CA2320769A1 - Optical device - Google Patents
Optical device Download PDFInfo
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- CA2320769A1 CA2320769A1 CA002320769A CA2320769A CA2320769A1 CA 2320769 A1 CA2320769 A1 CA 2320769A1 CA 002320769 A CA002320769 A CA 002320769A CA 2320769 A CA2320769 A CA 2320769A CA 2320769 A1 CA2320769 A1 CA 2320769A1
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- core
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Classifications
-
- 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
- G02B6/02042—Multicore optical fibres
-
- 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
- G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
- G02B6/03605—Highest refractive index not on central axis
-
- 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
- G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
- G02B6/03616—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
- G02B6/03688—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 5 or more layers
-
- 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
- G02B6/255—Splicing of light guides, e.g. by fusion or bonding
- G02B6/2552—Splicing of light guides, e.g. by fusion or bonding reshaping or reforming of light guides for coupling using thermal heating, e.g. tapering, forming of a lens on light guide ends
-
- 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
- G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
- G02B6/2821—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals
- G02B6/2835—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals formed or shaped by thermal treatment, e.g. couplers
-
- 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
-
- 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
Abstract
An optical device comprises a multicore optical fibre having m circularly symmetric cores where m1, the multicore optical fibre having a region of steadily narrowing cross-sectional area. This invention also provides an optical coupler comprising a multicore optical fibre having m circularly symmetric cores optically coupled at a narrowed coupling region to another optical fibre having n cores, where m and n are positive integers and m is greater than 1, the multicore optical fibre having regions of steadily varying cross-sectional area linking the narrowed coupling region to non-narrowed regions of the multicore optical fibre.
Description
_ .. , r.
- r . f -. ~s .
,~~~~ a r f .1 y. f 1 f f --a ~ f a .r r=.s~r ~ w ~.:, a..
OPTICAL DEVICE
'This invention relates to optical devices.
Currently, in order to implement optical devices such as multiplexers, demultiplexcrs and band-Tars -filters ba--opticai ~tr,ansmission systems, -frbre $ragg gratings (FBGs) are used, in conjunction with a circulator. Circulators are expensive non-fibre devices that wshaw ~lativeiy ~ ~erti~ losses and -palarisatian sensitivity. There is thus-a--ueed for-aiiwopticai fibresystems that accomplish a similar _ function and have low insertion Loss and negligible polarisation sensitivity.
Previous attemptsravewbeen-made to-~a~form~-reflective-bawd-stop--devie-a I0 (the FHG) into a transmissive band pass device using just optical fibre technology. A
four port configuration has been reported with a 50:50 coupler arranged to couple two identical fibres with identical FBGs written at both output ports. Light launched into one input fibre is eqnaliy ~piit ~t-the-two vntgut pods where it -is subsequently reflected by the gatmgs ~rzd ~ecombme'd trough the coupler to re-appear on -the .
fourth pan. As this device is based on interferometric principles, however, it requires careful matching of the-outpu.# ports. .
An all-fibre mufti-core , device has also been proposed that performs such transformation (WO-A-98/48305). It comprises a mismatched dual-core fibre-fused with a standard single-core, single-mode fibre aver a particular coupling region. 'Ihe single-care fibre is phaSE-matched-to,-and therefore-e~cchaages power with, onlyoae t~f the cores of the dual core fibre. The length of the coupling region.isadjusted.to.give substantially complete cross-coupling. The ~ati~g is imprinted on the- other (mismatched) core of the dual core fibre outside tie coupling region and it is-used to optically couple the 'two wevr~s by wteai~~re -known -as gratingyassisted -baelcw~d coupling. Power launched into the mismatched-core ~fthe dual cor~~bre will travel unaffected through the coupling region and rerrzain iu the same core-throughout the entire Length of the device. This device, based on gra~Lrng assisted backward coupling, is non iaterferoraetric 'and So ~daes ~t rewire ~rryyent of the fibre ~engtl~
for the output ports. Dual core fibres, -however, are k~~wn to exhihit _polazisation sensitivity, rendering the operation of the entire device polarisation dependent. This OG' ~O~' f means that the system designer must ensure the entering Light has the appropriate polarisation - a factor over which there will typically be no control.
This invention provides an optical device comprising a multicore optical fibre having m circularly symmetric cores where m>I, the multicore optical fibre having a S region of steadily narrowing cross-sectional area.
Using this basic configuration a number of different optical components such as transmissive, polarisation insensitive bandpass short and long period gratings, add/drop multiplexers, as well as acoustically activated band pass filters can be achieved. Compared to the prior art these devices can be made cheap, polarisation IO insensitive and have to have negligible insertion loss. There is no need to use expensive circulators, with their associated insertion losses.
This invention also provides an optical coupler comprising a multicore optical fibre having m circularly symmetric cores optically coupled at a narrowed coupling region to another optical fibre having n cores, where m and n are positive integers and 15 m is greater than 1, the multicore optical fibre having regions of steadily varying cross-sectional area linking the narrowed coupling region to non-narrowed regions of the multicore optical fibre.
Embodiments of the invention will now be described with reference to the accompanying drawings, throughout which parts are referred to by like references and 20 in which:
Figure I shows schematically the refractive index prof le of a; typical circularly symmetric m-core fibre;
Figures 2a to 2f show schematically a mode transformation along a tapered region of a two core circularly symmetric fibre when light is initially launched into the 25 inner core;
Figures 3a to 3f show schematically a mode transformation along a tapered region of a two core circularly symmetric fibre when light is initially launched into the outer core;
Figure 4 shows schematically one embodiment of the invention as a 30 transmissive short-period grating device;
Figure 5 shows schematically an addldrop multipIexer-demultiplexer; and ca o 2 3 2 0 7 6 9 2 0 0 0 - o s - i s S~STITI7TE SHEET (RULE 26) Figure 6 shows schematically a transmissive grating device with a long period.
A cross section of the refractive index of a typical m-core optical fibre used in this embodiment is shown schematically in Figure 1. An innermost core 10 has a standard top hat refi~active index profile 50 while all outer cores 30, 40 have a ring like concentric geometry. The cores are separated by a lower refractive index cladding material 20. These circularly symmetric geometries facilitate the splicing of the device into standard telecom fibres and show no polarisation sensitivity.
As with all multicore waveguide structures, the fibre shown in Figure 1 supports a number of guided eigenmodes. When such a multimode guiding structure is adiabatically tapered (as illustrated schematically in Figure 2a), a mode transformation takes place along a tapered region 70. Examples of such mode transformations for a two core fibre similar to the one shown in Figure 1 are presented in Figures 2 and 3. Figure 2b shows the normalised radial power distribution of a fibre mode initially launched into the inner fibre core 10 in an untapered region 60.
As the mode enters the tapered region 70, it gradually transforms into the corresponding mode of the composite tapered structure. Thus for a Gaussian-like initial mode shown in Figure 2b a continuous transformation into an oscillatory spatial mode, shown in Figure 2f takes place, intermediate stages being shown in Figures 2c, 2d, and 2e.
Once again, Figure 3a illustrates the tapered fibre structure, and Figure 3b shows the normalised power radial distribution of a fibre mode initially launched into an outer ring fibre core 40 in the untapered region 60. As the mode enters the tapered region 70, it gradually transforms into the Gaussian mode, shown in Figure 3f, intermediate stages being shown in Figures 3c, 3d and 3e. These different stages correspond to different taper ratios - defined as the ratio of the taper outer diameter over the untapered initial diameter. The intermediate stage shown in Figure 3c corresponds to a taper ratio of 0.8, for example. Such mode transformation is achieved here with a refractive index profile 50 where the refractive index of the outer ring cores is higher than or equal to the central fibre cores.
This taper effect may be used to achieve a wide variety of all-fibre optical devices. In a first embodiment, illustrated in Figure 4, a transmissive band pass filter ca o 2 3 2 0 7 6 9 2 0 0 0 - o s - i s S~STIZ'I1TE SHEET (RULE 26) is shown. The device comprises a circularly symmetric muIticore fibre 200 optically coupled to a standard single core, single mode fibre 210. The optical coupling is achieved by tapering I80 and fusing 190 together the two fibres 200, 210. The device has four ports: 220, 230, 240 and 250. A grating 260 is incorporated in the port 240 of the multicore fibre, which is not the one into which Light is launched. To avoid back reflections the grating 260 is preferably formed in the outer ring core only.
Light is initially launched into the innermost top-hat core of the multicore fibre 200 in the port 220 which does not contain the grating 260. As it enters a tapered region 180 it gradually transforms into an oscillatory mode pattern that is spatially incompatible and phase mis-matched to the Gaussian-like mode of the other tapered fibre 210. It therefore passes the fused region 190 without exchanging any power and appears in the inner core of the autlet port 240. This change of mode in the broadening taper is due to symmetry and reciprocity. The grating 260 is now used to couple Light from the forward propagating inner core mode into a backward propagating outer ring care mode. This is described as a grating assisted backward coupling process and is known to be wavelength dependent. Light in the outer core mode is gradually transformed into a Gaussian mode as it re-enters the tapered region 180, which is designed to be phase matched to the Gaussian-like mode of the fibre 210 in the fused region 190. The fused length is adjusted to achieve substantially full power exchange between the two fibres. As a result light initially launched into the port 220 of the multicore fibre without a grating will appear at the port 230 of the single core fibre on the same side of the fused region as the initial launch port 220 with negligible insertion losses and no polarisation dependence, providing its wavelength lies within the range of wavelengths reflected by the grating.
Light with a wavelength such that it is not affected by the grating will enter at port 220 and leave at port 240.
In another embodiment two devices similar to the one shown in Figure 4 may be combined to make an add/drop multiplexer-dernultiplexer, as shown in Figure 5.
Multiple channels are launched into the inner core of a port 290 of the multicore fibre at the left of the Figure. One channel, at a wavelength, ~.D, which is to be demultiplexed, is reflected back at the grating 330 and dropped, by the mechanism of ca o 2 3 2 0 ~ 6 9 2 0 0 0 - o s - i s S~STITUTE SHEET (RULE 26) ..-:.:. . z~ ~ ~-ry ~xa .~~ ~s r.~~ '~ ~ ; - ~_. aFe i i . . y ''si W r ~~ J, l i~
I ~r_~ ~~ sues ~~ ..
r z Figure 4 detailed abavc,-at ~ pert 39~-~f a-sirt~,,Ie-zorwfihre-3~6-at ~-~-~
FiQUre. The rest of the channels are at wavelengths lying outside the gratin backward assisted coupling band and continue along the multicore fibre.
A channel--to -be ~ ~twavefen=~th, ~.'~, i~ ~avmched into the yore-oft fibre at a port 310 beyond a further fused section 280. It is subjected to grating assisted bacic~,yard-cs~:pl~~rx-a-~t~-~'~ ~~~ mr~scvr~~~~S.~~~ae f~~~_ in the outer core -of the fiktre. 3~ese ~asfer-ta-t~e iitaer-cvre as they pass~~
taper. The channels are thus coupled to sine mode; single core -fibrz 3?~ -at ~s~eci section 230 and e~cit the device at the outlet port 320 of this fibre.
L O in $ diff~r~t ~mbo~t -a-lang~etiad-b~c-bass-traasmiss~e t~e~iee ~-~be made as illustrated in Figure b. A long ptriod grating 350, which maybe generated by a travelling acoustic wave, is used to couple the Gaussian-like mode of the inner core itlto the oscillatory mode of the- outer rang core befai~ the light hers tl~e tapertd region 70. ~ Along the tapered -region 7fl the ring made is traasformed back ~to a Gaussian-like mode of the tapered fibre and is launched efficiently into a single-mode fibre 340 that is spliced -into it. This is a wavelengtkt-dependent, grating-as$isted forward-coupling process. Light of wavelength-outside the ba dwidth affected by the gating remains in the Gaussian-like mode and eventually transforms into an oscillatorymode upon entering the tapered region 7fl. This mode is coupled to high order cladding modes in the spliced fibre 340 and finally lost.
- 'ihe gating 35d is formed in the -outer ring zladding of the fibre 330 and can either be a permanent, optically written grating or a transient grating.
~~~o
- r . f -. ~s .
,~~~~ a r f .1 y. f 1 f f --a ~ f a .r r=.s~r ~ w ~.:, a..
OPTICAL DEVICE
'This invention relates to optical devices.
Currently, in order to implement optical devices such as multiplexers, demultiplexcrs and band-Tars -filters ba--opticai ~tr,ansmission systems, -frbre $ragg gratings (FBGs) are used, in conjunction with a circulator. Circulators are expensive non-fibre devices that wshaw ~lativeiy ~ ~erti~ losses and -palarisatian sensitivity. There is thus-a--ueed for-aiiwopticai fibresystems that accomplish a similar _ function and have low insertion Loss and negligible polarisation sensitivity.
Previous attemptsravewbeen-made to-~a~form~-reflective-bawd-stop--devie-a I0 (the FHG) into a transmissive band pass device using just optical fibre technology. A
four port configuration has been reported with a 50:50 coupler arranged to couple two identical fibres with identical FBGs written at both output ports. Light launched into one input fibre is eqnaliy ~piit ~t-the-two vntgut pods where it -is subsequently reflected by the gatmgs ~rzd ~ecombme'd trough the coupler to re-appear on -the .
fourth pan. As this device is based on interferometric principles, however, it requires careful matching of the-outpu.# ports. .
An all-fibre mufti-core , device has also been proposed that performs such transformation (WO-A-98/48305). It comprises a mismatched dual-core fibre-fused with a standard single-core, single-mode fibre aver a particular coupling region. 'Ihe single-care fibre is phaSE-matched-to,-and therefore-e~cchaages power with, onlyoae t~f the cores of the dual core fibre. The length of the coupling region.isadjusted.to.give substantially complete cross-coupling. The ~ati~g is imprinted on the- other (mismatched) core of the dual core fibre outside tie coupling region and it is-used to optically couple the 'two wevr~s by wteai~~re -known -as gratingyassisted -baelcw~d coupling. Power launched into the mismatched-core ~fthe dual cor~~bre will travel unaffected through the coupling region and rerrzain iu the same core-throughout the entire Length of the device. This device, based on gra~Lrng assisted backward coupling, is non iaterferoraetric 'and So ~daes ~t rewire ~rryyent of the fibre ~engtl~
for the output ports. Dual core fibres, -however, are k~~wn to exhihit _polazisation sensitivity, rendering the operation of the entire device polarisation dependent. This OG' ~O~' f means that the system designer must ensure the entering Light has the appropriate polarisation - a factor over which there will typically be no control.
This invention provides an optical device comprising a multicore optical fibre having m circularly symmetric cores where m>I, the multicore optical fibre having a S region of steadily narrowing cross-sectional area.
Using this basic configuration a number of different optical components such as transmissive, polarisation insensitive bandpass short and long period gratings, add/drop multiplexers, as well as acoustically activated band pass filters can be achieved. Compared to the prior art these devices can be made cheap, polarisation IO insensitive and have to have negligible insertion loss. There is no need to use expensive circulators, with their associated insertion losses.
This invention also provides an optical coupler comprising a multicore optical fibre having m circularly symmetric cores optically coupled at a narrowed coupling region to another optical fibre having n cores, where m and n are positive integers and 15 m is greater than 1, the multicore optical fibre having regions of steadily varying cross-sectional area linking the narrowed coupling region to non-narrowed regions of the multicore optical fibre.
Embodiments of the invention will now be described with reference to the accompanying drawings, throughout which parts are referred to by like references and 20 in which:
Figure I shows schematically the refractive index prof le of a; typical circularly symmetric m-core fibre;
Figures 2a to 2f show schematically a mode transformation along a tapered region of a two core circularly symmetric fibre when light is initially launched into the 25 inner core;
Figures 3a to 3f show schematically a mode transformation along a tapered region of a two core circularly symmetric fibre when light is initially launched into the outer core;
Figure 4 shows schematically one embodiment of the invention as a 30 transmissive short-period grating device;
Figure 5 shows schematically an addldrop multipIexer-demultiplexer; and ca o 2 3 2 0 7 6 9 2 0 0 0 - o s - i s S~STITI7TE SHEET (RULE 26) Figure 6 shows schematically a transmissive grating device with a long period.
A cross section of the refractive index of a typical m-core optical fibre used in this embodiment is shown schematically in Figure 1. An innermost core 10 has a standard top hat refi~active index profile 50 while all outer cores 30, 40 have a ring like concentric geometry. The cores are separated by a lower refractive index cladding material 20. These circularly symmetric geometries facilitate the splicing of the device into standard telecom fibres and show no polarisation sensitivity.
As with all multicore waveguide structures, the fibre shown in Figure 1 supports a number of guided eigenmodes. When such a multimode guiding structure is adiabatically tapered (as illustrated schematically in Figure 2a), a mode transformation takes place along a tapered region 70. Examples of such mode transformations for a two core fibre similar to the one shown in Figure 1 are presented in Figures 2 and 3. Figure 2b shows the normalised radial power distribution of a fibre mode initially launched into the inner fibre core 10 in an untapered region 60.
As the mode enters the tapered region 70, it gradually transforms into the corresponding mode of the composite tapered structure. Thus for a Gaussian-like initial mode shown in Figure 2b a continuous transformation into an oscillatory spatial mode, shown in Figure 2f takes place, intermediate stages being shown in Figures 2c, 2d, and 2e.
Once again, Figure 3a illustrates the tapered fibre structure, and Figure 3b shows the normalised power radial distribution of a fibre mode initially launched into an outer ring fibre core 40 in the untapered region 60. As the mode enters the tapered region 70, it gradually transforms into the Gaussian mode, shown in Figure 3f, intermediate stages being shown in Figures 3c, 3d and 3e. These different stages correspond to different taper ratios - defined as the ratio of the taper outer diameter over the untapered initial diameter. The intermediate stage shown in Figure 3c corresponds to a taper ratio of 0.8, for example. Such mode transformation is achieved here with a refractive index profile 50 where the refractive index of the outer ring cores is higher than or equal to the central fibre cores.
This taper effect may be used to achieve a wide variety of all-fibre optical devices. In a first embodiment, illustrated in Figure 4, a transmissive band pass filter ca o 2 3 2 0 7 6 9 2 0 0 0 - o s - i s S~STIZ'I1TE SHEET (RULE 26) is shown. The device comprises a circularly symmetric muIticore fibre 200 optically coupled to a standard single core, single mode fibre 210. The optical coupling is achieved by tapering I80 and fusing 190 together the two fibres 200, 210. The device has four ports: 220, 230, 240 and 250. A grating 260 is incorporated in the port 240 of the multicore fibre, which is not the one into which Light is launched. To avoid back reflections the grating 260 is preferably formed in the outer ring core only.
Light is initially launched into the innermost top-hat core of the multicore fibre 200 in the port 220 which does not contain the grating 260. As it enters a tapered region 180 it gradually transforms into an oscillatory mode pattern that is spatially incompatible and phase mis-matched to the Gaussian-like mode of the other tapered fibre 210. It therefore passes the fused region 190 without exchanging any power and appears in the inner core of the autlet port 240. This change of mode in the broadening taper is due to symmetry and reciprocity. The grating 260 is now used to couple Light from the forward propagating inner core mode into a backward propagating outer ring care mode. This is described as a grating assisted backward coupling process and is known to be wavelength dependent. Light in the outer core mode is gradually transformed into a Gaussian mode as it re-enters the tapered region 180, which is designed to be phase matched to the Gaussian-like mode of the fibre 210 in the fused region 190. The fused length is adjusted to achieve substantially full power exchange between the two fibres. As a result light initially launched into the port 220 of the multicore fibre without a grating will appear at the port 230 of the single core fibre on the same side of the fused region as the initial launch port 220 with negligible insertion losses and no polarisation dependence, providing its wavelength lies within the range of wavelengths reflected by the grating.
Light with a wavelength such that it is not affected by the grating will enter at port 220 and leave at port 240.
In another embodiment two devices similar to the one shown in Figure 4 may be combined to make an add/drop multiplexer-dernultiplexer, as shown in Figure 5.
Multiple channels are launched into the inner core of a port 290 of the multicore fibre at the left of the Figure. One channel, at a wavelength, ~.D, which is to be demultiplexed, is reflected back at the grating 330 and dropped, by the mechanism of ca o 2 3 2 0 ~ 6 9 2 0 0 0 - o s - i s S~STITUTE SHEET (RULE 26) ..-:.:. . z~ ~ ~-ry ~xa .~~ ~s r.~~ '~ ~ ; - ~_. aFe i i . . y ''si W r ~~ J, l i~
I ~r_~ ~~ sues ~~ ..
r z Figure 4 detailed abavc,-at ~ pert 39~-~f a-sirt~,,Ie-zorwfihre-3~6-at ~-~-~
FiQUre. The rest of the channels are at wavelengths lying outside the gratin backward assisted coupling band and continue along the multicore fibre.
A channel--to -be ~ ~twavefen=~th, ~.'~, i~ ~avmched into the yore-oft fibre at a port 310 beyond a further fused section 280. It is subjected to grating assisted bacic~,yard-cs~:pl~~rx-a-~t~-~'~ ~~~ mr~scvr~~~~S.~~~ae f~~~_ in the outer core -of the fiktre. 3~ese ~asfer-ta-t~e iitaer-cvre as they pass~~
taper. The channels are thus coupled to sine mode; single core -fibrz 3?~ -at ~s~eci section 230 and e~cit the device at the outlet port 320 of this fibre.
L O in $ diff~r~t ~mbo~t -a-lang~etiad-b~c-bass-traasmiss~e t~e~iee ~-~be made as illustrated in Figure b. A long ptriod grating 350, which maybe generated by a travelling acoustic wave, is used to couple the Gaussian-like mode of the inner core itlto the oscillatory mode of the- outer rang core befai~ the light hers tl~e tapertd region 70. ~ Along the tapered -region 7fl the ring made is traasformed back ~to a Gaussian-like mode of the tapered fibre and is launched efficiently into a single-mode fibre 340 that is spliced -into it. This is a wavelengtkt-dependent, grating-as$isted forward-coupling process. Light of wavelength-outside the ba dwidth affected by the gating remains in the Gaussian-like mode and eventually transforms into an oscillatorymode upon entering the tapered region 7fl. This mode is coupled to high order cladding modes in the spliced fibre 340 and finally lost.
- 'ihe gating 35d is formed in the -outer ring zladding of the fibre 330 and can either be a permanent, optically written grating or a transient grating.
~~~o
Claims (11)
1. An optical device comprising a multicore optical fibre having a plurality of m cores arranged in a concentric geometry with a radially innermost core and a radially outermost core such that the respective indices of the m cores increase in a sequence from the radially innermost core to the radially outermost core, the multicore optical fibre having a region of steadily narrowing cross-sectional area and an optical grating formed in one or more of the m cores of the multicore optical fibre away from the region of steadily narrowing cross-sectional area, the optical grating having a period suitable for providing coupling between ones of the m cores.
2. A device according to claim 1, in which the optical grating is a transiently-formed grating.
3. A device according to claim 1, in which the optical grating is an optically-written grating.
4. A device according to claim 1, 2 or 3, in which the radially innermost core is an axial core.
5. A device according to claim 4, in which the optical grating is formed in one of the m cores that is not the radially innermost core.
6. An optical filter comprising:
an optical device according to claim 4 or 5; and a launching optical arrangement for launching an input optical signal into tie axial core of the multicore optical fibre in a direction of narrowing of the multicore optical fibre.
an optical device according to claim 4 or 5; and a launching optical arrangement for launching an input optical signal into tie axial core of the multicore optical fibre in a direction of narrowing of the multicore optical fibre.
7. An optical coupler comprising:
an optical device according to any one of the preceding claims, coupled at the region of steadily narrowing cross-sectional area to another optical fibre having n cores, where n is a positive integer, the optical device being arranged so that regions of steadily varying cross-sectional area link the region of steadily narrowing cross-sectional area to non-narrowed regions of fine multicore optical fibre.
an optical device according to any one of the preceding claims, coupled at the region of steadily narrowing cross-sectional area to another optical fibre having n cores, where n is a positive integer, the optical device being arranged so that regions of steadily varying cross-sectional area link the region of steadily narrowing cross-sectional area to non-narrowed regions of fine multicore optical fibre.
8. An optical coupler comprising a multicore optical fibre having m concentrically arranged cores optically coupled at a narrowed coupling region to another optical fibre having n cores, where m and n are positive integers and m is greater than 1, the multicore optical fibre having regions of steadily varying cross-sectional area linking the narrowed coupling region to non-narrowed regions of the multicore optical fibre and a grating which is impressed onto at least one of the cores of the multicore optical fibre at a position away from the coupling region and having a period suitable for providing coupling between ones of the cores.
9. An optical add/drop multiplexer/demultiplexer comprising two or more optical filters according to claim 6 or couplers according to claim 7 or 8 connected in series, the filters or couplers being connected at a region having a grating.
10. A grating assisted backward coupling process performed in an optical fibre with multiple concentrically arranged cores, including an inner axial core and an outer ring core, the optical fibre having a tapered region and a grating region arranged away from the tapered region, the grating region including an optical grating formed in one of the cores and having a period suitable for providing coupling between ones of the cores, the process comprising:
(a) launching a light signal into a forward propagating mode of the inner axial core;
(b) using the grating in the grating region to couple the light signal in the forward propagating mode in the inner axial core into a backward propagating mode in the outer ring core; and (c) using the tapered region to transform the light signal in the backward propagating mode in the outer ring core into a Gaussian mode.
(a) launching a light signal into a forward propagating mode of the inner axial core;
(b) using the grating in the grating region to couple the light signal in the forward propagating mode in the inner axial core into a backward propagating mode in the outer ring core; and (c) using the tapered region to transform the light signal in the backward propagating mode in the outer ring core into a Gaussian mode.
11. A grating assisted forward coupling process performed in an optical fibre with multiple concentrically arranged cores, including an inner axial core and an outer ring core, the optical fibre having a tapered region and a grating region arranged away from the tapered region, the grating region including an optical grating formed in one of the cores and having a period suitable for providing coupling between ones of the cores, the process comprising:
(a) launching a light signal into a Gaussian mode of the inner axial core;
(b) using the grating in the grating region to couple the sight signal in the Gaussian mode in the inner axial core into an oscillatory mode in the outer ring core before the light signal enters the tapered region; and (c) using the tapered region to transform the light signal from the oscillatory mode in the outer ring core back into a Gaussian mode.
(a) launching a light signal into a Gaussian mode of the inner axial core;
(b) using the grating in the grating region to couple the sight signal in the Gaussian mode in the inner axial core into an oscillatory mode in the outer ring core before the light signal enters the tapered region; and (c) using the tapered region to transform the light signal from the oscillatory mode in the outer ring core back into a Gaussian mode.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GBGB9803709.6A GB9803709D0 (en) | 1998-02-20 | 1998-02-20 | Polarisation insensitive transmissive fibre devices |
| GB9803709.6 | 1998-02-20 | ||
| PCT/GB1999/000529 WO1999042871A1 (en) | 1998-02-20 | 1999-02-19 | Optical device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2320769A1 true CA2320769A1 (en) | 1999-08-26 |
Family
ID=10827389
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002320769A Abandoned CA2320769A1 (en) | 1998-02-20 | 1999-02-19 | Optical device |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP1057057A1 (en) |
| JP (1) | JP2002504703A (en) |
| AU (1) | AU2540099A (en) |
| CA (1) | CA2320769A1 (en) |
| GB (1) | GB9803709D0 (en) |
| WO (1) | WO1999042871A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6343165B1 (en) * | 1998-02-12 | 2002-01-29 | Novera Optics, Inc. | Optical add drop multiplexer |
| FR2822314B1 (en) * | 2001-03-19 | 2003-06-27 | Highwave Optical Tech | INSERTION-EXTRACTION MULTIPLEXER |
| JP5435476B2 (en) * | 2010-01-15 | 2014-03-05 | 古河電気工業株式会社 | Multi-core optical fiber manufacturing method |
| FR2987905B1 (en) * | 2012-03-08 | 2015-03-20 | Commissariat Energie Atomique | DEVICE FOR CONVERTING THE TRANSVERSE SPATIAL PROFILE OF INTENSITY OF A LUMINOUS BEAM, PREFERABLY USING A MICROSTRUCTURED OPTICAL FIBER |
| US10901240B2 (en) * | 2016-02-04 | 2021-01-26 | Massachusetts Institute Of Technology | Electro-Optic beam controller and method |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4748687A (en) * | 1984-09-25 | 1988-05-31 | Siemens Aktiengesellschaft | Narrow band laser transmitter |
| GB8529861D0 (en) * | 1985-12-04 | 1986-01-15 | Gen Electric Co Ltd | Concatenated coupler |
| US5177803A (en) * | 1991-04-29 | 1993-01-05 | Corning Incorporated | Coaxial optical fiber coupler transmitter-receiver apparatus and method of making same |
| GB9323226D0 (en) * | 1993-11-10 | 1994-01-05 | Northern Telecom Ltd | Optical fibre elements |
| US5473714A (en) * | 1994-04-29 | 1995-12-05 | At&T Corp. | Optical fiber system using tapered fiber devices |
| US5636300A (en) * | 1994-12-12 | 1997-06-03 | Corning Incorporated | MxO multiplex demultiplex component |
-
1998
- 1998-02-20 GB GBGB9803709.6A patent/GB9803709D0/en not_active Ceased
-
1999
- 1999-02-19 WO PCT/GB1999/000529 patent/WO1999042871A1/en not_active Application Discontinuation
- 1999-02-19 AU AU25400/99A patent/AU2540099A/en not_active Abandoned
- 1999-02-19 JP JP2000532751A patent/JP2002504703A/en active Pending
- 1999-02-19 CA CA002320769A patent/CA2320769A1/en not_active Abandoned
- 1999-02-19 EP EP99905105A patent/EP1057057A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JP2002504703A (en) | 2002-02-12 |
| EP1057057A1 (en) | 2000-12-06 |
| AU2540099A (en) | 1999-09-06 |
| GB9803709D0 (en) | 1998-04-15 |
| WO1999042871A1 (en) | 1999-08-26 |
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| FZDE | Discontinued |