Note: Descriptions are shown in the official language in which they were submitted.
2077856
OPTICAL CONNECTOR
BACKGROUND OF THE INVENTION
(Field of the Invention)
The present invention relates to an optical connector
in which optical fibers are positioned and fixed and optical
connection is realized by using guide pins in optical
communication, and particularly to an optical connector in
which connection guide pins and optical fibers are positioned
and fixed by V-grooves provided in the optical connector.
(Prior Art)
Fig. 1 shows an end surface view of a conventional
optical connector for multiple coated optical fibers, in which
a substrate with ~~-grooves is subjected to insert-molding so as
to be integrated with a molding resin portion.
A substrate 1 is prepared so as to provide optical
fiber guide grooves 3 and two guide pin grooves 4 arranged on
opposite sides of a group of the optical fiber guide grooves 3
on an upper surface thereof. An upper plate 2 is bonded over
the optical fiber guide grooves 3 of the substrate 1 in such a
manner that upper surfaces of the guide pin grooves 4 are left
to be entirely opened. By use of a metal mold, molding guide
pins are subjectE~d to insert-molding within the guide pin
grooves 4 so that a resin molding portion 9 is formed to cover
the substrate 1 and the upper plate 2.
- 1 -
~~'~'~856
At the time of coupling, the optical fibers are
positioned and held in the optical fiber guide grooves 3, the
end surfaces of 'the optical fibers are polished, and then the
guide pins 7 are inserted into two guide pin holes 6 formed
through molding respectively so that the optical fibers are
positioned and coupled with each other. The coupling loss was
about 0.25 dB in average in single-mode optical fibers.
In the conventional optical connector shown in Fig. 1,
the guide pins 7 inserted into the guide pin holes 6
respectively are pressed by the molding resin portion 9 into
the guide pin grooves 4 of the substrate 1, so that
highly-accurate centering can be realized. However, there has
been a problem that the guide pin holes 6 may be transformed as
shown by dotted lines 6' by generation of shrinkage distortion
of the molding resin after insert molding, so that the
V-contact operation force of the guide pins 7 can not be
sufficiently generated to make it difficult to realize optical
connector coupling having a low loss not higher than 0.1 dB in
single-mode optical fibers.
Fig. 2 is a perspective view of another conventional
optical connector for collectively connecting a plurality of
coated optical i:ibers by using guide pins. An optical
connector 50 is formed of epoxy resin through molding and has
such a structure that optical fiber holes 5 are arranged in one
row in the inside of the optical connector 50 and guide pin
holes 6 to which guide pins 7 be inserted are formed on the
- 2 -
207'856
opposite sides oi: the row of optical fiber holes 5. Reference
numeral 12 designates an opening portion from which a person
can view the condition where the optical fibers are being
inserted into t:he optical fiber guide grooves during the
manufacture. Optical fibers are positioned and fixed in the
optical fiber holes 5 and guide pins 7 made of stainless steel
are inserted into the guide pin holes 6, so that optical
connectors 50 in opposition to each other are positioned and
fixed while being guided by the guide pins 7 to thereby realize
an optical coupling.
Such an optical connector 50 employs a method in which
optical fiber cone pins for forming optical fiber holes 5 and
guide pin core pins for forming guide pin holes 6 are
positioned with high accuracy in a metal mold, resin is poured
in the metal mold. to perform molding, and then the respective
core pins are drawn out after molding.
However, the outer diameter of each of the optical
fiber core pins is very small to be about 0.130 mm~, and it
becomes difficult to perform molding with high accuracy because
the optical fiber guide pins 7 are apt to be bent as the number
of the optical fibers becomes larger in producing a connector
for multiple coated optical fibers. Further, resin moldings
have swelling characteristic against heat and humidity so that
the pitch and di<3meter of the holes are apt to be changed,
resulting in a problem in attaining a connection loss of about
0.1 dB in average.
- 3 -
20 7 78 5 6
SUMMARY OF THE INVENTION
The present invention has been attained so as to
solve the problems described above, and an object of the
invention is to provide an optical connector provided with a
silicon V-groove connection member, which is highly accurate
to attain an average contact loss of about 0.1 dB.
The object of the invention has been achieved by
provision of an optical connector in which on a guide-groove
substrate having grooves for positioning optical fibers and
guide pins, there is provided an upper plate having groove
portions for covering the guide pins positioned in said guide
grooves respectivE>ly, and in that an elastic guide-pin
pressing member is provided in each of said guide pin grooves
of said guide-groove substrate above a portion where the
guide pin groove i:> in contact with the guide pin.
In one aspect, the present invention provides for
an optical connector for connecting optical fibers,
comprising: a gui~~e pin; a guide-groove substrate having
guide grooves for positioning said optical fibers and said
guide pin, said guide pin contacting a predetermined location
on one of said guide grooves by which said guide pin is
positioned; an upper plate having a groove portion for
covering said guide pin positioned in said one of said guide
grooves when said upper plate is coupled to said guide-groove
substrate; and an elastic guide-pin pressing member provided
in said groove portion at a position above said location
where said one of raid guide pin grooves contacts said guide
pin.
- 4 -
=y!
2077856
In a furi~her aspect, the present invention provides
for an optical connector for coupling optical fibers,
comprising: a connection member made of silicon and having V-
grooves by which guide pins and optical fibers are positioned
and fixed; and an oxide film formed on said V-grooves of said
connection member at least in the vicinity of contact points
between said guide pins and said V-grooves.
Also, the optical connector of the invention is
characterized in that the V-grooves are oxidized at least in
the vicinity of contact points between the guide pins and the
V-grooves to provide an oxide films. Preferably, the
thickness of the oxide films is 0.01 to 2.0 Vim.
In anothE~r aspect, the present invention provides
an optical connector for performing an optical coupling,
comprising: a guide member having optical fiber guide grooves
for positioning optical fibers and having top and bottom
guide surfaces; a resin molding portion for surrounding said
guide member having opposite opened portions at top and
bottom molding surfaces thereof so as to expose said top and
bottom guide surfaces, respecaively.
Further, the optical connector of the invention is
characterized in treat the resin molding portion of the back
surface of the V-groove guide member is opened at its part
corresponding to an opening portion formed in an upper
surface of the V-groove guide member so that the V-groove
guide member is Exposed at a part of a bottom surface
thereof.
- 4a -
BR:CEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a front view of an end surface of a
conventional multiple-coated-optical-fiber connector in which
a guide-groove substrate is subjected to insert-molding so as
to be integrated with a molding resin portion;
Fig. 2 is a perspective view of a conventional
multiple-coated-optical-fiber connector for collectively
connecting a plurality of optical fibers by using guide pins;
Fig. 3 is a front view of an end surface of an optical
connector according to one embodiment of the present invention;
Fig. 4 is a front view of an end surface of an optical
connector according to another embodiment of the present
invention;
Fig. 5(a) is a perspective view showing a state in
which opening portions are formed in an upper surface of an
upper plate provided on a guide-groove substrate, and Fig . 5 ( b )
is a cross sectional view taken along a line V-V in Fig. 5(a);
Figs. 6(a) through 6(c) are explanatory views showing
a section of a main portion in a method of forming a elastic
guide-pin pressing member by use of the opening portion in Fig.
5;
Fig. 7 i:, an end view of a silicon V-groove guide
substrate in the optical connector according to a still further
embodiment of the present invention; and
- 5 -
2 0'~'~ 8 5
Fig. 8 is an explanatory top view of an example of test
of the optical connector in the state where a guide pin is
inserted according to the present invention;
Figs . 9 ( a ) and 9 ( b ) are views f or explaining an optical
connector according to an embodiment of the present
invention, in wh:Lch Fig. 9(a) is a perspective view of the
whole of the optical connector whereas Fig. 9(b) is a back
surface view of the Fig. 9(a); and
Figs. 10(a) and 10(b) are cross sections of a metal
mold at the time of resin-molding the optical connector of
Figs. 7(a) and 7(~b).
DETAILED DE;3CRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 3 is a front view of an end surface of an optical
connector according to an embodiment of the present invention.
As shown in the figure, a guide-groove substrate 1 made of a
hard and brittle material such as silicon, ceramic, or the like
is subjected to g:riding so as to form, in its upper surface,
optical fiber guide grooves 3 and guide pin grooves 4. An
upper plate 2 made of a material similar to that of the
guide-groove substrate 1 is bonded on the guide-groove
substrate 1 through a thin-film adhesive-agent layer or Si-Si
direct bonding. Groove portions 15 for covering guide pins 7
positioned in the guide pin grooves 4 of the guide-groove
substrate 1 are formed in the upper plate 2. In each of the
groove portions 15, an elastic guide-pin pressing member 16 is
- 6 -
20'~'~8~6
provided only at .3 portion of the groove portion 15 upper than
the center axis of the guide pin 7. Further, a molding resin
portion 9 of epoxy resin or the like is provided through
integral molding to cover the respective outer circumferences
of the guide-groove substrate 1 and the upper plate 2 bonded
with each other.
In this ~=mbodiment, for example, if ael, which is
defined by a shortest distance between the periphery of the
guide pin 7 and t:he surface of the groove portion 15 in the
figure, is selected to be not more than 10 Vim, the molding
resin does not come to flow into each groove portion 15 of the
upper plate 2 so that the elastic guide-pin pressing member 16
is formed only on the portion upper than the center axis of the
guide pin 7.
Fig. 4 is a front view of an end surface of an optical
connector according to another embodiment of the present
invention. In this embodiment, basically, the configurations
of the upper plate 2 and the groove portion 15 are similar to
those in Fig. 3 in. that elastic guide-pin pressing members 16
are provided above contact points A between guide pins 7 and
guide pin grooves ~~, respectively. In this case, if ~e2, which
is defined by the shortest distance between the periphery of
the guide pin 7 and the surface of the groove portion 15 in
Fig. 4, is selected to be not less than 30 um, resin flows in
to reach the contact points A.
20'x'785
In the embodiment of Fig. 3, downward pressing
operation force is most easily generated against the guide pins
7. Even in the embodiment of Fig. 4, however, the resin is
provided in the groove portion 15 only above the respective
contact points A between the guide pins 7 and the guide pin
grooves 4, so treat the quantity of the resin covering the
circumference of the guide pins 7 is less than that of the
conventional example, and further, two guide pin holes are
separated from each other by the upper plate 2 so that the
shrinkage distortion of the resin at the time of molding can be
remarkably reduced.
In Figs. 5(a) and 5(b), opening portions 18
respectively communicating with groove portions 15 are formed
in the upper surface of an upper plate 2 positioned on a
guide-groove substrate 1. When the opening portions 18 are
thus provided, re;~in may be poured into the groove portions 15
through the opening portions 18 to provide elastic guide-pin
pressing members 16, or after elastic guide-pin pressing
members 16 are inserted into the groove portions 15, molding
may be made.
Figs. 6(a) is an explanatory views showing a cross
section of an optical connector in a method of forming the
elastic guide-pin pressing member 16 by use of the opening
portions 18. Figs" 6(b) and 6(c) are explanatory views showing
cross sections of a main portion of an optical connector
according to a modified example of Fig. 6(a).
_ g _
20'7'785
Figs. 6(a) and 6(b) show examples in which molding
resin is poured through the opening portions 18 into the groove
portions 15 of th.e upper plate 2 at the time of forming the
outer-circumferen~tial molding resin portion 9, and the molding
resin is used as it is so as to form the elastic guide-pin
pressing members 7.6. In this case, no particular shape of the
groove portion 15 is required so long as ~e4 shown in Fig.
6(b), which is defined by the shortest distance between the
periphery of the guide pin 7 and the inner surface of the
groove portion 15,, is selected to be not more than 10 um. In
Fig. 6(b), the groove portion 15 has a cross section of a
semicircle whereas that in Fig. 6(a) has V-shaped cross
section.
Fig. 6(c) shows an example in which a guide-groove
substrate 1 and an upper plate 2 are subjected to
insert-molding under the condition where elastic guide-pin
pressing members 16 are inserted into the groove portion 15 at
the time of forming an outer-circumferential molding resin
portion 9. In this case, even if DeS, which is defined by the
shortest distance between the periphery of the guide pin 7 and
the surface of the elastic guide-pin pressing member 16, is not
less than 30 um, tile molding resin does not come to flow down.
Further, the insert pressing members 16 can give downward
operation force against guide pins 7 by the molding pressure of
the molding resin even in the time of molding.
_ g _
207~~~6
The coup:Ling loss test of the optical connector thus
organized, which has been conducted by the inventors, will be
described.
Single-crystal silicon was used for a guide-groove
substrate 1 and subjected to grinding so as to form optical
fiber guide grooves 3 and guide pin grooves 4. An upper plate
2 made of the Name material as that of the guide-groove
substrate 1 and ;having groove portions 15 was bonded on the
guide-groove substrate 1. The diameter of each guide pin 7 was
selected to be 0.6985 mm~. In this structure, gel was set to
be 5 - 10 um, and transfer molding was carried out with epoxy
resin containing silica to thereby produce a single mode
optical fiber connector 50 having the structure shown in Fig.
3 for 32 coated optical fibers. The V-groove working was
carried out with eccentricity within ~ 0.5 um.
As a resu7_t of estimation on the thus obtained optical
connector, the coupling loss attained 0.08 dB in average and
0.56 dB (n=20) at maximum. In order to confirm the pressing
force operation oj_ the elastic guide-pin pressing member 100,
estimation was made on the coupling losses with respect to
guide pins in a range of from 0.6980 mm~ to 0.6990 mm~. The
coupling loss was within 0.1 dB in average in any case.
Further, it was confirmed that there was no problem in
practical use when the guide pin insertion force was in a range
of from 50 to 250 g.
- 10 -
2~7'~ 856
Further, in order to confirm reliability of the optical
connector 50, the optical connector 50 was subjected to a heat
cycle of from -40 to +70 C° and a wet heat test at 80 C° and 95
$ humidity. As a :result, it was confirmed that loss scattering
was within 0.03 d~3 which was not a problem.
In the embodiments described above, because the guide
pin 7 is directly brought into contact with the surface of the
guide pin groove 4 formed in the substrate 1, it is preferable
to improve friction-resistance between the guide pin 7 and
guide pin groove 4 , as shown in a further embodiment of Fig . 7 .
Fig. 7 illustrates an end view of a V-groove guide
substrate in an optical connector according to another
embodiment of the present invention. In the drawing, reference
numeral 1 designates a V-groove guide substrate of silicon
having optical filer V-grooves 3 and guide pin V-grooves 4
formed in its upper. surface. An oxide film 34 is formed on the
surfaces of the optical fiber grooves 3 and the guide pin
grooves 4.
The V-groove guide substrate 1 is made of silicon and
the optical fiber grooves 3 and the guide pin grooves 4 are
formed thereon, for example, by cutting or the like. Then, the
silicon in the surd=ace of the optical fiber grooves 3 and the
guide pin grooves ~E is oxidized by a diffusion method to form
the oxide film 34. Although the drawing shows a case where the
oxide film 34 is formed over the whole surface of the V-groove
guide substrate 1, 'the oxide film 34 is formed on the guide pin
- 11 -
20'~'~8~6
V-grooves 4 with a width of 100 um at least in the vicinity of
the contact point. between each guide pin V-groove 4 and the
guide pin. It is preferable to select the thickness of the
oxide film 34 to be in a range of 0.01 to 2.0 ~m because micro
cracks can not beg reduced if the film thickness is too thin
while the strengl:h is weakened if it is too thick on the
contrary. As the :material for the guide pins, it is preferable
to use zirconia in order to prevent abrasion.
As stated above, in the optical connector according to
the present invention, an oxide film 34 is formed to cover at
least the surface of the guide pin V-grooves 4 so that micro
cracks in the surf~3ce are reduced and cracks due to abrasion by
the guide pins are also reduced. Accordingly, the starting
points of cracks are reduced to thereby improve the strength
against cracks.
As was described above, it is preferable to select the
thickness of the oxide film 34 to be in a range of 0.01 to 2.0
um because micro cracks can not be reduced and no effect can be
shown if the film i~hickness is too thin while stress acting on
the boundary between the silicon material and the silicon oxide
becomes so strong t:o break the silicon oxide if it is too thick
on the contrary.
By using z:irconia as a material for the guide pins 7,
the abrasion of the guide pins 7 can be made to be almost zero
because the hardnf~ss of zirconia is larger than stainless
steel. Although there is cemented carbide as a material having
- 12 -
2 0'7'7 $ 5 a
a large hardness other than zirconia, abrasion caused when the
guide pins are inserted/drawn out into/from the guide pin
V-grooves 4 is smaller than the case using cemented carbide
because the frictional coefficient with respect to silicon is
smaller in the care using zirconia than the case using cemented
carbide. It is Estimated that a ceramic material having the
same hardness and frictional coefficient as those of zirconia
may be used for the guide pins 7.
The strength test of the optical connector thus
organized which has been conducted by the inventors will be
described.
A V-groove guide substrate 1 having optical fiber
V-grooves 3 and guide pin V-grooves 4 formed in its upper
surface was heate<~ at 1050 C° for 2 to 3 hours in an atmosphere
of oxygen and steam to thereby form an oxide film 34 having a
film thickness of 0.2 to 0.3 um. The thickness of the oxide
film 34 can be controlled by changing the quantity of steam,
the time, and the temperature. By using the V-groove guide
substrate 1 subjected to oxidation treatment, an optical
connector for collectively connecting SM fiber of 16 coated
optical fibers was produced, and the strength and connection
loss stability were estimated.
Fig. 8 illustrates a top view of an optical connector
in the state where a guide pin 7 has been inserted thereinto.
As shown in Fig. Et, the guide pin 7 was inserted by 4 mm into
a guide pin hole, and a force in the direction of arrow was
- 13 -
20'~'~8~6
exerted to the guide pin 9 at a position away by 5 mm from the
end surface of an optical connector 50.
In the strength test, the test was conducted on 30
samples. As a result, it was confirmed that the average
strength was 1 . 36 kg in the case of providing no oxide film 34 ,
while the average strength was 1.79 kg in the case of providing
an oxide film 34, so that the strength was improved by about 30
As a result of test on 30 samples with respect to the
connection loss, it was confirmed that the change in contact
loss due to connection/disconnection of the optical connector
300 times was 0 . ~4 dB at maximum in the case of providing no
oxide film 34 and using a stainless steel guide pin 7, while it
was 0.2 dB at max:Lmum in the case of providing an oxide film 34
and using a zirconia guide pin 7, so that the connection loss
characteristic was improved.
Figs . 9 ( a ) and 9 ( b ) are views for explaining an optical
connector according to a still further embodiment of the
present invention, in which Fig. 9(a) is a perspective view
showing the whole of the optical connector, and Fig. 9(b) is a
view showing the back surface of Fig. 9(a).
In the drawings, reference numeral 100 designates a
V-shape guide member on which optical fiber guide grooves 3 and
guide pin grooves are formed, and which provides an opening
portion 12 at a portion of the upper surface. At the opening
portion 12, the optical fiber guide grooves 3 are exposed
- 14 -
2077856
partly at portions 3a of the optical fiber guide grooves 3.
Reference numeral. 9 designates a resin molding portion formed
through resin-molding on the circumference of the V-groove
guide member 100. The resin molding portion 9 provides opening
portions 24 respe~~tively in its front and back surface portions
corresponding to the upper opening portion 12 so that a V-
groove substrate 1 of the V-groove guide member 100 is partly
exposed.
Figs. 10(a) and 10(b) are cross sections illustrating
manufacturing metal molds for obtaining the optical connector
shown in Figs. 9(a) and 9(b) according to the invention.
In Fig. 10(a), similarly to the conventional example,
a projected portion 22a is provided on a lower metal mold 22 at
a portion corresponding to the opening portion 12 of the
V-groove guide member 100 to thereby form an opening-portion
seal portion. Further, an upper metal mold 21 is also similar
to that of the conventional example. However, a projected
portion 21a is provided on the substrate 1 at a portion
corresponding to t:he opening portion 12 of the V-groove guide
member 100 to ther~'by form a seal portions and after molding no
resin portion exi:~ts at this seal portion so as to form the
opening portion 24 of the resin molding portion 9 at which the
back surface of the substrate 1 is partly exposed.
Thus, the opening portion 24 in which no resin exists
is formed also in vthe back surface of the V-groove substrate 1
corresponding to t:he opening portion 12 so that the molding
- 15 -
2~'~'~~~~
pressures applied on the upper and lower surfaces of the
V-groove guide member 100 are balanced with each other to make
it possible to minimize the transformation of the V-groove
guide member 100.
In Fig. 10(b), although the lower metal mold 22 is
similar to that of the conventional example, a projected
portion 21a is ;provided on the upper metal mold 21 at a
position corresp~~nding to the opening portion 12 of the
V-groove guide member 100 similarly to the lower metal mold 22
to thereby form a seal portion. Accordingly, no molding resin
exists at this seal portion so that the back surface of the
substrate 1 is exposed partly at this portion.
In order to confirm the effects of the present
invention, large-aized optical connectors each of which has a
width of 24 mm and having 80 coated optical fibers were made of
silicon chips and were estimated.
Each sili~~on chip was prepared so as to provide two
guide pin grooves of 1.2 mm~, 80 optical-fiber guide grooves of
0 . 125 mm~, and an opening portion for inserting optical fibers .
Thus, V-groove guide members 100 were formed respectively into
such a molding pressure balance type guide member as shown in
Fig. 10(a) and such a molding pressure unbalance type guide
member providing no opening portion 24, and were subjected to
molding with epoxy resin through transfer molding.
As a result, in the molding pressure balance type, no
curve was generated in the V-groove guide member of the silicon
- 16 -
2U7'~8~~
chip and a multiple-coated-optical-fiber connector having an
eccentricity of 0.5 um could be formed. On the other hand, in
the unbalance tyF>e, a curve was confirmed in the silicon chip
and it was found i~hat the silicon chip became most eccentric at
its center so treat it was bent by 2 um at maximum in the
up/down direction.
As was described above, according to the optical
connector, the guide pins can be surely touched with the guide
pin grooves by means of the elastic guide-pin pressing members,
respectively, so i~hat an optical connector having a low loss of
not more than O.:L dB can be realized in single-mode optical
fibers. By provision of opening portions in the upper plate,
molding resin can be poured through the opening portions so
that the function of the elastic guide-pin pressing members
can be formed, or the insert pressing members can be provided
before resin molding. By making the dimension of De be a
parameter, the quantity of resin to be poured can be controlled
and the upper position of each of the guide pins can be
pressed.
Also, according to the optical connector of the present
invention, by forming an oxide film over at least the surface
of the guide pin V-grooves of the silicon V-groove guide
substrate it is made possible to improve the friction-
resistance of they optical connector, and by coupling such
optical connectors by use of zirconia guide pins the abrasion
of the guide pin V-grooves of the optical connectors can be
- 17 -
2 fl'~'~ 8 ~ ~
reduced, and the connection loss is stabilized to thereby make
it possible to realize an optical connector of low connection
loss of about 0.1 dB in average.
Further, in the optical connector according to the
present invention, an opening portion is provided in the resin
molding portion o:n the back surface of the V-groove guide
portion correspondingly to the opening portion in the upper
surface thereof, so that the molding pressure can be balanced
at the time of molding to thereby make it possible to obtain a
highly-accurate optical connector in which the transformation
of the V-groove guide member is minimized.
- 18 -
