Fibre optic connector, kits of parts and methods of using the same

Abstract

The invention relates to a fibre optic connector (e.g. an SC-type connector) for attachment to the end of an optical fibre. The connector has a rear body (200) provided with a longitudinal slot which receives the optical fibre (400) (see Fig. 3). The rear body (200) supports the resilient insert (300) within a transverse slot (202) so as to partially surround the optical fibre (400) and apply a forward biasing force to a rear end of a ferrule sub-assembly in which the optical fibre (400) is terminated. The resilient insert 300 has an opening (e.g. it may be U-shaped), or it is openable, to thus allow it to engage the ferrule sub-assembly at locations spaced around an optical axis without having been threaded over the optical fibre (400) or the ferrule sub-assembly. Advantageously, this type of resilient insert (300) avoids the need to thread a conventional spring over the connector rear body (200), thus facilitating a reduction in the length and / or diameter of the connector and simplifying its final assembly in the field.

Description

[0001] FIBRE OPTIC CONNECTOR, KITS OF PARTS AND METHODS OF USING THE SAME

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a fibre optic connector, and more particularly to a fibre optic connector for attachment to the end of an optical fibre. The present invention further relates to a kit of parts for making a fibre optic connector, and to methods of using the same.

[0004] BACKGROUND

[0005] Fibre to the home (FTTH) is the generic term for broadband network architecture that uses optical fibre technology to carry data to a residential dwelling from a broadband service provider via a telecommunications cabinet located near the residential dwelling. Purely by way of example, the products and techniques disclosed herein may be applied in FTTH applications, as well as in installation of optical fibres to a variety of premises (FTTx) and / or within premises. In many installations, optical fibres are installed through an installation tube or duct, for example a so-called microduct. In one type of installation, the optical fibre is carried through the duct using compressed gas or fluid, for example air. This is known as installation by blowing, and special lightweight cable assemblies known as “fibre units” have been developed for this installation method. Optical fibres can also be installed by pushing, or pulling, or preinstalled in a duct. Different cable designs can be used for these different methods. For example, a cable adapted for installation by pulling may include strengthening fibres, surrounding the optical fibres and all contained within an outer sheath. A cable adapted for installation by pushing may include a strength member such as a fibre reinforced plastic rod to resist compression as well as providing tensile strength and stiffness. Versatile cables are also becoming available, which can be installed over useful distances by any of pulling, pushing and blowing.

[0006] In order to transmit optical signals to homes and commercial premises through a network, an optical fibre needs to be either spliced to another optical fibre or terminated with a suitable connector. Common connector types for telecommunication applications include SC and LC, as well as so-called ‘hardened’ connectors with increased strength and protection against the environment. In a typical connector, one or two ferrule sub-assemblies are generally attached to one or two optical fibres respectively. An optical ferrule is typically a cylinder of material (for example zirconia, ceramic or plastic), having a small bore into which the glass element of the optical fibre is inserted and cemented, and whose end is then polished to mate with a corresponding ferrule in a mating connector. In order to avoid performing complex and delicate termination of the optical fibre in the field, there is a trend towards using preterminated optical fibres, in which at least a partial connector has been added to the end of the optical fibre in a factory environment. The standard connector bodies are typically too large to be installed through the installation tube, but a suitably designed connector body can be fitted around the partial connector at the end of the cable, after it emerges from the duct. The partial connector typically includes the optical ferrule mounted in a ferrule holder, and a coil spring surrounding the cable immediately behind the ferrule holder. The ferrule and ferrule holder (where provided) may be referred to as a ferrule sub-assembly. The coil spring, in the finished connector, engages the rear end of the ferrule sub-assembly to apply a forward biasing force to the ferrule, when it mates in with an opposing ferrule to make an optical connection. Examples of such preterminated optical fibres and connectors can be seen in GB2558567A and WO2023016835A1.

[0007] In order to facilitate installation in smaller sizes of microduct, and to allow routing around bends, it is desirable to minimise both the diameter and the length of the partial connector. As the coil spring in the known connectors fits around the end of the cable, it is necessarily of a larger diameter than the cable itself. Additionally, the coil spring has a length which contributes to the overall length of the partial connector. This may indirectly limit the diameter of cable that can be installed through a certain diameter of duct. Alternatively or in addition, it may affect the ability of the partial connector to travel around bends.

[0008] In EP3299858A1 it is proposed to provide a coil spring as a resilient biasing member that is separate from the ferrule sub-assembly, and which has an opening large enough to pass over the ferrule and ferrule holder, after installation through the duct. This avoids the need for the spring to pass through the duct, but a larger spring takes up more space and the connector body has to be made in more parts to capture the spring and connect it operably with the rear end of the ferrule holder.

[0009] SUMMARY OF THE INVENTION

[0010] According to a first aspect of the present invention, there is provided a connector for attachment to the end of an optical fibre, the connector comprising (at least) a rear body and a ferrule biasing arrangement, wherein the rear body is provided with a longitudinal slot configured to allow the optical fibre to be inserted into the rear body, wherein the rear body is configured to support the ferrule biasing arrangement in a position at least partially surrounding the optical fibre so as to apply a forward biasing force to a rear end of a ferrule sub-assembly in which the optical fibre is terminated, and wherein the ferrule biasing arrangement is formed with an opening, whereby it can engage the rear end of the ferrule sub-assembly at locations spaced around an optical axis of the ferrule sub-assembly without having been threaded over the optical fibre or the ferrule subassembly.

[0011] The inventors have recognised that a ferrule biasing arrangement need not have a closed shape such as a coil spring, but can be made in a form that has a side opening, or at least is openable. As will be seen, this provides much greater flexibility to design a connector that avoids one or more of the drawbacks identified above.

[0012] Optionally, the ferrule biasing arrangement comprises at least one resilient insert formed of a material different to a material of the rear body. For example, in some examples the resilient insert is formed at least partly of metal, while the rear body is formed of a plastic. In other examples, the resilient insert may be formed at least partly of an elastomeric material, while the rear body is formed of a relatively rigid plastic.

[0013] In some examples, the resilient insert is received in a transverse slot within the rear body.

[0014] In some examples, the resilient insert is substantially U-shaped.

[0015] In some examples, the ferrule biasing arrangement comprises at least one deflectable tine. Optionally, the ferrule biasing arrangement comprises at least two deflectable tines.

[0016] In some examples, the connector further comprises at least one front body part, the front body part being formed so as to mate with the rear body after an optical fibre has been fitted into the longitudinal slot and to hold a ferrule sub-assembly in engagement with the ferrule biasing arrangement.

[0017] In some examples, the ferrule biasing arrangement is formed in one piece.

[0018] In some examples, the ferrule biasing arrangement is integrated with the rear body, for example by over moulding or co-moulding a resilient insert. In other examples, the ferrule biasing arrangement is formed integrally with the rear body by forming one or more resilient elements from the material of the rear body.

[0019] In some examples, the ferrule biasing arrangement is adapted to apply a forward biasing force in the range of 5 to 12 N over a predetermined range of rearward travel of the ferrule subassembly, for example a force in the range 5 to 6 N or a force in the range 7 to 12 N.

[0020] In some examples, the ferrule biasing arrangement is adapted to apply a forward biasing force to the rear end of the ferrule sub-assembly over a range of at least 0.4 mm travel.

[0021] According to a second aspect of the invention, there is provided a kit of parts comprising a connector according to the first aspect of the invention as set forth above, together with a ferrule sub-assembly adapted to be received in the longitudinal slot of the rear body and having a rear end adapted to engage the ferrule biasing arrangement, when assembled.

[0022] Optionally, the kit of parts may further include an optical fibre cable, wherein the ferrule subassembly has been fitted already to terminate an optical fibre at one end of the optical fibre cable.

[0023] Optionally, the kit of parts may further include an installation duct, wherein the optical fibre cable including the ferrule sub-assembly has been installed in the installation duct.

[0024] According to a third aspect of the present invention, there is provided a method of installing an optical fibre in an installation tube, the method comprising: providing an optical fibre terminated at a leading end with a ferrule sub-assembly; inserting the leading end of the optical fibre including the ferrule sub-assembly into an installation tube; propelling the connector and the attached optical fibre along the length of the installation tube to a distal end thereof; and at the distal end of the installation tube, assembling a connector around the ferrule sub-assembly, the connector including a rear body and a ferrule biasing arrangement in accordance with the first aspect of the invention as set forth above. The step of propelling the optical fibre along the installation tube may be performed before or after the installation tube is installed along a desired route.

[0025] These and further aspects and examples of the present disclosure will be description and drawings.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Embodiments of the present invention in different aspects will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0028] Figure 1 is a schematic view of a connector rear body in accordance with a first example;

[0029] Figure 2a is a schematic view of a resilient insert and the rear body in accordance with the first example, and Figure 2b is a schematic view of the rear body with the resilient insert inserted;

[0030] Figure 3 is a schematic view of the rear body, with the resilient insert and a ferrule inserted in accordance with the first example;

[0031] Figure 4 is a schematic view of the resilient insert in accordance with the first example;

[0032] Figure 5 is a schematic cross-sectional view of the example of Figure 3 with a front body part fitted;

[0033] Figures 6a and 6b are schematic views of a connector assembly before and after it is complete;

[0034] Figure 7 is a schematic plan view of a connector rear body in accordance with a second example;

[0035] Figure 8a is a schematic perspective view of a resilient insert and the rear body in accordance with the second example, and Figure 8b is a schematic view of the rear body with the resilient insert inserted; Figure 9 is a schematic plan view of the rear body, with the resilient insert and the ferrule inserted in accordance with the second example;

[0036] Figure 10 is a schematic perspective view of the resilient insert in accordance with the second example;

[0037] Figure 11 is a schematic cross-sectional view of the embodiment of Figure 9 with a housing fitted in accordance with the second example; and

[0038] Figure 12 is a schematic view of a resilient insert in accordance with a third example.

[0039] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0040] INTRODUCTION

[0041] In the following description and drawings, there will be described various examples of a connector for fitting to the end of an optical fibre, after that optical fibre has been installed through a tube. The optical fibre may be contained within a lightweight and compact cable, for example of the type used for installation by blowing through compact installation tubes referred to as microducts. Such a cable may be referred to in the market as a 'fibre unit’, ‘microcable’ or ‘nanocable’. The diameter of the cable depends on a number of its construction, as well as the number of fibres contained. A lightweight fibre unit for installation by blowing may contain only one to 4 fibres and may have an outer diameter that said cable is less than 1.2 mm, optionally less than 1 .1 mm or even less than 1 .0 mm. In other examples, the fibre optic cable may contain a greater number of optical fibres and / or may include additional elements such as strength members that dictate a larger outer diameter, for example in the range of 1 .5 to 2.5 mm, for example in the range 1 .9 to 2.2 millimetres, for example 2.0 to 2.1 mm. The skilled person will readily adapt the examples presented herein to these different sizes and use cases.

[0042] By convention, a microduct is defined as any installation tube having an outer diameter (OD) of 16 mm or less, and a smaller inner diameter (ID). For the purposes of the present disclosure, the installation tubes may have OD / ID sizes such as (purely as examples) 8 / 5 mm, 7 / 4 mm, or 5 / 3.5 mm, 4 / 2.5 or even 3 / 2.1 mm. It will be understood that the inner diameter of the tube needs to be greater than the outer diameter of the selected cable, and also greater than the outer diameter of any partial connector which is pre-fitted to the leading end of the cable. A sufficient margin of additional diameter is required, depending on the installation method selected, frictional properties of the materials, the presence of bends and so forth. The skilled person will readily adapt the examples presented herein to these different sizes and use cases.

[0043] In the following examples, a connector for attachment to the end of an optical fibre cable includes a rear body and a ferrule biasing arrangement, which together can be assembled around the end of the optical fibre cable, where a partial connector has already been factory- fitted. The rear body in these examples is provided with a longitudinal slot which is wide enough, in a rear portion, to accept the optical fibre cable without constraining its movement in the longitudinal direction. The diameter of the longitudinal slot in this rear portion may be, for example, in the range of 0.9 mm to 3.0 mm, for example 0.9 mm to 2.0 mm. A front portion of the longitudinal slot, which may have a form and dimension different to the rear portion, is for accommodating a partial connector, for example a ferrule sub-assembly incorporating a ferrule and ferrule holder.

[0044] The rear body of the connector in these examples is further configured to support a ferrule biasing arrangement in a position at least partially surrounding the optical fibre, where it can apply a forward biasing force to a rear end of ferrule sub-assembly in which the optical fibre is terminated. The ferrule biasing arrangement is formed with an opening, whereby it can engage the rear end of the ferrule sub-assembly at locations spaced around an optical axis of the ferrule sub-assembly without having been threaded over the optical fibre or the ferrule subassembly. In the examples described below, the ferrule biasing arrangement is formed so as to be substantially symmetrical about one or more planes aligned with the optical axis. In this way, the required force and deflection is provided substantially equally either side of the ferrule on insertion.

[0045] The skilled reader will appreciate that the examples illustrated are only a few of the possible designs implementing the broader principles disclosed herein. Many modifications and variations within the scope of the present disclosure, some of which are described further below.

[0046] THE ILLUSTRATED EXAMPLES

[0047] Referring to Figure 1 of the drawings, there is shown a connector rear body 200 with a longitudinal slot 201 and a transverse slot 202. In this example, the transverse slot 202 of the rear body 200 has a first portion 202a and a second portion 202b, the first portion being wider in the transverse direction than the second portion, and the first and second portions both are wider than the diameter of the longitudinal slot 201 . In this example, the outer surface of the connector rear body 200 comprises ribs or ridges 211 .

[0048] Figure 2a shows the connector rear body 200 of Figure 1 with a resilient insert 300 positioned above prior to insertion and Figure 2a shows the connector rear body 200 of Figure 1 with the resilient insert 300 inserted into the transverse slot 202. The resilient insert 300 may conveniently be an interference fit into the transverse slot 202 located in the connector rear body 200. The resilient insert 300 in this example sits against a closed bottom face of the transverse slot 202 of the connector rear body 200. The resilient insert 300 in this example is substantially U-shaped, being open at one side as well as in the centre so as not to block the longitudinal slot 201 of the connector rear body 200.

[0049] Figure 3 shows the connector rear body 200 with the resilient insert 300 and a ferrule 410 inserted, which has been fitted to the end of an optical fibre cable 400. A ferrule holder 420 is also shown. The ferrule holder in this example 420 is provided with a plurality of grooves, indentations, or ridges, in the manner described in GB2558567A, mentioned above. In this example, the ferrule holder 420 has an asymmetric D-shaped profile which is located and aligned within a correspondingly-shaped section of the connector rear body 200. This ensures the correct orientation of the fibre optic ferrule connection is achieved and minimises angular rotation of the connector around the longitudinal axis of the optical ferrule 410. The flat in section of the D-shaped profile can be seen in the cross-section of another example, shown in Figure 11 . Apart from differences are specifically mentioned, all the features in the examples of Figures numerals 1 to 11 are substantially the same.

[0050] The resilient insert 300 is shown in more detail in Figure 4. The resilient insert 300 has two deflectable tines 301 and 302 and an outer frame 303. The deflectable tines 301 and 302 are located either side of the central opening of the resilient insert 300. In this example the tines each extend from a base portion of the frame of the resilient insert 300. It will be recognised that the resilient insert can be conveniently formed out of a single piece of metal by a stamping process. Any suitable metal may be used, including for example stainless steel or beryllium copper. The thickness of the metal in the illustrations is not necessarily to scale. The metal thickness may be for example in the range 0.1 to 0.7 mm, for example less than 0.5 mm or less than 0.3 mm. The skilled person will appreciate that reasonable experimentation may be required to arrive at the appropriate combination of material selection and material processing, as well as its thickness and shape, so that a desired combination of biasing force and travel will be achieved and maintained over a lifetime of operation.

[0051] Considering Figures 1 to 4 together, it will be seen that the outer frame of the resilient insert

[0052] 300, in use, is received in the wider, first portion 202a of the transverse slot 202 of the connector rear body 200. At the same time, the deflectable tines 301 , 302 extend into the second portion 202b of the slot, while being free to deflect in a rearward direction. The tines

[0053] 301 , 302 extend partly into the longitudinal slot 201 so that they will engage a rear surface of the ferrule holder 420, without impeding free movement of the cable 400. In this way, the tines can impart a forward force on the ferrule holder 420, countering any force that pushes the ferrule rearward into the connector rear body 200.

[0054] Figure 5 is a schematic cross-sectional view of the example of Figure 3 with a connector housing or front body part 210 fitted. In the example of an SC connector, illustrated this front body part 210 is what may be called the inner shroud of the standard connector, and an outer shroud will be added as mentioned later to complete the front body part from the end user’s perspective. This front body part 210 is connected or fixed to the connector rear body 200 such that it surrounds the connector rear body 200, in this case substantially enclosing the part of the connector rear body 200 that receives the ferrule holder 420.

[0055] As can be seen, the front body part 210 has a narrowed opening through which the ferrule 410 projects, while the front body part engages a forward end of the ferrule holder 420. In this way, the ferrule sub-assembly is now held captive against forward movement. Optionally, the fitting of the front body part 210 already causes the rear end of the ferrule holder to engage slightly the ferrule biasing arrangement, in this example the tines 301 and 302 of the resilient insert 300. The ferrule biasing arrangement will be engaged so as to apply a forward biasing force against rearward movement of the ferrule sub-assembly.

[0056] The arrow in Figure 5 represents the forward force provided by the deflection of the tines 301 and 302. It will be recognised that each tine has the form of a cantilever spring, and in general the resilient insert is formed to be symmetrical about a central plane aligned with the optical axis of the ferrule 410. By engaging the rear end of the ferrule holder 420 at two locations spaced 180° apart around the optical axis of the ferrule 410, this ferrule biasing arrangement can provide a forward biasing force, without a tendency to skew the ferrule so as to compromise any optical connection formed at its front end. In the illustrated example, the cable 400 includes two or more optical fibres and a central strength members, all embedded in a solid resin to form a coated fibre bundle, and then covered with an extruded outer sheath. An internal bore 425 of the ferrule holder 420, has a concave curved tapered end to guide an optical fibre (not fully visible in this cross-section) from the cable into the ferrule 410. The optical fibre is cemented into a central bore of the ferrule 410. The ferrule in an SC or LC connector conventionally has a diameter of 1.25 mm. The ferrule holder 420, at least in a forward portion the rear end of the ferrule, has a slightly greater diameter. The forward portion of the longitudinal slot in the rear body 200 is dimensioned so as to allow longitudinal sliding of the ferrule holder within the rear body, while keeping it closely aligned with a desired optical axis.

[0057] This type of cable, and the manner in which it is fixed into the ferrule 410 and ferrule holder 420, can be the same as for example described in WO2023016835A, mentioned above. In this construction, the ferrule holder 420 is bonded to a portion of the extruded outer sheath so as to provide significant tensile strength against pulling forces on the cable. This type of construction is only an example, however, and more conventional constructions are possible, for example using tensile yarns within the cable 400 to provide tensile connection to the ferrule holder.

[0058] Referring to Figures 6a and 6b, the outer shroud 220 is fitted over the front body part 210 and a boot 230 is fitted over a rear part of the connector rear body 200, engaging the ribs or ridges 211 . These parts all together form a complete connector assembly, which in this example is a complete SC connector plug. The boot provides protection against excessive bending of the cable, without restricting its movement in a longitudinal direction. When mated with the ferrule of another connector to carry optical signals between two fibres, the ferrule 410 can deflect back approximately 0.4mm with the resilient insert giving a reactive force of approximately 10N. This degree of movement is sufficient to meet the mandatory specifications for an SC connector, even if a conventional coiled spring allows further movement.

[0059] Referring to Figure 7 of the drawings, there is shown another example of a connector rear body 2000 with the longitudinal slot 2010 and the transverse slot 2020. The transverse slot in this example has a different shape to the first example, in that its second portion 2020b has a more trapezoidal cross section, wider where it meets the first section 2020a. This is to accommodate a different shaped resilient insert, as will be illustrated below. In this example also, the outer surface of the connector rear body 2000 is provided with ribs or ridges 2110. Figure 8a shows the SC connector rear body 2000 of Figure 7 with the resilient insert 3000 prior to insertion and Figure 8a shows the connector rear body 2000 with the resilient insert 3000 inserted. The resilient insert 3000 may conveniently be an interference fit into the transverse slot 2020 of the connector rear body 2000. The resilient insert 3000 may sit flush with the bottom face of the transverse slot 2020 of the connector rear body 2000. The resilient insert 3000 is substantially U-shaped, having an open centre so as not to block the longitudinal slot 2010 of the connector rear body 2000.

[0060] Figure 9 shows the SC connector rear body 2000 with the resilient insert 3000 and the cable 4000 inserted. The ferrule holder 4200 and the termination piece 4100 are also shown. These parts, with reference numbers suffixed ‘O’, perform the same functions as the like numbered parts in the example of Figures 1 to 6.

[0061] The resilient insert 3000 of this second example is shown in more detail Figure 10. The resilient insert 3000 has two deflectable tines 3010 and 3020. The deflectable tines 3010 and 3020 project toward the open centre of the U-shape of the resilient insert 3000, extending from side portions of the frame 3030 rather than from the base portion. As in the first example, these are adapted to deflect when the finished connector mates with another connector and pressure is applied to the end of the ferrule 4100.

[0062] Figure 11 is a schematic cross-sectional view of the example of Figure 9 with a front body part 2100 fitted. This front body part 2100 is connected or fixed to the connector rear body 2000 such that it substantially encloses a forward part of the connector rear body 2000. The internal bore 1250 of the ferrule holder 4200, has a concave curved tapered end to guide the fibre into the termination piece 1100 with reduced stress. The cross-section seen in Figure 11 is taken in a vertical plane of the connector, whereas the cross-section in Figure 5 is taken in a horizontal plane (all with reference to the orientation shown in the perspective views). In this view, the optical fibre 4300 can be seen extending from the cut end of the cable into the central bore of the ferrule 4100. The cable 4000 again includes two or more optical fibres and a central strength element, all contained within an extruded outer sheath, and bonded into the ferrule holder 4200 as described in WO2023016835A.

[0063] Also seen in Figure 11 is that the forward part of the longitudinal slot, in which the ferrule holder is received, has an asymmetric cross-section. At the bottom side, in the orientation shown, is the flattened part of the D-shaped cross-section, mentioned above. The engagement of these flat surfaces ensures a correct orientation of the ferrule 410 in the connector body. This can be important, for example when the front end of the ferrule and optical fibre have been polished at an angle.

[0064] Figure 12 shows a third example of a resilient insert 3001. The resilient insert 3001 has one deflectable tine 3011 , which is forked or bifurcated so as to engage the rear face of the ferrule holder at diametrically opposite locations. The deflectable tine 3011 is substantially Y shaped, extends from the base of the U-shape of the resilient insert 3000, and is free to deflect when inserted into the SC connector rear body 2000.

[0065] SUPPLYING AND USING THE CONNECTOR

[0066] In the illustrated examples, no special tooling is required during the final assembly of the SC connector in the field. Therefore, it may be undertaken by either the installer or the final user of the optical fibre system at the site of the installation, further increasing the ease with which the optical fibre may be installed.

[0067] For the manufacture of preterminated optical fibre cables, the connector may conveniently be supplied as a kit of parts, including a ferrule sub-assembly, a rear body, at least one front body part, and optionally further parts to be assembled to the rear body and / or the front body to complete the connector. In the illustrated examples of an SC connector, for example, additional parts include the outer shroud 220 and the boot 230. The kit of parts will include the ferrule biasing arrangement, either as one or more separate components or already formed or fitted within the rear body.

[0068] The ferrule sub-assembly will be fitted to an optical fibre at the end of the cable 400 within a factory environment. Needless to say, when supplying such kits of parts in volume, the ferrule sub-assemblies may be packaged separately from the other parts, to simplify the handling and logistics. A packet containing the other parts can be supplied to the installer with each of the preterminated cables.

[0069] Various methods can be envisaged for installing an optical fibre in an installation tube, when an optical fibre has been pre-fitted at a leading end with a ferrule sub-assembly. A method may begin with inserting the leading end of the optical fibre including the ferrule sub-assembly into an installation tube. A next step is propelling the connector and the attached optical fibre along the length of the installation tube to a distal end thereof. Finally, at the distal end of the installation tube, the remaining parts of the connector are assembled around the ferrule subassembly. Using a connector of the above examples, the rear body and a ferrule biasing arrangement will be fitted, either as a unit or in separate steps. Next, by other parts such as the illustrated front body parts and boot will be fitted to complete the finished connector.

[0070] In one type of method, the optical fibre will be propelled through the installation tube after the tube has been laid along a desired route in the field. In another type of method, the optical fibre will be installed in a length of tube while still in a factory environment. The installation tube pre-populated with the optical fibre can be laid along a desired route. The leading end of the optical fibre is then accessed by cutting off an excess length of the installation tube. In this way, the number of steps to be performed in the field, as well as the skills and equipment involved, can be further reduced. The installer can choose the best method according to the circumstances of each project.

[0071] OTHER EXAMPLES

[0072] In the illustrated examples, the ferrule biasing arrangement is formed so as to engage the rear end of the ferrule sub-assembly at two locations, diametrically axis of the ferrule subassembly. In other examples, the number of contact locations may be three, four or more. In this context, a contact location refer to a point contact, or contact over an extended area. In yet other examples, contact may be made substantially continuously around the circumference of the rear end of the ferrule sub-assembly, in the finished connector.

[0073] In the illustrated examples, the ferrule biasing arrangement is shaped so as to surround the optical fibre on three sides, while remaining permanently open on the fourth side, to allow entry of the cable in a transverse direction. In the illustrated examples, the open side of the ferrule biasing arrangement is aligned with the opening of the longitudinal slot in the connector rear body. In other examples, the open side of the ferrule biasing arrangement may be oriented differently, being fitted into the connector rear body and around the cable at a time after the cable has been introduced into the longitudinal slot.

[0074] In yet other examples, the ferrule biasing arrangement may be formed so as to have an opening at the time it is fitted around the cable, but then completely surrounds the cable in the finished connector. For example, the ferrule biasing arrangement may be made of two or more parts which are fitted around the cable from different sides. For example, instead of a single U-shaped insert, a pair of U-shaped inserts could be fitted around the cable from opposite sides so as to become stacked in the longitudinal direction. In another example, an insert made of an elastomeric material may be formed in two semicircular halves, or may be sufficiently deformable that it may be formed with a slit which is prised open temporarily to admit the optical fibre.

[0075] Many other arrangements may be envisaged, while a single insert clearly has the attraction of simplicity and low cost. The fitting of the ferrule biasing arrangement around the cable may be done before or after the cable is inserted into the connector rear body. On the other hand, if the ferrule biasing arrangement is pre-fitted in the rear body, this simplifies the steps required to assemble the finished connector in the field.

[0076] In the illustrated examples, the ferrule biasing arrangement comprises a resilient insert formed of for example of metal. The metal insert is conveniently manufactured by pressing from sheet material. However, a metal resilient insert can of course be formed in some other way into a resilient shape, for example by bending and folding wire and / or sheet material. Where the resilient insert is made of metal, the metal may be for example stainless steel or beryllium copper.

[0077] In other examples, the ferrule biasing arrangement may comprise by one or more pieces of material whose bulk properties provide the required resilience, such as an elastomeric material. Different types of materials may be combined into a composite resilient insert in a composite ferrule biasing arrangement, made in one or more pieces.

[0078] In the illustrated examples, the ferrule biasing arrangement comprises a single resilient insert. In other examples, however, a different form of insert, and / or multiple inserts may be provided to make up the ferrule biasing arrangement. For example, in other examples, two or more resilient inserts may be stacked in the longitudinal direction, so as to increase the permitted travel of the ferrule when pressed against another connector. In other examples two or more resilient inserts may be fitted around the cable from two or more transverse directions, so as to cooperate in applying a forward biasing force at multiple angular locations around the longitudinal axis of the ferrule sub-assembly.

[0079] In the illustrated examples, the resilient insert is received within a slot formed in the rear body. The resilient insert may be supplied already fitted within the rear body, or it may be supplied separately, for an installer to insert. The resilient insert may be encapsulated within the rear body during its manufacture, for example by over-moulding. A resilient biasing arrangement may likewise be formed by co-moulding a rigid plastic material with portions of an elastomeric material positioned to engage the rear end of the ferrule sub-assembly. In the illustrated examples, the rear body extends some distance forward of the ferrule biasing arrangement, partially enclosing the ferrule sub-assembly. The longitudinal slot accordingly has a rear portion for receiving the optical fibre and a front portion for receiving a rear end of the ferrule sub-assembly. In other examples, a front end of the rear body may coincide substantially at the location of the ferrule biasing arrangement, while the ferrule sub-assembly is housed and supported in a front body part that mates with the rear body.

[0080] In the illustrated examples, the longitudinal slot in the rear body is closed in a rear portion when the boot is fitted. In a front portion, the longitudinal slot is closed when the front body part referred to as the inner shroud is fitted. In other examples, the longitudinal slot may be closed by other means, separate from any boot or rear body. The rear body may for example be formed in two parts that assembled together to close the longitudinal slot around the optical fibre.

[0081] The rear body of the connector may be made for example as a moulded plastic part. In the illustrated examples, the ferrule biasing arrangement is formed by a material different to the material of the connector rear body in which is supported. In other examples, the ferrule biasing arrangement may be formed by shaping the material of the connector body itself to have a resilient biasing function. The material from which the rear body is moulded in that case may be selected differently to a simple connector rear body, in order to have sufficient strength and resilience to provide the required spring force under multiple operations.

[0082] In the illustrated examples, the type of connector to be fitted on the installed optical fibre is of the standard SC type. The skilled person will recognise that the devices and techniques disclosed herein are in no way limited to that specific type of connector and can be readily adapted to other types of connector where an optical ferrule is to be biased, including for example standard LC connectors and other connectors, whether known at the present day or developed in the future. The forward biasing force exerted by the ferrule biasing arrangement, as well as the length of travel permitted, can be determined to comply with the relevant specifications for each type of connector. For example, in an LC connector the forward biasing force (ferrule compression force) should be in the range 5.0 N to 6.0 N, when mated. For an SC connector the ferrule compression force should be in the range 7.0 N to 11 .8 N.

[0083] The above examples and variations are by no means limiting on the range of examples that can be provided, within the scope of the present disclosure. No limitation of the scope of protection is intended by the presentation of some examples and not others. Except they are physically incompatible, any of the features and variations described above can be provided in combination with any of the other features and variations, without departing from the principles disclosed herein.

[0084] SUPPLEMENTARY DISCLOSURE

[0085] In some respects, the language of the present application deviates from language that was used in the priority application GB 2401305.4, while presenting the same examples and principles. For the avoidance of doubt, the disclosure above and in the drawings further includes examples as set forth in the following numbered clauses:

[0086] Clause 1. A connector for attachment to the end of an optical fibre; the connector comprising a rear body and a resilient biasing member; wherein the rear body comprises a longitudinal slot configured to allow a cable to be inserted; wherein the rear body comprises a transverse slot configured to receive the resilient biasing member, wherein the resilient biasing member has a shape configured to allow a cable to be inserted the longitudinal slot.

[0087] Clause 2. The connector of clause 1, wherein the longitudinal slot has a diameter in the range of 0.90 to 2.00mm.

[0088] Clause 3. The connector of clause 1 or clause 2, wherein the connector does not comprise a spring extending from the ferrule holder.

[0089] Clause 4. The connector of any of the above clauses, wherein the resilient biasing member is a resilient biasing clip, wherein the resilient biasing clip comprises a deflectable tine.

[0090] Clause 5. The connector of clause 4, wherein the resilient biasing clip comprises two deflectable tines.

[0091] Clause 6. The connector of clause 4 or clause 5, wherein the resilient biasing clip is substantially U-shaped. Clause 7. The connector of any of clauses 4 to 6 wherein the resilient biasing clip has a thickness in the range of 0.1 to 0.7 mm.

[0092] Clause 8. The connector of any of the preceding clauses, wherein the resilient biasing member comprises stainless steel.

[0093] Clause 9. The connector of any of the preceding clauses, wherein the resilient biasing member comprises beryllium copper.

[0094] Clause 10. The connector of any of the preceding clauses, wherein the resilient biasing member is integrally formed in one piece.

[0095] Clause 11. The connector of any of clause 5, wherein the transverse slot of the rear body has a cross section formed of a first and second rectangle, wherein the first rectangle has a greater length than the second rectangle and the first and second rectangles both have lengths greater than the diameter of the longitudinal slot.

[0096] Clause 12. The connector of any of the preceding clauses, wherein the connector further comprises a ferrule holder, the ferrule holder having an internal bore.

[0097] Clause 13. The connector of clause 12, wherein the ferrule holder comprises an internal bore and wherein the internal bore has a tapered end.

[0098] Clause 14. The connector of clause 13, wherein the tapered end of the internal bore of the ferrule holder is curved.

[0099] Clause 15. The connector of clause 14, wherein the tapered end of the internal bore of the ferrule holder is tapered in a concave curve.

[0100] Clause 16. A connector for attachment to the end of an optical fibre; the connector comprising a rear body and a resilient biasing member; wherein the rear body comprises a longitudinal slot configured to allow a cable to be inserted; and wherein the rear body and the resilient biasing member are integrally formed. Clause 17. A kit of parts comprising the connector of any preceding clause, a fibre optic blowing accessory and an installation tube, wherein the fibre optic accessory has an outer diameter between 75% and 85% of the inner diameter of the installation tube.

Claims

CLAIMS1 . A connector for attachment to the end of an optical fibre, the connector comprising a rear body and a ferrule biasing arrangement, wherein the rear body is provided with a longitudinal slot configured to allow the optical fibre to be inserted into the rear body, wherein the rear body is configured to support the ferrule biasing arrangement in a position at least partially surrounding the optical fibre so as to apply a forward biasing force to a rear end of a ferrule sub-assembly in which the optical fibre is terminated, wherein the ferrule biasing arrangement is formed with an opening, whereby it can engage the rear end of the ferrule sub-assembly at locations spaced around an optical axis of the ferrule sub-assembly without having been threaded over the optical fibre or the ferrule subassembly.

2. A connector as claimed in claim 1 , wherein the ferrule biasing arrangement comprises at least one resilient insert formed of a material different to a material of the rear body.

3. A connector as claimed in claim 2, wherein the resilient insert is formed at least partly of metal, while the rear body is formed of a plastic.

4. A connector as claimed in claim 2, wherein the resilient insert is formed at least partly of an elastomeric material, while the rear body is formed of a relatively rigid plastic.

5. A connector as claimed in any of claims 2 to 4 wherein the resilient insert is received in a transverse slot within the rear body.

6. A connector as claimed in any of claims 2 to 5, wherein the resilient insert is substantially U-shaped.

7. A connector as claimed in any of claims 2 to 6, wherein the ferrule biasing arrangement is integrated with the rear body, either by over moulding or co-moulding the resilient insert with material of the rear body.

8. A connector as claimed in claim 1 wherein the ferrule biasing arrangement is formed integrally with the rear body, by forming one or more resilient elements from material of the rear body itself.

9. A connector as claimed in any preceding claim, wherein the ferrule biasing arrangement is formed in one piece.

10. A connector as claimed in any preceding claim, wherein the ferrule biasing arrangement comprises at least one deflectable tine.

11. A connector as claimed in claim 10, wherein the ferrule biasing arrangement comprises at least two deflectable tines.

12. A connector as claimed in any preceding claim, further comprising at least one front body part, the front body part being formed so as to mate with the rear body after an optical fibre has been fitted into the longitudinal slot and to hold a ferrule sub-assembly in engagement with the ferrule biasing arrangement.

13. A connector as claimed in any preceding claim, wherein the ferrule biasing arrangement is adapted to apply a forward biasing force in the range of 5 to 12 N over a predetermined range of rearward travel of the ferrule sub-assembly, for example a force in the range 5 to 6 N or a force in the range 7 to 12 N.

14. A connector as claimed in any preceding claim, wherein the ferrule biasing arrangement is adapted to apply a forward biasing force to the rear end of the ferrule subassembly over a range of at least 0.4 mm travel.

15. A kit of parts comprising a connector as claimed in any preceding claim together with a ferrule sub-assembly adapted to be received in the longitudinal slot of the rear body and having a rear end adapted to engage the ferrule biasing arrangement, when assembled.

16. A kit of parts as claimed in claim 15, further including an optical fibre cable, wherein the ferrule sub-assembly has been fitted to terminate an optical fibre at one end of the optical fibre cable.

17. A kit of parts as claimed in any of claims 17 to 19, further including an installation duct, wherein the optical fibre cable including the ferrule sub-assembly has been installed in the installation duct.

18. A method of installing an optical fibre in an installation tube, the method comprising: providing an optical fibre terminated at a leading end with a ferrule sub-assembly; inserting the leading end of the optical fibre including the ferrule sub-assembly into an installation tube; propelling the connector and the attached optical fibre along the length of the installation tube to a distal end thereof; and at the distal end of the installation tube, assembling a connector around the ferrule sub-assembly, the connector including a rear body and a ferrule biasing arrangement as claimed in any of claims 1 to 14.

19. A method as claimed in claim 18, wherein the propelling step is performed at least partly by blowing.

20. A method as claimed in claim 18, wherein the propelling step is performed primarily by pushing.

21. A method as claimed in any of claims 18 to 20, wherein the installation tube has an inner diameter between 2 mm and 5 mm, for example between 2 mm and 4 mm.

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