Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1999-12-08
2002-09-03
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S089000
Reexamination Certificate
active
06443630
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
This invention relates to an optical connector used with a multiplex transmission circuit of a vehicle, such as an automobile, a sleeve placed in a receptacle forming a part of the optical connector, and a manufacturing method for the sleeve.
2. Related Art
As this type of optical connector and sleeve, an optical connector previously proposed by the applicant (art disclosed in JP-B-6-33443UM) is generally known.
The optical connector and sleeve disclosed in the gazette will be discussed with reference to
FIGS. 9
to
11
.
First, in
FIG. 9
, reference numeral
1
denotes an optical connector and the optical connector
1
comprises a receptacle
2
as a machine side connector and an optical plug
3
as an optical fiber side connector.
As shown in
FIGS. 9 and 10
, the receptacle
2
has a housing
4
made of a synthetic resin and storage chambers
5
and
5
in the housing
4
stores reception and transmission modules
6
and
6
′ in a state in which they are supported on back sheets
7
and
7
each made of an elastic member such as rubber. On the rear face, a cap
8
is placed, and reception tubes
10
and
10
extended forward matching the axes of lenses
9
and
9
are placed ahead of the storage chambers
5
and
5
in which the reception and transmission modules
6
and
6
′ are supported. Sleeves
13
and
13
each comprising a light transmission member
11
consisting of a core and a clad (not shown) (for example, a multimode plastic optical fiber of about Ø1) bonded and fixed to a holder
12
like a metal cylinder and ground on both end faces are inserted into the reception tubes
10
and
10
.
The optical fiber
3
is fitted and connected to the receptacle
2
and as shown in
FIGS. 9 and 11
, comprises ferrule assemblies
15
and
15
for covering optical fibers
14
and
14
(only one is shown throughout the drawings) in a state in which the ends of the optical fibers
14
and
14
are exposed at the tips, a plug housing
17
provided with a tubular partition wall
16
for housing and protecting the ferrule assemblies
15
and
15
, a spring cap
18
fitted and fixed to the plug housing
17
, and a boot
19
fitted to the rear part of the spring cap
18
.
The plug housing
17
is formed with shoulder part
17
a
engaging collar-like retention parts
15
a
and
15
a
placed in the latter half parts of the outer peripheries of the ferrule assemblies
15
and
15
and springs
20
and
20
are placed between the retention parts
15
a
and
15
a
and inner tube parts
18
a
and
18
a
of the spring cap
18
so that the ferrule assemblies
15
and
15
are urged forward all the time.
The retention parts
15
a
and
15
a
engage the shoulder part
17
a
, whereby tip parts A of the ferrule assemblies
15
and
15
(see
FIG. 11
; corresponding to positions of incidence and emission end faces (light reception face and light emission face) of the optical fibers
14
) are always retracted inside from front end face B of the plug housing
17
(see FIG.
11
).
In the described configuration, connection of the receptacle
2
and the optical plug
3
will be discussed with reference to FIG.
9
.
When the optical plug
3
is fitted to the receptacle
2
, the reception tubes
10
and
10
enter the plug housing
17
and at the same time, the ferrule assemblies
15
and
15
enter the reception tubes
10
and
10
.
The ferrule assemblies
15
and
15
abut the tips of the reception tubes
10
and
10
and adequate contact pressure is kept by the elastic force of the springs
20
and
20
.
In this state, the tip parts A (see
FIG. 11
) and the sleeves
13
and
13
and the lenses
9
and
9
and the sleeves
13
and
13
are placed with gaps (not shown) kept to the minimum, whereby the gap loss of the optical connector
1
is minimized, so that a transmission margin when light communication is executed can be widened.
Problem to be Solved by the Invention
By the way, in the described related art, a gap of 6 mm, for example, on the structure exists between the reception and transmission module
6
,
6
′ and the optical fiber
14
,
14
, and the sleeve
13
,
13
6 mm long, for example, is placed so as to bridge the gap. Preferably, the gap between the reception, transmission module
6
,
6
′ and the sleeve
13
,
13
and the gap between the optical fiber
14
,
14
and the sleeve
13
,
13
is made zero from the relation of the described gap loss.
However, it is very difficult to make the gaps zero because of the combination of the members; in even the described optical connector
1
, a slight gap occurs in some cases and a light power loss occurs.
Taking the gap between the transmission module
6
′ and the sleeve
13
(not shown) as an example in the description, the transmission module
6
′ usually uses a light emitting diode and therefore if a gap occurs, a part of light emitted and diverged (emitted like radiation) from the light emitting diode leaks through the gap. A part of the leakage light is not again incident on the light transmission member
11
of the sleeve
13
, of course; thus the light leakage part leads to a light power loss.
Since a plastic optical fiber (POF) having the same N.A. (numerical aperture)=0.5 as the optical fiber
14
has been used as the light transmission member
11
, there is a limit on reception of light from the transmission module
6
′ (light emitting diode). Of course, larger light than the N.A. of the light transmission member
11
exists, thus a light power loss cannot be avoided if the above-mentioned gap is contained.
Letting the refractive index of the core be n
1
and that of the clad be n
2
(n
1
>n
2
), the above-mentioned N.A. is defined by a relational expression of N.A.=[(n
1
)2−(n
2
)2]½.
On the other hand, the above-described light power loss is caused by not only the gap, but also by the assembly state (position) of the sleeve
13
,
13
.
That is, the receptacle
2
is made of a synthetic resin and a minute protrusion (not shown) for retaining the sleeve
13
is formed in the reception tube
10
molded integrally with the receptacle
2
and the sleeve
13
having the metal holder
12
is inserted into the reception tube
10
. When the sleeve
13
is inserted, the minute protrusion is scraped, for example, by the holder
12
and a longitudinal or lateral shift occurs in the optical axis. Resultantly, a light power loss occurs.
Giving a more detailed description, the sleeve
13
is ground on both end faces, thus the possibility that the end face of the holder
12
may be an edge is high and when the sleeve
13
is inserted into the reception tube
10
, it is hard to say that the minute protrusion functions normally.
For example, if four minute protrusions are formed at equal intervals in the reception tube
10
and the sleeve
13
is inserted in an insertion axis shift state, at least one of the minute protrusions is scraped by the end face of the holder
12
or is excessively compressed and crashed or broken.
Thus, it is easily understood that the inserted sleeve
13
loses stability, causing a shift to occur in the optical axis.
Therefore, also in this case, like the above-described gap problem, it is said that a light power loss cannot be avoided.
On the other hand,
FIG. 12
graphs the optical axis shift (on horizontal axis, mm units) in a state in which the above-mentioned gap (gap amount, mm units) is contained and the light power loss (on vertical axis, dB units) to relate them to each other.
As also seen in the figure, it is said that the gap and the optical axis shift largely cause the light power to be lost. It is preferred that the gap amount and the optical axis shift are extremely small and how to manage them becomes a point for decreasing the light power loss. If the light power loss can be decreased, it is made possible to widen a margin optically downstream from the optical connector
1
.
By the way, the sleeve
13
is manufactured through a large number of steps, thus it is preferred that c
Amari Alessandro V.
Spyrou Cassandra
Sughrue & Mion, PLLC
Yazaki -Corporation
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