~u. n
`c:Jo_C>
`~ UJ
`
`.......... =....,
`
`0,6' - '"Z- b .- e--{)
`PROVISIONAL APPLICATION FOR PATENT COVER SHEET
`
`~ .,.::::..
`c
`~ ~ This is a request for filing a PROVISIONAL APPLICATION FOR PATENT under 37 CFR 1.53(b)(2)
`'" ...,
`o
`
`c:Jo~'
`
`I Docket No. I 06948-105028 P
`
`INVENTOR(s)/APPLICANT(s)
`
`Last Name
`Holter
`Wach
`
`First Name Middle Initial
`Dwight
`J.
`L.
`Michael
`
`Residence (City and either State or Foreign Country)
`1472 Murex Drive, Naples, Florida 34102
`914 Collier Road, N.W., #6005, Atlanta, Georgia
`30318
`
`TITLE OF THE INVENTION (280 characters max)
`
`Micro Identifier System and Components for Optical Assemblies
`
`CORRESPONDENCE ADDRESS
`
`Steven P. Wigmore, King & Spalding, 191 Peachtree Street, 45 th Floor, Atlanta,
`
`STATE
`
`Georgia
`
`ZIP CODE
`
`30303
`
`COUNTRY
`
`I U.S.A.
`
`ENCLOSED APPLICATION PARTS (check all that apply)
`
`[2JSpecification
`
`Pages
`
`C8JDrawing(s) No. of Sheets
`
`37
`
`6
`
`METHOD OF PAYMENT (check one)
`
`D Small Entity Statement
`
`D Other (specify)
`
`D A check or money order is enclosed to cover the Provisional filing fee
`
`D The Commissioner is hereby authorized to charge filing fees and credit Deposit Account No. 11-0980
`
`$
`PROVISIONAL FILING FEE AMOUNT
`The InVentIOn was made by an agency ofthe Umted States Government or under contract WIth an agency
`of the United States Government:
`
`C8J No.
`
`DYes, the name of the U.S. Government agency and the Government contract number are:
`
`Respectfully submitted,
`
`SIGNATURE:
`----~~---4~~-----------------
`
`-
`Date: J~ Z 3,
`,
`
`2
`6
`oc)
`
`TYPED or PRINTED NAME:
`~--------~-----------
`
`40,447
`Reg. No.:
`-----'------
`
`Express Mail No.
`
`EK006109672US
`
`Date: June 23, 2000
`
`Page 1
`
`

`
`I
`
`Micro Identifier System and Components for Optical Assemblies
`
`5
`
`15
`
`This invention relates to facilitating automation of high quality optical
`assemblies in which waveguides are included and to methods for improving quality
`assurance and repair of such assemblies. Such assemblies have been found to be
`especially useful, for example, in telecommunications and in medical diagnostics, in
`pharmaceutical research and chemical process monitoring. Ultra high performance
`10 waveguides (including optical fibers), for example, associated with high performance
`filters and precision micro optics are now being recognized as having the potential to
`fill a critical role in the ever increasing demand for increased bandwidth in
`telecommunications and to playa significant part in providing major improvements in
`medical diagnostics and pharmaceutical applications. Waveguides described herein
`are those used in propagating light typically in the 700-2000 nm range.
`The invention further relates to a system having an identifying
`mechanism on or in high performance waveguides that is machine-readable
`(especially, by optical means, for example using a laser interference pattern) for quick
`and accurate recall of information included in the identifying mechanism. Many of
`the individual components of such optical assemblies are extremely small and
`technically complex. Differences between component assembly pieces or even
`differences within individual pieces are difficult to discern. Although the identifier in
`accordance with the present invention could be designed to serve a functional role in
`the operation or use of the waveguide, the identifier is distinct from the traditional
`functional aspects of the waveguide. The identifier avoids the need for detailed re(cid:173)
`analysis of at least one specific waveguide technical characteristic included in the
`identifier. The identifier in some applications can be a simple mark that indicates the
`orientation needed in the assembly. For other applications it may be desirable to
`incorporate a substantial amount of information.
`The etching or engraving, for example, of a cladding surface can
`provide precise and detailed product information, including: the manufacturer, the
`core and cladding dimensions, compositions, indices of refraction, any other
`In other cases additional details may be
`imprinting that has been included, etc.
`important. As indicated in Visionex patent application 08/819,979 filed March 13,
`1997, entitled "Method and Apparatus for Improved Fiber Optic Light Management,"
`the optics associated with individual waveguides can have special characteristics. For
`
`20
`
`25
`
`30
`
`35
`
`-
`
`Page 2
`
`

`
`2
`
`'=01
`
`15
`
`10
`
`example, the end face of one fiber may be intentionally angled so that its face is not
`uniformly perpendicular to its axis and the axis of a waveguide with which it is to be
`mated.
`It may be a very slight angle and it may be critical to have the end face
`precisely oriented as it mates with the waveguide. The identifier on the fiber and the
`5 waveguide provide sufficient information for the mating to be precise. One advantage
`of using the peripheral surface of a fiber end face is the relative space availability.
`The entire periphery could be utilized if information need and image clarity required.
`Similarly, the probability of that area causing fiber function limitations is low and
`could be reduced further, for example, by covering disrupted (etched/engraved)
`surface areas with material that would restore transparency to wavelengths negatively
`affected without detrimentally affecting the readability of the image. Such factors
`playa role in determining which identifier process, marking and location to utilize.
`It also may be critical to high volume production for the information to
`be read significantly in advance of the mating operation and in some cases even by a
`different manufacturer. In one embodiment of the invention the automated system,
`for example, uses pre-aligned/oriented fiber segments locked into position by a belt or
`cartridge. The belt or cartridge is fed at the mating location for placement of fiber
`segments in predetermined alignment/orientation. (see FIG 2a.) This manufacturing
`flow allows operations to be maintained at a rate that is not limited by the alignment
`function. It also allows for efficient task separations. In many cases it is desirable for
`each fiber segment end to have its own identifier. With longer segments it is
`advantageous to include some of the information at intervals along the segment. In
`such cases that the interval identifier would include distinguishing characteristic( s) to
`avoid confusion with end face identifications. The choice of location of and type of
`identifier depends on the specific application as indicated below. In some cases it
`may be desirable to have identical identifier markings inmore than one location. For
`example, in assemblies in which there will be face-to-face connection of two optical
`fiber segments, it may be desirable to include the identifiers on both the face
`periphery and the fiber wall periphery near the edge. The fiber wall peripheral
`30 markings would be readable even after face-to-face connection. This would be
`beneficial for both repair and quality assurance.
`Several embodiments ofthe identifier means are illustrated in FIG. 1 in
`which fiber 11 has a core lla and cladding llb. Fiber end face 13, which could
`include an integral filter has included in its peripheral area (near edge 17 which is the
`junction of end face 13 and fiber wa1119) identifier space 15a. Identifier 15a can be
`simply a registration mark or can include more detailed information about the fiber.
`
`20
`
`25
`
`35
`
`Page 3
`
`

`
`3
`
`End face 13 also includes in its peripheral area optional or alternative registration
`marks 15c that can be used in assuring, for example, proper rotation of fiber 11 in an
`assembly operation. It is preferable to locate the identifier in the cladding area that is
`not in the substantive evanescent field of propagating light, i.e. outside the mode field
`In a preferred embodiment the identifier is in spaces in the cladding
`diameter.
`periphery, at least in about the exterior 80 percent, advantageously in the exterior 50
`percent, especially in the exterior 20% and, in some cases, ideally in the exterior 10%
`to avoid interfering with the photon transmission purposes of the waveguide segment.
`Fiber wall 19 includes identifier space 15b which can contain the same information as
`space 15a or could contain different information.
`As shown in perspective view in FIG. 2, the system also includes
`reading means 22a, 22b, and 22c for sufficient identification to initiate appropriate
`reaction. Advantageously the system includes means for reacting to the identifier
`information, process 24, and desirably means, drive motor 23c, for appropriate
`adjustment of the placement of the waveguide, for example in mating with another
`waveguide. Thus, for example, as illustrated in FIG. 2 a waveguide (fiber segment
`21) rests on a pair of precision rollers 26 at least one of which is mounted for
`controlled rotation by drive motor 23c. Drive motor 23c is mounted on circular
`platform 28, which rotates in synchronized movement with assembly belt 29. As
`fiber segment 21 passed in the view area of camera 22c information from its identifier
`is read and passed on to processor 24. Processor 24 digests the identifier information
`and compares it with information as to, for example, the disposition of the segment
`about its axis. Segment 21 is needed to be rotated axially for perfect alignment with
`its mating assembly member 25.
`Information is then communicated from the
`processor to drive motor 23c to rotate the fiber by rotating the roller(s) 26. Cameras
`22b and 22a communicate through the processor with drive motors 23b and 23a
`respectively. Drive motor 23b is geared finer than 23c for more precise adjustment of
`fiber segment 21, which motor 23a is geared even finer than motor 23 to assure
`precise alignment. After fiber segment 21 is joined in precise alignment with piece 25
`by, for example, fusing the fused pieces picked off for subsequent inspection, use,
`distribution, etc. FIG 2a illustrates in end view cutaway drive 23a having rollers 26a
`supporting fiber segment 21a. By driving one or both rollers 26a, drive 23a
`effectively adjusts the rotation of fiber segment 21a.
`If both the mating members in mating assemblies have identification
`information on their respective peripheral areas the match could be idealized by
`appropriate to the information. Waveguides having such identification in one or more
`
`5
`
`1 0
`
`15
`
`20
`
`25
`
`30
`
`35
`
`Page 4
`
`

`
`4
`
`5
`
`10
`
`locations as substantially pennanent identification for the fiber segment another
`aspect of this invention. The use of the cladding, especially the cladding peripheral
`areas, as the location of the identifier infonnation is an especially preferred
`embodiment of this invention. The use of such identifier for quality assurance is
`another preferred embodiment of the invention.
`The identifier can be placed on each piece in a number of different
`ways on one or more surfaces of the waveguide. FIG. 3 illustrates in perspective view
`several options for placement or configuration of identifier spaces. Fiber 31 with core
`31a and cladding 31b has on its end face 33 identifier spaces 35a and 35c. In this
`embodiment different infonnation is included in space 35a from that included in
`space 35c. The infonnation in space 35a could be, for example, coded infonnation
`relating to the technology in the fiber, while the coded infonnation in space 35c could
`identify the manufacturer, plant location, manufacturing line, specific run, etc.
`Infonnation identical to that included in 35a and 35c is included in spaces 35b and
`35e respectively which are located on fiber wall 39. The location of identifier space
`on the fiber side wall pennits continuing identification after the segment is joined at
`its end face to another assembly piece. Infonnation space 35d is included to illustrate
`that a plurality of identifier spaces can be utilized when appropriate.
`Identifier infonnation can actually be imprinted in the cladding of an
`optical fiber, for example, by a technique similar to those used for fiber-Bragg
`gratings. Such gratings are nonnally applied to Ge-doped fiber core material as
`disclosed in U.S. Pat. No's. 4,807,950 (950) and 4,725,110 (110). U.S. Pat. No.
`5,235,639 discloses a method for "writing" an in line grating with high-silica glass.
`Although that technique could be rather expensive it does have some appeaL FIG 4
`illustrates fiber 41 having a core 41a and cladding 41b. Although fiber 41 has an
`identifier space 45 and infonnation thereon, it also has a series of precisely located
`disruptions 48 in the index of refraction of peripheral cladding interior. These
`disruptions 48 are induced in a manner generally consistent with the disclosure, for
`example, in the above referenced 950 and 110 patents as modified in the '639 patent.
`30 However, instead of focusing the actinic radiation in the fiber core the radiation is
`focused in the cladding. Using the cladding to locate an infonnation repository is
`It is preferable to locate the
`another important embodiment of this invention.
`disruptions in the cladding periphery, at least in about the exterior 80 percent,
`desirably in the exterior 50 percent, especially in the exterior 20% and preferably in
`the exterior 10% to avoid interfering with the photon transmission purposes of the
`waveguide segment.
`
`15
`
`20
`
`25
`
`35
`
`Page 5
`
`

`
`5
`
`5
`
`:~J
`
`15
`
`FIG 5 further illustrates purposefully created index of refraction
`disruptions 58 in cladding 51b of fiber 51 having core 51a. Since such disruptions
`can be crafted to be wavelength specific, a large number of individual wavelengths
`translated into codes are readily readable. As with the case of the surface
`identification spaces, for example in FIG 3, these sets of disruptions can be placed in
`different locations around the fiber periphery with each set, e.g., having a different
`wavelength selectivity. Thus, it would be possible to standardize a given wavelength
`or combinations of wavelengths as codes representing, e.g., specific fiber runs and/or
`product codes.
`lO In a recent Visionex patent application entitled "Optical Assembly
`with High Performance Filter," filed May 25,1999, (assigned U.S. Serial No.
`09/318,451) we disclosed but did not claim another aspect of this invention. That
`aspect is "identifier space 15" as disclosed in the following, a quote from the
`paragraph transcending pages 8 and 9 of that application: Information for cross
`referencing with U.S. Serial No. 09/318,451: Note for the new application, FIG I
`of U.S. Serial No. 09/318,451 corresponds to new FIG 7 with all numbers having first
`digit "7" and second digit the same as in the old. Thus 15 in the old is 75 in the new.
`Similarly, old FIG 4 corresponds to new Fig 6. Again in the numbering on the
`drawing the first digit for each number is changed from 4 to 6 and the second digit
`remains the same. For example, identifier spaces 45 in the old become 65 in the new.
`"In a further preferred embodiment ofthis invention the mask serves as
`a significant component in facilitating mating with other waveguide structures. Space
`15 is reserved for micro bar code, magnetic or other identification information that
`will assist in assuring appropriate alignment and mating of the optical assemblies. For
`example, the mask dimensions and characteristics could be identified. In addition the
`fiber's core and polarization axes can be identified with respect to the location of the
`identifier and the mask aperture location, configuration and dimensions. Also, the
`core dimension and location can be identified. When fiber to fiber connections are
`made, often testing and aligning can be a time consuming task. Proper information in
`the identifier space could minimize the testing burden. Using code in identifier space
`15 to reference specific, detailed computer link information would allow for unlimited
`information about the optical assembly. The identifier information could be located at
`other locations on the mask, but the space is desirably located where it could be used
`in automating manufacturing systems. If the optical assembly is likely to be end to
`end connected to another assembly in which subsequent identification is useful, for
`example as illustrated in Fig. 6 and Fig. 7, an identifier on the edge can be used."
`
`20
`
`25
`
`30
`
`35
`
`Page 6
`
`

`
`6
`
`The drawings in that application show several examples of such
`identifier spaces. (FIG. 1, 15; FIG. 3,35; FIG. 4,45; FIG. 5, 55; FIG. 6, 65 and 65a).
`Additionallanguage of the 5/25/99 patent application mentioned above
`has relevance to describe how identification would be applied to, for example,
`peripheral areas of the fiber. See page 9 beginning in line 17:
`''By using photo-resist material and standard photoresist techniques
`(see, for example, the descriptions for temporary mask formation in U.S. Patent
`5,237,630 by Hogg et aL) a temporary mask is formed in surface areas of the pre(cid:173)
`assembly filtered fiber.... The temporary mask photoresist material is applied
`uniformly over the entire filtered fiber end portion. The photoresist material is then
`exposed imagewise ... "
`(The following is new information but continues the thought) ... to
`provide the identifier information. The photoresist is removed (usually by solvent
`wash) from the appropriate surface in an image wise patter of the identifier
`information. The identifier information is then provided, for example, to the surface,
`e.g. by etching, or electrolytic deposition. In the latter case, as the temporary mask is
`removed using a solvent wash (with a different solvent) any metallic deposition
`covering the temporary mask is also removed leaving only the durable metallic
`identifier information in a precise identifier image pattern. Because the identifier
`information must be precise and be robust it is important, especially in many
`deposition environments, to assure that the substrate filter/or fiber be thoroughly clean
`before applying mask material and identifier. For some applications, a preferred
`embodiment includes the creation of the identifier by using precision laser
`etching/ engraving techniques.
`In a preferred embodiment a narrow view would include:
`A fiber optic segment having an end face, a peripheral end face surface
`and peripheral edge surface said segment including at least one machine readable
`identifier which is readable from at least one of said peripheral surfaces.
`A broader view would include:
`A waveguide including at least one machine readable identifier.
`
`5
`
`1 0
`
`15
`
`20
`
`25
`
`30
`
`K&S Docket No. 06948-105028 P
`
`Page 7
`
`

`
`•
`
`1
`
`OPTICAL ASSEMBLY WITH HIGH PERFORMANCE
`
`5 TECHNICAL FIELD
`This invention relates generally to optical assemblies, and
`more particularly to assemblies including waveguides, for example
`optical fibers, in optical connection with high performance filters.
`
`15
`
`10
`
`STATEMENT REGARDING RELATED APPLICATIONS
`This application is a continuation in part of u.S. Patent
`Application Serial No. 08/819,979, filed March 13, 1997, entitled
`"Method and Apparatus for Improved Fiber Optic Light Management,"
`and is related to U.S. Patent Application Serial Nos. 08/561,484, entitled
`"Optical Fiber with Enhanced Light Collection and Illumination and
`Having Highly Controlled Emission and Acceptance Patterns," filed
`November 20, 1995, 09/267,258, entitled "Method and Apparatus for
`Filtering an Optical Fiber" filed March 12, 1999, and 09/280,413, entitled
`"Optical Filtering Device," filed March 29, 1999, and U.S. Provisional
`20 Application Serial Nos. 601013,341, entitled "Fiber Optic Interface with
`Manipulated Delivery and Reception Sensitivities, fI filed March 13, 1996,
`60/036,504, entitled "Improved Fiber Optic Probe Assembly," filed
`January 28, 1997, and 60/038,395, entitled "Improved Filtering of Optical
`Fibers and Other Related Devices," filed February 14, 1997.
`
`25
`
`BACKGROUND OF THE INVENTION
`Optical assemblies including waveguides in recent years
`have been recognized as offering a high potential for solving problems in
`a number of commercial applications including telecommunications and
`30 medical diagnostics. Optical fiber assemblies are well known in
`telecommunications and have been found to be especially useful in
`analyzing materials by employing various types of light-scattering
`spectroscopy. Optical filters have been found to be useful in such
`applications. In telecommunications typical uses include bandpass filters
`in wavelength-division multiplexing and as noise blocking filters for
`optical amplifiers.
`
`35
`
`7
`
`Page 8
`
`

`
`5
`
`10
`
`15
`
`2
`The term "waveguide" is used herein to refer to an optical
`structure having the ability to transmit light in a bound propagation mode
`along a path parallel to its axis, and to contain the energy within or
`adjacent to its surface. In many optical applications it is desirable to filter
`light that is propagating within a waveguide, perhaps an optical fiber, in
`order to eliminate or redirect light of certain wavelengths or to pass only
`light of certain wavelengths.
`Many types of filters, including interference filters, are
`commonly used for this filtering. However, there are a number of
`difficulties associated with the use of many types of filters, including
`interference filters. First, in some applications the power density of light
`propagating within a waveguide may be unacceptably high for the filter,
`having detrimental effects that may include damage to the filter material
`or reduced filter performance.
`Also, filters are typically employed by means of bulky,
`multiple-optical-element assemblies inserted between waveguides, which
`produces a variety of detrimental effects. Separate optical elements can
`be difficult to align in an assembly and it can be difficult to maintain the
`alignment in operation as well. Each element often must be separately
`20 mounted with great precision and the alignment maintained. Also, an
`increase in the number of pieces in an optical assembly tends to reduce
`the robustness of the assembly; the components may be jarred out of
`alignment or may break. In addition, interfaces between optical elements
`often result in significant signal losses and performance deterioration,
`especially when an air gap is present in the interfaces. The materials of
`which the additional elements are composed may also introduce
`fluorescence or other undesirable optical interference into the assembly.
`The size of filtering assemblies is often a problem as well.
`Not only can it be difficult to manufacture a filter on a small surface area,
`but also filtering assemblies usually contain bulky light-collimating,
`alignment and mounting components in addition to the filtering element.
`However, space is often at a premium in optical assemblies. In addition,
`the filtering characteristics of interference filters change depending upon
`the angle at which light is incident on the filter, and interference filters
`are generally designed for the filtration of normally incident light.
`
`25
`
`30
`
`35
`
`Page 9
`
`

`
`3
`High performance filters have shown particular promise in
`many applications as described in Applicants' co-pending U.S. Patent
`Application Serial Nos. 08/819,979 and 09/267,258. There is an ongoing
`demand for assemblies in these and other industrial and medical
`applications that have less noise. In telecommunications the demand for
`more useable bandwidth is growing at an incredible rate. That
`telecommunications demand and the recognized need for more effective
`medical and environmental diagnostic tools (for example those described
`in the referenced U.S. Patent Application Serial No. 08/819,979) are
`resulting in the need for assemblies having improved signal to noise ratio.
`
`5
`
`10
`
`15
`
`20
`
`SUMMARY OF THE INVENTION
`This invention provides a surprisingly effective optical noise
`reduction in optical assemblies by controlling or limiting unwanted
`photon entrance, reflection, departure or appearance in or from the
`assembly. Applicants have found such unwanted photons passing
`through areas that had not been recognized or had been vastly
`underestimated as photon passageways potentially creating significant
`problems. Applicants have further found the optical performance loss
`because of these areas to present special, technology limiting problems in
`applications benefiting from high performance filters. More specifically,
`applicants have found that penetration of unwanted photons especially in
`areas along periphery of the filter layers, even very thin filter layers, can
`cause significant noise or effective signal erosion. This is especially true
`25 when optical transmission purity/high optical performance is essential.
`That unwanted photon penetration occurs not only through edge surfaces
`but also through face surfaces and edge junctures. The edge juncture is
`where the filter edge surface joins a filter face surface or a filter face
`surface joins another face, for example, of a waveguide, including an
`optical fiber. Problematic optical noise can occur through the filter face
`itself if, for example, some areas of the filter or the waveguide to which it
`is optically connected have differing transmission characteristics or
`demands. In accordance with this invention improvements are obtained
`by selectively covering with a material opaque to the unwanted photons
`those areas that would otherwise allow the unwanted penetrations.
`Assemblies according to one embodiment of the invention when used to
`
`30
`
`35
`
`9
`
`Page 10
`
`

`
`4
`cover such junctures can effectively be utilized as universal adapters for
`connecting fibers to one another or to optical devices for specific
`applications, for example, in chemical analysis and or communication
`facilitating devices. A fiber identification mechanism assures proper fiber
`5 matching and alignment.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`Fig. 1 is a perspective of an optical assembly end portion
`illustrating a masked, filtered fiber end.
`Fig. 2 is a cross sectional magnified view of an optical
`assembly in accordance with Fig. 1 with exaggerated fiber core, filter,
`and mask thickness dimensions.
`Fig. 3 is an end view of an optical assembly illustrating a
`mask having a hexagonal exterior profile and a circular aperture.
`Fig. 4 is a distorted perspective of an uncompleted optical
`assembly end portion illustrating a mask precursor having a hexagonal
`profile.
`
`Fig. 5 is an end view of a cluster of uncompleted optical
`assemblies end portions.
`Fig. 6 is a perspective of two optical assemblies with masks
`placed in mask end near mask end configuration illustrating mating
`orientation.
`
`Fig. 7 is a perspective of two optical assemblies in
`accordance with Fig. 3 in mask end to mask end, mating connection.
`Fig. 8 is a cross sectional view illustrating two optical
`assemblies each having beveled end faces with mask end near mask end
`configuration illustrating mating orientation, with exaggerated fiber core,
`filter, and mask thickness dimensions.
`Fig. 9 is a cross sectional view illustrating two optical
`assemblies oriented for end to end splice using a connection device mated
`to the masked assembly ends.
`Fig. lOis a cross sectional view illustrating two optical
`assemblies oriented for end to end splice using a connection device
`having a fluid entry/evacuation port.
`Fig. 11 includes I1a which is an end view of a splice
`connection device as in Fig. 10 and including a channel for aligning the
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`/()
`
`Page 11
`
`

`
`•
`
`5
`fiber end faces, and lIb which is a blow-up of the channel and its
`surrounds.
`
`DETAILED DESCRIPTION
`A preferred embodiment of the present invention is
`illustrated in Fig. 1 and Fig. 2.
`In Fig. 1 the end of an elongated
`waveguide, in the illustration an optical fiber 11, is shown having at its
`end mask 12. Mask 12 partially covers the filter end face 13 at the end
`face periphery 14. Mask 12 is opaque to at least some wavelengths of
`light. Accordingly, light of the opacity wavelengths do not penetrate
`mask 12 thereby eliminating unwanted optical noise that would result
`from such light penetration of the mask covered areas. Such optical noise
`is particularly problematic in applications requiring high performance, for
`example, in high bandwidth telecommunications, and those applications
`requiring the ability to differentiate between ordinarily small signal
`differences, such as in Raman spectroscopy. Applicants' co-pending U.S.
`Patent Application Serial No. 09/267,258 describes high performance
`filters that are an important factor in enabling the user to get to new
`performance levels. For the foreseeable future there is a conspicuous
`need for ever increasingly higher performance levels. Applicants have
`found the apparently extreme measures according to this invention to
`enable performance levels at which the otherwise tolerable noise is
`problematic. In accordance with a preferred embodiment of the present
`invention high performance filters combined with masking eliminates
`significant sources of unwanted light penetration.
`U.S. Patent Application Serial No. 08/819,979 referenced
`above describes filter performance requirements for demanding
`applications, such as Raman spectroscopy. These requirements include:
`a) high throughput in transmission wavelength region; b) high-attenuation
`(dense) blocking in rejection wavelength regions; c) steep transition
`between wavelength regions of rejection and transmission; d)
`environmental stability; e) low ripple in passage regions, f) minimal
`sensitivity to temperature variation; g) no performance fluctuation with
`ambient humidity or chemicals; h) the ability to withstand high, and
`rapidly changing, temperatures present in sterilization processes and
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`II
`
`Page 12
`
`

`
`6
`industrial processes; i) physical toughness; and j) tenacious adhesion
`between filter and substrate.
`These desirable filter performance properties are achieved in
`high performance filters, thin-film filters having a large number of
`alternating highllow refractive indices, stacked layers deposited on a
`substrate. Between 20 and 150 layers are usually required depending on
`such factors as: 1) the performance required for the end use; 2) the
`refractive index differential between materials in adjacent filter layers; 3)
`the consistency and purity of the filter layer; and 4) the sophistication of
`the filter design process. And, the layers must be free from defects and
`voids such that the material characteristics of the layer approaches that of
`a bulk solid and the packing factor of the layer approaches 100%.
`Achieving high-density packing requires the molecules depositing onto
`the substrate to be highly energetic. During the layer deposition process,
`this energy prevents the forming layer from orienting itself into columnar
`or similar structures that are riddled with voids. While the depositing
`layers are predisposed to forming the imperfect structures, the high
`energy forces pack the molecules (or atoms) into any voids or pinholes
`which may exist.
`Even though the techniques described in U.S. Provisional
`Application Serial No. 60/038,395 provide an extremely attractive means
`of filtering optical fibers, the present invention provides further and now
`recognizable signal quality improvements. The present invention has
`particular advantages for instrumentation applications, such as Raman,
`fluorescence, and other spectroscopic analyses. They are also devised for
`wavelength division multiplexing, telecommunications, general fiber
`optic sensor usage, photonic computing, photonic amplifiers, pump
`blocking, fiber-integral active devices such as fiber-coupled (pigtailed)
`lasers and lasers utilizing the fiber as the lasing cavity.
`In one embodiment of the present invention, a thin-film
`interference filter is applied to a fiber end face. The fiber core may have
`an essentially uniform cross section. Alternatively, the fiber, monomode
`or multimode, may be up tapered so that the cross section of the core is
`enlarged at the filter end face and filtered light is angularly redirected or
`collimated. The filter has a packing density of at least 95%, but preferably
`greater than 99%. A fiber with an integral, masked filter is utilized for
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`12.
`
`Page 13
`
`

`
`7
`instrumentation/sensing applications generally and
`analytical
`spectroscopy more specifically showing improvement even over
`applicants' previous advanced probe systems. The coating of the filters
`on the