CN105091877A - Rotation sensing method based on polarization state of light and optical gyroscope thereof - Google Patents

Abstract

The present invention relates to a rotation sensing method based on polarization state of light and an optical gyroscope thereof, and belongs to the technical fields of optical equipment and optical sensing. Rotation sensing can have a very wide range of applications, including navigation, motion sensing, motion control including object attitude control, motion platform control, and handheld device such as a fashion phone. The optical gyroscope utilizes the change between interference optical paths of forward and reverse transmitted light caused by the rotation to detect the rotation. Most optical gyroscope are based on optical Sagnac interferometer structure, including a variety of interferometric fiber optic gyroscopes. Such fiber optic gyroscopes can be designed with no moving parts, and vibration component or motion unit included in other gyros can be eliminated.

Description

The method and the optical gyroscope thereof that rotate sensing is carried out based on polarisation of light state

Technical field

The invention belongs to optical device and optical sensing technical field, particularly based on the non-interfering formula fibre optic gyroscope of polarization sense.

Background technology

Optical device and optical sensing technology comprise optical gyroscope and rotary optical sensing.

Rotate sensing existence to apply very widely, comprise navigation, motion-sensing, motion control comprises gestures of object and controls, and motion platform controls, and handheld device is as fashionable cell-phone etc.Interfere the change of light path to carry out rotation sensing between forward and reverse transmission two light that optical gyroscope causes by utilizing rotation.A lot of optical gyroscope all comprises various interferometric fiber optic gyroscope based on optics Sagnac interferometer structure.This type of optical gyroscope is usually designed to no-rotary part, therefore, can eliminate rotatable parts required in other gyroscope.At present, interferometric fiber optic gyroscope is commercialization, and has had a large amount of products on much dual-use.

Fig. 1 and Fig. 2 gives two kinds of optical interference formula gyroscopes based on Sagnac interferometer.Give the space gyroscope that (bulk) designs in Fig. 1, and in Fig. 2, illustrate the interferometric fiber optic gyroscope based on fiber optic loop.In order to improve sensitivity and stability, need the fiber optic loop using longer distance relatively, such as hundreds of is to the optical fiber of a few km.Fig. 2 is given in further in interferometric fiber optic gyroscope and introduces a phase-modulator, make in gyro, to produce a base inclined, thus make it be operated on the most responsive working point, and adopt the circuit of closed loop, for increasing the gyrostatic dynamic range of interfere type and its detection sensitivity of raising.

Summary of the invention

This patent document has set forth optical device and optical sensing technology comprises optical gyroscope and rotary optical sensing.

On the one hand, provide a kind of method for rotating sensing, the method only realizes, to the sensing of rotating, mainly comprising: the light beam that an input beam divides bunchy two polarization state orthogonal by (1) without the need to depending on optical interdferometer based on polarisation of light sensing; (2) light beam coupling of two bundle polarized orthogonals is used for the input/output port of the optical loop that sensing is rotated to one, make light beam in optical loop along the first optical path direction transmission, and the second bundle light transmits along the second optical path direction in optical loop, the direction that the second light path is contrary with the first loop direction; (3) the first and second light beams are closed again bundle to input/output port, keep the first and second light beams to keep polarization state orthogonal simultaneously, avoid when input and output port closes bundle, the interference of light occurring, using light beam after the conjunction bundle of generation as the output light of optical loop; (4) the polarization state signal of obtained output light is processed, thus obtain the turn signal of optical loop institute sensing.

This patent also proposed a kind of based on the polarization state signal of transmission light being carried out to extraction realization to the optical gyroscope rotating sensing, thus replaces dependence optical interference structures realization rotation sensing.This optical gyroscope comprises: (1) optics input-output device, for a branch of input beam being divided into the light beam of two bundle polarized orthogonals, wherein light beam possesses a polarization state, and the second bundle light possesses and restraints another orthogonal polarization state of polarization state with first; (2) optical loop structure Couplings are on optics input-output device, its first ring road port receives light beam with the first optical loop direction in optical loop, and its second loop ports receives the second bundle light with the second loop direction in optical loop simultaneously.First bundle in optical loop and the second bundle light can be carried out conjunction bundle by light input-output device, keep the polarization state of two light beams mutually orthogonal simultaneously, to avoid between two-beam, the interference of light occurring in light input-output device, thus the light beam this conjunction restrainted is as the optical output signal of optical loop.Also comprise a detecting devices in this optical gyroscope, for detecting optical output signal, thus obtain the light polarization information of optical output signal, and detected light output polarization information is processed, the final turn signal extracting optical loop perception.

This patent further provides a kind of employing and transmission light polarization state is detected to the optical gyroscope realizing turn signal being carried out to sensing, replaces dependence optical interferometer structure and carries out sensing to turn signal.This optical gyroscope comprises following several function: an input beam is divided into two and restraints independently light beam by (1), and wherein the first light beam possesses the first polarization state, and the second bundle light possesses and restraints the second orthogonal polarization state of polarization state with first; (2) by the input/output port of the first and second light beam coupling to the optical loop of a perception amount of spin, light beam is transmitted in loop along the first loop direction, and the second bundle light transmits in ring along the second loop direction, wherein to restraint optical transmission direction contrary for the second bundle optical transmission direction and first; (3) function of carrying out two-beam to close in input/output port bundle is comprised further, using light beam after the conjunction bundle of generation as the optical output signal of optical loop, interfering in order to avoid going out two-beam in input/output port simultaneously, when carrying out combiner, needing the polarization state of maintenance two light beam orthogonal; (4) last, the polarization state information of output optical signal is processed, obtains the turn signal of optical loop perception.

The present invention also provides a kind of based on carrying out checking the method realizing rotation being carried out to sensing to the polarization state of transmission light further, replaces the method adopting optical interdferometer structure to realize carrying out turn signal sensing at present.This method comprises: a branch of input light with input polarization is imported one and is used in the closed optical loop of perception turn signal by (1); (2) light signal of the transmission light in closed optical loop as closed loop optical loop is exported; (3) output optical signal is detected, the output polarization state information of direct output optical signal, instead of depend on the directly related optical interference structures with closed loop optical loop; (4) last, by processing the polarization state information of obtained output optical signal, the final turn signal obtaining closed loop optical loop and experience.

This patent also provides an optical gyroscope further for rotating sensing, this gyroscope carries out sensing based on the polarization state information of transmission light, be replaced in and adopt the structure of optical interferometer to carry out sensing, comprise (1) closed loop optical loop for perception turn signal; (2) input/output port enter closed optical loop for receiving a branch of input light with input polarization, simultaneously for the light in closed loop light circuit is carried out coupling output as output light; (3) one detectors are used for receiving output optical signal, by directly extracting output optical signal polarization information, and do not rely on the optical interferometer structure adopting closed loop; (4) one processing units, by processing the output polarisation of light state information obtained, draw the turn signal that closed loop optical loop experiences.

The above and other side and their principle of work, by picture below, introduce in description in more detail.

Accompanying drawing explanation

Fig. 1 gives a space interference formula optical gyroscope structure;

Fig. 2 gives an interferometric fiber optic gyroscope structure;

Fig. 3 A and Fig. 3 B gives the optical polarization gyroscope of two kinds of different structures.Input light becomes 45 degree to be polarized with the two polarizing axis x-axis of PBS with y-axis, to ensure that two bundle polarized light light intensity are consistent after beam splitting.What Fig. 3 A provided is a nonreciprocity structure: depend on assumed condition, and two polarization states namely between PBS and reflector position are without nonreciprocity phase shift, and the polarization of output optical signal rotates and only depends on that gyro rotates.Fig. 3 B gives a reciprocal structure: by using one 90 degree of faraday rotation mirrors or the light of half-wave plate to y-polarisation state to rotate in x-polarisation state, and after the light of two forward and reverse transmission is reflected on catoptron with PBS, phase place is identical.

Fig. 4 A gives the differential phase shift or Differential Group Delay that produce by rotating, and output polarization state is rotated around the South Pole of kidnapping ball and a great circle of the arctic.

Fig. 4 B provides with the track of circular polarization state on (S2, S3) face, and wherein Df is DPS.

Fig. 5 gives an integrated polarization state analyser example being used for acquisition four Stokes' parameters.

Fig. 6 provides a kind of schematic diagram of fibre optic gyroscope of polarization structure, and this structure adopts a polarization-maintaining fiber coil as rotation sensing unit.In order to eliminate metrical error, the welding of 90 degree of intersections can be carried out at the point midway of fiber optic loop.

Fig. 7 gives the schematic diagram of the fibre optic gyroscope of another kind of polarization structure, and this structure adopts a polarization-maintaining fiber coil as rotation sensing unit.Non-polarizing beamsplitter is used, for being directly registered in polarization analysis instrument by the light of returning from fiber optic loop before PBS.The tail optical fiber of two polarisation fibres can be used to replace the tail optical fiber of polarization maintaining optical fibre, and then obtain more excellent performance.

Fig. 8 A gives the third polarization structure formula fibre optic gyroscope structural representation.Use Wollaston (Wollaston) prism, as polarising beam splitter, two polarized components are pressed different directions incidence.Use a pair of optical fiber structure amasthenic lens for receiving the pairwise orthogonal polarized component exporting light.Two tail optical fibers playing the tail optical fiber replacement polarization maintaining optical fibre of polarisation fibre can be used, and then obtain more excellent performance.

Fig. 8 B gives a pair of optical fiber structure collimating apparatus schematic diagram in Fig. 8 A, and it comprises a condenser lens for receiving two light beams, and they is focused on and be placed in two optical fiber of entry port on focal plane.

Fig. 9 provides the schematic diagram of the 4th kind of polarization fiber gyroscope arrangement.The tail optical fiber of two polarisation fibres can be used to replace the tail optical fiber of polarization maintaining optical fibre, and then obtain more excellent performance.

Figure 10 gives the schematic diagram of a Polarization instrument.A polarizer is placed on after quarter-wave plate for polarization analysis.The slow axis (or fast axle) of quarter-wave plate is with PBS in Fig. 7 or align with the X-axis of Wollaston prism in Fig. 8 and Fig. 9, thus between X and Y polarized component, introduce a pi/2 phase delay.

Figure 11 A and 11B gives the second Polarization instrument structural representation.Polarization is used for by placing a PBS after quarter-wave plate.The slow axis of quarter-wave plate (or fast axle) directly with Wollaston prism alignment in the x-axis of PBS in Fig. 7 or Fig. 8 and Fig. 9, for generation of a pi/2 phase delay.

Figure 12 A and 12B gives the structure of detection circuit in two kinds of different panel detector structures.

Figure 13 A and Figure 13 B gives the structural representation of the third polarization analysis instrument, and wherein 13A provides the layout of equipment, and Figure 13 B then provides the direction of two PBS and the quarter-wave plate direction relative to PBS or Wollaston prism in Fig. 7, Fig. 8 A, Fig. 8 B and Fig. 9.Two PBS have identical X and Y-direction.

Figure 14 A and 14B gives the 4th kind of polarization analysis instrument structure, and this structure uses Wollaston prism to replace the photodetector replacement two independently photodetector of PBS and employing dual chip in Figure 10.Figure 14 B gives the direction of principal axis of Wollaston prism and the direction of principal axis relative to the X of fiber optic loop front side polarization beam splitter and the quarter-wave plate of Y-direction.

Figure 15 A and 15B gives the structural scheme of mechanism of the 5th kind of Polarization instrument, wherein adopts two PBS that two Wollaston prisms replace in Figure 13 A and Figure 13 B, adopts two dual chip photodetectors to replace four photodetectors separated.Figure 15 B gives x and the y direction relative to fiber optic loop front side polarization beam splitter, the direction of Wollaston prism axis and quarter-wave bobbin.

Figure 16 gives the 6th kind of polarization structure fibre optic gyroscope schematic diagram.If adopt a polarized light source, need to adopt polarization maintaining fiber pigtail to couple light in dotted line frame.Such as, if use a depolarized light source, ASE light source, then adopt a single-mode tail fiber.When the extinction ratio performance of polarization beam apparatus 1 (PBS1) can not meet the demands, then need use one polarizer for being polarized the light of input system.When the extinction ratio performance of PBS1 is inadequate, any polarizer can be used to be polarized input light source.Light source can be integrated in empty frame box with chip form, thus reduces size and the price of instrument.For this situation, the light-source structure without tail optical fiber can be adopted.Use the tail optical fiber of two polarisation fibres to replace the tail optical fiber of polarization maintaining optical fibre, and then obtain more excellent performance.If use 45 degree of faraday rotation mirror to replace the quarter-wave plate on beam splitter (BS) right side, then need to use a quarter-wave plate before the polarizer, make the main shaft of wave plate consistent with the main shaft of PBS.

Figure 17 gives the 7th kind of polarization structure fibre optic gyroscope.If use polarized light source, then need to adopt polarization maintaining fiber pigtail to be coupled in dotted line frame by transmission light.Such as, if use a depolarized light source, ASE light source, then employing one single-mode optical fiber pigtail is needed to be coupled in dotted line frame by transmission light.If the extinction ratio performance of polarization beam apparatus 1 (PBS1) not, a polarizer can be used to export light to light source and to be polarized.Light source can adopt chip form to be integrated into dotted line frame inside simultaneously, and then reduces volume and the cost of manufacture of instrument.In this case, light source below can connect tail optical fiber.Use two tail optical fibers playing the tail optical fiber tail optical fiber replacement polarization maintaining optical fibre of polarisation fibre, and then obtain more excellent performance.If use 45 degree of faraday rotation mirrors to replace the quarter-wave plate on beam splitter (BS) right side, then need to use in the front of the polarizer quarter-wave plate that different, ensure that the main shaft (X, Y) of the main shaft of wave plate and Wollaston prism is consistent.

Figure 18 gives the 8th kind of polarization structure fibre optic gyroscope structural representation.If use a polarized light source, then employing one polarization maintaining fiber pigtail is needed to be coupled in dotted line frame by transmission light.Such as, if use a depolarized light source, ASE light source, then employing one single-mode optical fiber pigtail is needed to be coupled in dotted line frame by transmission light.If the extinction ratio performance of polarization beam apparatus (PBS) not, a polarizer can be used to export light to light source and to be polarized.Light source can adopt chip form to be integrated into dotted line frame inside simultaneously, and then reduces volume and the price of instrument.In this case, light source below can connect tail optical fiber.If use 45 degree of faraday rotation mirror to replace the quarter-wave plate on beam splitter (BS) right side, then need to use a different quarter-wave plate in the front of the polarizer, ensure that the main shaft (X, Y) of the main shaft of wave plate and Wollaston prism is consistent.

Figure 19 A and 19B gives two kinds of detecting devices structures, this structure based on lock-in amplify circuit structure, for improving the signal to noise ratio (S/N ratio) of detectable signal.

Figure 20 A and 20B gives two kinds of detector device structures, this structure based on lock-in amplify circuit and optical phase modulator structure, for improving the signal to noise ratio (S/N ratio) of detectable signal.

Figure 21 gives for detecting that rotational angle carries out linearizing electrical block diagram.

Embodiment

Disclosure sets forth and adopt optical sensing amount of spin to be carried out to the technology and equipment of sensing, mainly measure and sensing based on to polarization state or the polarization state variable quantity that causes due to rotation, instead of adopt optical interdferometer structure.Realize carrying out sensing to rotation based on the detection to optical polarization change of the present invention, optical gyroscope can be applied in very large application, comprise aviation, the field such as navigation and land fighting vehicle, can apply in multiple sensors and equipment, such as hand-held transmission equipment, such as panel computer and fashionable cell-phone, platform controller and other inspection for precise rotation speed and angle.

One of scheme, be to provide a kind of method for detecting turn signal, in the closed loop optical loop of the method based on the input optical alignment to an experience turn signal one with input polarization, and by carrying out sensing to the detection of transmission light polarization conversion, instead of depend on optical interdferometer structure sensing is carried out to turn signal; Using the output optical signal coupling output of the transmission light in closed loop optical loop as this loop; Realize exporting light signal detecting by the polarization state change information obtaining output optical signal, instead of depend on optical interdferometer structure; Obtained output polarization state change information is processed, obtains the turn signal that optical loop experiences.Another kind detects based on to the change of transmission light polarization state and then realizes sensing, instead of depend on optical interdferometer structure and carry out sensing for carrying out the scheme of sensing to turn signal, specifically comprise and the input light with input polarization is beamed into the orthogonal transmission light of two bundle polarization states, wherein the first bundle exports light and possesses the first polarization state, and the second bundle transmission light possesses and restraints the second mutually orthogonal polarization state of polarization state with first; Coupling first bundle and the second bundle light signal enter the input/output port of the optical loop for perception turn signal, aim at the first light beam to transmit with the first loop direction in optical loop, aim at the second light beam in optical loop to transmit with the rightabout second loop direction of the first loop simultaneously; First and second light beams are carried out conjunction bundle in input/output port, produce the output optical signal of a combination optical signal as optical loop, require that the first and second polarization states are mutually orthogonal while bundle is closed to two-beam, avoid two light beams in the input/output port generation interference of light.In addition, the method also comprises and detecting output optical signal, obtains and exports polarisation of light state change information; Again obtained output polarization state change information is processed, finally obtain the turn signal that optical loop experiences.

Set forth and detected by light polarization the optical sensing realized rotating, comprised and change by rotating the light polarization caused the optical gyroscope realized turn signal sensing from detecting.Use a closed loop optics ring, realize the sensing to closed loop optics ring rotates by the two-beam of transmission forward and reverse in ring, concrete, such as, to the measurement of the rotative component perpendicular to closed loop optic circle plane.

Fig. 3 A and Fig. 3 B gives the embodiment adopting closed loop optics ring optical gyroscope.To be divided into the two-beam of polarization state orthogonal (X and Y polarization direction) through polarising beam splitter (PBS) 302 from light source (as semiconductor laser or light emitting diodes) linear polarization input light 301 out.The orthogonal polarized light of two polarization states along the forward and reverse transmission of closed loop optical loop 303, and again closes bundle on polarization beam apparatus PBS302, and outputs to polaroid analyze 304 from polarization beam apparatus PBS302 output terminal.Therefore, in this scenario, PBS302 is as the output/input optical port of closed loop optical loop 303.When system experience is rotated, two light of forward and reverse transmission experience one is postponed relatively or differential phase poor.This postpones the simple differencing group delay (DGD) for the orthogonal two-beam of polarization state relatively.When two light converge at PBS302, along with the increase of DGD, close the polarization state output after bundle and the great circle (dextrorotation and left circularly polarized light) along the two-stage in poincare sphere is rotated, as shown in Figure 4 A and 4 B shown in FIG..The measurement to optical rotation momentum can be realized by polarization analysis instrument as shown in Figure 5.

Fig. 3 A and Fig. 3 B is different in some respects, and is have similar place in some in their optical designs.In two structures, input light 301 becomes 45 degree of incidences with two polarization axles of PBS302, therefore, after beam splitting, the power of two polarized lights is equal.Fig. 3 A gives one optically nonreciprocity structure: suppose that two polarization states between PBS302 and catoptron 3031,3032,3033 do not exist differential phase shift, exports polarization state and rotates the rotation only depending on gyro.Therefore, need the accuracy requirement of the optical mirror in focus ring road 303 and PBS302 very high in Fig. 3 A, to ensure that the polarized component between them does not exist additional differential phase shift, can to relax like this in optical loop 303 use the design parameter requirement of device.Give one optically reciprocal structure in Fig. 3 B: by using a faraday rotation mirror (or half-wave plate) 305 to change y-axis into x-axis to polarized light to polarized light, with ensure the light of forward and reverse transmission from optical loop 303 catoptron and PBS302 out after through going through identical phase shift.Structural design in Fig. 3 B meets optics reciprocity for the two-beam of the positive and negative transmission of optical loop 303, therefore, more relax in optical loop 303 use the requirement that optical element performance changes; Owing to adding faraday rotation mirror (or half-wave plate) 305 in Fig. 3 B, make light PBS302 export light to return along Yuan Lu, so increase a beam splitter (BS) 306, be used for output on polarimetry device 304 from the output light beam splitting of polarization beam apparatus PBS302.

Before entering into Fig. 3 A or Fig. 3 B PBS302, the electric field component of light is:

Wherein, x and y represents two transmission axles or the main shaft of PBS302.Pairwise orthogonal polarization state transmission light experience optical loop 303 after and after converging with PBS302, its electric field can be expressed as:

Wherein, Δ φ is the phase differential that optical loop rotates the pairwise orthogonal transmitting beam caused, and this phase differential is the same with interference optical gyro, can be expressed as:

Δφ＝2πDGD/λ ₀＝(4πA/λ ₀c)ω(3)

Wherein A is the area that light beam surrounds, λ ₀be centre wavelength, c is the light velocity, and ω is slewing rate.Additional phase shift is there is not between two polarized lights when our hypothesis is transmitted in optical loop 303 in literary composition.In formula (2), we suppose in Fig. 3 A or Fig. 3 B between PBS and catoptron, export polarisation of light and rotate the rotation only depending on gyro.

Fig. 4 A gives differential phase shift because physical location causes or differential group delay and the polarization state caused rotates around the south poles great circle of poincare sphere.Fig. 4 B gives the track of circular polarization state on (S2, S3) face, and wherein Δ φ is differential phase shift.

Fig. 5 gives a kind of structural drawing for obtaining the Stokes Polarization device exporting all Stokes' parameters of light from the PBS302 Fig. 3 A or Fig. 3 B.Export light and be divided into independently four parts.In order to obtain the luminous power P1 of light beam, before light beam enters first photodetector 5012, its major axes orientation according to first polarizer 5011 is needed to propagate, and in order to obtain the luminous power P2 of the second bundle light, need before the second bundle light enters second photodetector 5022, its orthogonal directions according to the polarizer 5011 to be propagated.In order to obtain the luminous power P3 of three-beam, need to become 45 degree of directions to propagate according to the polarizer 5011 main shaft it when three-beam enters the polarizer 5031; Finally, during in order to obtain the luminous power P4 of the 4th bundle light, need, before light enters the 4th photodetector 5042 to the 4th bundle, to need to allow it through a quarter-wave plate 5043 and a polarizer 5041.And need to allow the main shaft of quarter-wave plate 5043 align with first polarizer 5011 polarization axle (x-axis), and allow the polarization axle of the 4th polarizer 5041 become miter angle direction to align with the polarization axle (x-axis) of first polarizer 5011.Four parametric component of Stokes can be obtained by following formula:

S ₀＝P ₁+P ₂(4)

s ₁＝(P ₁-P ₂)/S ₀(5)

s ₂＝(2P ₃-S ₀)/S ₀(6)

s ₃＝(2P ₄-S ₀)/S ₀(7)

Wherein, time represent the matrix of quarter-wave plate, α for comprising each channel circuit gain, photodetector photon conversion efficiency, the coefficient of three aspects contributions such as light loss.Although the light loss of each passage is different with the transformation efficiency of detector, can be met by regulating circuit gain and make alpha parameter in all passages identical.In formula (11),

From formula (5)-(7), the Stokes' parameter of the light returned from loop can be expressed as:

s ₁＝0(13)

s ₂＝cosΔφ(14)

s ₃＝sinΔφ(15)

given next circle in Fig. 4, wherein

Δφ＝tan ^-1(s ₃/s ₂)(16)

Δ φ also can obtain from formula (14) or formula (15), depends primarily on its value.When Δ φ value is less, formula (15) can be used to ask for, and become large when Δ φ value and close to during as pi/2, then need employing formula (14) to obtain.Therefore, polarization state rotation angle by simply asking for acquisition to differential phase shift between pairwise orthogonal polarization state, directly can be directly proportional to optical loop system angle of rotation speed, and does not need to adopt phase bias.By measuring polarization state rotation angle, can the slewing rate of direct access systems.

Because polarization state track is directly in (S2, S3) plane, therefore do not need to measure S1, and then simplify the measurement to Δ φ in Fig. 5, as described below.

The gyrostatic several advantage of polarization structure comprises 1) without the need to adopting phase-modulator to gyrosystem, will very large cost price be saved compared with interfere type gyroscope; 2) the polarization state anglec of rotation and system slewing rate linear, it directly causes gyro to possess better calibration factor and larger dynamic range; 3) sense of rotation of polarization state rotation direction that is direct and gyrosystem links together, and greatly reduces and turns to cosine to export relevant indefinite factor to interference type optical fiber gyroscope; 4) in polarization structure optical gyroscope, PBS plays double effects, optical loop is made to obtain the two-beam of forward and reverse transmission as beam splitter, simultaneously as the polarizer for eliminating the impact of some unwanted polarized components in forward and reverse transmission two-beam of outputting in optical loop, be similar to the integrated optical device (IOC) in interference type optical fiber gyroscope; 5) circuit system structure simpler and only need be lower power consumption because without the need to modulation signal for driving phase-modulator and designing for digital closed loop without the need to the FPGA/DSP of higher rate.Only need the mimic channel of low-power consumption for detecting polarization state rotating signal.

Optical fiber can be used in polarization structure optical gyroscope to be used for strengthening detector sensitivity, and this is the same with interference type optical fiber gyroscope, as shown in Figure 6 and Figure 7.This equipment is polarization structure fibre optic gyroscope, or P-FOGs, is different from interferometric fiber optic gyroscope (IFOG).As shown in Figure 6, the light that a light source 601 is exported by polarization maintaining optical fibre 604, its polarization axle docks with the input port polarization axle of polarization beam apparatus (PBS) 602 is at 45 °, two output ports 6021 and 6022 of PBS601 are aimed at respectively with the slow axis of the port 6031 of polarization maintaining optical fibre fiber optic loop 603 and the fast axle of port 6032, the final output port of PBS docks with polaroid analyze 605 input port, produces electric signal and is used for next step process; But the transfer rate difference due to polarization maintaining optical fibre fast and slow axis causes there is larger being biased between the two.This is biased also to the sensitive of temperature, can cause larger detecting error.Solving the method reducing this base inclined is arrange an intersection fusion point at the point midway of fiber optic loop, as shown in Figure 6.But the method is not easy to realize, because be difficult to the position determining mid point accurately.Because the structure self of Fig. 3 A and Fig. 6 exists nonreciprocity, therefore, be not suitable for the application scenario of high accuracy gyroscope.

Fig. 7 gives a kind of schematic diagram structure, wherein directly docks with the same main shaft of the polarization maintaining optical fibre of polarization-maintaining fiber coil 705 (slow axis or fast axle) from PBS704 two polarized lights out.Now, need to place a beam splitter 702 before PBS704, the light for fiber optic loop being sent back incides in polaroid analyze 706.Similar to the minimal structure of interferometric fiber optic gyroscope, this structure can eliminate all nonreciprocities that optical element produces.Without the need to using 90 degree faraday rotation mirrors as shown in Figure 3 B or half-wave plate 305, because it can be made to produce 90 degree of rotations by torsion polarization maintaining optical fibre.

Also single-mode fiber can be adopted in the application and non PM fiber in P-FOG structure.Similar to IFOG, polarization maintaining fiber pigtail first can be used to be connected with the output terminal of PBS, to make slow (soon) axle and two of polarization maintaining optical fibre export polarisation of light direction and aim at.Then welding one depolarizer on polarization maintaining fiber pigtail, realizes entering in single-mode fiber ring at two light carrying out depolarized to it.

If when the extinction ratio performance of PBS704 is poor, can inclined optical fiber pigtail be used to replace two polarization maintaining fiber pigtails 7051 and 7052 of the output terminal connecting PBS704, the polarization extinction ratio of further raising system.In such an embodiment, need to allow the polarization state of PBS704 two output beam aim at the transmission axle playing polarisation fibre.If use polarization-maintaining fiber coil, polarization maintaining optical fibre can be allowed to aim at an inclined optical fiber pigtail and to be connected, namely allow its slow axis (or fast axle) directly aim at a polarisation fibre.If use single-mode fiber ring, then need first to connect a depolarizer on an inclined optical fiber pigtail.Then depolarizer is exported and be fused on the tail end of single-mode fiber.A polarizer 7041 and 7042 can be placed in addition at the output terminal of PBS704---such as use inclined glass crystal to make, to improve the extinction ratio of PBS704 further.

In Fig. 7, polarization for light source 701 can have three kinds of selections to axle: 1) the polarization maintaining optical fibre slow axis of light source 701 is aimed at from left side with a certain axle s and the p axle of beam splitter (BS) 703, then will rotate 45 ° from the PBS704 after BS703 for realizing polarizing beam constant power beam splitting orthogonal on PBS704 output port; 2) polarization maintaining fiber pigtail 7011 slow axis of light source 701 is aimed at one of BS beam splitter s axle and p axle, then uses quarter-wave plate or 45 degree of faraday rotation mirrors 7031 that the light beam inciding PBS is divided into the orthogonal two-beam of constant power; 3) polarization maintaining optical fibre 7011 slow axis of light source 701 is docked by 45 degree with the polarization axle of PBS704, to realize the orthogonal polarisation state light constant power beam splitting of PBS704 output port place.Can a polarizer 7041 and 7042 be used to improve the extinction ratio of PBS at two output port places.The object that the polarized light exported by light source 701 is aimed at s axle or the p axle of BS703 avoids occurring that polarization state that is that cause changes because the average beam splitting of BS703 is undesirable.Being directed to the situation that extinction ratio is poor, can selecting before BS703, to place a polarizer 702, for improving the polarization state of polarization maintaining optical fibre 7011 further.The polarizer 702 needs directly to aim at the slow axis of polarization maintaining optical fibre 7011 or fast axle.

Fig. 8 A gives the third structure, and the PBS704 wherein in Fig. 7 changes employing Wollaston prism 804 into, and pairwise orthogonal polarization state can be realized directly to be divided into two different directions.Such as, it can realize two light beams to separate angle at 3.7 degree.Fig. 8 B gives the inner structure of double-fiber collimator 805 in a kind of Fig. 8 A, and its inside has a condenser lens 8051 for receiving two light beams, and realizes two light beams to focus in two optical fiber 8052 that are placed on focal plane.Condenser lens 8051 can be sphere lens, aspheric mirror, or gradient-index lens, and is placed in box 8053.A metallic sheath 8054 can be adopted for being fixed in same box 8053 by two optical fiber 8052.Between two optical fiber 8052, distance of separation can be 0.25mm, namely consistent with the diameter dimension of optical fiber.When the extinction ratio of system is poor, may be selected in and place a polarizer 802 before beam splitter (BS) 803, exporting polarization degree for improving polarization maintaining optical fibre 8011.The polarizer 802 is kept to aim at the slow axis (or fast axle) of polarization maintaining optical fibre 8011.

In Fig. 7 and Fig. 8, a depolarized light source can be adopted, as ASE light source.The tail optical fiber of light source uses single-mode optical fiber pigtail in this case.In addition, before beam splitter BS, need use one polarizer for being polarized input light.Need to allow that the transmission axle of the direction of the polarizer and polarization beam apparatus PBS or Wollaston prism is at 45 ° docks, divide by constant power to meet light.

This structure is adopted to comprise three major advantages.The first, because Wollaston prism is made by birefringece crystal, therefore, can ensure that it possesses high extinction ratio; The second, the use of two fiber collimating lenses simplifies the structure design and to axle problem; 3rd, the size of encapsulation can more miniaturization.Fig. 8 A gives the schematic diagram of operation, need in figure to ensure that the slow axis of polarization maintaining fiber pigtail 8011 of light source 801 is aimed at one of the s axle of BS803 and p axle diaxon, suitable rotation Wollaston prism 804 makes to go out at prism 804 output port, meets the two light beam constant power beam splitting that polarization state is orthogonal.Two polarization state compositions are all coupled to the slow axis of polarization maintaining fiber pigtail 8061 and 8062 or fast axle.Fiber optic loop 806 can adopt polarization-maintaining fiber coil or single-mode fiber ring.If use single-mode fiber ring, then need each use one depolarizer after polarization maintaining fiber pigtail.

Fig. 9 provides the 4th kind of structure of polarization structure fibre optic gyroscope, wherein by light source as superradiation light-emitting diode (SLD), one LED chip or semiconductor chip 901 are integrated in the same encapsulating structure of Fig. 7 or Fig. 8 A, simultaneously, by the rotation making a Wollaston prism 904 suitable, carry out beam splitting to make two orthogonal light of beam splitter (BS) 903 output port place polarization state with constant power.Can by dotted line frame in light-source encapsulation to Fig. 7.

Figure 10 gives the structural representation of the first Polarization device.Use a polarizer 1002 for Polarization below at quarter-wave plate 1001.The slow axis (or fast axle) of quarter-wave plate 1001 aligns with PBS704 in Fig. 7 or with the x-axis of the Wollaston prism 804,904 in Fig. 8 and Fig. 9, thus between x and y-polarisation state composition, introduce a pi/2 phase delay.As shown in Figure 10,45 degree are become to dock with the slow axis of quarter-wave plate 1001 transmission axle of the polarizer 1002.Use a photodetector 1003 for detecting the luminous power through the polarizer 1002, it is converted into electric signal by light signal.Can show that from formula (2) luminous power accepted on detector 1003 is identical with formula (11), its corresponding voltage V ₁can be expressed as:

$V_1=G_1({\mathrm{\αE}}_0^2/2)(1+sin\mathrm{\Δ}\mathrm{\φ})=V_{10}(1+sin\mathrm{\Δ}\mathrm{\φ}),---\left(17\right)$

Wherein G ₁for the transform electrical signals efficiency of receiving circuit, α is the depletion efficiency of light component, for the voltage of detector.Can obtain from formula (17), rotating the phase differential caused can be obtained by following formula:

Δφ＝sin ^-1(1-V ₁/V ₁₀)(18)

In formula (18), V ₁₀zero and obtain can be set to by the rotating speed of polarization structure fibre optic gyroscope (P-FOG) on demarcation turntable will be placed on, suppose that the luminous power having light source to export remains unchanged.A problem is there is and any optical power fluctuation will cause V in formula 18 ₁fluctuate, cause measuring error thus.In order to solve this problem, we need the second polarization analysis instrument structure used as shown in figure 11.In figure, the voltage of first photodetector 1103 generation still can by being that (17) represent, the voltage of second photodetector 1104 generation can be expressed as:

$V_2=G_2({\mathrm{\αE}}_0^2/2)(1-sin\mathrm{\Δ}\mathrm{\φ})=V_{20}(1-sin\mathrm{\Δ}\mathrm{\φ})---\left(19\right)$

The method of usual employing is the gain factor G2 of the gain circuitry regulating PD21104, makes V ₁₀=V ₂₀=V ₀, simultaneously at V ₁and V ₂between keep a difference, and then obtain rotate produce phase differential:

Δφ＝sin ^-1[(V ₁-V ₂)/(V ₁+V ₂)](20)

In above discussion, each detector all uses two independently multipliers, as illustrated in fig. 12.Can with use mimic channel or digital circuit realize excessively from formula (17) to the computation process (20).When using digital circuit, use analog-to-digital conversion and microprocessor, as FPGA or DSP.

Or, a balance detection circuit realiration can be used to carry out differential amplification to the photocurrent between PD1 and PD2, as shown in Figure 12 B:

V ₁₂＝G ₁₂(I ₁-I ₂)＝2G ₁₂I ₀sinΔφ,(21)

Wherein G ₁₂be balanced detector across resistance gain amplifier coefficient, V ₁₂for voltage results, I ₁and I ₂be respectively the photoelectric current that detector PD1 and PD2 receives:

$I_1={\mathrm{\β}}_1({\mathrm{\αE}}_0^2/2)(1+sin\mathrm{\Δ}\mathrm{\φ})=I_{10}(1+sin\mathrm{\Δ}\mathrm{\φ})---\left(22\right)$

$I_2={\mathrm{\β}}_2({\mathrm{\αE}}_0^2/2)(1-sin\mathrm{\Δ}\mathrm{\φ})=I_{20}(1-sin\mathrm{\Δ}\mathrm{\φ})---\left(23\right)$

Fluctuation and the relative intensity noise of light source power can be eliminated by balance detection circuit.Equally, the computation process of formula (24) can by the acquisition of mimic channel and digital circuit, or adopt the combination of optical gain device in Figure 12 B to realize.

The shortcoming of structure shown in Figure 11 is rotate the phase place produced more than 90 degree, as shown in formula (20) and (24), only can not to be applicable to the gyro output under dynamic range under little slewing rate or little.For gyro in large investigative range, the third structure as shown in fig. 13 that can be used.In such an embodiment, use a kind of beam splitter of polarization insensitive (BS) 1301 that incident beam is divided into two parts.In a first portion, after quarter-wave plate 1303, use a polarization beam apparatus (PBS) 1304 for polarization beam splitting.The slow axis of quarter-wave plate 1303 directly aligns with the PBS704x axle in Fig. 7 or aligns, for generation of the phase delay of pi/2 with the x-axis of Wollaston804 and 904 in Fig. 8 A and Fig. 9.In the second portion, a PBS1302 is used not comprise quarter-wave plate for polarization beam splitting.Similar with (23) to formula (22), the detection photocurrent in photo-detector PD113041 and photo-detector PD213042 is:

$I_1^{\′}={\mathrm{\β}}_1({\mathrm{\αE}}_0^2/4)(1+sin\mathrm{\Δ}\mathrm{\φ})=I_{10}^{\′}(1+\sin \mathrm{\Δ}\mathrm{\φ})---\left(25\right)$

$I_2^{\′}={\mathrm{\β}}_2({\mathrm{\αE}}_0^2/4)(1-sin\mathrm{\Δ}\mathrm{\φ})=I_{20}^{\′}(1-\sin \mathrm{\Δ}\mathrm{\φ})---\left(26\right)$

The photocurrent detected in PD3 and PD4 is

$I_3={\mathrm{\β}}_3({\mathrm{\αE}}_0^2/4)(1+cos\mathrm{\Δ}\mathrm{\φ})=I_{30}(1+cos\mathrm{\Δ}\mathrm{\φ})---\left(27\right)$

$I_4={\mathrm{\β}}_4({\mathrm{\αE}}_0^2/4)(1-cos\mathrm{\Δ}\mathrm{\φ})=I_{40}(1-cos\mathrm{\Δ}\mathrm{\φ})---\left(28\right)$

Regulate probe current parameter beta ₁, β ₂, β ₃, the I ' being ₁₀=I' ₂₀and I ₃₀=I ₄₀, balance gain, can obtain

V ₁₂＝G ₁₂(I′ ₁-I' ₂)＝G ₁₂I′ ₁₀sinΔφ(29)

V ₃₄＝G ₃₄(I ₃-I ₄)＝G ₃₄I ₃₀cosΔφ,(30)

Wherein G ₁₂and G ₃₄be respectively the transimpedance gain of the balance detection circuit of detector set (PD1, PD2) and (PD3, PD4) (13041,13042,13043,13044).Rotate the phase place produced can be expressed as

Δφ＝tan ^-1[V ₁₂G ₃₄I ₃₀/(V ₃₄G ₁₂I′ ₁₀)](31)

Regulating circuit gain G ₁₂and G ₃₄, make G ₃₄i ₃₀=G ₁₂i ' ₁₀, we can obtain

Δφ＝tan ^-1(V ₁₂/V ₃₄)(32)

From formula (29) to the process of formula (32), balance detection circuit as shown in Figure 12 B can be used.In addition, independently gain circuitry as illustrated in fig. 12 can also be used.This structure can suppress the change of light source light power, therefore, is applicable to high-precision fiber optic loop.Δ φ can be obtained by use formula (32).But the Δ φ produced at little rotating speed is used alone formula (29) and can obtains Δ φ.When the absolute value of Δ φ is close to pi/2, formula (30) may be used for obtaining Δ φ, because along with the change of Δ φ, formula (29) is at minimum sensitive spot place.Δ φ is asked in use formula (29) or (30), depends primarily on the absolute value of Δ φ.

Figure 14 A gives the 4th kind of structure of polaroid analyze, uses Wollaston prism 1403 to replace the PBS1102 in Figure 11 A in the structure shown here and uses dual chip photodetector 1404 to replace independent two detectors 1103 and 1104.The size of two detector chips 14041 and 14042 change from 50 microns to 500 microns in dual chip detector 1404, the distance spatially separated is about 50 to 500 microns.The size of chip and spacing other sizes near this scope are also fine.Two chips are kept apart mutually on circuit.Each polarized component scioptics of incident light are focused on 1401 to corresponding chip for generation of photocurrent.The advantage of this structure is the little and low price of size.In addition, Wollaston prism has better extinction ratio usually.Wollaston prism 1403 main shaft and quarter-wave plate 1402 direction relative to fiber optic loop front side polarization beam splitter or Wollaston prism (704 of such as Fig. 7 or 804 and 904 of Fig. 8 A, Fig. 9) x and y-axis is given in Figure 14 B.

Figure 15 A gives the 5th kind of structure of polaroid analyze, use two Wollaston prisms 1504 and 1506 to replace PBS1302 and 1304 in Figure 13 A in this structure, and use two two dual chip photodetectors 1505 and 1507 to replace four independently detectors 13041,13042,13023,13024.Figure 15 B gives Wollaston prism 1504 main shaft and quarter-wave plate 1503 direction relative to fiber optic loop front side polarization beam splitter or Wollaston prism (704 of such as Fig. 7 or 804 and 904 of Fig. 8 A, Fig. 9) x-axis and y-axis.Two Wollason prisms 1504 are identical with x with y direction with 1506.

Figure 16 gives the 6th kind of structure of polarization fiber gyroscope (P-FOG).In this structure, by the lineshaft registration of the input polarization of light source 1601 and polarization beam apparatus (PBS) 1603, it is made loss-freely to pass through PBS1603.Then light beam is losslessly by a polarization insensitive beam splitter 1604 and quarter-wave plate 1605, and is divided into two mutually orthogonal polarized lights by PBS1606.A photodetector 1611 can be used to receive the luminous power situation of beam splitter (BS) 1604 reflected light for detection light source 1601.Quarter-wave plate 1605 becomes 45 degree with the main shaft x-axis of PBS1606 with y-axis with input polarization.After light returns from fiber optic loop 1607, segment beam will be reflexed on the polarizer 1610 and photo-detector (PD) 1610 by BS1604.The polarizer 1609 and x and y-axis at 45 °.Other parts light through BS1604, all will be reflexed on photo-detector (PD) 1608 by PBS1603.Like this, the photocurrent produced at detector (PD) 1610 and detector (PD) 1608 can be expressed as:

$I_1^{\′\′}={\mathrm{\β}}_1({\mathrm{\α}}_1{E}_0^2/2)(1-sin\mathrm{\Δ}\mathrm{\φ})=I_{10}^{\′\′}(1-sin\mathrm{\Δ}\mathrm{\φ})---\left(33\right)$

$I_2^{\′\′}={\mathrm{\β}}_2({\mathrm{\α}}_2{E}_0^2/2)(1+cos\mathrm{\Δ}\mathrm{\φ})=I_{20}^{\′\′}(1+cos\mathrm{\Δ}\mathrm{\φ})---\left(34\right)$

Wherein β _ifor circuit gain, comprise the response of each detector PDi, α _ifor the loss of light i.Δ φ=0 when gyro is static, can obtain I " ₁₀with I " ₂₀, suppose that luminous power does not change.In order to avoid occurring drift about the error caused by luminous power, need the photocurrent I of use detector (PD) 1611 ₃.

Regulating circuit gain, meets I " ₃=I " ₁₀=I " ₂₀, then can obtain by rotating the rotation produced:

Δφ＝tan ^-1[(I″ ₁-I″ ₃)/(I″ ₂-I″ ₃)](35)

Because the delay of fiber optic loop cause detector (PD) 1611 and detector (PD) 1608 and detector (PD) 1610 and between there is larger relative delay, therefore the noise of light source too good general can worsen the measuring accuracy of Δ φ in formula (35).

In figure 16, light source 1601 can be integrated in empty frame with the form of a chip, reduces size and the price of system.In this case, to light source then without the need to polarization maintaining fiber pigtail.

Figure 17 gives polarization fiber gyrostatic 7th kind of structure, wherein adopts Wollaston prism 1706 to replace polarization beam apparatus in Figure 16 (PBS) 1606.Other all the same with the structure in Figure 16, therefore formula (33) is appointed and so can be suitable for.

Figure 18 gives polarization fiber gyrostatic 8th kind of structure.This structure is similar to the structure in Figure 17, replaces the polarizer 1710 in Figure 17 except adopting a Wollaston1811 prism and uses a pair of chip prober 1812 to detect the photocurrent of two polarization states exported by prism 1811.Also a polarization beam apparatus PBS prism can be used to replace Wollaston prism 1811.Under use polarization beam apparatus replaces Wollaston prism 1811 situation, photodetector use two be separated replaces dual chip detector 1812.Detector PD118121, PD218122 and PD31808 produce photocurrent J1, J2 and J3 and can be expressed as:

$J_1={\mathrm{\β}}_1({\mathrm{\α}}_1{E}_0^2/2)(1-sin\mathrm{\Δ}\mathrm{\φ})=J_{10}(1-sin\mathrm{\Δ}\mathrm{\φ})---\left(36\right)$

$J_2={\mathrm{\β}}_2({\mathrm{\α}}_2{E}_0^2/2)(1+sin\mathrm{\Δ}\mathrm{\φ})=J_{20}(1+sin\mathrm{\Δ}\mathrm{\φ})---\left(37\right)$

$J_3={\mathrm{\β}}_3({\mathrm{\α}}_3{E}_0^2/2)(1+cos\mathrm{\Δ}\mathrm{\φ})=J_{30}(1+cos\mathrm{\Δ}\mathrm{\φ})---\left(38\right)$

Circuit tuning gain makes J ₁₀=J ₂₀=J ₃₀=J ₀, can obtain

sinΔφ＝(J ₂-J ₁)/(J ₂+J ₁)(39)

cosΔφ＝[2J ₃/(J ₁+J ₂)-1](40)

$\mathrm{\Δ}\mathrm{\φ}={\tan }^{-1}\[\frac{J_2-J_1}{2J_3-(J_2+J_1)}\]---\left(41\right)$

Before calculating, current conversion can be become voltage.Formula (41) can be used for obtaining Δ φ.But, when a little slewing rate is with little Δ φ, now, only use formula (39) that Δ φ can be obtained.When the absolute value of Δ φ is close to pi/2, use formula (40) that can be independent is for obtaining Δ φ, because now along with the change of Δ φ, formula (39) sensitivity is minimum.So finally can choice for use formula (39) formula (40) for obtaining Δ φ, depend primarily on the order of magnitude of Δ φ.

At Figure 16, in 17 and 18, a depolarized light source can also be used, as ASE light source.Now, a single-mode optical fiber pigtail can be used to export for connecting light source.In addition, when the extinction ratio of the polarization beam apparatus (as 1603,1703,1803) near light source is poor, any polarizer (as 1602,1702 and 1802) can be connected at the input end of polarization beam apparatus and input light is polarized.

In order to increase the signal to noise ratio (S/N ratio) of detectable signal further, lock-in amplifier circuit can be used, as shown in two structures in Figure 19 A and 19B.In the structure shown here, lock-in amplify circuit produces a frequency is f ₀modulation signal be used for modulated light source export, with f ₀centered by narrow-band filtering is carried out to the signal that PD in testing circuit returns, and filtered signal to be returned in lock-in amplifier.During this design, photodetector, for exchanging AC coupling, drifts about and low-frequency noise for eliminating direct current DC.Modulation signal can adopt sinusoidal signal, square-wave signal, sawtooth signal, etc.The bandwidth of bandpass filtering is more roomy than the detection zone needed for gyro, in the magnitude of 1kHz.Because narrow-band filtering, detected noise signal can be reduced greatly.This phase-locked gain scheme can be used on other polarization gyroscope arrangement of providing in this patent.Light source can be taked the mode of external band tail optical fiber (as Figure 19 A) or be built in the mode (as Figure 19 B) not with tail optical fiber in polarization fiber gyroscope encapsulation box.

In some use, can increase by a phase-modulation for noise decrease in phase-locked gain, as shown in Figure 20 A and Figure 20 B.But increasing the cost that this phase-modulator can increase system, the result of the gyro simultaneously made becomes more complicated.Different from traditional interference type optical fiber gyroscope, the depth of modulation of polarization fiber gyro can be very little, because gyro is operated in the sensitiveest some position.Adopt phase-modulation and lock-in amplify, formula (17), (22), (23), (25) to (28), formula (33), formula (34) and formula (36) can eliminate automatically to the DC terms in formula (38).In this case, the structure in Figure 10, Figure 16 and Figure 17 is can meet completely.

Providing a kind of simple circuit in Figure 21 to rotate and the phase place of generation for solving in formula (29) and formula (30), wherein using V ₁and V ₂represent G ₁₂i ' ₁₀and G ₃₄i ₃₀, use φ (t) to represent Δ φ simultaneously.The hardware being core by FPGA electronic chip can realize this circuit.Use this circuit, the test of the large range of speeds can be obtained and there will not be non-linear.

In the example above, from fiber optic loop, export the detection of polarisation of light state can adopt a variety of method to realize.Some light polarization analysers or polarization device can be used in present polarization fiber gyro, and these instruments or equipment can provide by following patent.

1.X.SteveYao,USPatentNo.6,836,327,“In-lineopticalpolarimeterbasedonintegrationoffree-spaceopticalelements,”2004.

2.X.SteveYao,USPatentNo.7,372,568,“Lowcostpolametricdetector,”2008.

3.X.SteveYao,USPatentNo.7,436,569,“Polarizationmeasurementandself-calibrationbasedonmultipletunableopticalpolarizationrotators,”2008.

4.X.SteveYao,USPatentNo.7,265,837,“Sensitivepolarizationmonitoringandcontrolling,”2007.

Above list of references comprises:

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2.H.C.Lefevre,"Fundamentalofinterferometericfiberopticgyroscope,"inFiberOpticGyros:20AnniversaryConf.,Proc.SPIE2837,46-60(1996).

3.G.A.Sanders,B.Szafraniec,R.Y.Liu,M.S.Bielas,andL.Strandjord,"Fiber-opticgyrodevelopmentforabroadrangeofapplications,"Proc.SPIE,FiberOpticandLaserSensorsXIII2510,2-11(1995).

4.G.A.Sanders,B.Szafraniec,R.Y.Liu,C.L.Laskoskie,L.K.Strandjord,andG.Weed,"Fiberopticgyrosforspace,marine,andaviationapplications,"inFiberOpticGyros:20AnniversaryConf.,Proc.SPIE2837,61-67(1996).

5S.K.Sheem,“Fiber-opticgyroscopewith[3x3]directionalcoupler,”Apply.Phys.Lett.,Vol.37,pp.869-871(1980).

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8.Szafraniec,G.A.Sanders,Theoryofpolarizationevolutionininterferometricfiber-opticdepolarizedgyros,Journaloflightwavetechnology,1999,17(4).579-590.

Much concrete right descriptions is comprised in this patent, but these specific descriptions, comprise the power of having obtained in the text or by what be likely authorized to, be not used to the authority limiting this invention, and especially as the explanation to specific embodiments concrete function.In the context of independent embodiment, some described feature also can be used in the combination of single embodiment.On the contrary, those various features described in the context of single embodiment also can in many embodiment: with independent or to realize in any suitable sub-portfolio.Although feature may be described to particular combination above; even initial one or more feature advocated from requiring combination; can leave out from combination in some cases, and combination required for protection can directly apply to the variant of sub-portfolio or a combination.

Only only has the description of several example and embodiment.To described example and embodiment, other change, amendment and improvement can realize.

Claims (34)

1. carry out a method of rotating sensing based on polarisation of light state, it is characterized in that, the method comprises:

A branch of input light with input polarization is divided into two-beam, and wherein light beam is with the transmission of the first polarization state form, and the second bundle light is to transmit perpendicular to the second polarization state of the first bundle polarization state;

Light beam and the second bundle optically-coupled are entered the input/output port of the optical loop of a rotation, realize light beam to propagate with first direction in optical loop, and the second bundle light is propagated with the second transmission direction reverse with the first light beams transmission direction;

In optical loop input/output port, the first bundle and the second bundle light are carried out conjunction bundle, keep the first and second bundle polarization states mutually orthogonal simultaneously, interfere to avoid appearing at input/output port place two-beam, will the output signal of the light after bundle as optical loop be closed;

Detect optical output signal, obtain the information of optics output terminal polarization state; The polarization state information that optics exports is processed, determines the turn signal that optics ring experiences.

2. method as described in claim 1, it is characterized in that, described input light is a branch of linearly polarized light; The described light beam and second be divided into is restrainted light and is linearly polarized light, and described input line polarized light polarization direction becomes miter angle with the first bunch polarized light with the polarization direction of the second bunch polarized light.

3. method as described in the appended claim 1, it is characterized in that, the first light beam that described input light is divided into and the second light polarization are orthogonal two linearly polarized lights, or two orthogonal circularly polarized lights of polarization state.

4. as the method in claim 1, it is characterized in that, described optical loop is that fiber optic loop is formed, and described optical loop input/output port is fiber coupler.

5. method as described in claim 4, it is characterized in that, described fiber optic loop comprises the fiber optic loop that polarization maintaining optical fibre is made.

6. method as described in claim 1, it is characterized in that, described optical loop adopts an optical polarization beam splitter as input/output port, is used for incident light being divided into the two orthogonal polarized lights in bundle polarization direction, and is coupled in optical loop; Described optical loop is made up of reflective optical system, for by the two-beam of free space by reflecting to form optical loop.

7. method as recited in claim 6, is characterized in that, also comprise: in optical loop, the side of optical polarization beam splitter uses one 90 degree of faraday rotation mirrors, for ensureing the optics reciprocity in optical loop.

8. method as described in claim 1, is characterized in that, also comprising and carry out detection acquisition light output polarization state information to output light, is the polarization state of use one polarization analyzer determination light output.

9. method as described in claim 1, is characterized in that, described detection optical output signal, obtains the polarization state information of optical output signal, comprising: light output is beamed into four light signals; Measure four kinds of different Stokes' parameters that four road light beams obtain light beam respectively; Described obtained light output polarization state information to be processed, determine the rotation information that optical loop experiences, comprise: measured four groups of Stokes' parameters of not sharing the same light are processed to the output polarisation of light state determining optical loop, use the output polarization state of optics ring to determine the rotation information that optics ring experiences.

10. method as described in claim 1, is characterized in that, also comprise: in focus ring road, light Zhong mono-tunnels of the forward and reverse transmission of two bundles apply modulation signal; Use the modulation signal of a characteristic frequency and adopt the polarization state information of lock-in amplifier to light output to detect, to reduce detection noise.

11. methods as described in claim 10, is characterized in that, also comprise: before input light being beamed into light beam and the second bundle light, first carrying out modulation to input light and make it carry modulation signal to transmit.

12. methods as described in claim 11, is characterized in that, modulate the light source producing input light, make to input light, and light beam and the second bundle light all carry modulation signal.

13. methods as described in claim 10, comprise and modulating light beam, make it carry modulation signal.

14. 1 kinds are carried out based on polarisation of light state the optical gyroscope rotating sensing, it is characterized in that, comprise: an optical polarization beam splitting arrangement has input polarization input light by one is divided into two-beam, wherein light beam possesses the first polarization state and the second bundle light possesses the second polarization state, and the polarization state of this two-beam is orthogonal, one optical loop coupling access input-output device, by the first loop of this loop, the light beam transmitted in loop is received, by the second loop, the second bundle light transmitted in ring is transmitted, this second light beams is contrary with the transmission direction of light beam, optics input-output device is adopted to restraint carrying out from loop light beam out and the second bundle light conjunctions, keep simultaneously light beam and the second bundle polarisation of light state mutually orthogonal, to avoid interfering at output/input optical port position two light, finally the output signal of the light after bundle as optical loop will be closed, one checkout equipment is used for the output light of detecting optical loop, obtains the optical polarization information of light output, and processes the polarization state information of the output signal of optical loop, determine the turn signal that optical loop experiences.

15. optical gyroscopes as described in claim 14, is characterized in that, described input polarization is a linear input polarization, and its light beam be divided into all becomes the linearly polarized light of miter angle with the second bundle polarisation of light state with input polarization.

16. optical gyroscopes as described in claim 14, is characterized in that, the first light beam that input light is divided into and the second light polarization are orthogonal two linearly polarized lights, or two orthogonal circularly polarized lights of polarization state.

17. optical gyroscopes as described in claim 14, it is characterized in that, described optical loop is made up of the fiber optic loop of optical fiber coiling, comprises and adopts fiber coupler as output/input optical port equipment.

18. optical gyroscopes as described in claim 17, is characterized in that, its fiber optic loop adopts polarization maintaining optical fibre coiling to form.

19. optical gyroscopes as described in claim 14, is characterized in that, the optical loop of coupling access input-output device comprises one group of optical mirror and realizes light beam and the second bundle light being carried out reflecting to form an optical loop in free space.

20. optical gyroscopes as described in claim 14, it is characterized in that, a branch of optics input-output device having the input light of input polarization to be divided into two-beam is comprised a polarization beam apparatus or Wollaston prism by described its, the input beam beam splitting being used for being received is the orthogonal light beam of two bundle polarization states, and be coupled to two input ports of optical loop respectively, be formed in the two-beam that the direction of propagation in optical loop is contrary, return in polarization beam apparatus or Wollaston prism and carry out conjunction bundle; Also comprising described optical loop is polarization-maintaining fiber coil.

21. optical gyroscopes as described in claim 20, is characterized in that, increase a faraday rotation mirror or half-wave plate, for realizing the light path reciprocity of optical loop in optical polarization beam splitter or Wollaston prism point of beam optical path; What be also included in optical polarization beam splitter or Wollaston prism input/output port increases a non-polarizing beamsplitter from the input light path of light source, is used for the output light checkout equipment output light beam splitting with optical loop information returned from polarization beam apparatus or Wollaston prism outputted to for detecting optical loop.

22. optical gyroscopes as described in claim 14, is characterized in that, its output light for detecting optical loop comprises with the optical polarization information detecting apparatus obtaining light output: a beam splitter is used for optics to export to be divided into four light; Four detectors are respectively used to receive this four roads light, each detector receives the polarizer of front end placement through direction initialization of light, quarter wave plate is also placed in one of them polarizer front end, thus to obtain in four road light four different Stokes' parameters by the light intensity of measurement four road light; One processing unit is used for processing measured four different Stokes' parameters, determines the polarization state change that in optical loop, light signal exports, uses the polarization state of optical loop light output to change the turn signal finally determined in loop.

23. optical gyroscopes as described in claim 14, it is characterized in that, its output light for detecting optical loop comprises with the optical polarization information detecting apparatus obtaining light output: the slow axis (or fast axle) of a quarter wave plate aligns with the polarization direction of the light beam be divided in the polarization beam apparatus of the orthogonal two-beam of polarization state by the input light of optical gyroscope, be used for receiving the output light for detecting optical loop, and produce an output light; After a polarizer is placed on described quarter wave plate, it plays folk prescription and aligns to the slow axis of described quarter wave plate, is used for receiving the output light from quarter wave plate, and produces an output light; After a photo-detector is placed on the described polarizer, is used for receiving the output light from the polarizer, and converts the light received to electric signal, for polarization analysis.

24. optical gyroscopes as described in claim 14, it is characterized in that, its output light for detecting optical loop comprises with the optical polarization information detecting apparatus obtaining light output: slow axis or the fast axle of a quarter wave plate align with the polarization direction of the light beam be divided in the polarization beam apparatus of the orthogonal two-beam of polarization state by the input light of optical gyroscope one, be used for receiving the output light for detecting optical loop, and produce an output light; After a polarization beam apparatus or Wollaston prism are placed on described quarter wave plate, be used for the output light from quarter wave plate being divided into the two orthogonal output light in bundle polarization direction; A branch of output light of described polarization beam apparatus or Wollaston prism plays folk prescription and aligns to the slow axis of described quarter wave plate, is used for receiving the output light from quarter wave plate, and produces an output light; Other a branch of output light of described polarization beam apparatus or Wollaston prism plays folk prescription and plays folk prescription to vertical to the slow axis of described quarter wave plate; Photo-detector is placed on the output port of described polarization beam apparatus or Wollaston prism wherein a branch of output light, be used for receiving a branch of output light from polarization beam apparatus or Wollaston prism, and convert the light received to electric signal, for polarization analysis; Another one photo-detector is placed on the another one optical output port of described polarization beam apparatus or Wollaston prism, be used for receiving from other a branch of polarization state of polarization beam apparatus or Wollaston prism output light vertical with aforementioned output light, and convert the light received to electric signal, for polarization analysis.

25. optical gyroscopes as described in claim 14, it is characterized in that, its output light for detecting optical loop comprises with the optical polarization information detecting apparatus obtaining light output: a checkout equipment beam splitter is used for input light to be divided into two bundles according to a certain percentage; A quarter wave plate is used for receiving and exports light from first after the beam splitting of checkout equipment beam splitter, slow axis or the fast axle of described quarter wave plate align with the polarization direction of the light beam be divided in the polarization beam apparatus of the orthogonal two-beam of polarization state by the input light of optical gyroscope, be used for receiving the wherein light beam separated by beam splitter for the output light of detecting optical loop, and produce one and export light; After first polarization beam apparatus or Wollaston prism are placed on described quarter wave plate, be used for the output light from quarter wave plate being divided into the two orthogonal output light in bundle polarization direction; A branch of beam splitting light of described first polarization beam apparatus Wollaston prism plays folk prescription and aligns to the slow axis of described quarter wave plate, is used for receiving the output light from quarter wave plate, and produces a first polarization beam apparatus Wollaston prism first beam splitting light; Another bundle beam splitting light of described first polarization beam apparatus or Wollaston prism plays folk prescription and plays folk prescription to vertical to aforementioned beam splitting light light, is the first polarization beam apparatus Wollaston prism second beam splitting light; A first polarization beam apparatus first beam splitting photo-detector is placed on described first polarization beam apparatus transmitted light output port, be used for receiving the first beam splitting light from the first polarization beam apparatus or Wollaston prism, and convert the light received to electric signal, for polarization analysis; First polarization beam apparatus or Wollaston prism second beam splitting photo-detector are placed on described first polarization beam apparatus or Wollaston prism second beam splitting optical output port, be used for receiving the second beam splitting light from the first polarization beam apparatus or Wollaston prism, and convert the light received to electric signal, for polarization analysis; Second polarization beam apparatus or Wollaston prism are placed and are used for being divided into the orthogonal second polarization beam apparatus output light in two bundle polarization directions by exporting light from described detection beam splitter second; Two the second polarization beam apparatus or Wollaston prism detector are placed on two beam splitting optical output ports of described second polarization beam apparatus or Wollaston prism respectively, be used for respectively receiving and restraint beam splitting light from two of the second polarization beam apparatus or Wollaston prism, and convert the light received to electric signal, for polarization analysis respectively.

26. optical gyroscopes as claimed in claim 18, it is characterized in that, welding again after the mid point being also included in fiber optic loop blocks, rotates 180 ° by polarization maintaining optical fibre during welding, the fast axle of polarization maintaining optical fibre and slow axis are intersected align, in order to reduce the error of optical gyroscope.

27. optical gyroscopes as claimed in claim 20, is characterized in that, are also included in two input/output port that polarization beam apparatus or Wollaston prism be connected with polarization-maintaining fiber coil and install a polarizer respectively additional; Also be included in light source output terminal and install a light source input light polarizer additional, it plays folk prescription at 45 ° with an off-axis of polarization beam apparatus, is used for improving input polarisation of light degree; Also being included in the light source that light source output terminal installs additional exports between the light polarizer and the polarization beam apparatus be connected with polarization-maintaining fiber coil, install a non-polarizing beamsplitter additional, be used for the optical loop signal sent back by polarization beam apparatus to output to output light for detecting optical loop to obtain in the optical polarization information detecting apparatus of light output.

28. 1 kinds are carried out based on polarisation of light state the optical gyroscope rotating sensing, it is characterized in that: comprise a light source and send light beam, first polarization beam apparatus is entered into through first polarizer, transmitted light can be divided into a branch of first transmission-polarizing beam-splitting light first reflecting polarization beam splitting light vertical with the first transmission-polarizing beam-splitting light with a branch of polarization direction by described first polarization beam apparatus, wherein the off-axis that rises of first polarizer plays folk prescription to parallel with the transmission of the first polarization beam apparatus, can all through the first polarization beam apparatus through the light of first polarizer with guarantee, non-polarizing beamsplitter receives the first transmission-polarizing light from the first polarization beam apparatus, and described first transmission-polarizing light is divided into a branch of reflected light and through Beam, 3rd photo-detector receives the reflected light from point polarization beam apparatus, is used for the power swing change of surveillance light source, thus can eliminate the measuring error that optical power change may bring, second polarization beam apparatus is used for the transmitted light from non-polarizing beamsplitter being divided into a branch of second transmission-polarizing beam-splitting light second reflecting polarization beam splitting light vertical with described second transmission-polarizing beam-splitting light polarization direction with a branch of polarization state, between non-polarizing beamsplitter and the second polarization beam apparatus, place first quarter wave plate or the first faraday rotation mirror, it is at 45 ° that the optical axis direction of described first quarter wave plate or the first faraday rotation mirror and the transmission of the second polarization beam apparatus play off-axis direction, one is used for producing the polarization-maintaining fiber coil in the single loop of formation rotating sensing, its first port is connected with the transmission output port of the second polarization beam apparatus, be used for receiving the second transmission-polarizing light from the second polarization beam apparatus, and the slow axis of polarization maintaining optical fibre is consistent with the second transmission-polarizing polarisation of light direction, second port of described polarization-maintaining fiber coil is connected with the reflection output port of the second polarization beam apparatus, is used for receiving the second reflect polarized light from the second polarization beam apparatus, and the slow axis of polarization maintaining optical fibre is consistent with the polarization direction of the second reflect polarized light, first photo-detector, be used for receiving for receive reflect through non-polarizing beamsplitter, from close through the second polarization beam apparatus bundle, with fiber optic loop rotation information, again through the back light of the first quarter wave plate, and produce one first detection electric signal, second polarizer is placed between the first photo-detector and beam splitter, its rise the direction of off-axis and the second polarization beam apparatus to play off-axis direction at 45 °, second photo-detector is placed on a light output end of the first polarization beam apparatus, be used for receiving through the first polarization beam apparatus reflection, returned by non-polarizing beamsplitter transmission, from close through the second polarization beam apparatus bundle, with fiber optic loop rotation information, again through the back light of the first quarter wave plate, and produce one second detection electric signal, use the first and second detection electric signal to process, the rotation information of fiber optic loop can be analyzed.

29. as the optical gyroscope in claim 28, it is characterized in that, also comprising described second polarization beam apparatus is a Wollaston prism, restraint polarized lights for the light from the first quarter wave plate being beamed into polarization state orthogonal two by a double-fiber collimator and being coupled in polarization-maintaining fiber coil, and the combiner returned from polarization-maintaining fiber coil is got back to the first quarter wave plate.

30., as the optical gyroscope in claim 28, is characterized in that, also comprise described second polarizer and are replaced by second Wollaston prism, are used for the light from the second quarter wave plate being beamed into the orthogonal polarized light of two bundle polarization states; Also comprise the first photo-detector and be replaced with a dual chip photo-detector, be used for receiving the two-beam from described second Wollaston prism respectively, and produce two electric signal, for polarimetry to analyze the rotation information of fiber optic loop.

31., as the optical gyroscope in claim 14 or 28, is characterized in that, also comprise in an input/output port that modulation signal is applied in optical loop by a signal modulator; Also being included in detecting unit and using lock-in amplifier to apply the modulation signal of a characteristic frequency on detected output light, during for obtaining the polarization state information of light output, reducing detection noise.

32., as the optical gyroscope in claim 14 or 28, is characterized in that, also comprise a signal modulator and are applied to by modulation signal on light source output port; Also being included in detecting unit and using lock-in amplifier to apply the modulation signal of a characteristic frequency on detected output light, during for obtaining the polarization state information of light output, reducing detection noise.

33., as optical gyroscope in claim 28, is characterized in that, described to carry out modulation to input light be that light source produces a modulation input light, and make the light beam after inputting light and beam splitting, the second bundle light all carries modulation signal.

34. 1 kinds are carried out the structure of rotating sensing based on polarisation of light state, it is characterized in that, comprising:

One experiences the closed loop optical loop of rotation and comprises one in being positioned at the input/output port before closed loop optical loop, for receiving the input optical signal that has input polarization, input/output port using the optical signal in closed loop optical loop out as the output signal of closed loop optical loop; One detector cells is used for detecting output optical signal, obtains the polarization state information that light signal exports, instead of depends on the optical interferometer structure of connection one closed loop optical loop; One processing unit processes the polarization state information that obtained light signal exports, and determines the turn signal of closed loop optical loop.