CN210323604U - Single-axis Sagnac interferometer phase offset control device - Google Patents
Single-axis Sagnac interferometer phase offset control device Download PDFInfo
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- CN210323604U CN210323604U CN201921559871.1U CN201921559871U CN210323604U CN 210323604 U CN210323604 U CN 210323604U CN 201921559871 U CN201921559871 U CN 201921559871U CN 210323604 U CN210323604 U CN 210323604U
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Abstract
The utility model discloses a single-axis Sagnac interferometer phase offset control device, which comprises an optical pulse transmitter, an optical pulse receiver, a single-axis Sagnac optical fiber interferometer, a sensing optical cable, a light reflector and a polarization controller; the optical pulse transmitter, the polarization controller, the single-axis Sagnac optical fiber interferometer, the sensing optical cable and the optical reflector are sequentially connected, and the single-axis Sagnac optical fiber interferometer is also connected with the optical pulse receiver; the optical pulse signal processing device comprises an optical pulse transmitter, a polarization controller, a sensing optical cable, a light reflector, a single-axis Sagnac optical fiber interferometer and an optical pulse receiver, wherein the optical pulse transmitter is used for generating a pulse optical signal, the polarization controller is used for changing the polarization state of the input optical signal, the sensing optical cable is used for sensing a vibration signal, the light reflector is used for reflecting the optical signal, the single-axis Sagnac optical fiber interferometer is used for enabling the signals scattered and reflected in the sensing optical cable to generate. The utility model discloses can make the phase place of unipolar Sagnac interferometer bias near the expectation to obtain better small-signal response sensitivity.
Description
Technical Field
The utility model relates to an optical fiber sensing technical field especially relates to a unipolar Sagnac interferometer phase place offset controlling means.
Background
When fiber optic distributed sensing is used to detect cable vibrations, a uniaxial Sagnac fiber optic interferometer (also known as an unbalanced mach zehnder interferometer) configuration is often used. The simplest single-axis Sagnac fiber optic interferometer structure is composed of a set of optical splitters and a section of fiber delay line. In general, the set of optical splitters may be a combination of 2x2 optical splitters with 1 uniform splitting ratio and 1x2 optical splitters with 1 uniform splitting ratio, or a combination of 3x3 optical splitters with 1 uniform splitting ratio and 1x2 optical splitters with 1 uniform splitting ratio. If a combination of a 2x2 optical splitter and a 1x2 optical splitter is used, the theoretical static phase of the single-axis Sagnac fiber optic interferometer is pi or 0; the theoretical static phase of a single axis Sagnac fiber optic interferometer is 2 pi/3 or 4 pi/3 if a combination of a 3x3 optical splitter and a 1x2 optical splitter is used. In addition, because the additional phase of the optical splitter is influenced by many external factors such as temperature, the static phase of the single-axis Sagnac fiber optic interferometer is in a constantly changing state, for two beams of coherent light, the relation between the amplitude and the phase of the interference signal is a cosine function, and if the static phase is in the vicinity of pi or 0, the response under the condition of small signal is poor. So in order to achieve good signal response sensitivity in small signal situations, the ideal static phase should be offset at pi/2. At present, the method for solving the problem of the static phase of the uniaxial Sagnac fiber optic interferometer mainly adopts a phase modulation mode, needs to use a phase modulator, and has the advantages of large volume, high cost and complex scheme.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a unipolar Sagnac interferometer phase place offset controlling means can make the phase place offset of unipolar Sagnac interferometer near the expectation to obtain better small-signal response sensitivity.
In order to achieve the above purpose, the utility model provides a following technical scheme:
a phase offset control device of a single-axis Sagnac interferometer comprises an optical pulse transmitter, an optical pulse receiver, a single-axis Sagnac optical fiber interferometer, a sensing optical cable, a light reflector and a polarization controller;
the optical pulse transmitter, the polarization controller, the single-axis Sagnac optical fiber interferometer, the sensing optical cable and the optical reflector are sequentially connected, and the single-axis Sagnac optical fiber interferometer is also connected with the optical pulse receiver;
the optical pulse transmitter is used for generating a pulse optical signal, the polarization controller is used for changing the polarization state of the input optical signal, the sensing optical cable is used for sensing a vibration signal, the optical reflector is used for reflecting the optical signal, the single-axis Sagnac optical fiber interferometer is used for enabling signals scattered and reflected back in the sensing optical cable to generate interference, and the optical pulse receiver is used for converting the received pulse optical signal into an electric signal.
Optionally, the single-axis Sagnac fiber optic interferometer includes a 2x2 optical splitter, a 1x2 optical splitter, and a fiber delay line.
Optionally, the single-axis Sagnac fiber optic interferometer includes a 3x3 optical splitter, a 1x2 optical splitter, and a fiber delay line.
Optionally, the optical pulse transmitter sends out a single-polarization periodic optical pulse signal, the type of the adopted light source is F-PLD or SLD, and the working wavelength range is 1230nm to 1650 nm.
Optionally, the sensing optical cable is a single mode optical fiber.
Optionally, a period value range of the optical pulse signal transmitted by the optical pulse transmitter is 1 × 102μs～2×103μs。
Optionally, the value of the period of the optical pulse is greater than (L1+ L2)/50, where L1 is the length of the sensing optical cable, and L2 is the length of the optical fiber delay line.
Optionally, the emissivity of the light reflector is greater than-25 dB.
According to the utility model provides a concrete embodiment, the utility model discloses a following technological effect:
the utility model discloses a polarization controller changes the polarization state of the light signal who inputs unipolar Sagnac interferometer, makes the phase offset of unipolar Sagnac interferometer near the value of expectation to obtain better small-signal response sensitivity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of a prior art fiber optic cable vibration sensing architecture for a single-axis Sagnac fiber optic interferometer;
fig. 2 is a schematic structural diagram of the phase offset control device of the single-axis Sagnac interferometer of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
The utility model aims at providing a unipolar Sagnac interferometer phase place offset controlling means can make the phase place offset of unipolar Sagnac interferometer near the expectation to obtain better small-signal response sensitivity.
In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description.
The principle of the utility model is that:
typically, a single-axis Sagnac fiber optic interferometer consists of 1 uniform split ratio 2x2 splitter, 1 uniform split ratio 1x2 splitter and one fiber delay line, or 1 uniform split ratio 3x3 splitter, 1 uniform split ratio 1x2 splitter and one fiber delay line. The two ports on the A side of the 2x2 (or 3x3) optical splitter are respectively connected with an optical transmitter and an optical receiver; the 1 port on the B side of the 2x2 (or 3x3) optical splitter is connected with an optical fiber delay line and then connected to the 1 port on the A side of the 1x2 optical splitter; the 1 port on the B side of the 2x2 (or 3x3) optical splitter is connected to 1 port on the a side of the 1x2 optical splitter by a fiber stub (stub fiber); and the side port of the 1x2 optical splitter B is connected with a sensing optical cable.
When the optical fiber interferometer works, an optical signal transmitted by an optical transmitter enters the single-axis Sagnac optical fiber interferometer and then enters the sensing optical cable, and is reflected back by the optical reflector at the tail end of the sensing optical cable; the backscattered signal and the reflected signal in the sensing optical cable enter the single-shaft Sagnac optical fiber interferometer and then enter the optical receiver. The single-axis Sagnac fiber optic interferometer is used for enabling backward scattering signals and reflection signals in the sensing optical cable to interfere after passing through the fiber optic interferometer.
The utility model discloses a device and the system difference that the tradition used unipolar Sagnac fiber optic interferometer lie in: the output optical signal of the optical transmitter is a pulse optical signal in a single polarization state, and a polarization controller is added between the optical transmitter and the single-axis Sagnac fiber optic interferometer.
The specific method comprises the following steps: firstly, a periodic single-polarization pulse light signal is used as an input signal of a single-axis Sagnac optical fiber interferometer; at the optical receiver, receiving, amplifying, sampling and digitally processing three optical pulses reflected by an optical reflector at the tail end of the photosensitive cable, and calculating the phase bias state of the uniaxial Sagnac optical fiber interferometer according to signal amplitude values of the three optical pulses; then, by utilizing the characteristic that the additional phase of the optical splitter in the structure of the uniaxial Sagnac fiber optic interferometer is related to the polarization state of the input optical signal, the polarization state of the input optical signal is controlled by the polarization controller, so that the static phase of the uniaxial Sagnac fiber optic interferometer is always biased to be close to a desired value (such as pi/2).
The utility model has the advantages that: the phase offset of a single-axis Sagnac fiber optic interferometer can be brought to near a desired value using relatively simple control methods and low cost apparatus to achieve good sensitivity of fiber optic cable vibration detection.
Shown in fig. 1 is a schematic diagram of a current fiber optic cable vibration sensing architecture for a single-axis Sagnac fiber optic interferometer. The single-axis Sagnac fiber optic interferometer comprises 2x2 optical splitters with 1 uniform splitting ratio, 1x2 optical splitters with 1 uniform splitting ratio and a fiber delay line, wherein an optical transmitter and an optical receiver can be pulsed or continuous.
Shown in fig. 2 is the utility model discloses unipolar Sagnac interferometer phase place offset controlling means schematic structure, as shown in fig. 2, a unipolar Sagnac interferometer phase place offset controlling means contains 1 optical pulse transmitter, 1 optical pulse receiver, 1 unipolar Sagnac fiber optic interferometer, sensing optical cable, 1 light reflector and 1 polarization controller.
The optical pulse transmitter sends out a single-polarization periodic optical pulse signal, the optical pulse signal firstly passes through the polarization controller and then enters the sensing optical cable through the single-axis Sagnac optical fiber interferometer, the tail end of the sensing optical cable is connected with the optical reflector, a reflected signal generated by the optical reflector returns to the single-axis Sagnac optical fiber interferometer and then enters the optical pulse receiver, and then the optical pulse receiver amplifies the signal, performs digital/analog conversion and processes a digital signal.
In the process of the optical signal traveling, the optical pulse signal is divided into four paths according to different paths:
in path 1, an optical transmitter, a polarization controller, a 2x2 optical splitter, an optical fiber time delay line, a 1x2 optical splitter, a measured optical fiber, an optical reflector, a measured optical fiber, a 1x2 optical splitter, an optical fiber time delay line, a 2x2 optical splitter and an optical receiver; in path 2, an optical transmitter, a polarization controller, a 2x2 optical splitter, an optical fiber time delay line, a 1x2 optical splitter, a tested optical fiber, an optical reflector, a tested optical fiber, a 1x2 optical splitter, an optical fiber short connecting line, a 2x2 optical splitter and an optical receiver; in path 3, an optical transmitter, a polarization controller, a 2x2 optical splitter, an optical fiber short connecting wire, a 1x2 optical splitter, a tested optical fiber, an optical reflector, a tested optical fiber, a 1x2 optical splitter, an optical fiber time delay wire, a 2x2 optical splitter and an optical receiver; in the 4 th path, an optical transmitter, a polarization controller, a 2x2 optical splitter, an optical fiber stub, a 1x2 optical splitter, a tested optical fiber, an optical reflector, a tested optical fiber, a 1x2 optical splitter, an optical fiber stub, a 2x2 optical splitter and an optical receiver.
The path of the 2 nd and 3 rd signals is the same, but the directions are different, the optical path difference of the two paths of signals is smaller than the coherence length of the optical signals, interference is generated at the output end of the single-axis Sagnac optical fiber interferometer, and the interference signals can be used for detecting the vibration of the optical cable; the 1 st and 4 th path signals are different in walking distance, one path of optical signal passes through the optical fiber delay line twice, and the other path of optical signal does not pass through the optical fiber delay line.
After a light reflector connected to the tail end of the optical fiber reflects the pulse light signal, once a certain point in an optical fiber line has Fresnel reflection, starting from an optical transmitter, because the path of the optical signal which travels the 4 th path is shortest, the first path reaches an optical receiver, the path of the optical signal which travels the 1 st path is longest, the last path reaches the optical receiver, the path of the optical signal which travels the 2 nd and 3 rd paths is in the length of the two paths, and the second path reaches the optical receiver, the optical receiver receives three reflected signal light pulses because the optical reflector in the single-axis Sagnac optical fiber interferometer has an optical time delay line with a fixed length.
If the length of the optical fiber delay line is long enough, signals reflected by the optical reflector connected to the tail end of the sensing optical cable do not overlap when returning to the optical pulse receiver, and three pulse signals are obtained in the optical pulse receiver, wherein the three pulse signals are defined as follows according to the receiving time sequence: a first pulse signal, a second pulse signal, and a third pulse signal. In the received three reflected signal light pulses, the path taken by the first light pulse does not pass through an optical fiber delay line, and the path is shortest and reaches the first time; the path taken by the third light pulse passes through the optical fiber delay line twice, is longest and finally reaches the optical fiber delay line; the path of the second optical pulse only passes through one optical fiber time delay line, and the second optical pulse is obtained by the interference of two optical pulse signals with the same path and opposite directions and contains optical cable vibration information.
In the signal received by the optical pulse receiver, if the amplitude of the first pulse signal is a1, the amplitude of the second pulse signal is a2, and the amplitude of the third pulse signal is A3, they have the following relations:
A2＝A1+A3+2×(A1×A3)0.5×COS(θ)
and theta is the phase difference of the optical pulse signals with the same paths and opposite directions.
With a1, a2, A3, the magnitude of θ can be obtained, that is, the static phase of a single-axis Sagnac fiber optic interferometer can be calculated by measuring the amplitudes of three pulse signals.
The utility model discloses an among the optical cable vibration sensing structure who carries out unipolar Sagnac interferometer phase place offset control, because second light pulse contains optical cable vibration information, the range value A2 formed data that obtain after its sample can be used for the vibration that the representation sensing optical cable receives.
No matter what be used in unipolar Sagnac fiber optic interferometer is 2x2 optical divider or 3x3 optical divider, the additional phase place that its produced is very big with the light polarization state relation of input, and the optical receiver calculates the static phase value that obtains unipolar Sagnac fiber optic interferometer according to this characteristic, then adjusts polarization controller for the static phase value of unipolar Sagnac fiber optic interferometer reaches anticipated value, accomplishes unipolar Sagnac fiber optic interferometer's phase offset control function, uses the utility model discloses the concrete step of device is:
the optical pulse transmitter transmits a single-polarization optical pulse signal as an input signal of the single-axis Sagnac optical fiber interferometer;
at an optical pulse receiver, receiving, amplifying, sampling and digitally processing three optical pulses reflected by a reflector at the tail end of a photosensitive cable to obtain signal amplitude values of the three optical pulses, which are recorded as A1, A2 and A3 respectively;
according to the relation of A2, A1+ A3+2 (A1 × A3)0.5 × COS (theta), where theta is the phase of the optical pulse signals with the same paths and opposite directions, namely the phase of the uniaxial Sagnac fiber interferometer, and is referred to as a first phase offset of the uniaxial Sagnac fiber interferometer;
if the first phase offset of the single-axis Sagnac fiber optic interferometer is outside the set range (theta)0–a)～(θ0+ a) defining the phase bias of the single-axis Sagnac fiber optic interferometer in an unlocked state; changing the polarization angle of the optical signal by 1 step angle towards a certain direction (such as a positive direction) by using a polarization controller under the condition that the first phase bias of the Sagnac fiber optic interferometer is in an unlocked state, jumping to a step of calculating the phase theta of the uniaxial Sagnac fiber optic interferometer according to the relation A2 ═ A1+ A3+2 × (A1 × A3)0.5 × COS (theta), and obtaining the second phase bias of the uniaxial Sagnac fiber optic interferometer; then comparing the change directions of the second phase bias of the uniaxial Sagnac fiber optic interferometer; if the second phase bias of the uniaxial Sagnac fiber optic interferometer is changed toward the set bias value θ0Approaching, continuing to change the polarization angle of the optical signal to the above direction by using the polarization controller, and jumping to the step "calculating the phase θ of the uniaxial Sagnac fiber interferometer according to the relation A2 ═ A1+ A3+2 × (A1 × A3)0.5 × COS (θ)" until the obtained phase offset enters the set range (θ:) (θ 1 × A3)0–b)～(θ0Within + b); if the second phase bias of the uniaxial Sagnac fiber optic interferometer is changed from the set bias value theta0Then, the polarization controller is used to change the polarization angle of the optical signal by 1 step angle in the direction opposite to the above-mentioned one direction (for example, negative direction), and the process proceeds to the step "a 2 is a relation a1+ A3+2 × (a1 × A3)0.5 × COS (θ), and the phase θ of the uniaxial Sagnac fiber optic interferometer is calculated" until the obtained phase offset falls within the set range (θ)0–b)～(θ0Within + b); once the obtained phase offset enters a set range (theta)0–b)～(θ0Within + b), the change of the polarization angle of the optical signal is stopped, and the phase bias of the uniaxial Sagnac fiber optic interferometer enters a locking state; wherein, pi/3>a>b>π/30。
The utility model discloses a working parameter that device used:
the light source type adopted by the optical pulse transmitter is F-PLD or SLD, and the working wavelength range is 1230nm to 1650 nm.
The sensing optical cable adopts a single mode optical fiber for communication.
The period T of the emitted light pulse is 1 × 102μs～2×103And μ s, the value of the optical pulse period needs to take the length L1 of the sensing optical cable and the length L2 of the optical fiber delay line into consideration, the value T of the optical pulse period is greater than (L1+ L2)/50, the unit of L1 and L2 is m, and the unit of T is μ s.
The value range of the optical pulse width t is 50 ns-20000 ns, the length L2 of the optical fiber time delay line needs to be considered, so that when the optical pulse receiver receives three pulses reflected by the optical reflector connected to the tail end of the sensing optical cable, the three pulses can be completely distinguished in time, the value of the optical pulse width t is smaller than L2/5, the unit of L2 is m, and the unit of t is ns.
The emissivity of the light reflector is greater than-25 dB.
The invention discloses the following technical effects:
the polarization controller is used for changing the polarization state of the optical signal input to the uniaxial Sagnac interferometer, so that the phase of the uniaxial Sagnac interferometer is biased to be close to an expected value, and better small-signal response sensitivity is obtained.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principle and the implementation of the present invention are explained herein by using specific examples, and the above description of the embodiments is only used to help understand the method and the core idea of the present invention; meanwhile, for the general technical personnel in the field, according to the idea of the present invention, there are changes in the concrete implementation and the application scope. In summary, the content of the present specification should not be construed as a limitation of the present invention.
Claims (8)
1. The phase offset control device of the uniaxial Sagnac interferometer is characterized by comprising an optical pulse transmitter, an optical pulse receiver, the uniaxial Sagnac optical fiber interferometer, a sensing optical cable, a light reflector and a polarization controller;
the optical pulse transmitter, the polarization controller, the single-axis Sagnac optical fiber interferometer, the sensing optical cable and the optical reflector are sequentially connected, and the single-axis Sagnac optical fiber interferometer is also connected with the optical pulse receiver;
the optical pulse transmitter is used for generating a pulse optical signal, the polarization controller is used for changing the polarization state of the input optical signal, the sensing optical cable is used for sensing a vibration signal, the optical reflector is used for reflecting the optical signal, the single-axis Sagnac optical fiber interferometer is used for enabling signals scattered and reflected back in the sensing optical cable to generate interference, and the optical pulse receiver is used for converting the received pulse optical signal into an electric signal.
2. The single-axis Sagnac interferometer phase bias control device of claim 1, wherein the single-axis Sagnac fiber optic interferometer includes a 2x2 optical splitter, a 1x2 optical splitter, and a fiber delay line.
3. The single-axis Sagnac interferometer phase bias control device of claim 1, wherein the single-axis Sagnac fiber optic interferometer includes a 3x3 optical splitter, a 1x2 optical splitter, and a fiber delay line.
4. The phase offset control device of the single-axis Sagnac interferometer of claim 1, wherein the optical pulse transmitter emits a single-polarization periodic optical pulse signal, the type of the adopted light source is F-PLD or SLD, and the operating wavelength range is 1230nm to 1650 nm.
5. The single-axis Sagnac interferometer phase bias control device of claim 1, wherein the sensing cable is a single mode fiber.
6. The single-axis Sagnac interferometer phase bias control device of claim 4, wherein the period of the optical pulse signal transmitted by the optical pulse transmitter ranges from 1x 102μs～2×103μs。
7. The single-axis Sagnac interferometer phase bias control device of claim 4, wherein said optical pulse period value is greater than (L1+ L2)/50, wherein L1 is the length of the sensing cable and L2 is the length of the optical fiber delay line.
8. The single-axis Sagnac interferometer phase bias control device of claim 1, wherein the emissivity of the light reflector is greater than-25 dB.
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| CN110501819A (en) * | 2019-09-19 | 2019-11-26 | 桂林聚联科技有限公司 | A kind of single shaft Sagnac interferometer phase bias controller and method |
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| CN110501819A (en) * | 2019-09-19 | 2019-11-26 | 桂林聚联科技有限公司 | A kind of single shaft Sagnac interferometer phase bias controller and method |
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