AU5942000A - Process for cutting an optical fiber - Google Patents

Description

1

AUSTRALIA

Patents Act 1990 The Whitaker Corporation

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT

C

C

C

C C *A C Invention Title: Process for cutting an optical fiber The following statement is a full description of this invention including the best method of performing it known to us:- PROCEss FOR CUTTING AN OPTICAL FIBER BACKGROUND OF 1 TE INVENTION Fie1fQ: the Invenrition S The invention relates to a process for cutting at least one optical fiber at one or more predetermined =ngles to form angled or shaped end faces that require no polishing.

Descriotion of the Prior Art Optical fibers made of glass are often u.sed in optical o transmission systems and other optical systems. The machining of the end face of these fibers plays a crucial role during the use of these monomode or multimode fibers. It is iaportant that the end faces have a particularly uniform sirface so that the transition from one fiber end to another or to an active element can be carried our- with damping values which are as low as possible. It is also important that the end faces of the fibers can be produced at predeteinined angles and that these angles are reliable and reproducible.

various mechanical processes are cur'rently nowi fEor severing optical fibers. With all procespes, the fiber is essen~tially fixed in a holding device consisting Of two holders which are then mutually offset, for examnPle, so that the correct angle-is en~sured during the cutting operation.

Diamond cutters, for example, are used. it is also kn~own to twist the fiber or begin to cut and then break the fibers which are to be out. All. these processes are expensive. In addition, they are alsmo applicable to she paral.lel fibers of -7 a ribbon cable only under certain conditions. It is %nown fromi EP 531,225 that in order to sever an optical fiber, the optical fiber may be fixed betweexi two carriers of a holding and positioning device, then one of the carriers is offset perpendicul~arly to the optical- axis 9* of the fibers and a cutting blade is used to cut the fibers at a desired angle. This process can also be used for the number of fibers in a ribbon cable which are arranged_ parallel to one another.

SIInThZAY OF TH~E INV=NTIN It is an object of the invention to provide a process for cutting at least one optical fiber at one or more partici2lar anigleri or with~ a particular shape with a high degree of accuaracy.

The object is achieved by a process having the characteristics of claim 1. The sub-claimsl provide *9 advantageous developmnts.

5 With the process according to the invention for the cutting of at least one optical fiber at onie or more predetermnined angles the fiber is held in a holding and positioning device and the fiber is then cut by means of a laser which delivers short, highpwe ulses while the holding and positioning device moves the fiber relative to the laser. As a reoult, a fi.ber end face can be produced **accurately with a predetermined angle or ahape and with Such surf ace uniformity that additional machining of the fiber end face is unnecessary.

It is also particularly advantageous that only a minin&I1 quantity of glass is melted during the cuttinlg of the fiber.

4 The holding and positioning device of the present invention is designed so that the fiber is fastened therein- Preferably, the device is configured to move the fiber at one or more predetermined angles relative to the laser beam, althouigh it is within the scope of the present invention to move the laser beam relative to the fiber.

The angle at which the be=m crosses the fiber can be selected to shape the erid face of the fiber. For example, in a simple configuration, the device moves the fiber across the beam in a single pass to form a plan-ar end face. The planar end face may be normal to the axis of the fiber, or it may be angled to the axis such that the end face of the fiber serves to change the direction of the light exiting or entering the fiber. In more complex configurations, the device moves the fiber across the beam at different angles in one or more passes to form a multifaceted or curved end face. Preferred end face shapes include, for example, a wedge shape formed by two opposing cuts. in practice, the wedge shaped will tend to be blunted due to surface tension of the softened fiber during cutting. The blunted wedge shape therefore acts a cylinder-type lens at the fiber end.

Such a configuration is well suited for optically coupling the fiber with a laser having an elliptical beam.

The laser beamn used for cleaving the fibers is preferably provided by a CO 2 laser, although other lasers, such as excimer lasers, miay be used, C0 2 lasers have proven particularly advantageous due to the high speed ar. which they can operate and the resultant cost effectiveness. The fiber m~aterial is removed by ablation by the CC, laser of during the cutting process, such that, rather than mnelting, the glass is sublimnatedi.

CO, laser is operated preferably in a pulsed mode...

for cutting the fiber. The pulse energy is very high. The pulses are ver-y shor t and have very steep edges, thus, the* maximum pulse energy is achieved very rapidly. F'or example,

I:

suitable results have been achieved in which the peak power of the pulse is between about 0.1 and about 1000 watts and e the pulse length is greater than about 50 fs. Very good results are achieved with a CO, laser (wavelength 10.G im having a pulse length of 35 j.4s and a peal< power of 00 watts, Other lasers with wavelengths between 0.1 and 1.5 g.m and 8.5 ~Im to 10 ,jAM can also be used.

6 Whereas former mrechanical- systemns have typical angle tolerances of 0.51.4, angle tolerances of less than 0.2m.

can be achieved with the proceas according to the invent~ion.

With the present process it is possible to cut not only individual fibers at an angle, but also fibers of a ribbon cable. Furthermnore, whe2 eas former mechanical systems were relegated to just straight cuts, thae process of the present j.vention enableo the fiber ends to be cut into any desired ahape.

~BRTRF DESCRIPTION~ OF TH.E DRAWINGS Figure I. is a schematic view of an optical waveguide with a coordinate syste n and a larmer beam; V* Figure 2 is a cross section through one end of an

C.

optical waveguide; Figure 3 is a schemnatic view of optical waveguides of a ribbon cable fastened in a holding and positioning device; and Figure 4 is a schematic view of a wedged-sh5~ped end of a fiber prepared using the laser cleaving of the present invention.

7 DETAILED DESCRIPTION OF THE PREFERRD EMBODIMENT A laser 14 from which a laser beam L. issues is initially required for carrying out the process of cutting a fiber 3. The laser beam L. is concentrated by a lens 1. The laser beam once concentrated in this way, impinges on the optical fiber 3. The optical fiber 3 is a glass fiber, for example a monomode or Multimode fiber. As shown in Fig. 2, the fiber 3 consists of a fiber core 4 and a fiber sheath S so that the light is guided substantially in the fiber core 4. The fiber 3 is arranged in a holding and positioning device and is positionable relative to the laser Lx. For example, it can be orientated along the axis ay and thenri be moved along the axis X relative to the laser beam L. using microtranslators on the holding and positioning device. 15 However, it is also possible for microtranslators of the holding and positioning device to move the fiber 3 along the axis ax or any other angle or combination of angles and curves relative to the laser beam. As shown in Fig. 2, a surface 6 of the fiber 3 is produced at an inclination angle co the fiber axis. The angle of inclination should be accurately reproducible, and this is achieved by the proposed process. For carrying out the process, the laser 8 transmiits short high-energY Pulses Of laser light, so that the material of the fiber is Sublimatedl.

A very accurate and high quality surf ace of the f iber is achieved by Tlasex cutting", so additional machining of the fikDer surface aft~er cwting, as is normal wizh mechanical cuttin~g processes, is no lonxger necessairy. The fiber end face 6 is finished sufficiently after cutting with the laser As. shown in Fig. 3, with the process accordi~ig to the 341vention, it is po,5sible to cut not only an individual fiber and adeqi.~aely finish the end surface at the same C. timte, bu~t also a bundle of fibers 3 orientated parallel to *one another (for excample, a ribbon cable) simultaneously 00 C 0-09.9wit.h the samne surface qualities. For this purpose, the fibers 3 that make up a bundle are introduced into a 00 positoninflg devi~ce 7. The positioning devi.ce 7 ensures thqt s the fibers :3 are arranged parallel to one another. Thelongitudinal axis of the fibers 3 coincides, for example.

wit~h the X-axis off a coordinate systemn. T~he positiconing device 7 can monw be driven along the direction off the Y-axis in a m~anner that ensures that the fibers 3 remnain in parallel orientation.

A laser beaMn which in this embodiMent is inclined by an angle a to the Z-axiS, is concenitrated Qonto the fibers 3 by means of a Lerns I and operated in a mode with short high-energy pulses described above. The fibers 3 pass th-rough the laser beam L. and are thus cut and the end faces finished.

As shown in Figure 4, laser cleavings of the Present invention can be used to formn a wedged-sh~.ped fiber end 41.

This wedge shape was formned by passing the fiber through the :trr.laser beamn at different angler., The wedge shaped fiber e~rad 41 is slightly blunted p~cesumably due to surface tension of the softened fiber during laser ablation. The blunted wedge shape therefore presents a cylinder-type lens 42 at the fiber end. Such a configairation. is well suited for optically coiipling the fiber with puimp-type lasers or ozher devices which emit or receive an elliptical beamn of light, Advantageously, this process ensures that all fib~rs of the ribbon cable are cut at the same angle with an equally high end face quality

Claims (13)

1. A process for cutting at least one optical fiber, the process comprising the steps of: introducing the fiber into a holding and positioning device; actuating a laser device to deliver the beamn in short high-power pulses; and effecting the relative movement of the beam across the fiber at one or more predetermined angles. 9 oooo ooo

2. The process according to claim i wherein a plurality of fibers are introduced into the holding and positioning device parallel to one another and moving the beam across 0 the plurality so that the fibers are cut in succession, 99ooo

3. The process according to claim 1 wherein the fiber is a ribbon fiber having multiple fibers therein. 99 9 9

4. The process according to claim I wherein the laser is a Co laser.

Ii The process accordin to claim 4, wherein the laser device delivers -pulses with peak power between about 0.1 and about I000 watts and the pulse length is greater th.an 50 fs.

6. The process according to claim 4, wherein ths laser device delivers pulses at a wavelength of 10.6 gm hAving a peak power of 600 watts and a pulse length of 35 /2s

7. The process according to claim 1, wherein said beam is Moved across the fiber at only one predetermined angle.

S. The process according to claim 1, wherein said beam is moved across the fiber at two or more predetermined angles to shape the end face of the fiber *O ooo"

9. The process according to claimn 8, wherein paid beam is moved across the fiber at two predetermined angles to shape a wedge on the end face of the fiber.

The process according to claim 1, wherein said beam is moved across the fiber at preeternined angles to effectively shape a curve on the end fce of the fiber. 12

11. A fiber' prepared in accordance with the proceso of claimr 1

12. A fiber' prepared in accordance with the process of cl.aim 7.

13. A fiber' prepared in accordance with the process of. claim a. DATED THIS 13 DAY OF SEPTEMBER 2000 THE WHITAKER CORPORATION Patent Attorneys for the Applicant: F.B.RICE CO