Method and system for constructing frequency domain reflecting fiber grating sensing network of bus topological structure

Abstract

The invention relates to a method and a system for constructing a frequency domain reflecting fiber grating sensing network of a bus topological structure. The frequency domain reflecting fiber grating sensing network of the bus topological structure is formed by connecting fiber grating distributed sensing network branches and a network main line both based on the frequency domain reflecting technology by using a three-terminal optical fiber circulator, a four-terminal optical fiber circulator and a network node upper and lower carrier wave division multiplexer consisting of two chirped fiber gratings with complementary reflecting spectra. The network has high capacity and high spatial resolution and increases the measuring distance by dozens of times. The network does not adopts an optical fiber divider, so the insertion loss is low; a signal transmission main line can adopt an armored optical cable and sensing measurement branches can be connected through a flexible optical fiber or an optical cable, so assembling flexibility and convenience of a fiber grating sensor are guaranteed; and damage to the branched fiber grating sensor does not influence normal signal transmission of other branched fiber grating sensors, so the survival rate of the network sensor and the operating reliability of the network are high.

Description

technical field [0001] The invention relates to a fiber grating sensor network, in particular to a method and system for constructing a fiber grating sensor network with large capacity, high flexibility, and long-distance intensive measurement, and belongs to the technical field of fiber grating sensing. technical background [0002] One of the technical advantages of fiber grating sensing is to combine multiple fiber grating Connected in series to form a fiber grating sensor network, it has broad application prospects in the safety monitoring system of large-scale projects and major equipment. In the fiber grating sensor network system with wavelength division multiplexing, the positioning of the fiber grating sensor adopts wavelength coding, and the measurement of the fiber grating sensor also uses wavelength signals. The measurement range of the sensor occupies a certain wavelength bandwidth, and the total bandwidth resource of the light source In limited cases, the netw...

AI Technical Summary

Problems solved by technology

In the fiber grating sensor network system with wavelength division multiplexing, the positioning of the fiber grating sensor adopts wavelength coding, and the measurement of the fiber grating sensor also uses wavelength signals. The measurement range of the sensor occupies a certain wavelength bandwidth, and the total bandwidth resource of the light source In limited cases, the network capacity is greatly restricted

In the fiber grating sensor network system using time division multiplexing, although the network capacity is greatly improved, the spatial resolution of sensor measurement is limited (see literature [1])

Fiber Bragg grating sensor network using frequency domain reflectometry can solve the problem of network capacity and spatial resolution (see literature [2] and literature [3]), however, because frequency domain reflection technology is a coherent detection technology, due to the influence of light source Coherence is limited, so the measurement distance of the network is very limited

[0003] In these FBG sensor network systems using "wavelength division multiplexing", "time division multiplexing", and "frequency domain reflection", there are not only such shortcomings as limited network capacity, low spatial resolution, and short measurement distances. Insufficient, and because the construction of these sensor networks is the direct series connection of fiber grating sensors, when one of the fiber grating sensors fails or is damaged, all the signals of the following fiber grating sensors will be interrupted, so the sensor network has serious problems. reliability issues

Chinese Patent No. 201010250519.7 provides a "frequency domain reflection" and "wavelength division multiplexing" mixed fiber grating sensor network system, which increases the measurement distance of the frequency domain reflection fiber grating sensor network by dozens of times, but the network construction still uses Serial connection mode, the network reliability problem has not been solved

In this topological fiber grating sensor network, the fiber grating sensors are no longer directly connected in series, but the fiber grating sensor is separated from the signal transmission bus by using a "fiber splitter", and the reliability of the network is improved. However, its network capacity is still limited by the bandwidth of the light source just like the WDM sensor network

At the same time, the network uses fiber optic splitters as optical splitting devices. Its optical splitting function is at the cost of the loss of light intensity of the branches, which greatly affects the number of multiplexing and measurement distances of the network.

In order to make up for the loss of signal energy, both literature [4] and literature [5] use Raman fiber amplifiers, which undoubtedly increases the cost of the network

The Chinese patent and document [6] with the patent number of 200810157486.4 provides a star structure network construction method, which is a parallel network connection method, which has enhanced reliability and maintainability. However, This network construction method is at the cost of increasing the scale of the network backbone transmission optical fiber or cable and signal receiving and processing equipment. At the same time, a large number of optical fiber splitters are used as optical splitting devices in the links of the star network. 4] The same capacity and cost issues as the sensor network given in [5]

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