Patent Publication Number: US-2002005988-A1

Title: Microetalon for DWDM telecommunications applications

Description:
[0001] REFERENCE TO PENDING PRIOR PATENT APPLICATION  
     [0002] This patent application claims benefit of pending prior U.S. Provisional Patent Application Serial No. 60/204,967, filed May 17, 2000 by Chris Duska et al. for MICROETALON FOR DWDM TELECOMMUNICATIONS APPLICATIONS (Attorney&#39;s Docket No. CORE-64 PROV), which patent application is hereby incorporated herein by reference. 
    
    
     
       FIELD OF THE INVENTION  
       [0003] This invention relates to etalon telecommunication apparatus and methods in general, and more particularly to apparatus and methods using etalons of a reduced size.  
       BACKGROUND OF THE INVENTION  
       [0004] A traditional etalon consists of two parallel plates separated by an air gap. Typically the air gap is formed by positioning one or two block spacers on opposite ends of the plates. Optical contact may hold the plates to the spacers. This optical contact may be van der Waals forces established between the opposing highly polished surfaces of the block spacers and the plates.  
       [0005] These air gap etalons are also used by forming the spacers out of non-heat-sensitive materials and hermetically sealing the etalon in a closed package, such that changes of temperature do not affect the performance of the etalon.  
       [0006] For some applications, however, the etalons need to be very small, and it is difficult to create the etalons using the traditional construction technique. Among other things, as the size of the components is reduced, the surface area contact between the plates and the block spacers is also reduced. As such, it is no longer possible to hold the block spacers and parallel plates together by the traditional optical contact.  
       [0007] Additionally, alignment can be important in many etalon applications, since the angle of incidence of the input light beam can affect the output characteristics of the etalon. As a result, alignment must be provided in many applications. In some circumstances, it can be convenient to align the etalon before it is hermetically sealed in a closed package.  
       [0008] However, the performance characteristics of the air gap etalon can change if there is a variation in the etalon&#39;s air environment between the time of alignment and the time of hermetic sealing. Therefore, it would be an advance in the art to provide an improved etalon having reduced size and/or a hermetically sealed air gap.  
       SUMMARY OF THE INVENTION  
       [0009] Accordingly, one object of the invention is to provide an improved etalon having a reduced size.  
       [0010] Another object of the invention is to provide an etalon with a hermetically sealed chamber.  
       [0011] A further object of the invention is to provide an etalon with a single block spacer defining a cavity.  
       [0012] A still further object of the invention is to provide a method for filtering a light source using an etalon having a reduced size.  
       [0013] And still another object of the invention is to provide a method for filtering a light source using an etalon having a hermetically sealed chamber.  
       [0014] With the above and other objects in view, as will hereinafter appear, there is provided an etalon comprising a first plate and a second plate positioned in parallel to one another and separated by a given distance; a single block spacer extending the given distance between the first plate and the second plate; and the single block spacer defining a chamber extending the given distance between the first plate and the second plate.  
       [0015] In accordance with a further feature of the invention, there is provided a hermetically sealed etalon comprising a first plate and a second plate positioned in parallel to one another and separated by a given distance; a single block spacer extending the given distance between the first plate and the second plate; and the single block spacer defining a chamber extending the given distance between the first plate and the second plate, the block spacer defining a first perimeter surrounding the chamber adjacent the first plate and a second perimeter surrounding the chamber adjacent the second plate, wherein the single block spacer surrounds the chamber along the given distance between the first plate and the second plate, and further wherein the single block spacer forms a first seal around the first perimeter adjacent the first plate and the single block spacer forms a second seal around the second perimeter adjacent the second plate, whereby to form the hermetically sealed etalon.  
       [0016] In accordance with a still further feature of the invention, there is provided an etalon assembly comprising a light source producing a collimated beam of light; an etalon receiving the collimated beam of light and producing a light emission, the etalon comprising a first plate and a second plate positioned in parallel to one another and separated by a given distance, a single block spacer extending the given distance between the first plate and the second plate, and the single block spacer defining a chamber extending between the first plate and the second plate; and a detector for receiving the light emission from the etalon.  
       [0017] In accordance with a further feature of the invention, there is provided a method for filtering a light source using an etalon, the method comprising: producing a collimated beam of light with the light source; receiving the collimated beam of light into the etalon, the etalon comprising a first plate and a second plate positioned in parallel to one another and separated by a given distance, a single block spacer extending the given distance between the first plate and the second plate, and the single block spacer defining a chamber extending between the first plate and the second plate; and producing a light emission from the etalon.  
       [0018] The above and other features of the invention, including various novel details of construction and combinations of parts and method steps, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular devices and method steps embodying the invention are shown by way of illustration only and not as limitations of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0019] These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein:  
     [0020]FIG. 1 is a schematic perspective view of one form of a hermetically sealed etalon with a single block spacer, illustrative of an embodiment of the invention;  
     [0021]FIG. 2 is a schematic perspective view of an alternative embodiment of the invention showing an etalon with a single block spacer open at the top portion of the cavity;  
     [0022]FIG. 3 is a schematic perspective view of an alternative embodiment of the invention showing an etalon having two spacers forming a hermetic seal; and  
     [0023]FIG. 4 is a schematic view of an etalon assembly formed in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0024] The present invention is an etalon for DWDM telecommunications applications. The present invention may be constructed so as to permit a reduced size of etalon. The present invention may also be constructed such that the etalon is hermetically sealed.  
     [0025] Referring to FIG. 1, an etalon  5  is shown having two parallel plates  10  separated by a spacer  15 . Spacer  15  is formed with a chamber  20  extending therethrough, between parallel plates  10 . Spacer  15  and chamber  20  are dimensioned so as to provide an optimal surface area contact between spacer  15  and plates  10 .  
     [0026] In one preferred embodiment of the present invention, optical contact holds plates  10  to spacer  15 . Optical contact includes van der Waals forces between opposing highly polished surfaces of plates  10  and spacer  15 .  
     [0027] In a preferred embodiment of the present invention, chamber  20  is sealed around its perimeter with each parallel plate  10 . This sealing forms a hermetically sealed chamber  20  and hence a hermetically sealed etalon  5 .  
     [0028] More particularly, and still referring now to FIG. 1, a hermetically sealed etalon  5  is shown with single block spacer  15  completely surrounding chamber  20  along the distance between plates  10 . Single block spacer  15  forms a seal around each perimeter  30  of chamber  20 , i.e., adjacent the contact area between plates  10  and spacer  15 . These sealed perimeters  30  form a hermetically sealed chamber  20  and, therefore, form a hermetically sealed etalon  5 .  
     [0029] In one preferred form of the invention, plates  10  comprise fused silica and preferably have a reflective coating in their inside surfaces, i.e., the surfaces facing chamber  20 A. Preferably both of the plates  10  has a non-parallel or non-reflective outer surface, e.g., a non-parallel outer surface  11 .  
     [0030] And in one preferred form of the invention, single block spacer  15  comprises a glass having a low thermal expansion. By way of example but not limitation, spacer  15  may be formed out of ULE or ZERODUR.  
     [0031] Looking next at FIG. 2, an etalon  5 A is shown with a single block spacer  15 A having an open chamber  20 A. Single block spacer  15 A is formed so as to provide an enhanced surface area contact between spacer  15 A and plates  10 . In this embodiment of the invention, however, chamber  20 A is not hermetically sealed within etalon  5 .  
     [0032] Referring now to FIG. 3, an etalon  5 B is shown with two portions  25  forming spacer  15 B. The two spacer portions  25  surround chamber  20 B along the entire distance between plates  10 . In addition, a seal is formed around each perimeter  30  adjacent to the contact area between plates  10  and spacer  15 B. These sealed perimeters  30  form a hermetically sealed chamber  20  and, therefore, form a hermetically sealed etalon  5 .  
     [0033] In a preferred embodiment of the invention, and referring now to FIG. 4, etalon  5  (or  5 A or  5 B) may be used in conjunction with an etalon assembly  35 . Etalon assembly  35  includes a light source  40 , etalon  5  (or  5 A or  5 B), and a detector  45 . Light source  40  produces a collimated light beam  50 . Etalon  5  (or  5 A or  5 B) receives the collimated light beam  50  and produces a light emission  55 . Detector  45  receives emission  55  from etalon  5  (or  5 A or  5 B).  
     [0034] A method also is disclosed for filtering light source  40  using etalon  5  (or  5 A or  5 B). The method includes producing a collimated light beam  50  with light source  40 , passing the collimated light beam  50  into etalon  5  (or  5 A or  5 B), and producing a light emission  55  from etalon  5  (or  5 A or  5 B).