RU180903U1 - FIBER OPTICAL THERMOMETER - Google Patents

Abstract

The utility model relates to the field of temperature measurement in areas with strong electromagnetic interference, in areas of increased explosion and fire hazard, when measuring under high voltage. The device comprises an optical coupler, a circulator, an optical filter, N-1 optical splitters connected in series via fiber optics, N-1 optical sensors, N optical combiners connected in series via fiber optic cables, the laser radiation source is made broadband, and each optical sensor is made on the basis of fiber Bragg gratings with two π-phase shifts symmetrically located relative to its central wavelength. The technical result consists in simplifying the circuit of a fiber optic thermometer. 1 s.p. f-ly, 4 ill.

Description

The technical solution relates to the field of temperature measurement in areas with strong electromagnetic interference, in areas of increased explosion and fire hazard, during measurements under high voltage and in other conditions where the use of standard electronic means of monitoring the temperature state is inadmissible, namely, systems for monitoring the temperature state in medicine, at power supply facilities, engineering structures.

A fiber optic thermometer is known (RF patent RU 2491523 C1, “Fiber optic thermometer”, published August 27, 2013), including a fiber optic temperature sensor with a Bragg fiber array recorded near its end, as well as a recording system.

The disadvantage of this fiber optic thermometer is the need to use a complex expensive unit for the spectral analysis of the received radiation and a photodetector for recording spectral bias, as a rule, these are optical spectrum analyzers. Optoelectronic separate signal processing is also difficult. All this leads to the appearance of additional sources of temperature measurement errors and a decrease in their accuracy in general.

There is a fiber optic thermometer that includes a laser source, an optical sensor, and a receiving device (US Patent No. 7463832 B2, “Method and System for Compensating Thermal Displacements for Optical Networks,” published 09.08.2005).

The principle of operation of such a fiber-optic thermometer is that they generate pairs of signals of a predetermined close amplitude, transmit the generated pair of signals to the optical sensor, receive the pair of signals passed through it, and determine the temperature by comparing the difference in amplitudes between the signals of the pair received after passing through through an optical sensor, or by comparing their amplitudes with the amplitudes of the signals in the generated pair transmitted to the receiving device.

The disadvantage of this fiber-optic thermometer is the need to use a complex optical system for separate spectral reception of individual components of signal pairs, requiring, as a rule, the presence of narrow-band interference filters, in turn, having a temperature dependence of spectral characteristics. Separate optoelectronic processing of the components is also complex and represents the processing of the absolute amplitude values of the received signals, subject to the effects of noise and interference of various nature. All this leads to the appearance of additional sources of temperature measurement errors and a decrease in their accuracy in general.

Closest to the proposed technical solution is a fiber optic thermometer described in the method (RF patent RU 2491511 C2, "Method for measuring the parameters of physical fields", published August 27, 2013), containing a source of two-frequency laser radiation, an optical splitter, the first fiber optic cable , an optical sensor, a second optical fiber cable, a first photodetector, a second photodetector connected through a third optical fiber cable to a second output of the optical splitter, a phase meter, a controller about distribution of the parameter of the physical field, while the outputs of the first and second photodetectors are connected respectively to the first and second inputs of the phase meter, and the output of the phase meter to the input of the controller determining the parameter of the physical field. In various cases, the device can be performed using an optical sensor based on a Bragg fiber grating, or a Fabry-Perot interferometer, or a thin-film filter. Typically, the length of the third fiber optic cable is the sum of the lengths of the first and second fiber optic cables.

The prototype is based on measuring the phase difference between the envelope of the beats of the signals of the generated pair and the envelope of the beats of the signals of the pair passing through the optical sensor.

The disadvantage of the prototype is the presence of a complex and expensive source of dual-frequency laser radiation, in which it is necessary to use the Mach-Zehnder electro-optical modulators, in which the position of the operating point is shifted due to the influence of internal and external factors, such as ambient temperatures, so an additional device is required for its stabilization, which significantly complicates the scheme of the fiber optic thermometer. In addition, in this technical solution there is no possibility of connecting more than one temperature sensor, and there is no possibility of multiplexing.

The technical problem lies in the complexity of the used dual-frequency laser radiation source.

The technical problem to be solved (technical result) of the proposed fiber optic thermometer is to simplify the scheme of the fiber optic thermometer.

The technical problem to be solved (technical result) in a fiber-optic thermometer containing a laser radiation source, an optical splitter, an optical sensor, a first photodetector, a second photodetector, a temperature determination controller, a laser radiation source connected to the input of the optical splitter via a fiber optic fiber, a second output of the optical splitter connected to the input of the optical sensor by means of a fiber light guide is achieved by the fact that an optical response is additionally introduced into it a driver, a circulator, an optical filter, N-1 optical splitters connected in series through fiber optic fibers, N-1 optical sensors, N optical couplers connected in series through fiber optical fibers, where N is a natural number and N≥1, with the first output of each previous N the optical splitter is connected to the input of each subsequent corresponding from N optical splitter, the second output of each input from N-1 optical splitter is connected to the input of the corresponding from N-1 op of the optical sensor through a fiber, the output of each of the N optical sensors is connected to the second input of the corresponding N optical combiner via a fiber, the first input of each of the previous N optical combiners connected to the output of each subsequent corresponding N optical combiner, the output of the first from N optical the combiner is connected to the input of the optical coupler through a fiber light guide, the first output of the optical coupler is connected to the input of the first of the first photodetector by means of a fiber, the second output of the optical coupler is connected to the input of the circulator by means of a fiber, the first output of the circulator is connected to the optical filter by the fiber, the second output of the circulator is connected to the input of the second photodetector by the fiber, the outputs of the first and second photodetector are connected to the first and the second inputs of the temperature determination controller, respectively, by means of electric wires, the source of laser radiation eniya made broadband, and each optical sensor is based on fiber Bragg grating with two phase shifts of π-symmetrically arranged with respect to its center wavelength and spaced by an amount Δλ.

In particular, in optical sensors, the phase shift separation is Δλ _i ≠ Δλ _j , where i and j are the numbers of optical sensors, i, j∈N, where N is the set of optical sensors, and the difference Δλ _i -Δλ _{j is} not equal to and is not a multiple of in general and particular Δλ _i and Δλ _j .

In FIG. 1 is a structural diagram of a fiber optic thermometer; FIG. 2 shows the construction of an optical sensor; FIG. 3 is a spectrum of a Bragg fiber lattice with two π-phase shifts, FIG. 4 shows the operation algorithm of the temperature determination controller.

The fiber-optic thermometer (Fig. 1, Fig. 2) contains a laser source 1, N connected in series via fiber optic optical splitters 2 ₁ -2 _N , N optical sensors 3 ₁ -3 _N , N connected in series through optical fiber optical combiners 4 ₁ -4 _N , where N is a natural number and can take values, for example, 1, 2, 3, 4, 5, etc., an optical coupler 5, a circulator 6, an optical filter 7, the first photodetector 8, the second photodetector 9 , temperature determination controller 10, laser source about radiation 1 is connected to the input of the first of the N optical splitter 2 ₁ through a fiber, the first output of each of the previous N optical splitter 2 ₁ -2 _{N is} connected to the input of each subsequent corresponding N optical splitter 2 ₁ -2 _N , the second output of each of N optical splitter 2 ₁ -2 _{N is} connected to the input of the corresponding from N optical sensor 3 ₁ -3 _N through a fiber, the output of each of N optical sensor 3 ₁ -3 _{N is} connected to the second input of the corresponding N optical combiner 4 ₁ -4 _N by a fiber, the first input of each of the previous N optical combiners 4 ₁ -4 _N connected to the output of each subsequent corresponding N optical combiner 4 ₁ -4 _N , the output of the first N optical combiner 4 ₁ connected to the input optical coupler 5 by a fiber, the first output of the optical coupler 5 is connected to the input of the first photodetector 8 by a fiber, the second output of the optical coupler 5 is connected to the input of the circulator 6 by fiber of the optical fiber, the first output of the circulator 6 is connected to the optical filter 7 via a fiber, the second output of the circulator 6 is connected to the input of the second photodetector 9 via a fiber, the outputs of the first and second photodetectors 8 and 9 are connected to the first and second inputs of the temperature determination controller 10, respectively, by electrical wires, the laser radiation source 1 is made broadband, and each optical sensor 3 ₁ -3 _{N is} made on the basis of the Bragg fiber grating 11 (Fig. 2) with two phase π-shifts 12 (Fig. 2), symmetrically located relative to its central wavelength, and spaced by Δλ.

In particular, in optical sensors 3 ₁ -3 _{N the} phase shift is 12 Δλ _i ≠ Δλ _j , where i and j are the numbers of optical sensors 3 ₁ -3 _N , i, j∈N, where N is the set of optical sensors 3 ₁ - 3 _N , while the difference Δλ _i -Δλ _j is not equal and is not a multiple of the whole and particular Δλ _i and Δλ _j (Fig. 3). The components of the circuit according to FIG. 1, a laser source 1, a first photodetector 8, a second photodetector 9 and a temperature determination controller 10 are connected to power sources (the power supply system in FIG. 1 is not shown), a signal processing program is recorded according to the algorithm shown in FIG. 4 to the temperature determination controller 10.

Consider the operation of a fiber optic thermometer (Fig. 1 - Fig. 4). Broadband radiation from the laser source 1 (Fig. 1) is sent to the optical sensors 3 ₁ -3 _N through the optical splitters 2 ₁ -2 _N.

In the optical sensors 3 ₁ -3 _N in the transparency windows, two narrow-band sections with a spacing Δλ are cut from the full spectrum of light, while the phase shift spacing is 12 Δλ _i ≠ Δλ _j , where i and j are the numbers of the optical sensors 3 ₁ -3 _N , i , j∈N, where N is the set of optical sensors 3 ₁ -3 _N , and the difference Δλ _i -Δλ _{j is} not equal and is not a multiple of the whole and particular Δλ _i and Δλ _j . Next, the optical combiners 4 ₁ -4 _N combine the signals transmitted through the optical sensors 3 ₁ -3 _N , and the received signal goes to the optical coupler 5, where it is divided into two parts, one of which is sent to the first photodetector 8, the other through the circulator 6 in the optical filter 7, where the signal is attenuated, in accordance with its spectral position relative to the reflection characteristics of the optical filter 7, the reflected signal from the optical filter 7 through the circulator 6 enters the second photodetector 9. Thus At the output of the first photodetector 8, an beat envelope of two frequency components of equal amplitude with a frequency corresponding to the spacing Δλ is formed, and at the output of the second photodetector 9, an beat envelope of two frequency components of different amplitude is formed, depending on the spectral position passed from optical sensors 3 ₁ -3 _N light, also with a frequency corresponding to the separation Δλ. The temperature determination controller 10 receives signals from the first and second photodetectors 8 and 9 and processes them according to the algorithm shown in FIG. four.

Fiber optic thermometer can be created on the following elements, designed to work at a wavelength of 1550 nm:

- source of laser radiation 1 SLD-1550-3 - laser diode of the company "Superlum";

- optical splitters 2 ₁ -2 _N , optical coupler 5, optical combiners 4 ₁ -4 _N - optical coupler TELECOM-TEST of LLC Production and Trade Company SOKOL;

- optical sensors 3 ₁ -3 _N - Bragg fiber lattice 11 with at least two phase shifts 12 recorded in the Scientific Research Institute of Prefesses, Knitu-KAI (Kazan);

- circulator 6 - 3PIOС-1550 circulator of the Flyin company;

- optical filter 7 - Bragg fiber lattice recorded in the Scientific and Research Center “Photonika” (Moscow), or the Scientific Research Institute of Scientific and Practical Technologies Knitu-Kai (Kazan), or Inversion-Fiber (Novosibirsk), or Inversion-Sensor (Perm), etc., or purchased sensors from these firms and FiberSensing;

- the first photodetector 8, the second photodetector 9 high-speed fiber-optic InGaAs / InP microwave broadband PIN photodetectors (receiving modules) of NPF DiLaz, for example, DFDMSh-40-16;

- temperature determination controller 10 - microprocessor controller based on chips from Atmel, Microchip, etc .;

When implementing a fiber-optic thermometer, all of these blocks of generation, reception and processing of signals can be performed on a single chip or in an integrated version.

Compared with the prototype, the proposed fiber-optic thermometer allows to simplify the circuit by eliminating the complex and expensive source of dual-frequency laser radiation from the circuit.

An additional advantage of the proposed fiber-optic thermometer is the ability to connect more than one temperature sensor, as well as the possibility of multiplexing.

Tests of the prototype fiber-optic thermometer were carried out on optical sensors manufactured at the Scientific Research Institute of Scientific and Practical Sciences Knitu-KAI (Kazan), calibrated on optical ANDO spectrum analyzers in the same place, the number of optical sensors is 256. Studies have shown that the proposed fiber-optic thermometer allows significantly simplify its scheme, while the error of temperature measurement is ± 0.3 ° C in the range of 240 ° C. The measurement error was determined mainly by the error of the ADC of the temperature determination controller, as well as the inaccuracy of manufacturing temperature sensors based on Bragg fiber gratings with two phase shifts.

All this allows us to talk about achieving a solution to the technical problem - a simplification of the fiber optic thermometer.

Claims (2)

1. A fiber optic thermometer containing a laser source, an optical splitter, an optical sensor, a first photodetector, a second photodetector, a temperature determination controller, a laser source is connected to the input of the optical splitter via a fiber, the second output of the optical splitter is connected to the input of the optical sensor by fiber optic cable, characterized in that an optical coupler, a circulator, an optical filter, N-1 are subsequently introduced into it optical couplers flaxly connected by optical fibers, N-1 optical sensors, N optical fiber combiners connected in series by optical fibers, where N is a natural number and N≥1, and the first output of each previous N optical splitter is connected to the input of each subsequent corresponding N optical splitter, the second output of each optical splitter introduced from N-1 is connected to the input of the corresponding optical sensor from N-1 through a fiber optic fiber , the output of each of the N optical sensors is connected to the second input of the corresponding N optical combiner via a fiber, the first input of each of the previous N optical combiners is connected to the output of each subsequent corresponding N optical combiner, the output of the first of the N optical combiners is connected to the optical input coupler by means of a fiber optic fiber, the first output of the optical coupler is connected to the input of the first photodetector by a fiber optic fiber a, the second output of the optical coupler is connected to the input of the circulator through the fiber, the first output of the circulator is connected to the optical filter through the fiber, the second output of the circulator is connected to the input of the second photodetector via the fiber, the outputs of the first and second photodetectors are connected to the first and second inputs of the determination controller temperature, respectively, by means of electric wires, the laser radiation source is made broadband, and each optical Occupancy is based on fiber Bragg grating with two phase shifts of π-symmetrically arranged with respect to its center wavelength and spaced by an amount Δλ. 2. The fiber-optic thermometer according to claim 1, characterized in that in the optical sensors the phase shift is Δλ _i ≠ Δλ _j , where i and j are the numbers of optical sensors, i, j∈N, where N is the set of optical sensors, this difference Δλ _i -Δλ _{j is} not equal and not a multiple of the whole and particular Δλ _i and Δλ _j .

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