JP2536138B2 - Communication system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a communication system using an optical submarine cable, and is particularly suitable for use in a meeting when laying an optical submarine cable or repairing the cable. Related to a communication system.

[Conventional technology]

When laying an optical submarine cable used for optical communication or repairing an optical submarine cable that has already been laid, a meeting is generally held on land and at sea or between shores. The meeting is performed by transmitting and receiving a low frequency signal such as a voice signal using the installed optical submarine cable.

Transmission and reception of this low-frequency signal through an optical submarine cable requires processing such as encoding, decoding, pulse insertion and rearrangement. For this reason, a PC at both ends of the optical submarine cable
M (Pulse Code Modulation) It was necessary to install an optical communication terminal that transmits and receives general communication signals and a meeting communication device that is used exclusively for meeting communication. A low-frequency signal including a voice signal was sampled by a meeting communication device at, for example, 8 kHz, coded into a pulse train of 8 bits per sampling, and sent to the optical terminal device as a pulse train of 64 kb / s. The optical terminal equipment rearranges the pulse train of the general communication signal PCM-multiplexed and the output pulse train of the meeting communication device, converts this into an optical pulse signal and sends it to the optical submarine cable.

The optical pulse signal is regenerated and relayed by a repeater arranged in the middle of the optical submarine cable, and reaches the other terminal station device. The other terminal equipment converts the input optical pulse signal into an electrical signal, sends a general communication signal to a system other than the optical submarine cable system, extracts a 64 kb / s pulse train for a meeting, and sends it. The low-frequency signal was reproduced by decoding by the operation opposite to the encoding performed by the meeting communication device on the side. The low frequency signal reproduced in this manner was converted into an audible sound by a telephone or the like when it was a voice signal.

[Problems to be Solved by the Invention]

As described above, conventionally, when performing the meeting communication, the meeting communication device and the optical terminal device are required. The functions of the meeting communication device are summarized here as sampling, encoding and decoding, and the functions of the optical terminal equipment are pulse insertion, rearrangement and electro-optical conversion, all of which require advanced technology. To be done. Therefore, the installation, adjustment, operation and repair of such a device are complicated and require a lot of time, labor and skill, so that what is inevitably constructed as a portable device at present. It doesn't exist.

Thus, in the conventional meeting communication method, when the optical submarine cable is repaired, the meeting communication between the optical terminal equipment on land and the optical terminal equipment on the repair ship is ensured, and when the optical terminal equipment itself fails. From the viewpoints of securing temporary emergency communications, securing communications when laying optical submarine cables at a stage where the construction of optical terminal equipment is not completed, and securing communications using the system under test. It had the drawback of not being able to function.

Therefore, an object of the present invention is to provide a meeting communication system that enables easy meeting communication between land and sea or between land.

[Means for solving the problem]

The meeting communication system of the present invention comprises: (i) low-frequency signal generating means for generating a low-frequency signal in which information to be transmitted is represented by a change in amplitude, and frequency modulating means for frequency-modulating the low-frequency signal. (Ii) pulse forming means for converting the frequency-modulated signal into a pulse signal having a pulse width corresponding to the frequency, and (iii) a predetermined duty other than 50% which is sufficiently higher than the frequency of the pulse signal. A high-speed pulse signal generating means for generating a high-speed pulse signal having a ratio, (iv) a logical operation means for obtaining an exclusive OR between the high-speed pulse signal and the pulse signal, and (v) an output of this logical operation means. The transmitting side is provided with a transmitting means having an electro-optical converting means for converting a signal into an optical signal and transmitting the optical signal to the optical submarine cable. Then, information is transmitted according to a change in the duty ratio of the optical signal, and a meeting is held between the transmitting side and the receiving side.

That is, according to the meeting communication system of the present invention, the signal to be transmitted is frequency-modulated and then converted into a pulse signal having a pulse width corresponding to the frequency. Then, the exclusive OR is taken with a high-speed pulse signal having a sufficiently high frequency and a duty ratio other than 50%. Therefore, for example, if the duty ratio of the high-speed pulse signal is 25%, a signal with a duty ratio of 75% is output as the result of the logical operation while the pulse signal is at the high level, and a pulse signal is output while the pulse signal is at the low level. , A signal with a duty ratio of 25% is output. As described above, the present invention forms a high-speed pulse signal for transmitting information by changing the duty ratio, so that information can be directly transmitted to the optical submarine cable without using an optical terminal device.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 shows a configuration in which a transmitter and a receiver are connected to an optical submarine cable in a meeting communication system according to an embodiment of the present invention.

The transmitter 11 is connected to both ends of an optical fiber cable 17 in which an optical submarine repeater 15 is appropriately arranged together with the receiver 13.

The transmitter 11 includes a low-frequency signal oscillator 21 that generates a low-frequency signal 19, a frequency modulator 25 and a pulse forming circuit 27 that change the low-frequency signal 19 into a pulse signal 23 whose frequency changes. The pulse signal 23 is input to one terminal of the gate 29 having two input terminals, and the high speed pulse pattern signal 33 is input to the other terminal from the pulse pattern generator 31. The gate circuit 29 takes the exclusive OR of these input signals and supplies the output gate output signal 35 to the electro-optical converter 37. Further, the clock signal 39 from the pulse pattern generator 31 is converted into an electro-optical converter.
Supplied directly to 37.

The electro-optical converter 37 converts the electric signal into an optical signal and sends the optical digital signal 41 to the optical submarine cable 17 as an output signal from the transmitter 11.

The receiving device 13 includes an optical submarine cable 17 and an optical-electrical converter (O / E) 45 that receives the optical digital signal 41 propagating through the optical submarine repeater 15 and converts it into an electric signal. Receiver 13
Further comprises a filter 47 and a frequency demodulator 49, which reproduces the low frequency signal and outputs it as a low frequency demodulated signal 51. The low-frequency demodulated signal 51 is supplied to the signal regenerator 53 and converted into a signal form according to the application.

FIG. 2 shows the output waveform of each component of the meeting communication device. The operation of the meeting communication device described above will be described with reference to FIG.

When meeting communication is required, without using the optical terminal equipment,
The transmitter 11 and the receiver are directly connected to the optical submarine cable 17.

From the low-frequency generator 21, a low-frequency signal 19 (a in FIG. 2a), which represents information such as voice to be transmitted, is represented by a change in amplitude.
Occurs. The low frequency signal 19 is input to the frequency modulator 25. As a result, the amplitude of the low frequency signal 19 changes in frequency as shown in FIG. 2b. In this embodiment, the carrier frequency for frequency modulation is not specified and is arbitrary. The FM modulation signals 5 and 5 output from the frequency modulator 25 are pulse signals 23 having a pulse width corresponding to the frequency.
(FIG. 2c) can be changed by the pulse forming circuit 27.

As it is, the pulse signal 23 is not relayed through this optical submarine cable and cannot reach the receiving device 13. That is, for example, a high frequency carrier wave of about several megabits is required. As a carrier wave, a high-speed pulse pattern signal 33 (FIG. 2d) is output from the pulse pattern generator 31 as a high frequency pulse signal, and is input to one terminal of the gate circuit 29. The gate circuit 29 takes the exclusive OR with the pulse signal 23 input to the other terminal, modulates the high speed pulse pattern signal 33, and outputs the gate output signal 35 (FIG. 2e).

The high speed pulse pattern signal 33 may be either a random signal or a fixed pattern signal. However,
Since the gate circuit 29 performs the modulation that takes the exclusive OR, the following conditions are necessary. That is, for the random signal, the mark ratio indicating the probability of occurrence of the signal "1" among the levels of the signals "0" and "1" is set to less than 1/2, for example, 1/4 or 1/8. The fixed pattern signal has a duty ratio of less than 50%,
For example, set it to 25% or 10%.

FIG. 3 shows the input signal 23 of the gate circuit 29 shown in FIG.
33 and a part of the output signal 35 are shown in detail.

FIG. 3d is a specific example of FIG. 2d and shows a high-speed pulse pattern signal 33 input to one side of the gate circuit 29.
It shows the waveform of. In FIG. 3d, the duty ratio M
Is indicated by A / B. FIG. 3c is a specific example of FIG. 2c and shows the waveform of the pulse signal 23 input to the other input terminal of the gate circuit 29. Pulse signal
23 is an FM modulation signal 55 that is frequency-modulated by the frequency converter 25.
The pulse width C is a signal that is converted every moment.

FIG. 3e shows an output waveform when the gate circuit 29 takes the exclusive OR of the waveforms shown in FIG. 3d and FIG. 3c, and embodies the gate output signal 35 (FIG. 2e). Is. As shown in this figure, in the section C in which the pulse is output in FIG. 3c, the mark ratio or duty ratio K is reversed as compared with the waveform in FIG. 3d. That is, the duty ratio K of the gate output signal 35 has a value of 1-M. Except for the section C, the same value as that of the waveform in FIG. 3D, that is, the duty ratio K of the high speed pulse pattern signal 35 is equal to the duty ratio M of the high speed pulse pattern signal 33.

Thus, the amplitude of the low frequency signal 19 output from the low frequency generator 21 is represented by the frequency change by the frequency modulator 25. The pulse forming circuit 27 represents the change in pulse width, and the gate circuit represents the change in mark ratio or the change in duty ratio. After being converted in this way, the gate output signal 35 is input to the electro-optical converter 37. Gate signal output 35 input to electro-optical converter 37
Is converted into an optical digital signal 41 together with the clock signal 39, and is output to the optical submarine cable 17 as an output signal of the transmitter 11.

The optical digital signal 41 is regenerated and relayed by the optical submarine repeater 15 appropriately arranged in the optical submarine cable 17 and supplied to the receiving device 13. In the optical regenerator 15, after converting the optical digital signal 41 into an electric signal, equivalent amplification, retiming and identification reproduction by the clock signal 39 are performed,
After that, it is converted into an optical signal again. Note that the reproduction of the optical digital signal 41 does not necessarily have to perform all of the equivalent amplification, retiming, and identification reproduction, and in some cases, equivalent amplification and identification reproduction, or only equivalent amplification may be performed.

Receiver via optical submarine cable 17 and optical regenerator 15.
The optical digital signal 41 reaching 13 is converted again into an electric signal (Fig. 2e) by the photoelectric converter 45. Since the converted electric signal contains the frequency component of the pulse signal 23 of the transmitter 11, the frequency component is extracted by passing through the filter 47 to obtain the signal having the waveform shown in FIG. 2B. The signal that has passed through the filter 47 is demodulated by the frequency demodulator 49 while timing is adjusted by the clock signal 46, and the low frequency demodulated signal 51 (FIG. 2f) obtained by reproducing the low frequency signal 19 is obtained. The low frequency demodulated signal 51 is further converted by the signal regenerator 53 into a signal form according to the application. For example, if the low frequency generator 21 is a telephone transmitter for converting a voice signal into an electric signal, the signal regenerator 53 is composed of a speaker and a receiver, and the low frequency demodulated signal 51 is converted into an audible sound.

〔The invention's effect〕

As described above, according to the present invention, a change in the amplitude of a low-frequency signal to be transmitted is frequency-modulated and then converted into a pulse signal having a pulse width corresponding to the frequency, and this signal and a frequency sufficiently higher than this signal are generated. A signal that is exclusive ORed with a high-speed pulse signal with a duty ratio other than 50% is sent. As a result, the frequency of the optical signal transmitted through the optical submarine cable becomes the same constant frequency as the high-speed pulse signal, and information is transmitted due to the change in the duty ratio.
Therefore, even if a transmission device such as a repeater capable of transmitting only an optical signal having a constant frequency is provided in the middle of the optical submarine cable, information can be properly transmitted. Also, because a simple meeting communication device was configured without using a terminal device or a meeting communication device, a meeting between a land-based optical terminal device and an optical terminal device on a repair ship when repairing an optical submarine cable Communication, temporary emergency communication when the optical terminal equipment itself fails, communication when laying an optical submarine cable at the stage where the construction of the optical terminal equipment is incomplete, communication using the system under test Can be easily secured. Further, the meeting communication device of the present invention can be easily configured not only by using a commercially available measuring instrument or the like, but also can be easily installed and used.

[Brief description of drawings]

The drawings are for explaining one embodiment of the present invention.
Of these, FIG. 1 is a configuration diagram of a transmitting device and a receiving device connected to an optical submarine cable, FIG. 2 is a waveform diagram showing output signal waveforms of respective components of the meeting communication system, and FIG.
It is a wave form diagram which showed a part of figure in detail. 11 …… Transmitter, 13 …… Receiver, 21 …… Low frequency generator, 25 …… Frequency modulator, 27 …… Pulse forming circuit, 29 …… Gate circuit, 31 …… Pulse pattern generator, 37… … Electro-optical converter, 45 …… Optical-electric converter, 47 …… Filter, 49 …… Frequency demodulator, 53 …… Signal regenerator.

Claims (1)

(57) [Claims] 1. A low-frequency signal generating means for generating a low-frequency signal whose information to be transmitted is represented by a change in amplitude, a frequency modulating means for frequency-modulating this low-frequency signal, and a signal after this frequency modulation. Forming means for converting the pulse signal to a pulse signal having a pulse width corresponding to the frequency, and a high-speed pulse signal generation for generating a high-speed pulse signal having a frequency sufficiently higher than the frequency of the pulse signal and having a predetermined duty ratio other than 50% Means, a logical operation means for taking an exclusive OR between the high-speed pulse signal and the pulse signal, and an electro-optical conversion means for converting a signal output from the logical operation means into an optical signal and sending it to an optical submarine cable. A meeting communication system in which a transmitting means including the above is provided on the transmitting side, information is transmitted according to a change in the duty ratio of an optical signal, and a meeting is held between the transmitting side and the receiving side.