CN201522765U - Optical fiber intrusion alarm system - Google Patents

Abstract

The utility model discloses an optical fiber intrusion alarm system. Vibration caused by an intrusion source intervenes into a light circuit structure of a full optical fiber system, the optical fiber intrusion alarm system comprises a laser light source, a photoelectric detector, an industrial computer, an alarm system, a coupler, a delay coil, a sensing optical fiber, an optical fiber reflector and the intrusion source, and the optical fiber reflector is connected with the 3*3 optical fiber coupler via a single bundle of sensing optical fibers. Response of sensing optical fibers in different time to sound pressure leads optical paths relative to an inference system to be different, phase change of inference signals finally shows different light intensities, and intrusion source disturbance characteristics can be obtained and real-time alarm can be achieved through terminal optical-to-electrical conversion and phase demodulation. The optical fiber intrusion alarm system has the advantages that the optical fiber intrusion alarm system detects large-range defense areas, is suitable for severe weather and special terrains, and is high in sensibility, long in service life and low in maintenance cost.

Description

The optical fiber type intrusion alarm system

Technical field

The utility model relates to a kind of optical fiber type intrusion alarm system, belongs to the safety precaution field.

Background technology

Existing security and guard technology product, comprise with infrared system the most commonly used, traditional mature technology that video frequency pick-up head is representative, with leaky cable, tension force iron wire etc. is the innovative techniques of representative, with the advanced optical fiber technical products that with the sensor fibre is representative, various technology, have his own strong points, on using based on complementation; But on some application of special occasions, the optical fiber type intrusion alarm system has the advantage that can't replace; In addition, though there are indivedual external products technical ripe relatively, in the great circuit monitoring system acquisition that relates to country and national economy safety, the principle of government, military service is to adopt home products as far as possible; Adopt the mode of electricity for some, make up the technical scheme of distributed sensing point as cable and electronic component, need electromagnetic radiation shielding, prevent the application of static at some, or underwater use, these systems will show the defective of embodiment costliness, complexity especially, even may not use.

Induction optical cable class warning system is representative with Australian FFT company fiber fence product, be used for Pentagon's circumference security protection, but this product adopts technology path to determine system itself can't shield Temperature Influence fully, and layout difficulty (needs three optical cables greater than the optical fiber type intrusion alarm system, optical fiber type intrusion alarm system technology only needs one), simultaneously, imported product costs an arm and a leg, and has hindered its further popularization.

The utility model content

In order to overcome the deficiencies in the prior art, the utility model provides a kind of optical fiber type intrusion alarm system.

Its structural relation is: fibre reflector is connected with single bundle sensor fibre with fiber coupler, between fibre reflector and SLED LASER Light Source, be provided with time-delay coil and coupling mechanism, photodetector is connected with the industrial computer data acquisition channel, industrial computer is connected with the warning system output circuit, just can be perceived fast as long as the little vibration in invasion source acts on sensor fibre, its signal is handled the back by alarm software and is reported to the police by warning system.

Its principle of work is: because the vibration that cause in the invasion source gets involved the light channel structure of full fibre system, the sensor fibre of different time makes the optical path difference difference of interference system coherent light beam to the response of acoustic pressure, the phase change of interference signal finally shows as the difference of light intensity, by terminal opto-electronic conversion and phase demodulating, can obtain invading source perturbation features and warning.

Wherein feedback loop fiber optic interferometric system constitutes (its system architecture as shown in the figure) by SLED LASER Light Source, 3 * 3 optical fiber directional couplers, photodetector, fibre reflector and single-mode fiber etc., utilize single only 3 * 3 fiber couplers structure optical interference circuit, make the light that reflects through different paths arrival fibre reflectors form different light beams, two relevant light beams are back to coupling mechanism formation interferes.

The optical fiber inner light beam is through behind the coupling mechanism, a part arrives fibre reflector by the fibre delay line circle behind time delay τ, another part directly arrives fibre reflector, when reflected light turns back to coupling mechanism, owing to transmit the difference of distance, mainly obtain the light of following several different transmission path.

(1)2-5-6-5-(1-4) _N-3；

(2)2-(4-1) _N-5-6-5-3；

(3)2-5-6-5-3；

(4)2-(4-1) _N-5-6-5-(1-4) _M-3。

Light path approach subscript N, M represents the number of times of light path round-trip delay coil.

The electric field of this four road light is respectively

E ₁＝E ₀?exp{-i[kNl ₀+2kS(t-Nτ)]}

E ₂＝E ₀?exp{-i[kNl ₀+2kS(t)]}

E ₃＝E ₀?exp{-i[2kS(t-Nτ)]}

E ₄＝E ₀?exp{-i[k(N+M)l ₀+2kS(t-Nτ)]

Wherein, k=2 π/λ, S (t) is an invasion source disturbing signal, l ₀Be fibre delay line circle length, τ is the time that light is getted over the fibre delay line circle.

Because adopt semiconductor laser SLED light source, the coherent length of light source is less, above four bundle light only have the light path of (1), (2) two-beam process close, in coupling mechanism, can produce stable interference.Remaining because optical path difference (integral multiple of about fibre delay line circle length) is far longer than the coherent length of light source, can not obtain stable interference through the light beam of (3), (4) route.In addition, notice that (1), (2) are if middle light path all comes and goes repeatedly through the time-delay coiler part, also can form interference, but owing to repeatedly come and go fiber coupler, the light amplitude fading is bigger, the interference strength that the interference strength that forms forms during with (1), (2) two-way light path N=1 is compared less, can ignore.

Light beam along path (1) transmission vibrates its phase change because sensor fibre produces under the effect of invasion source

$\mathrm{\Δ}{\mathrm{\φ}}_1=\frac{4\mathrm{\π}(s_1-s_0)}{\mathrm{\λ}}---\left(41\right)$

In the formula, s ₀Effective length when not having external disturbance for sensor fibre; s ₁The effective length of sensor fibre when acting on the light beam arrival sensor fibre that transmits in path, lower edge (1) for the invasion source.

Correspondingly, the light beam phase change of (2) transmission along the path

$\mathrm{\Δ}{\mathrm{\φ}}_2=\frac{4\mathrm{\π}(s_2-s_0)}{\mathrm{\λ}}---\left(42\right)$

So two-beam is back to the phase differential of coupling mechanism place formation

${\mathrm{\Δ\φ}}^{\′}={\mathrm{\Δ\φ}}_1-{\mathrm{\Δ\φ}}_2=\frac{4\mathrm{\π}(s_1-s_2)}{\mathrm{\λ}}---\left(43\right)$

Ignore the time of light by fiber coupler coupled zone length, then two-beam arrives s respectively ₁And s ₂The time of differing of position is the time of light through the time-delay coil

τ ₀＝nL ₀/c (44)

In the formula, L ₀Be fibre delay line circle length.

Because the light velocity is exceedingly fast, be example with 1km fiber delay time coil, the elapsed time is about 5 μ s, can think τ ₀→ 0, so have

$s_1-s_2=\frac{s_1-s_2}{{\mathrm{\τ}}_0}\·{\mathrm{\τ}}_0=\underset{\mathrm{\Δt}=t_0\→0}{\lim }\frac{\mathrm{\Δs}}{\mathrm{\Δt}}\·{\mathrm{\τ}}_0=V\left(t\right){\mathrm{\τ}}_0---\left(45\right)$

In the formula, the sensor fibre axial vibration speed that V (t) causes for the invasion source.

By principle of interference as can be known, the interference light intensity that forms at the coupling mechanism place is

I＝A|E ₀ ²|{1+cos[Δφ′(t)+φ ₀]} (2.52)

Wherein: A is system constants,

Be the light path phase differential that causes of invasion source disturbance,

For two paths of signals poor because of the proper phase that light path causes.By output signal is carried out demodulation, just can obtain original invasion disturbing signal S (t).

Owing to adopted above technical scheme, the utlity model has following beneficial effect:

(1) system is a sensing unit with the optical cable, utilizes extraneous vibration that the single cover of the change realization main frame of light characteristic is reached the detection in defence area on a large scale of 80 kilometers distances, has broken through 67 kilometers technical bottleneck in the world;

(2) adopt optical cable as passive detector, effectively avoided the thunder and lightning interference, place such as be applicable to inflammable and explosive, strong electromagnetic and set up defences under water;

(3) be applicable to various complex-terrains, be not subjected to the environmental restraint such as height, complications of landform, broken infrared ray, microwave wall etc. and only be applicable to the limitation that sighting distance and flat site use, can realize effective detection irregular circumference defence area;

(4) be fit to weather extremes, be not subjected to the influence of natural climates such as high temperature, low temperature, high light, dust, rain, snow, mist, frost;

(5) adopt the interference-type optical fiber sensing technology, optical cable has high sensitivity, promptly can be laid immediately on the various iron net iron skills, also can directly be embedded in various ground even following, forms hidden guard system;

(6) long service life, sensing optic cable were 30 years, and maintenance cost is low.

Description of drawings

Fig. 1 is the structural representation of the utility model optical fiber type intrusion alarm system.

In the drawings: 1-SLED LASER Light Source, 2-photodetector, 3-industrial computer, 4-warning system, 5-3 * 3 fiber couplers, 6-time-delay coil, 7-sensor fibre, 8-fibre reflector, 9-invade the source

Embodiment

With reference to Fig. 1, the optical fiber type intrusion alarm system that the utility model provides comprises LASER Light Source 1, photodetector 2, industrial computer 3, warning system 4, coupling mechanism 5, time-delay coil 6, sensor fibre 7, fibre reflector 8 and invasion source 9, between fibre reflector 8 and 3 * 3 fiber couplers 5 with single bundle sensor fibre 7 connections, between fibre reflector 8 and SLED LASER Light Source 1, be provided with time-delay coil 6 and 3 * 3 fiber couplers 5, photodetector 2 is connected with industrial computer 3 data acquisition channels, industrial computer 3 is connected with warning system 4 output circuits, just can be perceived fast as long as invasion source 9 enters sensor fibre 7, reported to the police by warning system 4 in the processed back of its signal.

It should be noted that at last: above embodiment only in order to the explanation the utility model and and the described technical scheme of unrestricted the utility model; Therefore, although this instructions has been described in detail the utility model with reference to each above-mentioned embodiment,, those of ordinary skill in the art should be appreciated that still and can make amendment or be equal to replacement the utility model; And all do not break away from the technical scheme and the improvement thereof of spirit and scope of the present utility model, and it all should be encompassed in the claim scope of the present utility model.

Claims (4)

1. optical fiber type intrusion alarm system, comprise LASER Light Source, photodetector, industrial computer, warning system, coupling mechanism, time-delay coil, sensor fibre, fibre reflector and invasion source, it is characterized in that: be connected with single bundle sensor fibre between fibre reflector and 3 * 3 fiber couplers.

2. optical fiber type intrusion alarm system as claimed in claim 1 is characterized in that: be provided with time-delay coil and 3 * 3 fiber couplers between fibre reflector and SLED LASER Light Source.

3. optical fiber type intrusion alarm system as claimed in claim 1 is characterized in that: photodetector is connected with the industrial computer data acquisition channel.

4. optical fiber type intrusion alarm system as claimed in claim 1 is characterized in that: industrial computer is connected with the warning system output circuit.