CN201697728U - A highly sensitive temperature sensor based on partially perfused HiBi-PCF-FLM - Google Patents

Abstract

The utility model relates to a high-sensitivity temperature sensor based on a partial perfusion HiBi-PCF-FLM, which solves the shortcoming of low temperature sensitivity of common optical fiber temperature sensors with an extremely compact structure. In the utility model, a temperature-sensitive solution is poured into the small air holes in the cladding layer of the photonic crystal fiber to form a photonic crystal fiber with high birefringence. Both ends of the photonic crystal fiber are respectively connected with two ports on one side of the fiber coupler to form a fiber loop mirror structure, and the two ports on the other side of the fiber coupler are respectively connected with a broadband light source and a wavelength measuring device. The fiber coupler divides the light emitted by the broadband light source into two beams of light that transmit in opposite directions. The phase difference of the two beams of light is very sensitive to temperature changes. For the larger drift of the output spectrum of the fiber optic loop mirror, the temperature information can be demodulated by monitoring the drift of a certain loss peak in the output spectrum. The sensor of the utility model has the advantages of small volume, simple structure and high temperature measurement sensitivity, and can be widely used in the field of high-sensitivity temperature monitoring.

Description

A highly sensitive temperature sensor based on partially perfused HiBi-PCF-FLM

technical field

The utility model belongs to the technical field of optical fiber sensing, in particular to a highly sensitive temperature sensor based on a partially perfused high birefringent photonic crystal fiber loop mirror (Highly Birefringent Photonic Crystal Fiber Loop Mirror, HiBi-PCF-FLM).

Background technique

Measuring temperature can be seen everywhere in our daily life, and thermometer is one of the most common simple temperature sensors. With the development of society and the advancement of science and technology, other temperature sensors based on electrical signals, such as thermocouples and thermistors, have gradually entered people's sight and are widely used in various fields of temperature detection. Their temperature measurement principle and structure are relatively simple, but because they use electrical signals as the working medium, they are easily subject to electromagnetic interference, and there are disadvantages such as easy corrosion, low sensitivity, and difficulty in realizing distributed sensing.

Fiber optic sensors have many unique advantages, such as insensitivity to electromagnetic interference, high sensitivity, small size, corrosion resistance, and can be applied in various environments. There are various mechanisms for using optical fiber as a temperature measurement medium, and a temperature sensor based on a fiber Bragg grating or a long-period fiber grating can be obtained by demodulating the wavelength drift or intensity change caused by temperature changes. The temperature information is valued by people. However, the sensitivity of the fiber Bragg grating temperature sensor is relatively low (only ~10pm/℃), so it cannot be applied to the field of high-sensitivity temperature measurement; the long-period fiber Bragg grating temperature sensor is extremely sensitive to bending due to its extreme sensitivity to bending. Unforeseen interference is introduced, so the measurement conditions are very demanding.

Photonic crystal fiber is a new type of optical fiber, in which wavelength-scale air holes are periodically arranged in the cladding along the axial direction, and has a two-dimensional photonic crystal structure. Different functions can be realized by flexible design of the size, distribution or refractive index of these air holes. The utility model realizes temperature sensing by pouring a temperature-sensitive solution into some air holes in the cladding of the photonic crystal fiber.

Contents of the invention

The purpose of the utility model is to propose a simple, compact, and high-sensitivity high-sensitivity temperature sensor based on the combination of a partially perfused high-birefringence photonic crystal fiber and an optical fiber ring mirror in view of the low sensitivity of the existing optical fiber temperature sensor. sensor.

The technical scheme that the utility model takes for solving the technical problem is:

A highly sensitive temperature sensor based on partially perfused HiBi-PCF-FLM, including photonic crystal fiber, fiber coupler and temperature-sensitive solution.

A temperature-sensitive solution is poured into the air hole in the cladding of a 5cm-long photonic crystal fiber to form a high birefringence effect. For the specific filling method, please refer to the literature: Y.Y.Huang, Y.Xu, Amnon Yariv, "Fabrication of functional microstructured optical fibers through a selective-filling technique,” Applied Physics Letters, Vol.85, No.22, 2004. The two ports on one side of the fiber coupler are respectively connected to the two ends of the photonic crystal fiber perfused with the temperature-sensitive solution, and the two ports on the other side are respectively connected to the broadband light source and the wavelength measurement device. Photonic crystal fiber and fiber coupler form a fiber loop mirror structure.

The utility model has the advantages that: the phase difference of the two oppositely transmitted lights in the fiber optic loop mirror is very sensitive to temperature changes, and under the interference of the output end of the fiber optic loop mirror, a very small change in the external environment temperature can cause the optical fiber The larger drift of the output spectrum of the ring mirror, by monitoring the drift of a certain loss peak in the interference spectrum, the temperature information can be demodulated, thereby greatly improving the sensitivity of temperature sensing, which can reach 1.8nm/°C, compared to The fiber Bragg grating temperature sensor is two orders of magnitude higher; the length of the photonic crystal fiber used for the sensing part is only 5cm, which is greatly reduced compared with the temperature sensor of other fiber loop mirror structures, so the device is compact in structure and small in size, and can be widely used It is used in various temperature monitoring fields.

Description of drawings

Fig. 1 is a structural diagram of the utility model, and Fig. 2 is a schematic diagram of the end face of the photonic crystal fiber and its cladding small air holes infused with temperature-sensitive type in the utility model.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described.

As shown in Figure 1, a highly sensitive temperature sensor based on partially perfused HiBi-PCF-FLM includes a photonic crystal fiber 1, a fiber coupler 2 and a temperature-sensitive solution 3. Get 5cm long photonic crystal fiber 1, pour temperature sensitive solution 3 in the small air hole of this photonic crystal fiber cladding, form high birefringence photonic crystal fiber; The two ports on the other side of the fiber coupler are respectively connected to the broadband light source and the wavelength measurement device. The photonic crystal fiber 1 and the fiber coupler 2 form a fiber loop mirror structure. When the light of the broadband light source passes through the fiber optic loop mirror, interference can occur at its output port, forming multiple loss peaks, and the polarization extinction ratio of the loss peaks can reach 20-30dB.

The working mode of the utility model is as follows: the fiber coupler divides the light emitted by the broadband light source into two bundles of oppositely transmitted light to enter the fiber optic loop mirror, and after propagating in the fiber optic loop mirror for a week, it is emitted from the output port of the fiber optic loop mirror through the fiber optic coupler. Since the photonic crystal fiber can achieve a high birefringence effect after being infused with a temperature-sensitive type, the two beams of light propagating in opposite directions will produce a phase difference, and its value is:

Among them: Δn is the refractive index difference between two oppositely transmitted lights in the fiber optic loop mirror, L is the length of the photonic crystal fiber, and λ is the wavelength of the incident light wave. In the present utility model, Δn can reach 5.7×10 ^-4 , L is 5 cm, and λ is 1550 μm.

The two beams of light with phase difference will interfere after meeting at the output end of the fiber optic loop mirror, forming an interference spectrum with multiple loss peaks. The relationship between the interference spectrum and the phase difference is as follows:

When the external temperature changes, the refractive index of the solution in the small hole of the photonic crystal fiber will change slightly, and then the difference in the refractive index of the two oppositely transmitted lights in the fiber optic ring mirror will change, that is, the phase difference between the two will change. According to the above formula, it can be seen that the interference spectrum will drift, and the temperature information can be demodulated by monitoring the drift of a certain loss peak as the temperature changes.

The key technology of the utility model that can realize high-sensitivity temperature measurement is: the photonic crystal fiber used can achieve a higher birefringence effect after being infused with a temperature-sensitive type; The change is relatively sensitive. After the interference of the output spectrum of the fiber optic loop mirror, it can bring about a large drift of the loss peak, thereby improving the sensitivity of temperature measurement.

In this embodiment, the diameter of the two large air holes in the cladding of the selected photonic crystal fiber is 4.5 μm, the diameter of the remaining small air holes is 2.2 μm, and the fiber length is 5 cm. The temperature-sensitive liquid is deionized water, the refractive index at room temperature is 1.333, and the rate of change of refractive index with temperature is 6.24×10 ^-4 /℃; the temperature sensitivity of the sensor reaches 1.8nm/℃.

Claims (4)

1. high sensitivity temperature sensor based on part perfusion type HiBi-PCF-FLM, comprise photonic crystal fiber (1), fiber coupler (2) and refraction index solution (3), it is characterized in that: the fiber coupler of this contrive equipment two ports on one side with pour into refraction index solution after the photonic crystal fiber two ends be connected, two ports of another side are connected with the wavelength measurement device with wideband light source respectively, and photonic crystal fiber and fiber coupler are formed the fiber loop mirror structure.

2. as right 1 described photonic crystal fiber, the diameter that it is characterized in that two big airports in the covering is 4.5 μ m, and the diameter of all the other little airports is 2.2 μ m, can reach higher birefringence effect after the perfusion refraction index solution in the little airport of covering.

3. as right 1 described fiber coupler, it is characterized in that its splitting ratio is 1: 1.

4. as right 1 described refraction index solution, it is characterized in that its refractive index is responsive to temperature, can be aqueous solution or liquid crystal.

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