GB2191013A - Tunable optical fibre filters - Google Patents

Tunable optical fibre filters Download PDF

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Publication number
GB2191013A
GB2191013A GB08612782A GB8612782A GB2191013A GB 2191013 A GB2191013 A GB 2191013A GB 08612782 A GB08612782 A GB 08612782A GB 8612782 A GB8612782 A GB 8612782A GB 2191013 A GB2191013 A GB 2191013A
Authority
GB
United Kingdom
Prior art keywords
fibres
couplings
filter according
filter
biconical
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.)
Granted
Application number
GB08612782A
Other versions
GB8612782D0 (en
GB2191013B (en
Inventor
Anthony Christos Boucouvalas
George Antony Georgiou
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co PLC
Original Assignee
General Electric Co PLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by General Electric Co PLC filed Critical General Electric Co PLC
Priority to GB8612782A priority Critical patent/GB2191013B/en
Publication of GB8612782D0 publication Critical patent/GB8612782D0/en
Publication of GB2191013A publication Critical patent/GB2191013A/en
Application granted granted Critical
Publication of GB2191013B publication Critical patent/GB2191013B/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
    • G02B6/29395—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device configurable, e.g. tunable or reconfigurable
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2821—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals
    • G02B6/2835—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals formed or shaped by thermal treatment, e.g. couplers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29346—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 wave or beam interference
    • G02B6/2935—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means
    • G02B6/29352—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means in a light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/21—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  by interference
    • G02F1/225—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  by interference in an optical waveguide structure
    • G02F1/2252—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  by interference in an optical waveguide structure in optical fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/29—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
    • G02F1/31—Digital deflection, i.e. optical switching
    • G02F1/313—Digital deflection, i.e. optical switching in an optical waveguide structure
    • G02F1/3131—Digital deflection, i.e. optical switching in an optical waveguide structure in optical fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/0147—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on thermo-optic effects

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Nonlinear Science (AREA)
  • Light Guides In General And Applications Therefor (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

A Mach-Zehnder interferometer comprises two single mode optical fibres 2,3 similarly coupled together at two or more closely-spaced regions by means of biconical couplings, and means 5,6 are provided for heating at least one of the fibres between two couplings in a controlled manner so as to produce an optical phase-shift of light propagating in the fibre. <IMAGE>

Description

SPECIFICATION Tunable optical fibre filters This invention relates to tunable filters utilising single mode optical fibres coupled to provide a Mach Zehnder interferometer.
According to the invention two single mode optical fibres are similarly coupled together at two or more closely spaced regions by means of biconical couplings, and means are provided for heating one or other of the fibres between two couplings.
Biconical couplings are themselves known for multimode fibres, and are formed by twisting the fibres together and heating the twisted region of the fibre to a temperature sufficient to cause them to fuse together whilst at the same time applying a controlled tension to the fibres to produce a predetermined stretching of the fibres, and this technique is employed for forming the couplings in a device in accordance with the invention.
The degree of stretching will depend upon the form of coupling required, and may be such as to provide a power splitting ratio of 1:1 or to give 100% switching. The term "closely spaced" means that the coupling regions are not more than 10cm apart, the spacing preferably being less than 5cm.
The invention provides an all fibre Mach Zehnder interferometer (MZI), which because of the equal arms set close together provides a very stable device.
Heating can be effected by providing on one or both fibres a thin layer of high resistivity material and passing an electric current therethrough.
The invention will now be further explained by way of example with reference to Figures 1 to 6 of the accompanying drawings, in which Figure 1 illustrates diagrammatically one form of filter in accordance with the invention, and the preferred method of fabrication, Figure 2 represents the output power/voltage characteristic for a particular wavelength of the filter, Figure 3 illustrates the manner of varying the pass band of the filter, Figures 4 and 5 illustrate variations in wavelength attainable by the filter, and Figure 6 illustrates a further form of filter.
Referring first to Figure 1, this shows the preferred fabrication process used to form one filter in accordance with the invention. In this process a first coupler 1 is formed in a pair of fibres 2, 3 which are stretched by the usual method, whilst being heated by an oxybutane flame from a burner 4, but by an amount such as to produce total switching. All power will then be transferred to the coupled arm. The second coupler is made a few centimetres along the fibres, and is also stretched for total power transfer. All power will now be the straight through arm. Such a technique ensures individual coupler fabrication control.
In a second method a first coupler 1 is formed as described previously, but is stretched by an amount such as to produce 50% switching as opposed to 100% as indicated in Figure 1b. The second coupler is sim ilarly fabricated as described-above, and stretched to a desired length a longer stretching resulting in a narrower pass band, as explained below.
In each case both arms of the filter between the coupler are coated individually with a thin layer 5 of high resistivity material. Electrodes, represented diagrammatically at 6, are connected to the ends of the layer on one arm and the device is encapsulated in a protective medium shown diagrammatically at 7 forming an enclosing box with the two electrodes connected to external terminals on the box. The protective medium may, for example, comprise a thermosetting resin.
The filter can be used as an MZI. For a single wavelength input in one arm of the MZI, e.g into the left hand end of the fibre 2 as shown in Figure 1c, and on the application of a voltage between the electrodes 6, a current, I, flows through the resistive material, hence dissipating heat 12RH, where RH is the resistance of the material. The heat causes refractive index and dimensional changes to the fibre and hence an optical phase shift to the light propsgating in the fibre, and switching takes place, due to the thermo-optic effect in silica.
The device is hence an electrically tunable MZI, and 100% tunability is possible by the application of a suitable voltage across the microheater. Figure 2 shows the output power versus voltage characteristic for a specific wavelength of such a device. The wavelength transmission of such a device is hence a function of the applied voltage on the microheater, as well as on the individual coupler fabrication.
The filter bandwidth is, however, a function of the couplers' properties only. The bandwidth can be controlled in the following manner, during the fabrication of the MZI.
When the first and second couplers are made, usually the taper process is stopped at the first equal power crossing point (Fig. 3). This results in a coupler with a relatively broad pass band A 250nm or more. To obtain a much narrower pass band the couplers are stretched during fabrication to successive equal power points, i.e B, C, ... of Figure 3.
This results in a MZI device of a narrow oscillating pass band wavelength transmission characteristic.
It has been found that the wavelength response of the interferometer is the product of the wavelength responses of the individual couplers. The phase shifter is simply shifting the wavelength response of the second coupler. Knowledge of the wavelength response of the individual couplers would, therefore, allow the tunability characteristics of the interferometer to be predicted.
It has also been found that the best results for tunability are achieved when the first coupler is tapered at points A or A' in Figure 3 (depending on the fabrication method used).
This gives a broad wavelength for the first coupler. The second coupler can be made to stop at points B', C', etc, depending on how narrow the pass band need be. The narrower the pass band the longer we have to stretch the second coupler. Tunability is achieved by applying a voltage to one of the micro-heaters 5 in order to heat the respective arm and thereby obtain a degree of phase shift. A device made this way has shown a wavelength response as in Figure 4, when no voltage is applied to the phase shifter.
On application of a voltage equivalent to a power of 26mW shifted the wavelength response to that of Figure 5, clearly indicating the tunability of the method.
Further, the pass band can be reduced even further, by cascading more than two couplers 7, 8, 9 in series, as shown in Fig. 6, with a pair of microheaters 5 between them. Tuning of the pass band peak can be achieved by controlling the voltage across the micro-heaters. Very narrow pass band can be achieved this way, typically c 10nm.
This device has the following advantages.
1. It has a wavelength transmission characteristic which can be electrically tuned.
2. The pass band width can be narrow.
3. It is compact.
4. It has an all fibre construction with low losses.

Claims (7)

1. A tunable optical fibre filter comprising two single mode optical fibres coupled together at two or more closely spaced regions by means of biconical couplings, and means for heating at least one of the fibres between two couplings.
2. A filter according to Claim 1 incorporating a layer of high resistivity material on at least one of the fibres between the two couplings and means for passing an electric current through the layer to effect the heating of the fibre.
3. A filter according to Claim 1 incorporating on the fibres between the two couplings substantially identical layers of high resistivity material, and means for passing an electric current through at least one of the layers for heating the respective fibre.
4. A filter according to any preceding Claim wherein the couplings and the parts of the fibres between them are encapsulated within a protective medium.
5. A filter according to Claim 4 wherein the protective medium comprises a thermosetting resin.
6. A filter according to any preceding Claim wherein the biconical coupling at the input end of the filter has a broader pass band characteristic than the second or any subsequent coupling.
7. A filter according to any preceding claim wherein the fibres are coupled together at more than two closely spaced regions by means of biconical couplings, and means are provided for introducing a phase shift in the fibres between each adjacent pair of couplings.
7. A filter according to any preceding Claim wherein the fibres are coupled together at more than two closely spaced regions by means of biconical couplings, and means are provided for heating at least one of the fibres between each adjacent pair of couplings.
8. A tunable optical fibre filter substantially as shown in and as hereinbefore described with reference to Figure 1 or 6 of the accompanying drawings.
CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1-7 above have been deleted or textually amended.
New or textually amended claims have been filed as follows:
1. A tunable optical fibre filter comprising two single mode optical fibres coupled together at two or more closely spaced regions by means of biconical couplings, and means for introducing a phase shift in the fibres between two couplings.
2. A filter according to Claim 1 incorporating a layer of high resistivity material on at least one of the fibres between the two couplings and means for passing an electric current through the layer to effect the heating of the fibre.
3. A filter according to Claim 1 incorporating on the fibres between the two couplings substantially identical layers of high resistivity material, and means for passing an electric current through at least one of the layers for heating the respective fibre.
4. A filter according to any preceding claim wherein the couplings and the parts of the fibres between them are encapsulated within a protective medium.
5. A filter according to Claim 4 wherein the protective medium comprises a thermosetting resin.
6. A filter according to any preceding claim wherein the biconical coupling at the input end of the filter has a broader pass band characteristic than the second or an subsequent coupling.
GB8612782A 1986-05-27 1986-05-27 Tunable optical fibre filters Expired GB2191013B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8612782A GB2191013B (en) 1986-05-27 1986-05-27 Tunable optical fibre filters

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8612782A GB2191013B (en) 1986-05-27 1986-05-27 Tunable optical fibre filters

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GB8612782D0 GB8612782D0 (en) 1986-07-02
GB2191013A true GB2191013A (en) 1987-12-02
GB2191013B GB2191013B (en) 1989-12-13

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0382461A2 (en) * 1989-02-07 1990-08-16 Nippon Telegraph and Telephone Corporation Guided-wave optical branching components and optical switches
US4953934A (en) * 1987-12-09 1990-09-04 Hitachi, Ltd. Waveguide type light merging and branching device
GB2329721A (en) * 1997-09-24 1999-03-31 Northern Telecom Ltd Optical attenuator
WO2001092933A2 (en) * 2000-05-31 2001-12-06 Corning Incorporated A method for tuning the spectral response of a monolithic tapered fiber filter device
EP1245974A1 (en) * 2001-03-30 2002-10-02 Corning O.T.I. S.p.A. Mach-Zehnder interferometer and method of manufacture thereof
US6782168B2 (en) * 2001-06-22 2004-08-24 Sumitomo Electric Industries, Ltd. Apparatus for and method of monitoring wavelength multiplexed signal light as well as optical transmission system using the same
US6862386B2 (en) 2001-03-30 2005-03-01 Corning Incorporated Method of making a Mach-Zehnder interferometer, and related device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1175855A (en) * 1966-08-25 1970-01-01 American Optical Corp Improvements in or relating to information processors
GB2096784A (en) * 1981-04-09 1982-10-20 Standard Telephones Cables Ltd Optical fibre temperature sensors
GB2167575A (en) * 1984-11-21 1986-05-29 Gen Electric Co Plc Optical couplers

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1175855A (en) * 1966-08-25 1970-01-01 American Optical Corp Improvements in or relating to information processors
GB2096784A (en) * 1981-04-09 1982-10-20 Standard Telephones Cables Ltd Optical fibre temperature sensors
GB2167575A (en) * 1984-11-21 1986-05-29 Gen Electric Co Plc Optical couplers

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IEE PROCEEDINGS, VOL 132, PT J, OCTOBER 1985, PAGES 277 TO 286, *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4953934A (en) * 1987-12-09 1990-09-04 Hitachi, Ltd. Waveguide type light merging and branching device
EP0382461A2 (en) * 1989-02-07 1990-08-16 Nippon Telegraph and Telephone Corporation Guided-wave optical branching components and optical switches
EP0382461A3 (en) * 1989-02-07 1991-11-27 Nippon Telegraph and Telephone Corporation Guided-wave optical branching components and optical switches
GB2329721A (en) * 1997-09-24 1999-03-31 Northern Telecom Ltd Optical attenuator
WO2001092933A2 (en) * 2000-05-31 2001-12-06 Corning Incorporated A method for tuning the spectral response of a monolithic tapered fiber filter device
WO2001092933A3 (en) * 2000-05-31 2002-05-23 Corning Inc A method for tuning the spectral response of a monolithic tapered fiber filter device
EP1245974A1 (en) * 2001-03-30 2002-10-02 Corning O.T.I. S.p.A. Mach-Zehnder interferometer and method of manufacture thereof
WO2002079833A1 (en) * 2001-03-30 2002-10-10 Corning O.T.I. S.P.A. Mach-zehnder interferometer and method of manufacture thereof
US6862386B2 (en) 2001-03-30 2005-03-01 Corning Incorporated Method of making a Mach-Zehnder interferometer, and related device
US6782168B2 (en) * 2001-06-22 2004-08-24 Sumitomo Electric Industries, Ltd. Apparatus for and method of monitoring wavelength multiplexed signal light as well as optical transmission system using the same

Also Published As

Publication number Publication date
GB8612782D0 (en) 1986-07-02
GB2191013B (en) 1989-12-13

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19930527