Optical fiber block assembly for minimizing stress...

Details Optical fiber block assembly for minimizing stress... Optical fiber block assembly for minimizing stress...

2002-10-21

2004-06-29

Wille, Douglas (Department: 2814)

Optical waveguides

Accessories

External retainer/clamp

C385S049000

Reexamination Certificate

active

06757471

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical-fiber-block assembly for connecting a planar-light circuit (PLC) to an optical fiber. In particular, the present invention relates to an optical-fiber-block assembly that includes an optical-fiber block and a glass cover for minimizing stress imposed on the optical fiber, and its related contacting device.
2. Description of the Related Art
In WDM (Wavelength Division Multiplexing) communication systems, optical signals with multiple N wavelengths are transmitted simultaneously through a single strand of optical fiber to accommodate a large volume of data traffic. To this end, a PLC (Planar Lightwave Circuit) is widely used for the optical-signal processing, such as the optical signal's bifurcation, modulation, switching, multiplexing, and so forth. To connect the PLC to an optical fiber, an optical-fiber block is typically employed. The optical-fiber block is also one of the optical components that are used as an input/output port of a Micro-Optic device.
FIG. 1
illustrates a connection state of a conventional Planar-Lightwave Circuit
10
(PLC) with an optical-fiber block
20
and
30
. As shown in the drawing, each of the optical blocks
20
and
30
is connected to the PLC
10
at its input/output side and also connected to each single fiber F
1
and a ribbon fiber F
2
. In operation, N wavelengths (N is a natural number) are inputted in the input port of the PLC
10
via the single fiber F
1
, then the inputted optical signals are multiplexed while passing through the PLC
10
. Each multiplexed optical signal is then outputted through the ribbon fiber F
2
, respectively. An adhesive B, such as epoxy resin, is used to fix the alignment of the input/output side of the optical fiber block
20
and
30
, each being connected to the input/output port of the PLC
10
. In addition, glass covers C
1
through C
4
are adhered to the input/out side of the PLC
10
as well as the input/output side of the optical fiber block
20
and
30
, respectively. The glass covers C
1
and C
2
are adhered to the input/output side of the PLC
10
for processing, and the glass covers C
3
and C
4
are adhered to the input/output side of the optical fiber block
20
and
30
to support each aligned optical fiber. In the drawing, the reference mark S indicates a silicon substrate on which the optical circuit is provided to process optical signals.
With reference to
FIGS. 2 through 4
, the components of an output side optical-fiber block
30
in accordance with the related art will be explained hereinafter. As depicted in the drawings, the conventional optical-fiber block
30
is divided into a fiber-alignment area
301
in which the bare fibers BF whose coatings are peel-off are aligned, and a stress-relief-depth area
302
for relieving the stress that is generated due to the coating thickness of the ribbon fiber. For the fiber-alignment area
301
, a plurality of V-grooves
310
is provided to receive the bare fibers BF. Note that the fiber-alignment area
301
and the stress-relief-depth area
302
are created in a very precise manner through a wet-etching process.
A vital function of the fiber block
30
is to support the bare fiber BF disposed in the V-groove
310
, to fixate or secure the alignment of each bare fiber BF, and to have the bare fibers BF positioned at a regular interval from each other. Accordingly, it is absolutely important to manufacture a precise V-groove
310
and a glass cover C
4
that is in contact with the fiber block
30
. Referring to
FIG. 4
, the cover C
4
is attached to the fiber-alignment area
301
for supporting the upper portion of the bare fibers BF aligned thereon. Then, the fiber block
30
and the cover C
4
undergo a polishing process to be etched in the form of dicing them to a designated degree (&thgr;), thereby finalizing the alignment state of the fiber.
However, when the fiber block and the fiber are assembled in the manner shown in
FIG. 2
, that is, if the bare fibers BF are aligned in each V-groove
310
, and the glass cover C
4
is used to fixate the alignment state after injecting epoxy resin B, the following problems inevitably occur.
First, as shown in
FIG. 3
, the V-groove
310
, the bare fiber BF, and the glass fiber C
4
form a contact point at three different locations, P
1
, P
2
, and P
3
, respectively. Although these three contact points P
1
, P
1
, and P
3
, are necessary to maintain the precise alignment state of the bare fibers BF, they experience a considerable amount of stress due to the contraction and expansion of the adhesive B, which was injected to the contact points during the fabrication process. In the drawing, the stress intensity is indicated by the length variation of the arrow, and the direction of the arrow indicates the direction of the stress distribution. As evident in the stress distribution according to the arrow's direction, the stress is concentrated at the three contact points, and particularly, the stress is highest at the contact point P
3
, where the bare fiber comes in contact with the glass cover C
4
. In the long run, such stress eventually fatigues the adhesion at the contact point P
3
, thus causes delamination, a phenomenon where the boundary sides forming the contact point fall apart or become delaminated. This process eventually deteriorates the reliability of the optical components in general.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an optical-fiber-block assembly that includes an optical-fiber block with minimum stress concentration and a cover.
It is another object of the present invention to provide a contacting device therewith.
According to one aspect of the invention, there is provided an optical-fiber-block assembly, which includes an optical-fiber block for connecting a lightwave element to a fiber, and a cover that is in contact with the optical-fiber block for supporting the fiber disposed along at least one V-groove of the optical-fiber block, wherein the cover, for the purpose of minimizing stress concentration, includes: (a) a planar portion having a top surface and a bottom surface; (b) at least one ridge in a designated position of the bottom surface for supporting the fiber disposed in the V-grooves, and (c) a slot adjoined to the ridge gap receiving an adhesive material.
Another aspect of the present invention provides a contacting device using the cover described above which connects a planar-lightwave circuit to an optical fiber. The device includes: (a) an optical block on which at least one optical fiber is aligned along a V-groove; and (b) a cover in a spatial contact relationship with the optical-fiber block using an adhesive material.
Yet another aspect of the present invention provides an optical-fiber-block assembly for minimizing stress concentration using an optical-fiber block having a fiber-alignment area mounted with a plurality of V-grooves at which optical fibers are disposed and a stress-relief-depth area, which is an extended part formed by etching the fiber-alignment area, for relieving stress that is caused by the coating thickness of the fiber. The optical-fiber block further comprises: (a) a first fiber-alignment area having a width within a range that does not contact an external side of the aligned bare fiber, in which the first V-grooves with a constant width are uniformly aligned and extended therefrom; and (b) a second fiber-alignment area having a second V-grooves extending from the first V-grooves and in contact with the external side of the aligned bare fiber, wherein the width of the first V-grooves is substantially wider than the width of the second V-grooves.
The foregoing and other features and advantages of the invention will be apparent from the following, more detailed description of preferred embodiments as illustrated in the accompanying drawings in which reference characters refer to the same parts throughout the various views. The drawings are not necessarily to scale, the emphasis ins

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