CN204229090U - Free Spectral Range is tunable Mach-Zehnder fibre optic interferometer - Google Patents

Abstract

The tunable Mach-Zehnder fibre optic interferometer of a kind of Free Spectral Range, comprises the 3dB polarization-maintaining fiber coupler of 2 2*2,1 variable optical delay line, wire jumper.The first input end mouth of the first coupling mechanism is connected with laser instrument, 3rd input port of the first coupling mechanism is connected with variable optical delay line with the first input end mouth of the second coupling mechanism, the four-input terminal mouth of the first coupling mechanism is connected with wire jumper with the second input port of the second coupling mechanism, and final output is the 3rd port and the 4th port of the second coupling mechanism.The beneficial effects of the utility model are: realize simple, with low cost, utilize polarization-maintaining fiber coupler to add fibre delay line and construct tunable Mach-Zehnder fibre optic interferometer, overcome the problem that existing Mach-Zehnder fibre optic interferometer effectively can not realize free spectrum adjustment on a large scale.

Description

Free Spectral Range is tunable Mach-Zehnder fibre optic interferometer

Technical field

The present invention relates to the tunable Mach-Zehnder fibre optic interferometer of a kind of Free Spectral Range.

Background technology

Mach-Zehnder fibre optic interferometer (MZI) is the instrument utilizing interference of light principle to make, and has that volume is little, lightweight, compact conformation, good insulating, electromagnetism interference and a sensitivity advantages of higher, day by day comes into one's own.Mach-Zehnder fibre optic interferometer has been widely used in the full-fiber sensor measuring systems such as pressure magnetic field, refractive index, microseismic activity, micrometric displacement, laser phase noise, frequency noise, and light carries the optical fiber telecommunications system of millimeter wave, microwave.For high performance measuring system and optical fiber telecommunications system, strict requirement is proposed to the Free Spectral Range of fibre optic interferometer.But current existing Mach-Zehnder fibre optic interferometer mainly manufactures with Integrated Optics Method, its Free Spectral Range is only to realize tunability among a small circle or to fix certain value, and with high costs.

Summary of the invention

Technical matters to be solved by this invention is, a kind of tunable Mach-Zehnder fibre optic interferometer utilizing polarization-maintaining fiber coupler to add fibre delay line structure is provided, overcomes the problem that existing Mach-Zehnder fibre optic interferometer effectively can not realize free spectrum adjustment on a large scale.

For solving the problems of the technologies described above, the invention provides the tunable Mach-Zehnder fibre optic interferometer of a kind of Free Spectral Range, it is characterized in that, comprising: the 3dB polarization-maintaining fiber coupler of 2 2*2,1 variable optical delay line, wire jumper; The first input end mouth of the first coupling mechanism is connected with laser instrument, 3rd input port of the first coupling mechanism is connected with variable optical delay line with the first input end mouth of the second coupling mechanism, the four-input terminal mouth of the first coupling mechanism is connected with wire jumper with the second input port of the second coupling mechanism, and final output is the 3rd port and the 4th port of the second coupling mechanism.

Preferably, the connection of fiber port uses FC/APC flange head.

Preferably, optical fiber is the polarization maintaining optical fibre of slow axis alignment, and the tail optical fiber length of optical delay line offset by wire jumper, ensures that the optical path difference of two-arm is 0.The adjustment of Free Spectral Range was realized by the time delay of control lag line and wire jumper, and two-arm time delay that can regulate is 0-300ps, thus makes the frequency tuning of free spectrum frequency range be 3GHz-+ ∞ Hz.

Beneficial effect of the present invention is: realize simple, with low cost, utilize polarization-maintaining fiber coupler to add fibre delay line and construct tunable Mach-Zehnder fibre optic interferometer, overcome the problem that existing Mach-Zehnder fibre optic interferometer effectively can not realize free spectrum adjustment on a large scale.

Accompanying drawing explanation

Fig. 1 is the structural drawing of the tunable Mach-Zehnder fibre optic interferometer of Free Spectral Range of the present invention.

Fig. 2 is the Free Spectral Range schematic diagram based on Mach-Zehnder fibre optic interferometer of the present invention.

Embodiment

As shown in Figure 1, a kind of Free Spectral Range is tunable Mach-Zehnder fibre optic interferometer, is characterized in that, comprising: the 3dB polarization-maintaining fiber coupler of 2 2*2,1 variable optical delay line, wire jumper; The first input end mouth of the first coupling mechanism is connected with laser instrument, 3rd input port of the first coupling mechanism is connected with variable optical delay line with the first input end mouth of the second coupling mechanism, the four-input terminal mouth of the first coupling mechanism is connected with wire jumper with the second input port of the second coupling mechanism, and final output is the 3rd port and the 4th port of the second coupling mechanism.

The connection of fiber port uses FC/APC flange head.Optical fiber is the polarization maintaining optical fibre of slow axis alignment, the tail optical fiber length acting as counteracting optical delay line of wire jumper, ensures that the optical path difference of two-arm is 0.The adjustment of Free Spectral Range was realized by the time delay of control lag line and wire jumper, and two-arm time delay that can regulate is 0-300ps, thus makes the frequency tuning of free spectrum frequency range be 3GHz-+ ∞ Hz.

Three-dB coupler 2 3., the electric field strength E of 4. output port ₃, E ₄for:

$\left[\begin{array}{c}{E}_3\\ E_4\end{array}\right]=\frac{1}{2}{E}_1\left[\begin{array}{c}\exp [-{\mathrm{ik}}_{0}n(L+\mathrm{C\τ})]-\exp (-{\mathrm{ik}}_0\mathrm{nL})\\ -i\left\{\exp \right[-{\mathrm{ik}}_{0}n(L+\mathrm{C\τ})]+\exp (-{\mathrm{ik}}_0\mathrm{nL})\}\end{array}\right]---\left(1\right)$

Wherein: k ₀for light is in the propagation constant of vacuum, k ₀=2 π/λ; τ=Δ L/C, wherein f is the frequency of light, and unit is Hz; C is the light velocity, and size is 3 × 10 ⁸meter per second; Δ L is the optical path difference in the upper and lower two-arm of interferometer, and unit is rice; L is the length of wire jumper, and n is the refractive index of optical fiber; And luminous power is: P=E ₁ ^*e ₁/ 2.

Corresponding power transfer function is: $\left[\begin{array}{c}{P}_3\\ P_4\end{array}\right]=P_1\left[\begin{array}{c}{\sin }^2\left(\frac{k_0\mathrm{nC\τ}}{2}\right)\\ {\cos }^2\left(\frac{k_0\mathrm{nC\τ}}{2}\right)\end{array}\right]=\frac{P_1}{2}\left[\begin{array}{c}1-\cos \left(k_0\mathrm{nC\τ}\right)\\ 1+\cos \left(k_0\mathrm{nC\τ}\right)\end{array}\right]---\left(2\right)$

If ignore loss, the output-transfer function of interferometer can be:

The feature of the transmission spectrum of the Mach-Zehnder fibre optic interferometer that the 3dB polarization-maintaining fiber coupler of 22 × 2 is formed is a series of transmision peak equidistant at frequency domain and depends on Δ L, above formula Taylor series expansion can be obtained Free Spectral Range, i.e. adjacent transmission peaks peak frequency interval

Although the present invention illustrates with regard to preferred implementation and describes, only it will be understood by those of skill in the art that otherwise exceed claim limited range of the present invention, variations and modifications can be carried out to the present invention.

Claims (1)

1. the tunable Mach-Zehnder fibre optic interferometer of Free Spectral Range, is characterized in that, comprising: the 3dB polarization-maintaining fiber coupler of 2 2*2,1 variable optical delay line, wire jumper; The first input end mouth of the first coupling mechanism is connected with laser instrument, 3rd input port of the first coupling mechanism is connected with variable optical delay line with the first input end mouth of the second coupling mechanism, the four-input terminal mouth of the first coupling mechanism is connected with wire jumper with the second input port of the second coupling mechanism, and final output is the 3rd port and the 4th port of the second coupling mechanism.