Optical fibre assembly for transmitting high energy laser radiation

An optical fibre assembly (10) for transmitting high energy laser radiation comprises a tubular moulded plastics handle (1) having a tubular metallic termination (2) for engagement with a laser radiation source. The other end of handle (1) is connected by a heat shrunk plastics sleeve (6) to a length of plastics tubing (4) the distal end of which incorporates an end formation (5), and a single plastics coated glass cored optical fibre (3) extends through the interior of termination (2), handle (1), plastics tube (4) and termination (5). The assembly (10) is easy and inexpensive to manufacture because of the simplicity of components and assembly thereof and enables the assembly (10) to be used on a once-and-for-all basis, i.e., assembly (10) is disposable.

This invention relates to an optical fibre assembly for transmitting high 
energy laser radiation. 
High energy laser radiation is being utilised increasingly in medical work, 
being delivered to the site to be irradiated by an optical fibre assembly 
dimensioned externally to fit within an endoscope and being connected to a 
laser radiation source. Low energy laser radiation is also needed in 
medical work, primarily for illumination purposes, but whereas low energy 
radiation may be transmitted by an optical fibre assembly incorporating a 
fibre bundle, high energy laser radiation is required to be transmitted by 
a single fibre, and the coupling of that fibre to the laser radiation 
source is critical if the fibre is to have any usable lifespan. 
Furthermore, in medical work, sterilization of the optical fibre assembly 
is critically important if cross contamination of patients is to be 
avoided. 
It is an object of the present invention to provide an optical fibre 
assembly for transmitting high energy laser radiation, and which is 
sufficiently easy and inexpensive to manufacture as to permit use on a 
once-and-for-all basis, whereby such assemblies may be pre-sterilized. 
According to a first aspect the present invention provides an optical fibre 
assembly for transmitting high energy laser radiation, said assembly 
comprising a tubular moulded plastics handle to which is fitted at one end 
a tubular metallic termination and at the other end a length of plastics 
tubing, the distal end of the tubing incorporating an end formation, a 
single plastics-coated glass-cored optical fibre extending through the 
interior of the termination, the handle, the tubing and the end formation 
and being secured to the termination, the plastics tubing being a sliding 
fit within the bore of the handle and being secured to the handle by a 
heat shrunk plastics sleeve, the fibre being cleaved at each end and 
accurately located with respect to the termination by a crimp secural of 
the termination to the plastics coating of the fibre. 
The end formation may be created by pre-crimping the plastics tubing or it 
may be a separate member capable of centralizing the single fibre in the 
plastics tubing. 
The fibre assembly of the present invention is easy and inexpensive to 
manufacture in that only one component is required to be made of metal 
(e.g. a brass termination), the others being made of plastics such as PTFE 
or polysulphane, and assembly of the components is relatively simple 
because the plastics tubing is a sliding fit within the bore of the 
handle. Thus, during assembly, one end of the fibre is crimp connected to 
the termination whereafter the handle is fed over the length of the fibre 
into engagement with the termination. The length of tubing is then fed 
over the fibre and slid into the bore of the handle. When the end 
formation is a separate member this sliding movement is sufficient to 
expose the distal end of the fibre which is fitted to the end member and 
thereafter the tubing is slid in the reverse direction into engagement 
with the end member. The heat shrinkable plastics sleeve is fitted and 
heat shrunk thereafter to the handle in order to secure the tubing in its 
final position. 
The optical fibre conveniently has a hard silica core and may have a 
plastics cladding over which is a relatively thick plastics coating which 
provides the basis for the crimp secural. One suitable form of fibre is 
manufactured by Ensign Bickford Inc. of 660 Hopmeadow Street, Simsbury, 
Conn., U.S.A. under product reference number HC - 412T. 
Preferably the handle is provided on its outer surface with a flange 
disposed at a predetermined distance from said termination whereby the 
handle is capable of being resiliently urged to seat the termination 
against a mechanical stop associated with a laser radiation source in 
order precisely to locate the cleaved fibre end at the focal point of the 
incoming laser radiation. In this connection it will be understood that in 
order to couple high energy laser radiation from a source into an optical 
fibre assembly it is necessary to pass the collimated laser beam through a 
focussing lens and to locate the fibre end at the focal point such that 
laser radiation is incident only on the core portion of the single fibre. 
In accordance with a second aspect of the invention there is provided 
apparatus for coupling an optical fibre assembly in accordance with the 
first aspect of the present invention to a laser radiation source, said 
apparatus comprising a member defining a socket for receiving the handle 
and termination of said assembly, an abutment collar being fixedly mounted 
in said socket and having an abutment surface located at a predetermined 
distance from a focussing lens mounted on said member, the optical axis of 
said lens being aligned with the longitudinal axis of said socket, said 
member being provided with means for securing the member to the housing of 
a laser radiation source. 
Conveniently an electrical interlock device incorporating a microswitch is 
mounted on said member and is arranged for connection to enable and/or 
disable a said laser radiation source according to the presence or absence 
of a said fibre assembly fitted to said socket with said termination in 
abutment with said abutment surface.

As is shown in FIG. 1 an optical fibre assembly 10 comprises a tubular 
moulded plastics handle 1 to which there is fitted at one end a tubular 
metallic termination 2, this termination 2 being illustrated in greater 
detail in FIG. 2. A length of plastics tubing 4 is fitted to the other end 
of the handle 1, tubing 4 being a sliding fit within the bore 7 of handle 
1, the final location of tubing 4 with respect to handle 1 being preserved 
by a heat shrunk plastics sleeve 6 overlapping part of handle 1 and part 
of tubing 4. At the distal end of tubing 4 there is provided an end member 
5, alternative forms of which are illustrated more clearly in FIGS. 3, 4 
and 5 respectively, and secured to termination 2 and to member 5 and 
extending within tubing 4, handle 1, and member 2 there is a plastics 
coated glass cored optical fibre 3. The fibre 3 is secured to termination 
2 by crimping at location 8, this crimping being such that the thin walled 
portion of termination 2 is deformed into mechanical engagement with the 
plastics coating of fibre 3 but with insufficient deformation to affect 
the optical properties of the fibre. At its other end optical fibre 3 is 
secured to end member 5 in any one of the configurations to be explained 
with reference to FIGS. 3, 4 and 5. Each end of the fibre 3 is free of 
plastics coating for a very short distance and the fibre end faces are 
each cleaved. 
Termination 2 is shown in greater detail in FIG. 2 from which it will be 
seen that the termination is of tubular structure comprising a head 
portion 2A with a principal recess 2B into which the cleaved end of fibre 
3 protrudes, the head portion incorporating a bore 2C for locating the 
fibre 3 concentrically and integral with head portion 2A is a tubular 
shank 2D dimensioned to be an interference fit with the bore 7 of handle 
1, a thin walled shank portion 2E being integral with shank 2D and 
incorporating crimp location 8. 
In order to assemble fibre 3 to termination 2 the plastics coating is 
initially stripped back from the end of the fibre which is thereafter 
fitted into termination 2 until the cleaved end face of the fibre is 
precisely located axially within recess 2B and thereafter a crimp tool 
(not shown) is applied to thin walled portion 2E to crimp termination 2 
onto the plastics coating of fibre 3. Handle 1 is thereafter slid along 
the length of the fibre 3 and forced into engagement with shank 2D which 
conveniently may be provided with tooth-like protrusions to prevent 
disengagement. The required length of tubing 4 is thereafter slid over the 
free end of fibre 3 and caused to slide along bore 7 of handle 1 until 
such time as the free end of fibre 3 protrudes from tubing 4. Thereafter 
end member 5 is secured to the fibre 3 and tubing 4 is slid in the reverse 
direction with respect to handle 1 into engagement with end member 5. 
Finally, a length of heat shrinkable plastic sleeving is slid along the 
exterior of tubing 4 to overlap with part of handle 1 and part of plastics 
tubing 4, heat thereafter being applied in order to shrink sleeve 6 into 
place. 
As is shown in FIG. 3 one form of end member 15 comprises a head portion 
15A with a recess 15B into which the cleaved end of fibre 3 is located, 
head portion 15A being integral with a relatively thin walled shank 
portion 15C which at location 16 is deformed by crimping so as to engage 
with the plastics coating of fibre 3, the outer surface of head portion 
l5A being provided with teeth 15D which engage with the plastics tubing 4 
in order to secure tubing 4 in position. 
As is shown in FIG. 4 another form of end member 25 comprises a head 
portion 25A having a recess 25B for receiving the cleaved end of the fibre 
3 and a shank portion 25C terminating in inwardly extending teeth 25D 
which are arranged to grip the plastics coating of fibre 3 in 
screw-thread-like manner. The outer surface of head portion 25A is 
provided with teeth 25E for engagement with plastics tubing 4. 
As shown in FIG. 5 a still further form of end member 35 is in the form of 
a helical spring externally dimensioned to fit within and grip plastics 
tubing 4 and internally dimensioned to receive and grip the plastics 
coating of fibre 3. In this case tubing 4 is axially extended beyond end 
member 35 in order to provide a recess 35A for the cleaved end of fibre 3. 
FIG. 6 illustrates a modified form of the distal end retention arrangement 
for the fibre 3 in which the plastics tubing 4 is pre-crimped radially 
with four indentations 38 leaving an axially disposed gap sufficient to 
centrally locate the end of fibre 3 without gripping the fibre. With this 
arrangement retention of the tubing 4 is effected solely at the handle 1 
by means of the heat shrink sleeve 6 and tubing 4 is axially extended 
beyond end formation 38 to provide a recess 39 for the cleaved end of 
fibre 3. The exact axial length of recess 39 is relatively unimportant and 
may be sufficiently oversize to provide protection against damage during 
transit of the assembly 10 in which case it is preferred that the user cut 
off the unwanted length of tubing 4 prior to use of the assembly 10, this 
being easy to effect because tubing 4 is made of plastics. Furthermore, 
with the FIG. 6 arrangement during assembly of the components it will be 
appreciated that there is no requirement to reverse slide the tubing 4 
since there is no separate end member per se and, of course, there is no 
danger of the end member becoming disengaged and lost during use of the 
assembly 10 if the end member is absent. 
As is shown in FIG. 7 assembly 10 is arranged to be fitted to a laser 
source (not shown) by way of an assembly 40 comprising a socket member 41 
into which the nose portion of handle 1 is a sliding fit. Within the 
socket of member 41 there is provided an end stop 42 having an abutment 
surface 42A against which termination 2 is resiliently urged by means of 
spring loaded detent 43 mounted in member 41 and engaging a radially 
extending shoulder 43A on handle 1. The end stop 42 is itself axially 
apertured and surface 42A is factory set at a critical distance from a 
focussing lens 44 which is held by mounts 45 such that its optical axis is 
precisely aligned with the longitudinal axis of the socket formed within 
member 41. 
Member 41 is provided with a termination flange 41A incorporating X,Y, 
adjustment means 41B whereby the flange is capable of being secured to the 
housing of a laser radiation source (not shown) so that the optical axis 
of lens 44 is precisely aligned with the received radiation axis. 
An electrical interlock device 46 is fitted to member 41 and incorporates a 
microswitch 46A which is actuated by the termination 2 and interlock 
device 46 is arranged, in use, to enable the laser source when assembly 10 
is fitted to member 41 and to disable the laser radiation source when 
assembly 10 is not so fitted. 
It will be appreciated that in a medical environment the site to which 
radiation is to be delivered incorporates a variety of liquids which in 
relation to the optical fibre 3 are contaminants and in order to keep the 
cleaved fibre end face free of such contaminants it is desirable to 
surround the fibre end face with one or more jets of inert gas. To provide 
such gas jetting, handle 1 is provided with aperture 50 which, when the 
handle is fitted to member 41, is aligned with an annular channel 51 to 
which fitting 52 provides gas from a supply (not shown). Axial flow of gas 
within member 41 is prevented by O-ring seals 53, 54, and gas entering 
handle 1 flows along the annular channel formed between the fibre 3 and 
the interior of tubing 4 and emerges from the end of assembly 10 via end 
member 5. For this purpose the end member 15 (FIG. 3) is provided with a 
cut-out portion 15E; the end member 25 (FIG. 4) is provided with a cut-out 
portion 25F; and the end member 35 (FIG. 5) is provided with separated 
coils so that a helical passageway 35B is provided. In the FIG. 6 case the 
circumferential regions between the four indentations 38 provide through 
passageways for gas flow. 
The assembly 10 which has been described is sufficiently cheap and easy to 
manufacture to be used on a once-and-for-all basis and is easily coiled 
and packaged and sterilized, such as by ethylene oxide sterilization.