EP 1012645 B1

Europäisches Patentamt
(19)
European Patent Office
*EP001012645B1*
Office européen des brevets
(11)
EP 1 012 645 B1
EUROPEAN PATENT SPECIFICATION
(12)
(45) Date of publication and mention
(51) Int Cl.7:
of the grant of the patent:
18.09.2002 Bulletin 2002/38
G02B 6/28, G02B 6/34
(86) International application number:
PCT/GB98/01141
(21) Application number: 98917409.9
(87) International publication number:
(22) Date of filing: 20.04.1998
WO 98/048305 (29.10.1998 Gazette 1998/43)
(54) OPTICAL COUPLER AND/OR MULTIPLEXER
OPTISCHER KOPPLER UND/ODER MULTIPLEXER
COUPLEUR ET/OU MULTIPLEXEUR OPTIQUE
(84) Designated Contracting States:
(56) References cited:
DE FR GB IT
EP-A- 0 435 194
US-A- 5 170 450
WO-A-97/08574
(30) Priority: 21.04.1997 GB 9708045
11.08.1997 GB 9716970
(43) Date of publication of application:
28.06.2000 Bulletin 2000/26
(73) Proprietor: UNIVERSITY OF SOUTHAMPTON
Southampton, Hampshire SO17 1BJ (GB)
(72) Inventors:
• LAMING, Richard, Ian
Southampton,Hampshire SO31 4QZ (GB)
• DONG, Liang
Painted Post, NY 14870 (US)
(74) Representative: Haines, Miles John et al
• PATENT ABSTRACTS OF JAPAN vol. 011, no.
194 (P-588), 23 June 1987 -& JP 62 017709 A
(NIPPON TELEGR & TELEPH CORP), 26 January
1987,
• PATENT ABSTRACTS OF JAPAN vol. 011, no.
345 (P-636), 12 November 1987 -& JP 62 127807
A (FURUKAWA ELECTRIC CO LTD:THE), 10
June 1987,
• DONG L ET AL: "NOVEL ADD/DROP FILTERS
FOR WAVELENGHT-DIVISION-MULTIPLEXING
OPTICALFIBER SYSTEMS USING A BRAGG
GRATING ASSISTED MISMATCHED COUPLER"
IEEE PHOTONICS TECHNOLOGY LETTERS, vol.
8, no. 12, December 1996, pages 1656-1658,
XP000679542
EP 1 012 645 B1
D. Young & Co.
21 New Fetter Lane
London EC4A 1DA (GB)
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give
notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in
a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art.
99(1) European Patent Convention).
Printed by Jouve, 75001 PARIS (FR)
EP 1 012 645 B1
Description
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[0001] This invention relates to optical couplers and/or multiplexers.
[0002] Fused optical fibre couplers, in which two optical fibres are fused together at a coupling region, are known.
[0003] JP-A-62 017 709 and US-A-5 170 450 propose an optical fibre coupler having at least an m-core optical fibre
optically coupled to an n-core optical fibre, where m and n are positive integers and m is greater than 1.
[0004] In such a coupler, at least one of the fibres involved in the coupler has two or more light-transmitting cores.
[0005] In wavelength division multiplexed (WDM) optical transmission systems, multiple information channels are
transmitted at different respective wavelengths so that the channels can all be carried on a single waveguide (e.g. an
optical fibre).
[0006] There is a need in such systems for so-called channel-add multiplexers and so-called channel-drop demultiplexers (these two functions can be combined in a single channel add/drop multiplexer).
[0007] A channel add multiplexer is an optical device capable of receiving two optical signals - one generally being
a multi-channel WDM signal and the other generally being a new wavelength channel to be added to the WDM signal.
These two signals are received at respective input ports of the device, and a composite WDM signal comprising the
original WDM signal and the new wavelength channel is supplied at an output port of the device.
[0008] Similarly, in a channel drop demultiplexer, a multi-channel WDM signal is received at an input port of the
device. One or more of the wavelength channels of the WDM signal is separated from the others and is supplied at a
first output port, while the remainder of the WDM signal is supplied at another output port.
[0009] Figure 1 of the accompanying drawings schematically illustrates a previously proposed optical fibre channel
add/drop multiplexer having two input ports A1, A2 and two output ports A3, A4. The device comprises two optical
circulators 10, 20 and a fibre Bragg grating 30.
[0010] In Figure 1, a multi-channel WDM signal λIN is launched into port A1. A channel to be added, λADD, is launched
into port A4 and a channel λDROP to be separated from the WDM signal λIN is output at port A2. The WDM signal with
the channel λDROP dropped and the new channel λADD added is output at port A3.
[0011] The device works in a straightforward way. The Bragg grating is arranged to reflect light at the wavelength
λDROP of the channel to be dropped and the channel to be added. So, the channel to be dropped passes from the
circulator towards the grating, is reflected by the grating and is output by port A2 of the circulator. Similarly, the channel
to be added enters at port A4, passes from the circulator to the Bragg grating where it is reflected, and is output at port
A3 of the circulator. The remaining channels of the WDM signal, λOTHERS, are unaffected by the Bragg grating and so
emerge at port A3 of the circulator.
[0012] The device of Figure 1 makes good use of the wavelength-selective properties of a fibre Bragg grating, but
because the grating 30 is a two-port device the multiplexer needs the two circulators 10, 20. Circulators are expensive
bulk optical devices, so it is undesirable to use them in an all-fibre system. Also, there are inevitable losses caused by
the need to connect fibres to the bulk optical circulators. A simpler device could use two 50:50 fused fibre couplers,
but at the expense of an increased insertion loss of 6 dB (decibels) for the add/drop multiplexer.
[0013] This invention provides a channel drop demultiplexer comprising an optical fibre coupler having at least an
m-core optical fibre optically coupled to an n-core optical fibre, where m and n are positive integers and m is greater
than I in which:
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the fibres are coupled at a coupling region;
a grating is disposed on at least one core of the m-core fibre away from the coupling region;
a core of the m-core optical fibre to a first side of the coupling region provides an input port for a WDM signal;
that core of the m-core fibre, to a second side of the coupling region, provides an output port for a WDM signal; and
the grating promotes coupling of light of a chancel to be dropped between cores of the m-core fibre.
[0014] This invention also provides a channel add multiplexer comprising an optical fibre coupler having at least an
m-core optical fibre optically coupled to an n-core optical fibre, where m and n are positive integers and m is greater
than 1 in which:
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the fibres are coupled at a coupling region;
a grating is disposed on at least one core of the m-core fibre away from the coupling region;
a core of the m-core optical fibre to a first side of the coupling region provides an input port for a WDM signal;
that core of the m-core fibre, to a second side of the coupling region, provides an output port for a WDM signal; and
the grating promotes coupling of light of a channel to be added between cores of the m-core fibre.
[0015] In the invention a channel add multiplexer and a channel drop demultiplexer are provided which do not require
expensive and lossy bulk optical devices such as optical circulators but which do not introduce the insertion losses of
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conventional fused taper couplers.
[0016] Embodiments of the invention can provide away of selectively coupling light into or out of one core of the
more fibre. Embodiments of the invention can use established simple fused coupler techniques, and can introduce
very low (e.g. less than 1 dB) insertion losses for the coupled light.
[0017] An exemplary embodiment of the invention comprises a dual core fibre coupled to a single core fibre. If one
core of the dual core fibre is substantially identical (in terms of its optical propagation constants) to the core of the
single core fibre, light can be made to couple between that core of the dual core fibre and the single core fibre, whereas
light in the other core of the dual core fibre is essentially unaffected.
[0018] The insertion loss can be very low (e.g. < 1dB or even < 0.5 dB), which is much lower than the simple coupler
arrangement described in a paper by Bilodeau et al: IEEE Photonics Technology Letters, 7, 1995, pp388-390 and a
paper by Bakhti et al: Electronics Letters, 33, 1997, pp803-804. Compared to these prior an devices, embodiments of
the invention are not interferometric devices and so there is no need to balance optical path lengths within the devices
to a few wavelengths of the light. This makes embodiments of the invention much easier to manufacture.
[0019] Again, compared to the paper by Bakhti et al and also WO97/08574, the grating can be written over a length
of fibre instead of onto the waist of the coupler. this means that coupler manufacture and grating manufacture are
different processes which can reliably be done separately without affecting the other process. In any event, it is difficult
to produce a coupler waist of good uniformity over a long length, so any irregularities will affect the grating performance
and restricts the length and number of gratings which can be used in the prior art devices. In contrast, in the present
embodiments, multiple gratings can be used, of good quality because they are impressed onto fibre rather than onto
a coupler waist. Tuning of the gratings e.g. by compression or stretching is also possible, helped by the non-interferometric nature of the embodiments and the high physical strength of fibre away from the coupler waist.
[0020] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which:
Figure 1 schematically illustrates a previously proposed channel add/drop multiplexer;
Figures 2a and 2b schematically illustrate cross sections through optical fibres;
Figure 3 schematically illustrates a coupler formed of the fibres shown in Figures 2a and 2b;
Figure 4 schematically illustrates a channel drop demultiplexer using a coupler as shown in Figure 3;
Figure 5 schematically illustrates a channel add/drop multiplexer; and
Figure 6 schematically illustrates an optical transmission system.
[0021] Figures 2a and 2b schematically illustrate cross sections through two respective optical fibres used in the
devices described below.
[0022] Figure 2a illustrates a conventional single-mode optical fibre having a cladding region 40 surrounding a core
50. The core in this embodiment has a numerical aperture (NA) of 0.14, and is formed of boron and germanium doped
silica glass.
[0023] The fibre shown in Figure 2b has a cladding region 60 similar to the cladding 40 of the fibre of Figure 2a,
surrounding two cores 70, 80 disposed about 14 µm apart. The core 80 is substantially central in the fibre and has an
NA of 0.25 and is formed of phosphorus and germanium doped silica glass. The other core 70 is non-axial (off-centre),
has an NA of 0.14 and is formed of boron and germanium doped silica glass (i.e. it is similar to the core 50).
[0024] Accordingly, Figure 2a illustrates a single core (SC) fibre and Figure 2b illustrates a dual core (DC) fibre. The
two cores of the DC fibre are mismatched with respect to the other, although one of them is matched to the core of SC
fibre. One core of the DC fibre is also axial to facilitate easy connection to standard telecommunication fibre.
[0025] Figure 3 schematically illustrates a fused taper coupler formed by fusing together a length of DC fibre 100
and a length of SC fibre 110 at a coupling region 120. This forms a six-port device having ports B1..B6.
[0026] The transmission properties of this six-port device, when light is launched into any one of ports B1..B3, are
shown in the following tables:
Table 1
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Results measured at a wavelength of 1.51 µm
input port
output at port B4
output at port B5
output at port B6
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> 95%
< 1%
< 5%
2
< 1%
< 6%
> 94%
3
< 1%
> 96%
< 4%
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[0027]
The device of Figure 3 is symmetrical so the following results also apply:
Table 2
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input port
output at port B1
output at port B2
output at port B3
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> 95%
< 1%
< 5%
5
< 1%
< 6%
> 94%
6
< 1%
> 96%
< 4%
[0028] Thus, light launched into port B2 (the larger core of the DC fibre) emerges preferentially at port B6, whereas
light launched into port B1 (the smaller core of the DC fibre) emerges preferentially at port B4.
[0029] A number of uses can be envisaged for such a coupler. One such use. as part of a channel drop, a channel
add or a channel add/drop multiplexer, will be described below.
[0030] Figure 4 schematically illustrates a channel drop multiplexer comprising a coupler of the type shown in Figure
3 with a Bragg grating 130 impressed on one of the fibre cores using standard grating writing techniques. In the example
of Figure 4. the grating is impressed on the larger core of the DC fibre between the coupling region 120 and the port B5.
[0031] A WDM input signal having a range of wavelength channels (λIN) is launched into port B1. For those wavelengths unaffected by the Bragg grating (λOTHERS), the light emerges at port B4 according to the results shown in Table
1.
[0032] However, the grating 130 has the effect of coupling light, at the wavelength λDROP of a channel to be dropped,
from the core leading to port B4 (the central, narrower core of the DC fibre) into the core leading to port B5 (the wider,
off-centre core of the DC fibre) but in a reverse propagation direction. Accordingly, it is as though the light was entering
from port B5, and so according to Table 2 above, the dropped channel λDROP emerges from port B3.
[0033] The coupling condition for the grating 130 to have this effect is as follows:
2π
β 1 (λ) + β 2 (λ) = -----Λ
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where β1 and β2 are the propagation constants of the central core and the non-central core respectively.
[0034] The grating 130 can in fact be fabricated as a series arrangement of two or more gratings having different
periods or the same periods, so that two or more channels can be dropped by the same device and/or the dropped
channel can be "cleaned up" (attenuated) by a second grating at the same pitch.
[0035] The grating 130 is disposed in the off-centre core of the DC fibre, so that for wavelengths at which the grating
does not cause coupling from one fibre to another, the grating has little or no effect on the forward propagation of the
non-dropped channels λOTHERS. A particular resonance is at λ when
2π
2β 1 (λ) = -----Λ
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This will cause a reflection at λ back down the central core, therefore causing a loss for the channel at λ. By writing
the grating into the off-centre core, this reflection is reduced.
[0036] Figure 5 schematically illustrates a channel add/drop multiplexer formed, in effect. by a back-to-back arrangement of two couplers of the type shown in Figure 3 with a grating disposed on one of the cores between the two couplers.
[0037] The device of Figure 5 is an eight-port device having ports numbered C1..C8. The initial WDM signal is
launched into port C1, representing the central, narrower core of the DC fibre (equivalent to port B1 of the device of
Figure 3). A dropped channel λDROP emerges from port C3. A channel to be added, λADD is launched into port C8 and
the non-dropped channels of the original WDM signal (λOTHERS) along with the added channel λADD emerge from port
C6.
[0038] The channel dropping arrangement is identical to that shown in Figure 4. A grating 130' in the non-central
core of the DC fibre causes coupling from the central core into the non-central core, in a reverse direction at the
wavelength λDROP. This light is then coupled back to the port C3 as described above.
[0039] Similarly, the channel to be added, λADD, is launched into port C8. This is equivalent to light being launched
into port B6 of Figure 3, and from Table 2 it can be seen that the light emerges at port B2 of Figure 3, i.e. in the offcentre core of the DC fibre. Light propagating (from right to left as shown) in this core impinges on the grating 130',
which couples the light into a reverse-propagating (with respect to the original direction of the added channel) signal
in the central core. This reverse-propagating light (in fact, now propagating from left to right in Figure 5) emerges from
the port C6 of the device.
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[0040] The channels unaffected by the grating, λOTHERS, pass through both couplers and emerge from the port C6.
[0041] In other embodiments, the grating could be (or include) a chirped grating, such as a linearly chirped grating,
to give a similar response over a range of channels or to provide dispersion compensation.
[0042] Figure 6 schematically illustrates an optical transmission system using channel add/drop multiplexers of the
type shown in Figures 4 or 5.
[0043] In Figure 6, two optical transmitters 200, 210 at wavelengths λ1 and λ2 respectively are combined at a channel
add multiplexer 220. A further channel from as transmitter 230 (wavelength λ3) is added at a channel add multiplexer
240. The combined WDM signal then propagates through a length of fibre 250 before light at λ1 is removed by a channel
drop demultiplexer 260, to be received by an optical receiver 270. The remaining light continues to propagate to a
channel drop demultiplexer 270 which separates the wavelengths λ2 and λ3 for reception by respective receivers 280,
290.
[0044] While the embodiments described above have related to a 2 core fibre coupled to a 1 core fibre, in general
other numbers of cores can be used, so long as at least one fibre has more than one core. So, for example, a 3 core
fibre could be coupled to a 2 core fibre, and the grating could be impressed on a subset (possibly greater than 1) of
the cores of one fibre. Of course, if multi-core fibres are used some of the cores could be arranged as unconnected
"dummy" cores.
Claims
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1.
A channel drop demultiplexer comprising an optical fibre coupler having at least an m-core optical fibre (60) optically
coupled to an n-core optical fibre (40), where m and n are positive integers and m is greater than 1 in which:
the fibres are coupled at a coupling region;
a grating is disposed on at least one core of the m-core fibre away from the coupling region;
a core (80) of the m-core opt fibre to a first side of the coupling region provides an input port for a WDM signal;
that core of the m-core fibre, to a second side of die coupling region, provides an output port for a WDM signal;
and
the grating (30) promotes coupling of light of a channel to be dropped between cores of the m-core fibre.
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2.
A channel drop demultiplexer according to claim 1, in which
the grating is disposed in the m-core fibre to the second side of the coupling region, the grating promoting
reverse direction coupling of light of a channel to be dropped between cores of the m-core fibre; and
a core of the n-core fibre, to the first side of the coupling region provides an output port for the dropped
channel.
3.
A channel add multiplexer comprising an optical fibre coupler having at lease an m-core optical fibre (60) optically
coupled to an n-core optical fibre (40), where m and n are positive integers and m is greater than 1 in which:
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the fibres are coupled at a coupling region;
a grating is disposed on at least one core of the m-core fibre away from the coupling region;
a core of the m-core optical fibre to a first side of the coupling region provides an input port for a WDM signal;
that core of the m-core fibre, to a second side of the coupling region, provides an output port for a WDM signal;
and
the grating promotes coupling of light of a channel to be added between cores of the m-core fibre.
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4.
A channel add multiplexer according to claim 3, in which
the grating is disposed in the m-core fibre to the first side of the coupling region, the grating promoting reverse
direction coupling of light of a channel to be added between cores of the m-core fibre; and
a core of the n-core fibre, to the second side of the coupling region provides an input port for the channel to
be added.
5.
A channel add/drop multiplexer comprising:
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a channel drop demultiplexer according to claim 1 or claim 2;
series-connected with:
a channel add multiplexer according to claim 3 or claim 4.
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6.
A channel add/drop multiplexer according to claim 5, in which a common grating disposed between the channel
add multiplexer and the channel drop demultiplexer performs the function of the grating of the channel add multiplexer and the grating of the channel drop demultiplexer.
7.
A multiplexer or demultiplexer according to any one of the preceding claims, in which the grating comprises two
or more grating sections having different grating periods to promote optical coupling at different respective wavelengths.
8.
A multiplexer or demultiplexer according to any one of the preceding claims, in which the grating comprises two
or more grating sections having substantially identical grating periods.
9.
A multiplexer or demultiplexer according to any one of the preceding claims, in which the cores (70,80) of the mcore fibre have different propagation constants.
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10. A multiplexer or demultiplexer according to any one of the preceding claims, in which m=2 and n=1.
11. A multiplexer or demultiplexer according to any one of the preceding claims, in which one of the cores (70) of the
m-core fibre has a propagation constant substantially identical to the propagation constant of a core (50) of the ncore fibre.
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12. A multiplexer or demultiplexer according to any one of the preceding claims, in which the or each grating (130)
comprises a periodic refractive index variation.
13. A multiplexer or demultiplexer according to claim 12, in which the or a grating (130) comprises a chirped grating.
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14. A multiplexer or demultiplexer according to claim 13, in which the or a grating (130) comprises a linearly chirped
grating.
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15. A multiplexer or demultiplexer according to any one of the preceding claims, in which one of the cores (80) of the
m-core optical fibre is disposed substantially axially within the m-core fibre (60), the or each grating being impressed
on another of the cores (70) of the m-core fibre.
16. A multiplexer or demultiplexer according to any one of the preceding claims, in which the fibres are fused together
at the coupling region.
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17. A multiplexer or demultiplexer according to any one of the preceding claims, in which the or each grating is impressed on the core (70) of the m-core fibre having a propagation constant substantially identical to the propagation
constant of a core of the n-core fibre.
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18. An optical transmission system comprising a multiplexer or demultiplexer according to any one of che precoding
claims.
19. A wavelength-division-multiplexed optical transmission system comprising two or more series-connected multiplexers according to any one of claims 3 to 8, each multiplexer being arranged to add one or more respective
wavelength channels to a wavelength-division-multiplexed optical signal.
20. A wavelength-division-multiplexed optical transmission system comprising two or more series-connected demultiplexers according to claims 1, 2, 5, 6, 7 or 8, each demultiplexer being arranged to remove one or more respective
wavelength channels from a wavelength-division-multiplexed optical signal.
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21. A method of wavelength division demultiplexing, comprising:
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providing an optical fiber coupler having at least an m-core optical fiber (60) optically coupled to an n-core
optical fiber (40), where m and n are positive integers and m is greater than 1;
coupling the m-core optical fiber and the n-core optical fiber at a coupling region;
disposing a grating (30) on at least one core of the m-core fiber away from the coupling region;
providing an input port for a WDM signal, said input port being formed by a portion of a core (80) of the mcore optical fiber arranged at a first side of the coupling region;
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providing an output port for a WDM signal, said output port being formed by a further portion of said core of
the m-core optical fiber arranged to a second side of the coupling region; and
coupling light of a channel to be dropped between cores of the m-core fiber with the grating, thereby to perform
channel drop demultiplexing.
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22. A method of wavelength division multiplexing, comprising:
providing an optical fiber coupler having at least an m-core optical fiber (60) optically coupled to an n-core
optical fiber (40), where m and n are positive integers and m is greater than 1;
coupling the m-core optical fiber and the n-core optical fiber at a coupling region;
disposing a grating on at least one core of the m-core fiber away from the coupling region;
providing an input port for a WDM signal, said input port being formed by a portion of a core of the m-core
optical fiber arranged at a first side of the coupling region;
providing an output port for a WDM signal, said output port being formed by a further portion of said core of
the m-core optical fiber arranged to a second side of the coupling region; and
coupling light of a channel to be added between cores of the m-core fiber with the grating, thereby to perform
channel add multiplexing.
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Patentansprüche
1.
Kanal-Drop-Demultiplexer, der einen Glasfaserkoppler aufweist, mit zumindest einer Glasfaser (60) mit m Kernen,
die optisch mit einer Glasfaser (40) mit n Kernen gekoppelt ist, wobei m und n positive ganze Zahlen sind und m
größer als 1 ist, in dem
die Fasern in einer Kopplungsregion gekoppelt sind,
ein Gitter von der Kopplungsregion entfernt an zumindest einem Kern der Faser mit m Kernen angeordnet ist,
ein Kern (80) der optischen Faser mit m-Kernen einen Eingangsanschluß für ein WDM-Signal an der ersten Seite
der Kopplungsregion zur Verfügung stellt,
wobei dieser Kern der m-Kern-Faser an einer zweiten Seite der Kopplungsregion einen Ausgangsanschluß für
ein WDM-Signal zur Verfügung stellt und
das Gitter (30) das Koppeln des Lichtes des abzusetzenden bzw. auszukoppelnden Kanals zwischen den Kernen
der Faser mit m Kernen unterstützt.
2.
Kanal-Drop-Demultiplexer nach Anspruch 1, in dem
das Gitter an der zweiten Seite der Kopplungsregion in der Faser mit m Kernen angeordnet ist, wobei das Gitter
das Einkoppeln von Licht eines abzusetzenden bzw. auszukuppelnden Kanals in umgekehrter Richtung zwischen
den Kernen der Faser mit m Kernen unterstützt und
ein Kern der Faser mit n Kernen einen Ausgangsanschluß für den abgesetzten bzw. ausgekoppelten Kanal an der
ersten Seite der Kopplungsregion zur Verfügung stellt.
3.
Ein Kanal-Add-Multiplexer, der einen Glasfaserkoppler mit zumindest einer Glasfaser mit m Kernen (60) aufweist,
die optisch mit einer Glasfaser mit n Kernen (40) gekoppelt ist,
wobei m und n positive ganze Zahlen sind und m größer als 1 ist, in dem
die Fasern in einer Kopplungsregion gekoppelt sind,
ein Gitter an zumindest einem Kern der Faser mit m Kernen von der Kopplungsregion entfernt angeordnet ist,
ein Kern der Glasfaser mit m Kernen an einer ersten Seite der Kopplungsregion einen Eingangsanschluß für ein
WDM-Signal zur Verfügung stellt,
wobei dieser Kern der Faser mit m Kernen an einer zweiten Seite der Kopplungsregion einen Ausgangsanschluß
für ein WDM-Signal zur Verfügung stellt und
das Gitter das Koppeln des Lichtes eines Kanals, der zwischen den Kernen der Faser mit m Kernen aufgenommen
bzw. eingekoppelt werden soll, unterstützt.
4.
Ein Kanal-Add-Multiplexer nach Anspruch 3, in dem
das Gitter an einer ersten Seite der Kopplungsregion in der Faser mit m Kernen angeordnet ist, wobei das Gitter
das Koppeln von Licht eines Kanals, der zu den Kernen der Faser mit m Kernen zugefügt werden soll, in umgekehrter Richtung unterstützt, und
ein Kern der Faser mit m Kernen an der zweiten Seite der Kopplungsregion einen Eingangsanschluß für den
hinzuzufügenden Kanal zur Verfügung stellt.
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5.
Ein Kanal-Add-/Drop-Multiplexer, der aufweist:
einen Kanal-Drop-Demultiplexer gemäß Anspruch 1 oder Anspruch 2, der in Reihe geschaltet ist mit
einem Kanal-Add-Multiplexer gemäß Anspruch 3 oder Anspruch 4.
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6.
Ein Kanal-Add-/Drop-Multiplexer gemäß Anspruch 5, in dem ein gemeinsames Gitter, das zwischen dem KanalAdd-Multiplexer und dem Kanal-Drop-Demultiplexer angeordnet ist, die Funktion des Gitters des Kanal-Add-Multiplexers und des Gitters des Kanal-Drop-Demultiplexers ausübt.
7.
Ein Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in dem das Gitter zwei oder mehrere
Gittersektionen mit unterschiedlichen Gitterperioden hat, um das optische Koppeln bei unterschiedlichen jeweiligen Wellenlängen zu unterstützen.
8.
Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in dem das Gitter zwei oder mehrere Gittersektionen mit im wesentlichen identischen Gitterperioden hat.
9.
Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in dem die Kerne (70, 80) der Faser mit m
Kernen unterschiedliche Wellenübertragungsfaktoren haben.
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15
20
10. Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in denen m = 2 und n = 1.
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11. Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in dem einer der Kerne (70) der Faser mit
m Kernen einen Wellenübertragungsfaktor bzw. eine Übertragungskonstante hat, die im wesentlichen gleich zu
der Übertragungskonstante eines Kerns (50) der n-Kern-Faser ist.
12. Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in dem das Gitter oder jedes Gitter (130)
eine periodische Brechungsindexvariation aufweist.
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13. Multiplexer oder Demultiplexer nach Anspruch 12, in dem das Gitter oder ein Gitter (130) ein gechirptes Gitter
bzw. ein Gitter mit einer ortsabhängigen Gitterperiode aufweist.
14. Ein Multiplexer oder Demultiplexer nach Anspruch 13, in dem das Gitter oder ein Gitter (130) ein linear gechirptes
Gitter bzw. ein Gitter mit linear ortsabhängiger Gitterperiode aufweist.
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15. Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in dem einer der Kerne (80) der optischen
Faser mit m Kernen im wesentlichen axial innerhalb der m-Kern-Faser (60) angeordnet ist, wobei das Gitter oder
jedes Gitter auf einem anderen der Kerne (70) der m-Kern-Faser aufgeprägt ist.
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16. Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in der die Fasern in der Kopplungsregion
aneinander fixiert sind.
17. Ein Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche, in dem das Gitter oder jedes Gitter auf
dem Kern (70) der m-Kern-Faser vorgegeben ist, der eine Übertragungskonstante hat, die im wesentlichen gleich
der Übertragungskonstante eines Kerns der n-Kern-Faser ist.
18. Optisches Übertragungssystem, das einen Multiplexer oder Demultiplexer nach einem der vorherigen Ansprüche
aufweist.
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19. Ein optisches Wellentängenmultiplex-Übertragungssystem, das zwei oder mehrere in Reihe verbundene Multiplexer nach einem der Ansprüche 3 bis 8 aufweist, wobei jeder Multiplexer angeordnet ist, um einen oder mehrere
entsprechende Wellenlängenkanäle zu einem optischen Wellenlängenmultiplex-Signal hinzuzufügen.
20. Optisches Wellenlängenmultiplex-Übertragungssystem, das zwei oder mehrere in Reihe geschaltete Demultiplexer nach einem der Ansprüche 1, 2, 5, 6, 7 oder 8 aufweist, wobei jeder Demultiplexer angeordnet ist, um ein oder
mehrere entsprechende Wellenlängenkanäle aus einem optischen Wellenlängenmultiplex-Signal zu entfernen.
21. Verfahren des Wellenlängen-Demultiplexen, das aufweist:
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das Zurverfügungstellen eines Glasfaserkopplers mit zumindest einer Glasfaser mit m Kernen (60), die optisch
an eine n-Kern-Glasfaser (40) gekoppelt ist, wobei m und n positive ganze Zahlen sind und m größer als 1 ist,
das Koppeln der m-Kern-Glasfaser mit der n-Kern-Glasfaser in einer Kopplungsregion,
5
das Anordnen eines Gitters (30) an zumindest einem Kern der m-Kern-Faser von der Kopplungsregion entfernt,
das Zurverfügungstellen eines Eingangsanschlusses für eine WDM-Signal, wobei der Eingangsanschluß von
einem Abschnitt eines Kernes (80) der m-Kernglas-Faser gebildet wird, der an einer ersten Seite der Kopplungsregion angeordnet ist,
10
das Zurverfügungstellen eines Ausgangsanschlusses für ein WDM-Signal, wobei der Ausgangsanschluß von
einem weiteren Abschnitt des Kerns der m-Kern-Glasfaser gebildet wird, die an einer zweiten Seite der Kopplungsregion angeordnet ist, und
15
das Koppeln von Licht eines abzusetzenden Kanals zwischen Kernen der m-Kern-Faser mit dem Gitter, wodurch das Kanal-Drop-Demultiplexing durchgeführt wird.
20
22. Verfahren zum Wellenlängenmultiplexen, das aufweist:
das Zurverfügungstellen eines optischen Faserkopplers mit zumindest einer optischen Faser mit m Kernen
(60), die mit einer optischen Faser mit n Kernen (40) optisch gekoppelt ist, wobei m und n positive ganze
Zahlen sind und m größer als 1 ist,
25
das Koppeln der optischen Faser mit m-Kernen und der optischen Faser mit n-Kernen in einer Kopplungsregion,
das Anordnen eines Gitter an zumindest einem Kern der m-Kern-Faser von der Kopplungsregion entfernt,
30
das Zuverfügungstellen eines Eingangsanschlusses für ein WDM-Signal, wobei der Eingangsanschluß von
einem Abschnitt eines Kerns der optischen m-Kern-Faser gebildet wird, der an einer ersten Seite der Kopplungsregion angeordnet ist,
das Zurverfügungstellen eines Ausgangsanschlusses für ein WDM-Signal, wobei der Ausgangsanschluß von
einem weiteren Abschnitt des Kerns der optischen m-Kern-Faser gebildet wird, der an einer zweiten Seite der
Kopplungsregion angeordnet ist, und
35
das Koppeln von Licht eines zu den Kernen der m-Kern-Faser hinzuzufügenden Kanals mit dem Gitter, wodurch das Kanal-Add-Multiplexing durchgeführt wird.
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Revendications
45
1.
Démultiplexeur à abandon de canal comprenant un coupleur de fibres optiques comportant au moins une fibre
optique à m coeurs (60) couplée optiquement à une fibre optique à n coeurs (40), m et n étant des entiers positifs
et m étant supérieur à 1, dans lequel :
les fibres sont couplées dans une région de couplage ;
un réseau de diffraction est disposé sur au moins un coeur de la fibre à m coeurs, loin de la région de couplage ;
un coeur (80) de la fibre optique à m coeurs d'un premier côté de la région de couplage procure un point
d'entrée pour un signal multiplexé par division de longueur d'onde ;
ce coeur de la fibre à m coeurs, d'un deuxième côté de la région de couplage, procure un point de sortie pour
un signal multiplexé par division de longueur d'onde ; et
le réseau de diffraction (30) favorise le couplage de la lumière d'un canal à abandonner entre les coeurs de
la fibre à m coeurs.
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2.
Démultiplexeur à abandon de canal selon la revendication 1, dans lequel :
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le réseau de diffraction est disposé dans la fibre à m coeurs du deuxième côté de la région de couplage, le
réseau de diffraction favorisant le couplage en sens inverse de la lumière d'un canal à abandonner entre les
coeurs de la fibre à m coeurs ; et
un coeur de la fibre à n coeurs, du premier côté de la région de couplage, procure un point de sortie pour le
canal abandonné.
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3.
Multiplexeur de rajout de canal comprenant un coupleur de fibres optiques comportant au moins une fibre optique
à m coeurs (60) optiquement couplée à une fibre optique à n coeurs (40), m et n étant des entiers positifs et m
étant supérieur 1, dans lequel :
10
les fibres sont couplées dans une région de couplage ;
un réseau de diffraction est disposé sur au moins un coeur de la fibre à m coeurs, loin de la région de couplage ;
un coeur de la fibre optique à m coeurs d'un premier côté de la région de couplage procure un point d'entrée
pour un signal multiplexé par division de longueur d'onde ;
ce coeur de la fibre à m coeurs, d'un deuxième côté de la région de couplage, procure un point de sortie pour
un signal multiplexé par division de longueur d'onde ; et
le réseau de diffraction favorise le couplage de la lumière d'un canal devant être ajouté entre les coeurs de
la fibre à m coeurs.
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20
4.
Multiplexeur à rajout de canal selon la revendication 3, dans lequel :
le réseau de diffraction est disposé dans la fibre à m coeurs du premier côté de la région de couplage, le
réseau de diffraction favorisant le couplage en sens inverse de la lumière d'un canal à rajouter entre les coeurs
de la fibre à m coeurs ; et
un coeur de la fibre à n coeurs, du deuxième côté de la région de couplage, procure un point d'entrée pour le
canal à rajouter.
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5.
Multiplexeur à rajout/abandon de canal, comprenant :
un démultiplexeur à abandon de canal selon la revendication 1 ou la revendication 2 ;
connecté en série avec :
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un multiplexeur à rajout de canal selon la revendication 3 ou la revendication 4.
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6.
Multiplexeur à rajout/abandon de canal selon la revendication 5, dans lequel un réseau de diffraction commun
disposé entre le multiplexeur à rajout de canal et le démultiplexeur à abandon de canal assure la fonction du
réseau de diffraction du multiplexeur à rajout de canal et du réseau de diffraction du démultiplexeur à abandon de
canal.
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7.
Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel le réseau de
diffraction comprend deux ou plusieurs sections de réseau de diffraction ayant des périodes de réseau de diffraction
différentes pour favoriser un couplage optique à des longueurs d'onde respectives différentes.
8.
Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel le réseau de
diffraction comprend deux ou plusieurs sections de réseau de diffraction ayant des périodes de réseau de diffraction
sensiblement identiques.
9.
Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel les coeurs
(70, 80) de la fibre à m coeurs ont des constantes de propagation différentes.
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50
10. Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel m = 2 et n = 1.
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11. Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel l'un des
coeurs (70) de la fibre à m coeurs a une constante de propagation sensiblement identique à la constante de
propagation d'un coeur (50) de la fibre à n coeurs.
12. Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel le réseau de
diffraction ou chaque réseau de diffraction (130) comporte une variation d'indice de réfraction périodique.
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13. Multiplexeur ou démultiplexeur selon la revendication 12, dans lequel le réseau de diffraction ou un réseau de
diffraction (130) comprend un réseau de diffraction fluctuant.
5
14. Multiplexeur ou démultiplexeur selon la revendication 13, dans lequel le réseau de diffraction ou un réseau de
diffraction (130) comprend un réseau de diffraction fluctuant de façon linéaire.
10
15. Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel l'un des
coeurs (80) de la fibre optique à m coeurs est disposé sensiblement axialement à l'intérieur de la fibre à m coeurs
(60), le réseau de diffraction ou chaque réseau de diffraction étant imprimé sur un autre des coeurs (70) de la fibre
à m coeurs.
16. Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel les fibres sont
fondues les unes aux autres dans la région de couplage.
15
17. Multiplexeur ou démultiplexeur selon l'une quelconque des revendications précédentes, dans lequel le réseau de
diffraction ou chaque réseau de diffraction est imprimé sur le coeur (70) de la fibre à m coeurs ayant une constante
de propagation sensiblement identique à la constante de propagation d'un coeur de la fibre à n coeurs.
20
18. Système de transmission optique comprenant un multiplexeur ou un démultiplexeur selon l'une quelconque des
revendications précédentes.
25
19. Système de transmission optique multiplexé par division de longueur d'onde comprenant deux ou plusieurs multiplexeurs connectés en série selon l'une quelconque des revendications 3 à 8, chaque multiplexeur étant configuré
de façon à ajouter un ou plusieurs canaux de longueur d'onde respectifs à un signal optique multiplexé par division
de longueur d'onde.
30
20. Système de transmission optique multiplexé par division de longueur d'onde comprenant deux ou plusieurs démultiplexeurs connectés en série selon les revendications 1, 2, 5, 6, 7 ou 8, chaque démultiplexeur étant configuré
de façon à retirer un ou plusieurs canaux de longueur d'onde respectifs d'un signal optique multiplexé par division
de longueur d'onde.
21. Procédé de démultiplexage par division de longueur d'onde, comprenant :
35
40
45
la disposition d'un coupleur de fibres optiques comportant au moins une fibre optique à m coeurs (60) optiquement couplée à une fibre optique à n coeurs (40), m et n étant des entiers positifs et m étant supérieur à 1 ;
le couplage de la fibre optique à m coeurs et de la fibre optique à n coeurs dans une région de couplage ;
la disposition d'un réseau de diffraction (30) sur au moins un coeur de la fibre à m coeurs, loin de la région
de couplage ;
la disposition d'un point d'entrée pour un signal multiplexé par division de longueur d'onde, ledit point d'entrée
étant formé par une partie d'un coeur (80) de la fibre optique à m coeurs disposée d'un premier côté de la
région de couplage ;
la disposition d'un point de sortie pour un signal multiplexé par division de longueur d'onde, ledit point de sortie
étant formé par une autre partie dudit coeur de la fibre optique à m coeurs disposée d'un deuxième côté de
la région de couplage ; et
le couplage de la lumière d'un canal à abandonner entre les coeurs de la fibre à m coeurs au réseau de
diffraction, de façon à effectuer par conséquent un démultiplexage à abandon de canal.
22. Procédé de multiplexage par division de longueur d'onde, comprenant :
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55
la disposition d'un coupleur de fibres optiques comportant au moins une fibre optique à m coeurs (60) optiquement couplée à une fibre optique à n coeurs (40), m et n étant des entiers positifs et m étant supérieur à 1 ;
le couplage de la fibre optique à m coeurs et de la fibre optique à n coeurs dans une région de couplage ;
la disposition d'un réseau de diffraction sur au moins un coeur de la fibre à m coeurs, loin de la région de
couplage ;
la disposition d'un point d'entrée pour un signal multiplexé par division de longueur d'onde, ledit point d'entrée
étant formé par une partie d'un coeur de la fibre optique à m coeurs disposée d'un premier côté de la région
de couplage ;
la disposition d'un point de sortie pour un signal multiplexé par division de longueur d'onde, ledit point de sortie
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EP 1 012 645 B1
étant formé par une autre partie dudit coeur de la fibre optique à m coeurs disposée d'un deuxième côté de
la région de couplage ; et
le couplage de la lumière d'un canal à rajouter entre les coeurs de la fibre à m coeurs au réseau de diffraction,
de façon à effectuer par conséquent un multiplexage à rajout de canal.
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