Rinsing bath

A device for cleaning ends of optical fibers comprises a vessel intended to contain a rinsing fluid, in which the ends are to be inserted. A holder assembly is attached to the vessel and has a central element comprising a through-hole adapted to receive a fiber holder. The central element can be moved vertically in order to position the fiber holder at a predetermined distance from the surface of the rinsing fluid, so that only a predefined portion of an end portion of an optical fiber held by the fiber holder is emerged in the rinsing fluid. For a correct distance this will protect the primary coating of the optical fiber from being wet by the fluid. A light guide is mounted in the central element. Its lower end projects through a predetermined distance from the bottom surface of the central element. The upper end surface of the light guide has a lens shape and can be viewed by an operator, so that when moving the central element by turning an adjustment ring the change of coloring of the upper surface of the light guide will indicate a contact between the lower end and the liquid surface. A piezoelectrical vibrator is connected to the vessel for conveying ultrasonic vibrations thereto and transmits vibrations having a scanning frequency, the variation of frequency eliminating the risk of forming stationary nodes in the liquid where no cleaning effect is achieved.

The present invention relates to a rinsing bath for optical fibers, in 
particular for optical ribbon fibers. 
BACKGROUND 
Optical fibers are presently widely used for communicating information. In 
the physical installation of optical fibers in e.g. networks such as in 
large telecommunication systems, in computers, LANs, optical fibers have 
to spliced to each other and connected to various physical device such as 
lasers, light detectors, couplers, etc. Also in maintenance of existing 
optical fiber installations there is a need for repairing optical fibers, 
this also requiring that optical fibers are spliced to each other. Optical 
fibers composed to ribbon fibers are more and more used since ribbon 
fibers hold a plurality of optical fibers and are more easily handled than 
individual fibers. When making splices or connections to devices the 
primary protection coating of the optical fibers has to be removed in 
order to expose the bare optical fiber, this operation being called to 
strip the optical fibers. The primary protection coating is commonly made 
of an artificial resin such as acrylic plastics. The stripping operation 
mostly leaves some dust or particles on the bare portion of the optical 
fibers and this dust must be removed. Finally the optical fibers are cut 
off a right angles and then the splicing or connection operation is 
performed. In the cutting and splicing operations the bare fiber ends are 
positioned very accurately in relation to another fibers or an input or 
output surface area of a device. For this positioning often some kind of 
positioning planes or surfaces are used, such as V-grooves. For such 
positioning to be accurate the bare fiber ends should be extremely clean, 
since also a very small dust particle can jeopardize the required 
accuracy. 
Dust and particles can adhere rather strongly to stripped, bare fiber ends 
and it may be difficult to have them completely removed. The removal of 
dust and particles of stripped fiber ends has often, in a simple way, been 
executed by moistening a cloth with some alcohol and then wiping the ends. 
However, such a wiping procedure is not quite satisfactory since the cloth 
can itself leave some particles. In addition, in some applications, e.g. 
High Strength Splicing, the bare fibers should not touched by any rough 
objects or materials. 
SUMMARY 
It is an object of the invention to provide a device for cleaning optical 
fibers which can easily be handled and used in the field and has an 
efficient rinsing or cleaning action. 
It is another object of the invention to provide a device for cleaning 
optical fibers in which the risk of wetting the primary protective coating 
of the fibers is minimized. 
The problem solved by the invention is thus how to construct an efficient 
device for cleaning optical fibers so that the device can easily be 
handled and used in the field and so that the risk of wetting the primary 
protective coating is low and the rinsing effect still is maintained at a 
high level. 
Thus, a device for cleaning ends of optical fibers comprises a vessel 
intended to contain a suitable rinsing liquid and having a transport lid, 
protecting the interior of the vessel and a rinsing liquid contained 
therein. A holder assembly is attached to the vessel and has an adjustment 
unit. The adjustment unit comprises a central element and adjustment ring 
which are rotatably attached to each other. The adjustment ring cooperates 
with a holder unit comprising holder ring attached to the vessel and a 
base ring having a thread engaging a thread of the adjustment ring. The 
central element has a through-hole adapted to receive a fiber holder. The 
adjustment unit and thus the central element can be moved vertically by 
turning the adjustment nut. Thereby the fiber holder can be positioned at 
a predetermined distance of the surface of the rinsing fluid, so that only 
a predefined portion of an end portion of an optical fiber held by the 
fiber holder is immersed in the rinsing liquid. For a correct distance 
this will protect the primary coating of the optical fiber from being wet 
by the liquid. The exact positioning is carried out using a light guide 
mounted in the central element. The light guide has a lower end projecting 
through a predetermined distance from the bottom surface of the central 
element. The upper end of the light guide has a polished flat end surface 
and can be viewed by an operator, so that when moving the central element 
by turning the adjustment ring the change of coloring of the upper surface 
of the light guide will indicate a contact between the lower end and the 
liquid surface. 
A piezoelectrical element or vibrator is connected to the vessel for 
conveying ultrasonic vibrations thereto. It transmits vibrations having a 
varying frequency, the variation of frequency eliminating the risk of 
forming stationary nodes in the liquid where no cleaning effect is 
achieved. An indicator is provided signalling that the cleaning operation 
is finished and that the fiber holder together with fibers held thereby 
can be extracted from the hole in the adjustment unit when the vibrations 
are still excited and the cleaning action still is active, this preventing 
recontaminating the fibers. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the methods, processes, instrumentalities and combinations particularly 
pointed out in the appended claims.

DETAILED DESCRIPTION 
In FIG. 1 an exploded view of an ultrasonic rinsing bath for optical fibers 
is shown. It comprises a rinsing vessel 1, a holder assembly 3, a 
protective transport lid 5, a piezoelectric element 7, an electronic 
circuit board 9, an upper plate 11, a house 13 and a bottom plate 15. The 
rinsing vessel 1 is attached to the holder assembly 3 at its upper edge, 
see also the sectional view of FIG. 2. The holder assembly is mounted in a 
through-hole in the upper plate 11 and projects into the interior of the 
house 13, in which also the vessel 1 is located. The piezoelectric element 
7 has the shape as a low circular cylinder and is mounted to the bottom of 
the vessel 1. The house 13 is open at its top and bottom side and is there 
closed by the upper plate 11 and the bottom plate 15 respectively. The 
transport lid 5 is detachably mounted at the top surface of the holder 
assembly 3 and is used only when the bath assembly is transported and the 
vessel contains a liquid. 
The details of the vessel 1 and the holder assembly 3 appear from the 
sectional view of FIG. 2. The vessel 1 has a basically circular 
cylindrical shape. Its upper marginal portion is bent outwards to form a 
flange 21. The flange 21 is retained between two components of the holder 
assembly 3, a base ring 23 attached to the upper plate 11 and a holder 
ring 25. A central element 27 is mounted to slide in the holder ring 25 
and is at its upper side rotatably attached to an adjustment ring 29. The 
adjustment ring 29 is attached to the holder ring 25 through a thread. A 
locking nut 31 is connected to the holder ring 25 through the same thread. 
The adjustment ring 29 will when rotated be displaced upwards or downwards 
owing to the threaded connection to the holder ring 25, the direction 
being dependent on the rotation direction. The central element 27 will 
accompany the movement upwards or downwards of the adjustment ring 29 but 
will not be rotated. 
In the center of the central element 27 a through-hole 33 is provided which 
is adapted to receive and firmly hold a fiber holder 35, see FIG. 3. The 
fiber holder 35 has generally the shape of a low rectangular box 
comprising two openable lids 37 which when closed firmly hold a ribbon 
fiber 39. The through-hole 33 is somewhat tapering in its upper portions, 
this simplifying the insertion of the fiber holder 35. The fiber holder 
will when fully inserted with its lower end surface abut a projection 41 
projecting from the walls of the through-hole 33 towards the center of the 
hole. The projection still leaves room for the fiber ribbon 39 to pass 
downwards from the fiber holder 35 into the vessel 1. 
In the central element 27 also a light guide 43 is mounted in a hole 
extending in parallel to the through-hole 33 but displaced from the center 
position. The light guide 43 can be glass or plastics rod. Its lower end, 
which is a flat surface perpendicular to the light guide axis, projects an 
accurately defined distance from the bottom surface of the central element 
27. The upper end can have a flat polished surface allowing the colour 
thereof to be viewed. 
The operation of the ultrasonic rinsing device will now be described. An 
optical ribbon fiber 39 for example comprising four parallel fibers is 
mounted in the fiber holder 35, the free end portion of the fiber ribbon 
extending 35-45 mm from the end surface of the fiber holder. This free end 
portion is stripped of its polyacrylic protective coating so that a 
definite, accurately determined small length of e.g. 3 mm of the coating 
is left immediately at the fiber holder 35, the rest of the free end 
portion comprising the bare fibers. 
The protection lid 5 of the rinsing device is removed, rinsing fluid such 
as suitable alcohol like ethanol or propanol is filled into the vessel 1 
up to some level mark, not shown, made inside in the vessel 1. The level 
mark is located to give a suitable level of the upper surface of the 
cleaning liquid, so that e.g. the level is always somewhat below the 
bottom surface of the central element 27. In this operation all of the 
holder assembly 3 may be removed by having turned the holder ring 25 in a 
suitable direction. 
The vertical position of the central element is then adjusted. Then first 
the adjustment ring 29 is turned in a suitable direction to move it to the 
highest possible position, generally in an anti-clockwise direction. The 
locking nut 31 is then moved to its lowest position by turning it, 
generally in a clockwise direction, as seen from the top. The holder 
assembly 3 is mounted to the base ring 23 by making the threads engage and 
turning in a suitable direction if the assembly has been previously 
removed. The upper surface of the light guide 43 is observed while turning 
the adjustment ring 29 to make it move downwards, generally in a clockwise 
direction as seen from above. The turning of the ring is stopped exactly 
at the moment when the coloring of the lens-shaped top surface of the 
light guide 43 becomes darker, this fact signalling a contact of the lower 
end of the light guide with the surface of the liquid in the vessel 1. 
Finally the locking nut is turned to move it upwards, generally in an 
anti-clockwise direction, until is engages the bottom surface of the 
adjustment ring 29 and locks it in its current position. 
The fiber holder 35 and its firmly retained ribbon fiber 39 are then 
inserted in the central hole 33 in the central element 27 as far as 
possible downwards until the lower end surface of the fiber holder 25 
engages the projection 41. The cleaning process is started by pressing a 
"Start/Stop" button 45 on the top plate 11. A light emitting diode 47, 
also positioned on the top plate 11, is then made to issue visible light 
to indicate the start of the cleaning process. The piezoelectrical element 
7 is at the same time energized to make it vibrate and thereby transmit 
the generated ultrasonic vibrations to the vessel 1 and to the liquid in 
the vessel thereby cleaning the immersed optical fibers. However, then the 
vibrations generated in the liquid may be apt to form a standing-wave 
pattern in the liquid, such a pattern having fixed nodes in which the 
liquid practically does not move and thus does not have any cleaning or 
rinsing action. In order to alleviate this phenomenon the frequency of the 
ultrasonic vibrations is varied, as controlled by the electronic circuits 
on the circuit board 9, by continuously changing the energizing of the 
piezoelectrical element 7. Typically the frequency can be varied between 
two definite frequencies, say 50 and 56 kHz, the variation having a time 
period of 1-4 seconds, preferably 1-2 seconds, for changing from the 
lowest to the highest frequency of the generated vibrations. After some 
definite time period such as 10 seconds the cleaning action is sufficient 
and the fiber holder can be removed. This is indicated in some suitable 
way, for instance by starting an audible alarm, not shown, or by changing 
the state of the light issued by the light emitting diode 47, for instance 
by changing a steady light to a blinking issued light. The fiber holder is 
then removed and the generation of the ultrasonic vibrations automatically 
stops after some suitable further time period such as 10 seconds. In that 
way the fibers are extracted from the liquid bath when the vibrations 
therein are still generated, this reducing the risk of having particles 
suspended in the liquid attach to the fibers and thus accompanying them in 
the operation of lifting the fiber holder up from the holder assembly. The 
fiber holder 35 is as quickly as possible mounted in some device, not 
shown, for example cutting the held fibers to some definite standard free 
length, such as a length of 13 mm, to be then used in a splicing 
apparatus, not shown, for connection to other fibers or for connection to 
other devices. 
While specific embodiments of the invention have been illustrated and 
described herein, it is realized that numerous additional advantages, 
modifications and changes will readily occur to those skilled in the art. 
Therefore, the invention in its broader aspects is not limited to the 
specific details, representative devices and illustrated examples shown 
and described herein. Accordingly, various modifications may be made 
without departing from the spirit or scope of the general inventive 
concept as defined by the appended claims and their equivalents. It is 
therefore to be understood that the appended claims are intended to cover 
all such modifications and changes as fall within a true spirit and scope 
of the invention.