JPH0548636A - Optical communication system - Google Patents

Abstract

(57) [Abstract] [Purpose] Easy bi-directional communication between upstream and downstream, high transmission speed, long transmission distance, increased number of accommodated subscribers, low cost, and easy implementation An optical communication system having a small size is provided. [Structure] In the downlink, each of a plurality of transmission ends in a station device is branched and connected to each reception end of a plurality of terminal devices by an optical communication path via a star coupler provided corresponding to each transmission end. In the uplink, each of the plurality of receiving ends of the station device is branched and connected by an optical communication path to each transmitting end of the plurality of terminal devices via a star coupler provided corresponding to each receiving end.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system used for optical communication using an optical fiber. More specifically, the present invention relates to one station device and a plurality of terminal devices for downlink transmission of a signal from the station device to the terminal device and uplink transmission of a signal from the terminal device to the station device. The present invention relates to an optical communication system in which two optical communication networks for communication are used to perform bidirectional communication.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a downlink of a conventional optical communication system, and FIG. 8 is a block diagram showing an uplink of the same. In these figures, SR is a station device, TD is a time division multiplexer, LA is a laser, Sd is an optical star coupler for downlink, Su is an optical star coupler for uplink, and L is an optical star coupler for upstream.
R is a light receiving element, TR is a time division demultiplexer, T1 to Tn
Is a terminal device.

In this conventional optical communication system, a downlink star coupler Sd and an optical fiber are provided between a transmitting end of one station SR and receiving ends of a plurality of terminal devices T1 to Tn. An optical communication network for lines is provided, and an up-link star coupler S is provided between each transmission end of the plurality of terminal devices T1 to Tn and the reception end of the one station device SR.
An upstream optical communication network connected by u and an optical fiber is provided.

The down-link star coupler Sd distributes a signal arriving at its input to a plurality of n outputs, and a signal equal to all outputs is sent out. Therefore, when one terminal device is selected as the station device SR for communication,
The destination code with the identification code of the terminal device is transmitted, and the terminal device side identifies whether the signal is addressed to the own station by the destination code. When a plurality of terminal devices and the station device simultaneously communicate with each other, the station device SR performs time division multiplexing.

The upstream star coupler Su collects the signals arriving at a plurality of n inputs into one and outputs it. Therefore, each terminal device transmits a source signal to which its own station identification code is attached, so that the station device SR can identify the source. When a plurality of terminal devices and a station device simultaneously communicate with each other, optical signals are sent from the plurality of terminal devices so that the output of the star coupler Su is time division multiplexed.

[0006]

The above-mentioned conventional system is an excellent system capable of simply carrying out upstream and downstream bidirectional communication. However, in the conventional system, when a wideband digital signal of 150 Mb / s is simultaneously communicated between 16 terminal devices and one station device, the station device time-division-multiplexes the downlink signal and sends the uplink signal. Optical signals are transmitted from a plurality of terminal devices so as to be time division multiplexed at the output of the star coupler Su. At this time, the time-division multiplexed bit rate is 150 Mb / s × 16 =
It will be 2.4 Gb / s. 2.4G if more than 16
The transmission rate is higher than b / s, which is difficult with the current technology. In addition, since the transmission speed increases as the number of wideband digital signals to be multiplexed increases by time division multiplexing, the possible transmission distance becomes shorter, or the number of optical star coupler branches, that is, subscribers that can be accommodated. The number will decrease.

Further, as the transmission speed increases, the cost of optical devices and integrated circuits increases. Moreover, power consumption increases as the transmission speed increases. Then, as the transmission speed becomes higher, the size of mounting becomes larger. There were the above problems.

The present invention is an improvement of the above, in which it is possible to easily carry out upstream and downstream bidirectional communications, and since the transmission speed does not increase because time division multiplexing is not performed, the possible transmission distance can be increased. An object of the present invention is to provide an optical communication system which can increase the number of subscribers that can be accommodated, can reduce the cost of optical elements and integrated circuits, can reduce power consumption, and can reduce the mounting size.

[0009]

To achieve the above object, according to the present invention, in an optical communication system, each of a plurality of transmission ends in a station device has a downlink star coupler provided corresponding to each transmission end. Via the optical communication path to each receiving end of the plurality of terminal devices, each of the plurality of receiving end in the station device, through the upstream star coupler provided for each receiving end, a plurality of An optical communication path is provided for branch connection to each transmitting end of the terminal device.

Then, the station device selects an empty transmitting end which is not transmitting, and simultaneously transmits a down signal to each receiving end of a plurality of terminal devices through an optical communication path through a star coupler for a down line corresponding to the transmitting end. Is provided with a transmission means for transmitting
Each of the plurality of terminal devices is provided with a selective receiving means for selecting and receiving a downlink signal for its own terminal from its own receiving end.

Further, each of the plurality of terminal devices is provided with a selective transmission means for transmitting an upstream signal by selecting a terminal device side transmission end that can communicate with a vacant station device side reception end that is not in communication. The station device is provided with receiving means for simultaneously receiving an upstream signal by a plurality of receiving ends.

[0012]

In the present invention, the optical communication network connecting the station device and the plurality of terminal devices by the star coupler is upstream and downstream, and the plurality of optical communication networks are parallel. Select an empty (not in communication) optical communication network from the optical communication networks in parallel.
Each line between the station device and the terminal device is set. Therefore, even if the number of terminal devices increases and the number of line settings increases, the transmission speed does not increase.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 3 are block diagrams showing a downlink portion in an embodiment of the present invention. That is, FIG. 1 shows a station device part therein, FIG. 2 shows an optical star coupler box part, and FIG. 3 shows a terminal device part, respectively, and FIG. 1 and FIG. 2, FIG. 2 and FIG. By connecting, the entire downlink part is shown.

Similarly, FIGS. 4 to 6 are block diagrams showing the uplink portion in one embodiment of the present invention. That is, FIG. 4 shows the station equipment portion therein, FIG. 5 shows the optical star coupler box portion, and FIG. 6 shows the terminal equipment portion, respectively, and FIG. 4 and FIG. 5, FIG. 5 and FIG. By connecting, the entire uplink part is shown.

1 to 3 and FIGS. 4 to 6 show an embodiment of the present invention of an optical communication system composed of an upstream and downstream bidirectional optical communication network. First, Fig. 1
The downlink will be described with reference to FIG. This communication system includes one station device 56 and a plurality of terminal devices 24 to 27, and lasers 10 to 12 which are transmitting ends of the station device 56 and light receiving elements 28 to 30 which are receiving ends of the terminal devices 24 to 27.
A plurality of downlink optical communication networks (here, three) are provided between 32 to 34 and 40 to 42, which are connected to the downlink optical star couplers 16 to 18 and optical fibers.

1 to 3, it appears that there are four downlink optical communication networks, but one of them, namely,
Laser 13, optical star coupler 19, light receiving element 31, 3
The optical transmission line composed of 5, 39 and 43 is for transmitting a control signal for controlling the space division switches 44 to 47 and will be described in detail later.

In the station device 56, the control circuit 5 simultaneously selects the transmission ends (lasers 10 to 12) which are vacant (not transmitting) a plurality of transmission signals to the terminal devices 24 to 27. It is equipped with a means for transmitting. Here, although there are a total of four terminal devices 24 to 27, the transmission end (laser) of the station device 56 is reduced to three, assuming that it is rare that four terminals want to communicate at the same time. Ie 3 at the same time
Can only communicate with one terminal device. However, if it is statistically sufficient to talk at the same time with three terminal devices at almost all times, the number of lasers can be reduced and the size of the station device 56 can be reduced by doing so. In this way, the station device 5
By reducing the number of transmission terminals (lasers) of 6 from the number of terminal devices, it is possible to set up a line without accommodating a large number of terminal devices (statistically most of the time). The station device can be made smaller.

Further, in the terminal device 24, a desired receiving signal (a signal of a partner with whom communication is desired) desired from a plurality of receiving ends (light receiving elements) 28 to 30 is selected by the space division switch 44 to obtain a wide band signal 52. Similarly, the terminal devices 25 to 27 have a plurality of receiving ends (light receiving elements) 32 to 34, 36 to.
38, 40-42, the desired reception signal (the signal of the other party to communicate with) is selected by the space division switches 45-47 to obtain wideband signals 53-55. Space division switch 4
4 to 47 are sent from the control circuit 5 of the station device by the laser 13, and the optical star coupler 19 sends them to the terminal devices 24 to 2.
The light receiving elements 31, 35, 39, 43 of No. 7 are controlled by control signals coming to the control circuits 48, 49, 50, 51. Since this control signal has a low bit rate of about 64 Kb / s for each terminal device, it is easy to time-division-multiplex the control signals of a plurality of terminal devices. Controls the space division switch of the device.

Next, the uplink will be described with reference to FIGS. This communication system includes one station device 56 and a plurality of terminal devices 24 to 27. Light receiving elements 69 to 71 which are receiving ends of the station device 56 and lasers 80 to 91 which are transmitting ends of the terminal devices 24 to 27. Upstream optical star coupler 7
3 to 75 and a plurality of uplink optical communication networks (here, three) connected by optical fibers are provided. here,
1 to 3 and 4 to 6 together form an optical communication system capable of one-way communication, and the station device 56, the star coupler box 15, and the terminal devices 24 to 26 are shown in FIGS. It is written separately in FIG. 3 and FIG. 4 to FIG.

Further, the terminal device 24 is selected from the lasers 80 to 82 corresponding to the receiving ends (light receiving elements 69 to 71) of the station device which is vacant (not receiving) the transmission signal to the station device 56. The wide band signal 100 to the space division switch 9
2. Modulate the laser selected by 2. Here, although there are a total of four terminal devices 24 to 27, the receiving end (light receiving element) of the station device 56 is reduced to three, assuming that it rarely becomes necessary for four to communicate at the same time. That is, only three terminal devices can communicate at the same time. However, if it is statistically sufficient to be able to talk with three terminal devices at the same time at almost all times, the number of light receiving elements can be reduced and the station device 56 can be made smaller by doing so. In this way, by reducing the number of receiving ends (light receiving elements) of the station device 56 to be smaller than the number of terminal devices, most of the time is statistically busy (not busy) even if many terminal devices are accommodated. The line can be set up without any need, and the station device can be made smaller.

Similarly, the terminal devices 25 to 27 also have a laser 83 corresponding to the receiving end (light receiving elements 69 to 71) of the station device which is vacant (not receiving) the transmission signal to the station device 56.
To 91, the broadband signals 101 to 103 are modulated by the space division switches 93 to 95 to the selected laser. The space division switches 92 to 95 are controlled by control signals 96 to 99 from the control circuits 48 to 51 shown in FIG.

In the embodiment of the present invention, since a large number of optical fibers are used for the connection between the terminal device, the optical coupler and the station device, the optical fibers are entangled with each other, or the fusion splicing of the optical fibers is troublesome. However, it can be easily solved by using an optical fiber ribbon coated with nylon by bundling a large number (8 to 200) of optical fibers. Further, in the embodiment of the present invention, since a large number of lasers and light receiving elements are used, there are drawbacks that the cost of optical components becomes high and the size of the device becomes large. The price has been dramatically reduced due to, and a large number of arrays of lasers and photo detectors have been arranged (a large number of optical components are arranged by optical integration).
By doing so, it can be solved in recent years.

[0023]

As described above, the optical communication system of the present invention has a simple structure and enables bidirectional communication. In particular, at a high bit rate (for example, 150 Mb / s or more), the system has a simple structure and can be constructed at a low cost as compared with other optical communication systems, and the effect of the present invention is exerted.

The following numerical examples can be considered in order to introduce the present invention with concrete economic effects. That is, the distance from the station to the optical coupler box is 200m to 20k.
The optical coupler box is arranged so that the distance from the optical coupler box to the terminal device is about 10 m to 200 m. The number of optical fibers bundled with light and fiber ribbons is set to 10 to 200. Further, the number of branches of the optical coupler is changed from 100 to 1000. That is, one optical coupler box can accommodate 100 to 1000 terminal devices (that is, subscribers).

[Brief description of drawings]

FIG. 1 is a block diagram showing a station device part of a downlink part in an embodiment of the present invention.

FIG. 2 is a block diagram showing an optical star coupler box portion of a downlink portion in an embodiment of the present invention.

FIG. 3 is a block diagram showing a terminal device portion of a downlink portion in an embodiment of the present invention.

FIG. 4 is a block diagram showing a station device part of an uplink part in an embodiment of the present invention.

FIG. 5 is a block diagram showing an optical star coupler box portion of an uplink portion in an embodiment of the present invention.

FIG. 6 is a block diagram showing a terminal device portion of an uplink portion in an embodiment of the present invention.

FIG. 7 is a block diagram showing a downlink of a conventional optical communication system.

FIG. 8 is a block diagram showing an uplink of a conventional optical communication system.

[Explanation of symbols]

1-3 ... Broadband signal, 4 ... Exchange, 5 ... Control circuit, 6 ...
Control signal, 7-9 ... Output port, 10-13 ... Laser,
14 ... Optical fiber ribbon, 15 ... Optical star coupler
Box, 16-19 ... Optical Star Coupler, 20-23
... optical fiber ribbon, 24-27 ... terminal device, 28-
43 ... Light receiving element, 44-47 ... Space division switch, 48
˜51 ... Control circuit, 52-55 ... Wideband signal, 56 ... Station device, 61-63 ... Wideband signal, 64 ... Exchange, 65 ...
Control signals, 66 to 68 ... Input ports, 69 to 71 ... Light receiving element, 72 ... Optical fiber ribbon, 73 to 75 ... Optical star coupler, 76 to 79 ... Optical fiber ribbon, 80 ...
91 ... Laser, 92-95 ... Space division switch, 96-
99 ... Control signal, 100-103 ... Wideband signal

Claims (1)

[Claims] 1. Each of a plurality of transmission ends in a station device,
Through the downlink star coupler provided corresponding to each transmission end, is branched and connected by an optical communication path to each reception end of the plurality of terminal devices, each of the plurality of reception ends in the station device,
Via an upstream star coupler provided for each receiving end, it is branched and connected to each transmitting end of a plurality of terminal devices by an optical communication path, and the station device selects an empty transmitting end that is not transmitting. Then
A transmission means is provided for simultaneously transmitting downlink signals via an optical communication path to each receiving end of a plurality of terminal devices via the downlink star coupler corresponding to the transmitting end, wherein the plurality of terminal devices receive their own reception signals. It comprises a selective receiving means for selecting and receiving a downlink signal for its own terminal from the end, each of the plurality of terminal device has a terminal device side transmitting end that can communicate with an empty station device side receiving end not communicating. An optical communication system, comprising: selective transmitting means for selecting and transmitting an upstream signal, wherein the station device comprises a receiving means for simultaneously receiving upstream signals by a plurality of receiving ends.