(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0097956 A1
`(43) Pub. Date:
`Jul. 25, 2002
`Kikuchi et al.
`
`US 20020097956A1
`
`(54) FIBER COLLIMATOR ARRAY
`
`Publication Classi?cation
`
`(76) Inventors: Juro Kikuchi, KakegaWa-City (JP);
`Yasuyuki Mizushima, KakegaWa-City
`(JP); Hiroki Takahashi, Fukuroi City
`(JP); Yoshiaki Takeuchi, ShiZuoka-shi
`(JP)
`
`Correspondence Address:
`CORNING INCORPORATED
`SP-TI-3-1
`CORNING, NY 14831
`
`(21) Appl. No.:
`
`09/767,255
`
`(22) Filed:
`
`Jan. 22, 2001
`
`........ .. G02B 6/32
`(51) Im. c1? .
`(52) Us. 01. ............................................... ..3s5/33; 385/34
`
`ABSTRACT
`(57)
`An optical ?ber collimator array includes an optical ?ber
`array block and a rnicrolens array substrate. The optical ?ber
`array block includes an angled surface and is con?gured to
`receive and retain a plurality of individual optical ?bers,
`Which carry optical signals. The rnicrolens array substrate
`includes a plurality of rnicrolenses integrated along a micro
`lens surface and a sloped surface opposite the rnicrolens
`surface. The rnicrolens surface is coupled to the angled
`surface such that the optical signals from the individual
`optical ?bers are each collirnated by a different one of the
`integrated rnicrolenses.
`
`116
`
`100
`
`108 /
`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-1
`
`

`

`Patent Application Publication
`
`Jul. 25, 2002 Sheet 1 0f 5
`
`US 2002/0097956 A1
`
`116
`
`136
`
`120
`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-2
`
`

`

`Patent Application Publication
`
`Jul. 25, 2002 Sheet 2 0f 5
`
`US 2002/0097956 A1
`
`200
`
`102
`
`110A
`
`1108
`
`201. K20;
`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-3
`
`

`

`Patent Application Publication
`
`Jul. 25, 2002 Sheet 3 0f 5
`
`US 2002/0097956 A1
`
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`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-4
`
`

`

`Patent Application Publication
`
`Jul. 25, 2002 Sheet 4 0f 5
`
`US 2002/0097956 A1
`
`602
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`Petitioner Ciena Corp. et al.
`Exhibit 1040-5
`
`

`

`Patent Application Publication
`
`Jul. 25, 2002 Sheet 5 0f 5
`
`US 2002/0097956 A1
`
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`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-6
`
`

`

`US 2002/0097956 A1
`
`Jul. 25, 2002
`
`FIBER COLLIMATOR ARRAY
`
`BACKGROUND OF THE INVENTION
`
`[0001] 1. Field of the Invention
`
`[0002] The present invention is directed to a ?ber colli
`mator array and more speci?cally to a ?ber collimator array
`for use in an optical transmission system and/or an optical
`sensor system.
`[0003] 2. Technical Background
`[0004] Collimation is a process by Which divergent beams
`of radiation or particles (e.g., light rays) are converted into
`parallel beams. Laser diode (LD) collimating lenses are
`commonly used in laser beam printers, bar code scanners
`and sensors. In addition, ?ber collimators are Widely used in
`a variety of optical applications (e.g., optical ?lters). Due to
`the recent increase in demand for ?ber collimators, to be
`used With Wave division multiplexed (WDM) systems,
`reducing the ?ber collimator cost has become increasingly
`important.
`[0005] HoWever, commercially available ?ber collimator
`arrays have typically implemented separate lenses, Which
`has increased the cost of the array. For eXample, one
`commercially available collimator array has utiliZed a
`V-groove array substrate With individually aligned gradient
`indeX (GRIN) microlenses and ?bers in each V-groove.
`These GRIN microlenses have generally been produced by
`an ion-exchange process and normally provide high cou
`pling efficiency and have been utiliZed as collimators for
`laser beam printers, bar code scanners, optical isolators,
`circulators and digital versatile disc (DVD) players, as Well
`as miniature objective lenses for medical/industrial endo
`scopes.
`
`[0006] Planar microlens arrays (PMLAs) are tWo-dimen
`sional GRIN-type lens arrays that integrate ion-exchange
`technology and photolithography. By diffusing ions through
`a photolithographic mask into a glass substrate, numerous
`microscopic lenses can be formed in various siZes and
`patterns. Commercially available PMLAs are available With
`sWelled lens surfaces, Which tend to increase coupling
`ef?ciencies in transceiver applications, or With ?at surfaces,
`Which typically simplify collimation With ?ber arrays.
`PMLAs have been used in liquid crystal projectors, three
`dimensional data processing and tWo dimensional laser
`diode (LD) coupling to ?bers. Other manufactures, such as
`Rochester Photonics Corp., have produced aspheric colli
`mating microlenses that are intended to replace GRIN-type
`microlenses in collimating applications.
`[0007] HoWever, the effectiveness of GRIN-type PMLAs
`and collimating arrays incorporating aspheric collimating
`microlenses are highly dependent on the con?guration of the
`?ber collimator array. As such, it is important to con?gure
`the ?ber collimator array to reduce insertion loss and inter
`nal re?ections.
`
`SUMMARY OF THE INVENTION
`
`[0008] An embodiment of the present invention is directed
`to an optical ?ber collimator array that includes an optical
`?ber array block and a microlens array substrate. The optical
`?ber array block includes an angled surface and is con?g
`ured to receive and retain a plurality of individual optical
`
`?bers, Which carry optical signals. The microlens array
`substrate includes a plurality of microlenses integrated along
`a microlens surface and a sloped surface opposite the
`microlens surface. The microlens surface is coupled to the
`angled surface such that the optical signals from the indi
`vidual optical ?bers are each collimated by a different one of
`the integrated microlenses.
`[0009] According to another embodiment of the present
`invention, an optical ?ber collimator array includes an
`optical ?ber array block, a microlens array substrate and an
`indeX-matched spacer. The optical ?ber array block is con
`?gured to receive and retain a plurality of individual optical
`?bers, Which carry optical signals. The microlens array
`substrate includes a plurality of microlenses integrated along
`a microlens surface and the indeX-matched spacer couples
`the optical ?ber array block to the microlens array substrate.
`[0010] Additional features and advantages of the inven
`tion Will be set forth in the detailed description Which
`folloWs and Will be apparent to those skilled in the art from
`the description or recogniZed by practicing the invention as
`described in the description Which folloWs together With the
`claims and appended draWings.
`[0011] It is to be understood that the foregoing description
`is exemplary of the invention only and is intended to provide
`an overvieW for the understanding of the nature and char
`acter of the invention as it is de?ned by the claims. The
`accompanying draWings are included to provide a further
`understanding of the invention and are incorporated and
`constitute part of this speci?cation. The draWings illustrate
`various features and embodiments of the invention Which,
`together With their description, serve to eXplain the princi
`pals and operation of the invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0012] FIG. 1A is a cross-sectional vieW of an optical
`?ber collimator array, according to an embodiment of the
`present invention;
`[0013] FIG. 1B is a top plan vieW of the array of FIG. 1A;
`
`[0014] FIG. 1C is a cross-sectional vieW of an optical
`?ber collimator array, according to another embodiment of
`the present invention;
`[0015] FIG. 2 is a cross-sectional vieW of the collimator
`array of FIG. 1A that additionally includes an indeX
`matched angled spacer;
`
`[0016] FIG. 3 is a cross-sectional vieW of another embodi
`ment of an optical ?ber collimator array of the present
`invention;
`[0017] FIG. 4 is a cross-sectional vieW of yet another
`embodiment of an optical ?ber collimator array of the
`present invention;
`[0018] FIG. 5 is a cross-sectional vieW of still another
`embodiment of an optical ?ber collimator array of the
`present invention;
`[0019] FIG. 6 is a cross-sectional vieW of a different
`embodiment of an optical ?ber collimator array of the
`present invention;
`[0020] FIGS. 7A-7C are cross-sectional vieWs of the opti
`cal ?ber collimator array of FIG. 6 during assembly;
`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-7
`
`

`

`US 2002/0097956 A1
`
`Jul. 25, 2002
`
`[0021] FIG. 8 is a cross-sectional vieW of an optical ?ber
`collimator array that utilizes a spacer With a hole;
`
`[0022] FIGS. 9A-9B are cross-sectional, taken through
`sectional line IXA, and end elevational vieWs, respectively,
`of the spacer of FIG. 8; and
`
`[0023] FIG. 10 is a cross-sectional vieW of a microlens
`array substrate With a non-?at lens surface.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT(S)
`[0024] The present invention is directed to an optical ?ber
`collimator array that includes a microlens array substrate
`and an optical ?ber array block that are con?gured to reduce
`insertion loss and to reduce internal re?ections. Each micro
`lens is preferably a graded-index (GRIN) lens, an aspheric
`lens or a Fresnel lens. A GRIN lens has a refractive indeX
`that decreases With distance from its optical aXis (i.e.,
`center). This causes light rays to travel in sinusoidal paths,
`With the length of one complete cycle being knoWn as the
`pitch of the lens. Commercially available ?ber array blocks
`typically have a pitch of either tWo-hundred ?fty microns or
`one-hundred tWenty-seven microns. The pitch of the ?ber
`block limits the microlens diameter, Which may limit the
`coupling ef?ciency of the lens since the mode?eld diameter
`of the optical poWer (of the optical signal) in the microlens
`plane is limited by the microlens diameter.
`
`[0025] To reduce coupling loss to less than 0.01 dB, the
`mode?eld diameter should typically be less than half the
`effective microlens diameter. As such, When a GRIN lens
`With a pitch of tWo-hundred ?fty microns is used, the
`mode?eld diameter should be less than one-hundred ten
`microns since the effective lens diameter is typically less
`than ninety percent of the physical lens diameter. While a
`larger collimated beam diameter is preferable in order to get
`higher coupling ef?ciency, at typical Working distances over
`a feW millimeters, in practical use, the mode?eld diameter
`limits the diameter of the collimated optical beam. As such,
`the dimensions of the ?ber collimator array, including the
`optical ?ber array block and the microlens array substrate,
`are limited. Preferably, the mode?eld diameter of an optical
`signal on a microlens plane should be set close to one
`hundred ten microns.
`
`[0026] Turning to FIGS. 1A-1B, a cross-sectional and top
`plan vieW, respectively, of an optical ?ber collimator array
`100, according to an embodiment of the present invention,
`are depicted. The array 100 retains a plurality of optical
`?bers 108 Within an optical ?ber array block 102, Which
`includes a plurality of channels for receiving the ?bers 108,
`Which are preferably retained Within the block 102 With an
`adhesive. A planar graded-index (GRIN) microlens array
`substrate 104 includes a plurality of GRIN microlenses 106,
`Which are spaced such that each microlens 106 receives an
`optical signal from one of the optical ?bers 108. The ?ber
`array block 102 includes an angled surface 112, opposite the
`end of the ?ber block 102 in Which the ?bers 108 enter the
`?ber block 102. The microlens array substrate 104 includes
`a sloped surface 114 opposite the microlenses 106 (i.e., a
`microlens surface 116). The angled surface 112, of the ?ber
`array block 102, and the sloped surface 114, of the microlens
`array substrate 104, are designed to reduce re?ection at the
`boundary betWeen the block 102 and the substrate 104.
`Preferably, the microlens array substrate 104 is made of a
`
`glass (e.g., PYREX®) and one end of the ?bers 108 are ?Xed
`?ush With and have substantially the same angle as the
`angled surface 112.
`
`[0027] The block 102 and the substrate 104 are preferably
`joined to each other through the use of a commercially
`available indeX-matched optical adhesive 110A, preferably
`using an active alignment tool. Suitable UV-cured indeX
`matched optical adhesives are commercially available from
`NTT Advanced Technology Corporation (e.g., product num
`ber 9389 is suitable for a refractive indeX of 1.448). If
`desired, a conventional anti-re?ection
`coating or coat
`ings 110B may also be added to the interface betWeen the
`block 102 and the substrate 104. The angles (i.e., the angled
`surface 112 and the sloped surface 114) are preferably eight
`degrees from perpendicular to the optical aXes of the ?bers
`108, Which, in theory, should provide at least a 60 dB
`attenuation of any re?ected signal. Re?ections can also be
`further reduced at the microlens surface 116 by applying an
`AR coating (or a multi-layer AR coating) 117 to the surface
`116. HoWever, utiliZing an AR coating 117 With the micro
`lens array substrate 104, of FIG. 1A, has been shoWn to only
`reduce re?ections to about one-tenth of one percent of the
`transmitted signal (i.e., about 30 dB). While a return loss of
`30 dB is acceptable in many applications, such a return loss
`is generally not acceptable in some practical applications,
`such as ?ber ampli?er modules.
`
`[0028] FIG. 1C illustrates a cross-sectional vieW of an
`optical ?ber collimator array 120, according to another
`embodiment of the present invention, that retains a plurality
`of optical ?bers 128 Within an optical ?ber array block 122.
`The ?ber collimator array 120 can typically achieve a return
`loss greater than 60 dB When AR coatings are utiliZed. An
`aspheric microlens array substrate 124 includes a plurality of
`aspheric microlenses 126, Which are spaced such that each
`microlens 126 receives an optical signal from one of the
`optical ?bers 128. The ?ber array block 122 includes an
`angled surface 132, opposite the end of the ?ber block 122
`in Which the ?bers 128 enter the block 122. The microlens
`array substrate 124 includes a sloped surface 134 opposite
`the microlenses 126 (i.e., a microlens surface 136). The
`angled surface 132 of the ?ber array block 122 and the
`sloped surface 134 of the microlens array substrate 124 are
`designed to reduce re?ection at the boundary betWeen the
`block 122 and the substrate 124. Preferably, the microlens
`array substrate 124 is also made of a glass (e.g., PYREX®).
`
`[0029] The block 122 and the substrate 124 are preferably
`attached to each other through the use of an indeX-matched
`optical adhesive 130A, preferably using an active alignment
`tool, and may included an AR coating (or coatings) 130B at
`the interface. Similar to the collimator array 100 of FIG. 1A,
`the angles of the block 122 and substrate 124 are preferably
`eight degrees from perpendicular to the optical aXes of the
`?bers 128. Re?ections can also be further reduced by
`applying an anti-re?ection
`coating 127 to the micro
`lens surface 136.
`
`[0030] The re?ections of the array 100 can be further
`reduced through the implementation of an indeX-matched
`angled spacer. As shoWn in FIG. 2, an optical ?ber colli
`mator array 200 includes an indeX-matched angled spacer
`202, Which reduces re?ections at the microlens surface 116
`of the GRIN microlens array substrate 104. Preferably, the
`angled spacer 202 is attached to the microlens surface 116,
`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-8
`
`

`

`US 2002/0097956 A1
`
`Jul. 25, 2002
`
`of the array substrate 104, With an indeX-matched optical
`adhesive 204, after active alignment of the microlens array
`104 With the ?ber array block 102. The refractive index of
`the spacer 202 is preferably selected to be substantially the
`same as that of the microlens 106. When another device,
`such as an optical ?lter, is not directly connected to the
`spacer 202, a slanted surface 206 of the spacer 202, opposite
`that attached to the microlens array substrate 104, is also
`preferably coated With an AR coating 205 to further reduce
`re?ection. Typically, a slant of less than about one degree is
`enough for the spacer 202 to adequately attenuate any
`re?ections (i.e., at least a 60 dB loss).
`
`[0031] In the ?ber collimator arrays 100, 120 and 200 of
`FIGS. 1A-1C and 2, respectively, the optical beam aXis
`generally slightly slants at the boundary of the ?ber array
`block and the microlens array substrate When the refractive
`indeX of the materials (i.e., the ?ber core and substrate) differ
`from each other. As such, the coupling efficiency of an
`optical system, that includes such a collimator array, is
`slightly degraded. This is because the mode?eld center of
`optical poWer in the microlens plane slightly shifts from the
`center of the microlens. This slight shift adversely affects the
`coupling ef?ciency, since the Whole optical beam mode?eld
`is very close to the effective microlens area.
`
`[0032] Moving to FIG. 3, a cross-sectional vieW of an
`optical ?ber collimator array 300, according to yet another
`embodiment of the present invention, is depicted. In general,
`the ?ber collimator array 300 provides a higher coupling
`ef?ciency as compared to the ?ber collimator arrays of
`FIGS. 1A-1C and 2. As shoWn in FIG. 3, an optical ?ber
`array block 302 retains a plurality of optical ?bers 308. An
`angled surface 312 of the ?ber array block 302 is coupled
`(preferably, With an indeX-matched optical adhesive 310A)
`to a sloped surface 314 of a GRIN microlens array substrate
`304. If desired, an AR coating 310B may also be provided
`at the interface betWeen the block 302 and the substrate 304.
`The sloped surface 314 of the microlens array substrate 304
`is preferably formed at an angle that is different from the
`angled surface 312 of the ?ber array block 302.
`
`[0033] The center angle of the sloped surface 314 of the
`microlens array substrate 304 is, preferably, adjusted to be a
`someWhat different value from 8+/—0.5 degrees, depending
`on the difference of the refractive indeX of the core of ?bers
`308 and the microlens array substrate 304. If the refractive
`indeX of the microlens array substrate 304 is 1.66, for
`eXample, an appropriate center angle is about 83 degrees.
`The microlens array substrate 304 is adjusted in relation to
`the block 302 such that the optical beam aXis coincides With
`the optical aXis (i.e., center) of each of the microlenses 306.
`In this con?guration, the re?ection from the microlens
`surface 316 can be reduced by using an indeX-matched
`optical adhesive 318 and by attaching an indeX-matched
`angled spacer 332 that includes an AR coating 336 on its
`slanted surface 334. A back surface 330 of the spacer 332
`does not require an AR coating, since the indeX of the spacer
`332 preferably matches that of the microlens 306. A similar
`con?guration can also be utiliZed in conjunction With an
`aspheric microlens array substrate, such as that of FIG. 1C.
`
`[0034] A preferred material for the optical ?ber array
`blocks of FIGS. 1A-1C, 2 and 3 is PYREX® or silicon glass,
`Which is selected to match the coef?cient of thermal eXpan
`sion (CTE) of the microlens array substrate material. That is,
`
`if the microlens array substrate is made of silica glass, the
`same material (silica glass) Would be a preferred choice for
`the material of the ?ber array block.
`
`[0035] FIG. 4 depicts a cross-sectional vieW of an optical
`?ber collimator array 400, according to still another embodi
`ment of the present invention. In general, the ?ber collimator
`array 400 provides an alternative to the ?ber collimator array
`300 that is particularly useful When alignment of the block
`302 and substrate 304 is burdensome or When the thickness
`of the substrate 304 cannot be easily controlled to Within
`about ten microns. As shoWn in FIG. 4, a ?ber array block
`402 retains a plurality of optical ?bers 408. An angled
`surface 412 of the ?ber array block 402 is coupled (e.g., With
`an indeX-matched optical adhesive 410A) to a slanted sur
`face 434 of an indeX-matched angled spacer 432. If desired,
`an AR coating 410B may also be provided at the interface
`betWeen the block 402 and the spacer 432. The spacer 432
`includes a back surface 430 that is opposite the slanted
`surface 434. The slanted surface 434 of the spacer 432 is
`preferably formed at an angle that is different from the
`angled surface 412, of the ?ber array block 402. A back
`surface 414 of the microlens array substrate 404 is then
`adjusted in relation to the back surface 430, of the spacer
`432, such that each optical beam aXis coincides With an
`optical aXis of one of the microlenses 406. When proper
`alignment is achieved betWeen the substrate 404 and the
`spacer 432, the tWo are coupled together, preferably, With an
`indeX-matched optical adhesive 420. In this con?guration,
`the re?ection from the microlens surface 416, of the micro
`lens array substrate 404, can be reduced by adding an AR
`coating 418 to the surface 416.
`
`[0036] FIG. 5 illustrates a cross-sectional vieW of an
`optical ?ber collimator array 500, according to a different
`embodiment of the present invention. In the embodiment of
`FIG. 5, all surfaces of the array 500, that an optical beam
`crosses, are substantially perpendicular, at least initially, to
`the optical aXis of each microlens 506. A ?ber array block
`502 retains a plurality of optical ?bers 508 and includes a
`?rst surface 512 that is coupled (e.g., With an indeX-matched
`optical adhesive 511) to a ?rst surface 534 of an indeX
`matched spacer 532. The spacer 532 includes a second
`surface 530 that is opposite the ?rst surface 534. Amicrolens
`surface 516 of the microlens array substrate 504 is then
`adjusted in relation to the second surface 530 such that the
`optical beams coincide With the optical aXis of each of the
`microlenses 506.
`
`[0037] When proper alignment is achieved betWeen the
`substrate 504 and the spacer 532, they are coupled together,
`preferably, With an indeX-matched optical adhesive 513A. If
`desired, an AR coating 513B may also be provided at the
`interface betWeen the spacer 532 and the substrate 504. The
`refractive indeX of the spacer 532 is preferably matched to
`the refractive indeX of the core of the optical ?ber 508. A
`re?ection reduction of approximately 20 dB is achievable
`due to the spacing, dictated by the Width (dependent on the
`focal length of the microlenses 506) of the spacer 532,
`betWeen the ends of the optical ?bers 508 and the micro
`lenses 506. This is because the mode?eld of an optical beam
`from each of the ?bers 508 diverge until they reach one of
`the microlenses 506. In this con?guration, the re?ection
`from the microlens surface 516 of the microlens array
`substrate 504 can be reduced by adding anAR coating 513B
`to the interface betWeen the spacer 532 and the substrate
`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-9
`
`

`

`US 2002/0097956 A1
`
`Jul. 25, 2002
`
`504. Further, the re?ection from a back surface 514 of the
`array 504, opposite the microlens surface 516, can be
`reduced by adding anAR coating 515 to the surface 514 and
`further reduced by angle polishing the surface 514.
`[0038] FIG. 6 illustrates a cross-sectional vieW of an
`optical ?ber collimator array 600, according to another
`embodiment of the present invention. An optical ?ber array
`block 602 retains a plurality of optical ?bers 608 and
`includes an angled surface 612 that is coupled (e.g., With an
`indeX-matched optical adhesive 611A) to a slanted surface
`634 of an indeX-matched spacer 632. If desired, an AR
`coating 611B may also be provided at the interface betWeen
`the spacer 632 and the block 602. The spacer 632 includes
`a back surface 630, opposite the angled surface 634, that is
`generally perpendicular to the optical aXes of microlens 606.
`A microlens surface 616, of the microlens array substrate
`604, is then adjusted in relation to the surface 630, of the
`spacer 632, such that the optical beams coincide With the
`optical beam aXis of each of the microlenses 606.
`[0039] When proper alignment is achieved betWeen the
`substrate 604 and the spacer 632, they are coupled together,
`preferably, With an indeX-matched optical adhesive 613. The
`refractive indeX of the spacer 632 is, preferably, matched to
`the refractive indeX of the microlens 606. Further, any
`re?ection from the surface 614 of the array 604, opposite the
`microlens surface 616, can generally be reduced by angle
`polishing the surface 614 and normally further reduced by
`adding an AR coating 615 to the surface 614.
`[0040] FIGS. 7A-7C illustrate a simpli?ed procedure for
`fabricating the ?ber collimator array 600 of FIG. 6. As
`shoWn in FIG. 7A, initially, the slanted surface 634 of the
`indeX-matched spacer 632 is attached to the angled surface
`612 of the optical ?ber array block 602. The effective
`thickness (i.e., the length of the optical path in the spacer
`632) is passively adjusted using an alignment tool. Next, as
`is shoWn in FIG. 7B, the microlens surface 616 of the
`microlens array substrate 604 is actively aligned, preferably
`by using a mirror, With the back surface 630 of the spacer
`632. When proper alignment is achieved, the spacer 632 and
`microlens array substrate 604 are ?Xed in relation to one
`another With an indeX-matched optical adhesive 613.
`Finally, as shoWn in FIG. 7C, the back surface 614 of the
`substrate 604 is angle polished and AR coated 615, if
`required for the application.
`[0041] FIG. 8 depicts a cross-sectional vieW of a ?ber
`collimator array 800, according to yet another embodiment
`of the present invention. A ?ber array block 802 retains a
`plurality of optical ?bers 808 and includes an angled surface
`812. A slanted surface 834 of a spacer 832 is adjusted With
`respect to the angled surface 812 until the optical beams
`provided through the optical ?bers 808 are perpendicular to
`a back surface 830 of the spacer 832. The block 802 and the
`spacer 832 are then ?Xed With an adhesive 811B. If desired,
`an AR coating 811A may also be utiliZed on the surface 812
`of the block 802 to reduce re?ections. A microlens surface
`816 of the microlens array substrate 804 is then adjusted in
`relation to the surface 830 of the spacer 832 such that the
`optical beams coincide With the optical beam aXis of each of
`the microlenses 806. Preferably, the spacer 832 has a hole
`809, Which alloWs the optical beams to pass from the ends
`of the optical ?bers 808, through air, to the microlens 806.
`[0042] When proper alignment is achieved betWeen the
`substrate 804 and the spacer 832, they are coupled together,
`
`With an adhesive 813A. HoWever, in this embodiment an
`indeX-matched optical adhesive is not required since the
`optical beams travel through air. In this con?guration, any
`re?ection from the microlens surface 816, of the microlens
`array 804, can also typically be reduced by adding an AR
`coating 813B to the surface 816. Re?ections from the
`surface 814, opposite the microlens surface 816, can also
`typically be reduced by angle polishing the surface 814 and
`by adding an AR coating 815 to the surface 814, if required
`for the application.
`
`[0043] When a spacer is located betWeen the ?ber array
`block and the microlens array substrate, as shoWn in FIGS.
`4, 5, 6, 7A-7C and 8, it is desirable to CTE match the spacer
`With the ?ber array block and the microlens array substrate
`for high property stability over a Wide temperature range.
`Preferably, the spacer material is a glass material that is
`transparent in the applied Wavelength range, eXcept in the
`case of FIG. 8, the spacer material does not have to be
`transparent in the applied Wavelength range. The glass
`material of the angled spacer of FIG. 4 is, preferably,
`selected to match the refractive indeX of the microlens array
`substrate. The glass material of the angled spacer of FIGS.
`2, 3, 6 and 7A-7C is, preferably, selected to match the
`refractive indeX of the microlens.
`
`[0044] A suitable angle for the angled surface of the ?ber
`array blocks of FIGS. 1A-1C, 2, 3, 4, 6, 7A-7C and 8 is
`about 8+/—0.1 degrees. It should be appreciated that the
`angle range is a function of the desired minimum re?ection.
`For eXample, if a center angle of 8.5 degrees is utiliZed, a
`Wider angular range of about +/—0.6 degrees provides an
`acceptable re?ection reduction. An acceptable angle for the
`sloped surface of the microlens array substrate is about
`8+/—0.5 degrees. HoWever, the angle of the sloped surface
`can typically vary someWhat as the position of the microlens
`array substrate to the ?ber array block is adjusted actively in
`the ?ber collimator array fabrication process. In the case of
`the array of FIG. 3, the center angle of the sloped surface is
`preferably adjusted to be a slightly different value from
`8+/—0.5 degrees, depending on the refractive indeX differ
`ence betWeen the core of the ?ber and the microlens array
`substrate. Asimilar angular range of +/—0.5 degrees from the
`center angle is also usually acceptable for the slanted surface
`of the angled spacers of FIGS. 4, 6, 7A-7C and 8. In the case
`of FIGS. 6, 7A-C and 8, the back surface of the microlens
`array substrate is, preferably, angle polished to an angle of
`1+/—0.5 degrees, since a minimum angle of 0.4 degrees
`reduces the re?ectivity such that the collimator array attenu
`ates re?ections by at least about 60 dB. The back surface of
`the indeX-matched angled spacers of FIGS. 2 and 3 are also
`preferably angle polished to an angle of about 1+/—0.5
`degrees for similar reasons.
`
`[0045] FIGS. 9A-9B shoW a cross-sectional vieW and a
`side vieW, respectively, of an eXemplary spacer 832 that can
`be utiliZed in the array of FIG. 8. As previously discussed,
`With respect to FIG. 8, the slanted surface 834 is adjusted
`such that the back surface 830, Which faces the substrate, is
`perpendicular to the optical beams provided by the optical
`?bers 808. FIG. 10 depicts a microlens array 900 With a
`non-?at lens surface 902 that can be utiliZed With many of
`the embodiments, disclosed herein. Further, While only
`linear arrays have been depicted, one of ordinary skill in the
`art Will appreciate that the arrays, disclosed herein, can
`readily be expanded to tWo-dimensional arrays.
`
`Petitioner Ciena Corp. et al.
`Exhibit 1040-10
`
`

`

`US 2002/0097956 A1
`
`Jul. 25, 2002
`
`[0046] In summary, an optical ?ber collimator array has
`been described that includes an optical ?ber array block and
`a microlens array substrate. The optical ?ber array block
`includes an angled surface and is con?gured to receive and
`retain a plurality of individual optical ?bers, Which carry
`optical signals. The microlens array substrate includes a
`plurality of microlenses integrated along a microlens surface
`and a sloped surface opposite the microlens surface. The
`microlens surface is coupled to the angled surface such that
`the optical signals from the individual optical ?bers are each
`collimated by a different one of the integrated microlenses.
`According to another embodiment of the present invention,
`an optical ?ber collimator array includes an optical ?ber
`array block, a microlens array substrate and an indeX
`matched spacer. The optical ?ber array block is con?gured
`to receive and retain a plurality of individual optical ?bers,
`Which carry optical signals. The microlens array substrate
`includes a plurality of microlenses integrated along a micro
`lens surface and the indeX-matched spacer couples the
`optical ?ber array block to the microlens array substrate.
`
`[0047] It Will become apparent to those skilled in the art
`that various modi?cations to the preferred embodiment of
`the invention as described herein can be made Without
`departing from the spirit or scope of the invention as de?ned
`by the appended claims.
`
`The invention claimed is:
`1. An optical ?ber collimator array, comprising:
`
`an optical ?ber array block con?gured to receive and
`retain a plurality of individual optical ?bers Which
`carry optical signals, the optical ?ber array block
`including an angled surface; and
`
`a m