CA2402309A1 - Compression-tuned grating-based optical add/drop multiplexer - Google Patents
Compression-tuned grating-based optical add/drop multiplexer Download PDFInfo
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- CA2402309A1 CA2402309A1 CA002402309A CA2402309A CA2402309A1 CA 2402309 A1 CA2402309 A1 CA 2402309A1 CA 002402309 A CA002402309 A CA 002402309A CA 2402309 A CA2402309 A CA 2402309A CA 2402309 A1 CA2402309 A1 CA 2402309A1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
- G02B6/29316—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide
- G02B6/29317—Light guides of the optical fibre type
- G02B6/29319—With a cascade of diffractive elements or of diffraction operations
- G02B6/2932—With a cascade of diffractive elements or of diffraction operations comprising a directional router, e.g. directional coupler, circulator
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
- G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
- G02B6/02195—Refractive index modulation gratings, e.g. Bragg gratings characterised by means for tuning the grating
- G02B6/022—Refractive index modulation gratings, e.g. Bragg gratings characterised by means for tuning the grating using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
- G02B6/29316—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide
- G02B6/29317—Light guides of the optical fibre type
- G02B6/29322—Diffractive elements of the tunable type
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/2938—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
- G02B6/29382—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM including at least adding or dropping a signal, i.e. passing the majority of signals
- G02B6/29383—Adding and dropping
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/29395—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device configurable, e.g. tunable or reconfigurable
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/29398—Temperature insensitivity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0201—Add-and-drop multiplexing
- H04J14/0202—Arrangements therefor
- H04J14/021—Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
Abstract
A compression-tuned fiber Bragg grating based reconfigurable wavelength add/drop module has a compression force assembly and an all-glass Bragg grating compression unit having gratings spaced along an axis of compression.
The compression force assembly responds to a control electronics signal containing information about a selected wavelength of a channel to be added to or dropped from an optical traffic signal, for providing a compression force applied along the axis of compression. The compression unit responds to the optical traffic signal and the compression force, for providing an all-glass Bragg grating compression unit optical signal having the selected wavelength of the channel to be added to or dropped from the optical traffic signal. The compression unit optical signal may include either the traffic with an added reflected channel(s), or a dropped reflected channel(s). The compression unit is a "dogbone" structure having either a glass tube with an optical fiber fused therein, or a single large diameter waveguide having a core. The core of the optical fiber or waveguide has the gratings spaced therein. The axis of compression is parallel with the longitudinal axis of the dogbone structure.
The compression force assembly responds to a control electronics signal containing information about a selected wavelength of a channel to be added to or dropped from an optical traffic signal, for providing a compression force applied along the axis of compression. The compression unit responds to the optical traffic signal and the compression force, for providing an all-glass Bragg grating compression unit optical signal having the selected wavelength of the channel to be added to or dropped from the optical traffic signal. The compression unit optical signal may include either the traffic with an added reflected channel(s), or a dropped reflected channel(s). The compression unit is a "dogbone" structure having either a glass tube with an optical fiber fused therein, or a single large diameter waveguide having a core. The core of the optical fiber or waveguide has the gratings spaced therein. The axis of compression is parallel with the longitudinal axis of the dogbone structure.
Description
COll2PRESSrON-TUNED GRATINGBASED
OPTICAL ADD/riROP MULTIPLEXEIt Cross References To Related Applications 'S This is a continuation-in-part o.f US Patent Application, Serial No. 09/S
19,220 a:
entitled "Compression-Tmaed Bragg Grating Based Iteconfiguxable wavelength Channel Addl:Drop Multiplexes", :Czled March 6, 2000 {CC-0204), which is hereby incozporated herein by reference in its entirety.
2b3 Technicalh'ield.
The present inventi.an relates to optical add/drop multiplexes devices, and more partioularly, an optical addldrop multiplexes. {O.ADNI] using a. iarge diametex waveguide for dynamically adding and dropping optical signals from a. "~tflM
optical, signal, l'5 Baclrground Art The telecommunications Indus°'.ry is undergoing dramatic changes with, increased competition, relentless bandwidth, demand, and a migration toward a more data-centric network architeatuxe. First generation point-to-point wave division a o multiplex systems have eased the traffio bot~lenecl~ in the backbone portion of a networlc. As a new cross-connect architecture moves the technology closer to ihew subscriber side of the network, operators are challenged to provide services at fh.e opti.aal .layer, calling for more flexible n.etlvorlcs that can switch and reroute wavelengths. This is placing great emphasis and demand for wavelength agile devices, of which compression-tuned grating devices could play a majox xole.
The need to provide services "ju.st in time" by allocation of wavelengths, and .furth.er migration ofthe optical layer from the high-capacity bacltbone portion to the local loop, is driving the transformation of the network toward an all optie~.l nel."~~orlc in which basic network requixem,ents wilt be performed. in the optical Iayer, The optical, naetwork is a natural evolution of point-to-point dense wavelength division multiplaxin.g (D~7trDM) iTansport to a more dynasn.ie, nexible, and intelligent netwvorlting architecture to improve service delivery tuna. The main element of the optical network is the wavelength (channel), which will be provisioned, configured, .s, routed., and managed in the optical domain. Xntell.igent optical networking will be first deployed as an "opaque" network in which periodic optical-electrical convexsi.on will be required to monitor and isolate signal impairments, Longex xange, the optical netwoxlc will evolve to a "transparent" optical network in which a signal is transported from its source to a destination totally within the optical domain.
io A key elean.ent of the emerging optical z~.etvvoxlc is an optical add/drop multiplexes (OADM), An OADM will drop oz add specific wavelength channels without affecting tla.e ilrrough channels, nixed OADMs can simplify the networlc and readily allow cost-effective DWDM migration from simple point-to-point topologies to tzxed mufti-point configyxations. True dynamic OADM, in which reconfiguration r15: i.s done in the optical domain without optical-electrical conversion, vcrould allow dynamically xeconfigurable, mufti-point DWDM optical networks. This dynamically xeeonfigurable mufti-point architecture is slated to be the next major please in network evolution, with true OADM an enabling network element for this arcllitecturo, One known comrnezcially is a fixed all-optical OADM that couples fixed a o optical clia~mel filters, usually fiber Bragg gratings, to passive optical routing and branching components such as couplers and circulators. The fiber Bragg gratings are not tuned to filter different wavelengths.
A tunable gratiog/ei..rculator approach for dynamically reconfigurable OADM
has also been pursued in the prior art by thermal or strain tuning the gzating. These 2s, dynamic or programmable all-optical OADM designs are based on tunable gratings.
But thermal tuniaag is slow and difficult to maintain and control wavelength to the tolerances required in cun~ent DWDM systems that feature sub-manometer channel spacing, Strain tuning approaches, in vYhioh, the fiber grating is mechanically stretched, loave also proved difficult to maintain and control and tune wavelengths due to ~.ber attachment challenges and slight mechanical creep that cause errors anal slippage. The reliability of a fiber. being lteld under tension for extended periods of tithe is questionable and controversial for use in the industry.
Ball, in United States Patent No, 6,020,986, shows an addldrop module haying a. circulator 16, an array of tunable fiber Bragg gratings, a piezoelectric device and a controller, which is incorporated here:tn by reference. strain is applied by coupling the piezoelectric device to each Ether Bxagg grating, and adjusting the current applied to each piezoel.ectri.e device from the controller. The wavelength, o~ the grating trtay be adjusted ("tuned") i.n th.e manometer range for gratings having a wavelength of a.o. about 1540 manometers. However, SaII does not disclose how the piezoelectric device is physi.cal.l,y coupled to the fiber Bragg gratings to apply strain..
See also United States Patent No. 5,579,143, issued to Huber, and United States latent No.
5,748,349, issued to Mizxahi, which disclose OA.DM systems having tenable optical filters, v~rllzch axe incorporated herein by reference.
z5 Moreover, the grating/circulator approach for OADM has emerged as a. viable rztethod over otl.~er OAAM techniques such as optical switches and arrayed vVaveguide devices, which are broadband in nature, Combinations of switches and wavelength.
rttultiplexers achieve wavelength selection but suffer fram other performance problems such as high optical losses and high cost.
ao Despite intense efforts, dynamic OADMs of such types remain elusive due to inherent performance issues, particularly drift and reliability, tlaz~a thermal or tension grating tuning approaches. T, he inadequacy of thermal and tension-based grating tuning methods to control and maintain wavelength to tight tolerances would require some sort of in-line signal diagnostic, such as a wavelengtl monitoring device or s, speci:rttm. aualy~ex, to provide feedbacle and referencing for closed loop control of the grating v~avelengtla, Summary of the Invention fn accordance with an embodiment of the present invention, an optical drop filter includes a compression-tuned optical device, The compression tuned optical device includes an optical waveguide, which has an inner care disposed within an outer cladding and a grating disposed within the inner core. The grating reflectd a fixst reflection wavelength of light baclc along the inner core and propagates the remainirr,ycvaYelengths of light through the grating. The optical waveguide includes a pair of opposing surfaces. The optical waveguide also includes a compressing devzce that compresses tile optical waveguide fox compressing the opposing surfaces towards each other to tttn.e the grating and change th.e reflection wavelength of light reflected baclt along the inner core. The drop f lter also includes an optical directing device for ~.o providing an input optical sig~.ial to the compression-tuned optical device.. The input optical signal has a plurality of optical channels cantered at spaced wavelengths. The compression-tuned optical device removes an optical charnel from the input opti,eal signal.
In accordance wiill another embodiment of the pxesent invezation, an optical add ~rlter includes a compression-tuned optical device, which has an optical rnaveguide, The optical waveg~iide includes an inner core disposed within an outer cladding and a grating disposed within the inner core. The grating reflects a first reflection. wavelength. of light back along the um.er core and propagates the remaining wavelengths of light through the grating, The optical waveguide includes a.
pair of a o opposing surfaces. A compressing device compresses the opposing stufaces of the optical waveguide to tune the grating and change the refiection wavelength of Iight reflected baelc along the innex core. An optical directing device is optically connected to the compression-tuned optical device for combining an input optical signal and an added optical Channel. The input optical signal has a phu-ali,ty of optical channels z s centered at spaced wavelengths, The compression-tuned optical device provides the optical channel to be combined with the input optical signal to provide a combined output signal, In aecorda~.ZCe with another embodiment of fihe present invention, an optical addldrop multipiexer includes a compression-tuned optical device that has an optical waveguide. The optical waveguide includes an inner core disposed within an outer elad.ding and a grating disposed within the innez core. The grating reflects a first reflection wavelength of light back along the inner core and propagates the retxiailiing wavelengths of light through, the grating. The optical waveguide includes a pair of opposing surfaces, A compressing device compresses the optical waveguide to compress the opposing surfaces towards each other to tune the grating and to change the reflection wavelength. of light reflected back along the inner core, An optical directing device is ogtically connected to the compzession-tuned optical device for combining an input optical signal and an added optical cha~tnel, The input optical so signal has a plurality of optical channels centered at spaced wavelengths.
The compression-tuned optical device provides the optical channel to be combined with the input optical signal to provide a combim.ed output signal.
In. accordance with another embodiment of tine present invention, a.
compression-tuned optical addldrop module includes a compression device for a.s providing a compzession force applied along an axis of compression. A
grating compression unit having a grating along the a~ezs of compression is responsive to the optical inpui. signal, and fiazther responsive to the compression force, for providing a grating compression unit optical signal having tla.e selected wavelength of the channel to be added to or dropped from. the input signal.
z o The foregoing and other objects, features and advantages of the present invention will become more apparent in light ortlxe following detailed description of exen~plaxy embodiments ~thareof, as illustrated in the accompanying drawing.
Brief Description of t)xe Drawings z5 hTG. 1 is a. side view of a tunable grating unit of a tunable optical filter and a.
block diagram of a positionallforce feedbaelc control circuit in accordance with the present invention;
FIG. 2 is a side view of a grating element pf a tunable optical filter in accordance with the present invention;
FIG. 3 is a block diagram of a tunable drop filter in accordance with the present invention;
FIG. 4 is a block diagraan of another embodiment of a tunable drop alter in accordance ~arith the present invention;
FIG. 5 is a block diagram of a tunable add filter inn accordance with the present invention;
1~'IG. b is a bloclc diagram of another embodiment of a tunable add filter in accordance with the present invention;
FIG, 7 is a. bloelc dia~am of another embodiment of a tunable add filter in y o accordance urith the present invention, FIG. 8 is a block diagram of at~toyer embodiment of a ttu~able add filter.in accordance with the present invention;
FIG. 9 is a block diagram of a reconiiguxable optical addJc~rop multiplexer (ROADlI~ in accordance with the present invention;
15 FIG. 10 is a bloclc diagram. of.a~~other ~mbodirnel~t of a reconfi,gurable optical addldrop multiplexer (ROAD1VI) in accordance with the present invention;
FIG, 11 is a. block diagram of another embodiment of a reconhgurabl.e optical addldrop multiplexer (1~OAI7M~ in accordance with the present invention;
FIG. 12 is a block diagram of another embodiment of a reconhgurable optical 2 o addldrop multiplexez (ROADM) in accordance with the present zn.vention, and FIG, 13 is a block diagram of another embodiment of a recoufigurable optical addldrop ~n.ultiplexer (ROADM) in accordance with the present invention.
Detailed. Descrigtion of the Invention 25 FIGS. 3 and 4 show respective embodiments of tunable drop filters 80, 90 that filter or drop at least one wavelength band ox optical el,lannel of light, which is cantered at a respective channel wavelength, from a'VSrDM optical input signal 11, FIGS, 5 - 8 show respective embodiments of tunable add f Iters 100,110,120,130 that add or combine at least one optical channel, to a WDM optical input signal 11, As sho~m in FTGs. 9 -13, tha tunable drop and add filters 80,90,100,110,120,130 may be combined in a number ways to provide a reconfiguxable optical add/drop multiplexer (ROADM~ 140,150,160,170,180.
Referring to FIGs. 1 and 2, each of the tunable drop filters, add filter and ROADMs shown in Figs. 3 - 13 include at least one ttu able Bragg grating unit 10, optically coupled to a pork of an optical directing device 12,13 (see Figs. 3 -6), such as a 3 or 4 port circulator, or optical coupler 15. The grating unit x 0 tunes a grating element 14, which is a bulls or large diameter optical waveguide, having an outer cladding 18 and an inner core 16 disposed therein, having a single mode. The grating an element 14 has an outer diameter of at least .3 mrxi and comprises silica.
glass (SiOz) having the appropriate dopants, as is lcnown, to allow light 11 to propagate along the inner core 16, The grating element (laxge diameter optical waveguide) may be formed by using fiber Braying techniques now lcnow or later developed that provido the resultant desired dimensions for the core and the outer dimensions discussed hereinbafore, similar to that disclosed in co-pending US Patent Application, Serial No. 091455,868 entitled "Large Diameter Optical V~l'aveguide, Grating, a~ad Laser".
The grating element n~.ay then, be etched, grounded or machined to form a "dogbone"
shape, as will be described in greatex detail hereiafter. A pair of fibers ox "pigtails" I7 W ay be attached to the ends of the brating element 14 by Icnovvv techniques, such as z o epoxy or glass fusion) Alternatively, floe optical grating element 14 may be formed by heating, collapsing and fusing a glass capi,ll.ary tube to a fzber (not Shown) by a laser, filament, flame, ete,, as is described in copending US Patent Application, Serial. No.
091455,865, entitled "Tube-Encased. Fiber fixating", which is incorporated herein by ~ s reference. Other techniques may be used foz collapsing and fusing the tubes to the fiber, such as is discussed in US Patent No. 5,745,626, entitled "Method For And Encapsulation. Of An Optical Tiber", to Duclc et al,, andlor US Patent No.
4,915,467ø
entitled "Method of Malrixag Fibax Coupler Having Tntegral Precision Connection 'Wells", to Berkey, ~.~hich are incoipoxated herein by reference to the extent necessary to understand the present invention, or other techniques, Alternatively, other techniques may be used to fuse the lzber to the tube, such as using a high temperature glass solder, e.g., a silica solder (powder or solid), such that the fiber, the tube and the solder all become fused to each other, or using laser weldin~fusing or other fusing tBChniques.
The grating element 14 includes a reflective element 20, such as a Bra.gg grating, is vvri ten (embedded or imprinted) into the inner core 16 of the grating element 14. Th.e Bragg grating 20 reflects back a portion the input light 11 as indicated by a line 22 having a predetermined wavelength band of light centered at a ~. o reflection ~tea~srelength ?a,, a~.d passes the remaining wavelengths of the incident light 1.3 (within a. predetermined wavelength zange), as indicated by a line 24, The grating 20, as is 1{nown, is a periodic or aperiodic variation in th.e effective refractive index an.dlor effective optical absorption coefficient of an optical waveguide, such as that desczibed in US patan.t No. 4,725,110 and 4,507,950, entitled "Method for Impressing is GratingS'9Vithin Fiber Optics", to Glenn et al; and US patent No.
5,3$8,173, entitled "Method and Apparatus for Forming Aperiodic Gratings in Optical. Fibers", to Glenn, wluch are hereby incorporated by reference to the extent necessary to u~~derstvt$ the presentinvention.
Txowever, any wavelength-itmable grating ox reflective element 20 embedd.ed,, s o written, etched, imprinted, or otherwise formed in the inner core 16 may be used if desired, As used laexein, th.e term "grating" 'means any of such zeflective dements.
Further, the reflective element (or grating) 20 lnay be used in reflection and/or transmission of light.
Other materials and dimensions fox the optical grating element 14 may be used 2 s if desired. For example, the grating element 14 may be made of any glass, e.g., silica, phosphate glass, or other glasses, or made of glass and plastic, or solely plastic, Tlxe grating element 14 is axially compressed by a compression; d.eviee or housing 30, similar to that described in US Patent Application, Sezial y'o.
09/707,084, entitled "Compression-Tuned Bragg Grating Based Laser" (GiDRA. Docket No. CC-0129D), Une end of the grating elexnent 14 is pressed against a seat 32 in one end 34 of the housing 30. Th.e housing also has a pair of arms (or sides) 36, which.
guide a.
movable bloel~, 3. The block 38 has a seat 40 that presses against the other end of the grating element 14, The axial and faces of the grating element 14 andlor the seats on mating surfaces 32,40 rnay be plated with a material that reduces stresses or enhances the mating of the grating element 14 with the seat on the mating surfaces, The ends of the housing 30 and tloe block 38 have a bone 42 drilled through them to allow the fiber 41 to pass therethtough. Instead of the recessed seats 32,40, the end 34 of fine housing 30 and th.e bloclc 38 may provide a planar surface for engaging flush with fine 2o respective ends of the grating element 14.
The housing 30 may be assembled suclz that a. pre-strain or no pre-stain exists on the ,grating element 14 prior to applying any outside forces.
Atyctuator 44, such as a piezoelectzic actuator, engages the n~ovcable bloels 38, which causes the bloclz to rza.ove as indicated by arrows 46, Accordingly, the PZT
a5 actuator 44 provides a predetermined amount of force to the mooring block 38 to compress the grating element 14, and thereby tune the grating 20 to desired a reflection wavelela.gCh., In response to control signal generated by a displacement control circuit or contxol.ler 60 via conductor 52, the PzT actuator 44 is energized to provide the appropriate compression force necessary to tune the grating element to the z o d.esized l3xagg reflection wavelength of the grating 20, The control circuit 50 adjusts the expansion anal retraction of the actuator 44 in response to an input command 54 and a displacement sensor 56 that provides feedback representative of the strain or eornpression of the grating element 14 to form anon-optical closed-loop control eoniiguration. In other words, light 11 propagating through the network or device is z5 not used to provide feedback for the timing of the grating 20.
In one embodiment, the displacement sensor S6 includes a pear ofcapacitive elements S8 and a displacement sensor circuit 59, sirniIar to that disclosed in co-pending US Patent Application, Serial No, 09!519,802 entitled, "Tamable Optical Structure Featuring Feedback Control", filed March 6, 2000, which is incorporated by reference in its entirety, As shown. in rrCr. 1, each capacitive element S8 is generally tubular having an ~umttlar capacitive end surface 60, The capacitive eleznents 58 are mounted to respective ends of the grating element 14 at b2 such tlta~ the capacitive surfaces 60 are spaced a predetermined distance apart, fox example, approximately 1 -2 microns, Other spacings may be used i.~ desired. The capacitive elements 58 may be bonded or secured using an epoxy or other adhesive compomtd, or fused to grating element 14 using a. COZ laser ox other heating element. The capaeitive surfaces 60 are coated with a metallic coating, such as gold, to form. a pair of annular capacitive plates 64, The change in capacitmce depends on the change in the spacing between xo the capacitive plates.
~leatrodes 66 are attached to the capacitive plates b4 to connect the capacitor to the displacement sensor circuit 59. The sensor circuit 59 measures the capaei.tance between the capacitive plates 64; and provides a sensed signal 67, indicative of the measured capacitance, to the displacement controller 50, As the grating elern.ent 14 is za strained, the gap between the parallel capacitive plates 64 will vary, thereby causing the capacitance to cla.aan.ge correspondingly. Specifically as the grating is compressed, the gap between the capaeitive plates 64 is reduced, resulting in an increase in capacitutce, The change in capacitance is inversely proportional to the change in the reflection wavelength 1y, ofthe grating 20, Since the capacitive elemenfis 58 are z o directly eaxln.ected to the grating element 14, the capacitive elements are passive anal will not slip. One skilled in the art ~twould be able to implement vvitllout undue experinaentation, the sensor electronics circuit 59 to measure the change in eapao.iCance beivycen the two capacitive plates 64.
In the operation of the grating unit 10, the controller SO receives the as wavelength input signal 54, wluch represents fhe desired reflection wavelength to tune the grating unit, In response to the input signal 54 and the sensed signal 67, which is representative of the present resection wavelength of the grating 20, the controller 50 provides a conlxol signal S2 to the actuator 44 to increase or decrease the compression force applied to the grating element 14 to set the desired reflection wavelength of the zo grating 20, The change in applied force to the grating element 14 changes the spacing between the ends of the grating 20, and therefore, the spacing between the capacitive plates 64, As described above, the change in spacing of the capacitive plates changes the capacitance th.exebetween provided to the sensor circuit 59, Wlueh provides displacement feedbacl~ to the controller 50. While the sensor circuit 59 and.
th.e conixoller 50 has been. shown as two separate components, one v~ould recognize that th.e functions of these components may be combined into a single component.
One example of a closed loop actuator 44 that may be used is Model, No, CM
(controller) and DPT-C-M (for a cylindrical actuator) made by Queensgate, Zne.
of 1 o N,'Y'.
Although the invention has been described with respect to using a capacitor 56 to measure the gap dist~co, it should be understood by those slralled in the art that other gap sensing techniques may be used, such as inductive, optical, magnetic, microwave, time-of flight based gap sensors. Moreover,1he scope of the invention is also intended to .include measuring or sensing a force applied on or about the compzessive element, and feeding it beak to control the compression tuning of the optical structure. While the erro.bodiment of the present invention described hereinbefore includes means to provide feedback of the displacement of a grating element 20, one should recognize tlyt the grating units may be accurately and z a repeatably compressed and thus may oporate in art open loog mode.
Alternatively, instead of using a. piezoelectric actuator drl, the grating element 1.4 may be compressed by ataother actuator, such as a solenoid, pnemnatic force actuator, or any other device that is capable of directly or indirectly applying an axial compressive force on the grating element 14. p'urrher, a stepper motor or other type a s of motor whose rotation or position can be co~ixolled may be used to compress the grating eleznenfi, A mechanical linkage connects the motor, e.g" a screw drive, linear actuator, gears, andlor a cam, to the movable block 38 (or piston), which cause the bloclt to move as indicated by arrows d.6, similar to that described in pending U.S.
Patent Application Serial No, 09/751,589 entitled "Wide Range Tunable Optical I~lter", fried Decembez 29, 2000 (CC-0274A); and U,S. Patent Application Serial I~o.
091752,332 entitled "Actuator Mechanism for Tuning an Optical Device", filed Deeembez 29, 2000. (CC-0322), which are incorporated herein by reference, The stepper motor may be a high resolution stepper motor driven in a microstepping mode, s11C1a aS that described in the aforementioned US Patent No, 5,469,520, "Compression Tuned l~ber Grating", to Mozey et al, (e.g., a Melles Griot NANOMOVER), incorporated herei7,a by reference.
As shown in. FIG. 2, the grating eler.~.ent 14 may have a "dogbone" shape having a. narrow central section 70 and larger outer sections 72.
.Advantageously, the zo dofbone shape provides increased sensitivity in converting force applied by the actuator 44 to assure accurate tuning of the grating 20. Th,e narrow section 70 may leave an outer diameter d2 of about 0.8-1 nvaa, and a length L2 of about 5-20 tnyn, The large sections 72 each have a diameter d3 of about 2-3 mm an,d a length L3 of about 2 - 5 nnm, The overall length Ll is about I O-30 mm and flee mufti-component grating ~.s has a length Lg of about 5-20 mm, Other lengths and diameters of the sections 70,72 may be used, Other dimensions and lengths for the grating element 14 and the multi-companelat grating may be used, An inner transition region 74 of the large sections 72 may be a sharp vertical oz angled edge or may be ewwed. A curved geometry lzas less stress risers than a x o sharp edge and tlms may reduce the likelihood of breakage. Also, the large sections 72 may have the outer fluted sections 76 at tine eza~.s.
We have fallnd that such a dimension change between the dimension d3 of the large section 72 and the dimension d2 of the n.arxow section 70 provides increased force to grating wav~elelagth shift sensitivity (or gain or scale factor) by strain 2s amplification. Also, tho dimensions provided herein for the dogbone are easily scalable to provide the desired amoiuat of sensitivity.
Tloe dimensions and geometties for any of the embodiments described herein are merely for, illustrative purposes and, as such, any other dimensions may be used if desired., depending on th.e appli.eatiarm, site, performance, manufacturing zequirements, or other. factors, in view of the teachings herein, The grating element 14 m.ay have tapered (or beveled or angled) outer eoxners or edges 76 to provide a seat fox ilme grating element 14 to mate v~ritb.
housing 30 and moving bloclc 38 atmd%or to adjust the force angles on the grating element, or for other reasons. The angle ofthe bel~eled cornets 76 is set to aclmiewe the desired fwmction. 1n addition, one or both of the axial ends of the grating eleramt 14 vrhere the fiber 4I
attaches may have an outer tapered (or fluted, conical, or apple) axial section 78, 11 or the grating element 14 formed by collapsing a tube onto a fiber, the Bragg 1 o grating may be written in the fiber before or after the capillary tube is encased axou~d and fused to the fiber, such as is discussed in copending US Patent Application, Serial, No. a9/45~5,865, entitled "Tubo-Encased Fiber Grating", filed Deeernber 6, (CiDRA Docket No. CC-0078B), whi.clm is incorporated herein by reference, If the grating 20 is written in the fiber after tb.e Tube is encased. around the grating, tlme is grating naay be written through the tribe into the ~.ber by any desired teehn.ique, such as is described in oopmding US Patent Application, Serial No, 09/205,845, entitled "Method aid Apparatus For Forming A T~.'~e-Encased l3ragg Crrating", filed Deeembez 4,1998, (CiDRA Docltet No, CC-0130) which is incorporated herein by reference, x o While the tunable grating units I O are actively tuned to provide a.
reconfig~.uabl,e optical addldrop multiplexes (ROADM), one v~till appreciate and recognize tlae present invention contemplates substituting the tunable gzating units with athermal grating units, rwhieh passively tune the grating element 14 to .mai.ntain the reflection wavelength of the grating 20 over a predetermined temperature xaimge to 2 s provide a fixed optical addldzop multiplexes (k'OAD1V.17, The athezrnal grating unit is similar to that disclosed in US Patent Application Serial No. 09/699,940 e~.ltitled "Temperature Compensated Optical Device" filed October 30, 2000 (CC-0234A), ~cxrhich is incorporated herein by reference. The invention also contemplates that soma or all the grating units may be substituted for the atllermal grating units.
Refezzing to rrG. 3, the tunable drop i~lter 30 includes a plurality of tunable Hragg grating .nits 10, optically coupled in series to a port of an optical directing device 12, such as a. 3-port circulator, At least ono grating unit 10 is actuated to compzess a respective grating element 14, and therefore, tune a respective grating 20 to reflect die desired optical channels) to be dropped from the optical input signal 1 I, while the other grating units 10 axe tanned or parlced to pass tile remaining channels of the input signal 11.
Zn the operation of the drop filter 80, a first port 81 ofthe circulator 12 receives the input signal 11, having optical channels centered at wavelengths At,~, , , .
to ~, that is transmitted through optical fiber 82. The input signal 11 may originate from a light source or tapped off an optical neCwoxlc (not shown). The circulatax 12 directs the input signal 11 in a clockwise direction to a second port 83 o,f, the circulator. The input signal 11 exits the second porC 83 and propagates through optical fiber 85 to grating elements 14 ofthe grating units 10, r s A select number of gratuzg elements 10 are tuned to reflect corresponding optical charnels of the input signal 1 I, effectively dropping the corresponding optical channel frotta the input signal 11, Tile retxiaining optical grating units 10 are tuned or parked. to pass the remaining optical channels of the input signal 11, to provide an optical signal 86 that does not include the dropped optical channels. for example, as 2 o shown in rTG. 3, a pair of grating ututs 10 are respectively tuned to reflect an optical signal. having optical chmnels centered at wawelengtlZS >~,~, while the remaining gating units I O are pazlced or tuned to pass th.e remaining channels centered at wavelengths A1,7~, . . . 7~,r. The grating units 10 may be parked by tuning the grating units suab that the f.lter function of the grating 20 is parlted between optical ehannel.s, 25 parlced outside of the range of optical channels of the input signal 11, or parked ~t the same wavelength of the grating of another grating unit, which is tined to reflect an optical signal.
z~
Tlle reflected optical channels propagate back to the second pozt 83 of the circulator 12, Which then directs the reflected channels to a third port 87 of the circulator and through optical fiber 88 to provide a drop optical signal 89.
Fig. A. illustzates another embodiment of a tunable drop filter 90, The tunable drop Filter 90 includes a plurality of tunable Bragg grating units 10, optically coupled in series to a port of an optical directing device 12, such as a 3-port circulator. At least one grating unit I O is actuated to compress a respective grating element 14, and therefore, ttuze a respecti~te grating 14 to pass the desired optical, channels) to be dropped from the optical input signal I 1, while the other grating units are tuned to refl.eet the remaining optical channels of the input signal, u~ the operation of the drop filter 90, a first port 91 of the circulator 12 receives the input siglal 11, having optical channels centered at wavelengths A1,A2, ...
)~, that is transmitted through optical fiber 92. The input signal 11 may originate from a light source or tapped off an optical networlc {not. shown). The circulator. 12 i5 directs the input signal 1 I in a. counter-cloelo~rise dareei~ion to a second part 93 of the circulator. Tla.e input signal 11 exits the second port 93 atad propagates through optical fiber 94 to grating elements 14 of the grating units 10.
Each of the grating elements 14 are tuned or parked to pass corresponding optical channels of the input signal 11, effectively dropping the corresponding optical a o channels from the input signal, A select numbez of optical grating waits are tuned to zeflect the remaining optical chay.~.nels of the input signal 11 to provide an optical signal 98, which does net include the dropped optical channels. Fox example as shown in FIC. 4, each of th,e gr. acing ututs 10 are respectively tuned or parked to pass ~.u. optical signal 95 having a optical channels centered at wavelengths 1,2,3, while a 2 s select number of grating units are tuned to reflect the remaiiri.ng channels centezad at ~vavelengtlls A1,3~, ... ~.
The reflected optical channels centered at ~z,>u propagate back fio the second port 93 of the circulator 12, which then directs the zefleeted channels to a third port 96 of the circulator and tlrrough optical (ibex 97 to provide an output optical signal 98.
Refernng to Fig. S, the tunable add filter 100 includes a plurality of tunable Bragg grating units 10 optically coupled in sez~es to a port of an optical direct~yig device 13, such as a 3-port circulator. At least one grating unit I O is actuated to compress a respective grating element 14, and therefore, tune a respective grating 20 to reflect the desired optical, channel.(s) to be added to the optical input signal 11, while the other grating units are tuned to pass the optical channels of the input siyal.
rn the operation of the add filter 100, a first port 101 of the circulator 13 receives the optical signal 102 to be added to the input signal 1 I. The added signal 102 has, for example, a single optical channel centered at wavelei~gtl~ l~
that is z:o transmitted thxough optical fiber 103. The circulator 13 directs the added optical signal 102 in a cloclcwise direction to a second port 104 of the circulator, The added optical sig~lal 102 exits the second port 104 and propagates tluough. optical fiber 105 to grating elements 14 of the grating units 10. At least one grating element 14 is timed to reflect tile added. signal 102 to be combined yyitl~ the input signal I 1. The input light 11, having optical channels centered at rwavelengthS 7~t,~~ . , , ~.r, are transmitted to the grativg el,etnents 14 ofthe grating units 10 through optical fibex 106. The grating elements 14 are tined or parked to pass the optical channels of tlae input signal 11 and combine with, tla,e added optical signal 102 to provide an optical.
signal I09 having optical channels centered at wavelengths ?~i,Aa, ... ~y, 4 a The coxubined optical light propagates ba.ek to the second port 104 ofthe circulator I3, which tlZen directs the combined optical light to a third port 107 of the eixculator 7.3 ao.d thxough optical fiber 108 to provide the output signal 109, having optical channels centered at wavelengths ~1,~2, , .. 7~.
While the add Biter 100 of I~IG. 5 adds a single channel to the inp~.t light 11, 2 s one skilled in the art will appreciate and recognize that more than onE
optical signal may be added provided tlm add filter has a concesponding number of gratiu,g units 10, or a single grating unit that has sufficient bandwidth to reflect adjacent optical eltat~nels to be added.
is Fig. 6 i.l.lusiraces anotla.ex embodiment of a. tunable add alter 110. The tunable add filter 110 includes a plurality of tmiable Bragg grating units 10, optically coupled in series to a port of an optical directing device 13, such as a 3-port circulator, The gratiy~g units 10 are actuated to compress respective grating elements 1d, and therefore, tune or pa~rlt gratings 20 to pass the desired optical channels) to be added to the optical input signal I I, while the outer grating units 10 are tuned to reflect and combine the channels of the input signal 11., ?n the operation of the add filter 110, a first port 1 I 1 of the circulator receives th.e input si.ga~al 11, having optical channels centered at wavelengths 7~~,h3, ...
?o ?~.1, that is lxmsxnitted through optical fiber 112. Tho input signal 11 may originate from a light source or tapped off an optical network (not shown). The circulator 13 directs the input signal I 1 in a counter-clockwise direction to a second port I 13 of th.e circulator. The input signal 11 exits the second port I I3 and propagates through optical i'iber I 14 to the grating elements 14 of the grating units 10. A
select nurxiber zs of grating elements 14 axe tuned to zeflect the optical channels of the iyaput signal 11 centered at wavelengths A1,3~, . , , I~,a of the gratings 20 to be combixted vVith an optical added signal I 15. The added signal 11.5, having an opiical chmnel centered at wavelength ~, are tTmsmitted to the grating elements Id of the grating units I
O
through optical fiber 116. Each grating trait 10 is tuned or parked to pass the optical 2 o clzazu~.el(s) of the added signal 1 I5, which is then combined with the optical i~aput signal 1I to provide a combined optical signal having optical channels centered at ~lo~r ." ~ljy.
The combined optical. signal propagates baclc to the second port 113 of the circulator I.3, Which thezz directs the combined optical 1ig11t to a third port I I7 of the 25 circulator 13 and thzough optical fiber I18 to provide the output signal 119, having optical channels centered at wavelengths A~,')~, .., >~, Referring to Pig. 7, the tuz~.able add filter 120 is similar to the tunable add filter o~ FIG. 5, and therefore, like eorflponents have the same reference number, Tlae tunable add filter 120 includes a plurality of tunable Bragg grating units 10 optically z~
coupled in series to a port of an optical directing device 13, such as a 3-port circulator At least one grating unit I 0 is actuated to compress a respective grating element I4, and therefore, tune a respective grating 20 to reflect the desired optical clza~mel(s) to be added to the optical input signal 11, while the other gxatuig units 10 are tuned or parlced to pass the reznai.ning optical, ch annels of fihe input signal 11; , Zn the operation of the add filter I20, a first port I01 of the circulator 13 receives the added optical signal lOZ to be added to the input signal 11. The added signal 102 may, for example, include a plurality ofoptical channels centered at wavelengths ~1,A2, . . . '~,,~, any of which that maybe added to the input signal 11. The a a added signal 102 is transmitted through optical fiber 103 to th,e circulator 13, ~Wh.icli.
then directs the added optical signal 102 in a clockwise direction to a second port 104 of the. circulator. The added optical signal 102 exits the second port 104 and propagates thro~,gh optical fiber 105 to grating elements 14 ofthe gzating units 10, At least one grating element 1~. is tuned to reflect at least one optical channel of the a.5 added signal 102. For example, one grating unit 10 may be tuned to reflect an optical channel centered at wavelength 7~ to pzovide a filtered added signal 109. The other grating elements are toyed or parked to pass the rem.ainiog optical charutels of the added optical signal 102.
The filtexed added signal propagates baclc to the second port 104 of the z o circulator 13, which then directs the combined optical light to a. third port 10? of the cixculator 13 and through optioal fiber 108 to provide the filtered added signal 109.
The output signal 109 is then transmitted to an irZput port of an optical co~.pler 12I .
The input signal I l, having optical channels centEred at wavelengths 7~i,A3, . .. fir, are transmitted to a second input port of the optical coupler 121. The aptieal coupler 121.
as combines the filtered added signal 109 and the input signal 11 and provides a.
combined optical signal 122 at are output. port orthe coupler, wherein the combined output signal 122 includes a. plurality of channels centered at wavelengths AI,Az, ...
?fir.
ze Wbile the add filter 120 of FIG. 7 adds a single channel. to the input light 11, one skilled in tlae art will appreciate and recognize that more thin on,e.
optical signal may be added prowi.ded the add filter has a. corresponding yaumber of gxating units 10, or a single grating unit that h.as sufficient bandwidth to reflect adjacent optical channels to be added.
Referni.o.g to b'ig. $, the tunable add filter 130 is similar io the tunable add filter 110 of FrG. 6, amd therefore, lilce components have tl.~.e same reference number. The t~.nabl.e add filter 130 includos a plurality of tunable Hragg grating units 10 optically coupled in series to a porC of an optical directing device 131, such as an optical xo coupler, Each of the grating units 10 are actuated to compress respective grating elements 14, and therefore, tune or park gratings 20 to pass the desired optical channels) to be added to the optical input signal 11.
Tn the operation of the add filter 110, tile added signal 115 may, for example, include a plurality of optical channels centered at waYelengths At,7~, , , .
l~, any of zs which that may be added to the input signal 11. The added signal 115 is traansmitted to the grating elern.eots 14 of the dating units 10 through optical fiber 116.
Each grating unit 10 is tuned or parlced to pass a selected opfiieal ela.anxlel(s) ofthe added signal 115 to be added to the input signal 11. For example, each, grating unit 10 may be tined to pass an optical channel at wavelength ~ to provide a filtered added signal a.o 132, The filtered added signal 132 is then transmiti~ed to an input port of an optical coupler 131 through optical fiber 114. The optical coupler 13I combines the filtered added signal. 132 and the input signal 11 and provides a combil~ed optical signal 133 at m output port of the optical ooupler 131, wherein the combined output signal 133 includes a. plurality of channels centered at wavelengths At,A2, . . . ~.
2 s V~hile the add filter 130 of 1~TCr. 8 adds a single channel to the input light 11, one skilled in the a~ will appreciate and recognize that .more than one optical signal may be added.
FIG, 9 illustrates a reconfigurable optical addJdrop multiplexer (RO.AnIVI) that effectively combines the tunable drop filter $0 of FTG. 3 and the tunable add f.~ll:er 100 of FIG, 5, rYvhexein a single series of grating units 10 are. used to both drop a selected optical channel and add a. selected optical channel, as discussed hereinbefore, Components similax to the drop filter 80 of FIG. 3, the add filter 100 of FIG, 5 and the ROADM 140 of FIG. 9 have the same reference number.
As shown in FIG. 9, a pair of grating units 10 are tuned to reflect optical channels centered at wavelen gths ~z,~, w'hi'le the other gratings units are tuned to pass the remaining channels centered at wavelengths hl,lt, , , , ?~,,.
Consequently, fine ROAbM 140 drops optical channels centered at ~rave1e7,1gt11S 7~,~, and adds the added optical signal 102 having a ehal~nel centered at wavelengths 1~~. The output yo signal 109, therefore, includes optical channels centered at ~1,A2,?~y, .
..1~,1.
FIG. 10 illustrates a recon~gurable optical add/drop multxplexer (RO.A.DM) 150 that effectively combines the tunable drop filter 80 of J~IG. 3 and the tunable add filter 110 of FIG, 6, ryherein the add alter 110 is optically connected in series with the drop fl.ter 80, Tloe drop at~d add filters 80,110 .functions substantially the same, as ~.s disoussed hereinbefore, Components suxailar to the drop filter 80 of FIG.
OPTICAL ADD/riROP MULTIPLEXEIt Cross References To Related Applications 'S This is a continuation-in-part o.f US Patent Application, Serial No. 09/S
19,220 a:
entitled "Compression-Tmaed Bragg Grating Based Iteconfiguxable wavelength Channel Addl:Drop Multiplexes", :Czled March 6, 2000 {CC-0204), which is hereby incozporated herein by reference in its entirety.
2b3 Technicalh'ield.
The present inventi.an relates to optical add/drop multiplexes devices, and more partioularly, an optical addldrop multiplexes. {O.ADNI] using a. iarge diametex waveguide for dynamically adding and dropping optical signals from a. "~tflM
optical, signal, l'5 Baclrground Art The telecommunications Indus°'.ry is undergoing dramatic changes with, increased competition, relentless bandwidth, demand, and a migration toward a more data-centric network architeatuxe. First generation point-to-point wave division a o multiplex systems have eased the traffio bot~lenecl~ in the backbone portion of a networlc. As a new cross-connect architecture moves the technology closer to ihew subscriber side of the network, operators are challenged to provide services at fh.e opti.aal .layer, calling for more flexible n.etlvorlcs that can switch and reroute wavelengths. This is placing great emphasis and demand for wavelength agile devices, of which compression-tuned grating devices could play a majox xole.
The need to provide services "ju.st in time" by allocation of wavelengths, and .furth.er migration ofthe optical layer from the high-capacity bacltbone portion to the local loop, is driving the transformation of the network toward an all optie~.l nel."~~orlc in which basic network requixem,ents wilt be performed. in the optical Iayer, The optical, naetwork is a natural evolution of point-to-point dense wavelength division multiplaxin.g (D~7trDM) iTansport to a more dynasn.ie, nexible, and intelligent netwvorlting architecture to improve service delivery tuna. The main element of the optical network is the wavelength (channel), which will be provisioned, configured, .s, routed., and managed in the optical domain. Xntell.igent optical networking will be first deployed as an "opaque" network in which periodic optical-electrical convexsi.on will be required to monitor and isolate signal impairments, Longex xange, the optical netwoxlc will evolve to a "transparent" optical network in which a signal is transported from its source to a destination totally within the optical domain.
io A key elean.ent of the emerging optical z~.etvvoxlc is an optical add/drop multiplexes (OADM), An OADM will drop oz add specific wavelength channels without affecting tla.e ilrrough channels, nixed OADMs can simplify the networlc and readily allow cost-effective DWDM migration from simple point-to-point topologies to tzxed mufti-point configyxations. True dynamic OADM, in which reconfiguration r15: i.s done in the optical domain without optical-electrical conversion, vcrould allow dynamically xeconfigurable, mufti-point DWDM optical networks. This dynamically xeeonfigurable mufti-point architecture is slated to be the next major please in network evolution, with true OADM an enabling network element for this arcllitecturo, One known comrnezcially is a fixed all-optical OADM that couples fixed a o optical clia~mel filters, usually fiber Bragg gratings, to passive optical routing and branching components such as couplers and circulators. The fiber Bragg gratings are not tuned to filter different wavelengths.
A tunable gratiog/ei..rculator approach for dynamically reconfigurable OADM
has also been pursued in the prior art by thermal or strain tuning the gzating. These 2s, dynamic or programmable all-optical OADM designs are based on tunable gratings.
But thermal tuniaag is slow and difficult to maintain and control wavelength to the tolerances required in cun~ent DWDM systems that feature sub-manometer channel spacing, Strain tuning approaches, in vYhioh, the fiber grating is mechanically stretched, loave also proved difficult to maintain and control and tune wavelengths due to ~.ber attachment challenges and slight mechanical creep that cause errors anal slippage. The reliability of a fiber. being lteld under tension for extended periods of tithe is questionable and controversial for use in the industry.
Ball, in United States Patent No, 6,020,986, shows an addldrop module haying a. circulator 16, an array of tunable fiber Bragg gratings, a piezoelectric device and a controller, which is incorporated here:tn by reference. strain is applied by coupling the piezoelectric device to each Ether Bxagg grating, and adjusting the current applied to each piezoel.ectri.e device from the controller. The wavelength, o~ the grating trtay be adjusted ("tuned") i.n th.e manometer range for gratings having a wavelength of a.o. about 1540 manometers. However, SaII does not disclose how the piezoelectric device is physi.cal.l,y coupled to the fiber Bragg gratings to apply strain..
See also United States Patent No. 5,579,143, issued to Huber, and United States latent No.
5,748,349, issued to Mizxahi, which disclose OA.DM systems having tenable optical filters, v~rllzch axe incorporated herein by reference.
z5 Moreover, the grating/circulator approach for OADM has emerged as a. viable rztethod over otl.~er OAAM techniques such as optical switches and arrayed vVaveguide devices, which are broadband in nature, Combinations of switches and wavelength.
rttultiplexers achieve wavelength selection but suffer fram other performance problems such as high optical losses and high cost.
ao Despite intense efforts, dynamic OADMs of such types remain elusive due to inherent performance issues, particularly drift and reliability, tlaz~a thermal or tension grating tuning approaches. T, he inadequacy of thermal and tension-based grating tuning methods to control and maintain wavelength to tight tolerances would require some sort of in-line signal diagnostic, such as a wavelengtl monitoring device or s, speci:rttm. aualy~ex, to provide feedbacle and referencing for closed loop control of the grating v~avelengtla, Summary of the Invention fn accordance with an embodiment of the present invention, an optical drop filter includes a compression-tuned optical device, The compression tuned optical device includes an optical waveguide, which has an inner care disposed within an outer cladding and a grating disposed within the inner core. The grating reflectd a fixst reflection wavelength of light baclc along the inner core and propagates the remainirr,ycvaYelengths of light through the grating. The optical waveguide includes a pair of opposing surfaces. The optical waveguide also includes a compressing devzce that compresses tile optical waveguide fox compressing the opposing surfaces towards each other to tttn.e the grating and change th.e reflection wavelength of light reflected baclt along the inner core. The drop f lter also includes an optical directing device for ~.o providing an input optical sig~.ial to the compression-tuned optical device.. The input optical signal has a plurality of optical channels cantered at spaced wavelengths. The compression-tuned optical device removes an optical charnel from the input opti,eal signal.
In accordance wiill another embodiment of the pxesent invezation, an optical add ~rlter includes a compression-tuned optical device, which has an optical rnaveguide, The optical waveg~iide includes an inner core disposed within an outer cladding and a grating disposed within the inner core. The grating reflects a first reflection. wavelength. of light back along the um.er core and propagates the remaining wavelengths of light through the grating, The optical waveguide includes a.
pair of a o opposing surfaces. A compressing device compresses the opposing stufaces of the optical waveguide to tune the grating and change the refiection wavelength of Iight reflected baelc along the innex core. An optical directing device is optically connected to the compression-tuned optical device for combining an input optical signal and an added optical Channel. The input optical signal has a phu-ali,ty of optical channels z s centered at spaced wavelengths, The compression-tuned optical device provides the optical channel to be combined with the input optical signal to provide a combined output signal, In aecorda~.ZCe with another embodiment of fihe present invention, an optical addldrop multipiexer includes a compression-tuned optical device that has an optical waveguide. The optical waveguide includes an inner core disposed within an outer elad.ding and a grating disposed within the innez core. The grating reflects a first reflection wavelength of light back along the inner core and propagates the retxiailiing wavelengths of light through, the grating. The optical waveguide includes a pair of opposing surfaces, A compressing device compresses the optical waveguide to compress the opposing surfaces towards each other to tune the grating and to change the reflection wavelength. of light reflected back along the inner core, An optical directing device is ogtically connected to the compzession-tuned optical device for combining an input optical signal and an added optical cha~tnel, The input optical so signal has a plurality of optical channels centered at spaced wavelengths.
The compression-tuned optical device provides the optical channel to be combined with the input optical signal to provide a combim.ed output signal.
In. accordance with another embodiment of tine present invention, a.
compression-tuned optical addldrop module includes a compression device for a.s providing a compzession force applied along an axis of compression. A
grating compression unit having a grating along the a~ezs of compression is responsive to the optical inpui. signal, and fiazther responsive to the compression force, for providing a grating compression unit optical signal having tla.e selected wavelength of the channel to be added to or dropped from. the input signal.
z o The foregoing and other objects, features and advantages of the present invention will become more apparent in light ortlxe following detailed description of exen~plaxy embodiments ~thareof, as illustrated in the accompanying drawing.
Brief Description of t)xe Drawings z5 hTG. 1 is a. side view of a tunable grating unit of a tunable optical filter and a.
block diagram of a positionallforce feedbaelc control circuit in accordance with the present invention;
FIG. 2 is a side view of a grating element pf a tunable optical filter in accordance with the present invention;
FIG. 3 is a block diagram of a tunable drop filter in accordance with the present invention;
FIG. 4 is a block diagraan of another embodiment of a tunable drop alter in accordance ~arith the present invention;
FIG. 5 is a block diagram of a tunable add filter inn accordance with the present invention;
1~'IG. b is a bloclc diagram of another embodiment of a tunable add filter in accordance with the present invention;
FIG, 7 is a. bloelc dia~am of another embodiment of a tunable add filter in y o accordance urith the present invention, FIG. 8 is a block diagram of at~toyer embodiment of a ttu~able add filter.in accordance with the present invention;
FIG. 9 is a block diagram of a reconiiguxable optical addJc~rop multiplexer (ROADlI~ in accordance with the present invention;
15 FIG. 10 is a bloclc diagram. of.a~~other ~mbodirnel~t of a reconfi,gurable optical addldrop multiplexer (ROAD1VI) in accordance with the present invention;
FIG, 11 is a. block diagram of another embodiment of a reconhgurabl.e optical addldrop multiplexer (1~OAI7M~ in accordance with the present invention;
FIG. 12 is a block diagram of another embodiment of a reconhgurable optical 2 o addldrop multiplexez (ROADM) in accordance with the present zn.vention, and FIG, 13 is a block diagram of another embodiment of a recoufigurable optical addldrop ~n.ultiplexer (ROADM) in accordance with the present invention.
Detailed. Descrigtion of the Invention 25 FIGS. 3 and 4 show respective embodiments of tunable drop filters 80, 90 that filter or drop at least one wavelength band ox optical el,lannel of light, which is cantered at a respective channel wavelength, from a'VSrDM optical input signal 11, FIGS, 5 - 8 show respective embodiments of tunable add f Iters 100,110,120,130 that add or combine at least one optical channel, to a WDM optical input signal 11, As sho~m in FTGs. 9 -13, tha tunable drop and add filters 80,90,100,110,120,130 may be combined in a number ways to provide a reconfiguxable optical add/drop multiplexer (ROADM~ 140,150,160,170,180.
Referring to FIGs. 1 and 2, each of the tunable drop filters, add filter and ROADMs shown in Figs. 3 - 13 include at least one ttu able Bragg grating unit 10, optically coupled to a pork of an optical directing device 12,13 (see Figs. 3 -6), such as a 3 or 4 port circulator, or optical coupler 15. The grating unit x 0 tunes a grating element 14, which is a bulls or large diameter optical waveguide, having an outer cladding 18 and an inner core 16 disposed therein, having a single mode. The grating an element 14 has an outer diameter of at least .3 mrxi and comprises silica.
glass (SiOz) having the appropriate dopants, as is lcnown, to allow light 11 to propagate along the inner core 16, The grating element (laxge diameter optical waveguide) may be formed by using fiber Braying techniques now lcnow or later developed that provido the resultant desired dimensions for the core and the outer dimensions discussed hereinbafore, similar to that disclosed in co-pending US Patent Application, Serial No. 091455,868 entitled "Large Diameter Optical V~l'aveguide, Grating, a~ad Laser".
The grating element n~.ay then, be etched, grounded or machined to form a "dogbone"
shape, as will be described in greatex detail hereiafter. A pair of fibers ox "pigtails" I7 W ay be attached to the ends of the brating element 14 by Icnovvv techniques, such as z o epoxy or glass fusion) Alternatively, floe optical grating element 14 may be formed by heating, collapsing and fusing a glass capi,ll.ary tube to a fzber (not Shown) by a laser, filament, flame, ete,, as is described in copending US Patent Application, Serial. No.
091455,865, entitled "Tube-Encased. Fiber fixating", which is incorporated herein by ~ s reference. Other techniques may be used foz collapsing and fusing the tubes to the fiber, such as is discussed in US Patent No. 5,745,626, entitled "Method For And Encapsulation. Of An Optical Tiber", to Duclc et al,, andlor US Patent No.
4,915,467ø
entitled "Method of Malrixag Fibax Coupler Having Tntegral Precision Connection 'Wells", to Berkey, ~.~hich are incoipoxated herein by reference to the extent necessary to understand the present invention, or other techniques, Alternatively, other techniques may be used to fuse the lzber to the tube, such as using a high temperature glass solder, e.g., a silica solder (powder or solid), such that the fiber, the tube and the solder all become fused to each other, or using laser weldin~fusing or other fusing tBChniques.
The grating element 14 includes a reflective element 20, such as a Bra.gg grating, is vvri ten (embedded or imprinted) into the inner core 16 of the grating element 14. Th.e Bragg grating 20 reflects back a portion the input light 11 as indicated by a line 22 having a predetermined wavelength band of light centered at a ~. o reflection ~tea~srelength ?a,, a~.d passes the remaining wavelengths of the incident light 1.3 (within a. predetermined wavelength zange), as indicated by a line 24, The grating 20, as is 1{nown, is a periodic or aperiodic variation in th.e effective refractive index an.dlor effective optical absorption coefficient of an optical waveguide, such as that desczibed in US patan.t No. 4,725,110 and 4,507,950, entitled "Method for Impressing is GratingS'9Vithin Fiber Optics", to Glenn et al; and US patent No.
5,3$8,173, entitled "Method and Apparatus for Forming Aperiodic Gratings in Optical. Fibers", to Glenn, wluch are hereby incorporated by reference to the extent necessary to u~~derstvt$ the presentinvention.
Txowever, any wavelength-itmable grating ox reflective element 20 embedd.ed,, s o written, etched, imprinted, or otherwise formed in the inner core 16 may be used if desired, As used laexein, th.e term "grating" 'means any of such zeflective dements.
Further, the reflective element (or grating) 20 lnay be used in reflection and/or transmission of light.
Other materials and dimensions fox the optical grating element 14 may be used 2 s if desired. For example, the grating element 14 may be made of any glass, e.g., silica, phosphate glass, or other glasses, or made of glass and plastic, or solely plastic, Tlxe grating element 14 is axially compressed by a compression; d.eviee or housing 30, similar to that described in US Patent Application, Sezial y'o.
09/707,084, entitled "Compression-Tuned Bragg Grating Based Laser" (GiDRA. Docket No. CC-0129D), Une end of the grating elexnent 14 is pressed against a seat 32 in one end 34 of the housing 30. Th.e housing also has a pair of arms (or sides) 36, which.
guide a.
movable bloel~, 3. The block 38 has a seat 40 that presses against the other end of the grating element 14, The axial and faces of the grating element 14 andlor the seats on mating surfaces 32,40 rnay be plated with a material that reduces stresses or enhances the mating of the grating element 14 with the seat on the mating surfaces, The ends of the housing 30 and tloe block 38 have a bone 42 drilled through them to allow the fiber 41 to pass therethtough. Instead of the recessed seats 32,40, the end 34 of fine housing 30 and th.e bloclc 38 may provide a planar surface for engaging flush with fine 2o respective ends of the grating element 14.
The housing 30 may be assembled suclz that a. pre-strain or no pre-stain exists on the ,grating element 14 prior to applying any outside forces.
Atyctuator 44, such as a piezoelectzic actuator, engages the n~ovcable bloels 38, which causes the bloclz to rza.ove as indicated by arrows 46, Accordingly, the PZT
a5 actuator 44 provides a predetermined amount of force to the mooring block 38 to compress the grating element 14, and thereby tune the grating 20 to desired a reflection wavelela.gCh., In response to control signal generated by a displacement control circuit or contxol.ler 60 via conductor 52, the PzT actuator 44 is energized to provide the appropriate compression force necessary to tune the grating element to the z o d.esized l3xagg reflection wavelength of the grating 20, The control circuit 50 adjusts the expansion anal retraction of the actuator 44 in response to an input command 54 and a displacement sensor 56 that provides feedback representative of the strain or eornpression of the grating element 14 to form anon-optical closed-loop control eoniiguration. In other words, light 11 propagating through the network or device is z5 not used to provide feedback for the timing of the grating 20.
In one embodiment, the displacement sensor S6 includes a pear ofcapacitive elements S8 and a displacement sensor circuit 59, sirniIar to that disclosed in co-pending US Patent Application, Serial No, 09!519,802 entitled, "Tamable Optical Structure Featuring Feedback Control", filed March 6, 2000, which is incorporated by reference in its entirety, As shown. in rrCr. 1, each capacitive element S8 is generally tubular having an ~umttlar capacitive end surface 60, The capacitive eleznents 58 are mounted to respective ends of the grating element 14 at b2 such tlta~ the capacitive surfaces 60 are spaced a predetermined distance apart, fox example, approximately 1 -2 microns, Other spacings may be used i.~ desired. The capacitive elements 58 may be bonded or secured using an epoxy or other adhesive compomtd, or fused to grating element 14 using a. COZ laser ox other heating element. The capaeitive surfaces 60 are coated with a metallic coating, such as gold, to form. a pair of annular capacitive plates 64, The change in capacitmce depends on the change in the spacing between xo the capacitive plates.
~leatrodes 66 are attached to the capacitive plates b4 to connect the capacitor to the displacement sensor circuit 59. The sensor circuit 59 measures the capaei.tance between the capacitive plates 64; and provides a sensed signal 67, indicative of the measured capacitance, to the displacement controller 50, As the grating elern.ent 14 is za strained, the gap between the parallel capacitive plates 64 will vary, thereby causing the capacitance to cla.aan.ge correspondingly. Specifically as the grating is compressed, the gap between the capaeitive plates 64 is reduced, resulting in an increase in capacitutce, The change in capacitance is inversely proportional to the change in the reflection wavelength 1y, ofthe grating 20, Since the capacitive elemenfis 58 are z o directly eaxln.ected to the grating element 14, the capacitive elements are passive anal will not slip. One skilled in the art ~twould be able to implement vvitllout undue experinaentation, the sensor electronics circuit 59 to measure the change in eapao.iCance beivycen the two capacitive plates 64.
In the operation of the grating unit 10, the controller SO receives the as wavelength input signal 54, wluch represents fhe desired reflection wavelength to tune the grating unit, In response to the input signal 54 and the sensed signal 67, which is representative of the present resection wavelength of the grating 20, the controller 50 provides a conlxol signal S2 to the actuator 44 to increase or decrease the compression force applied to the grating element 14 to set the desired reflection wavelength of the zo grating 20, The change in applied force to the grating element 14 changes the spacing between the ends of the grating 20, and therefore, the spacing between the capacitive plates 64, As described above, the change in spacing of the capacitive plates changes the capacitance th.exebetween provided to the sensor circuit 59, Wlueh provides displacement feedbacl~ to the controller 50. While the sensor circuit 59 and.
th.e conixoller 50 has been. shown as two separate components, one v~ould recognize that th.e functions of these components may be combined into a single component.
One example of a closed loop actuator 44 that may be used is Model, No, CM
(controller) and DPT-C-M (for a cylindrical actuator) made by Queensgate, Zne.
of 1 o N,'Y'.
Although the invention has been described with respect to using a capacitor 56 to measure the gap dist~co, it should be understood by those slralled in the art that other gap sensing techniques may be used, such as inductive, optical, magnetic, microwave, time-of flight based gap sensors. Moreover,1he scope of the invention is also intended to .include measuring or sensing a force applied on or about the compzessive element, and feeding it beak to control the compression tuning of the optical structure. While the erro.bodiment of the present invention described hereinbefore includes means to provide feedback of the displacement of a grating element 20, one should recognize tlyt the grating units may be accurately and z a repeatably compressed and thus may oporate in art open loog mode.
Alternatively, instead of using a. piezoelectric actuator drl, the grating element 1.4 may be compressed by ataother actuator, such as a solenoid, pnemnatic force actuator, or any other device that is capable of directly or indirectly applying an axial compressive force on the grating element 14. p'urrher, a stepper motor or other type a s of motor whose rotation or position can be co~ixolled may be used to compress the grating eleznenfi, A mechanical linkage connects the motor, e.g" a screw drive, linear actuator, gears, andlor a cam, to the movable block 38 (or piston), which cause the bloclt to move as indicated by arrows d.6, similar to that described in pending U.S.
Patent Application Serial No, 09/751,589 entitled "Wide Range Tunable Optical I~lter", fried Decembez 29, 2000 (CC-0274A); and U,S. Patent Application Serial I~o.
091752,332 entitled "Actuator Mechanism for Tuning an Optical Device", filed Deeembez 29, 2000. (CC-0322), which are incorporated herein by reference, The stepper motor may be a high resolution stepper motor driven in a microstepping mode, s11C1a aS that described in the aforementioned US Patent No, 5,469,520, "Compression Tuned l~ber Grating", to Mozey et al, (e.g., a Melles Griot NANOMOVER), incorporated herei7,a by reference.
As shown in. FIG. 2, the grating eler.~.ent 14 may have a "dogbone" shape having a. narrow central section 70 and larger outer sections 72.
.Advantageously, the zo dofbone shape provides increased sensitivity in converting force applied by the actuator 44 to assure accurate tuning of the grating 20. Th,e narrow section 70 may leave an outer diameter d2 of about 0.8-1 nvaa, and a length L2 of about 5-20 tnyn, The large sections 72 each have a diameter d3 of about 2-3 mm an,d a length L3 of about 2 - 5 nnm, The overall length Ll is about I O-30 mm and flee mufti-component grating ~.s has a length Lg of about 5-20 mm, Other lengths and diameters of the sections 70,72 may be used, Other dimensions and lengths for the grating element 14 and the multi-companelat grating may be used, An inner transition region 74 of the large sections 72 may be a sharp vertical oz angled edge or may be ewwed. A curved geometry lzas less stress risers than a x o sharp edge and tlms may reduce the likelihood of breakage. Also, the large sections 72 may have the outer fluted sections 76 at tine eza~.s.
We have fallnd that such a dimension change between the dimension d3 of the large section 72 and the dimension d2 of the n.arxow section 70 provides increased force to grating wav~elelagth shift sensitivity (or gain or scale factor) by strain 2s amplification. Also, tho dimensions provided herein for the dogbone are easily scalable to provide the desired amoiuat of sensitivity.
Tloe dimensions and geometties for any of the embodiments described herein are merely for, illustrative purposes and, as such, any other dimensions may be used if desired., depending on th.e appli.eatiarm, site, performance, manufacturing zequirements, or other. factors, in view of the teachings herein, The grating element 14 m.ay have tapered (or beveled or angled) outer eoxners or edges 76 to provide a seat fox ilme grating element 14 to mate v~ritb.
housing 30 and moving bloclc 38 atmd%or to adjust the force angles on the grating element, or for other reasons. The angle ofthe bel~eled cornets 76 is set to aclmiewe the desired fwmction. 1n addition, one or both of the axial ends of the grating eleramt 14 vrhere the fiber 4I
attaches may have an outer tapered (or fluted, conical, or apple) axial section 78, 11 or the grating element 14 formed by collapsing a tube onto a fiber, the Bragg 1 o grating may be written in the fiber before or after the capillary tube is encased axou~d and fused to the fiber, such as is discussed in copending US Patent Application, Serial, No. a9/45~5,865, entitled "Tubo-Encased Fiber Grating", filed Deeernber 6, (CiDRA Docket No. CC-0078B), whi.clm is incorporated herein by reference, If the grating 20 is written in the fiber after tb.e Tube is encased. around the grating, tlme is grating naay be written through the tribe into the ~.ber by any desired teehn.ique, such as is described in oopmding US Patent Application, Serial No, 09/205,845, entitled "Method aid Apparatus For Forming A T~.'~e-Encased l3ragg Crrating", filed Deeembez 4,1998, (CiDRA Docltet No, CC-0130) which is incorporated herein by reference, x o While the tunable grating units I O are actively tuned to provide a.
reconfig~.uabl,e optical addldrop multiplexes (ROADM), one v~till appreciate and recognize tlae present invention contemplates substituting the tunable gzating units with athermal grating units, rwhieh passively tune the grating element 14 to .mai.ntain the reflection wavelength of the grating 20 over a predetermined temperature xaimge to 2 s provide a fixed optical addldzop multiplexes (k'OAD1V.17, The athezrnal grating unit is similar to that disclosed in US Patent Application Serial No. 09/699,940 e~.ltitled "Temperature Compensated Optical Device" filed October 30, 2000 (CC-0234A), ~cxrhich is incorporated herein by reference. The invention also contemplates that soma or all the grating units may be substituted for the atllermal grating units.
Refezzing to rrG. 3, the tunable drop i~lter 30 includes a plurality of tunable Hragg grating .nits 10, optically coupled in series to a port of an optical directing device 12, such as a. 3-port circulator, At least ono grating unit 10 is actuated to compzess a respective grating element 14, and therefore, tune a respective grating 20 to reflect die desired optical channels) to be dropped from the optical input signal 1 I, while the other grating units 10 axe tanned or parlced to pass tile remaining channels of the input signal 11.
Zn the operation of the drop filter 80, a first port 81 ofthe circulator 12 receives the input signal 11, having optical channels centered at wavelengths At,~, , , .
to ~, that is transmitted through optical fiber 82. The input signal 11 may originate from a light source or tapped off an optical neCwoxlc (not shown). The circulatax 12 directs the input signal 11 in a clockwise direction to a second port 83 o,f, the circulator. The input signal 11 exits the second porC 83 and propagates through optical fiber 85 to grating elements 14 ofthe grating units 10, r s A select number of gratuzg elements 10 are tuned to reflect corresponding optical charnels of the input signal 1 I, effectively dropping the corresponding optical channel frotta the input signal 11, Tile retxiaining optical grating units 10 are tuned or parked. to pass the remaining optical channels of the input signal 11, to provide an optical signal 86 that does not include the dropped optical channels. for example, as 2 o shown in rTG. 3, a pair of grating ututs 10 are respectively tuned to reflect an optical signal. having optical chmnels centered at wawelengtlZS >~,~, while the remaining gating units I O are pazlced or tuned to pass th.e remaining channels centered at wavelengths A1,7~, . . . 7~,r. The grating units 10 may be parked by tuning the grating units suab that the f.lter function of the grating 20 is parlted between optical ehannel.s, 25 parlced outside of the range of optical channels of the input signal 11, or parked ~t the same wavelength of the grating of another grating unit, which is tined to reflect an optical signal.
z~
Tlle reflected optical channels propagate back to the second pozt 83 of the circulator 12, Which then directs the reflected channels to a third port 87 of the circulator and through optical fiber 88 to provide a drop optical signal 89.
Fig. A. illustzates another embodiment of a tunable drop filter 90, The tunable drop Filter 90 includes a plurality of tunable Bragg grating units 10, optically coupled in series to a port of an optical directing device 12, such as a 3-port circulator. At least one grating unit I O is actuated to compress a respective grating element 14, and therefore, ttuze a respecti~te grating 14 to pass the desired optical, channels) to be dropped from the optical input signal I 1, while the other grating units are tuned to refl.eet the remaining optical channels of the input signal, u~ the operation of the drop filter 90, a first port 91 of the circulator 12 receives the input siglal 11, having optical channels centered at wavelengths A1,A2, ...
)~, that is transmitted through optical fiber 92. The input signal 11 may originate from a light source or tapped off an optical networlc {not. shown). The circulator. 12 i5 directs the input signal 1 I in a. counter-cloelo~rise dareei~ion to a second part 93 of the circulator. Tla.e input signal 11 exits the second port 93 atad propagates through optical fiber 94 to grating elements 14 of the grating units 10.
Each of the grating elements 14 are tuned or parked to pass corresponding optical channels of the input signal 11, effectively dropping the corresponding optical a o channels from the input signal, A select numbez of optical grating waits are tuned to zeflect the remaining optical chay.~.nels of the input signal 11 to provide an optical signal 98, which does net include the dropped optical channels. Fox example as shown in FIC. 4, each of th,e gr. acing ututs 10 are respectively tuned or parked to pass ~.u. optical signal 95 having a optical channels centered at wavelengths 1,2,3, while a 2 s select number of grating units are tuned to reflect the remaiiri.ng channels centezad at ~vavelengtlls A1,3~, ... ~.
The reflected optical channels centered at ~z,>u propagate back fio the second port 93 of the circulator 12, which then directs the zefleeted channels to a third port 96 of the circulator and tlrrough optical (ibex 97 to provide an output optical signal 98.
Refernng to Fig. S, the tunable add filter 100 includes a plurality of tunable Bragg grating units 10 optically coupled in sez~es to a port of an optical direct~yig device 13, such as a 3-port circulator. At least one grating unit I O is actuated to compress a respective grating element 14, and therefore, tune a respective grating 20 to reflect the desired optical, channel.(s) to be added to the optical input signal 11, while the other grating units are tuned to pass the optical channels of the input siyal.
rn the operation of the add filter 100, a first port 101 of the circulator 13 receives the optical signal 102 to be added to the input signal 1 I. The added signal 102 has, for example, a single optical channel centered at wavelei~gtl~ l~
that is z:o transmitted thxough optical fiber 103. The circulator 13 directs the added optical signal 102 in a cloclcwise direction to a second port 104 of the circulator, The added optical sig~lal 102 exits the second port 104 and propagates tluough. optical fiber 105 to grating elements 14 of the grating units 10. At least one grating element 14 is timed to reflect tile added. signal 102 to be combined yyitl~ the input signal I 1. The input light 11, having optical channels centered at rwavelengthS 7~t,~~ . , , ~.r, are transmitted to the grativg el,etnents 14 ofthe grating units 10 through optical fibex 106. The grating elements 14 are tined or parked to pass the optical channels of tlae input signal 11 and combine with, tla,e added optical signal 102 to provide an optical.
signal I09 having optical channels centered at wavelengths ?~i,Aa, ... ~y, 4 a The coxubined optical light propagates ba.ek to the second port 104 ofthe circulator I3, which tlZen directs the combined optical light to a third port 107 of the eixculator 7.3 ao.d thxough optical fiber 108 to provide the output signal 109, having optical channels centered at wavelengths ~1,~2, , .. 7~.
While the add Biter 100 of I~IG. 5 adds a single channel to the inp~.t light 11, 2 s one skilled in the art will appreciate and recognize that more than onE
optical signal may be added provided tlm add filter has a concesponding number of gratiu,g units 10, or a single grating unit that has sufficient bandwidth to reflect adjacent optical eltat~nels to be added.
is Fig. 6 i.l.lusiraces anotla.ex embodiment of a. tunable add alter 110. The tunable add filter 110 includes a plurality of tmiable Bragg grating units 10, optically coupled in series to a port of an optical directing device 13, such as a 3-port circulator, The gratiy~g units 10 are actuated to compress respective grating elements 1d, and therefore, tune or pa~rlt gratings 20 to pass the desired optical channels) to be added to the optical input signal I I, while the outer grating units 10 are tuned to reflect and combine the channels of the input signal 11., ?n the operation of the add filter 110, a first port 1 I 1 of the circulator receives th.e input si.ga~al 11, having optical channels centered at wavelengths 7~~,h3, ...
?o ?~.1, that is lxmsxnitted through optical fiber 112. Tho input signal 11 may originate from a light source or tapped off an optical network (not shown). The circulator 13 directs the input signal I 1 in a counter-clockwise direction to a second port I 13 of th.e circulator. The input signal 11 exits the second port I I3 and propagates through optical i'iber I 14 to the grating elements 14 of the grating units 10. A
select nurxiber zs of grating elements 14 axe tuned to zeflect the optical channels of the iyaput signal 11 centered at wavelengths A1,3~, . , , I~,a of the gratings 20 to be combixted vVith an optical added signal I 15. The added signal 11.5, having an opiical chmnel centered at wavelength ~, are tTmsmitted to the grating elements Id of the grating units I
O
through optical fiber 116. Each grating trait 10 is tuned or parked to pass the optical 2 o clzazu~.el(s) of the added signal 1 I5, which is then combined with the optical i~aput signal 1I to provide a combined optical signal having optical channels centered at ~lo~r ." ~ljy.
The combined optical. signal propagates baclc to the second port 113 of the circulator I.3, Which thezz directs the combined optical 1ig11t to a third port I I7 of the 25 circulator 13 and thzough optical fiber I18 to provide the output signal 119, having optical channels centered at wavelengths A~,')~, .., >~, Referring to Pig. 7, the tuz~.able add filter 120 is similar to the tunable add filter o~ FIG. 5, and therefore, like eorflponents have the same reference number, Tlae tunable add filter 120 includes a plurality of tunable Bragg grating units 10 optically z~
coupled in series to a port of an optical directing device 13, such as a 3-port circulator At least one grating unit I 0 is actuated to compress a respective grating element I4, and therefore, tune a respective grating 20 to reflect the desired optical clza~mel(s) to be added to the optical input signal 11, while the other gxatuig units 10 are tuned or parlced to pass the reznai.ning optical, ch annels of fihe input signal 11; , Zn the operation of the add filter I20, a first port I01 of the circulator 13 receives the added optical signal lOZ to be added to the input signal 11. The added signal 102 may, for example, include a plurality ofoptical channels centered at wavelengths ~1,A2, . . . '~,,~, any of which that maybe added to the input signal 11. The a a added signal 102 is transmitted through optical fiber 103 to th,e circulator 13, ~Wh.icli.
then directs the added optical signal 102 in a clockwise direction to a second port 104 of the. circulator. The added optical signal 102 exits the second port 104 and propagates thro~,gh optical fiber 105 to grating elements 14 ofthe gzating units 10, At least one grating element 1~. is tuned to reflect at least one optical channel of the a.5 added signal 102. For example, one grating unit 10 may be tuned to reflect an optical channel centered at wavelength 7~ to pzovide a filtered added signal 109. The other grating elements are toyed or parked to pass the rem.ainiog optical charutels of the added optical signal 102.
The filtexed added signal propagates baclc to the second port 104 of the z o circulator 13, which then directs the combined optical light to a. third port 10? of the cixculator 13 and through optioal fiber 108 to provide the filtered added signal 109.
The output signal 109 is then transmitted to an irZput port of an optical co~.pler 12I .
The input signal I l, having optical channels centEred at wavelengths 7~i,A3, . .. fir, are transmitted to a second input port of the optical coupler 121. The aptieal coupler 121.
as combines the filtered added signal 109 and the input signal 11 and provides a.
combined optical signal 122 at are output. port orthe coupler, wherein the combined output signal 122 includes a. plurality of channels centered at wavelengths AI,Az, ...
?fir.
ze Wbile the add filter 120 of FIG. 7 adds a single channel. to the input light 11, one skilled in tlae art will appreciate and recognize that more thin on,e.
optical signal may be added prowi.ded the add filter has a. corresponding yaumber of gxating units 10, or a single grating unit that h.as sufficient bandwidth to reflect adjacent optical channels to be added.
Referni.o.g to b'ig. $, the tunable add filter 130 is similar io the tunable add filter 110 of FrG. 6, amd therefore, lilce components have tl.~.e same reference number. The t~.nabl.e add filter 130 includos a plurality of tunable Hragg grating units 10 optically coupled in series to a porC of an optical directing device 131, such as an optical xo coupler, Each of the grating units 10 are actuated to compress respective grating elements 14, and therefore, tune or park gratings 20 to pass the desired optical channels) to be added to the optical input signal 11.
Tn the operation of the add filter 110, tile added signal 115 may, for example, include a plurality of optical channels centered at waYelengths At,7~, , , .
l~, any of zs which that may be added to the input signal 11. The added signal 115 is traansmitted to the grating elern.eots 14 of the dating units 10 through optical fiber 116.
Each grating unit 10 is tuned or parlced to pass a selected opfiieal ela.anxlel(s) ofthe added signal 115 to be added to the input signal 11. For example, each, grating unit 10 may be tined to pass an optical channel at wavelength ~ to provide a filtered added signal a.o 132, The filtered added signal 132 is then transmiti~ed to an input port of an optical coupler 131 through optical fiber 114. The optical coupler 13I combines the filtered added signal. 132 and the input signal 11 and provides a combil~ed optical signal 133 at m output port of the optical ooupler 131, wherein the combined output signal 133 includes a. plurality of channels centered at wavelengths At,A2, . . . ~.
2 s V~hile the add filter 130 of 1~TCr. 8 adds a single channel to the input light 11, one skilled in the a~ will appreciate and recognize that .more than one optical signal may be added.
FIG, 9 illustrates a reconfigurable optical addJdrop multiplexer (RO.AnIVI) that effectively combines the tunable drop filter $0 of FTG. 3 and the tunable add f.~ll:er 100 of FIG, 5, rYvhexein a single series of grating units 10 are. used to both drop a selected optical channel and add a. selected optical channel, as discussed hereinbefore, Components similax to the drop filter 80 of FIG. 3, the add filter 100 of FIG, 5 and the ROADM 140 of FIG. 9 have the same reference number.
As shown in FIG. 9, a pair of grating units 10 are tuned to reflect optical channels centered at wavelen gths ~z,~, w'hi'le the other gratings units are tuned to pass the remaining channels centered at wavelengths hl,lt, , , , ?~,,.
Consequently, fine ROAbM 140 drops optical channels centered at ~rave1e7,1gt11S 7~,~, and adds the added optical signal 102 having a ehal~nel centered at wavelengths 1~~. The output yo signal 109, therefore, includes optical channels centered at ~1,A2,?~y, .
..1~,1.
FIG. 10 illustrates a recon~gurable optical add/drop multxplexer (RO.A.DM) 150 that effectively combines the tunable drop filter 80 of J~IG. 3 and the tunable add filter 110 of FIG, 6, ryherein the add alter 110 is optically connected in series with the drop fl.ter 80, Tloe drop at~d add filters 80,110 .functions substantially the same, as ~.s disoussed hereinbefore, Components suxailar to the drop filter 80 of FIG.
3, the add filter 110 of FIG. 6 and the RO.ADM 150 of FIG. 10 have the same reference number.
As shown in FIG. 10, a pair of grating units 10 of the drop filter 80 axe tuned to reflect optical channels centered afi wavelengths >~,~, while the other gratings traits are tuned to pass the rem.ainung chaJUtel.s eenCered at wavelengths l~l,~, ...
>~. The 2 o grating units 10 of the add alter 110 axe tuned to pass the added signal 115, haying an optical channel centred a.t A2. Consequently, the ROA.DM 150 drops opti.eaJ, channels centered at Wavelengths 1~2,h~, anal adds the added optical signal 115 lyving a eJ2aru.~el, centered at wavelengths ~. The output signal 119, therefore, includes optical ahanne.ls centered at A~,~2,~, , , , )~.
2s FIG. 11 illustxates a reeanfi.gyable optical add/drop mulhplexer (ROAb~vI) 160 that effectively combines the tunable drop filter 90 of FIG. 4 and the tunable add filter 100 oflllG, 5, whexein the add alter 100 zs optically connected in series with the drop filter 90. The drop and add filters 90,100 functions substantially the same, as zo discussed hsreinbefore. Components similar to the drop fzlter 90 of FIG. ~, the add filter 100 of FIG, 5 and the. ROADM 160 of FIG. 1 I have the. same reference number.
As shown in FIG, 10, each of the grating units 10 of the drop filter 90 are tuned to pass optical eh.annels centered at wavelengths l~a,~, while the other gratings units are tensed to reflect the remaining channels centered at wavelengths ?,1,~, , , , )~, The grating units 10 of the add filter x 00 are tuned to reflect the added signal 102, having an optics). ch.almel centered at ~2. Consequently, the ROADM I60 drops optical chama.els centered at wavel.exyths ~,~, and adds fine added optical.
signal 102 having a channel centered at wavelengths 7~2: The output signal 108, therefore, to includes optical channels centered at ~~,?~,1~, ... )~.
FTG, 12 illustrates a reconfigurable optical add/drop rnultiple~er (ROA:DM) 170 that effectively ootr~biues the tunable drop filter 90 of FTG, 4 and the tunable add filter 110 of FTG. 6, wherein the add f leer 110 is optically connected in series with the drop filter 90. The drop au.d add f lters 90,110 functions substantially the same, as is discussed hereiabefore. ComponEnts similar to the drop filter 90 ofFIG. 4, the add filter I I O of FIG, 6 and the ROA>aM, I70 of FIG, 12 have the same refesenee number.
As shown in FIG. 12, each of the grating units 1.0 of the drop alter 90 are tuned to pass optical channels centered at wavelengths 1~,>~, while the other gratings units are tuned to reflect the remaining channels centered at wavelengths t~1,7~, , , , ?~,~.
a a Each, of th,e grating units 10 of the add filter 110 are tuned to pass the added signal 115, having an optical channel centered at ~2, while the other gratings units are i~.nec~
to reflect the remaining channels centered at wavelengths A1,7~., , . , )~
Consequently, the ROADM 170 drops optics) chu~.nels centered at wavelengths ~2,?<3, and adds the added optical signal 1 I5 having a chaxu~el centered at wavelengths >1Z, The output 2s signal 119, therefore, includes optical c)tannels centered at ~l,~z,~, ...
~, FTG. 13 illustrates a reconfigurable optical add/drop multiplea:ar (ROADM) 170 is substantial.l.y similar to the RO.ADM I60 of FIG, 22, which effectively combines the tunable drop filter 90 of FTG, 4 and the tunable add .filter I l O of FIG. 6.
Effectively, the ItOADM l3.as substituted the pair of 3.port circulators 12, 13 with a single 4-port eircul,ator 181, The ROADM 180 of FIG. 13 operates substantially the same as the ROA17M 170 of FIG. 12, as discussed hereinbefore. Components similar to th,e drop filtex 90 of FTG. 4, the add filter 110 of FZG. 6 an,d floe ROADM
170 of FIG, 12 have the sane reference number.
Itz addition to the above embodiments of an ROADM, the present invention also contemplates other ROADM eonfzguxations by optically connecting in series in various combinations of any one of the tunable drop filters 80,90 of FIGS. 3 and 4 respectively, with any one oftha tunable add filters 120,1,30 of FIGS. 7 and 8 respectively.
a. o While the grating units 10 are interconnected to a 4-port circulator, one will appreciate that it is within the scope of the present invention that any other optical directing device or means may be substituted for the cizculator 1.2,13, such as an optical eouplex, op~cal sputter or frog space.
The dimensions and geornetries for any of the embodiments described herein s5 are merely for illustrative purposes md, as much, any other dimensions may be used if desired, depending on the application, size, performance, manufacturing zequirements, or oilier factors, in view of the teachings herein., Ii should be understood that, unless stated otherwise hexean, any of the features, characteristics, alternatives or modifieatzons described regarding a particular 2 o embodiment herein may also be applied, used, or incorpoxated, with any other embodi,rn.en,t described herein. Also, the drawings herein are not draw. to scale.
Altloough the invention has been described seed illustrated ~rith respect to e:cemplary embodiments thereof tl~e foregoing and various other additions and omissions may be made therei~i ~,vithout departing from the spirit and scope of th.e z s present invention.
As shown in FIG. 10, a pair of grating units 10 of the drop filter 80 axe tuned to reflect optical channels centered afi wavelengths >~,~, while the other gratings traits are tuned to pass the rem.ainung chaJUtel.s eenCered at wavelengths l~l,~, ...
>~. The 2 o grating units 10 of the add alter 110 axe tuned to pass the added signal 115, haying an optical channel centred a.t A2. Consequently, the ROA.DM 150 drops opti.eaJ, channels centered at Wavelengths 1~2,h~, anal adds the added optical signal 115 lyving a eJ2aru.~el, centered at wavelengths ~. The output signal 119, therefore, includes optical ahanne.ls centered at A~,~2,~, , , , )~.
2s FIG. 11 illustxates a reeanfi.gyable optical add/drop mulhplexer (ROAb~vI) 160 that effectively combines the tunable drop filter 90 of FIG. 4 and the tunable add filter 100 oflllG, 5, whexein the add alter 100 zs optically connected in series with the drop filter 90. The drop and add filters 90,100 functions substantially the same, as zo discussed hsreinbefore. Components similar to the drop fzlter 90 of FIG. ~, the add filter 100 of FIG, 5 and the. ROADM 160 of FIG. 1 I have the. same reference number.
As shown in FIG, 10, each of the grating units 10 of the drop filter 90 are tuned to pass optical eh.annels centered at wavelengths l~a,~, while the other gratings units are tensed to reflect the remaining channels centered at wavelengths ?,1,~, , , , )~, The grating units 10 of the add filter x 00 are tuned to reflect the added signal 102, having an optics). ch.almel centered at ~2. Consequently, the ROADM I60 drops optical chama.els centered at wavel.exyths ~,~, and adds fine added optical.
signal 102 having a channel centered at wavelengths 7~2: The output signal 108, therefore, to includes optical channels centered at ~~,?~,1~, ... )~.
FTG, 12 illustrates a reconfigurable optical add/drop rnultiple~er (ROA:DM) 170 that effectively ootr~biues the tunable drop filter 90 of FTG, 4 and the tunable add filter 110 of FTG. 6, wherein the add f leer 110 is optically connected in series with the drop filter 90. The drop au.d add f lters 90,110 functions substantially the same, as is discussed hereiabefore. ComponEnts similar to the drop filter 90 ofFIG. 4, the add filter I I O of FIG, 6 and the ROA>aM, I70 of FIG, 12 have the same refesenee number.
As shown in FIG. 12, each of the grating units 1.0 of the drop alter 90 are tuned to pass optical channels centered at wavelengths 1~,>~, while the other gratings units are tuned to reflect the remaining channels centered at wavelengths t~1,7~, , , , ?~,~.
a a Each, of th,e grating units 10 of the add filter 110 are tuned to pass the added signal 115, having an optical channel centered at ~2, while the other gratings units are i~.nec~
to reflect the remaining channels centered at wavelengths A1,7~., , . , )~
Consequently, the ROADM 170 drops optics) chu~.nels centered at wavelengths ~2,?<3, and adds the added optical signal 1 I5 having a chaxu~el centered at wavelengths >1Z, The output 2s signal 119, therefore, includes optical c)tannels centered at ~l,~z,~, ...
~, FTG. 13 illustrates a reconfigurable optical add/drop multiplea:ar (ROADM) 170 is substantial.l.y similar to the RO.ADM I60 of FIG, 22, which effectively combines the tunable drop filter 90 of FTG, 4 and the tunable add .filter I l O of FIG. 6.
Effectively, the ItOADM l3.as substituted the pair of 3.port circulators 12, 13 with a single 4-port eircul,ator 181, The ROADM 180 of FIG. 13 operates substantially the same as the ROA17M 170 of FIG. 12, as discussed hereinbefore. Components similar to th,e drop filtex 90 of FTG. 4, the add filter 110 of FZG. 6 an,d floe ROADM
170 of FIG, 12 have the sane reference number.
Itz addition to the above embodiments of an ROADM, the present invention also contemplates other ROADM eonfzguxations by optically connecting in series in various combinations of any one of the tunable drop filters 80,90 of FIGS. 3 and 4 respectively, with any one oftha tunable add filters 120,1,30 of FIGS. 7 and 8 respectively.
a. o While the grating units 10 are interconnected to a 4-port circulator, one will appreciate that it is within the scope of the present invention that any other optical directing device or means may be substituted for the cizculator 1.2,13, such as an optical eouplex, op~cal sputter or frog space.
The dimensions and geornetries for any of the embodiments described herein s5 are merely for illustrative purposes md, as much, any other dimensions may be used if desired, depending on the application, size, performance, manufacturing zequirements, or oilier factors, in view of the teachings herein., Ii should be understood that, unless stated otherwise hexean, any of the features, characteristics, alternatives or modifieatzons described regarding a particular 2 o embodiment herein may also be applied, used, or incorpoxated, with any other embodi,rn.en,t described herein. Also, the drawings herein are not draw. to scale.
Altloough the invention has been described seed illustrated ~rith respect to e:cemplary embodiments thereof tl~e foregoing and various other additions and omissions may be made therei~i ~,vithout departing from the spirit and scope of th.e z s present invention.
Claims (31)
1. An optical drop filter comprising:
a compression-tuned optical device including:
an optical waveguide including an inner core disposed within an outer cladding and a.
grating disposed within the inner core, the grating reflecting a first reflection wavelength of light back along the inner core and propagating remaining wavelengths of light through the grating, the optical waveguide including a pair of opposing surfaces; and a compressing device compresses the opposing surfaces towards each other to tune the grating to change the reflection wavelength of light reflected back along the inner core; and an optical directing device for providing an input optical signal to the compression-tuned optical device, the input optical signal having a plurality of optical channels centered at spaced wavelengths;
whereby the compression-tuned optical, device removes an optical channel from the input optical signal.
a compression-tuned optical device including:
an optical waveguide including an inner core disposed within an outer cladding and a.
grating disposed within the inner core, the grating reflecting a first reflection wavelength of light back along the inner core and propagating remaining wavelengths of light through the grating, the optical waveguide including a pair of opposing surfaces; and a compressing device compresses the opposing surfaces towards each other to tune the grating to change the reflection wavelength of light reflected back along the inner core; and an optical directing device for providing an input optical signal to the compression-tuned optical device, the input optical signal having a plurality of optical channels centered at spaced wavelengths;
whereby the compression-tuned optical, device removes an optical channel from the input optical signal.
2. The filter of claim 1 further comprising a plurality of compression-tuned optical devices optically connected in series.
3. The filter of claim 1 wherein the compression-tuned optical device is dynamically tuned to reflect at least one optical channel to be removed from the input optical signal, and passing the remaining optical channels of the input optical signal.
4. The filter of claim 1 wherein the compression-tuned optical device is dynamically tuned to pass at least one optical channel to be removed from the input optical signal, and reflecting the remaining optical channels of the input optical signal.
5. The filter of claim 1 wherein the optical waveguide has outer dimensions along perpendicular axial and transverse directions, the outer dimension being at least 0.3 mm along the transverse direction.
6. The filter of claim 1 wherein at least a portion of the optical waveguide has a transverse cross-section that is contiguous and comprises a substantially homogeneous material.
7. The filter of claim 6 wherein the homogeneous material comprises a glass material.
8. The filter of claim 1 wherein the optical waveguide is cane.
9. The filter of claim 1 wherein at least a portion of the optical waveguide comprises a generally cylindrical shape, having a diameter being at least 0.3 mm.
10. The filter of claim 1 wherein the grating has a characteristic wavelength and wherein the optical wavguide comprises a shape that provides a predetermined sensitivity to a shift in the wavelength due to a change in force on the optical waveguide.
11. The filter of claim 10 wherein the shape of the optical waveguide comprises a generally dogbone shape.
12. The filter of claim 1, wherein the compressing device comprises an actuator for applying axially a compressive force against at least one of the opposing surfaces of the optical waveguide.
13. The filter of claim 1, wherein an outer dimension of the optical waveguide along an axial direction is greater than an outer dimension of the optical waveguide along an transverse direction.
14. The filter of claim 1, wherein the inner core is a single mode core.
15. The filter of claim 1 wherein the compression-tuned optical device passively tunes the optical waveguide in response to a temperature change to maintain the reflection wavelength, over a predetermined temperature range.
16. An optical add filter comprising;
a compression-tuned optical device including:
an optical waveguide including an inner core disposed within an outer cladding and a grating disposed within the inner core, the grating reflecting a first reflection wavelength of light back along the inner core and propagating remaining wavelengths of light through the grating, the optical waveguide including a pair of opposing surfaces; and a compressing device compresses the opposing surfaces towards each other to tune the grating to change the reflection wavelength of light reflected back along the inner core; and an optical directing device optically connected to the compression-tuned optical device for combining an input optical signal and an added optical channel, the input optical signal having a plurality of optical channels centered at spaced wavelengths;
whereby the compression-tuned optical device provides the optical channel to ba combined with the input optical signal to provide a combined output signal.
a compression-tuned optical device including:
an optical waveguide including an inner core disposed within an outer cladding and a grating disposed within the inner core, the grating reflecting a first reflection wavelength of light back along the inner core and propagating remaining wavelengths of light through the grating, the optical waveguide including a pair of opposing surfaces; and a compressing device compresses the opposing surfaces towards each other to tune the grating to change the reflection wavelength of light reflected back along the inner core; and an optical directing device optically connected to the compression-tuned optical device for combining an input optical signal and an added optical channel, the input optical signal having a plurality of optical channels centered at spaced wavelengths;
whereby the compression-tuned optical device provides the optical channel to ba combined with the input optical signal to provide a combined output signal.
17, The filter of claim 1 further comprising a plurality of compression-tuned optical devices optically connected in series.
18. The filter of claim, 1 wherein the compression-tuned optical device is dynamically tuned to reflect at least one optical channel to be added to the input optical signal, and passing the remaining optical channels of the input optical signal.
19. The filter of claim 1 wherein the compression-tuned optical device is dynamically tuned to reflect at least one optical channel to be added to the input optical signal, and passing the remaining optical channels of the input optical signal.
20. The filter of claim 1 wherein the optical waveguide has outer dimensions along perpendicular axial and transverse directions, the outer dimension being at least 0.3 mm along the transverse direction.
21. The filter of claim 1 wherein at least a portion of the optical waveguide has a transverse cross-section that is contiguous and comprises a substantially homogeneous material.
22. The filter of claim 21 wherein the homogeneous material comprises a glass material.
23. The filter of claim 1 wherein the optical waveguide is cane.
24. The filter of claim 1 wherein at least a portion of the optical waveguide comprises a generally cylindrical shape, having a diameter being at least 0.3 mm.
25. The filter of claim 1 wherein the grating has a characteristic wavelength and wherein the optical waveguide comprises a shape that provides a predetermined sensitivity to a shift in the wavelength due to a change in force on the optical waveguide.
26. The filter of claim 10 wherein the shape of the optical waveguide comprises a generally dogbone shape.
27. The filter of claim 1, wherein the compressing device comprises an actuator for applying axially a compressive force against at least one of the opposing surfaces of the optical waveguide.
28. The alter of claim 1, wherein an outer dimension of the optical waveguide along an axial direction is greater than an outer dimension of the optical waveguide along an transverse direction.
29. The filter of claim 1 wherein the compression-tuned optical device passively tunes the optical waveguide in response to a temperature change to maintain the reflection wavelength over a predetermined temperature range.
30. An optical add/drop multiplexer comprising:
a compression-tuned optical device including:
a optical waveguide including an inner core disposed within an outer cladding and a grating disposed within the inner core, the grating reflecting a first reflection wavelength of light back along the inner core and propagating remaining wavelengths of light through the grating, the optical waveguide including a pair of opposing surfaces; and a compressing device compresses the opposing surfaces towards each other to tune the grating to change the reflection wavelength of light reflected back along the inner core; and a first optical directing device optically connected to the compression-tuned optical device for combining an input optical signal and an added optical channel, the input optical signal having a plurality of optical channels centered at spaced wavelengths;
whereby the compression-tuned optical device provides the optical channel to be combined with the input optical signal to provide a combined output signal.
a compression-tuned optical device including:
a optical waveguide including an inner core disposed within an outer cladding and a grating disposed within the inner core, the grating reflecting a first reflection wavelength of light back along the inner core and propagating remaining wavelengths of light through the grating, the optical waveguide including a pair of opposing surfaces; and a compressing device compresses the opposing surfaces towards each other to tune the grating to change the reflection wavelength of light reflected back along the inner core; and a first optical directing device optically connected to the compression-tuned optical device for combining an input optical signal and an added optical channel, the input optical signal having a plurality of optical channels centered at spaced wavelengths;
whereby the compression-tuned optical device provides the optical channel to be combined with the input optical signal to provide a combined output signal.
31. A compression-tuned optical add/drop module comprising:
a compression force assembly for providing a compression force applied along an axis of compression; and a grating compression unit having a grating along the axis of compression, responsive to the optical input signal, and further responsive to the compression force, for providing a grating compression unit optical signal having the selected wavelength of the channel to be added to or dropped from the input signal.
a compression force assembly for providing a compression force applied along an axis of compression; and a grating compression unit having a grating along the axis of compression, responsive to the optical input signal, and further responsive to the compression force, for providing a grating compression unit optical signal having the selected wavelength of the channel to be added to or dropped from the input signal.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US51922000A | 2000-03-06 | 2000-03-06 | |
| US09/519,220 | 2000-03-06 | ||
| PCT/US2001/007165 WO2001067137A2 (en) | 2000-03-06 | 2001-03-06 | Compression-tuned grating-based optical add/drop multiplexer |
| USUNKNOWN | 2003-08-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2402309A1 true CA2402309A1 (en) | 2001-09-13 |
Family
ID=24067387
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002402309A Abandoned CA2402309A1 (en) | 2000-03-06 | 2001-03-06 | Compression-tuned grating-based optical add/drop multiplexer |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP1261888A2 (en) |
| JP (1) | JP2003530586A (en) |
| KR (1) | KR20030034050A (en) |
| AU (1) | AU2001262920A1 (en) |
| CA (1) | CA2402309A1 (en) |
| WO (1) | WO2001067137A2 (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5416877A (en) * | 1988-07-26 | 1995-05-16 | Fuji Photo Film Co., Ltd. | Optical wavelength converter device and optical wavelength converter module |
| US5042898A (en) * | 1989-12-26 | 1991-08-27 | United Technologies Corporation | Incorporated Bragg filter temperature compensated optical waveguide device |
| US5817944A (en) * | 1996-03-19 | 1998-10-06 | The Research Foundation Of State University Of New York | Composite material strain/stress sensor |
| US6020986A (en) * | 1997-11-21 | 2000-02-01 | Jds Uniphase Corporation | Programmable add-drop module for use in an optical circuit |
-
2001
- 2001-03-06 JP JP2001566055A patent/JP2003530586A/en active Pending
- 2001-03-06 KR KR1020027011705A patent/KR20030034050A/en not_active Application Discontinuation
- 2001-03-06 EP EP01937156A patent/EP1261888A2/en not_active Withdrawn
- 2001-03-06 WO PCT/US2001/007165 patent/WO2001067137A2/en not_active Application Discontinuation
- 2001-03-06 AU AU2001262920A patent/AU2001262920A1/en not_active Abandoned
- 2001-03-06 CA CA002402309A patent/CA2402309A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO2001067137A3 (en) | 2002-01-10 |
| KR20030034050A (en) | 2003-05-01 |
| WO2001067137A2 (en) | 2001-09-13 |
| JP2003530586A (en) | 2003-10-14 |
| EP1261888A2 (en) | 2002-12-04 |
| AU2001262920A1 (en) | 2001-09-17 |
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