WO2002077685A1

WO2002077685A1 - A method and an arrangement for supplying optical fibers

Info

Publication number: WO2002077685A1
Application number: PCT/SE2002/000583
Authority: WO
Inventors: Jan-Åke ENSTRAND; Jap Hoen; Magnus Larsson
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2001-03-22
Filing date: 2002-03-22
Publication date: 2002-10-03
Also published as: SE0101005D0; SE519712C2; SE0101005L; TW525325B

Abstract

A method and an arrangement in which optical fiber lengths (13) are mechanically unwond form a fiber drum (23) in the axial direction in the process of preparing the fiber lenghts (13) for different applications e.g. connection to microelectronic devices. The fiber is unwound by initial lifting the fiber in the radial direction of the drum and subsequent guding of the fiber axially along the drum by an unwinding means (27) and is discharged at the center of one side of the drum. The method and arrangement include monitoring steps for measuring light influenced by a prepared lenght at the second not unwound fiber end on the durm by menas of a light processing apparatus (42) and comparing the actual value of an optical parameter of the influenced light to a preset value.

Description

A METHOD AND AN ARRANGEMENT FOR SUPPLYING OPTICAL FIBERS

TECHNICAL FIELD The invention relates to a method and an arrangement for mechanically supplying an optical fiber to a fiber preparation unit comprising unwinding lengths of said fiber from a fiber drum and monitoring at least one optical parameter of a prepared fiber length.

BACKGROUND OF THE INVENTION

Optical fibers are in common use in connecting various kinds of microelectronic devices such as DFB (Distributed Feed Back) laser modules, PIN (P- Intrinsic N- diode) and APD (Avalanche Photo Diode) based receiver modules and integrated transmitter modules. Normally the optical fibers have to be adapted or prepared in many ways before they can be connected to the devices. The fiber ends are subjects for different tapering, grinding or cutting methods in order to achieve the best possible light transmission and the fiber lengths are often subjects for special splicing or grating preparation. One part of the over-all process is to supply fiber lengths from a fiber drum and another part is to check the fiber lengths after they have been prepared according to any such method.

One known way of supplying fiber lengths is to unwind the fiber from a storage drum in the radial direction by rotating the drum in a traditional way. Another known way is to unwind by hand from a fixed drum. The monitoring of the prepared fiber length is normally omitted or conducted as a special step after the length has been cut. None of these methods are suitable for large-scale industrial production.

SUMMARY OF THE INVENTION The increasing use of fiber optics together with microelectronics has revealed the problem that there are no production methods that are suitable for larger scale production of fiber units for connection to microelectronic devices. Another problem is that known methods do not give reliable and even quality on the produced fiber lengths and many lengths have to be rejected and scrapped.

For that reason, one object of the present invention is to achieve a method and an arrangement that give the possibility of large scale industrial production of fiber lengths prepared for different applications e.g. connection to microelectronic devices. Another object is to provide a method and an arrangement that give the possibility to mechanically unwind fiber from a fixed fiber storage drum and still another object is to achieve a method and an arrangement that enable running control of quality of the prepared fiber lengths.

Briefly, these objects of the present invention are accomplished by a method and an arrangement in which optical fiber lengths are mechanically unwound from a fiber drum in the axial direction in the process of preparing the fiber lengths for different applications e.g. connection to microelectronic devices. The fiber is unwound by initial lifting the fiber in the radial direction of the drum and subsequent guiding of the fiber axially along the drum and is discharged at the center of one side of the drum. The method and arrangement include monitoring steps for measuring light influenced by a prepared first length at the second not unwound fiber end on the drum by means of a light processing apparatus and comparing the actual value of an optical parameter of the influenced light to a preset value.

An advantage of the present invention is that it enables gentle unwinding from storage fiber drums under continuos monitoring of the subsequent end or length shaping method. Another advantage is that disapproved lengths can be detected immediately and will not cause more expensive discarding in connection with the final assembly and control. A further advantage is the possibility to have a fully automatic production and means for running correction of the same without any interruptions. Yet another advantage is that all kinds of preparations including splicing that give variation in the light reflection or attenuation can be monitored by one and the same equipment. Still another advantage is that the unwinding means can easily be adapted to different storage drums and fibers.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described more in detail with reference to the following drawings, in which:

Fig. 1 shows schematically a perspective overview of an arrangement according to the invention,

Fig. 2 shows schematically a perspective view of an unwinding means and fiber storage drum included in the arrangement according to Fig. 1, Fig. 3 shows schematically perspective view of a fiber positioner device included in the arrangement according to Fig. 1 or 2, Fig. 4 shows a cross section according to line A-A in Fig.3 Fig. 5 shows a cross section according to line B-B in Fig.4 and Fig. 6 shows an enlarged detail within circle C in Fig. 4.

DETAILED DESCRIPTION OF THE INVENTION In Fig. 1, a fiber length preparation unit 11 is schematically shown. The unit includes a displacing apparatus 12, for moving fiber lengths shown by the dotted line 13, between different workstations 14-18 arranged on a working table 19. The displacing apparatus is preferable an industrial robot with movable arms 20 and a gripping means 21 for gripping round the fiber. The robot 12 is also arranged for pulling fiber 22 from a storage drum 23 positioned on a separate support table 24 at one side of the working table 19. The drum is carried in a fixed position on the table 24 by a drum holder 25 holding the drum axis 26 in line with the initial pulling path of the fiber length 13. An unwinding means 27 is arranged to unwind fiber from the storage drum 23 in the axial direction of the drum and lead it to a sensor device 28 at the center of one side of the drum. A fiber positioner device 29 arranged in line with the sensor device 28 forms the starting point for the unwinding of fiber lengths 13 to be prepared at the later work stations 14-18.

The unwinding means 27 is shown more in detail in Figs. 2 and 3. It comprises a rotatable axle 30 protruding the center hole 31 of the drum 23 and at one side holding a feeding arm 32 and at the other side being connected to a driving means 33 for rotating the same. The driving means, preferable an electric motor, is supported by an upright part 34 of the drum holder 25. The feeding arm 32 comprises two first portions 35 and 35' extending in the radial direction along the first side of the drum to a position outside the drum and two second portions 36 and 36' extending from that first position in the axial direction in over the drum to a second position over the fiber windings 37. Guiding means 38 e.g. wheels or rolls are arranged along said arm portions in order to lift the fiber from the drum and guide it axially along the drum to outfeed wheels forming a central discharge 39 in line with the center axis 26. The arm portions 35, 36 and 35', 36' are symmetric to each other in order to provide for counter balance and an alternative feeding path.

The second not unwound end 40 of the fiber 13 is connected to a monitoring means 41 including a light processing apparatus 42 of some known suitable kind that are able to emit light into the end 40 and measure light after reflection or otherwise being influenced by the unwound and prepared fiber length 13. The purpose of the monitoring means is to control the preparation of the fiber before the fiber length 13 pulled out is cut off. This is done by using the well known fact that each particular fiber configuration causes typical light characteristics and that also quite small deviations from an ideal end form give rice to a difference that can be detected by the light processing apparatus 42. The transmitted or reflected light can be measured in many way e.g. simply by measuring the intensity and then the change between the sent light and light influenced by the prepared end can be registered by some chosen optical parameter. Ideal values of the parameter are found by experience and are registered in the apparatus 42. The actual values are then compared to said preset ideal values and all fiber lengths that do not comply with the ideal values are displaced by the gripping means 21 and cut off by a cutting device (not shown) arranged on the working table 19.

The fiber positioner device 29 is shown more in detail in Figs. 3-6. It comprises a holder 43 that is movable along a track 44 attached on the working table 19. A pair of jaws 45 are arranged to grip and hold the fiber close to a first unwound end 46 of it and the holder 43 is arranged to move the jaw device 45 between a first position 47 close to a fiber brake means 48 and a second position 49 (shown in Fig.3) at a distance from said first position. The brake means includes a head 50 positioned in line with the jaw device 45, said head containing a through hole 51 for the fiber. The hole has a square cross section with one corner 52 connected to a vacuum line 53 by means of a narrow slot 54 along at least a part of the whole length of the hole 51. The slot is arranged to submit negative pressure to the corner 52 and press the fiber against the internal wall of the hole when the vacuum system 53 is activated.

The sensor means 28 is also arranged on the working table 19 and comprises a stand 55 with three wheels 56-58 mounted one after the other on a horizontal part 59 of the stand. The first and the last wheels 56, 58 have fixed axles whereas the middle wheel 57 is free to move a certain distance in the vertical direction, between a lower stop position and a higher start position. As shown in Fig. 2, the fiber is arranged to run on the upper side of the fixed wheels 56, 58 and on the under side of the vertically movable wheel 57. When a certain tension is applied to the fiber, the middle wheel is lifted upwards and at the same time a not shown contact means is activated and sends a signal to the drum driving means 33 ordering it to start rotating the axle 30.

The method of supplying fiber to a fiber end preparation unit starts with the step of pulling out a new length from the fiber drum 23. The starting position is shown in Fig. 2 in which the first end 46 of the fiber is held by the jaw device 45 in its first position close to the fiber brake means 48. At that position the brake is activated and the vacuum holds the fiber in a firm but not totally fixed position and the jaws grip round the fiber end. The holder 43 is then moved on the track 44 to the second position at a distance from the fiber brake means 48 as shown in Fig. 3. The brake is activated during the move and keeps the fiber stretched between the jaw device and the brake. Then the robot 12 is started and places its gripping means 21 round the fiber between said jaw device and brake means. The fiber is very sensitive to damages so it is important to position the gripping means exactly round the fiber. This is facilitated by the fiber brake that holds the fiber stretched and easily defined by the robot. When the gripping means has a fixed grip round the fiber the jaws 45 can release their grip and the robot is activated to pull out a full fiber length 13 in a straight moving path along the working table. During the move, the fiber brake is applied in order to keep the length stretched. The brake is, however, not so firmly applied that it could course damages to the fiber coating.

As soon as the fiber is started to be pulled out and stretched, the middle wheel 57 in the sensor means 28 is lifted as described above and a signal is sent to the unwinding means 27 to start its operations. More in detail, the driving means 33 begins to rotate the axle 33 and the feeding arm 32 with its protruding second portions 36 round the fixed storage drum 23. The guiding means 38 in the form of wheels or rolls lifts the fiber from the drum by the same time the arm 32 is moved and the fiber is then guided between the wheels to the central discharge 39 in line with the rotating axis 26. When the pulling action is finished the middle wheel 56 again falls down to its lower position and initiates a stop signal to the unwinding means 27.

After the fiber length is fully pulled out, the robot moves the first fiber end 46 between the work stations 14-18 in order to prepare the fiber end for connection to different optoelectronic devices. At first the end is moved to a stripping and cleaning station 14, then continuing to a tapering or cutting station 15 or 16. After that further stations like a dipping station 17 and a storage station 18 might be included. It is also possible to arrange other stations in the total system, like a splicing station for connection of the first end to another fiber end or for joining two parallel fiber lengths to a four-way connection e.g. by fusing biconic tapers. A further station could be a grating unit for submitting special light attenuation properties to the fiber length. After stations including tapering, cutting, splicing and grating preparation it is as mentioned earlier important to control that the fiber end, the connection or the prepared fiber part has received the expected form and properties. For that reason the light processing apparatus 42 measures light influenced by the prepared fiber length in the way described above and only approved lengths are allowed to go to next stations. If e.g. an end is disapproved, it is cut off and the robot pulls out a further bit of fiber to achieve a new full length and the end preparation starts again. Approved fiber lengths are cut off at the positioner 29 and delivered to the storage station 18. Before said cut is done, the prepared fiber is again gripped by the jaws 45 after the holder 43 has been moved to its first position 47 at the breaking means 48. The robot with its gripping means 21 still holding the first end then stretches the length and a not shown cutting device cuts the fiber close to the holder. By that way the produced fiber units will have exactly the same length which is important for the future installations. Now the fiber length preparation is finished and a new supplying and preparation cycle can be started.

It should be noted that the fiber end preparation unit according to the shown embodiment is only one example of such units that can be supplied with fiber lengths according to the present invention. There are many other forms of fiber treatments that are suitable for supply in the same way. It should also be clear that two or more supply arrangements can be installed at the same fiber length preparation unit and that they can be interconnected e.g. in a splicing monitoring arrangement. In that case one light processing apparatus can be a light source for emitting light into one end of the connected fiber lengths and another apparatus can be the light receiver and monitor.

Claims

1. A method of mechanically supplying an optical fiber to a fiber preparation unit comprising unwinding lengths of said fiber from a fiber drum and monitoring at least one optical parameter of a prepared fiber length characterized by the steps of:

- unwinding the fiber in the axial direction of the fiber drum (23) by initial lifting of the fiber in the radial direction of the drum and subsequent guiding of the fiber axially along the drum,

- discharging the fiber at the center (39) of one side of the drum, - connecting the second not unwound end (40) of the fiber on the drum to a light processing apparatus (42),

- measuring light influenced by the prepared length (13) and

- comparing the actual value of the optical parameter of said influenced light to a preset value.

2. The method according to claim 1 , characterized by initiating the step of unwinding by pulling the fiber in the axial direction from the drum and submitting the pulling tension to a sensor means (28) for starting the unwinding mechanics (27).

3. The method according to claim 1 or 2, characterized by holding the first fiber end in a fixed position before each fiber length is pulled out and unwound.

4. The method according to anyone of claims 1 to 3, characterized in that the lifting and guiding substeps are performed by a feeding arm (32) attached to a rotatable axle (30) in the center of the drum (23).

5. An arrangement for supplying an optical fiber to a fiber preparation unit comprising unwinding means for unwinding lengths of said fiber from a fiber drum and monitoring means for monitoring at least one optical parameter of a prepared fiber length characterized in that - the unwinding means (27) is arranged for unwinding the fiber in the axial direction of the fiber drum (23) and comprises a feeding arm (32) attached to a rotatable axle (30) in the center of the drum,

- the feeding arm comprises a first portion (35) attached to the axle and extending radially by one side of the drum to a position outside the drum and a second portion (36) extending axially from the first portion from said position outside the drum to a second position over the windings (37) on the drum,

- the unwinding means comprises guiding means (38, 39) for discharging the fiber at the center of one side of the drum and - the monitoring means includes a light processing apparatus (42) arranged to be connected to the second not unwounded end (40) of the fiber.

6. The arrangement according to claim 5, characterized in that a displacing apparatus (12) is arranged to pull the fiber in the axial direction from the center (39) of said one side of the drum.

7. The arrangement according to claim 5 or 6, characterized in that a drum holder (25) is arranged to hold the fiber drum in a non-rotatable position and that driving means (33) is arranged to rotate the rotatable axle (30).

8. The arrangement according anyone of claim 5, 6 or 7, characterized in that a fiber positioner (29) is arranged to hold the fiber in a fixed position in a sequence before unwinding each fiber length; that said positioner comprises a through hole (51) for the fiber and that said hole is connected to a vacuum line (53) in order to submit a friction force to the fiber.

9. The arrangement according to anyone of claims 5 to 8, characterized in that the displacing apparatus (12) comprises a gripping means (21) for gripping the fiber in its fixed position at the positioner (29); that said positioner is arranged to release the fixed position when the gripping means has gripped the fiber; and that a sensor means (28) is arranged to be activated by fiber tension caused by the displacing apparatus and start the unwinding means (27).

10. The arrangement according to anyone of claims 5 to 9, characterized in that the feeding arm (32) comprises low friction means in the form of wheels or rolls (38) for guiding the fiber during unwinding.

11. The arrangement according to anyone of claims 5 to 10, characterized in that the light processing apparatus (42) is arranged for emitting light into the prepared fiber length and/or for receiving light influenced by said length and comparing the actual value of the optical parameter to a preset value.