CA2211553A1 - Arrangement and method at an optical fibre - Google Patents
Arrangement and method at an optical fibreInfo
- Publication number
- CA2211553A1 CA2211553A1 CA002211553A CA2211553A CA2211553A1 CA 2211553 A1 CA2211553 A1 CA 2211553A1 CA 002211553 A CA002211553 A CA 002211553A CA 2211553 A CA2211553 A CA 2211553A CA 2211553 A1 CA2211553 A1 CA 2211553A1
- Authority
- CA
- Canada
- Prior art keywords
- fibre
- coupler
- wavelength
- optical
- wavelength channels
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
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
- G02B6/24—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
-
- 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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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Communication System (AREA)
- Mechanical Coupling Of Light Guides (AREA)
Abstract
The present invention relates to an arrangement and a method for selectively switching wavelength channels to and from an optical fibre (1). The arrangement according to the invention comprises at least two fibre couplers (2, 3) and one or more fibre gratings (4) arranged between these. The first fibre coupler (2) is adapted to take off a component of the signal and to switch another component of the signal to a fibre grating. The said grating is adapted to function as a band reflex filter and to prevent selected wavelengts from continuing on the fibre (1) and to reflect these back in the fibre (1).
Other wavelengths are allowed to pass further in the arrangement. The second fibre coupler (3) is arranged in a position on the other side of the fibre grating (4) along the optical fibre (1). The said fibre coupler (3) is adapted for introduction of the wavelength removed in the first fibre coupler (2) or for introduction of any other wavelength which is not already present on the fibre.
Other wavelengths are allowed to pass further in the arrangement. The second fibre coupler (3) is arranged in a position on the other side of the fibre grating (4) along the optical fibre (1). The said fibre coupler (3) is adapted for introduction of the wavelength removed in the first fibre coupler (2) or for introduction of any other wavelength which is not already present on the fibre.
Description
Arrange~ent and method at an optical fibre TECHNICAL SPHERE
The present invention relates to an arr~n~m~nt and a method for selective switchin of wavelength channels to and from an optical fibre.
PRIOR ART
In the sphere of telecommunications there is, in many cases. a need for very high tran~mi~ion capacity. By ut~ ing optical transmission by way of modulated optical signals, very rapid data tr~n~mi~ion can be achieved.
In order to L1~L~11IiL a plurality of optical signals o~er a common optical mPAinm wavelength division multiplexing (WDM) is used. The signals are Ll~ A by way of independent wavelength ch~nn~l~, which can exist simlllt~n~ously in an optical fibre.
For selectively ~wiLcl~g a wavelength channel to and from an optical fibre, that is introducing or removing a wavelength channel on an optical fibre, optical multiplexers and wavelength-selective ~ mllltirlexers are used.
An optical cl~mllltiplexer cwl~l;~l.lg waveguide coupler and waveguide grating is known from US-A-5 195 161. A waveguide coupler arran_ed between two parallel waveguides connects to waveguide gratings, so called Brag~ reflectors, c-~nn~te~ to two output ports on the coupler.; By means of the said waveguide grating all light of a desired wavelength can in principle be reflected to an outlet port parallel with the inlet port by constructively using il~l~r~lcllce. The disadvantage to this multi-plexer is that all light of a desired wavelength is only fed out if a very precise ratio exists between the length of waveguide branches between the coupler and the two reflectors. The dirr~,ellce in optical wavelength must be measured to within fractions of a light wavelength; otherwise total e~tin~ hing can occur at the outlet. Thistype of precision is not practically feasible, however, in the case of optical fibres, but can only be achieved in integrated optics. Demultiplexers are consequently both expensive and diff1cult to use in a fibre-optic network.
A fibre coupler for selectively switching a wavelength channel to or from an optical fibre is already known from US-A~} 673 270. This fibre coupler comprises two optical fibres with di~~ refractive index profiles, which are arran_ed ~ Pnt to one another in a switching area. In order to connect a certain wavelength channel 5 between the fibres. the connection coefficient must be periodically varied along the switching area. Ihis addingidropping coupler is difficult to implement since high precision is required in the switchin~ area between the fibres in order to permit switching of a certain wavelength channel in the fibre coupler. For this reason this does not represent an economically or practically feasible solution in many contexts.
DESCRIPTION OF THE INVENTION
The object of the present invention is to provide a wavelength-selective multiplexer and dPm-lltir~lexer, that is an adding/dropping multiplexer (ADM), by means of which wavelength ~ h~nnt~l~ can be switched to and from an optical fibre and blocked at 15 ~I,ill~y positions along this in a system with wavelength division multiplexing (WD~.
Ihis is achieved by the ~n~n~m~nt according to the invention, which c~ mpn.~es two fibre couplers and one or more fibre ~tin&~ arranged 1X~W~;11 them. Ihe first fibre 20 coupler is ~l~i~l to divide up an incoming optical signal, which co~ " ;~P~ aplurality of wavelength ~h~nn~l~, into a first and a second branch in the fibre coupler. The strength ratio between the component signals can be varied ~I,iL~ily.
The cclll~oll~ll signal in the first branch is allowed to pass through the fibre grating, with the exception of one or more wavelength rh~nn~l~ which are reflected in one or 25 more ~tin~ and cnn~eqllPntly prevented from c~ntin--ing on the fibre. Each wave-length channel which is reflected in a grating is allowed to pass to a third branch in the first fibre coupler. Other wavelength ~h~nnel~ are allowed to pass further in the arr~n~ nt Ihe second or third branch of the first fibre coupler is connected to one or more receivers, preferably int~n~led for the wavelengths blocked in the fibre 30 grating. Ihe second fibre coupler is arranged in a position on the other side of the fibre grating along the optical fibre. The said fibre coupler is ~ ptecl for introducing one or more wavelengths removed on the first fibre coupler or for introducing wave-lengths which are not already present on the fibre.
The invention also relates to a method for seiectively switching wavelength channels to and from an optical fibre. In the method according to the invention optical signals. comprising a plurality of wavelength ~h~nn~-lc, are carried to a first fibre coupler. The signal is divided up into two component signals, one of which is fed to a fibre grating, which reflects a certain wavelength channel and prevents this from continl~ing do~ along the optical fibre. The wavelength channel corresponding to the blocking area of the fibre grating is taken off to a receiver conne~teA to the first fibre coupler. One or more wavelength channels are there~er introduced on the optical fibre in a second fibre coupler.
One advantage to the arr~n~emPnt according to the invention is that it is fibre-based and simple in its structure and therefore inexpensive to implement.
DESCRIPTION OF FIGURES
Figure 1 shows a st h~.m~tic tli~m of a wavelength-selective adding/dropping multiplexer (ADM) for selective ~wilcl,illg of a wavelength t~h~nn~l;
Figure 2 shows a srh~.m~tic ~ ~m of a second embodiment of a wavelength-selective ADM for selective ~wi~cl~il,g of a wavelength ch~nn~l;
Figure 3 shows a srl .~ c diagrarn of an ADM for selective switching of four wavelength ch~nnPl~;
Figure 4 shows a srh~-m~tic diagrarn of a second embodiment of an ADM for selective switching of four wavelength ~h~nnel~; and Figure S shows a s~ r..~l~lic fli~m of a third embodiment of an ADM for selective ~wi~ lg of four ~vavelen~th ( h~nn~l~
PREFERRED EMBODIM~TS
The invention will now be described in detail with reference to the figures for the various embo~lill Ir- ll~ of adding/dropping multiplexers (AD~.
30 Figure 1 shows an adding/dropping multiplexer for selective ~wilcl~i~lg of a single specific wavelength ~h~nn~l. A optical signal co~ ;l Ig a plurality of wavelength h~nn~l~ is carried to a fibre coupler 2, which is adapted to switch an incoming optical signal, irrespective of wavelength, to a first fibre branch 21 and a second fibre branch 22 in accordance with a pre~etr" "in~l switching ratio of the fibrecoupler 2, so that a component signal is obtained on each branch. Each componentsignal comprises all wavelen_th channels: division in the fibre coupler only involves a strength division of the signal between the two branches 21, 22. The componentS signal in the second branch 22 is allowed to pass to a b~n-lp~ filter 5. through -~
~vhich only the reception wavelength channel is allowed to pass. The component signal in the first branch 21 is allowed to pass to a band reflex filter, ~vhich is formed by a fibre ~ating 4. The said fibre grating is d~i~n~ to block and reflect the reception wavelength rh~nn~l other wavelength ~h~nn~l~ being propagated 10 unrnodified along the optical fibre 1 even downstrearn of the fibre grating 4. The adding/dropping multiplexer shown in the figure is further provided with a second fibre coupler 3 with freely selectable ~wil~ g ratio, which is adapted to introduce wavelength ~h~nnPl~ on the optical fibre 1. Ihe band reflex filter in the form of a fibre grating f~rilit~t~ the re-intro~--ctir n into the other fibre coupler 3 of the 15 wavelength channel which is removed in the first fibre coupler and blocked in the gtating 4. In the embodiment shown in the figure, wavelength ~h~nn~l~ can be removed and blocked indep~nfl~ntly of one another. The ~n~ngernPnt shown in the figure can ~ Or~ be used to block a wavelength rh~nn~?l on an optical fibre 1, at the sarne time that a completely di~ wavelength channel is being removed from 20 the fibre. It is also possible to introduce into the other fibre coupler 3 any other wavelength channel which is not already present on the optical fibre.
Figure 2 shows a second possible embodiment of the adding/~ropping multiplexer.
As in the embodiment shown in Fig.1, the first fibre coupler 2 is adapted to connect 25 an in~min~ optical signal to a first fibre branch 21 and a second fibre branch 22 of the fibre coupler according to a precl~ . ",;,~ switching ratio. Ihe component signal which is conn~,t~l to the second branch 22 is not subjected to any further procP~.sing Ihe component signal in the first branch 21 is allowed to pass to a fibre grating, which is adapted to entirely reflect a specific wavelength channel, whilst 30 allowing other wavelength ~ h~nn~l~ to pass through the fibre grating 4 and further on the optical fibre 1. The wavelength channel reflected in the fibre grating is returned to the fibre coupler 2 and switched to a third fibre branch 23, which in turn connects to a receiver Rx The b~n~1r~cc filter 5 required in the embodiment according to Figure 1 can consequently be omitted in this embodiment, since filtering out of the wavelength intended for reception occurs through the fibre grating 4, which reflects the desired wavelength charmel to the third fibre branch 23 and on to the receiver Rx. This S wavelength channel is therefore blocked for further tr~nsmi~sion on the fibre 1.
Other wavelen~th rh~nnel.s are allowed to pass through the fibre grating 4, further on the optical fibre 1. The first fibre coupler 2 and second fibre coupler 3 arearranged, as in the embodiment shown in Fig. 1, on either side of the fibre grating 4 and a wavelength channel removed in the fibre coupler 2 can be reintroduced into the 10 second fibre coupler 3.
The adding/dropping mllltirle~Pr shown in Figure 1 can easily be ~ pte~l for introducing or removing a plurality of ~h~nnPlc Fig 3 shows an example for 4 ~h~.".~lc Since each fibre grating c~nstih tP-s a band reflex filter for a wavelength 15 range or a certain special wavçlPn~h, a plu~lity of fibre ~tin~s muct be arranged in an adding/dropping multiplexer for multiple wav~lPn~c. In the example shown in Figure 3 for four cll~nnplc~ four di~ fibre ~tin~c 4a, b, c, d must be arranged between fibre coupler 2 to receiver Rx and fibre coupler 3 for ~e Tx. The embodiment shown in the figL~e Ps~Pnti~lly corresponds to the 20 embodiment in Figure 1. The fimction of a first fibre coupler 2 is to deflect a part of the signal to an optical fibre branch, which is ~ l to a number of b~nflp~cc filters 5. Each of these b~n~p~cc filters 5 is adapted to allow a certain wavelength rh~nnPl to pass to a receiver Rx, provided for this wavelength ~h~nnPI, whilst the other wavelength rh~nnPlc are prevented from passing A second branch 22 of the 25 first fibre coupler 2 is conn~cte-l to the receivers. Ihis branch 22 is further divided by the use of a star coupler or cascade-coupled 2 x 2 coupler to four branches. The four fibre gratings 4a! b, c, d between the first fibre coupler and the second fibre coupler 3 are adapted to prevent the wavelengths which it is int~nrle~ to remove, from progressing to the second fibre coupler 3, in which the same wavelengths are 30 ~lcrcl~ly reintroduced from the optical fibre 1 with a new content. In the embodiment shown in the figure, wavelength ch~nnPlc can be removed and blocked indepPn-lPntly of one another, it being possible, Lh~l~rc~lc, to remove ~h~nnelc other than those which are blocked in tne respective fibre gratings. On the ~ eI side the si~nals from four ~ lers Tx are combined and carlied to a fibre branch in the second fibre coupler 3. The wavelength rh~nnt-ls are then carried to the optical fibre 1 by switching from the fibre coupler 3.
S In the same way the embodiment shown in Figure 2 can be adapted to switching a s~
plurality of wavelength channels to or from an optical fibre 1. Figure 4 shows this adding/dropping multiplexer ~pted to four wavelength ~~h~nn~ls Four fibre gratings 4a, b, c, d are designed so that a first fibre coupler 2 reflects four specific wavelengths. A second branch 22 of the fibre coupler 2, to which the reflected signal is switched, contains a node in which the reflected signal is distributed on the same nurnber of fibre branches as the number of rh~nn~lc that is four in this case.
Each branch comprises a b~ntlp~ss filter Sa, b, c, d, by means of which wavelength rh~nn~ls to be received are allowed to pass to a receiver Rx adapted to the wave-length. Since the adding/dropping multiplexer shown in Figure 2 is adapted to a plurality of rll~nn~ls, the b~n~p~s filters Sa, b, c, d can not be avoided in c~nnrction with removal of the signal, but the double filtrrinE~ which is obtained gives a better filtered signal to the receivers. As in earlier e~mpl~, the second fibre coupler 3, that is that for c ~nnrctin~ the ~ .";ll~,x Tx, is ~n~n~l along the optical fibre 1, at a position in the tl~ inn direction of the signal on the optical fibre 1 which is located d~wl~LLcalll of the fibre grating The embodirnent shown in Figure S finally shows a third way of using an adding/
dropping multiplexer for ~ cl~illg a plurality of wavelength rh~nnt-ls to and from an optical fibre 1. In this embodiment four separate first fibre couplers 2a, b, c, d are used for taking off four wavelength rh:~nnrls to four di~lc~ll receivers R~ Fibre gratings 4 a, b, c, d are arranged after each of the said fibre couplers~ in thedo~l~ll~ll direction along the optical fibre 1. The said gratings are (1PS;~1 toreflect a selected signal, in the same way as in the embodiment shown in Figure 2, down to a receiver Rx for the wavelength channel corresponding to the signal.
Optical isolators 6 a, b, c are arranged between res~;li~e fibre gratings 4a, b, c, and on fibre couplers 2b, c, d following these, in order to prevent the reflected signal from cnntim]ing ~LLca~ in the fibre. The introduction of four ne~v wavelength r.h~nnel.s is achieved in the same way as in the embodiment shown in rl-nnrctiQn CA 022ll553 l997-07-25 with Figure 3 and Figure 4. Since a large number of first fibre couplers 2a! b. c. d is used in the embodiment shown in this figure, the switching ratio between the various branches of the fibre couplers is of great irnportance.
~ =
The present invention relates to an arr~n~m~nt and a method for selective switchin of wavelength channels to and from an optical fibre.
PRIOR ART
In the sphere of telecommunications there is, in many cases. a need for very high tran~mi~ion capacity. By ut~ ing optical transmission by way of modulated optical signals, very rapid data tr~n~mi~ion can be achieved.
In order to L1~L~11IiL a plurality of optical signals o~er a common optical mPAinm wavelength division multiplexing (WDM) is used. The signals are Ll~ A by way of independent wavelength ch~nn~l~, which can exist simlllt~n~ously in an optical fibre.
For selectively ~wiLcl~g a wavelength channel to and from an optical fibre, that is introducing or removing a wavelength channel on an optical fibre, optical multiplexers and wavelength-selective ~ mllltirlexers are used.
An optical cl~mllltiplexer cwl~l;~l.lg waveguide coupler and waveguide grating is known from US-A-5 195 161. A waveguide coupler arran_ed between two parallel waveguides connects to waveguide gratings, so called Brag~ reflectors, c-~nn~te~ to two output ports on the coupler.; By means of the said waveguide grating all light of a desired wavelength can in principle be reflected to an outlet port parallel with the inlet port by constructively using il~l~r~lcllce. The disadvantage to this multi-plexer is that all light of a desired wavelength is only fed out if a very precise ratio exists between the length of waveguide branches between the coupler and the two reflectors. The dirr~,ellce in optical wavelength must be measured to within fractions of a light wavelength; otherwise total e~tin~ hing can occur at the outlet. Thistype of precision is not practically feasible, however, in the case of optical fibres, but can only be achieved in integrated optics. Demultiplexers are consequently both expensive and diff1cult to use in a fibre-optic network.
A fibre coupler for selectively switching a wavelength channel to or from an optical fibre is already known from US-A~} 673 270. This fibre coupler comprises two optical fibres with di~~ refractive index profiles, which are arran_ed ~ Pnt to one another in a switching area. In order to connect a certain wavelength channel 5 between the fibres. the connection coefficient must be periodically varied along the switching area. Ihis addingidropping coupler is difficult to implement since high precision is required in the switchin~ area between the fibres in order to permit switching of a certain wavelength channel in the fibre coupler. For this reason this does not represent an economically or practically feasible solution in many contexts.
DESCRIPTION OF THE INVENTION
The object of the present invention is to provide a wavelength-selective multiplexer and dPm-lltir~lexer, that is an adding/dropping multiplexer (ADM), by means of which wavelength ~ h~nnt~l~ can be switched to and from an optical fibre and blocked at 15 ~I,ill~y positions along this in a system with wavelength division multiplexing (WD~.
Ihis is achieved by the ~n~n~m~nt according to the invention, which c~ mpn.~es two fibre couplers and one or more fibre ~tin&~ arranged 1X~W~;11 them. Ihe first fibre 20 coupler is ~l~i~l to divide up an incoming optical signal, which co~ " ;~P~ aplurality of wavelength ~h~nn~l~, into a first and a second branch in the fibre coupler. The strength ratio between the component signals can be varied ~I,iL~ily.
The cclll~oll~ll signal in the first branch is allowed to pass through the fibre grating, with the exception of one or more wavelength rh~nn~l~ which are reflected in one or 25 more ~tin~ and cnn~eqllPntly prevented from c~ntin--ing on the fibre. Each wave-length channel which is reflected in a grating is allowed to pass to a third branch in the first fibre coupler. Other wavelength ~h~nnel~ are allowed to pass further in the arr~n~ nt Ihe second or third branch of the first fibre coupler is connected to one or more receivers, preferably int~n~led for the wavelengths blocked in the fibre 30 grating. Ihe second fibre coupler is arranged in a position on the other side of the fibre grating along the optical fibre. The said fibre coupler is ~ ptecl for introducing one or more wavelengths removed on the first fibre coupler or for introducing wave-lengths which are not already present on the fibre.
The invention also relates to a method for seiectively switching wavelength channels to and from an optical fibre. In the method according to the invention optical signals. comprising a plurality of wavelength ~h~nn~-lc, are carried to a first fibre coupler. The signal is divided up into two component signals, one of which is fed to a fibre grating, which reflects a certain wavelength channel and prevents this from continl~ing do~ along the optical fibre. The wavelength channel corresponding to the blocking area of the fibre grating is taken off to a receiver conne~teA to the first fibre coupler. One or more wavelength channels are there~er introduced on the optical fibre in a second fibre coupler.
One advantage to the arr~n~emPnt according to the invention is that it is fibre-based and simple in its structure and therefore inexpensive to implement.
DESCRIPTION OF FIGURES
Figure 1 shows a st h~.m~tic tli~m of a wavelength-selective adding/dropping multiplexer (ADM) for selective ~wilcl,illg of a wavelength t~h~nn~l;
Figure 2 shows a srh~.m~tic ~ ~m of a second embodiment of a wavelength-selective ADM for selective ~wi~cl~il,g of a wavelength ch~nn~l;
Figure 3 shows a srl .~ c diagrarn of an ADM for selective switching of four wavelength ch~nnPl~;
Figure 4 shows a srh~-m~tic diagrarn of a second embodiment of an ADM for selective switching of four wavelength ~h~nnel~; and Figure S shows a s~ r..~l~lic fli~m of a third embodiment of an ADM for selective ~wi~ lg of four ~vavelen~th ( h~nn~l~
PREFERRED EMBODIM~TS
The invention will now be described in detail with reference to the figures for the various embo~lill Ir- ll~ of adding/dropping multiplexers (AD~.
30 Figure 1 shows an adding/dropping multiplexer for selective ~wilcl~i~lg of a single specific wavelength ~h~nn~l. A optical signal co~ ;l Ig a plurality of wavelength h~nn~l~ is carried to a fibre coupler 2, which is adapted to switch an incoming optical signal, irrespective of wavelength, to a first fibre branch 21 and a second fibre branch 22 in accordance with a pre~etr" "in~l switching ratio of the fibrecoupler 2, so that a component signal is obtained on each branch. Each componentsignal comprises all wavelen_th channels: division in the fibre coupler only involves a strength division of the signal between the two branches 21, 22. The componentS signal in the second branch 22 is allowed to pass to a b~n-lp~ filter 5. through -~
~vhich only the reception wavelength channel is allowed to pass. The component signal in the first branch 21 is allowed to pass to a band reflex filter, ~vhich is formed by a fibre ~ating 4. The said fibre grating is d~i~n~ to block and reflect the reception wavelength rh~nn~l other wavelength ~h~nn~l~ being propagated 10 unrnodified along the optical fibre 1 even downstrearn of the fibre grating 4. The adding/dropping multiplexer shown in the figure is further provided with a second fibre coupler 3 with freely selectable ~wil~ g ratio, which is adapted to introduce wavelength ~h~nnPl~ on the optical fibre 1. Ihe band reflex filter in the form of a fibre grating f~rilit~t~ the re-intro~--ctir n into the other fibre coupler 3 of the 15 wavelength channel which is removed in the first fibre coupler and blocked in the gtating 4. In the embodiment shown in the figure, wavelength ~h~nn~l~ can be removed and blocked indep~nfl~ntly of one another. The ~n~ngernPnt shown in the figure can ~ Or~ be used to block a wavelength rh~nn~?l on an optical fibre 1, at the sarne time that a completely di~ wavelength channel is being removed from 20 the fibre. It is also possible to introduce into the other fibre coupler 3 any other wavelength channel which is not already present on the optical fibre.
Figure 2 shows a second possible embodiment of the adding/~ropping multiplexer.
As in the embodiment shown in Fig.1, the first fibre coupler 2 is adapted to connect 25 an in~min~ optical signal to a first fibre branch 21 and a second fibre branch 22 of the fibre coupler according to a precl~ . ",;,~ switching ratio. Ihe component signal which is conn~,t~l to the second branch 22 is not subjected to any further procP~.sing Ihe component signal in the first branch 21 is allowed to pass to a fibre grating, which is adapted to entirely reflect a specific wavelength channel, whilst 30 allowing other wavelength ~ h~nn~l~ to pass through the fibre grating 4 and further on the optical fibre 1. The wavelength channel reflected in the fibre grating is returned to the fibre coupler 2 and switched to a third fibre branch 23, which in turn connects to a receiver Rx The b~n~1r~cc filter 5 required in the embodiment according to Figure 1 can consequently be omitted in this embodiment, since filtering out of the wavelength intended for reception occurs through the fibre grating 4, which reflects the desired wavelength charmel to the third fibre branch 23 and on to the receiver Rx. This S wavelength channel is therefore blocked for further tr~nsmi~sion on the fibre 1.
Other wavelen~th rh~nnel.s are allowed to pass through the fibre grating 4, further on the optical fibre 1. The first fibre coupler 2 and second fibre coupler 3 arearranged, as in the embodiment shown in Fig. 1, on either side of the fibre grating 4 and a wavelength channel removed in the fibre coupler 2 can be reintroduced into the 10 second fibre coupler 3.
The adding/dropping mllltirle~Pr shown in Figure 1 can easily be ~ pte~l for introducing or removing a plurality of ~h~nnPlc Fig 3 shows an example for 4 ~h~.".~lc Since each fibre grating c~nstih tP-s a band reflex filter for a wavelength 15 range or a certain special wavçlPn~h, a plu~lity of fibre ~tin~s muct be arranged in an adding/dropping multiplexer for multiple wav~lPn~c. In the example shown in Figure 3 for four cll~nnplc~ four di~ fibre ~tin~c 4a, b, c, d must be arranged between fibre coupler 2 to receiver Rx and fibre coupler 3 for ~e Tx. The embodiment shown in the figL~e Ps~Pnti~lly corresponds to the 20 embodiment in Figure 1. The fimction of a first fibre coupler 2 is to deflect a part of the signal to an optical fibre branch, which is ~ l to a number of b~nflp~cc filters 5. Each of these b~n~p~cc filters 5 is adapted to allow a certain wavelength rh~nnPl to pass to a receiver Rx, provided for this wavelength ~h~nnPI, whilst the other wavelength rh~nnPlc are prevented from passing A second branch 22 of the 25 first fibre coupler 2 is conn~cte-l to the receivers. Ihis branch 22 is further divided by the use of a star coupler or cascade-coupled 2 x 2 coupler to four branches. The four fibre gratings 4a! b, c, d between the first fibre coupler and the second fibre coupler 3 are adapted to prevent the wavelengths which it is int~nrle~ to remove, from progressing to the second fibre coupler 3, in which the same wavelengths are 30 ~lcrcl~ly reintroduced from the optical fibre 1 with a new content. In the embodiment shown in the figure, wavelength ch~nnPlc can be removed and blocked indepPn-lPntly of one another, it being possible, Lh~l~rc~lc, to remove ~h~nnelc other than those which are blocked in tne respective fibre gratings. On the ~ eI side the si~nals from four ~ lers Tx are combined and carlied to a fibre branch in the second fibre coupler 3. The wavelength rh~nnt-ls are then carried to the optical fibre 1 by switching from the fibre coupler 3.
S In the same way the embodiment shown in Figure 2 can be adapted to switching a s~
plurality of wavelength channels to or from an optical fibre 1. Figure 4 shows this adding/dropping multiplexer ~pted to four wavelength ~~h~nn~ls Four fibre gratings 4a, b, c, d are designed so that a first fibre coupler 2 reflects four specific wavelengths. A second branch 22 of the fibre coupler 2, to which the reflected signal is switched, contains a node in which the reflected signal is distributed on the same nurnber of fibre branches as the number of rh~nn~lc that is four in this case.
Each branch comprises a b~ntlp~ss filter Sa, b, c, d, by means of which wavelength rh~nn~ls to be received are allowed to pass to a receiver Rx adapted to the wave-length. Since the adding/dropping multiplexer shown in Figure 2 is adapted to a plurality of rll~nn~ls, the b~n~p~s filters Sa, b, c, d can not be avoided in c~nnrction with removal of the signal, but the double filtrrinE~ which is obtained gives a better filtered signal to the receivers. As in earlier e~mpl~, the second fibre coupler 3, that is that for c ~nnrctin~ the ~ .";ll~,x Tx, is ~n~n~l along the optical fibre 1, at a position in the tl~ inn direction of the signal on the optical fibre 1 which is located d~wl~LLcalll of the fibre grating The embodirnent shown in Figure S finally shows a third way of using an adding/
dropping multiplexer for ~ cl~illg a plurality of wavelength rh~nnt-ls to and from an optical fibre 1. In this embodiment four separate first fibre couplers 2a, b, c, d are used for taking off four wavelength rh:~nnrls to four di~lc~ll receivers R~ Fibre gratings 4 a, b, c, d are arranged after each of the said fibre couplers~ in thedo~l~ll~ll direction along the optical fibre 1. The said gratings are (1PS;~1 toreflect a selected signal, in the same way as in the embodiment shown in Figure 2, down to a receiver Rx for the wavelength channel corresponding to the signal.
Optical isolators 6 a, b, c are arranged between res~;li~e fibre gratings 4a, b, c, and on fibre couplers 2b, c, d following these, in order to prevent the reflected signal from cnntim]ing ~LLca~ in the fibre. The introduction of four ne~v wavelength r.h~nnel.s is achieved in the same way as in the embodiment shown in rl-nnrctiQn CA 022ll553 l997-07-25 with Figure 3 and Figure 4. Since a large number of first fibre couplers 2a! b. c. d is used in the embodiment shown in this figure, the switching ratio between the various branches of the fibre couplers is of great irnportance.
~ =
Claims (10)
1. Arrangement for switching one or more wavelength channels to and from an optical fibre (1) characterised in that it comprises - at least one first fibre coupler (1), arranged connected to the fibre, the said coupler being adapted to remove one or more wavelength channels from the optical fibre (1);
- at least one second fibre coupler (3), arranged connected to the fibre (1) downstream of this in relation to the first fibre coupler (2), the said second coupler being adapted to carry one or more wavelength channels from a transmitter (Tx) to the optical fibre (1); and - one or more fibre gratings (4), arranged connected to the fibre (1) between the said fibre couplers (2,3), the said grating being adapted to reflect and prevent one or more wavelength channels from continuing on the optical fibre (1).
- at least one second fibre coupler (3), arranged connected to the fibre (1) downstream of this in relation to the first fibre coupler (2), the said second coupler being adapted to carry one or more wavelength channels from a transmitter (Tx) to the optical fibre (1); and - one or more fibre gratings (4), arranged connected to the fibre (1) between the said fibre couplers (2,3), the said grating being adapted to reflect and prevent one or more wavelength channels from continuing on the optical fibre (1).
2. Arrangement according to claim 1, characterised in that a first branch (21) on the first fibre coupler (2) is connected to a fibre grating (4) and that a second branch (22) or third branch (23) on the first fibre coupler (2) is connected to one or more receivers (Rx).
3. Arrangement according to claim 2, characterised in that one or more fibre gratings (4) are adapted to reflect one or more wavelength channels to the thirdbranch (23) of the fibre coupler.
4. Arrangement according to claim 2 or 3, characterised in that a bandpass filter (5), adjusted to a certain wavelength, is arranged between the second branch (22) or third branch (23) of the fibre coupler and each receiver (Rx).
5. Arrangement according to claim 1, characterised in that the fibre gratings (4a, b, c, d) arranged between the first fibre coupler (2) and second fibre coupler (3) are adapted so that their number corresponds to the number of wavelengths to be removed.
6. Arrangement according to claim 1, characterised in that the number of fibrecouplers (2a, b, c, d) for removing a wavelength channel from the optical fibre (1) corresponds to the number of wavelengths to be removed. that fibre gratings (4a, b, c, d) intended for reflecting the respective wavelength are arranged immediately after each fibre coupler (2a, b, c, d) intended for taking off, and that optical isolators (6a, b, c) arranged between the fibre couplers (2a, b, c, d) are adapted to prevent the wavelengths reflected in the fibre gratings (4a, b, c, d) from passing upstream in the optical fibre (1).
7. Method for switching one or more wavelength channels to and from an optical fibre (1), characterised by the following steps:
- carrying a first optical signal, comprising a plurality of wavelength channels, to a first fibre coupler (2);
- dividing the optical signal up into a first and a second component signal in the first fibre coupler (2);
- carrying the first of the component signals to one or more fibre gratings (4), one wavelength channel being reflected in each fibre grating and prevented from continuing on the optical fibre (1);
- taking off of wavelength channels, corresponding to the blocking range of the fibre grating, to receivers (Rx) connected to the first fibre coupler (2); and - introducing one or more wavelength channels on the optical fibre (1) in a second fibre coupler (3).
- carrying a first optical signal, comprising a plurality of wavelength channels, to a first fibre coupler (2);
- dividing the optical signal up into a first and a second component signal in the first fibre coupler (2);
- carrying the first of the component signals to one or more fibre gratings (4), one wavelength channel being reflected in each fibre grating and prevented from continuing on the optical fibre (1);
- taking off of wavelength channels, corresponding to the blocking range of the fibre grating, to receivers (Rx) connected to the first fibre coupler (2); and - introducing one or more wavelength channels on the optical fibre (1) in a second fibre coupler (3).
8. Method according to claim 7, characterised in that the wavelength channels which are taken off in the first fibre coupler (2) are reintroduced into the second fibre coupler (3).
9. Method according to claim 7 or 8, characterised in that the second component signal is carried to one or more bandpass filters (5a, b, c, d) which allow the wavelength channels blocked in the fibre gratings (4a, b, c, d) to pass to receivers (Rx) connected to the first fibre coupler.
10. Method according to claim 7 or 8, characterised in that one or more wavelength channels blocked in the fibre gratings (4a, b, c, d) are carried to one or more receivers (Rx) cormected to the first fibre coupler.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9500406-5 | 1995-02-06 | ||
| SE9500406A SE9500406L (en) | 1995-02-06 | 1995-02-06 | Device and method for coupling one or more wavelength channels to and from an optical fiber |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2211553A1 true CA2211553A1 (en) | 1996-08-15 |
Family
ID=20397088
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002211553A Abandoned CA2211553A1 (en) | 1995-02-06 | 1996-02-02 | Arrangement and method at an optical fibre |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0808473A1 (en) |
| JP (1) | JPH11501777A (en) |
| CA (1) | CA2211553A1 (en) |
| SE (1) | SE9500406L (en) |
| WO (1) | WO1996024871A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4105233B2 (en) * | 1996-10-10 | 2008-06-25 | ティコ テレコミュニケーションズ（ユーエス） インコーポレイティド | Method and apparatus for coupling insertion / extraction optical signal lines from a plurality of branch units |
| KR100206176B1 (en) * | 1996-12-03 | 1999-07-01 | 윤종용 | Optical attenuator and the manufacturing method thereof |
| GB2354895B (en) * | 1996-12-30 | 2001-06-13 | Furukawa Electric Europ Ltd | Isolated multiple grating system for filtering requirements |
| US6047096A (en) * | 1997-03-07 | 2000-04-04 | Telefonaktiebolaget Lm Ericsson | Optical device |
| EP0964275A1 (en) * | 1998-06-09 | 1999-12-15 | PIRELLI CAVI E SISTEMI S.p.A. | Method and device for dropping optical channels in an optical transmission system |
| JP4707399B2 (en) * | 2004-07-30 | 2011-06-22 | 富士通株式会社 | Optical add / drop device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5195161A (en) * | 1991-12-11 | 1993-03-16 | At&T Bell Laboratories | Optical waveguide comprising Bragg grating coupling means |
-
1995
- 1995-02-06 SE SE9500406A patent/SE9500406L/en not_active IP Right Cessation
-
1996
- 1996-02-02 JP JP8524186A patent/JPH11501777A/en active Pending
- 1996-02-02 WO PCT/SE1996/000121 patent/WO1996024871A1/en not_active Application Discontinuation
- 1996-02-02 CA CA002211553A patent/CA2211553A1/en not_active Abandoned
- 1996-02-02 EP EP96902554A patent/EP0808473A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| SE9500406D0 (en) | 1995-02-06 |
| WO1996024871A1 (en) | 1996-08-15 |
| SE503514C2 (en) | 1996-07-01 |
| SE9500406L (en) | 1996-07-01 |
| JPH11501777A (en) | 1999-02-09 |
| EP0808473A1 (en) | 1997-11-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |