JP2001144729A - Composite transmission system by wavelength multiplexing and frequency multiplexing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously transmit a signal such as a video signal from many places multiplexing the transmission signal and also to perform long distance transmission over a wide area in a composite transmission system by wavelength multiplexing and frequency multiplexing. SOLUTION: This system is provided with a plurality of frequency multiplex transmitting devices 121 which are respectively arranged in each of a plurality of areas (A area to N area), wavelength division multiplex transmitting devices 12A to 12N which are arranged in each of the plurality of areas (A area to N area), convert frequency multiplexing signals transmitted from the devices 121 in the areas into optical signals of wavelengths that are respectively different in each area, perform wavelength multiplexing the optical signals to a common optical fiber cable 13 and transmit the optical signals to a central station, and a wavelength division multiplex and frequency multiplex transmitting device 111 which is arranged at the central station, divides the optical signals transmitted via the cable 13 into optical signals of each wavelength and further divides the optical signals of each wavelength into electric signals of each carrier frequency to receive the optical signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite transmission system using wavelength division multiplexing and frequency division multiplexing, and more particularly, to monitoring of traffic volume at a large number of points over a wide area such as roads, railroads, tunnels, etc. The present invention relates to a composite transmission system using wavelength division multiplexing and frequency division multiplexing for centralized monitoring using video.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing an example of a conventional transmission system using time division multiplex transmission. The figure shows time division multiplexing (T
DM) shows a video signal transmission system using a transmission device, and converts an original video signal (NTSC color TV signal) photographed by a plurality of television cameras 61 _{1 to} 61 _n into a video switching device (V
-SW) 62, the selected video signal is encoded and encoded by an encoding device (such as a CODEC) 63, time-division-multiplexed by a time-division multiplexing (TDM) transmission device 64, and distant time-division multiplexing (TDM). TDM) transmission device 65, and the time-division multiplexing (TDM) transmission device 65 on the receiving side separates the received time-division multiplexed signal to a decoding device (DECO).
DER) 66 and output to a decoding device (DECODER).
A video signal 66 is decompressed and decoded to convert the compressed and coded video signal into an original video signal.
And the monitor device 67 displays the original video.

[0003] In order to transmit an original video signal at the same level as a normal television image, when compression is performed by the MPEG2 method, a band of at least 6 Mbit / s is occupied. Therefore, when transmitting a large number of images at the same time, time-division multiplexing (TDM) with a wide band bit rate is performed according to the number of images.
Transmission equipment must be used.

[0004] If a wideband time division multiplexing (TDM) transmission device is used, the entire system becomes expensive. Therefore, in the case of a system in which it is not necessary to constantly monitor images of all grounds,
As shown in FIG. 6, a video switching device (V-SW) 62 is used to periodically switch and input the video signals of the television cameras 61 _{1 to} 61 _n , and reduce the video to be transmitted simultaneously to a small number of lines. If it is necessary to reduce the number of necessary transmission lines, or conversely, if it is necessary to constantly monitor a large number of images on the ground, it is necessary to add a higher-order group transmission device in order to increase the required number of transmission lines. Had been

FIG. 7 is a diagram showing an example of a conventional transmission system using frequency multiplex transmission. This figure shows an example of a configuration for monitoring images of cameras installed in a plurality of monitored stations (stations B to D) 72 _{B to} 72 _D from a monitoring station (station A) 71.

Each monitored station (stations B to D) 72 _{B to} 72
In _D, the signal (NTSC color TV signal) of the original image taken by the TV camera 72 _first frequency modulator 72 ₂
Entered, the carriers of different frequencies f ₁ ~f ₃ each frequency modulator 72 ₂ per the monitored station and the frequency-modulated by a video signal, an electric light (E / O) converter 72 ₃ optical frequency modulation signal And converts the optical signal into an optical coupler 72 ₄
And transmits it to the monitor station (station A) 71.

That is, each monitored station (stations B to D) 72 _B
To 72 _D converts the image signals having different carrier frequencies respectively to the optical signal of the same wavelength, coupled to a common optical fiber transmission cable by the optical coupler 72 ₄ monitor station (A station)
Transmit to 71.

In the monitor station (station A) 71, the transmitted light
The signal is converted to a photoelectric (O / E) converter 71 ₁To electrical signals
After the conversion, the frequency separation circuit 71_TwoTo each monitored station (B
Station to D station) frequency separation circuit
71_ThreeMonitor device 71 by appropriately selecting a frequency band according to
_FourTo display the original video.

When transmitting a frequency multiplexed signal through an optical fiber using an optical signal having the same wavelength, a monitor station (station A) 7 is required.
The transmission distance between 1 and each of the monitored stations (stations B to D) 72 _{B to} 72 _D is limited to about 10 km to 20 km due to the effects of mode dispersion and the like due to the number of frequency multiplexing and the characteristics of the optical coupler and the like. It is not suitable for a wide-area transmission system beyond that.

[0010]

The transmission system based on the time division multiplex transmission shown in FIG. 6 is capable of long distance transmission exceeding about 20 km. It is necessary to periodically switch and transmit the video signal of the television camera using the switching device, or to add a transmission device of a higher order group.

The single-wavelength optical transmission system using frequency multiplex transmission shown in FIG. 7 can transmit a large number of images by using different carrier frequencies, but the transmission frequency band is expanded. As a result, the transmittable distance is shortened due to the influence of the dispersion characteristics of light and the like, which is unsuitable for a long-distance transmission system over a wide area.

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite transmission system using wavelength division multiplexing and frequency division multiplexing, which multiplexes transmission signals from a number of points and simultaneously transmits the signals, and is capable of long-distance transmission over a wide area. And

[0013]

In order to solve the above-mentioned problems, a composite transmission system using wavelength division multiplexing and frequency division multiplexing of the present invention (1) is arranged in a plurality of regions, and transmits transmission signals using different carrier frequencies. A plurality of frequency multiplex transmission apparatuses that transmit by frequency multiplexing, and are installed in each of the plurality of regions, and frequency multiplex signals transmitted from the plurality of frequency multiplex transmission devices in the region are different for each region. A wavelength division multiplex transmission device that converts the wavelength into an optical signal, multiplexes the wavelength into a common optical fiber cable and transmits the multiplexed signal to a central office, and is installed in the central office and passes through the optical fiber cable from the wavelength division multiplex transmission device. The wavelength division multiplexing and frequency division of the optical signal transmitted and separated into the optical signal of each wavelength, the optical signal of each wavelength separated into the electric signal of each carrier frequency and received. A heavy transmission device, in which with a.

[0014] (2) The frequency multiplex transmission apparatus arranged in each area has a configuration for transmitting a video signal output from a television camera at a different carrier frequency for each frequency multiplex transmission apparatus. The wavelength division multiplexing and frequency multiplexing transmission device installed in the central office has a configuration in which a video signal separated and extracted for each wavelength and each carrier frequency from a received optical signal is displayed on a monitor device.

(3) The wavelength division multiplexing and frequency multiplexing transmission equipment installed in the central office is provided with a wavelength demultiplexing unit for demultiplexing a received optical signal into an optical signal for each wavelength, and demultiplexed by the wavelength demultiplexing unit. A wavelength selector for selecting a part of the optical signal from the optical signals, an optical-electrical converter for converting the optical signal selected by the wavelength selector to an electric signal, and a signal converted by the optical-electrical converter. A frequency separation unit that separates an electric signal into a video signal for each carrier frequency, a frequency selection unit that selects a part of the video signal from the video signals separated by the frequency separation unit, and a selection unit that selects the video signal. Means for outputting the video signal to the monitor device, a selection control unit for controlling selection in the wavelength selection unit and the frequency selection unit,
It is provided with.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
FIG. 2 is an explanatory diagram of a complex transmission system using number multiplexing. In the figure
Then, 11₁Is the wavelength division multiplexing of the central station (monitor station)
(WDM: Wavelength Division Multiplex) and frequency
Number multiplex transmission device, 11_Two, 11_ThreeIs the central station (monitor station)
Monitoring device, 11_FourIs the monitor selection of the central station (monitor station)
Control unit, 12_A, 12_B, ..., 12_NIs the object to be monitored
Division multiplexing installed in each area (A-N)
(WDM) transmission device, 12₁Is a frequency multiplex transmission device, 1
2 _TwoIs a television camera.

Waves installed in each area (A to N)
Long division multiplexing (WDM) transmission device 12 _A, 12_B, ..., 1
2_NAre different wavelengths λ_A, Λ_B, ... λ_NKoshin
Signal transmission signal using optical coupler
Transmit to cable 13, wavelength division of central station (monitor station)
Multiplexing (WDM) and frequency multiplex transmission device 11₁Send to
You.

Further, each wavelength division multiplexing (WDM) transmission device
12_A, 12_B, ..., 12_NHave different transport
Multiple frequency multiplex transmission equipment for transmitting video signals by frequency
12 ₁Is input. Each frequency multiplex transmission
Device 12₁Has a TV set at the point to be monitored
Camera 12_TwoIs input.

The wavelength division multiplexing (WD) of the central station (monitor station)
M) and frequency multiplexing transmission apparatus 11 _1, each wavelength division multiplexed installed in each region (WDM) transmission apparatus 12 _A, 1
2 _B, ..., 12 from the transmission signal of the transmission wavelength multiplexing and frequency multiplexing of _N, select the monitor selection controller 11 ₄ wavelength and a signal of the carrier frequency, including a video signal to be monitored, the selected video signal To the monitoring device 11 ₂ , 1
To display in the 1 _3.

FIG. 2 is an explanatory diagram of a wavelength division multiplexing (WDM) transmission device installed in each region. Wavelength division multiplexing (W
The DM) device is also used for the first-class communication business, and divides an optical wavelength into a maximum of 32 waves, and transmits a maximum of 32 to a single optical fiber.
A light wave of a wave is assigned and transmitted as a communication wave.

Now, in each of the regions A, B,..., N, the station A wavelength division multiplexing (WDM) transmission device 20 _A , the station B wavelength division multiplexing (WDM) transmission device 20 _B ,. It is assumed that a multiplex (WDM) transmission device _20N is installed.

Each of the wavelength division multiplexing (WDM) transmission devices 20 _{A to} 20 _N includes a wavelength conversion unit 21, a level adjustment unit 22, an optical output unit 23, an optical coupler 24, and a level monitor 25.

The wavelength converter 21 divides the wavelength of the optical signal received from the subordinate frequency multiplex transmission apparatus into each wavelength division multiplex (W
DM) is converted into an optical signal transmission device 20 _A to 20 _N per different wavelengths (up to 32 waves). The output level of the optical signal output from the wavelength conversion unit 21 is adjusted by the level adjustment unit 22 and is input to the optical output unit 23.

The level monitor 25 monitors the output level of the optical signal output from the optical output section 23 and controls the level adjustment section 22 to adjust the output level. Light output unit 2
The optical signal output from the third station is wavelength division multiplexed at station A (WD
From M) transmission apparatus 20 _A as a wavelength lambda _N from wavelength lambda _A, B station Wavelength division multiplexing (WDM) wavelength from the transmission device 20 _B λ _B, N stations wavelength division multiplexing (WDM) transmission apparatus 20 _N is Optical couplers 24 as optical signals of different wavelengths, respectively.
Is output to The optical coupler 24 sends an optical signal output from the optical output unit 23 to a single mode optical fiber cable.

FIG. 3 is an explanatory diagram of a frequency multiplex transmission device arranged in each area. A plurality of frequency multiplex transmission apparatuses 30 _a , 30 _b , 30 _c,.
n are allocated as monitored stations (stations a to n).

The frequency multiplexing transmission devices 30 _a , 30 _b , 30 _c ,..., 30 _n of the monitored stations (stations a to n) respectively transmit the original video signals (N
TSC color TV signal) to the frequency modulator 32,
The frequency modulator 32 frequency-modulates a carrier having a different frequency f _{1 to} f _n for each monitored station by a video signal,
The electro-optical (E / O) converter 33 converts the frequency-modulated electric signal into an optical signal, couples the optical signal to one optical fiber transmission cable 35 by an optical coupler 34, and connects the optical signal to the optical fiber transmission cable 35. The signal is transmitted to the wavelength division multiplexing (WDM) transmission device of the connected upper station.

Each of the monitored stations (stations a to n) transmits video signals having different carrier frequencies to the same wavelength (“α” in FIG. 3).
Wavelength ". ), Is coupled to an optical fiber transmission cable 35 by an optical coupler 34, and is transmitted to a wavelength division multiplexing (WDM) transmission device.

When a frequency-division multiplexed signal is transmitted by an optical signal having the same wavelength, as described above, the limit distance at which transmission is possible is about 10 km to 20 km due to the influence of light dispersion and the like. The transmission distance between the transmission apparatus and each of the monitored stations (stations a to n) must be less than or equal to the limit distance, but the wavelength division multiplexing (WDM) transmission apparatuses of the upper station have different wavelengths. , Each wavelength division multiplexing (WDM) transmission device, for each optical signal of each wavelength, according to the distance to the central office,
Also, by adjusting the output level so that the level does not fluctuate due to the characteristics of the optical coupler, etc., wavelength division multiplexing (WD)
M) Transmission up to about 80 km is possible between the transmission device and the central office.

FIG. 4 is an explanatory diagram of a wavelength division multiplexing (WDM) and frequency multiplexing transmission apparatus of a central station (monitor station) according to the present invention. The wavelength division multiplexing (WDM) and frequency multiplexing transmission device 40 transmits a wavelength division multiplexing (WDM) and frequency multiplexing transmission signal transmitted from a wavelength division multiplexing (WDM) transmission device installed in each region via a single mode optical fiber cable. Is received by an optical receiving unit 41, separated into optical signals of respective wavelengths by a wavelength separating unit 42, and an optical signal including a video signal to be appropriately monitored is selected by a wavelength selecting unit 43, and the optical signal (O / E ) is converted into an electrical signal by the conversion unit 44 separates the frequency-multiplexed signal by frequency separation unit 45 selects the frequency of the monitored video signal by the frequency selector 46, and displays on the monitor device 47 _1, 47 _2. In addition,
The wavelength selection unit 43 and the frequency selection unit 46 include a selection control unit 48 that operates according to a command from the monitor selection control device 49.
Is controlled by

FIG. 5 is an explanatory diagram of a selection operation screen in the monitor selection control device of the present invention. In the central station (monitor station), as shown in FIG. 5, the names of the points to be monitored specified by the combination of the optical signal wavelength corresponding to the area and the carrier frequency corresponding to the monitored station in each area are arranged in a matrix. Is displayed on the monitor selection control device, and the monitor specifies the monitored target point names arranged in the matrix, and the monitor selection control device 49 causes the light corresponding to the monitored target point name to be displayed. The selection control unit 48 is notified of the signal wavelength and the carrier frequency, and the selection control unit 48
And controlling the frequency selector 46 to select and output the video signal of the optical signal wavelength and the carrier frequency.

The above-mentioned screen in which the names of the monitored points are arranged in a matrix is displayed on a display device. By clicking on the square of the monitored point name to be monitored on the screen, the monitored points are displayed. Can be arbitrarily and easily specified, and a name, a symbol, and the like can be arbitrarily input to each square portion of the matrix so as to easily identify the monitored target point.

Further, based on the composite transmission system using wavelength division multiplexing and frequency division multiplexing of the present invention, transmission of not only video signals but also monitoring / warning signals by detection of various sensors is added as an optional function to prevent crime. A wide-area monitoring system applicable to various fields of use such as disaster prevention and disaster prevention can be constructed.

[0033]

As described above, according to the present invention,
A plurality of transmission signals such as video signals are collectively transmitted for each region by frequency multiplexing to a wavelength division multiplexing (WDM) transmission device, and the wavelength division multiplexing (WDM) transmission device for each region is used for wavelength division multiplexing in other regions. It is possible to collect and transmit a large number of transmission signals over a wide area by converting them into optical signals of different wavelengths and transmitting the transmission signals to the central station so that the wavelengths do not overlap with each other with the multiplex (WDM) transmission device. ,
A transmission network for a wide range of video signals and the like can be constructed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a composite transmission system based on wavelength division multiplexing and frequency division multiplexing of the present invention.

FIG. 2 is an explanatory diagram of a wavelength division multiplexing (WDM) transmission device of the present invention.

FIG. 3 is an explanatory diagram of a frequency multiplex transmission device of the present invention.

FIG. 4 is an explanatory diagram of a wavelength division multiplexing (WDM) and frequency multiplexing transmission device of a central office according to the present invention.

FIG. 5 is an explanatory diagram of a selection operation screen in the monitor selection control device of the present invention.

FIG. 6 is a diagram illustrating an example of a conventional transmission system using time division multiplex transmission.

FIG. 7 is a diagram illustrating an example of a transmission system using conventional frequency multiplex transmission.

[Explanation of symbols]

11 ₁ Wavelength division multiplexing and frequency multiplexing transmission equipment at the central office 11 ₂ , 11 ₃ Monitoring equipment at the central office 11 ₄ Monitor selection control equipment at the central office 12 _A , 12 _B ,..., 12 _N Wavelength division installed in each region Multiplex transmission device 12 ₁ Frequency multiplex transmission device 12 ₂ TV camera

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K002 AA01 AA03 BA04 BA05 CA09 DA02 DA10 EA05 FA01 GA01 5K022 AA00

Claims (3)

[Claims] 1. A plurality of frequency multiplex transmission devices arranged in each of a plurality of regions and transmitting frequency-multiplexed transmission signals using different carrier frequencies, and installed in each of the plurality of regions, A frequency multiplexed signal transmitted from a plurality of frequency multiplexing transmission devices,
A wavelength division multiplexing transmission device that converts to an optical signal of a different wavelength for each region, multiplexes the wavelength into a common optical fiber cable, and transmits the multiplexed signal to the central office, Wavelength division multiplexing and frequency multiplexing for separating an optical signal transmitted via the optical fiber cable into optical signals for each wavelength, and separating and receiving the optical signal for each wavelength into an electric signal for each carrier frequency; A composite transmission system using wavelength division multiplexing and frequency division multiplexing, comprising: a transmission device; 2. The frequency multiplex transmission device arranged in each area has a configuration for transmitting a video signal output from a television camera at a different carrier frequency for each frequency multiplex transmission device. The installed wavelength division multiplexing and frequency multiplexing transmission device is provided with a configuration for displaying on a monitor device a video signal separated and extracted for each wavelength and each carrier frequency from a received optical signal. 3. A composite transmission system using wavelength division multiplexing and frequency division multiplexing. 3. A wavelength division multiplexing and frequency multiplexing transmission device installed in the central office, comprising: a wavelength demultiplexing unit for demultiplexing a received optical signal into an optical signal for each wavelength; and an optical signal demultiplexed by the wavelength demultiplexing unit. A wavelength selecting unit that selects a part of the optical signals, a photoelectric converting unit that converts the optical signal selected by the wavelength selecting unit into an electric signal, and an electric signal that is converted by the photoelectric converting unit. A frequency separation unit that separates the video signal into video signals for each carrier frequency, a frequency selection unit that selects a part of the video signal from the video signals separated by the frequency separation unit, and a frequency selection unit that is selected by the frequency selection unit. The composite device according to claim 2, further comprising: a unit that outputs a video signal to a monitor device; and a selection control unit that controls selection in the wavelength selection unit and the frequency selection unit. transmission system.