

2. The optical fibre assembly according to claim 1, wherein the first down-taper is configured to disperse at least a portion of the light.

3. The optical fibre assembly according to claims 1 or 2, wherein the taper angle of the first down-taper relative to the longitudinal axis of the first optical fibre section is 60 degrees or less and, optionally, 50 degrees or less.

4. The optical fibre assembly according to any preceding claim, wherein the taper angle of the first down-taper relative to the longitudinal axis of the first optical fibre section is 10 degrees or more and, optionally, 30 degrees or more.

5. The optical fibre assembly according to any preceding claim, wherein the taper angle of the first up-taper relative to the longitudinal axis of the second optical fibre section is 60 degrees or less and, optionally, 50 degrees or less.

6. The optical fibre assembly according to any preceding claim, wherein the taper angle of the first up-taper relative to the longitudinal axis of the second optical fibre section is 10 degrees or more and, optionally, 30 degrees or more.

7. The optical fibre assembly according to any preceding claim, wherein in the first down-taper the diameter of the optical fibre decreases by at least half.

8. The optical fibre assembly according to any preceding claim, wherein after the first up-taper the diameter of the second optical fibre section is substantially the same as the diameter of the first optical fibre section.

9. The optical fibre assembly according to any preceding claim, wherein the first down-taper and the first up-taper are substantially symmetrical.

10. The optical fibre assembly according to any preceding claim, wherein the first optical fibre section and the second optical fibre section are formed from a single continuous optical fibre.

11. The optical fibre assembly according to any of claims 1 to 9, wherein the first optical fibre section and the second optical fibre section are formed from separate optical fibres.

12. The optical fibre assembly according to claim 11, wherein the first down-taper and the first up-taper are joined at their respective narrowest diameters, to form a continuous optical fibre.

13. The optical fibre assembly according to any preceding claim, wherein distal end of the second optical fibre section comprises a second down-taper in which the diameter of the optical fibre decreases.

14. The optical fibre assembly according to claim 13, further comprising a third optical fibre section having a proximal end and a distal end, the proximal end comprising a second up-taper in which the diameter of the optical fibre increases.

15. The optical fibre assembly according to claim 14, wherein the assembly is arranged such that when light is directed into the proximal end of the first optical fibre section, at least a portion of the light is emitted from the second down-taper and is dispersed by the second up-taper.

16. The optical fibre assembly according to any of claims 13 to 15, wherein the second down-taper is configured to disperse at least a portion of the light.

17. The optical fibre assembly according to any of claims 14 to 16, wherein after the second up-taper the diameter of the third optical fibre section is substantially the same as the diameter of the second optical fibre section.

18. The optical fibre assembly according to any according to any of claims 14 to 17, wherein the second down-taper and the second up-taper are substantially symmetrical.

19. The optical fibre assembly according to any preceding claim, further comprising a dispersal tip disposed at the opposite end of the optical fibre assembly to the first optical fibre section, the dispersal tip being configured to disperse light that is directed into the proximal end of the first optical fibre section and that is not dispersed by any of the preceding down-tapers or up-tapers.

20. The optical fibre assembly according to any preceding claim, wherein the optical fibre comprises glass and / or polymer.

21. The optical fibre assembly according to claim 20, wherein the glass comprises silica glass and / or doped silica glass.

22. The optical fibre assembly according to claim 21, wherein the doped silica glass comprises one or more dopants selected from: germanium, fluorine, and boron.

23. The optical fibre assembly according to any preceding claim, wherein the first optical fibre section comprises a multi-modal optical fibre.

24. The optical fibre assembly according to any preceding claim, wherein at least the first optical fibre section comprises a cladding and wherein, optionally, the cladding is configured to at least partially distribute light that is directed into the proximal end of the first optical fibre section.

25. The optical fibre assembly according to any preceding claim, further comprising a sheath configured to substantially surround the optical fibre assembly and wherein, optionally, the sheath is configured to at least partially distribute light that is directed into the proximal end of the first optical fibre section.

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