Fiber-optic oscillator


(57) Abstract:

Fiber-optic oscillator can be used in the transducers of physical quantities to measure temperature, pressure, acceleration. The oscillator contains a fiber-optic laser, one end of the optical fiber is coupled to the collimator forming a parallel beam of light to the reflecting surface of the microcavity. The second end of the optical fiber, an output, forms together with the reflecting surface of the microcavity two-mirror optical resonator fiber optic laser. The reflective surface of the microcavity is under some given angle to the axis of the beam. Self-oscillating mode in the system of fiber-optic laser - microresonator is due to modulation of the amplitude of the reflection coefficient of the optical resonator fiber laser or q-switching two-mirror optical resonator due to photoinduced angular deviations of one of the mirrors, which serves as the reflecting surface of the microcavity. Stable measurement results. 2 Il.

The invention relates to fiber optic priorisation, excited by light.

The creation of a new class of fiber-optical oscillator based on micromechanical resonator (Mr) and optical coherent radiation interacting with MP. In the literature reported the development of various schemes for optical excitation of vibrations Mr and their practical implementation.

In all cases, the intensity modulation of optical radiation occurs at the resonance frequency of the MRI.

When it absorbs MP optical radiation of its illuminated side is experiencing thermal expansion, resulting in Mr occurs bending moment varying in phase with the modulated optical radiation, which leads to mechanical vibrations at the resonance frequency of the MRI.

External influences (temperature, pressure, acceleration, etc.) is converted into the internal stress MRI, which leads to change of its own resonant frequency determined by the dimensions of the Mr and its physical properties.

In connection with the small amplitude oscillations Mr ( 0.1 ám) in the oscillator is applied interferometric method for obtaining information about the resonances of h is retronym mirror, either end of the light conductor, paired with a reflective surface Mr.

Direct communication with a digital measuring device without converting the analogue-dial, large extent of the optical transmission channel, high potential accuracy of the measurement of the resonance frequency make this type of sensors is promising.

However, a microresonator oscillator based on photometric Mr excitation and optical detection of oscillations, have the following disadvantage.

The position of the working point of A Fabry-Perot interferometer unstable and shift depends both from the drift of the main characteristics of the Mr, and the instability of the radiation source and the parameters of the Fabry-Perot interferometer. In other words, the performance of the oscillator is affected by both the instability characteristics of the channel of the Mr excitation and channel interferometric information retrieval that requires special measures to stabilize the position of the working point A.

Closest to the proposed technical solution to the technical essence and the achieved results is a fiber optic sensor (WATER) physical led is microresonator with the reflecting surface, the photodetector and the spectrum analyzer.

The known solution is characterized by the following negative characteristics:

- high stability requirements power source (the pump current of the laser diode) and careful control of the operating point of the Fabry-Perot interferometer due to changes in the small limits of optical radiation power incident on Mr;

additional loss of optical power caused by the presence of the necessary discrete elements forming an additional feedback channel in the electronic circuit;

- stringent requirements on the stability characteristics of the resonator Fabry-Perot, and characteristics of Mr in because of the limited possibilities of their correction in this electronic scheme;

- limited adjustment of the working point of the Fabry-Perot interferometer by changing the wavelength of the optical radiation of the laser diode when implementing complex electronic circuits reverse the positive connection.

The problem solved by this invention is the development of a microresonator oscillator on the basis of fiber-optic laser and the q-switching two-mirror optical resonator wines the end of a single-mode optical fiber is interfaced with the collimator, forming a parallel light beam on the reflective surface Mr, oriented at an angle to the optical axis of the incident beam, and the second is the output.

Changing the output power with the reflection from the Mr results, due to the effect of photoinduced deformation, to the modulation of the deflection angle of the reflected beam (t), i.e., the modulation of optical power.

As a collimator uses a gradient rod lens (GSL) and a quarter of a period, forming a Gaussian beams.

Regardless of the topology and design of the Mr under certain conditions in the considered scheme is established self-oscillating mode with frequency F, which practically coincide with the resonant frequency f = f

These conditions are formulated in the following way:

in the initial state, the deflection angleandthe reflective surface Mr is in the interval1and2limits (1,2) depend on the characteristics of Mr and optical fiber laser;

resonance frequency of the Mr is close to the frequency of the relaxation oscillations of fiber-optic laser fRelor its harmonics, i.e., f nfRelwhere n = 1,2,3... Note that fRelthe Oprah
- average radiation power exceeds a certain threshold level is dependent on characteristics of the Mr and fiber laser.

As a result of the system Mr - fiber-optic laser self-oscillations at the resonant frequency of the Mr, there is no need to introduce interferometric feedback stabilization of the operating point of the oscillator.

The solution of this problem is provided by the fact that in a microresonator optical fiber oscillator containing a source of optical radiation, microresonator, as the source of optical radiation used fiber-optic laser, one end of the optical fiber is coupled to the collimator interposed between this end and the microcavity, and the second end of the fiber is an output, while the reflective surface forms a microcavity with an output end of the optical fiber, the two-mirror optical resonator fiber laser and the reflecting surface of the microcavity in the initial position is oriented to the optical axis of the collimated beam at some given angleand. Optical radiation optical fiber laser using a gradient rod Lin is Roy makes with the optical axis of the incident beam some angleandwhen the output signal of the oscillator is simulated resonant frequency of the Mr due to modulation of the q-switched two-mirror optical resonator fiber laser.

The essence of the proposed solution is the development of a microresonator optical fiber oscillator, in which the excitation of self-oscillations uses fiber-optic laser without introducing additional optical fiber devices, while for the existence of oscillatory modes in the system fiber-optic laser - microresonator sufficient modulation amplitude reflection coefficient R of the optical resonator fiber-optic laser arising from the fluctuations of the microcavity.

Fiber optic laser is a segment of single-mode type optical fiber of length L, the pumping can be performed in various ways, for example through the segment buffer of non-activated fiber, is perfectly consistent with carbon fiber.

The unique properties of the fiber-optic laser to achieve the effective optical approval of Mr with fiber-optic laser, and t is istoricheskikh materials such as Si, SiO2, CaAs allow you to implement the Mr structure with the specified acoustic performance and topology (for example, in the form of micromembrane, micromastia, microconsole and so on), allowing the system Mr - fiber-optic laser self-oscillations, resonance frequency which depends on the impact of relevant external factors (temperature, pressure, acceleration, and others).

In Fig. 1 presents a diagram of a microresonator optical fiber oscillator of a new type, where 1 - fiber-optic laser, erbium activated, pumped at a wavelength ofn= 0.98 μm, 2 - single-mode fiber, 3 - collimator, which was applied gradient rod lens in the fourth period, forming a Gaussian beams with parameters : diameter of the waist of the beam 2 Wo= 780 μm, the angle of divergence 2 = 2,6 10-3happy 4 - mirror M1optical resonator, which serves as the interface of the fiber-air, 5 - microresonator representing silicon membrane (micromattic, there), obtained by means of anisotropic etching, 6 - angleandbetween the normal to the reflective surface Mr and optical axis of the light beam, to form the device operates as follows.

Part of the power of the optical beam generated by the collimator 3, is reflected from the surface 7 of the microcavity 5, the normal to which in the initial position is the angleandwith the axis of the beam of light, and back into the resonator fiber laser.

Changing the output power fiber-optic laser W1falling on MRI results due to the effect of photoinduced deformation to the modulation of the deflection angle of the reflected beam (t) i.e., modulation of [(t)].

In Fig. 2 shows the experimental dependence (). Experimental results showed that regardless of the topology and design of MRI while performing the specified conditions (which were discussed above) in the device is self-oscillating mode with a frequency of Mr f F.

The experimental results obtained for the Mr in the form of micromastia size 1650 x 400 x 6 μm3with a film of Nickel (Nias reflective coatings MP. The film thickness was hNi0.3 μm, the reflection coefficient is 72%. Due to the considerable width of the Mr ensured its effective interaction with the optical beam. In the present case was instituted self-oscillations with frequencies F1= 35,5 to the activity was 1.5...4 mW, the ratio of signal to noise in the system 40...50 dB. The amplitude of Mr was 30 nm. Q-switched data modes measured with the acoustic excitation of vibrations, was 90 and 120, respectively.

As can be seen from Fig. 2, the region of existence of self-oscillations (1,2for the main oscillation modes is located entirely on one branch of the curve ().

This indicates that the q-switched optical resonator caused by the modulation of the beam deflection angles, and not an extra focusing (defocusing) due to the curvature of the surface of the Mr with self-excited oscillations. In addition, the experiment showed that when the dimension of H as in the submicron range, and significantly ( 1.5 mm) breakdown of self-oscillations were observed, with the relative change of the frequency F/F was 310-4. Within the interval (1,2) observed weak dependence of F(and), the nature of the monotony of which depends on the angular and linear geometric parameters describing the spatial orientation of the optical beam relative to the MP. Width of interval = O2-O1depends on the angle of divergence of the beam, and the greater the angle of divergence, the less the width of the interval. If this method of excitation of self-oscillations for the effective interaction of fiber-optic laser microcavity requires the use of detergents sizes, comparable to the diameter of the collimated beam. The linear increase of the geometrical sizes of a microresonator converters leads to significant changes of the conversion.

Thus, a new principle of construction of a microresonator optical fiber oscillator, thus to stabilize the operating point of the oscillator does not require the introduction of additional optical devices in the optical fiber laser.

Self-oscillating mode in the system of fiber-optic laser - Mr is carried out by modulation of the amplitude of the reflection coefficient R of the optical cavity fiber laser, or the q-switching two-mirror optical resonator due to photoinduced angular deviations of one of the mirrors, which serves as the reflective surface Mr.

Fiber-optic oscillator containing a laser source of the optical radiation from the optical fiber and microresonator, and one end of the light guide is associated with a collimator interposed between this end and the microcavity, and the second end of the fiber is an output, wherein the laser source opticoat with the exit end of the light guide two-mirror optical resonator fiber laser, and the reflecting surface of the microcavity in the initial position is oriented to the optical axis of the collimated beam at some given angleand.


Same patents:

The invention relates to fiber-optic transducers of physical quantities (temperature, pressure, acceleration, and other) using micromechanical resonators excited by light

The invention relates to the field of hydro-acoustics and can be used in laboratory and field conditions to measure sound waves in the liquid

The invention relates to medicine and can be used in medical practice to improve the laser beam on the biologically active points of the body

The invention relates to optical observation devices and can be used in cases when the input part of the Supervisory device is located at a considerable distance from the observer, for example for monitoring of a helicopter cabin space under the cabin of the helicopter

The invention relates to devices, fiber optics and can be used to connect the optical fiber with another optical fiber or optical element, for example with gradient lens

The invention relates to fiber-optic transducers of physical quantities (temperature, pressure, acceleration, and other) using micromechanical resonators excited by light

The invention relates to apparatus for determining the damage on the ship, for example, the hull of the vessel containing the distributed optical fiber located near the hull, and these optical fibers are attached to the Central unit, suited for the characterization of optical fibers on the mode of transmission of light to determine the damage to the hull

FIELD: instrument engineering.

SUBSTANCE: converter can be used for measuring parameters of acoustic fields in gases and liquids. Fiber-optic converter has optical radiation source exciting circuit, optical radiation source, optical coupler, auxiliary optical radiation, fiber-optic light guide made in form of cylindrical two-channel coaxial tied structure, which has rod single-mode waveguide and tubular single-mode waveguide. Device also has optical radiation divider, which divides optical radiation from rod waveguide and tubular waveguide, optical radiation receiver for receiving optical radiation from output of rod waveguide , additional optical radiation receiver which receives optical radiation from output of tubular waveguide, and analog signal processing unit.

EFFECT: improved precision of fiber-optic converter.

3 dwg

FIELD: measurement technology; electric-power industry; geological prospecting; aircraft industry.

SUBSTANCE: device can be used for inspecting deformations in big structures, for measuring temperature modes of transformers and temperature distributions along wells and for checking structural deformations in flying vehicles. Device has comparator, pulse former and pulse sampling unit for selecting optical pulses after they were reflected from reference point. As reference points the optical connectors are used mounted among sections of fiber-optic cable, which is used as measuring transformer. Selected pulses run auto-oscillating mode through positive feedback circuit. Oscillation repetition period defines delay in propagation of optical signal to selected reference point. Changes in temperature and influence of mechanical stresses resulting to deformation of optical fiber change refraction factor of material of optical fiber core. Due to change in refraction factor the delay of optical signal changes. Value of temperature or value of deformation acting on any section of measuring transformer are determined by change in delay of optical signals from any reference point.

EFFECT: simplified design; improved precision; widened dynamic range of operation.

2 dwg

FIELD: measuring technique.

SUBSTANCE: fiber-optic deformation sensor comprises generator of sinusoidal signals that modulates the intensity of laser emitter and spectrum analyzer that is used for determining the resonance frequencies of the signal of back scattering from the measuring converter. The values of the resonance frequencies are related to the mechanical deformation of different zones of the structure that is provided with the measuring converter.

EFFECT: reduced measurement time.

3 dwg

FIELD: oil-gas industry, possible use for diagnostics of extensive objects used during operation of wells or during transportation of product to collection stations and further, etc.

SUBSTANCE: method for monitoring status of extensive objects includes equipping extensive object with sensitive optical fiber, producing a series of coherent optical impulses with length T with spectrum width about 1/T and temporal interval between impulses equal to T1, organization of reflection-metric channel and feeding aforementioned impulses into sensitive optical fiber with length L, registration of amplitude of reverse dissipation signals, comparative analysis of aforementioned reverse dissipation signals in serial reflectograms and selecting local changes in them, pointing at presence of influence on extensive object, while coordinate of position of influence resulting from presence of selected local changes along the length of sensitive optical fiber is determined by position of changes on reflectogram, while a condition is maintained, in accordance to which length L of sensitive optical fiber is such, that temporal interval T1 between impulses exceeds value 2L/V, where: V-speed of light in sensitive optical fiber, while registration of amplitude of reverse dissipation signal is performed by means of photo-receiver with temporal resolution not worse than duration of impulse T. The method is realized by means of an appropriate device.

EFFECT: decreased requirements to coherence of impulse source of optical radiation used during diagnostics (width of optical impulse spectrum may be equal to about 1/T); increased number of measuring channels and working length of sensitive optical fiber.

2 cl, 3 dwg

FIELD: laser technology; measuring technique.

SUBSTANCE: device and method can be used for fiber-optic measurement of spatial distribution of temperature/deformation of elongated objects, namely, it can be used in oil industry, power engineering, automotive industry for monitoring of deformations in structures of bridges, supports and buildings. System has radiation source - laser - optically connected with optical fiber (with diameter of 150-600 mcm and diameter of core of 12-20 mcm) composed of point detectors on base of Bragg fiber arrays, reflecting light at different resonant wavelengths; fiber beam-splitting unit; spectrum analyzer in for of photoreceiver. Detectors with different reflection factors and/or with different width and shape of spectrum reflection alternate in optical fiber to follow preset order, including selection into groups. Detectors are recorded in thick optical fiber by laser at wavelength of 240-270 nm and at power of 0,5 W and higher. They also van be recorded through protecting polymer envelope disposed onto light guide by means of laser radiation at wavelengths of 270-450 nm and at power of 1 W and higher. Uniformity and stability of recorded Bragg array is improved.

EFFECT: improved reliability; reduced cost; higher speed of operation; increased sensitivity of array to environment influence.

4 cl, 2 dwg

FIELD: invention refers to measuring technique.

SUBSTANCE: sensor of measuring of deformation has at least one sensor element which provides changing of quantity of passing light at changing curvature of light guide. Sensor element is confined in body fulfilled with possibility of impacting on sensor element from one side with aid of pusher in shape of at least from one side of elastic wall of body or with aid of pusher passing through wall of body and having possibility to impact on sensor element and from other side with aid of support in shape of immovable wall of body. Pusher ensures perception of deformation of medium and/or deformation of surface, and body ensures possibility of switching of at least one light guide for supply light from source of light to sensor element and discharge of output light from sensor element.

EFFECT: invention is assigned for accommodation of optical sensor for measuring of deformation of elements of building constructions including reinforced concrete.

19 dwg

FIELD: physics.

SUBSTANCE: fibre-optic temperature sensor has a capillary inside of which there is optical fibre and a light-reflecting element which is placed at a distance from the butt end of the optical fibre. According to the first version, the sensor has a housing with a through hole and two blind holes coaxial with the through hole. In one of the blind openings there is a thread for a screw whose end is inserted into the through hole and has a light-reflecting butt end. In the opposite threaded blind hole there is an iron ring rigidly attached to the housing with a capillary inside which is also inside the through hole. According to the second version, the fibre-optic temperature sensor has a housing with a through hole and two blind holes coaxial with it. In each of the blind holes there is an iron ring with a capillary inside, where the capillary is also inside the through hole. One of the iron rings is rigidly attached to the housing. According to the third version, a fibre-optic deformation sensor has capillary inside of which there is an optical fibre and a light-reflecting element which is fitted at a distance from the butt end of the optical fibre. The sensor has a dumbbell shaped housing with cylindrical outer surfaces. On the surfaces of the ends of the housing there are threads, with a right-handed thread on one end and a left-handed on the other.

EFFECT: increased measurement accuracy, protection of the sensor from external mechanical effects, possibility of attaching the housing of the sensor to measurement objects, shorter time for transfer of temperature from objects to sensor elements and transfer of deformation of the material of objects to active elements of the sensor.

17 cl, 5 dwg

FIELD: physics.

SUBSTANCE: fibre-optic position sensor has a magnetic or electromagnetic element, a broad-band light source, optical fibre, at least two sensors in form of a fibre-optic Bragg grating made from optical fibre, at least one segment of magnetostrictive material, a rod made from magnetic field impermeable material. At least one of the two sensors is attached to the segment of the magnetostrictive material, where at least one of the segments of magnetostrictive material is attached to the rod. The magnetic or electromagnetic element and the rod are superposed in such a way that they experience displacement only along the axis of the rod. Said displacement causes changes in the dimensions of the segment of magnetostrictive, which leads to changes in the length of waves reflected by the sensors in form of a fibre-optic Bragg grating.

EFFECT: ensuring safety when using the sensor in explosion hazard zones owing to absence of electrical signals in the immediate proximity of the measurement point.

16 cl, 11 dwg

FIELD: physics.

SUBSTANCE: optical reflectometre generates a probing pulse which falls on a first examined Bragg grating through a circulator. Part of the probing pulse is reflected from the grating and falls on reference gratings whose reflection spectra lie equidistant from the spectrum of the examined Bragg grating. Two reflected signals are generated, having power which is determined by the spectral interval between the spectrum of examined grating and the spectrum of the corresponding reference grating. Reflected signals are returned to the reflectometre and are displayed on a reflectogram in form of two peaks whose amplitude is proportional to the power of these signals. The spectrum of the examined grating shifts in case of an external physical effect. One of the peaks increases while the other falls. The difference between the amplitude of these peaks is the picked up signal. In order to pick up signals of the next groups of examined fibre Bragg gratings, the reference Bragg gratings are rearranged so that the initial resonance wavelengths of the examined fibre Bragg gratings are exactly between the resonance wavelengths of reference Bragg gratings.

EFFECT: wider measurement range and high resistance to amplitude noise.

8 dwg

FIELD: physics.

SUBSTANCE: reflectometer has a pulse modulator and a pulsed radiation source connected to each other and a means of facilitating bidirectional transmission of radiation. The means of facilitating bidirectional transmission of radiation is connected to the pulsed radiation source, a sensitive fibre and through a photodetector to a control and processing unit, which is connected to the input of the pulse modulator. The connection between the means of facilitating bidirectional transmission of radiation and the pulsed radiation source is in form of two optical paths formed by two optical splitters. One of the splitters is connected to the output of the pulsed radiation source and the other to the means of facilitating bidirectional transmission of radiation. One of the optical paths has a delay line and the other has a phase modulator connected to the control and processing unit.

EFFECT: improved invention.

9 cl, 2 dwg

FIELD: the invention refers to the mode of manufacturing lens in the shape of peaks on the end-faces of single-mode and multi-mode optical fibers.

SUBSTANCE: the manufacturing mode is in plotting drops of polymerized substance on the end-face plane of the fiber, radiation of the plotted drop with a source of light for realization light photo polymerization. At that before exposure they choose one or several desired modes subjecting the optical fiber to mechanical strains, at the stages of plotting the drop and radiation they execute control and management of the form and the sizes of the peak, before the radiation stage they hold out the mixture at the given temperature for achieving viscosity of the mixture which allows to get the needed height of the drop, regulate duration of exposure and/or intensity of the light for regulating the end radius of the curvature of the peak.

EFFECT: provides possibility to get peaks of different heights and different radiuses on the end-face planes of the optical fibers and also provides possibility to control the indicated parameters of the peaks in time of their manufacturing.

26 cl, 13 dwg

FIELD: electrical engineering .

SUBSTANCE: device for introduction of laser emission in fibre, which contains optical single-mode or multimode fibres equipped with microlenses that are shaped of transparent materials, differs because microlenses are made of optical glass, refractive exponent of which is higher than the refractive exponent of light conducting thread of fibre, in the shape of sphere that embraces light conducting thread at the end of fibre, and the end surface of fibre is made in the form of polished cylindrical surface, besides, axis of cylindrical surface intersects with fibre axis and is perpendicular to fibre axis.

EFFECT: increases coefficient of emission introduction and reduces dependency of introduction coefficient on misalignment.

5 cl, 5 dwg

FIELD: physics; optics.

SUBSTANCE: invention relates to devices for splitting optical fibres, specifically to manual portable instruments. The mechanism for breaking optical fibres contains apparatus for breaking fibres and one or more clamping elements which can clamp an optical fibre at one end, which should be cut off, and apply a pulling force so as to stretch the fibre when breaking it. The mechanism is designed such that, the clamping element(s) can also push the broken part of the fibre using devices which enable the clamping element(s) to continue applying a pulling force to the cut off part of the fibre after breaking. The clamping element or each clamping element releases the cut off part when moving the cut off part of the fibre.

EFFECT: high quality joining and reliability of fibres.

11 cl, 15 dwg

FIELD: physics.

SUBSTANCE: fibro-optical connector comprises first and second half-couplings to receive first and second sections of optical fiber. First and second pairs of step-down optical multilayer transformers are arranged on end faces of said sections. Air gap is arranged between outer layers of said first and second pairs of said transformers. Layers of first and second pairs of aforesaid transformers are made from materials with differing indices of reflection and are counted from outer layers of aforesaid transformers in direction of the end faces of connected sections of optical fiber. Thickness of every layer makes one fourth of average signal wave λ0 transmitted over optical fiber, while the number of layers is selected subject to conditions covered by invention claim.

EFFECT: reduced power loss, expanded performances.

4 cl, 9 dwg