WO2009143632A1

WO2009143632A1 - Optical fiber connector for fiber laser

Info

Publication number: WO2009143632A1
Application number: PCT/CA2009/000761
Authority: WO
Inventors: Alex Fraser; Eric Weynant; Mathieu Bergeron; Patrick Zivojinovic; Xavier Pruneau
Original assignee: Phasoptx Inc.
Priority date: 2008-05-30
Filing date: 2009-06-01
Publication date: 2009-12-03
Also published as: KR20110036799A; EP2289133A1; AU2009253704A1; JP2011523717A; WO2009143632A8; RU2010153389A; CA2726352A1

Abstract

The present invention is directed to an optical fiber connector for fiber lasers having improved signal conduction which minimizes optical losses. This optical fiber connector is capable of operating at high power levels, by dissipating heat and by maintaining the alignment of the optical fibers even when the fibers thermally expand in the presence of high temperature. The connector may be made of a shape memory alloy having a generally cylindrical body and a longitudinal conduit for splicing together the optical fibers.

Description

OPTICAL FIBER CONNECTOR FOR FIBER LASER

TECHNICAL FIELD

The present invention relates generally to optical fiber connectors and, in particular, to optical fiber connectors for fiber lasers and, more particularly, to optical fiber connectors for fiber lasers operating at high power levels.

BACKGROUND

Lasers using a doped optical fiber as an active gain medium are being used in a growing number of applications because of their numerous advantages in comparison with other types of lasers. A fiber laser is a laser wherein the active gain medium is an optical fiber that has been suitably doped with a rare-earth element such as, for example, ytterbium, neodymium, erbium, dysprosium, praseodymium, and thulium. For example, they are compact, powerful and may be used over a wide range of emission wavelengths. The design and construction of these laser sources requires a connection of the optical fibers, including connection of the laser to optical fiber. There are two different types of connections: a fused splice or the use of a mechanical splice (or mechanical connector). In both cases, optical losses are generated. These losses in transmission at the fiber junction cause a local increase of the temperature of the optical fibers which is a limiting factor having regard to the performance level obtained. In order to avoid damage or destruction of the optical fibers and/or connectors and to transmit at a high-power level, it is necessary to minimize the optical losses and to dissipate the heat expelled from these connections in an efficient way. Indeed, an optimal connection between optical fibers will allow for higher power emission by the laser.

Accordingly, there is a need for a fiber connector that would enable optical fibers to operate at high-power levels in fiber lasers by maintaining good alignment of the fibers while also allowing heat dissipation occasioned by optical losses at the fiber junction. Optical fiber connections of the mechanical type which allow good signal conduction are described in U.S Patent No. 7,066,656 and U.S. Patent No. 7,121,731 , WO 2005/040876 published May 6, 2005 and U.S. Patent Application No. 60/943,965, all of which are herein incorporated entirely by reference. These mechanical connectors for connecting ends of two optical fibers by abutment are manufactured from shape memory material (SMM), such as polymer, ceramic or a metal alloy (shape memory alloy), with low elastic modulus. In general, such materials when deformed from a rest condition by any suitable means, such as by mechanical deformation (applied force or external pressure) or temperature increase, will be biased to return to a rest condition when the cause of deformation (force, pressure, temperature) is removed. However, the above-mentioned patents and patent applications did not contemplate the technical problem of preserving fiber alignment within the mechanical connector while still permitting heat to dissipate when these mechanical connectors are used with a fiber laser.

Various patents describe optical fiber devices capable of operating at high power levels while reducing thermal heating problems and thus avoiding damage to the fibers. For example, two approaches are described in U.S. Patent No. 5,291,570 and U.S. Patent Application No. 2007/0206909 published September 6, 2007. However, it is still desired to improve on these known optical fiber devices for fiber lasers so as to provide connectors (connection devices) having improved signal conduction with minimal optical losses. In particular, it is desired to develop an optical fiber connector capable of operating at high-power levels by not only maintaining the precise alignment of the optical fibers even when the fibers thermally expand but also enabling effective dissipation of heat.

SUMMARY

The present invention provides an optical fiber connector for a fiber laser which enables good signal conduction and minimizes optical losses, which is capable of operating at high power levels, which has the property of maintaining the alignment of optical fibers on a short distance when they are thermally expanding (as a consequence of high operating power levels) and which permits effective dissipation of heat generated by optical losses at the fiber junction. The present invention addresses the shortcomings and disadvantages of the prior art by providing an optical fiber connector made of a shape memory alloy or other shape memory material which can be used for a fiber laser where heat at the fiber splice is highly problematic.

Accordingly, one main aspect of the present invention is an optical fiber connector for splicing ends of optical fibers in a fiber laser, the connector comprising a fiber conduit dimensioned to splice optical fibers, a connector body having an axially longitudinal slot extending along a main longitudinal axis of the connector body from a first end to a second end and from an outer surface of the connector body radially inwardly to the fiber conduit, the slot and conduit expanding when a wedging force is exerted into the expansion slot, the slot and conduit contracting to grip the optical fibers when the wedging force is removed, and wherein the connector body is made of a highly elastic material that is highly heat conductive.

Another aspect of the present invention is a fiber laser comprising a pump for pumping light, a doped optical fiber connected to the pump, the pump launching light into the doped optical fiber, an outlet connected downstream to the doped optical fiber, the outlet extracting laser light, and at least one optical fiber connector dimensioned to splice optical fibers, the connector comprising a connector body having an axially longitudinal slot extending along a main longitudinal axis of the connector body from a first end to a second end and from an outer surface of the connector body radially inwardly to the fiber conduit, the slot and conduit expanding when a wedging force is exerted into the expansion slot, the slot and conduit contracting to grip the optical fibers when the wedging force is removed; and wherein the connector body is made of a highly elastic and heat conductive material for splicing the fibers and dissipating heat generated by optical losses at a splice of the optical fibers.

Yet another aspect of the present invention is a method of splicing optical fibers in a fiber laser. The method entails providing an optical fiber connector having a connector body made of a highly elastic and heat conductive material, the connector body having a first end and a second end and a longitudinally extending fiber conduit extending from the first end to the second end, the connector body having an expansion slot extending longitudinally from the first end to the second end and from an outer surface of the connector body radially inwardly to the fiber conduit, exerting a force on the connector body of the optical fiber connector to expand the expansion slot and fiber conduit, inserting two optical fibers in the fiber conduit, and releasing the force to cause the slot and conduit to contract to thus splice the optical fibers as part of the fiber laser.

Other aspects and features of the invention will become apparent from the following description of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, currently preferred embodiments will now be further described by way of example with reference to the accompanying drawings in which:

Figure 1 is an isometric view of an optical fiber connector in accordance with one embodiment of the present invention;

Figure 2 is a cross-sectional view of the optical fiber connector device in its open state showing the insertion of two optical fibers within the fiber conduit of the connector in which the optical fibers are not yet aligned;

Figure 3 is a cross-sectional view of the optical fiber connector device in its closed state showing the auto-alignment of the optical fibers within the fiber conduit of the connector;

Figure 4 is a semi-transparent isometric view of the optical fiber connector showing the insertion and alignment of two optical fibers within the fiber conduit of the connector;

Figure 5 is a graph plotting output power as a function of launched power, showing how much power is transmitted between two optical fibers (Corning SMF-28) spliced together using an optical fiber connector in accordance with one embodiment of the present invention; and

Figure 6 is a histogram or bar chart showing a distribution of splice losses measured with SMF-28 splices.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring to Figure 1 , the optical fiber connector device has a longitudinally extending connector body which may be generally cylindrical. However, although the optical fiber connector device is shown here as cylindrical, it may be of any shape which is suitable for such a device. The connector body of the optical fiber connector device has a first end and a second end. The body has a fiber conduit extending from the first end to the second end. The fiber conduit, which is shown here as round, may be of any shape suitable for insertion and splicing of optical fibers. Further, the optical fiber connector device may have a plurality of fiber conduits depending on the number of pairs of optical fibers to insert and splice together. The diameter of the fiber conduit is slightly smaller than the size of the optical fiber. The fiber conduit of the optical fiber connector device is used to hold (i.e. constrain, constrict, embrace) an optical fiber in order to enshroud and protect the fiber junction where the splice is created and to provide an adequately strong grip on the two adjoining optical fibers despite the fact that the connector only contacts the two fibers over a very short distance. In one embodiment, the connector body ("support") of the present invention has at least one axially longitudinal slot extending along a main longitudinal axis of the connector body from the first end to the second end and from an outer surface of the connector body radially inwardly to the fiber conduit. This longitudinal slot (or "expansion slot") enables the fiber conduit to expand for insertion into the fiber conduit of an optical fiber. However, it will be understood that the optical fiber connector device can be of any suitable design for retention of an optical fiber in the conduit and can be of the kind of design as, for example, shown in the aforementioned U.S. Patent No. 7,066,656 and U.S. Patent No. 7, 121 ,731, and WO 2005/040876 published May 6, 2005 and co-pending U.S. Application No. 60/943,965, all of which are herein incorporated entirely by reference. Of course, a skilled person in the art will appreciate that many minor variations and refinements can be envisaged. Accordingly, the person of ordinary skill in the art will be able to carry out any necessary mechanical modifications as may be necessary to the devices as described above for better use as an optical fiber device connector as defined herein.

Figure 2 shows how a wedge or wedging force can be applied to the expansion slot in a vertically downward direction onto the vertically upwardly facing expansion slot to cause the expansion slot to cleave open, i.e. to expand. This wedging force thus causes the fiber conduit to expand to enable insertion of the optical fibers. The connector body may include a dividing slit, not shown, that extends transversally to the expansion slot to divide the connector body into two separately operable portions. With a dividing slit, the two distinctly divided portions of the connector body can be actuated serially or sequentially to cause the divided expansion slot and divided fiber conduit to expand and then contract individually (independently) of each other.

The optical fiber connector devices in accordance with main embodiments of the present invention are made from SMM, and in particular shape-memory alloys (SMA) including those materials that may be used for manufacture of optical fiber connector devices of the type described in U.S. Patent No. 7,066,656 and U.S. Patent No. 7, 121 ,731, WO 2005/040876 published May 6, 2005 and co-pending U.S. application no. 60/943,965, all of which are herein incorporated entirely by reference. However, a skilled person will appreciate that for the novel devices of the present invention, materials suitable for the power and temperatures and the conditions associated with fiber lasers, including high power lasers, will be used.

For purpose of the present specification, with respect to SMM or SMA, reference may be made to AFNOR Standard "Alliages a memore de forme - Vocabulaire et Mesures" A 51080-1990, herein incorporated entirely by reference.

Materials, which are suitable for the optical fiber connectors described and illustrated in the previous patents and patent applications, will exhibit a very low Young's Modulus (elastic modulus) and / or pseudo-elastic effect. Pseudo-elastic effect is encountered in SMM. Concerning the shape memory effect, when the material is below a temperature (M_F), which is a property dependent on the particular SMM, it is possible to strain (deform) the material from about some tenths of a percent to more than about eight percent, depending on the particular SMM used. When the SMM is heated above a second temperature (A_F), which is also dependent on the particular SMM as well as the applied stress, the SMM will tend to recover its assigned shape. If unstressed, the SMM will tend toward total recovery of its original shape. If a stress is maintained, the SMM will tend to particularly recover its original shape. Concerning the pseudo elastic effect, when the SMM is at a temperature greater than its (A_F), it may be strained at particularly higher rates, that is, exhibiting non-used elasticity, arising from the shape memory properties. Initially, when the SMM is stressed, the strain will increase linearly, as in a used elastic material. However, at a threshold amount of stress, which is dependent on the particular SMM and temperature, the ratio of strain to stress is no longer linear, i.e. strain increases at a higher rate as stress is increasing at a lower rate. At a particular higher level of stress, the increase in strain will tend to become smaller. This non-linear effect exhibited by SMM at a temperature above (A_F) may manifest itself as a hysteresis-like effect, wherein on the release or reduction of stress the reduction in strain will follow a different curve from the one manifest as stress was increased, in the manner of a hysteresis-like loop.

An example of such above material would be a shape memory alloy (SMA). Examples concerning activation of the shape memory element in a SMA include D. E. Muntges et al., "Proceedings of SPIE", Volune 4327 (2001), pages 193-200 and Byong-Ho Park et al., "Proceedings of SPIE", Volume 4327 (2001), pages 79-87. Miniaturized components of SMA may be manufactured by laser radiation processing. See for example, H. Hafer Kamp et al., "Laser Zentrum Hannover e.v.", Hannover, Germany [publication]. All of the above references are incorporated herein by reference.

The optical fiber connector device of the present invention may, for example, be made from a polymeric material such as isostatic polybutene, shape ceramics such as zirconium with some addition of Cerium, Beryllium or Molybdenum, copper alloys including binary and ternary alloys, such as Copper - Aluminum alloys, Copper - Zinc alloys, Copper - Aluminum - Beryllium alloys, Copper - Aluminum - Zinc alloys and Copper - Aluminum - Nickel alloys, Nickel alloys such as Nickel - Titanium alloys and Nickel - Titanium - Cobalt alloys, Iron alloys such as Iron - Manganese alloys, Iron - Manganese - Silicon alloys, Iron - Chromium - Manganese alloys and Iron - Chromium - Silicon alloys, Aluminum alloys, and high elasticity composites which may optionally have metallic or polymeric reinforcement.

To connect the ends of two optical fibers using the optical fiber connector device of the present invention, the fiber conduit of the connector is enlarged (expanded) by deforming the latter in any suitable way. Without limitation, two optical fibers may be inserted into and positioned in the connector (support) in any manner as described in the aforementioned U.S. Patent No. 7,066,656 and U.S. Patent No. 7, 121,731, and WO 2005/040876 published May 6, 2005 and co-pending U.S. Application No. 60/943,965, all of which are herein incorporated entirely by reference, for the purpose of practicing the present invention. For example, an external force or pressure ("constraint") is applied to an outer surface of the connector body of the optical fiber connector to induce expansion of the fiber conduit. The optical fibers can thus be inserted into the expanded conduit. Once the optical fiber ends are fully inserted into the connector and their respective ends abut, the removal of the force or pressure (i.e. the release of the constraint) will allow the connector body to return to its original, initial shape. Upon releasing the force on the outer surface of connector body, the fiber conduit will constrict to retain the optical fibers within the fiber conduit of the connector (support). The conduit is carefully dimensioned such that when it constricts to its original shape the conduit will apply a uniform radial pressure along the outer cylindrical surfaces of the fibers. This optical fiber connector thus exerts a controlled compressive force on the optical fibers, sufficiently strong enough to retain the optic fibers in an abutment position but yet small enough not to crush or otherwise damage the optical fibers by over-compression.

There are numerous advantages in using this mechanical optical fiber connector for fiber lasers as compared to a standard fiber-fused connection, for example. This novel mechanical optical fiber connector is easier to manufacture. Furthermore, it can be used to splice two optical fibers of different composition or having different coefficients of thermal expansion (or having the same or similar composition or coefficient of thermal expansion). This property is further detailed in Kozak et al. (Low-loss glue splicing method to join silica and fluoride fibers; Electronics Letters 2005 vol. 41 (16): 21-22), incorporated herein by reference. The fiber-fused connection generally implies that the optical fibers have a similar composition and thus a similar fusion temperature. However, for certain types of optical fibers, it is difficult to obtain fusion without any optical losses (losses < 0.01 dB). For example, a fused connection for fluoride glass optical fiber (for example, Z BLAN) is not easy to obtain and usually leads to optical losses in the range between 0.1 dB and 0.5 dB. This is further detailed by Srinivasan et al. (Reproducible fusion splicing of low melting point (fluoride) optical fibers with the use of a stable heat source; OFC '97 Technical Digest, TuB l, 1997), Rivoallan and Guilloux (Fusion splicing of fluoride glass optical fiber with CO₂ laser; Electronics Letters 1988 vol. 24 (12): 756-757) and Harbison et al. (Fusion splicing of heavy metal fluoride glass optical fibers; Electronics Letters 1989 vol. 25 (18): 1214-1216). All of the above references are incorporated herein by reference. Therefore, the use of a mechanical connector made of a shape-memory material for splicing optical fibers is an innovation that provides a number of advantages relative to the prior art.

In order to minimize optical losses between optical fibers at the fiber junction when they are subject to high power levels, and thus exposed to substantial heat, the optical fiber connector device of the present invention has to maintain the alignment between the optical fibers despite thermal expansion due to exposure to high temperatures. It is important to mention that this alignment is maintained over a short distance within the length of the fiber conduit, which is at least 1 mm. The skilled person will appreciate that this has the benefit, among other things, of helping to dissipate heat efficiently. Indeed, it is known in the art that when a material is exposed to high temperature, its volume will increase proportionately with the increase in temperature depending on its coefficient of thermal expansion. Thus, the fiber connection has to account for thermal expansion ("'dilation") and contraction of the optical fibers within the connector body. In other words, the connector must adjust to thermal expansion of the optical fibers so as to preclude over-compression of the fibers that could, if the compressive forces became excessive, lead to the crushing or rupture of the fibers. Moreover, the thermal expansion (dilation) of two connected optical fibers has to be meticulously controlled and fully uniform at all times in order to maintain the precise alignment of the fibers inside the connector so as to always minimize optical losses. As is known in the art of mechanical connectors for optical fibers, there always remains a tiny gap between the canal in which optical fibers are aligned and the optical fibers itself. This gap (usually 1 or 2 microns) is necessary for the insertion of the optical fibers within this canal. Consequently, in order to obtain a stable alignment between the fibers, this gap has to be filled with glue. However, this glue is usually a thermal insulator which generally inhibits heat dissipation. Moreover, because it is difficult to obtain a uniform film of glue between the fibers and the canal in which optical fibers are aligned, the resulting film is usually an anisotropic film. This non- uniformity in the film of glue leads to differential thermal expansion between the two adjoining optical fibers. This frequently leads to rupture of the connection.

In contrast, in the present invention, no glue or adhesive is required. The novel optical fiber connector of the present invention is glueless, i.e. adhesive-free. The novel optical fiber connector of the present invention enables two optical fibers to be spliced together without glue, adhesive, or equivalent between the adjoining fiber ends or between the optical fibers and the conduit. It is solely the resiliency and super elasticity of the shape memory alloy or other shape memory material of the connector body that firmly holds the optical fibers in the fiber conduit. Since no glue or adhesive is employed in the connector, the connector is able to withstand high temperature. Since no glue is used, the connector is entirely reusable. Furthermore, since no glue is used in the connector, tiny adjustments can be made to the spliced fibers which would be problematic with a glued connection. The shape memory material combined with the novel geometry of the connector enables easy insertion, abutment and precise alignment of the optical fibers within the fiber conduit. These special characteristics of the optical fiber connector of the present invention also enable the alignment between the optical fibers to be maintained despite thermal expansion. Another important particularity of the optical fiber connector of the present invention is that the connector is always directly in full contact with the optical fiber. Moreover, in most embodiments, the connector body is made of a conductive metal, for example a shape memory alloy. The connector body therefore possesses the property of efficiently dissipating the heat generated at the splice (connection). Moreover, because of the geometry of the connector, the optical fiber connector of the present invention provides contact between the connector and the optical fibers over a very large surface area of the optical fibers. Accordingly, this geometry provides for improved contact of the connector with the optical fibers. For example, compared with a mechanical connector using a V-groove, such as Fujakura EZ Splice/FMS EZ-02, the connector device of the present invention provides a substantially larger area of contact between the connector and the fibers, thereby enabling more efficient dissipation of heat.

From the foregoing, it should be apparent that the connector body can be made of a highly elastic material (e.g. shape memory material) that is highly heat conductive (in order to dissipate heat efficiently). The thermal expansion coefficient of the material selected for the connector body should also enable the connector body to expand harmoniously with the thermal expansion of the optical fibers. In other words, the connector body should not thermally expand too much, in which case the grip on the spliced fibers may be loosened, nor should it thermally expand too little, in which case the optical fibers may be overly compressed inside the conduit. It has been found that shape memory alloys are ideal for this connector body as the shape memory alloy exhibits excellent thermal properties (the right coefficient of thermal expansion and the right heat conductivity, while providing super elastic behavior to operate as a glueless connector that can be easily and repeatedly opened and closed to grip (splice) optical fibers.

Examples

The capacity of the optical fiber connector of the present invention to join together two optical fibers while operating at high power levels has been tested and found to work very well. This novel technology minimizes optical losses at the fiber junction. For an illustrative example, two optical fibers of silica SMF-28 (Corning) were joined together. The optical fibers' characteristics are reproduced in the following table:

The SMF-28 optical fibers were cleaved with a high-quality Fitel S325A diamond blade cleaver that provided cleave angles under 1° with an average angle of 0.5°. The splice loss was measured by launching the light of a highly stable 1550 nm laser diode into a fiber segment and measuring the output power with an optical power meter. This measurement was then repeated after adding a spliced fiber segment. Figure 5 shows the power transmitted between the two SMF-28 fibers when increasing launched power. The linearity of the curve demonstrates that losses are stable when the launched power increases. This experiment proves that the device is capable of maintaining the alignment of the two fibers while they are thermally expanding due to the optical losses at the junction point. A bar chart or histogram of the splice loss after a hundred (100) such measurements is presented in Fig. 6. The measurement accuracy was 0.1 dB. The results prove that the alignment between the two optical fibers is very good since no index-matching gel was used nor were the fibers polished before connection.

As another example, and without limiting the application of this technology to other specific alloys or materials, a nickel-titanium shape memory alloy would have a coefficient of thermal conductivity of 18 W/m ^{• 0}C in the austenitic phase and 10 W/m ^{• 0}C in the martensitic phase. Thermal conductivity would be 1 1.0 x 10-6/ ⁰C in the austenitic phase and 6.6 x 10-6/ ⁰C in the martensitic phase. As another example, a Ni-Ti-Nb alloy would have a coefficient of thermal expansion (CTE) of 1 1.4 x 10-6/ ⁰C. Optical fibers such as, for example, the SMF28 by Corning typically range in CTE from about 6 x 10-6/⁰C to about 9 x 10-6/⁰C although these values can vary. Shape memory alloys have been discovered to have thermal expansion coefficients that are believed to be quite well-suited for maintaining alignment of the thermally expanding fibers. Similarly, the thermal conductivity properties of shape memory alloys are excellent in that they effectively dissipate heat generated by optical losses at the splice (connection) formed by the connector. Preferably, the shape memory alloy should have a coefficient of thermal expansion ranging from 6 x 10-6/⁰C to about 12 x 10-6/⁰C. The CTE of the connector body should be matched to the CTE of the fiber to ensure that a solid yet non-damaging grip is maintained on the fibers over the full range of operating temperatures. Fiber Laser Incorporating the Novel Fiber Connector

The novel connector described above may be incorporated into a fiber laser. The fiber laser comprises a light pump (or simply a "pump"), a doped fiber having at least one optical fiber connector as described above, and a laser output from which the generated laser light emerges. In a simple fiber laser, pump light is launched from the pump through a dichroic mirror into the core of the doped fiber. The generated laser light is extracted through another dichroic mirror at the output. In another embodiment, fiber Bragg gratings (FBG) may be spliced between the pump and the doped fiber and between the doped fiber and the output.

As will be appreciated by the skilled person to whom the present specification is addressed, the above description of embodiments is meant to be illustrative and exemplary only. The embodiments and examples presented herein are solely to illustrate the present invention. These specific implementations of the invention may thus be modified, refined, or varied without departing from the present invention as defined by the accompanying claims.

Claims

CLAIMS:

1. An optical fiber connector for splicing ends of optical fibers in a fiber laser, the connector comprising: a fiber conduit dimensioned to splice optical fibers; a connector body having an axial Iy longitudinal slot extending along a main longitudinal axis of the connector body from a first end to a second end and from an outer surface of the connector body radially inwardly to the fiber conduit, the slot and conduit expanding when a wedging force is exerted into the expansion slot, the slot and conduit contracting to grip the optical fibers when the wedging force is removed; and wherein the connector body is made of a highly elastic material that is highly heat conductive.

2. The optical fiber connection device of claim 1 , wherein said connector body thermally expands to maintain precise alignment of the optical fibers.

3. The optical fiber connector device of claim 2, wherein said optical fiber connector maintains the alignment over a distance of at least 1 mm.

4. The optical fiber connector as claimed in any one of claims 1 to 3 wherein said optical fibers have a same thermal expansion coefficient.

5. The optical fiber connector as claimed in any one of claims 1 to 3 wherein said optical fibers have different thermal expansion coefficients.

6. The optical fiber connection device of any one of claims 1 to 5 wherein said connector body is made of a shape memory alloy.

7. A fiber laser comprising: a pump for pumping light; a doped optical fiber connected to the pump, the pump launching light into the doped optical fiber; an outlet connected downstream to the doped optical fiber, the outlet extracting laser light; and at least one optical fiber connector dimensioned to splice optical fibers, the connector comprising a connector body having an axially longitudinal slot extending along a main longitudinal axis of the connector body from a first end to a second end and from an outer surface of the connector body radially inwardly to the fiber conduit, the slot and conduit expanding when a force is exerted into the expansion slot, the slot and conduit contracting to grip the optical fibers when the force is removed; and wherein the connector body is made of a highly elastic and heat conductive material for splicing the fibers and dissipating heat generated by optical losses at a splice of the optical fibers.

8. The fiber laser as claimed in claim 7 wherein the force is a wedging force acting on the expansion slot.

9. The fiber laser as claimed in claim 7 wherein the connector body is made of a shape memory alloy.

10. A method of splicing optical fibers in a fiber laser, the method comprising: providing an optical fiber connector having a connector body made of a highly elastic and heat conductive material, the connector body having a first end and a second end and a longitudinally extending fiber conduit extending from the first end to the second end, the connector body having an expansion slot extending longitudinally from the first end to the second end and from an outer surface of the connector body radially inwardly to the fiber conduit; exerting a force on the connector body of the optical fiber connector to expand the expansion slot and fiber conduit; inserting two optical fibers in the fiber conduit; and releasing the force to cause the slot and conduit to contract to thus splice the optical fibers as part of the fiber laser.

1 1. The method as claimed in claim 10 wherein the force is a wedging force exerted into the expansion slot.