Abstract:
A packaging method and apparatus that improve the yield and reliability of multi-port fiber optical devices are disclosed. The method utilizes a flexible metallic connection between a solid frame holding input and output optics (including fibers, collimators) and the main body of an optical device. Optical alignment and realignment are accomplished following the soldering and/or hermetically sealing of the entire package. A flexible connection is made with permeable material that has minimum stress memory associated with realignments and can tolerate repeated adjustment or realignment without becoming structurally unsound.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to optical components and their use in optical communications and more particularly to a method and apparatus for achieving optical packages that can be realigned following hermetical sealing. 
     2. Background Art 
     Optical fiber and related devices provide new avenues to transmit light and hence are becoming important in areas of optical communication, remote optical measurement and sensing. In many demanding applications, long operating lifetimes up to 25 years and low device failure rates are desired. 
     Many of the prior art telecom components are packaged utilizing soldering processes as described, for example, in U.S. Pat. No. 6,019,522 and other similar patents. Following the soldering process, however, many devices suffer degradation of the original optical alignment. Frequently, devices are reworked to recover some of the insertion losses. Due to the properties of the prior art packaging materials used, however, individual devices can only be reworked for a few times. 
     There are several disadvantages associated with these prior packaging methods. For instance, the number of times a device can be reworked is limited and due to the properties of the materials used, it is often difficult to avoid under or over adjustments. There is therefore a need for an improved packaging method and design such that the limitation on realignments can be substantially reduced. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a method and configuration of fiber optic device packaging with realignment capability is disclosed. In this new design, a flexible interconnection between the solid frame holding the optics and the remaining part is provided. These interconnections are made with a highly permeable alloy such that realignment can be performed repeatedly without risking device integrity. In addition, the new design allows tight fitting of optics and its holding frame, making it possible to use epoxy to secure the interfacing seal instead of solder. This may substantially increase the product yield as many reliability and stability related problems are removed. Several embodiments that incorporate this interconnection are revealed. The invention can be used to enhance manufacturing yields of optical communication devices containing single-, dual- and multi-fiber collimators, mirrors and other optical elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The aforementioned objects and advantages of the present invention, as well as additional objects and advantages thereof, will be more fully understood hereinafter as a result of a detailed description of a preferred embodiment when taken in conjunction with the following drawings in which: 
     FIG. 1A is a simplified diagram illustrating an embodiment of the present invention where an optical device consists of two fiber collimators and a filtering element; 
     FIG. 1B is a simplified diagram illustrating the side view of FIG. 1A; 
     FIG. 2A is a simplified diagram illustrating a multi fiber collimator inserted into a flange, with a flexible interconnect; 
     FIG. 2B is a diagram illustrating the side view of FIG. 2A; 
     FIG. 3A is a diagram illustrating an embodiment of the present invention where a multi fiber collimator can be soldered to an input/output flange; 
     FIG. 3B is the side view of the embodiment presented in FIG. 3A; 
     FIG. 4 is a schematic diagram illustrating an optical device and an associated flange with a flexible interconnect; 
     FIG. 5 is a schematic diagram illustrating an optical device and associated flange with a flexible interconnect where alignment screws are incorporated; and 
     FIG. 6 depicts an optical device and associated flange with another form of flexible interconnect where alignment screws are incorporated. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following the details of various preferred embodiments of the present invention are disclosed. The preferred embodiments are described with the aid of the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     FIGS. 1A and 1B are diagrams illustrating an optical assembly  100  in accordance with the present invention. The optical device consists of two multi fiber collimators  130 ,  134 , a wavelength-filtering device  132  and a package  110  with a flexible interconnect  112 . The collimators  130 ,  134  and the outer package  110  are soldered/brazed together such that hermetical seals are formed. Input and output optical fibers  120  through  126 ,  140  through  146  are used to couple light into and out of the device. The collimators ensure the proper interface with the filtering device such that a small range of angles are involved. The flexible interconnect  112  is made with highly permeable alloy such as Carpenter 49® alloy. Carpenter 49® alloy is a non-oriented 48% nickel/iron alloy processed for high permeability that is available from Carpenter Technology Corporation of Wyomissing, Pa. Other comparable materials may be substituted for this alloy. Realignment of the device can be performed repeatedly by changing the relative orientation of the two collimators without risking device integrity. 
     Referring now to FIGS. 2A and 2B, an interface section  200  of an optical assembly is disclosed. This interface section consists of a multi fiber collimator  230  with the accompanying input/output flange  210  where a flexible interconnect  212  forms part of the flange. The collimator  230  and the flange  210  are soldered/brazed together such that a hermetical seal is formed. Input and output optical fibers  220  through  226  are used to couple light into and out of the device. The collimator ensures the proper interface with the optical device such that a small range of angles are involved. The flexible interconnect  212  is made with highly permeable alloy such as Carpenter 49® alloy. Realignment of the device can be performed repeatedly by changing the relative orientation of the collimator and the remaining part of the assembly without risking device integrity. 
     Referring now to FIGS. 3A and 3B, an interface section  300  of an optical assembly is disclosed. This interface section consists of a multi fiber collimator  330  with the accompanying input/output flange  310  where a flexible interconnect  312  forms part of the flange. The collimator  330  and the flange  310  are soldered/brazed together such that a hermetical seal is formed. Input and output optical fibers  320  through  326  are used to couple light into and out of the device. The collimator ensures the proper interface with the optical device such that a small range of angles are involved. The flexible interconnect  312  is made with highly permeable alloy such as Carpenter 49® alloy. Realignment of the device can be performed repeatedly by changing the relative orientation of the collimator and the remaining part of the assembly attached to the other end of  312  without risking device integrity. Several air channels  314  are provided which are used for introducing soldering material in the soldering and brazing process. 
     Referring now to FIG. 4, an interface section  400  of an optical assembly is disclosed. This interface section consists of an optical device  430  with the accompanying input/output flange  410  where a flexible interconnect  412  forms part of the flange. The outer packaging material of the optics  430  and the flange  410  are soldered/brazed together such that a hermetical seal is formed. The optics can be a mirror, a lens, a filter, a properly terminated optical fiber, an optical window or a nonlinear crystal. Further, the optics may be formed by multiple optical elements combined as a sub assembly. The surfaces of the optics may be coated for antireflection and or other desired filtering functions such as band pass or edge filtering. The flexible interconnect  412  is made with highly permeable alloy such as Carpenter 49® alloy. Realignment of the device can be performed repeatedly by changing the relative orientation of the optics and the remaining part of the assembly attached to the other end of  410  without risking device integrity. 
     Referring now to FIG. 5, an interface section  500  of an optical assembly is disclosed. This interface section consists of an optical device  530  with the accompanying input/output flange  510  where a flexible interconnect  512  forms part of the flange. The section further consists of alignment arms  514  attached to the flange where alignment screws  516  are used to adjust and maintain optical alignment. The outer packaging material of the optics  530  and the flange  510  are soldered/brazed together such that a hermetical seal is formed. The optics can be a mirror, a lens, a filter, a properly terminated optical fiber, an optical window or a nonlinear crystal. Further, the optics may be formed by multiple optical elements combined as a sub assembly. The surfaces of the optics may be coated for antireflection and or other desired filtering functions such as band pass or edge filtering. The flexible interconnect  512  is made with highly permeable alloy such as Carpenter 49® alloy. Realignment of the device can be performed repeatedly by changing the relative orientation of the optics (through aligning screws  516 ) and the remaining part of the assembly attached to the other end of  510  without risking device integrity. 
     Referring now to FIG. 6, an interface section  600  of an optical assembly is disclosed. This interface section consists of an optical device  630  with the accompanying input/output flange  610  where a flexible interconnect  612  forms part of the flange. The section further consists of alignment arms  614  attached to the flange where alignment screws  616  are used to adjust and maintain optical alignment. The outer packaging material of the optics  630  and the flange  610  are soldered/brazed together such that a hermetical seal is formed. The optics  630  can be a mirror, a lens, a filter, a properly terminated optical fiber, an optical window or a nonlinear crystal. Further, the optics may be formed by multiple optical elements combined as a sub assembly. The surfaces of the optics may be coated for antireflection and or other desired filtering functions such as band pass or edge filtering. The flexible interconnect  612  is made with highly permeable alloy such as Carpenter 49® alloy. Realignment of the device can be performed repeatedly by changing the relative orientation of the optics (through aligning screws  616 ) and the remaining part of the assembly attached to the other end of  610  without risking device integrity. 
     Having thus disclosed various embodiments of the present invention, it will be understood that numerous alternative embodiments are contemplated. By way of example, the interconnect between respective flanges may be made of many other highly permeable materials and may be formed of a material which is different from the material of which the flanges are made. Moreover, while the interconnect is disclosed as having a constraint reduced thickness, the invention also contemplates having an interconnect having a gradually reduced thickness such as one that is tapered or arched. The intent is to facilitate repeated bending with a material that will retain each new bend and remain structurally sound despite many such adjustments. Therefore the scope of the invention is limited only by the appended claims and their equivalents.