JPH09210740A - Submarine observation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a highly reliable system structure inexpensively in a submarine observation system which eliminates the need for a feeder path for a submarine cable and an observing device and, dispenses with an electric circuit by arranging a light wave demultiplexer and a light wave multiplexer employing a light device in the observing device. SOLUTION: Light λ1-λ3 with a plurality of wavelengths allocated to observed points is transmitted to a submarine cable 10 by WDM transmission and light signals thereof are demultiplexed or multiplexed in terms of wavelengths by a light wave demultiplexer or a light wave multiplexer provided for the observing devices A-C at the observed points. The demultiplexed light is supplied to fiber optics applied sensors 8A-8C and undergoes a phase modulation to be overlapped on the submarine cable 10 by the demultiplexer again (λ1A-3C). The light is turned back within an observing device C at the final stage and returned to a land station as intact through the devices A-C. The light with varied wavelengths λ1A-λ3C is demultiplexed by the land station and a light heterodyne detection is performed to obtain observation information at the observed points.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seabed observation system, and more particularly to a seabed observation system for performing various seabed observations of water pressure, sound, magnetic field, etc. at a plurality of observation points by using a seabed optical cable.

[0002]

2. Description of the Related Art As a conventional seafloor observation system of this type, there is, for example, a tsunami meter device. This tsunami meter device uses a seafloor table to detect a pressure change as a change in a crystal oscillation frequency as an electric signal, and to detect the change. The signal is converted to an optical signal at the same optical wavelength and transmitted to a land-based observation terminal using an optical fiber pair. Therefore, the tsunami meter device includes a tsunami meter sensor unit, an O / E conversion unit that converts an electric signal of the tsunami meter sensor into an optical signal, a transmission unit that sends the optical signal to a submarine table, and a device therefor. And a power supply unit for supplying power to the power supply.

[0003] In addition, since the same optical wavelength is used as an optical signal, when there are a plurality of observation points, it is necessary to prepare a submarine cable containing a plurality of optical fibers serving as transmission paths.

[0004]

In the conventional seafloor observation system, since a sensor section, an O / E conversion section, a transmission section, and the like need an electric signal, the land terminal station needs a power supply device, The observation device requires a power supply unit and the like. For this reason, the seafloor observation device is complicated in structure and structure, and is required to have long-term withstand voltage characteristics in the seafloor environment because of power supply. In addition, since each observation device uses the same light wavelength, if there are a plurality of observation points, a plurality of fiber pairs are required. Therefore, the conventional seafloor observation system has a disadvantage that it requires a very high cost.

It is an object of the present invention to provide a seafloor observation system having a very simple structure using a single optical fiber pair and requiring no power supply to the observation apparatus.

Another object of the present invention is to provide a highly reliable ocean bottom observation system by using only optical devices that do not require power supply on the observation apparatus side.

[0007]

According to the present invention, there is provided a seafloor observation system for performing seafloor observation at a plurality of observation points by using a submarine optical cable, wherein each of the observation points is previously in advance. Transmitting means for wavelength-multiplexing allocated different wavelength lights to the submarine optical cable, and wavelength light allocated to the observed point from the optical signal of the submarine optical cable provided at each of the observed points Branching means for selectively branching, a sensor means provided at each of the observed points for modulating phase information of wavelength light branched by the branching means according to the observed information, and each of the observed points A submarine observation system is provided, which is provided and includes a combining unit that combines the sensor information with an optical signal of the submarine optical cable.

The sensor means is an optical fiber application sensor, the submarine optical cable is an optical fiber pair, and the sending means sends the wavelength light to one of the optical fiber pairs, Each of the wave means performs multiplexing on one of the optical fiber pairs, returns one of the optical fiber pairs to the other at the observed point at the farthest point, and passes the other of the optical fiber pairs through the land. It is characterized in that it is configured to send to a station.

Further, the land station includes a demultiplexing means for demultiplexing each wavelength light of the optical signal from the other of the optical fiber pair, and a detecting means for optically detecting each of the wavelength lights thus divided. It is characterized by having been provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will be described. Wavelength-division demultiplexing (WDM: Wavelength D) is performed by using light of different wavelengths assigned in advance to each observation point.
The light is transmitted to the submarine cable by an multiplex transmission method, and the wavelength light assigned to itself at each observation point is selectively branched and supplied to an optical fiber application sensor as a submarine observation sensor. Since the wavelength light is phase-modulated by the information to be observed by this sensor, this phase-modulated light is multiplexed and superimposed again on the submarine cable.

Then, the optical fiber is turned back inside the farthest point seabed observation device so that each wavelength light is returned to the land station through each observation device.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a ground station according to an embodiment of the present invention. In FIG. 1, the observation terminal station 1 has optical detectors 3A to 3C provided corresponding to the observation devices A to C (see FIG. 2) at the observation points on the sea floor, respectively.

Each of these photodetectors 3A to 3C has a wavelength λ1, λ2,
The optical signals λ1A, λ2B, and λ3C returned from the submarine optical cable 10 are heterodyne-optically detected by using λ3 (which are different from each other). These detection outputs are shown as observation outputs 11A to 11C.

The optical detectors 3A to 3C output the respective wavelength signals λ1 to λ.
3 is directly derived and sent to the next WDM transmission terminal station 2.
In the WDM transmission terminal 2, these wavelength optical signals λ1 to λ3
Optical multiplexer 4 for multiplexing and sending out to submarine optical cable 10
And the return wavelength optical signals λ1A and λ from the submarine cable 10.
And an optical demultiplexer 5 for demultiplexing 2B and λ3C.

The submarine optical cable 10 is a single optical fiber pair, and the observation devices A to A of each observation point on the seabed shown in FIG.
C are cascade-connected by this optical fiber pair.

More specifically, one of the optical fiber pairs 10 (down line) is connected to the second observation device B of the next stage via the optical demultiplexer 6A and the optical multiplexer 7A of the first observation device A. Has been introduced to.

The optical demultiplexer 6A selectively branches and extracts the optical signal of the wavelength λ1 assigned to the observation device A and supplies it to the sensor 8A. As the sensor 8A,
This sensor uses an optical fiber applied sensor. This optical fiber applied sensor mainly involves a phase change phenomenon of an optical signal due to expansion and contraction of an optical fiber and an optical signal caused by a change in a refractive index of an optical fiber core through a photoelastic effect. This utilizes a phase change phenomenon.

The optical signal whose phase has been changed (phase-modulated) through the sensor 8A is multiplexed by the optical multiplexer 7A as a wavelength λ1A and transmitted to the second observation device B at the next stage.

It is assumed that the second and third observation apparatuses B and C have the same configuration and the same operation. And
In the observation device C at the last stage (farthest point from the land station), the optical fiber pair is turned up at the turn-up unit 9 to become an up line,
The inside of each of the devices A to C is transmitted as it is to the land station in a through state.

Returning to FIG. 1 again, the return optical signal from the optical fiber pair 10 is (λ1A + λ2B + λ3C), and is thus demultiplexed by the optical demultiplexer 5 to λ1A, λ2B,
Separated into λ3C. These optical signals λ1A, λ2B, λ
3C is subjected to phase modulation by the respective sensors 8A, 8B, 8C. Therefore, the optical detectors 3A, 3B, and 3C optically heterodyne detect the original optical signal wavelengths λ1, λ2, and λ3, respectively, thereby detecting phase information (phase difference) and observing the output 11A, 11B of each observed point. , 11C are obtained.

Although only three observation points are shown in FIG. 2, this is for the sake of simplicity, and it goes without saying that four or more observation points may be used.

[0023]

According to the present invention, since the transmitted light signal from the terminal station installed on land can be observed simply by turning back, the submarine cable and the observation device do not need a power supply line. As the configuration in the observation device, since an electric circuit is unnecessary by using an optical demultiplexer and an optical multiplexer using an optical device, there is an effect that a highly reliable system configuration can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram of a land station according to an embodiment of the present invention.

FIG. 2 is a block diagram of an observation point on the seabed according to the embodiment of the present invention.

[Explanation of symbols]

 AC observation apparatus 1 observation terminal station 2 WDM transmission terminal station 3A-3C optical detector 4 optical multiplexer 5 optical demultiplexer 6A-6C optical demultiplexer 7A-7C optical multiplexer 8A-8C sensor 9 folding unit 10 Submarine cable

Claims (4)

[Claims] 1. A submarine observation system for performing submarine observation at a plurality of observation points by using a submarine optical cable, wherein wavelengths of different wavelengths pre-assigned to each of the observation points are wavelength-multiplexed. Then, sending means for sending to the submarine optical cable, branching means provided at each of the observed points, for selectively branching the wavelength light assigned to the observed point from the optical signal of the submarine optical cable, Sensor means provided at each of the observed points to modulate the phase information of the wavelength light branched by the branching means according to the observed information, and the sensor information provided at each of the observed points, the submarine optical cable The submarine observation system comprising: a multiplexing unit that multiplexes into the optical signal of. 2. The seabed observation system according to claim 1, wherein the sensor means is an optical fiber application sensor. 3. The submarine optical cable is an optical fiber pair, the sending means sends the wavelength light to one of the optical fiber pairs, and each of the multiplexing means connects to one of the optical fiber pairs. The optical fiber pair is folded back to the other at the observed point at the farthest point, and the other of the optical fiber pair is sent through to the land station through. The seabed observation system according to claim 1 or 2. 4. In the land station, a demultiplexing unit that demultiplexes each wavelength light of the optical signal from the other of the optical fiber pair, and a detection unit that photodetects each wavelength light that has been demultiplexed. The seabed observation system according to claim 3, wherein the seabed observation system is provided.