Optical module, board mounted optical module, and assembly...

Details Optical module, board mounted optical module, and assembly... Optical module, board mounted optical module, and assembly...

2000-09-14

2002-12-03

Lee, John D. (Department: 2874)

Optical waveguides

With disengagable mechanical connector

Optical fiber to a nonfiber optical device connector

C385S092000

Reexamination Certificate

active

06488416

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an optical module, a board mounted optical module, and method of assembly of an optical module. More specifically, the invention relates to an optical module for transmitting or receiving an optical signal, and a board mounted optical module of this kind, and to a method of assembly of an optical module of this kind.
Because of explosive use of the Internet and portable telephones, the construction of optical communication systems that offer high speed and large capacity have been promoted rapidly, and, hence, an even further reduction in the cost of optical components that are to be used in such systems is desired. On the other hand, in the board mounting process, since the jackets of optical fibers used in the optical modules have a low heat resistance, it is difficult to employ the convenient, low-cost reflow mounting process with the use of solder (i.e. mounting a component on a mount board by the solder reflow process) that is widely used in mounting electronic components. For this reason, although it becomes costly, a technique of individually mounting, only the optical modules has been adopted. Moreover, since it is difficult to automate a process of reeling the optical fiber on the mount board, the assembly process was complicated.
K. Kurata et al. have reported an optical module, which has a simplified connector structure that enables an optical fiber to be detachably connected and which is compliant with the mounting process using reflow soldering (hereinafter referred to as “compliant with the reflow mounting process”), in IEEE Trans. CPMT, vol.19, p.524 (1966).
FIG. 1
herein shows an example of board mounting with the use of an optical module, as described above, which is compliant with the reflow mounting process, and the housing configuration of the mount boards in optical transmission equipment. Optical modules
31
compliant with the reflow mounting process together with electronic components, such as an IC
20
, an IC
21
, etc., are mounted on a mount board
6
collectively by the solder reflow process. An electric connector
22
, which has electric connection pins
23
, is mounted on the mount board
6
, and an adapter
29
for optical connection is fixed to the mount board
6
with screws. After that, a simplified connector
30
terminating an optical fiber
27
for a module is attached to the optical module
31
, and a standard optical connector
1
that terminates the other end of the fiber is inserted in the adapter
29
. Then, the mount board
6
on which each component is mounted is inserted along guides
28
mounted on the enclosure of the optical communication equipment to establish a connection between the adapter
29
for optical contact and the standard optical connector
1
of the optical fiber
27
supported on a connector fixed post
25
of the enclosure, as well as the connection between the electric connection pins
23
and an electric connector
24
of the electric wiring
26
supported on the same.
This structure has the following features.
(1) The optical module
31
and the electronic components can be reflow mounted collectively on the mount board
6
.
(2) The adapter
29
for achieving optical contact is fixed on the mount board
6
with screws.
(3) The simplified connector
30
of the optical module
31
and the adapter
29
for optical contact are connected with the optical fiber
27
.
More specifically, the simplified connector
30
attached to one end of this fiber
27
and the optical module
31
are optically connected, and the standard optical connector
1
provided at the other end thereof is optically connected to the optical adapter
29
.
In structures like this, because the optical fiber is detachably connected and the structure is compliant with the reflow mounting process, there is the advantage that the optical modules can be reflow mounted with electronic components collectively. However, since the fiber
27
intervenes between the optical module
31
and the adapter
29
, there is a problem that the reeling process for supply of the fiber
27
is troublesome. Moreover, since this configuration requires a portion where the fiber
27
is arranged, there is a problem that the mount board becomes larger by that amount, which is contrary to the object of miniaturization of the optical module.
Here, the reason for providing the fiber
27
in this way can be ascribed to the following fact. In the above-described optical module
31
, which is devised to be compliant with the reflow mounting process, the mechanical fixation strength to the mount board for direct optical connection with an enclosure is structurally insufficient. Therefore, this module doesn't accommodate a receptacle part which a normal optical connector is directly attached to and detached from. That is, in this construction, attachment/detachment of the normal optical connector
1
is performed through the intermediary of the separately provided optical adapter
29
.
Moreover, in the optical module described in Japanese Patent Prepublication No. 5-335603, the optical module has a plate-like connection part that contacts a wide area of the mount board during the reflow process in order to increase the mechanical connection strength to the mount board.
FIG. 2
shows its structure. A package main body
42
is provided with an optical connector
43
capable of being detachably connected to an external optical connector, and further comprises lead parts
44
a
for making connection with a circuit board
41
and a plate-like connection part
44
b
that is to be soldered to the circuit board
41
during the reflow process and that has a large contact area to reinforce the mechanical connection strength. However, it is difficult to miniaturize this optical module because the connection part
44
b
having a large contact area needs to be mounted on the circuit board, and it is likely that the module may move in the plane of the board during the reflow process; therefore this, module is not suitable for connection with an enclosure that uses a multiplex connector.
On the other hand, the optical module disclosed in the Japanese Patent Prepublication No. 8-57746 and the optical module disclosed in the Japanese Patent Prepublication No. 8-15578 have receptacle structures that allow the attachment/detachment of optical fibers with respect to the main bodies, wherein both electric wiring pins and stud pins for fixing the receptacle part ensure the mechanical strength that can stand a stress at the time of the attachment/detachment of the optical fiber. Although the problem of the reeling process in the supply of optical fiber is solved in the optical modules as described above, the optical module needs to be mounted separately and so it is difficult to mount the optical module together with electronic components collectively using the solder reflow process.
SUMMARY OF THE INVENTION
With the above-mentioned conventional technology, by providing an attaching/detaching mechanism for an optical fiber whose heat resistance is low and a reflow mounting mechanism, the optical fiber together with the electronic components can be reflow mounted collectively. However, as shown in
FIG. 1
, in such an example where a large stress is applied to the optical module when the mount board is attached to and detached from the enclosure, the reflow mounting only by soldering is considered to be insufficient in terms of the mechanical fixation strength of the optical module to the mount board. Therefore, to circumvent this problem, a configuration is adopted wherein an optical adapter for external connection is provided separately and this adapter is connected to the optical module via an optical fiber. Now, with this structure, a step for connection of an optical fiber will newly occur, and hence the troublesome reeling process in the supply of the optical fiber and the screw fastening process of the optical adapter still remains necessary. Consequently, with this structure, it is difficult to reduce the cost of mounting. Furt

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