CN211978166U - Active temperature sensitive device based on Mach-Zehnder structure - Google Patents

Abstract

The utility model belongs to the technical field of this optical fiber sensing, the utility model discloses an active type temperature sensing device based on mach-zehnder structure, include: the annular cavity is formed by sequentially connecting a wavelength division multiplexer, an erbium-doped optical fiber, an optical fiber isolator, a Mach-Zehnder temperature sensitive element structure and a coupler end to end; the light source is connected with the wavelength division multiplexer through a single mode fiber, and the coupler is connected with the spectrometer through a single mode fiber. The utility model discloses a temperature sensitive device has with low costs and reliable and stable advantage.

Description

Active temperature sensitive device based on Mach-Zehnder structure

technical field

The utility model relates to the technical field of optical fiber sensing, in particular to an active temperature sensitive device based on a Mach-Zehnder structure.

Background technique

The description of the background technology of the present utility model belongs to the related technology related to the present utility model, and is only used to illustrate and facilitate the understanding of the utility model content of the present utility model. The new type of prior art on the filing date of the first application.

In the optical fiber active temperature sensing system, the output wavelength, intensity, etc. will change with the changes of physical quantities such as external refractive index, temperature, strain, magnetic field, curvature, etc., so as to realize the detection of external physical quantities.

However, the current sensing systems generally have the disadvantages of high cost, poor adaptability and susceptibility to electromagnetic interference.

Utility model content

The purpose of the embodiments of the present invention is to provide an active temperature sensitive device based on the Mach-Zehnder structure. The Mach-Zehnder structure active temperature sensitive device of the utility model is based on the Mach-Zehnder interference principle, and utilizes its sensitivity to ambient temperature to achieve temperature measurement within a fixed range, and the material selected in the sensing area is traditional single-mode optical fiber and multimode fiber, the sensor device has the advantages of low cost, simple tuning, and convenient use.

The purpose of this utility model is achieved through the following technical solutions:

In a first aspect, the present utility model provides an active temperature sensitive device based on a Mach-Zehnder structure, comprising:

A light source, a ring cavity and a spectrometer, the ring cavity is formed by a wavelength division multiplexer, an erbium-doped fiber, a fiber isolator, a Mach-Zehnder temperature sensitive element structure and a coupler connected end to end in sequence; the light source is connected by a single mode The optical fiber is connected with the wavelength division multiplexer, and the coupler is connected with the spectrometer through a single-mode fiber.

Further, the Mach-Zehnder temperature sensitive element structure includes two multi-mode fibers, and a second single-mode fiber is connected between the two multi-mode fibers.

Further, the length of the second single-mode optical fiber is 5 cm or 6 cm, and the length of the multi-mode optical fiber is 0.5 cm.

Further, the light source is a 980nm LD pump light source, the wavelength division multiplexer is a 980nm/1550nm wavelength division multiplexer, the length of the erbium-doped fiber is 10.4m, and the splitting ratio of the coupler is 40:60.

In the second aspect, the present invention provides a preparation method of an active temperature sensitive device based on a Mach-Zehnder structure, wherein the temperature sensitive device is the above temperature sensitive device, comprising the following steps:

A single-mode fiber is used to connect the wavelength division multiplexer, erbium-doped fiber, fiber isolator, Mach-Zehnder temperature sensitive element structure and coupler in turn to form a ring cavity, and connect the light source and the wavelength division multiplexer through the single-mode The optical fiber connection connects the light source to the annular cavity; the coupler is connected to the spectrometer through a single-mode optical fiber, and the spectrometer is connected to the annular cavity to obtain the temperature sensitive device.

Further, the preparation of the Mach-Zehnder temperature sensitive element structure includes the following steps:

Wipe the end faces of the second single-mode optical fiber and the multi-mode optical fiber with alcohol cotton respectively, then cut them flat, and perform optical fiber fusion in the order of multi-mode-single-mode-multi-mode to obtain a multi-mode-single-mode-multi-mode temperature-sensitive structure. It is the structure of the Mach-Zehnder temperature sensitive element.

The embodiments of the present utility model have the following beneficial effects:

The sensor device of the utility model uses an all-fiber structure for sensing, and has the advantages of anti-electromagnetic interference, electrical insulation, high sensitivity, small size, light weight, flexible shape and structure, strong adaptability, wide application range and high reliability.

Compared with the traditional Mach-Zehnder structure, the utility model adopts the on-line Mach-Zehnder structure, and has the advantages of compact structure, lower production cost, many tuning modes and the like.

The temperature sensitive element of the online multimode-single-mode-multimode Mach-Zehnder structure in the optical fiber active sensing structure adopted by the utility model is very sensitive to temperature.

The sensor device of the utility model has good stability.

Description of drawings

1 is a schematic diagram of the application sensing structure of the device of the present invention

1. LD pump light source; 2. Wavelength division multiplexer; 3. Erbium-doped fiber; 4. Fiber isolator; 5. Multimode-single-mode-multimode Mach-Zehnder (MZI) temperature sensitive element structure (5- 1 single mode fiber; 5-2 multimode fiber); 6, 1×2 coupler; 7, spectrometer; 8, single mode fiber.

Figure 2 is a linear fitting diagram of temperature-output wavelength when the single-mode length is 5 cm.

Detailed ways

The present application will be further introduced below with reference to the embodiments.

In order to describe the embodiments of the present invention or the technical solutions in the prior art more clearly, in the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. Different embodiments can be replaced or combined, and for those skilled in the art, other implementations can also be obtained according to these embodiments without creative efforts.

As shown in Figure 1, an active temperature sensitive device based on Mach-Zehnder structure includes:

Light source 1, annular cavity and spectrometer 7, the annular cavity is formed by connecting wavelength division multiplexer 2, erbium-doped fiber 3, fiber isolator 4, Mach-Zehnder temperature sensitive element structure 5 and coupler 6 in turn; The light source 1 is connected to the wavelength division multiplexer 2 through a single-mode fiber 8 , and the coupler 6 is connected to the spectrometer 7 through the single-mode fiber 8 .

Further, the Mach-Zehnder temperature sensitive element structure 5 includes two multi-mode optical fibers 5-2, and a second single-mode optical fiber 5-1 is connected between the two multi-mode optical fibers.

Further, the length of the second single-mode optical fiber 5-1 is 5 cm or 6 cm, and the length of the multi-mode optical fiber 5-2 is 0.5 cm.

Further, the light source 1 is a 980nm LD pump light source, the wavelength division multiplexer 2 is a 980nm/1550nm wavelength division multiplexer, the length of the erbium-doped fiber 3 is 10.4m, and the splitting ratio of the coupler 5 is 40:60.

A preparation method of an active temperature-sensitive device based on a Mach-Zehnder structure, wherein the temperature-sensitive device is the above-mentioned temperature-sensitive device, comprising the following steps:

The single-mode fiber 8 is used to connect the wavelength division multiplexer 2, the erbium-doped fiber 3, the fiber isolator 4, the Mach-Zehnder temperature sensitive element structure 5 and the coupler 6 in turn to form a ring cavity. The demultiplexer 2 connects the light source 1 to the ring cavity through the single-mode fiber 8; the coupler 6 is connected to the spectrometer 7 through the single-mode fiber 8, and the spectrometer 7 is connected to the ring The cavity yields the temperature sensitive device.

Further, the preparation of the Mach-Zehnder temperature sensitive element structure 6 includes the following steps:

Wipe the end faces of the second single-mode optical fiber 5-1 and the multi-mode optical fiber 5-2 respectively with alcohol cotton, cut them flat, and perform optical fiber fusion in the order of multi-mode-single-mode-multi-mode to obtain multi-mode-single-mode- The multimode temperature sensitive structure is the Mach-Zehnder temperature sensitive element structure.

An active temperature sensor device based on Mach-Zehnder structure is shown in Figure 1. The LD pump light source is coupled into the ring cavity through a single-mode fiber wavelength division multiplexer (WDM), and the erbium-doped fiber (EDF) 3 After being connected with an optical fiber isolator (ISO) 4, a multi-mode-single-mode-multi-mode Mach-Zehnder (MZI) structure 5 can be used as a filter to achieve temperature tuning. The beam is split by the 1×2 fiber coupler 6 and then output to the spectrometer 7 in one way, and the other way returns to the ring cavity for further transmission.

In the above-mentioned Mach-Zehnder structure active temperature sensing device, 980nm LD pump light, 980nm/1550nm wavelength division multiplexer (WDM), 10.4m long erbium-doped fiber (EDF), and the coupling ratio of 40:60 are selected. device. In the multimode-single-mode-multimode Mach-Zehnder (MZI) temperature sensitive element (5), the length of the second single-mode optical fiber 5-1 is 5 cm or 6 cm, and the length of the multi-mode optical fiber 5-2 is 0.5 cm.

The multi-mode-single-mode-multi-mode structure is selected as the Mach-Zehnder temperature sensitive element, and the incident light is transmitted to the multi-mode fiber 5-2 structure through the single-mode fiber 8. When the incident light is transmitted to the second single-mode fiber 5 in the middle part When -1 is spliced at the end face, part of the light will be transmitted along the core of the second single-mode optical fiber 5-1, and another part of the light will enter the cladding of the second single-mode optical fiber 5-1 and continue to transmit. When the two parts of light are simultaneously transmitted to the spliced end face of the other end of the second single-mode fiber 5-1 and the multi-mode fiber 5-2, the two parts of light will be re-coupled into the multi-mode fiber 5-2, and the phase matching conditions are met. , the light between the core and the cladding will undergo inter-mode interference, resulting in an output interference spectrum.

Among them, a phase difference is generated between the light passing through the core and cladding of the multimode fiber, respectively

n _core represents the effective refractive index of the multimode fiber core, n _cla d represents the effective refractive index of the multimode fiber cladding, L represents the length of the multimode fiber, and λ represents the wavelength of the transmitted light.

Due to thermo-optic effects, changes in temperature will result in changes in the refractive index of the core, cladding and the length of the interference arms.

The thermal expansion coefficient of the fiber is:

α=dL/LdT (3)

At the same time, the refractive index of the core and the cladding will also change. Let the thermo-optic coefficients of the core and the cladding be ζ _core and ζ _clad respectively, we can get:

When the temperature changes, the interferometric arm length L and the inter-mode phase difference will change, resulting in a shift in the output interference wavelength.

Figure 1 shows an active temperature sensing device based on a Mach-Zehnder structure. Among them, 980nm LD pump light, 980nm/1550nm wavelength division multiplexer (WDM), 10.4m long erbium-doped fiber (EDF), and a coupler with a splitting ratio of 40:60 are selected. In the multimode-single-mode-multimode Mach-Zehnder (MZI) temperature sensitive element (5), the length of the second single-mode optical fiber 5-1 is 5 cm or 6 cm, and the length of the multi-mode optical fiber 5-2 is 0.5 cm.

The manufacturing method of the sensing structure in the device: Wipe the end faces of the second single-mode optical fiber 5-1 and the multi-mode optical fiber 5-2 with alcohol cotton respectively, then cut them flat with a fiber cutter, and use a fusion splicer to follow the multi-mode-single-mode - Multi-mode fiber splicing is performed in sequence, wherein the second single-mode fiber 5-1 is 5 cm, and the multi-mode fiber 5-2 is 0.5 cm, and the splicing loss is controlled during the splicing process. According to the same operation method, a 6cm single-mode fiber and a 0.5cm multi-mode fiber were made into a multimode-single-mode-multimode temperature-sensitive structure.

The active sensor device uses 980nm LD pump light, 980nm/1550nm wavelength division multiplexer (WDM), 10.4m long erbium-doped fiber (EDF), and a coupler with a split ratio of 40:60. The LD pump light 1 is coupled into the cavity through a single-mode fiber 8 connected to a wavelength division multiplexer (WDM) 2, and the pump light is amplified by an erbium-doped fiber (EDF) 3, followed by an optical fiber isolator (ISO) 4 to ensure the one-way transmission of light and prevent some of the returned light from affecting the optical path system. After that, the light in the optical path is filtered through a multimode-single-mode-multimode Mach-Zehnder (MZI) temperature sensitive element structure 5, and then a 1×2 coupler Coupler16 is connected to form a loop. A coupler with a splitting ratio of 40:60 is used. The light enters through port 1 of the coupler Coupler1 and is divided into two paths. One path is connected to the wavelength division multiplexer after the LD pump light, and the other path is connected to the spectrometer (OSA) 7. If the temperature of the environment is controlled by a temperature control box, the transmission spectra under different temperature environments can be obtained.

Multimode-single-mode-multimode Mach-Zehnder (MZI) temperature sensitive element is used for filtering to form an active sensing device, which controls the temperature of the temperature control box to increase. ℃ measure the output waveform once and fit the experimental results. Combined with data analysis. At 30°C to 35°C, the sensitivity of the temperature-sensitive device reaches 0.216 nm/°C, as shown in the fitting curve of y1 in Fig. 2 . At 40°C to 55°C, the sensitivity of the temperature-sensitive device reaches 0.2115 nm/°C, as shown by the y2 fitting curve in Fig. 2 . Among them, the sensitivity reaches 0.682nm/°C from 35°C to 40°C. It is 10 times more sensitive than the common multi-mode-single-mode-multi-mode interference sensing structure, and the active temperature sensitive device has good stability under the condition of keeping the external environment unchanged.

It should be noted that the above embodiments can be freely combined as required. The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. For those skilled in the art, the present utility model may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (4)

1. An active temperature-sensitive device based on a Mach-Zehnder structure, comprising:

the annular cavity is formed by sequentially connecting a wavelength division multiplexer, an erbium-doped optical fiber, an optical fiber isolator, a Mach-Zehnder temperature sensitive element structure and a coupler end to end; the light source is connected with the wavelength division multiplexer through a single mode fiber, and the coupler is connected with the spectrometer through a single mode fiber.

2. A mach-zehnder structure-based active temperature-sensitive device according to claim 1, characterized in that the mach-zehnder structure-based temperature-sensitive element comprises two multimode optical fibers, and a second single-mode optical fiber is connected between the two multimode optical fibers.

3. The active temperature-sensitive device according to claim 2, wherein the second single-mode fiber has a length of 5cm or 6cm, and the multimode fiber has a length of 0.5 cm.

4. The active temperature-sensitive device based on the Mach-Zehnder structure of claim 1, characterized in that the light source is a 980nm LD pump light source, the wavelength division multiplexer is a 980nm/1550nm wavelength division multiplexer, and the erbium-doped fiber has a length of 10.4 m; the coupler split ratio was 40: 60.

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