EP1257858A1 - Wavelength controlled fbg filter - Google Patents
Wavelength controlled fbg filterInfo
- Publication number
- EP1257858A1 EP1257858A1 EP00975017A EP00975017A EP1257858A1 EP 1257858 A1 EP1257858 A1 EP 1257858A1 EP 00975017 A EP00975017 A EP 00975017A EP 00975017 A EP00975017 A EP 00975017A EP 1257858 A1 EP1257858 A1 EP 1257858A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- wavelength
- wavelengths
- fbg
- filter
- fibre
- 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.)
- Withdrawn
Links
- 239000000835 fiber Substances 0.000 claims abstract description 41
- 230000003287 optical effect Effects 0.000 claims abstract description 14
- 238000001914 filtration Methods 0.000 claims abstract description 6
- 239000013307 optical fiber Substances 0.000 abstract description 8
- 230000006835 compression Effects 0.000 abstract description 4
- 238000007906 compression Methods 0.000 abstract description 4
- 238000004806 packaging method and process Methods 0.000 description 6
- 238000005259 measurement Methods 0.000 description 4
- 230000002301 combined effect Effects 0.000 description 3
- 229910052761 rare earth metal Inorganic materials 0.000 description 3
- 150000002910 rare earth metals Chemical class 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 229910052691 Erbium Inorganic materials 0.000 description 2
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 230000004308 accommodation Effects 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
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
- G02B6/2932—With a cascade of diffractive elements or of diffraction operations comprising a directional router, e.g. directional coupler, circulator
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—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
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0201—Add-and-drop multiplexing
- H04J14/0202—Arrangements therefor
- H04J14/021—Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
- G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
- G02B6/02195—Refractive index modulation gratings, e.g. Bragg gratings characterised by means for tuning the grating
Definitions
- This invention relates to a controlled fiberoptic filtering system and use of this system, the system comprising at least one tunable FBG filter engraved into a first optical fibre, the FBG filter comprising a filter and a sensor grating with different wavelengths being inscribed in a chosen length of fibre, thus providing reflections at a first and a second wavelength, respectively.
- a Fibre Bragg Grating is a permanent, photo- induced periodic modulation of the refractive index in the core of an optical fibre, which reflects light within a narrow bandwidth centred at the Bragg wavelength, with negligible loss outside this wavelength band.
- the Bragg wavelength ⁇ B is given by:
- n av is the average refractive index seen by the light and ⁇ is the pitch of the grating.
- FBG filters can easily be wavelength tuned by changing the strain/compression or the temperature of the FBG, hence changing the average refractive index and the grating pitch [US patent 5, 007, 705, "Variable optical fibre Bragg filter arrangement" to W.W. Morey et.al.].
- Such wavelength tuneable FBG filters are expected to be central components in future reconfigurable/dynamic optical add/drop modules (OADMs) at add/drop nodes in the DWMD optical network, where one or more wavelength channels can be added and dropped, which will enable flexibility and fast accommodation of shifts in the traffic load, as well as rapid provisioning of services. [Lightwave, August 1999, "Advanced optical-networking components at the add/drop node"]
- OADMs reconfigurable/dynamic optical add/drop modules
- the invention also relates to a wavelength controlled FBG based fibre laser array comprising at least one tunable FBG based fibre laser.
- An FBG based fibre laser is a fibre laser where the laser feedback is provided by one (DFB laser) or two (DBR laser) FBGs imprinted in a section of an optical fibre doped with at least one of the rare earth materials, such as Erbium, which when optically pumped by a semiconductor laser provides gain in the rare earth doped fibre and consequently lasing at or close to the FBG Bragg wavelength.
- the gratings can be imprinted in fibres without any of the rare earths which are spliced to each end of a rare earth doped fibre.
- Such a laser can be continuously tuned by straining/compressing or heating the whole laser cavity [G. Ball and W.W. Morey, Optics Letters, Vol. 17, pp. 420-422, 1992] .
- the Bragg wavelength of a tuneable FBG filter has to be controlled with a high degree of stability, typically ⁇ 20pm over the whole tuning range, which can be up to tens of nanometres.
- a tuneable FBG filter For use in OADMs it is important to accurately tune and lock the tuneable FBG filters to the predetermined wavelengths (in the so-called ITU grid which has a spacing of 50GHz) .
- This is putting extreme requirements on the control of the FBG strain and temperature, which will depend on the actuator, the filter packaging and the fixing/positioning of the fibre.
- strain tuning the FBG can be tuned by fixing the fibre at each end of the grating and change the strain (or compression) of the FBG. This can for example be done by using piezoelectric actuators.
- the strain in the fibre has to be controlled within ca. 17 ⁇ strain (or the applied force to the fibre has to be controlled within ca. 15mN) .
- the corresponding accuracy in the positioning of the fixing points is ca. 0.3 ⁇ m. This is very demanding for any conventional actuator control.
- the object of the present invention is thus to provide a means for accurately controlling the wavelength of one or more wavelength multiplexed tuneable FBG filters, independently of drift and hysteresis in the actuator, the filter packaging and the fixing point of the fibre, as well as temperature drift.
- a further objective is to provide a means for accurately controlling the wavelength of one or more wavelength multiplexed tunable FBG based fibre lasers, independently of drift and hysterisis in the actuators, the laser packaging and the fixing point of the fibre, as well as temperature drift.
- the filter grating may be controlled using a sensor wavelength being different from the wavelength used for transmitting signals through the system, but which is reflected from the same FGB filter and therefore is subject to the same influences as the filter grating.
- the sensor wavelength does not influence the signals transmitted in the system and may easily be filtered out or removed.
- the preferred embodiment of the invention relates to a system using overlaid FBG gratings, e.g. as described in Xu, M.G., et.al., Electron. Lett., Vol. 30, pp. 1085-1087, 1994, involving two gratings, reflecting the filter and the sensor wavelengths, respectively.
- the sensor and filter gratings may, however, also be positioned side-by-side in each tuneable FBG filter.
- the system according to the preferred embodiment of the invention obtains a measure of the combined effect of strain, compression and temperature in the tuneable FBG filters, since the FBG sensors will see exactly the same strain and temperature as the tuneable FBG filters, and hence the Bragg wavelength of the sensor FBGs will be direct measures of the Bragg wavelength of the tuneable FBG filters, independently of drift and hysteresis in the actuator, the filter packaging and the fixing point of the fibre, as well as temperature drift.
- a wavelength controlled FBG based fibre laser array can be obtained by imprinting a second FBG inside each of the fibre laser cavities, with a Bragg wavelength outside the wavelength range preferentially outside the gain bandwidth of the lasers, hence not affecting the laser operation.
- the sensor FBGs will see exactly the same strain and temperature as the tunable FBG based fibre lasers.
- the laser wavelength can be determined with high accuracy by measuring the sensor FBG wavelengths.
- the measured sensor wavelengths can be used as input to the laser actuators to control the laser wavelengths with high accuracy.
- One advantage of this approach compared to measuring the laser wavelengths directly with an optical spectrum analyser is that the laser wavelengths can be controlled prior to turning on the lasers. Also the laser wavelengths can be controlled without tapping out laser light.
- Fig. 1 shows a preferred embodiment of the invention used in a reconfigurable OADM.
- Fig. 2 illustrates an FBG filter according to a preferred embodiment of the invention.
- Fig. 3 illustrates an FBG filter according to an Var embodiment of the invention.
- Fig. 4 shows an embodiment of the invention used to control the wavelengths of a tuneable FBG-based fibre laser array.
- the reconfigurable OADM shown in fig. 1 consists of a series of wavelength multiplexed, tuneable FBG filters 1 (here four) in an optical fibre 2 placed between two optical circulators 8.
- the tuneable FBG filters 1 can be strain tuned individually by means of actuators 3, for example piezoelectric actuators, to reflect one or more (here maximum 4) of the incoming wavelength multiplexed signal wavelengths 11 from the optical network 10 to the drop port 8, or to add one or more (here maximum 4) signal wavelengths 12 to the optical network at the add port 9.
- the add/drop ports 8,9 may be conventional optical circulators, e.g. as described in US patents 5.400.418 and 5.883.991, and will not be described in any detail here.
- FBG sensors 1 written in the 1300nm wavelength band (or alternatively in the 800nm wavelength band) in the same length of fibre as the tuneable FBG filters are used to measure the combined effect of strain and temperature in the tuneable FBG filters.
- the sensor gratings are overlaid or side-by-side as shown in figures 2 and 3, respectively, with the tuneable FBG filters .
- the Bragg wavelength of the sensor FBGs la will be direct measures of the Bragg wavelength of the tuneable FBG filters lb, independently of drift and hysteresis in the actuator, the filter packaging and the fixing point of the fibre, as well as temperature drift.
- the measured Bragg wavelengths are thus used to control the filter actuators 3 and lock the tuneable FBG filters 1 to the desired wavelengths .
- conventional actuator control 3 can be used to tune the FBG filters 1 to the desired wavelength channels and the FBG sensor measurements can be used to do the fine control and locking to the exact desired wavelengths.
- the 1300nm wavelength band FBG sensor wavelengths are measured by means of a wavelength readout unit 4 connected to the tuneable filters 1 via a 1300/1550nm WDM coupler 13.
- the 1300nm light passing the FBGs can be filtered out of the OADM by means of a second 1300/1550nm WDM coupler 14 e.g. comprising a fibre 15 having a dead end.
- the FBG sensors la will typically be written at different, non-overlapping wavelengths outside the wavelength band occupied by the DWDM system, not to interfere with the DWDM system.
- the DWDM system will operate at wavelength in the 1550nm wavelength band, while the FBG sensors la can be made to reflect wavelength in the 1300nm wavelength band (or possibly in the 800nm wavelength band) .
- the sensor FBGs la should have much narrower reflection spectrum than the tuneable FBG filters lb to allow high resolution Bragg wavelength measurements.
- a wavelength readout unit 4 including a broadband light source covering the FBG sensor la wavelengths, will be connected to the tuneable FBG 1 via an optical wavelength multiplexer.
- the measured FBG sensor wavelengths are compared with the desired FBG filter wavelengths and this information is used to control the actuators tuning the FBGs such that the FBG filter wavelengths are locked to the desired wavelengths.
- the readout unit 4 can in principle be any accurate spectrum analyser in combination with a broadband source (ELED) operating in the 1300nm wavelength range (or the 800nm wavelength band) , or alternatively an accurate tuneable source, covering the FBG sensor wavelengths, such as the read-out unit described in PCT application PCT/NO98/00031 to Kringlebotn et.al.
- the read-out unit 4 should be a simple device with low volume and low cost, such as the device described in the Norwegian patent application No. 1999.4473. With this device single or pairs of analysing FBG filters, corresponding to the individual sensor FBGs, are used to measure the sensor-, and hence the tuneable filter-Bragg wavelengths.
- the analysing FBG filters should then have Bragg wavelengths close to the sensor FBG wavelengths corresponding to the desired ITU wavelengths. This will minimise the required tuning of the analysing FBG filters, and greatly enhance the speed of the wavelength locking, which is important in reconfigurable OADMs.
- the measured FBG sensor wavelengths are compared with the desired FBG filter wavelengths in a signal processing unit 7 and this information is used to control the actuators 2 tuning the FBGs such that the FBG filter wavelengths are locked to the desired wavelengths.
- the control unit is provided with information 16 regarding the system, such as the required grating wavelengths in each filter grating, the wavelengths to be dropped or added to the system, and possibly calibration data for each actuator, as well as the information regarding the reflected sensor wavelengths provided from the wavelength readout unit 4.
- the tunable FBG-based fibre laser laser array shown in Fig. 4 consists of a series of wavelength multiplexed, tuneable FBG-based lasers 1' (here four) , preferentially Erbium-doped DFB fibre lasers operating in the 1.55 ⁇ m range (between 1.5 ⁇ m and 1.6 ⁇ m) , spliced into an optical fibre 2.
- the lasers are here pumped by one single pump laser 18, preferentially at 1480nm, through an optical isolator 19 and wavelength division multiplexer 13 which separates the laser wavelengths (and the pump laser wavelength) and the FBG sensor wavelengths.
- At the output of the laser array light within the sensor wavelength range is filtered out to a fibre 15 with a dead end by means of a second wavelength division multiplexer 14.
- the laser and pump light is directed through an optical isolator 20 to an erbium doped fibre 21 which is pumped by the residual pump power to provide amplification of the laser light.
- An optical isolator 22 is placed at the output of the amplifying fibre to isolate the laser system from feedback from an external system.
- the tunable fibre lasers can be strained tuned individually by means of actuators 3 to emit at the desired wavelengths.
- FBG sensors V written inside (or outside) the laser cavities, such that they are strained equally to the fibre lasers, at Bragg wavelengths outside the laser wavelength range, preferentially in the 1300nm band, are used to measure the combined effect of strain and temperature in the fibre lasers.
- a wavelength read out unit 4 including a broadband source covering the FBG sensor wavelengths, is connected to the tunable fibre laser, including the FBG sensors, via an optical fibre 6 and a wavelength multiplexer 13.
- the measured FBG sensor wavelengths are compared with the desired laser wavelengths in a signal processing control unit 7 and this information is used to control the actuators 3 tuning the lasers such that the laser wavelengths are locked to the desired wavelengths.
- the control unit is provided with information 16 regarding the desired laser wavelengths and the information 17 regarding the measured FBG sensor wavelengths.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Lasers (AREA)
- Optical Filters (AREA)
- Optical Communication System (AREA)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NO995485 | 1999-11-09 | ||
NO19995485A NO313606B1 (no) | 1999-11-09 | 1999-11-09 | Bolgelengdekontrollert FBG-filter |
PCT/NO2000/000377 WO2001035138A1 (en) | 1999-11-09 | 2000-11-08 | Wavelength controlled fbg filter |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1257858A1 true EP1257858A1 (en) | 2002-11-20 |
Family
ID=19903959
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP00975017A Withdrawn EP1257858A1 (en) | 1999-11-09 | 2000-11-08 | Wavelength controlled fbg filter |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1257858A1 (no) |
AU (1) | AU1312501A (no) |
NO (1) | NO313606B1 (no) |
WO (1) | WO2001035138A1 (no) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6389200B1 (en) * | 1999-12-28 | 2002-05-14 | Alcatel Usa Sourcing, L.P. | Wide tuning range fiber bragg grating filter (FBGF) using muscle wire |
DE60100503T2 (de) * | 2001-10-06 | 2004-06-09 | Agilent Technologies, Inc. (n.d.Ges.d.Staates Delaware), Palo Alto | Selbstjustierender verstimmbarer Filter |
AUPS096902A0 (en) * | 2002-03-07 | 2002-03-28 | Australian National University, The | Tuneable filter arrangement |
CN102610068A (zh) * | 2012-03-01 | 2012-07-25 | 昆明理工大学 | 一种基于光纤Bragg光栅的报警定位系统 |
CN102829810A (zh) * | 2012-08-21 | 2012-12-19 | 中国科学院半导体研究所 | 分布反馈式光纤激光器传感系统 |
GB2543806A (en) | 2015-10-29 | 2017-05-03 | Airbus Operations Ltd | Communication apparatus |
CN113983945B (zh) * | 2021-12-28 | 2022-03-22 | 南京牧镭激光科技有限公司 | 控制光纤光栅中心波长的传感器制作装置 |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5007705A (en) * | 1989-12-26 | 1991-04-16 | United Technologies Corporation | Variable optical fiber Bragg filter arrangement |
FR2731082B1 (fr) * | 1995-02-28 | 1997-04-04 | France Telecom | Multiplexeur optique a insertion-extraction utilisant des circulateurs optiques et des reseaux de bragg photoinscrits |
JP2985780B2 (ja) * | 1996-07-05 | 1999-12-06 | 日本電気株式会社 | 波長クロスコネクト装置 |
JPH10221552A (ja) * | 1997-02-07 | 1998-08-21 | Oki Electric Ind Co Ltd | 光波長フィルタおよび光波長選択ルータ |
US5982791A (en) * | 1998-01-14 | 1999-11-09 | Hewlett-Packard Company | Wavelength tracking in adjustable optical systems |
-
1999
- 1999-11-09 NO NO19995485A patent/NO313606B1/no not_active IP Right Cessation
-
2000
- 2000-11-08 AU AU13125/01A patent/AU1312501A/en not_active Abandoned
- 2000-11-08 EP EP00975017A patent/EP1257858A1/en not_active Withdrawn
- 2000-11-08 WO PCT/NO2000/000377 patent/WO2001035138A1/en active Application Filing
Non-Patent Citations (1)
Title |
---|
See references of WO0135138A1 * |
Also Published As
Publication number | Publication date |
---|---|
AU1312501A (en) | 2001-06-06 |
NO995485L (no) | 2001-05-10 |
WO2001035138A1 (en) | 2001-05-17 |
NO313606B1 (no) | 2002-10-28 |
NO995485D0 (no) | 1999-11-09 |
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