JP2001099702A - Optical fiber multiplex sensor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiplex system of optical fiber sensors. SOLUTION: A light source 1-1 is connected to a transmission gate 2-1, and connected to a wavelength multiplex coupler 3, and connected to a sensor array. In each sensor part composing a sensor array, an optical branching filter for a sensor 4-1 is connected to a coupler for a sensor 5-1, and one side is connected to a sensing fiber 6-1, and connected to a light-receiving part side through a reflector 7-1, the coupler for a sensor 5-1 and an optical multiplexer for a sensor 10-1. The other side is connected to a reference fiber 8-1, and connected similarly to the light-receiving part side. In the light-receiving part, a light- receiving optical branching filter 12-1 is connected to an O/E converter 13-1, and connected to a reception gate 14-1, and connected to a processor 15-1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor using both wavelength division multiplexing and time division multiplexing, capable of expanding the number of multiplexable sensor signals and transmitting the sensor signals over a general-purpose network. Multiplex system.

[0002]

2. Description of the Related Art Document name: ADKersey et al., "64-eleme"
nt time-division multiplexed interferometic sensor
array with EDFA telemetry "Optical Fiber Communi
cation96, Vol.2 1996. The above-mentioned literature describes a sensor system in which a sensor unit is connected via a delay line and a light pulse is transmitted from a light source to form a time-series pulse of each sensor signal and perform time-division multiplex transmission. ing.

[0003]

However, in the above configuration, it is difficult to further increase the number of multiplexable sensors, and there is no function for transmitting sensor signals on a general-purpose network. There is a problem.

[0004]

In order to solve the above-mentioned problems, an optical fiber multiplex sensor system according to the present invention comprises a light source outputting a plurality of different wavelength pulse groups, and a plurality of different wavelength pulse groups output from the light source. And a sensor array including a plurality of sensors connected via a delay line, to which a multiplex output from the multiplexer is input. A sensor duplexer that separates and outputs a specific wavelength component from the output multiplexing, and an interferometer that receives the specific wavelength component output from the sensor duplexer and outputs interference light according to an optical path difference. A sensor multiplexer for multiplexing and outputting interference light output from each of the interferometers of the plurality of sensors, and demultiplexing a specific wavelength component of the interference light from the multiplex output from the sensor multiplexer. Multiple duplexers that output Select time division channel by the light pulse received from the column gate of a specific wavelength component of the interference light output from the demultiplexer, and a plurality of demodulation processing unit for performing a demodulation process.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 <Configuration> FIG. 1 is a diagram showing the configuration of a multiple sensor system according to Embodiment 1 of the present invention. The light source 1-1 is connected to the transmission gate 2-1. Similarly, the light source 1-2 is connected to the transmission gate 2-2, and the transmission gate 2-1 and the transmission gate 2-2 are connected to the wavelength multiplexing coupler 3. , Connected to the sensor array.

In the sensor array, the optical demultiplexer for sensor 4-1
Is connected to the sensor coupler 5-1; one is connected to the sensing fiber 6-1; the reflector 7-1, the sensor coupler 5-1;
It is connected to the light receiving section via the optical multiplexer for sensor 10-1.
The other is connected to the reference fiber 8-1, and similarly connected to the light receiving section. In the light receiving section, the light splitter 12
-1 is connected to the O / E converter 13-1, connected to the reception gate 14-1, and connected to the processor 15-1.

[0007] <Operation> source 1-1 sends a continuous light of wavelength lambda _1, transmission gates 2-1 pulsing the continuous light at periodic constant time width. Similarly, light pulses having different wavelengths of the wavelength λ ₂ are transmitted by the light source 1-2 and the transmission gate 2-2.

A plurality of pulse lights having different wavelengths are multiplexed by the wavelength multiplexing coupler 3 and sent to the sensor array.

In the sensor array, the optical demultiplexer for sensor 4-1
, Only the wavelength λ ₁ is selected, and the captured optical pulse of the wavelength λ ₁ is power-divided by the sensor coupler 5-1. One branch light passes through the sensing fiber 6-1 and is reflected by the reflector 7-1, and is returned to the light receiving unit side via the sensor coupler 5-1 and the sensor optical multiplexer 10-1. The other branch light passes through the reference fiber 8-1, and in the same manner, the reflector 9
-1, reflected by the sensor coupler 5-1, sensor optical multiplexer 10-
The light is returned to the light receiving section via 1. Sensing fiber 6-1
However, when expansion or contraction or a change in the refractive index occurs in response to a change in sound pressure or temperature as a detection signal, a phase change of the propagating light occurs.
Therefore, by detecting the phase change by causing the light passing through the sensing fiber and the light passing through the reference fiber to interfere with each other, it is possible to detect a change in sound pressure or a change in a temperature signal.

The optical splitter 4-1 for the sensor and the optical multiplexer 10-1 for the sensor are composed of a circulator and a fiber Bragg grating (FBG). The FBG has a refractive index grating so that the wavelength λ ₁ is partially reflected. interval is set, demultiplexing a wavelength of lambda ₁ only, the multiplexing performed.

[0011] lambda ₁ partially transmitting wave and the wavelength lambda ₁ other than the transmitted pulse in the sensor optical demultiplexer 4-1 optical demultiplexer sensor 4-2
Is sent to the next-stage sensor unit by the same operation via, and returned to the light-receiving unit side. In this sensor unit, for example, it sets the structure for partially reflecting the FBG at a wavelength lambda _2, so that only the wavelength lambda ₂ is selected.

Further, in addition to the above-described wavelength multiplexing, a next-stage sensor for the same wavelength component is connected via delay fibers 11-1 and 11-2. As a result, time division multiplex transmission can be performed by time separation of the transmission pulse light. Only the wavelength lambda ₁ by the optical demultiplexer 4-11 sensor via a delay fiber 11-1 is selected, the sensor optical demultiplexer 4-1 in the same manner as the sensor coupler 5-11, optical multiplexer sensor The light is returned to the light receiving unit side via 10-11 and further via delay fiber 11-2.

[0013] In the light receiving portion, the light-receiving optical demultiplexer 12-1 (the same structure as the optical demultiplexer sensor), wavelength components lambda ₁ is selected, the O / E converter 13-1, the sensing The interference wave pulse between the light passing through the fiber and the light passing through the reference fiber is square-detected, time-sliced by the reception gate 14-1, and sent to the processor 14-1. The selected wavelength components of the light-receiving optical demultiplexer 12-2 lambda ₂ is sent to lambda ₁ in the same manner as 14-2. The processor performs a demodulation process on the sound pressure or temperature signal.

In this embodiment, the optical demultiplexer and the multiplexer for the sensor and the optical demultiplexer for the light receiving are a circulator and an FB.
Although the description has been given of the method configured by G, other methods such as an interference filter may be used. Although the light source and the transmission gate have different configurations, they may be integrated. Although the sensor section has been described using the Michelson interferometer, it is also possible to use a Mach-Zehnder interferometer. Further, the sensor unit is described in a system in which only the sensing fiber operates on a signal, but a mechanism in which the sensing fiber and the reference fiber perform a differential operation is also possible.

Although a configuration is described in which the sensing fiber and the reference fiber are terminated only by a reflector, a reflector (Faraday Rotator Mirror) provided with a magnetic element may be used. In the case where the transmission path is long, it is possible to prevent transmission loss by connecting an amplification optical amplifier or the like on the transmission path.

<Effects> As described in detail above, by performing wavelength multiplexing in addition to time division multiplexing, multiplexing can be performed by multiplying the number of wavelength multiplexes by the number of time division multiplexing. , The number of possible multiplexes increases dramatically.

Therefore, the number of sensor arrays can be increased, and a large-scale and large-scale sensor system can be constructed.

<Embodiment 2><Configuration> FIG. 2 is a diagram showing the configuration of a multiple sensor system according to Embodiment 2 of the present invention. 2 is a configuration example for connecting the. The same components as those in the specific example 1 are denoted by the same reference numerals, and description thereof will be omitted. In the specific example 2, in addition to the configuration of the specific example 1, the optical multiplexer for light source 20-1 and the optical demultiplexer for light reception 30-1 are used.
Is provided.

<Operation> Light pulses having different wavelengths are emitted from the light source 1-1.
The signal is generated by the transmission gate 2-1 and the like, is multiplexed by the wavelength multiplexing coupler 3, and is transmitted to the transmission line via the light source optical multiplexer 20-1. The FBG in the optical multiplexer for light source 20-1 is connected to one having a reflection wavelength equal to the wavelength to be transmitted.

The light receiving section is connected via a light receiving optical splitter 30-1. The FBG in the light receiving optical splitter 30-1 is connected to one having a reflection wavelength equal to the wavelength to be processed.

The basic operation of the sensor system is the same as that of the first embodiment.

<Effects> In addition to the effects described in the first embodiment,
Since the light source system and the processing system can be connected at any point on the transmission line, a sensor system can be constructed on a general-purpose optical fiber network.

<< Embodiment 3 >><Configuration> FIG. 3 is a diagram showing the configuration of a multiple sensor system according to Embodiment 3 of the present invention, wherein a centralized sensor array is formed at an arbitrary point on a transmission line, and a distributed sensor system is formed. It is an example of composition of a sensor system combined with an array. The same components as those in the specific example 1 are denoted by the same reference numerals, and description thereof will be omitted. In the specific example 3, in addition to the configuration of the specific example 1, the optical demultiplexer 40-1 for the centralized sensor is provided.
And a multiplexer 50-1 for a centralized sensor.

<Operation> The optical demultiplexer 40-1 for the centralized sensor is connected to a plurality of FBGs having different partial reflection characteristics.
A plurality of wavelength components are sent to a centralized sensor array.

The centralized sensor array is a sensor array according to the first embodiment, and the output of the array is a multiplexer for the centralized sensor.
Connected to the transmission line via 50-1.

The basic operation of the sensor system is the same as that of the first embodiment.

<Effect> A centralized sensor can be formed at any point, the multiplex transmission signal can be mounted on a general-purpose optical fiber network, and a flexible and large-scale sensing system can be constructed.

<Embodiment 4><Configuration> FIG. 4 is a diagram showing the configuration of a multi-sensor system according to Embodiment 4 of the present invention, wherein a centralized sensor array is formed at an arbitrary point on a transmission line and a distributed sensor system is formed. It is an example of composition of a sensor system combined with an array. The same components as those in the specific example 1 are denoted by the same reference numerals, and description thereof will be omitted. In Example 4, in addition to the configuration of Example 1, an optical coupler for sensor branch coupling is provided.

<Operation> The optical splitter for sensor 4-j splits an arbitrary wavelength component and sends it to the centralized sensor array via the input / output branch for centralized sensor 60-j.

In the centralized sensor array, optical branching and optical coupling to each sensor section are performed using a sensor branch coupling optical coupler. The optical couplers for sensor branching are connected via a delay fiber for time-division processing. The output of the array is I / O branch 60-j for centralized sensor, optical multiplexer 10 for sensor.
Connected to the transmission line via -j.

The basic operation of the sensor system is the same as that of the first embodiment.

<Effects> In addition to the effects described in the third embodiment,
Components of centralized sensor array are circulator and FB
An optical coupler can be used without using G, and the transmission line can be made up of a single fiber, which makes it possible to reduce the size and cost.

<Embodiment 5><Configuration> FIG. 5 is a diagram showing the configuration of a multiple sensor system according to Embodiment 5 of the present invention. A processing system is connected to an arbitrary point on a transmission line, and is essential for phase demodulation processing. This is an example of a configuration of a system in which a frequency for synchronous detection is extracted from a received signal and used.
The same components as those in the specific example 1 are denoted by the same reference numerals, and description thereof will be omitted. In the specific example 5, in addition to the configuration of the specific example 1, a modulation frequency extractor 90-1 is provided.

[0034] <Operation> source for generating an arbitrary wavelength λ _{j 1-j}
In has a function of generating an FM modulated light sinusoidal frequency f _0.

The light receiving section is connected via a light receiving optical splitter 30-1. In the wavelength component of _λj , which is demultiplexed by the optical demultiplexer 12-j, the interference signal is square-detected by the O / E converter 13-j, and the channel is selected by the reception gate 14-j and converted into a continuous signal. Is done. Continuous signal I (t), when the display is omitted DC component definitive and I (t) = Acos (Ccos2πf 0 t + φ) ··· (1). Here, C is a modulation index, which is a function of the maximum frequency shift of FM modulation at the light source and the optical path difference between the sensing fiber and the reference fiber of the sensor unit. A indicates a constant amplitude value. φ is composed of a signal component φ _s and an initial phase component φ ₀ .

Although φ _s usually deals with a small amount, for example, 0.5ra
In the case where d is equal to or less than d, when the components near the respective frequencies n of the fundamental wave and the second harmonic of the modulation frequency f ₀ are displayed from Expression (1), J ₁ (C) cos2πf ₀ t sin φ ₀ and J ₂ (C) cos4πf ₀ t
cosφ ₀ . J _n is an nth-order Bessel function. Therefore, when a narrow band filter or the like of each of the center frequencies f ₀ and 2f ₀ is connected to the output of the reception gate 14-j, it depends on φ ₀ which changes slowly with time, but either of f ₀ or 2f ₀ Can always be extracted. Even in a time zone where only one of the frequencies can be extracted, f ₀ ,
Both frequencies of 2f ₀ can be reproduced.

Using the extracted frequencies f ₀ and 2f ₀ , J ₁ (C) sin φ and J _{2 are obtained} by synchronous detection from the output of the reception gate 14-j.
(C) By extracting cos φ and performing a predetermined operation, φ is demodulated.

The basic operation of the sensor system is the same as that of the first embodiment.

<Effects> In addition to the effects described in the second embodiment,
Since the frequency tuning of the light source system and the processing system can be performed, the light source system and the processing system can exist as independent systems, respectively, and can be installed at arbitrary different points. Therefore, a sensor system having a more flexible configuration can be constructed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a multiple sensor system according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a multiple sensor system according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a multiple sensor system according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a multiple sensor system according to Embodiment 4 of the present invention.

FIG. 5 is a diagram showing a configuration of a multiple sensor system according to Embodiment 5 of the present invention.

[Explanation of symbols]

 Light source: 1-1 Transmission gate: 2-1 Wavelength multiplexing coupler: 3 Optical demultiplexer for sensor: 4-1 Sensor coupler: 5-1 Sensing fiber: 6-1 Reflector: 7-1 Reference fiber: 8 -1 Optical multiplexer for sensor: 10-1 Optical demultiplexer for light reception: 12-1 O / E converter: 13-1 Receiving gate: 14-1 Processor: 15-1

Claims (1)

[Claims] 1. A light source that outputs a plurality of different wavelength pulse groups, a multiplexer that multiplexes and outputs a plurality of different wavelength pulse groups output from the light source, and a multiplexer that is output from the multiplexer. A sensor array including a plurality of sensors connected via a delay line to which a wave is input, and the plurality of sensors are configured to separate and output a specific wavelength component from a multiplex output from the multiplexer. A specific wavelength component output from the sensor duplexer, and an interferometer that outputs interference light in accordance with an optical path difference, each of which is output from each of the plurality of sensors. A sensor multiplexer for multiplexing and outputting the interference light, a plurality of duplexers for separating and outputting a specific wavelength component of the interference light from the multiplex output from the sensor multiplexer, Wavelength component of the interference light output from the The time division channel is selected by the reception gate from the optical pulse train of
An optical fiber multiplex sensor system, comprising: a plurality of demodulation processors for performing a demodulation process.