A kind of fibre optic temperature sensor
Technical field
The invention belongs to technical field of optical fiber sensing, be specifically related to a kind of novel fibre optic temperature sensor.
Background technology
Fibre optic temperature sensor has very wide range of application.Its adopts optical fiber to make light path, and probe is separated with instrument, has increased adaptive capacity to environment, and it can be in strong electromagnetic, high voltage and can not use lead-in wire to carry out measuring under the condition such as electrical transmission.At present, the sensor of having succeeded in developing mainly contains fluorescent optical sensor, birefringece crystal sensor and semiconductor transducer.Existing fibre optic temperature sensor is mostly based on spectrophotometry, like list of references [1] Fiber Bragg Grating Temperature Sensor with Controllable Sensitivity; Jaehoon Jung, Hui Nam, Byoungho Lee, Jae Oh Byun, and Nam Seong Kim; Applied Optics, Vol.38, Issue13, the fiber grating of mentioning among the pp.2752-2754.List of references [2] Fabry-Perot Fiber-Optic Temperature Sensor; Lewis Research Center, Cleveland, Ohio NASA, Tech Briefs; Friday, the optical fiber Fabry one Perot etalon tool of mentioning among the January 01 1999.List of references [3] is based on the fibre optic temperature sensor of spectral detection; Optical fiber temperature sensor applying spectral analysis detection; " sensor technology " calendar year 2001 the 20th is rolled up the semiconductor absorption sensor of mentioning in the o. 11th, and they all require spectral analysis, complex manufacturing technology, expensive.
Summary of the invention
The present invention is complicated in order to solve existing temp sensor device, problem with high costs, a kind of novel optical fiber temperature sensor that provides.This sensor device is simple, and measuring accuracy is high, make easily, cost is low,, and adapt to temperature detection at high voltage and highfield environment.
The principle of described fibre optic temperature sensor is based on the temperature variant characteristic of double refractive inde of polarization maintaining optical fibre.The key element of sensor, temperature-sensing element is one section polarization maintaining optical fibre.It is poor that sensor is accurately measured the birefringent phase of this section polarization maintaining optical fibre, thereby obtain the information of temperature.
A kind of fibre optic temperature sensor provided by the invention comprises optical transceiver module, Transmission Fibers and sensing head; When described Transmission Fibers is polarization maintaining optical fibre; Described sensing head comprises temperature-sensing element and fiber reflector; Temperature-sensing element is one section polarization maintaining optical fibre, and first end of this section polarization maintaining optical fibre is provided with fiber reflector, is 45 degree between the polarization axle of second end and Transmission Fibers and fuses and be connected.Described optical transceiver module light source, optical fiber loop device, polarization beam apparatus and two photoelectric detectors; Described optical fiber loop device and polarization beam apparatus are three port devices; Wherein, Two ports of the front end of optical fiber loop device connect the light source and first photoelectric detector respectively through single-mode fiber; The 3rd port of rear end is through first port of single-mode fiber connection polarization beam apparatus front end, and second port of polarization beam apparatus front end connects second photoelectric detector through single-mode fiber, and the 3rd port of rear end connects Transmission Fibers.Like this, two linear polarization light intensities that return in the Transmission Fibers are exactly the result that two linearly polarized lights in the temperature-sensing element are interfered.The output of two photoelectric detectors just provides the birefringent phase difference information of temperature-sensing element, just the information of the temperature that will survey.The method of the length of this section of temperature range available adjustment polarization maintaining optical fibre of measuring changes, thereby adapts to different application.
When described Transmission Fibers is single-mode fiber; A polarizer is installed on sensing head; The polarizer one end is connected with Transmission Fibers; Be connected through polarization maintaining optical fibre between the other end and the temperature-sensing element, be 45 degree between the polarization axle of this section polarization maintaining optical fibre and polarization maintaining optical fibre that temperature-sensing element adopts and fuse and be connected.Described optical transceiver module mainly is made up of fiber coupler and two photoelectric detectors; Described fiber coupler is four ports; Wherein first port is used for directly receiving the light of light emitted, and second port connects Transmission Fibers, and all the other two ports connect two photoelectric detectors.
The invention has the advantages that:
1. the principle of fibre optic temperature sensor of the present invention and simple in structure is easy to make.
2. the sensitivity of fibre optic temperature sensor of the present invention is adjustable, only needs the length of the polarization maintaining optical fibre of change temperature-sensing element
Spend, just can satisfy the application demand of various temperature range.
3. the relative accuracy of temperature detection can reach 0.5%.
Description of drawings
Fig. 1 is the fibre optic temperature sensor principle schematic;
Fig. 2 is the typical sensor temperature response curve;
The optical fiber temperature transducer system principle schematic of Fig. 3 for simplifying.
Embodiment
Below in conjunction with accompanying drawing fibre optic temperature sensor provided by the invention is elaborated.The present invention provides two embodiment to explain that the employing polarization maintaining optical fibre is as the formed temperature sensor of temperature-sensing element.
Embodiment 1:
Described fibre optic temperature sensor comprises optical transceiver module 1, Transmission Fibers 2 and is used to experience the sensing head 3 of measured point temperature a long way off; As shown in Figure 1; Described optical transceiver module 1 is used for light is transferred to sensing head 3 through Transmission Fibers 2; Sensing head 3 will comprise the intensity signal of temperature information through Transmission Fibers 2 back light transceiver modules 1, and then obtain the temperature information of measured point.Described Transmission Fibers 2 is polarization maintaining optical fibres.Described sensing head 3 comprises temperature-sensing element 301 and fiber reflector 302, and temperature-sensing element 301 is one section polarization maintaining optical fibre, and an end of temperature-sensing element 301 is provided with fiber reflector 302, and the other end connects Transmission Fibers 2.Described optical transceiver module 1 comprises light source 101, optical fiber loop device 102, polarization beam apparatus 103 and two photoelectric detector 104A, 104B; Described optical fiber loop device 102 is three port devices with polarization beam apparatus 103; Wherein, The first port A of the front end of optical fiber loop device 102 is connected the light source 101 and the first photoelectric detector 104A with the second port B through single-mode fiber; The 3rd port C is through the first port A of single-mode fiber connection polarization beam apparatus 103 front ends, and the second port B of polarization beam apparatus 103 front ends connects the second photoelectric detector 104B through single-mode fiber, and the 3rd port C connects Transmission Fibers 2--polarization maintaining optical fibre.
The length of the polarization maintaining optical fibre that described temperature-sensing element 301 is used is by the temperature range decision of being surveyed.The general temperature range of detection that requires is big more, needs to select short polarization maintaining optical fibre as temperature-sensing element 301; The scope that require to detect hour then selects long polarization maintaining optical fibre as temperature-sensing element 301.
Fuse between the polarization maintaining optical fibre that polarization maintaining optical fibre that above-mentioned Transmission Fibers 2 is adopted and temperature-sensing element 301 are adopted, fuse a polarization axle of locating two sections polarization maintaining optical fibres mutually in angle of 45 degrees.
The trend of the light in the fibre optic temperature sensor of the present invention is: referring to Fig. 1, the light that light source 101 sends gets into polarization beam apparatus 103 through optical fiber loop device 102 backs.The light of polarization beam apparatus 103 outputs is single linearly polarized light, and propagates along a polarization axle of Transmission Fibers 2.When getting into temperature-sensing element 301, this linearly polarized light is broken down into two linearly polarized lights in+/-45 degree directions.They are propagated along two polarization axles of temperature-sensing element 301 respectively, are reflected along the original optical path backspace by fiber reflector 302 then.When getting into Transmission Fibers 2 again, two linearly polarized lights in the temperature-sensing element 301 are got back on two polarization axles of Transmission Fibers 2 by+/-45 ° of projections respectively.The two linearly polarized light components that temperature-sensing element 301 is all arranged on each polarization axle of Transmission Fibers 2, their phase differential be respectively 2 δ with 2 δ+180 °.Wherein δ is that the one way birefringent phase of temperature-sensing element 301 is poor.Like this, the light intensity on each polarization axle is exactly the result of interference of two linearly polarized lights in the temperature-sensing element in Transmission Fibers 2.In backhaul, two linearly polarized lights in the Transmission Fibers 2 are directed to photoelectric detector 104A and 104B by polarization beam apparatus 103 and optical fiber loop device 102 respectively, and two photoelectric detector 104A and 104B detect the intensity signal of two linearly polarized lights respectively.Because the birefringent phase difference of temperature-sensing element 301 is functions of temperature, so temperature can be through the reading D of two photoelectric detectors
1And D
2, confirm with following formula:
Fig. 2 is the curve of a typical function F (T), according to two reading D
1And D
2, calculate functional value F, just can get temperature value T from the function curve F (T) of prior calibration.
Embodiment 2:
Based on the principle same, the embodiment of available another simplification with embodiment 1.
In embodiment 1, the photoelectric detector 104A of two passages and the reading of 104B have all comprised the information of temperature, thereby can be reduced to and only use single passage.Like this, available single-mode fiber replaces twin-channel polarization maintaining optical fibre as Transmission Fibers 2.Simultaneously, the polarizer 303 of available two-port replaces the polarization beam apparatus 103 of three ports.For the variation that makes luminous power does not influence the work of system, we still use two photoelectric detectors, and replace optical fiber loop devices 102 with the fiber coupler 105 of four ports.As shown in Figure 3; The fibre optic temperature sensor that provides in the present embodiment 2 comprises optical transceiver module 1, Transmission Fibers 2 and sensing head 3; Described Transmission Fibers 2 is a single-mode fiber, and the two ends of Transmission Fibers 2 connect the polarizer 303 in fiber coupler 105 and the sensing head 3 in the optical transceiver module 1 respectively; Described sensing head 3 is made up of temperature-sensing element 301, fiber reflector 302 and the polarizer 303; Described temperature-sensing element 301 is one section polarization maintaining optical fibre; Wherein temperature-sensing element 301 is provided with fiber reflector 302 foremost; The rear end of temperature-sensing element 301 is connected with the polarizer 303 through polarization maintaining optical fibre, and said temperature-sensing element 301 be connected with this section polarization maintaining optical fibre fuse a place, the polarization axle of two sections polarization maintaining optical fibres is mutually 45 and spends.
Described optical transceiver module 1 comprises light source 101, fiber coupler 105 and two photoelectric detector 106A and 106B; Between fiber coupler 105 and the light source 101, be connected through monofilm optical fiber between fiber coupler 105 and the polarizer 303; Described fiber coupler 105 is four port devices; Wherein first port A is used to receive the light of light emitted, and second port B connects Transmission Fibers, and all the other two port C are connected photoelectric detector 106A and 106B with D.One of them photoelectric detector 106A is used to detect the polarization state light intensity D that single-mode fiber returns
3, another photoelectric detector 106B is used for 101 of detection light source and sends light intensity D
4, prison shows the variation of luminous power, then according to formula:
Calculate F (T), just can get temperature value T from the function curve F (T) of prior calibration.D in the formula
3And D
4The reading of two photoelectric detectors of difference.
Because replaced transmission polarization maintaining optical fibre, polarization beam apparatus and optical fiber loop device respectively with single-mode fiber, the polarizer and fiber coupler among the embodiment 2, the cost of gained fibre optic temperature sensor reduces greatly.To the available this embodiment of the lower application of accuracy requirement.