JP2000278216A - Method for transmitting and detecting information while utilizing polarization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for the transmission of a reference signal, to unnecessitate an electric cable and to facilitate the long-distance transmission of information by making a modulation frequency at each spot into multiple of a power supply frequency and making these modulation frequencies different for each spot. SOLUTION: Power supply frequency regulators 11a-11z generate signals having the frequency of integer multiple from commercial power sources 12a-12z and presets a multiple different for each spot. On the side to detect information, the propagation light of a modulated polarizing state is converted to an electric signal by an ODE converter 4 and in order to demodulate that signal, a demodulator 9' is provided while having a function for switching the frequency of a power source 12' to the same reception frequency as a modulation frequency for each of modulators 3a-3z by using a power supply frequency regulator 11'. Then, the signal demodulated for each frequency is sent to a signal processor 10 and the signal processor 10 can obtain sensor information at each spot by D/A converting the demodulated digital signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting sensor information at multiple locations by modulating the polarization state of light propagating through an optical fiber and detecting the information in a concentrated manner. The present invention relates to an information transmission method and an information detection method using polarized waves that do not require a plurality of demodulators.

[0002]

2. Description of the Related Art A conventional information transmission method and information detection method using polarized waves will be described with reference to FIG.

On the information transmission side, a light source 1 and an O / E converter 4 are connected by a single optical fiber 2, and light propagating in the optical fiber 2 is transmitted to a plurality of points along the optical fiber 2. Modulators 3a to 3z that modulate by applying an external force to the optical fiber 2 are attached. Modulators 3a to 3z
A / D-converts the information of the sensors 8a to 8z at the respective points by the sensor information converters 7a to 7z, and based on the A / D converted codes, propagates the light at the modulation frequency from the transmitters 5a to 5z. Is modulated.

On the information detection side, the demodulators 9a to 9z are converted into electric signals by the O / E converter 4 and demodulated by the respective converters 3a to 3z so as to demodulate the signals. Have been assigned. In these demodulators 9a to 9z, the frequencies (modulation frequencies) used for the modulation by the transmitters 5a to 5z.
Is referenced via the reference signal cables 6a to 6z, and the same frequency as the modulation frequency is used as a reception frequency for demodulation. The demodulated signal is sent to the signal processing device 10. The signal processing device 10 can obtain sensor information of each point.

[0005]

Since the signals used for modulation by the transmitters 5a to 5z are referred to and demodulated by the demodulators 9a to 9z, reference signal cables 6a to 6z are connected between the two.
Must be connected. In the case of long-distance transmission, it is difficult to transmit a reference signal. Further, since a plurality of demodulators are provided, there is a problem that the device becomes large.

An object of the present invention is to solve the above-mentioned problems and to provide an information transmission method and an information detection method using a polarized wave which does not require transmission of a reference signal and does not require a plurality of demodulators.

[0007]

In order to achieve the above object, an information transmission method according to the present invention is provided. An information transmission method for modulating and transmitting information at each point according to a modulated polarization state, wherein a modulation frequency at each point is a multiple of a power supply frequency, and these modulation frequencies are different for each point. Is used.

The information detecting method is a method for detecting information at each modulation frequency by demodulating propagation light in an optical fiber whose polarization state is modulated at a plurality of different frequencies. One demodulator whose reception frequency is switchable is used for the multiple propagation light in the optical fiber, and the demodulation is performed by switching the reception frequency to a multiple of the power supply frequency.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an information transmission system for implementing the information transmission method and the information detection method of the present invention.

On the information transmission side, the light source 1 and the O / E converter 4 are connected by one optical fiber 2, and the light propagating in the optical fiber 2 is transmitted to a plurality of points along the optical fiber 2. Modulators 3a to 3z that modulate by applying an external force to the optical fiber 2 are attached. Modulators 3a to 3z
A / D-converts the information of the sensors 8a to 8z at the respective points by the sensor information converters 7a to 7z, and based on the A / D converted codes, propagates the light at the modulation frequency from the transmitters 5a to 5z. Is modulated. The modulation frequencies output from the transmitters 5a to 5z are configured to be adjustable from the frequencies of the power supplies 12a to 12z using the power supply frequency adjusters 11a to 11z. The modulation frequency at each point is a multiple of the power supply frequency, and these modulation frequencies are different for each point. The power supplies 12a to 12z are commercial power supplies. The power supply frequency adjusters 11a to 11z generate a signal whose frequency is an integral multiple from the commercial power supply, and set a different multiple for each point in advance.

On the information detection side, the O / E converter 4 converts the propagation light whose polarization state is modulated into an electric signal and demodulates the signal. A demodulator 9 'having a function of switching to the same reception frequency as the modulation frequency of each of the modulators 3a to 3z using 11' is provided. The signal demodulated for each frequency is
The signal is sent to the signal processing device 10. The signal processing device 10 can obtain sensor information of each point by performing D / A conversion of the demodulated digital signal.

The power supply 12 'is a commercial power supply, and the power supply frequency regulator 11' can generate a signal whose frequency is an integral multiple from the commercial power supply. The demodulator 9 'can perform demodulation at an arbitrary reception frequency. The signal processing device 10 includes:
When a different multiple is set for each point on the information transmission side, the relationship between the point and the multiple (or frequency) is stored, and the relationship is set according to the frequency output by the power supply frequency adjuster 11 '. Thus, it is possible to identify from which point the signal taken out of the demodulator 9 'comes from.

The operation will be described below.

Continuous light from a light source 1 enters an optical fiber 2. In order to transmit the information of the sensors 8a to 8z at each point, the information is transmitted to the sensor information converters 7a to 7z at A / A.
D-converted, and based on the A / D-converted code, the transmitter 5
The propagating light is modulated at a modulation frequency from a to 5z. The modulation frequencies output from the transmitters 5a to 5z are generated by using the power supply frequency adjusters 11a to 11z, and the power supply 12a to 12z at each point is determined by a multiple set in advance for each point.
Is generated from the frequency of That is, each modulation frequency is a multiple of the power supply frequency and different from each other.

As described above, using the modulation frequencies from the transmitters 5a to 5z, the modulators 3a to 3z modulate the polarization state of the propagation light of the optical fiber 2. For example, digital information can be transmitted by setting the logic 1 of the code to modulation and the logic 0 to no modulation. The thus propagated light propagates through the optical fiber 2 and reaches the side where information is detected.

On the side that performs information detection, first, the O / E converter 4 converts the polarization state of the propagation light into an electric signal. For example, by receiving light through a filter that transmits a specific polarized wave, the propagating light with and without modulation is converted into an electric signal having a large amplitude and a small amplitude. The electric signal is demodulated by the demodulator 9 '. The receiving frequency used for demodulation is changed from the frequency of the power supply 12 'to the modulator 3a using the power supply frequency adjuster 11'.
Switching to the same reception frequency as the frequency for every 3z. Since demodulation is performed by switching the reception frequency in this manner, electric signal components at each point can be selectively extracted. By demodulating at each reception frequency, the code at each point is demodulated.

These digital information are stored in the signal processing device 10.
Sent to The signal processing device 10 converts the digital information into analog information, and detects the position (point) of the sensor from the frequency (or multiple) used for each demodulation. In this manner, the signal processing device 10 can obtain analog information of each point.

[0019]

The present invention exhibits the following excellent effects.

(1) Since transmission of a reference signal is not required, an electric cable is not required and long-distance transmission is facilitated.

(2) A plurality of demodulators are not required, and the device on the information detection side is simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an information transmission system that implements an information transmission method and an information detection method of the present invention.

FIG. 2 is a configuration diagram of a conventional information transmission system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Optical fiber 3a-3z modulator 4 O / E converter 5a-5z oscillator 9 'Demodulator 10 Signal processor 11a-11z, 11' Power frequency adjuster 12a-12z, 12 'Power supply

Claims (2)

[Claims] 1. An information transmission system for modulating a polarization state of light propagating in an optical fiber by applying an external force to the optical fiber at a plurality of points of the optical fiber, and transmitting information at each point based on the modulated polarization state. An information transmission method using polarization, wherein a modulation frequency at each point is a multiple of a power supply frequency, and these modulation frequencies are different for each point. 2. An information detection method for demodulating propagation light in an optical fiber whose polarization state is modulated at a plurality of different frequencies and detecting information at each modulation frequency, wherein the modulation frequency is a multiple of a power supply frequency. An information detection method, wherein one demodulator capable of switching a reception frequency is used for a propagation light, and the demodulation is performed by switching a reception frequency to a multiple of a power supply frequency.