Method of and apparatus for managing a length of optical fibre

The invention relates to a method of and apparatus for managing a length of optical fibre.

The invention provides a method of managing a length of optical fibre including the steps of:

housing the length of optical fibre in a duct, the length of optical fibre being so coiled as to extend along the duct, the coils of the optical fibre being free to expand, under the natural tendency to straighten, restrained by the inner periphery of the duct, providing a plurality of modules removably attached to the outer periphery of the duct at intervals along the duct, locating a plurality of devices in the modules, for attachment to the length of optical fibre at a plurality of positions adjacent to the modules and connecting the length of optical fibre to selected ones of the devices in the modules.

Preferably, the method includes the step of

providing a length-wise slot in the duct and connecting the length of optical fibre through the slot to selected ones of the devices in the modules.

Preferably, the method includes the step of withdrawing selected devices by detaching the modules containing the selected devices from the duct.

Preferably, the method includes the step of returning the selected devices by attaching the modules containing the selected devices to the duct.

Preferably, the method includes the step of including a plurality of fibre-joining devices in the modules.

The invention also provides an apparatus for managing a length of optical fibre including:

a coiled length of optical fibre. a duct the inner periphery of which is of a size and shape to house the length of optical fibre so coiled as to extend along the duct, the coils of the optical fibre being free to expand, under the natural tendency to straighten, restrained by the inner periphery of the duct, a plurality of modules removably attached to the outer periphery of the duct at intervals along the duct and a plurality of devices in the modules, for attachment to the length of optical fibre at a plurality of positions adjacent to the modules, the length of optical fibre, when housed in the apparatus, being connected to selected ones of the devices.

Preferably, the apparatus includes a length-wise slot in the duct, the length of being connected through the length-wise slot to selected ones of the devices.

Preferably, the inner periphery of the duct is of a size and is so contoured as to allow the coils of the optical fibre to expand to a radius of about the minimum fibre bend-radius required for satisfactory signal transmission.

Preferably, the inner periphery of the duct is cylindrical.

Preferably, the devices in the modules include fibre-joining devices.

A method of and apparatus for managing a length of optical fibre will now be described by way of example only with reference to the accompanying drawing.

The apparatus includes a cylindrical duct 1 having a length-wise slot making the inner periphery of the cylindrical duct accessible through the slot. A first module 2 is removably attached to the outer periphery of the cylindrical duct 1 and contains a first fibre-joining device 3 . A second module 4 is removably attached to the outer periphery of the cylindrical duct 1 and contains a second fibre-joining device 5 . A length of optical fibre 6 is housed in the cylindrical duct 1 and is so coiled as to extend along the cylindrical duct 1 , the coils of the optical fibre being free to expand, under the natural tendency to straighten, restrained by the inner periphery of the cylindrical duct 1 . The first module 2 is spaced from the second module 4 along the cylindrical duct 1 by about the coiled length of the optical fibre 6 which is attached, at one position, to the adjacent first fibre-joining device 3 and, at another position, to the adjacent second fibre-joining device 5 .

The specific manner in which the first module 2 and the second module 4 are removably attached to the cylindrical duct 1 is not shown in the drawing but may include ribs on the outer periphery of the cylindrical duct 1 into which the first module 2 and the second module 4 are removably clipped. Other means of removable attachment may also be used.

The optical cable 6 extends through the slot in the cylindrical duct 1 enabling connection to the first and second fibre-joining devices 3 and 5 .

The maintenance of the optical fibre 6 requires that the fibre-joining devices 3 and 5 should be accessible for servicing and other purposes. The first fibre-joining device 3 may be removed by withdrawing the first module 2 , at which time a part of the length of optical fibre 6 adjacent to the first fibre-joining device 3 is readily pulled from the cylindrical duct 1 because of the coiled lay-up of the optical fibre 6 . Similarly, on the return of the fibre-joining device 3 , the part of the length of the optical fibre 6 pulled from the cylindrical duct 1 is readily replaced in the cylindrical duct 1 and returns to the coiled lay-up. A corresponding situation exists in relation to the removal and return of the cable-joining device 5 .

There is a minimum fibre bend-radius for satisfactory operation of the length of optical fibre 6 and the size and shape of the inner periphery of the duct 1 are so chosen as to permit the coiled length of optical fibre 6 to meet the restrictions on fibre bend-radius. A cylindrical inner periphery for the duct 1 is satisfactory and it will be appreciated that minor departures from truly cylindrical are satisfactory. An inner periphery of oval transverse cross-section for the duct 1 is also satisfactory. Also satisfactory are other transverse cross-sections which permit the coiled length of optical cable to be cylindrical or near-cylindrical.

The width of the slot in the duct 1 in relation to the width of the duct 1 is a matter of the balance between housing the optical fibre 6 effectively and the ease with which an appropriate amount of the optical fibre 6 may be withdrawn with a fibre-joining device 3 or 5 .

The slot may be omitted altogether and connection made through the open ends of the duct but the absence of a slot makes the removal of fibre-joining devices more complicated, although such removal is then still possible.

The accompanying drawing shows only modules 2 and 4 and fibre-joining devices 3 and 5 but it will be understood that many more modules and fibre-joining devices may be employed according to the length of the optical fibre 6 . Connection of the optical fibre 6 to devices in the modules other than fibre-joining devices is possible.