Optical waveguides – Accessories – External retainer/clamp
Reexamination Certificate
1999-02-08
2001-04-10
Schuberg, Darren (Department: 2872)
Optical waveguides
Accessories
External retainer/clamp
C385S147000, C385S094000
Reexamination Certificate
active
06215944
ABSTRACT:
TECHNICAL FIELD
This invention relates to a sealed fiber array for an optical transmission module or the like, capable of performing hermetic sealing (hereinafter, called “sealing”) on a package of the transmission module or the like by the fiber array itself.
BACKGROUND ART
A conventional sealed fiber array for an optical transmission module is disclosed, for example, in JP-A-8-179171. In such a sealed fiber array, optical fibers are arranged in respective V grooves, and both ends of the fiber array are polished optically. The end of the fiber array to be exposed to outside of a package of the transmission module is capable of being connected to an optical connector.
To allow connection of such a package to the optical connector, it is necessary to provide one or more grooves for respective guide pins in a substrate of the sealed fiber array. In a traditional sealed fiber array having such V-grooves, the fiber grooves and the guide grooves extend from one end of the substrate to the other, so that guide holes extend through the sealed fiber array from its one end to the other. In this case, however, ambient air may enter into the package, through gaps between the guide holes and the guide pins. In a package in which one or more semiconductor elements such as laser diodes and/or photodiodes are provided, the elements tends to be degrade when exposed to ambient air.
DISCLOSURE OF THE INVENTION
It is therefore an object of the invention is to provide an improved sealed fiber array in which ambient air is prevented from entering into the package through gaps between the guide holes and the guide pins.
According to one aspect of the present invention, there is provided a sealed fiber array comprising: a lower substrate provided in its lengthwise direction with one or more fiber grooves for arranging respective fibers, and one or more guide grooves for arranging respective guide pins to be connected to an external connector; and an upper substrate arranged on the lower substrate so as to fixedly secure the guide pins and the fibers, the upper substrate having the same dimensions in the lengthwise direction and the direction perpendicular thereto as those of the lower substrate; the guide grooves of the lower substrate and the upper substrate forming one or more guide holes such that ambient air is prevented from entering from the side where the guide holes are formed toward the side opposite thereto.
In accordance with such a fiber array, as a sealing function is obtained by forming one or more guide holes such that ambient air is prevented from entering from the side where the guide holes are formed toward the side opposite thereto, one or more elements in a package may not degrade by entering ambient into the package, through gaps between the guide holes and the guide pins.
Preferably, each of the guide grooves has a length in the lengthwise direction thereof, which is not greater than that of the lower substrate in the lengthwise direction thereof.
In this way, by forming the guide grooves not from one end of the lower substrate, the end opposite thereto, but from the one end halfway to the end opposite thereto, the guide holes do not extend to the side (the side to be coupled to one or more optical elements; for example, refer to the above-mentioned JP-A-8-179171) opposite to the side (the side to be connected to connectors) where the guide holes are formed. Thereby, as the sealing function is obtained, one or more elements in a package may not degrade by entering ambient into the package, through gaps between the guide holes and the guide pins.
In this case, fibers extend over the lower substrate in the lengthwise direction thereof, so that the fiber grooves extend over the lower substrate thereof in the lengthwise direction thereof.
Preferably, each of the guide grooves has a length in the lengthwise direction thereof, which is same as that of the lower substrate in the lengthwise direction thereof, and an adhesive is filled at least partly in the guide grooves except the region which extends from one end thereof over a distance which is not greater than the length in the lengthwise direction thereof.
For each of the guide grooves, an adhesive is filled at least partly in the guide grooves except the region which extends from one end thereof over a distance which is not greater than the length in the lengthwise direction thereof, so that the guide holes do not extend to the side opposite to the side where the guide holes are formed. Thereby, as the sealing function is obtained, the elements may not degrade by entering ambient into the package, through gaps between the guide holes and the guide pins. In this case, it is unnecessary to shift the guide pins to be inserted into respective guide holes from an accurate position due to filling with the adhesive.
Preferably, each of the guide grooves has a length in the lengthwise direction thereof, which is same as that of the lower substrate in the lengthwise direction thereof, each of the guide pins extending over a length which is not greater than the length of the guide grooves in the lengthwise direction thereof, and an adhesive is filled between the guide grooves and the corresponding guide pins.
In this way, the adhesive is filled between the guide grooves and the corresponding guide pins, so that more effective sealing function can be obtained. It is also unnecessary to shift the guide pins to be inserted into respective guide holes from an accurate position due to filling with the adhesive.
Preferably, the upper and lower substrates comprise ceramics or glass.
It is preferable to select materials of the upper and the lower substrates in accordance with the coefficients of thermal expansion of one or more optical elements facing to an incident end face of each fiber. In accordance with the sealed fiber array, to fulfill such a requirement, ceramics or glass is selected as those materials. In the case where one or more laser diodes and/or photodiodes are used as optical elements, it is a general practice that gaps are provided between the fiber arrays and each of the laser diodes or photodiodes, and it is thus unnecessary to consider such a thing especially. Nevertheless, it is preferable to match the coefficients of thermal expansion of the optical elements with each other.
Preferably, the lower substrate is made by a press molding.
The guide grooves can be easily formed in the lower substrate by Si etching. However, the guide grooves on the lower substrate made of ceramics or glass, are provided by grinding. In grinding, since a grinder having a certain diameter (for example, several tens mm) is typically used, when the guide grooves are formed from the end thereof halfway to the end opposite thereto, each end of the guide grooves is rounded even if the grinding is stopped halfway. Therefore, the guide grooves having a desired shape at the end cannot be formed. This is the ground why the lower substrate is made by a press molding. The press molding may be carried out by a method described in JP-A-8-46819, for example.
Preferably, the surface of the lower substrate formed with the fiber grooves and the guide grooves, and the surface of the upper substrate to be jointed on the surface of the lower substrate, are metallized and jointed with each other by a solder.
In a module which requires sealing, even an adhesion with a resin may cause trouble because one or more optical elements (especially laser diodes and photodiodes) in the package tend to be degraded by a gas arising from the resin itself. To avoid such a problem, the surface of the lower substrate formed with the fiber grooves and the guide grooves, and the surface of the upper substrate to be jointed on the surface of the lower substrate, are jointed with each other by a solder. As the ceramics or the glass is not wet with the solder, it is preferred that those surfaces to be jointed with each other are metallized.
Preferably, the solder comprises an Au-based solder.
The elements may degrade if flux is used with the solder, so that it is preferred to use the Au-base
Fukuyama Masashi
Ota Takashi
Assaf Fayez
Burr & Brown
NGK Insulators Ltd.
Schuberg Darren
LandOfFree
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