CN205426774U - Protect inclined to one side photonic crystal optic fibre hydrogen sensor based on polarized light is interfered - Google Patents

Abstract

The utility model discloses an is protect inclined to one side photonic crystal optic fibre hydrogen sensor based on polarized light is interfered by broadband light source, transmission fiber, polarization controller, PM PCF, the pdAg hydrogen sensitive membrane, two -dimentional optic fibre anchor clamps, the constant temperature air chamber, the spectrum appearance is constituteed. Does the light beam of broadband light source transmission pass through the PM that incides behind the polarization controller adjustment polarization state PCF, PM PCF's the slow axis outside is evenly sputtered the pdAg hydrogen sensitive membrane and has been covered the half of periphery. It is different to the influence that fast slow axis birefringence led to the fact that the coating film distribution of optic fibre surface results in the pdAg hydrogen sensitive membrane to inhale the hydrogen inflation along the axial asymmetry, and the the polarization direction and the phase place of slow axis light change, and fast axis light state remains unchanged. Two transfer mode take place to interfere in transmission fiber, and spectrum is received by the spectrum appearance. The pdAg hydrogen sensitive membrane is very sensitive to hydrogen, consequently interferes spectrum drift volume can accurately reflect environment hydrogen concentration. This invents simple structure, and sensitivity is high, and temperature drift is little, provides the realistic plan for hydrogen concentration on -line monitoring.

Description

A polarization-maintaining photonic crystal fiber hydrogen sensor based on polarization interference

technical field

The utility model belongs to the technical field of optical fiber hydrogen sensing, in particular to a polarization-maintaining photonic crystal optical fiber hydrogen sensor based on polarized light interference.

Background technique

Hydrogen (H ₂ ) has a high energy density, and its combustion products are non-toxic and harmless. It is recognized as the most promising secondary energy source in the 21st century. Under the conditions of room temperature and standard atmospheric pressure, the explosive concentration range of hydrogen is very wide (4%~74.2%), the ignition energy is extremely small (0.02mJ), and the strong flammability and explosiveness have great influence on the safety, reliability and Higher requirements are put forward for the response ability of ultra-low concentration hydrogen.

Optical hydrogen sensors, especially fiber optic hydrogen sensors, use light as a medium for hydrogen concentration sensing. Since there are no electrical components in the sensing part, it has the advantages of intrinsic explosion-proof, high sensitivity, and immunity to electromagnetic interference. It has attracted widespread attention in recent years. and research. The common fiber grating type hydrogen sensor requires additional temperature compensation measures to suppress the temperature drift of the central wavelength, the detection accuracy is not high, and there is also the problem of temperature cross-sensitivity.

Polarization-maintaining photonic crystal fiber (PM-PCF) is a photonic crystal fiber with polarization-maintaining characteristics. The photonic crystal structure around the fiber core combined with stress rods produces a uniform stress birefringence effect, which can maintain the polarization state of polarized light in the same place for a long distance. , its good temperature characteristics are conducive to the production of optical fiber devices that are not sensitive to temperature, can effectively simplify the instrument structure, and improve the stability of the device.

Contents of the invention

In view of the deficiencies in the prior art, the purpose of this utility model is to provide a polarization-maintaining photonic crystal fiber hydrogen sensor based on polarization interference, which can reflect the hydrogen concentration through the drift of the interference wave trough wavelength. Excellent, can effectively reduce the adverse effects of ambient temperature fluctuations on hydrogen concentration detection.

The utility model is realized through the following technical solutions: a polarization-maintaining photonic crystal fiber hydrogen sensor based on polarization interference, which consists of a broadband light source (1), a transmission fiber (2), a polarization controller (3), and a PM-PCF (4) , Pd/Ag hydrogen sensitive film (5), two-dimensional optical fiber fixture (6), constant temperature gas chamber (7), spectrometer (8); the broadband light source (1) is connected to the polarization controller (3) through the transmission optical fiber (2) ), the polarization controller (3) is connected to the left end of the PM-PCF (4) through the transmission fiber (2), and the right end of the PM-PCF (4) is connected to the spectrometer (8) through the transmission fiber (2); among them, the PM-PCF ( 4) A Pd/Ag hydrogen sensitive film (5) is uniformly sputtered on the outside of the slow axis to form a hydrogen sensitive head, and the two-dimensional optical fiber fixture (6) fixes the PM-PCF (4) in a constant temperature gas chamber ( 7) Bottom.

The length of the PM-PCF (4) is 30mm-50mm, the coating length of the Pd/Ag hydrogen-sensitive film (5) is 20mm-30mm, the film thickness is 40nm-50nm, and the mass fraction of Ag is 20%-40%.

The preferred model of the polarization-maintaining photonic crystal fiber selected by the PM-PCF (4) is PM-1550-01, and the working wavelength is 1550nm.

The working principle of the utility model is: the broadband light source (1) emits a light beam with a wavelength of 1500nm~1600nm, adjusts the polarization state through the polarization controller (3), and then enters the PM-PCF along the transmission fiber (2). Since the Pd/Ag hydrogen-sensitive film (5) is evenly sputtered on the outside of the slow axis of PM-PCF (4) and covers half of the outer circumference, the coating distribution on the cladding surface is asymmetrical along the axial direction, and the Pd/Ag hydrogen-sensitive film (5) After absorbing hydrogen and causing volume expansion, the air holes in the extruded cladding can have different effects on the birefringence effects of the fast axis and the slow axis. After being modulated, the polarization direction and phase of the slow-axis light change, while the state of the fast-axis light remains unchanged, a phase difference appears between the two transmission modes and interference occurs in the transmission fiber (2), and the interference signal travels along the transmission fiber (2 ) is received by the spectrometer (8). It can be seen that the drift of the interference spectrum is determined by the phase difference introduced by the Pd/Ag hydrogen sensitive film (5) squeezing the PM-PCF (4), and the Pd/Ag hydrogen sensitive film (5) is very sensitive to hydrogen, so it can Realize high-precision sensing of ambient hydrogen concentration.

Phase difference between fast axis light and slow axis light Determined simultaneously by the extrusion of PM-PCF itself and the Pd/Ag hydrogen-sensitive film (5), it can be expressed as

(1)

In the formula, the integer m is the interference order, is the m-th order valley wavelength, , are the intrinsic birefringence and fiber length of PM-PCF, respectively; , are the additional birefringence introduced by the Pd/Ag hydrogen-sensitive film (5) and the length of the coating area, respectively.

Due to the expansion of the molecular lattice volume of Pd due to the absorption of _H2 , the extrusion of the air holes in the cladding causes the birefringence change of the slow axis, and the phase difference between the two transmission modes becomes

(2)

From (1) and (2), it can be obtained that the m-th order interference wave trough drift for

(3)

Additional birefringence change Determines the m-th order interference trough drift, and the Pd/Ag hydrogen sensitive film (5) is very sensitive to hydrogen, so it can realize high-precision sensing of hydrogen concentration.

The beneficial effects of the utility model are: (1) PM-PCF with excellent temperature characteristics is used to make an optical fiber hydrogen sensor that is not sensitive to temperature, and no temperature compensation link is required, which effectively simplifies the instrument structure and saves production costs; (2) Ag can effectively inhibit Pd binds H atom phase change, stabilize the metal lattice structure, alleviate the phenomenon of blistering and stacking faults on the surface of the Pd coating, improve the mechanical properties of the hydrogen-sensitive film, and prolong the service life of the device; therefore, the utility model has the advantages of simple structure, high sensitivity, and can reduce the impact of temperature fluctuations. The advantages of the influence brought by the detection of hydrogen concentration provide a practical solution for online monitoring of hydrogen concentration.

Description of drawings

Figure 1 is a system schematic diagram of a polarization-maintaining photonic crystal fiber hydrogen sensor based on polarization interference.

Fig. 2 is a schematic cross-sectional view of a hydrogen sensitive head in a polarization-maintaining photonic crystal fiber hydrogen sensor based on polarization interference.

detailed description

The utility model is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to accompanying drawing 1, a polarization-maintaining photonic crystal fiber hydrogen sensor based on polarization interference is characterized in that it consists of broadband light source (1), transmission fiber (2), polarization controller (3), PM-PCF (4) , Pd/Ag hydrogen sensitive film (5), two-dimensional optical fiber fixture (6), constant temperature gas chamber (7), spectrometer (8); the broadband light source (1) is connected to the polarization controller (3) through the transmission optical fiber (2) ), the polarization controller (3) is connected to the left end of the PM-PCF (4) through the transmission fiber (2), and the right end of the PM-PCF (4) is connected to the spectrometer (8) through the transmission fiber (2); the two-dimensional fiber holder (6 ) Fix the PM-PCF (4) at the bottom of the constant temperature gas chamber (7); see the attached figure 2 for the cross-section of the hydrogen sensitive head, uniformly sputter Pd/Ag hydrogen sensitive film (5) on the outside of the slow axis of the PM-PCF (4) Covering half of the outer circumference, the length of PM-PCF (4) is 40mm, the length of the coating area is 30mm, the film thickness of Pd/Ag hydrogen sensitive film (5) is 40nm, the mass fraction of Ag is 25%, PM - PCF (4) is a PM-1550-01 type polarization maintaining photonic crystal fiber.

The transmission fiber (2) is made of single-mode fiber, and the transmission fiber (2) and the PM-PCF (4) are spliced using the standard procedure of a fiber fusion splicer. The model of the fiber fusion splicer used is Fujikura 60s. The two-dimensional optical fiber clamp (6) keeps the PM-PCF (4) horizontally stretched, so as to prevent the Pd/Ag hydrogen-sensitive film (5) from falling off due to fiber bending and keep the inherent birefringence of the PM-PCF (4) constant. Air temperature remains on 25 degrees Celsius in the constant temperature air chamber (7).

The working principle of the utility model is: the broadband light source (1) emits a light beam with a wavelength of 1500nm~1600nm, adjusts the polarization state through the polarization controller (3), and then enters the PM-PCF along the transmission fiber (2). Since the Pd/Ag hydrogen-sensitive film (5) is evenly sputtered on the outside of the slow axis of PM-PCF (4) and covers half of the outer circumference, the coating distribution on the cladding surface is asymmetrical along the axial direction, and the Pd/Ag hydrogen-sensitive film (5) After absorbing hydrogen and causing volume expansion, the air holes in the extruded cladding can have different effects on the birefringence effects of the fast axis and the slow axis. After being modulated, the polarization direction and phase of the slow-axis light change, while the state of the fast-axis light remains unchanged, a phase difference appears between the two transmission modes and interference occurs in the transmission fiber (2), and the interference signal travels along the transmission fiber (2 ) is received by the spectrometer (8). It can be seen that the drift of the interference spectrum is determined by the phase difference introduced by the Pd/Ag hydrogen sensitive film (5) squeezing the PM-PCF (4), and the Pd/Ag hydrogen sensitive film (5) is very sensitive to hydrogen, so it can Realize high-precision sensing of ambient hydrogen concentration.

Claims (3)

1. a polarization-maintaining photonic crystal fiber hydrogen gas sensor based on polarized light interference, it is characterised in that: by wideband light source (1), Transmission Fibers (2), Polarization Controller (3), PM-PCF(4), Pd/Ag hydrogen sensitive film (5), two dimensional optical fiber fixture (6), constant temperature Air chamber (7), spectrometer (8) forms；Wideband light source (1) is connected to Polarization Controller (3), Polarization Control by Transmission Fibers (2) Device (3) passes through Transmission Fibers (2) and PM-PCF(4) left end is connected, PM-PCF(4) right-hand member passes through Transmission Fibers (2) and spectrometer (8) it is connected；Wherein, PM-PCF(4) slow axis outside uniform sputter Pd/Ag hydrogen sensitive film (5) cover this PM-PCF(4) periphery 1/2nd constitute hydrogen sensitive head, and two dimensional optical fiber fixture (6) is by PM-PCF(4) it is fixed on constant temperature air chamber (7) bottom.

A kind of polarization-maintaining photonic crystal fiber hydrogen gas sensor based on polarized light interference the most according to claim 1, it is special Levy and be: described PM-PCF(4) a length of 30mm ~ 50mm, Pd/Ag hydrogen sensitive film (5) a length of 20mm of plated film ~ 30mm, thickness be 40nm ~ 50nm, Ag mass fraction be 20% ~ 40%.

A kind of polarization-maintaining photonic crystal fiber hydrogen gas sensor based on polarized light interference the most according to claim 1, it is special Levy and be: described PM-PCF(4) the preferred model of polarization-maintaining photonic crystal fiber selected is PM-1550-01, operation wavelength exists 1550nm。