GB2121532A - Fibre optic gyroscope - Google Patents
Fibre optic gyroscope Download PDFInfo
- Publication number
- GB2121532A GB2121532A GB08214889A GB8214889A GB2121532A GB 2121532 A GB2121532 A GB 2121532A GB 08214889 A GB08214889 A GB 08214889A GB 8214889 A GB8214889 A GB 8214889A GB 2121532 A GB2121532 A GB 2121532A
- Authority
- GB
- United Kingdom
- Prior art keywords
- fibre
- polarization
- gyroscope
- optic
- loop
- 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- Withdrawn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 title claims abstract description 24
- 230000010287 polarization Effects 0.000 claims abstract description 38
- 230000000694 effects Effects 0.000 claims abstract description 6
- 238000005562 fading Methods 0.000 claims abstract description 6
- 230000003287 optical effect Effects 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 5
- 239000000758 substrate Substances 0.000 claims description 5
- 230000005540 biological transmission Effects 0.000 claims description 3
- 230000008878 coupling Effects 0.000 claims description 2
- 238000010168 coupling process Methods 0.000 claims description 2
- 238000005859 coupling reaction Methods 0.000 claims description 2
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 239000013307 optical fiber Substances 0.000 description 4
- 230000001902 propagating effect Effects 0.000 description 2
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 description 1
- 229910003327 LiNbO3 Inorganic materials 0.000 description 1
- 229910012463 LiTaO3 Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000028161 membrane depolarization Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000000135 prohibitive effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
- B64G1/00—Cosmonautic vehicles
- B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
- B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
- B64G1/36—Guiding or controlling apparatus, e.g. for attitude control using sensors, e.g. sun-sensors, horizon sensors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
- B64G1/00—Cosmonautic vehicles
- B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
- B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
- B64G1/36—Guiding or controlling apparatus, e.g. for attitude control using sensors, e.g. sun-sensors, horizon sensors
- B64G1/369—Guiding or controlling apparatus, e.g. for attitude control using sensors, e.g. sun-sensors, horizon sensors using gyroscopes as attitude sensors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/58—Turn-sensitive devices without moving masses
- G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
- G01C19/72—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
-
- 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
- G02B6/30—Optical coupling means for use between fibre and thin-film device
Landscapes
- Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Aviation & Aerospace Engineering (AREA)
- Optics & Photonics (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Power Engineering (AREA)
- Gyroscopes (AREA)
Abstract
A high performance single mode, single polarization fibre-optic gyroscope includes in an integrated optics architecture 26 a polarizer 20. To negate the effect of residual birefringence in the fibre 10, and external environmental changes, which result in fading of the signal at the output of the detector 17, there is included an active polarization controller 21. This controller is implemented in the integrated optics as a variable TE/TM phase shifter 22 in series with a TE<==>TM converter 23. Control signals derived from the photodetector 17 via a feedback loop 24 and electronics 25 periodically adjust the phase shifter control voltage V1, and the converter control voltage V2 to obtain maximum output from the photodetector. <IMAGE>
Description
SPECIFICATION
Fibre-optic gyroscope
This invention relates to improvements in fibre-optic gyroscopes and is particularly suited to gyroscopes fabricated with integrated electrooptics.
The principle of a closed loop interferometer gyroscope, utilising the Sagnac effect, is well documented. The recent development of low-loss optical fibres by means of which the closed loop interferometer can be implemented in a practical form is also well documented. The paper "Fiber
Optic Rotation Sensor (FORS) Signal Detection and
Processing" by Willis C. Goss and Raymond Goldstein, Optical Engineering, Jan.- Feb. 1979, Vol. 18
No. 1, pp 9-13, provides a background to the subject.
When optical fibre gyroscopes are configured in an architecture which provides high sensitivity the optical output is subject to fading from polarization effects unless steps are taken to prevent these effects. Methods of achieving a continuous output include (a) the use of a polarization maintaining fibre, or (b) depolarization of the signal. Unfortunately, polarization maintaining fibres are difficult to obtain, their performance is poor and, even in the longer term, their cost is expected to be prohibitive.
The use of depolarizers has been demonstrated in bulk systems, but no known equivalent is known in integrated optics form.
According to the present invention there is provided a fibre-optic gyroscope including means for energising the fibre-optic loop with a single mode, single polarization signal and means for effecting polarization transforms of the optical signals at one loop fibre end such that environmentally induced polarization rotation of the optical signals in the fibre are compensated, said energising means and said polarization transform effecting means being implemented in the form of integrated electro-optics on a common electrooptic substrate.
In a preferred embodiment of the invention the gyroscope includes a feedback control loop whereby a control signal is derived from a portion of the gyroscope optical output to control the polarization transform to achieve maximum transmission of the optical signals in the fibre loop.
The invention also provides a method of obviating fading from polarization effects in a single mode, single polarization fibre-optic gyroscope having integrated electro-optic components, including the step
of effecting a polarization transform of the optical signals at one end of the fibre loop such that fibre induced polarization rotation of the optical signals is compensated, said transform being effected in response to a feedback signal derived from the gyroscope output.
Embodiments of the invention will now be described with reference to the accompanying draw
ing, which illustrates an integrated electro-optics form of fibre-optic gyroscope.
The basis of the fibre-optic gyroscope is a coil 10
of optical fibre. 50% of the light leaving the laser 11 reachesthe coupler 15, via an optical guide 13, where it is equally split and coupled into the ends 12 and 14 of the fibre coil. After propagating through the fibre 10, the light emerging from the fibre ends is recombined by the coupler 15 and enters the guide 13. 50% of this light is transferred via coupler 16 to a detector 17. Hence the detector will receive approximately 25% of the original laser output power. The basic gyroscope configuration is completed by the inclusion of a Sagnac modulator 18 in one optical path to the coil, and a phase locked loop modulator 19 in one path. These components are not pertinent to the present invention and need not be further considered here.
For high performance it is necessary that the gyroscope operates with a single mode, single polarization signal. Single mode operation can be readily ensured by utilising optical fibre and optical components which only support single mode propagation. Single polarization is achieved by the inclusion of a polarizer 20 in the optical path between the two couplers. However, residual birefrigence in the optical fibre, and external environment changes, cause the state of polarization at the two fibre coil ends to be different with time, resulting in fading. To overcome this the optical path to one fibre end includes an active polarization controller or transformer 21. This comprises a variable TE/TM phase shifter 22 in series with a phase matched TE < +TM converter 23 with variable coupling.Operation of such a polarization controller is described in an article "Electrooptic Guided-Wave Device for
General Polarization Transformations" by Rod C.
Alferness, IEEE Journal of Quantum Electronics, Vol.
QE-17, No. 6, June 1981, at pages 965-969. The TE
TM mode converter is capable of providing a linear output polarization of purely TE or TM type only if the TE and TM input polarization components have a
O or 1r/2 phase difference. Thus, the phase shifter (control voltage V1) is used to achieve this state, whilst the mode converter (control voltage V2) adjusts the relative powers in the output TE and TM components. Assuming the polarizers pass only TE polarized light, maximum output is obtained from a feedback loop 24 involving the system detector 17 and the voltage control circuit 25. Firstly, V1 is adjusted to give a maximum signal received by the detector, then V2 is adjusted also to maximize the detector signal. In this way, V1 is correctly set, regardless of the value of V2, and only one iteration of the procedure is required.The result is that light passing from the fibre to polarizer will have its polarization changed from some arbitrary state to
TE, whilst light passing in the reverse direction will have its polarization changed from TE to some arbitrary state, such that on propagating through the fibre and returning to the polarizer it wil be purely TE polarized. As the polarization drifts due to the (generally) slowly changing environmental conditions surrounding the fibre, the voltages V1 and V2 must be readjusted. Simple electronic timing circuitry in the feedback loop can easily provide periodic optimization of these voltages. The polarization transformer demands a minimum coherence length, given by the need to separate the TE and TM components by up to ir radians and the value of (PTE - PTM), the modal birefringence.Typically, the mini mum coherence required is - 5 Fm, which means that an edge-emitting light emitting diode (ELED) (coherence length - 20 Clam) or a longer coherence laser can be used, as determined by other parts of the system. By providing a feedback signal from the system detector, the polarization can be actively controlled to ensure maximum transmission through the polarizer, even in the presence of environmentally induced changes in the fibre birefringence.
Afibre-optic gyroscope as described lends itself to fabrication as an integrated electro-optics device.
The optical waveguides 13, couplers 15, 16, polarizers 20, modulators 18, 19 and polarization controller 21 can all be fabricated with currently available technology in a single electro-optic substrate 26, e.g.
lithium niobate LiNbO3 or lithium tantalate LiTaO3.
The waveguides 13 are obtained by diffusion of metal ions into the substrate in a known manner and the active devices are realised by the formation of metal electrode patterns on the substrate surface.
Claims (7)
1. A fibre-optic gyroscope including means for energising the fibre-optic loop with a single mode, single polarization signal and means for effecting polarization transforms of the optical signals at one loop fibre end such that environmentally induced polarization rotation of the optical signals in the fibre are compensated, said energising means and said polarization transform effecting means being implemented in the form of integrated electro-optics on a common electrooptic substrate.
2. Afibre-optic gyroscope according to claim 1 including a feedback control loop whereby a control signal is derived from a portion of the gyroscope optical output to control the polarization transform to achieve maximum transmission of the optical signals in the fibre loop.
3. Afibre-optic gyroscope according to claim 2 wherein the feedback loop input is taken from the electrical output of the gyroscope photodetector.
4. Afibre-optic gyroscope according to claim 2 or 3 wherein the polarization transform effecting means comprises an electro-optic variable TE/TM phase shifter in series with a phase matched TE TM converter with variable coupling, the feedback control loop periodically producing a control signal for the variable phase shifter to give maximum signal at the gyroscope output followed by a control signal for the converter to maximise the gyroscope output.
5. A fibre-optic gyroscope substantially as described with reference to the accompanying drawing.
6. A method of obviating fading from polarization effects in a single mode, single polarization fibre-optic gyroscope having integrated electro-optic components, including the step of effecting a polarization transform of the optical signals at one end of the fibre loop such that environmentally induced polarization rotation of the optical signals in the fibre are compensated, said transform being effected in response to a feedback signal derived from the gyroscope output.
7. A method of obviating fading in an integrated optics fibre optic gyroscope substantially as hereinbefore described.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08214889A GB2121532A (en) | 1982-05-25 | 1982-05-25 | Fibre optic gyroscope |
| AU18491/83A AU1849183A (en) | 1982-05-25 | 1983-08-29 | Fibre optic gyroscope |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08214889A GB2121532A (en) | 1982-05-25 | 1982-05-25 | Fibre optic gyroscope |
| AU18491/83A AU1849183A (en) | 1982-05-25 | 1983-08-29 | Fibre optic gyroscope |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2121532A true GB2121532A (en) | 1983-12-21 |
Family
ID=25617216
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08214889A Withdrawn GB2121532A (en) | 1982-05-25 | 1982-05-25 | Fibre optic gyroscope |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU1849183A (en) |
| GB (1) | GB2121532A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0172391A2 (en) * | 1984-07-20 | 1986-02-26 | LITEF GmbH | Method and apparatus for measuring rotation rate using the Sagnac effect |
| GB2187837A (en) * | 1986-03-14 | 1987-09-16 | British Aerospace | Beam splitters |
| US4699451A (en) * | 1983-09-10 | 1987-10-13 | International Standard Electric Corp. | Optical fiber coil having juxtaposed ends in same or adjacent layers for rotation rate measuring instrument |
| WO1989002060A1 (en) * | 1987-09-01 | 1989-03-09 | Litton Systems Inc. | Fiber optic gyroscope with improved bias stability and repeatability and method |
| EP0383231A2 (en) * | 1989-02-15 | 1990-08-22 | Japan Aviation Electronics Industry, Limited | Fiber optic gyroscope |
| WO1990011491A1 (en) * | 1989-03-27 | 1990-10-04 | United Technologies Corporation | Single-polarization, integrated optical components for optical gyroscopes |
| US5037205A (en) * | 1989-04-19 | 1991-08-06 | Litton Systems, Inc. | Integrated optic interferometric fiber gyroscope module and method |
| GB2265457A (en) * | 1992-03-28 | 1993-09-29 | British Aerospace | Low-drift switched-coil fibre gyro |
| US20120182551A1 (en) * | 2011-01-19 | 2012-07-19 | National Cheng Kung University | Free space single-mode fibers and fiber components for fiber sensor applications |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4842358A (en) * | 1987-02-20 | 1989-06-27 | Litton Systems, Inc. | Apparatus and method for optical signal source stabilization |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2044447A (en) * | 1979-01-15 | 1980-10-15 | Max Planck Gesellschaft | Method and arrangement for the measurement of rotation by the sagnac effect |
-
1982
- 1982-05-25 GB GB08214889A patent/GB2121532A/en not_active Withdrawn
-
1983
- 1983-08-29 AU AU18491/83A patent/AU1849183A/en not_active Abandoned
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2044447A (en) * | 1979-01-15 | 1980-10-15 | Max Planck Gesellschaft | Method and arrangement for the measurement of rotation by the sagnac effect |
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4699451A (en) * | 1983-09-10 | 1987-10-13 | International Standard Electric Corp. | Optical fiber coil having juxtaposed ends in same or adjacent layers for rotation rate measuring instrument |
| EP0172391A2 (en) * | 1984-07-20 | 1986-02-26 | LITEF GmbH | Method and apparatus for measuring rotation rate using the Sagnac effect |
| EP0172391A3 (en) * | 1984-07-20 | 1986-06-04 | Litef Litton Techn. Werke Der Hellige Gmbh | Method and apparatus for measuring rotation rate using the sagnac effect |
| GB2187837A (en) * | 1986-03-14 | 1987-09-16 | British Aerospace | Beam splitters |
| WO1989002060A1 (en) * | 1987-09-01 | 1989-03-09 | Litton Systems Inc. | Fiber optic gyroscope with improved bias stability and repeatability and method |
| US5085501A (en) * | 1989-02-15 | 1992-02-04 | Japan Aviation Electronics Industry Limited | Fiber optic gyroscope using optical waveguide couplers |
| EP0383231A3 (en) * | 1989-02-15 | 1990-12-05 | Japan Aviation Electronics Industry, Limited | Fiber optic gyroscope |
| EP0383231A2 (en) * | 1989-02-15 | 1990-08-22 | Japan Aviation Electronics Industry, Limited | Fiber optic gyroscope |
| WO1990011491A1 (en) * | 1989-03-27 | 1990-10-04 | United Technologies Corporation | Single-polarization, integrated optical components for optical gyroscopes |
| US5037205A (en) * | 1989-04-19 | 1991-08-06 | Litton Systems, Inc. | Integrated optic interferometric fiber gyroscope module and method |
| GB2265457A (en) * | 1992-03-28 | 1993-09-29 | British Aerospace | Low-drift switched-coil fibre gyro |
| GB2265457B (en) * | 1992-03-28 | 1995-10-11 | British Aerospace | A fibre optic gyro |
| US20120182551A1 (en) * | 2011-01-19 | 2012-07-19 | National Cheng Kung University | Free space single-mode fibers and fiber components for fiber sensor applications |
| US9448116B2 (en) * | 2011-01-19 | 2016-09-20 | National Applied Research Laboratories | Free space single-mode fibers and fiber components for fiber sensor applications |
Also Published As
| Publication number | Publication date |
|---|---|
| AU1849183A (en) | 1985-03-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |