JPH0481028A - Optical communication system - Google Patents

Abstract

PURPOSE:To enlarge the scale of a system by providing a second optical multiplexer/ demultiplexer, which outputs the most of an optical signal from a slave station to a transmission line, and a wide band wavelength coupler to connect all the slave stations excepting for the first and N-th slave stations with the transmission line. CONSTITUTION:A first optical multiplexer/demultiplexer 7 is used for connecting a first slave station 5A1 closest from a host station 1A to a transmission line 2, and this first optical multiplexer/demultiplexer 7 connects the transmission line 2 and the first slave station 5A1 so as to output the most of opticals signals from the host station 1A and the first slave station 5A1 to the transmission line 2. A second optical multiplexer/demultiplexer 8 is used for connecting an N-th slave station 5An farthest from the host station 1A to the transmission line 2, the light emitting wavelength of the N-th slave station 5An is made same as that of the host station 1A, and the said second optical multiplexer/demultiplexer 8 connects the transmission line 2 and the N-th slave station 5An so as to supply the most of the optical signal from the host station 1A to the N-th slave station 5An and to supply optical signals from all the slave stations excepting for the N-th slave station 5An to the host station 1A. Thus, the system scale can be enlarged and any power can not be supplied to the transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a multi-drop type optical communication system, and particularly to an optical communication system with an expanded scale.

"Prior Art" Conventionally, in a multi-drop optical communication system, communication is performed between a master station and each slave station using optical signals of the same wavelength. Further, as optical couplers for connecting each slave station and a transmission line (optical fiber), those having the same branching ratio (for example, 10:I) are used.

FIG. 5 is a schematic configuration diagram showing the conventional optical communication system mentioned above. As shown in this figure, both ends of the transmission line 2 are led into the master station L, and one end is connected to the electrical/optical (Elo ) is connected to converter 3, and the other end is connected to optical/1 [air (0/E) converter 4. Slave station 5,,5,--5,-,
, 5□ are each connected to the transmission line 2 via an optical coupler 6.6, and these slave stations 5, . 5.・5□-,,5,
Each is also provided with an E10 converter 3.0/E converter 4. Note that the arrow in the figure indicates the direction in which the optical signal flows.

"Problem to be solved by the invention" By the way, in the conventional optical communication/system mentioned above,
Optical loss that exists between the master station 1 and the slave station located farthest from the master station 1 in the direction in which the optical signal flows along the transmission path, that is, the optical loss that exists in the direction from the master station l to the slave station. The master station 1 and the slave station 5. , , In the direction from the slave station to the master station 1, the optical loss is between the slave station 51 and the master station I, or in either case, Slave station 5D t
The optical dynamic range must be below the performance of the E10 conversion circuit 3 and the OE conversion circuit 4 of ``''``'', 5 *-, , 5-. This one
Is there a limit on the distance of transmission line 2 and the number of slave stations?

Let's take a look at the breakdown of the optical loss mentioned above: master station 1 and slave station 5. Between ((n-1) x (transmission loss of destination coupler 6) - '(2n-1) 2 losses). Looking at these quantitatively, the optical coupler 6
Passage loss is 0.5 dB, connection loss between optical coupler 6 and transmission line 2 is 0.2 dB, and branching loss of optical coupler 6 is 1O.
dB, transmission line 2 loss is 0.5 dB/km (λ-] 3
μm). In this case, slave station 5. ．． 5.・・5ゎ−、
, 5□ and the distance of the transmission line 2, the passing loss of the optical coupler 6 and the loss of the transmission line 2 increase,
The branching loss of optical coupler 6 is 10 dB regardless of these factors.
This is a large value.

In this way, in the conventional optical communication system, the optical loss between the master station l and the farthest slave station in the direction in which the optical signal flows is reduced by the E10 conversion circuit 3 and the O/E conversion circuit 4. Since it is necessary to keep the dynamic range below, there are limitations to the system scale, such as increasing the length of the transmission line 2 and increasing the number of slave stations.

By the way, it is possible to expand the scale of the system by inserting a repeater in the middle of the transmission path and regenerating and amplifying the optical signal, but in this case, the main feature of multi-drop optical communication systems is that there is no transmission path. A problem arises in that power supply is impaired.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide an optical communication system that can solve the above-mentioned problems and expand the system scale.

"Means for Solving the Problems" The present invention includes one master station and a plurality of slave stations connected to a transmission line in the order of receiving the optical signal output from the master station closest to each other. an Nth slave station that receives an optical signal output from the master station at the farthest distance and outputs an optical signal having the same wavelength as the optical signal from the master station; a first slave station that receives the optical signal closest to the first slave station and outputs an optical signal having the same wavelength as the optical signal output from each of the remaining slave stations except for the first slave station;
a first optical multiplexer/demultiplexer that connects a slave station and a transmission line and outputs most of the optical signal from the master station and most of the optical signal from the first slave station to the transmission line; The Nth slave station is connected to the transmission line, most of the optical signal from the master station is supplied to the Nth slave station, and all the slave stations except the Nth slave station are connected to each other. a second optical multiplexer/demultiplexer that outputs most of the optical signals from the second optical signal to the transmission line; and a second optical multiplexer/demultiplexer that outputs most of the optical signals from the first and second slave stations to the transmission line; The present invention is characterized by comprising a broadband wavelength coupler having equivalent characteristics for each of optical signals of two different wavelengths.

"Operation" According to the above configuration, the optical signal from the master station is supplied to the transmission line, that is, other slave stations, without being greatly attenuated by the first optical multiplexer/demultiplexer. Furthermore, the optical signal from the first slave station is also output to the transmission line without being greatly attenuated by the first optical multiplexer/demultiplexer.

On the other hand, the optical signals from all the slave stations except the Nth slave station are
The optical multiplexer/demultiplexer supplies the signal to the master station without significant attenuation. Further, the optical signal from the Nth slave station is also supplied to the master station without being significantly attenuated by the second optical multiplexer/demultiplexer.

Therefore, since the first and second optical multiplexers and demultiplexers having smaller branching losses than conventional optical couplers are used, it is possible to increase the number of transmission paths and the number of slave stations.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a multi-drop type optical communication system which is an embodiment of the present invention.

This example uses a conventional optical communication system (
Figure 5).

■Master station 1. The wavelength of the optical signal output from each of A and slave station D An is set to λ=155 μm.

The wavelength of the optical signal output from each of the other slave stations 5A, 5Ai-5A, - is set to λ-13 μm.

(2) An optical multiplexer/demultiplexer 7 is used to connect the slave station 5A1 to the transmission line 2, and an optical multiplexer/demultiplexer 8 is used to connect the slave station 5A1 to the transmission line 2. The details of each optical multiplexer/demultiplexer 78 will be described below.

FIG. 2 is a diagram showing the optical multiplexer/demultiplexer 7. This optical multiplexer/demultiplexer 7 acts as an optical coupler with a wavelength separation degree of 10 dB (branching loss 05 dB), and has a terminal a connected to a wavelength λ-1.
When a 55 μm optical signal is supplied, 90% of it is output from terminal d, and the remaining 10% is output from terminal d.

Also, when an optical signal with wavelength λ=1.3μ is supplied to terminal C, 90% of it is output from terminal C, and the remaining 10%
is output from terminal d. On the other hand, the wavelength λ-1,
When a 3 μm optical signal is supplied, 90% of it is output from terminal d, and the remaining 10% is output from terminal S.

FIG. 3 is a diagram showing the optical multiplexer/demultiplexer 8. This optical multiplexer/demultiplexer 8 has a wavelength separation degree of 20 dB or more (branching loss 0.Q5d
When an optical signal with a wavelength λ = 155 μm is supplied to terminal a, 99% of it is output from terminal d, and the remaining 1% is output from terminal S. . Furthermore, when an optical signal with wavelength λ=1.3 μm is supplied to terminal C, 99% of it is output from terminal d,
The remaining 1% is output from the terminal. On the other hand, when an optical signal with a wavelength of λ-1, 3μ is supplied to terminal a, 99% of the
The remaining 1% is output from terminal d. Further, when an optical signal having a wavelength of λ-1°55μ is supplied to terminal C, 99% of it is output from terminal 1, and the remaining 1% is output from terminal d.

The above-mentioned optical multiplexer/demultiplexers 7.8 are each connected to the transmission line 2 as shown in FIG. That is, the optical multiplexer/demultiplexer 7 has its terminal a connected to the master station via the transmission line 2! It is connected to the E10 conversion circuit 3B of A, and is connected to the optical coupler 6A via the terminal transmission line 2.

Further, the terminal C is connected to the E10 conversion circuit 3A of the slave station 5A, and the terminal d is connected to the O/E conversion circuit 4A of the slave station 5A. On the other hand, the optical multiplexer/demultiplexer 8 has its terminal a connected to the transmission path 2, and the terminal
/E conversion circuit 4B. Also, terminal C is connected to slave station 5.
A, is connected to the E10 conversion circuit 3B, and the terminal d is connected to the slave station 5.
A number of O/E conversion circuits 4B are connected.

■As an optical coupler 6A that connects each slave station 5A v~5A,,-1 and the transmission line 2, the branching ratio is lO:l, and the optical signals with wavelengths λ = 1.3 μm and 1.55 μm are the same. A broadband wavelength coupler with characteristics is used.

In the optical communication system configured in this way, the master station I
When an optical signal with a wavelength of 1.55 μm is output from A, 90% of it is output from the terminal to the transmission line 2, and the remaining 10% is supplied from the terminal d to the slave station 5A. Here, if the slave station 5A is in the receiving state, 10% of the optical signal output from the master station IA is supplied. Further, the optical signal output to the transmission line 2 is supplied to the slave station which is in the receiving state. In this case, assuming that the slave station 5A is in the receiving state, 99% of the optical signal that has reached the optical multiplexer/demultiplexer 8 is supplied to the slave station D A v. On the other hand, slave station 5A
The optical signal of wavelength λ-13 μm output from , is 9
0% is output from the terminal to the transmission line 2. In addition, slave station 5
Ninety-nine percent of the optical signals output from A, , and having a wavelength of λ-155 μm are supplied to the master station IA through the terminals.

As described above, since the optical multiplexer/demultiplexer 7 is used to connect the slave station 5A+ and the transmission line 2, and the optical multiplexer/demultiplexer 8 is used to connect the slave station 5An and the transmission line 2, conventional Station D A +,
Compared to the optical coupler used for 5 A n, the branching loss is smaller (compared to 10 dB of the conventional optical coupler, the optical multiplexer/demultiplexer 7 has a loss of 0.5 dB, and the optical multiplexer/demultiplexer 8 has a loss of 0.0 dB).
5dB). Therefore, since the branching loss is small, the transmission distance and the number of slave stations can be increased, and the system scale can be expanded. In this case, when attempting to expand the system scale with the conventional configuration, it becomes necessary to insert a repeater in the middle of the optical transmission line 2 and regenerate and amplify the optical signal, but this is not possible with multi-drop optical communication. The transmission line, which is a major feature of the system, is unpowered or damaged.
This is a huge disadvantage. However, in reality, in the conventional technology, the scale of the system is such that a repeater is required, and the same repeater is not required. Therefore, the transmission path can be made without power supply, and the characteristics of the multi-drop optical communication system can be brought out to a large extent.

In the above embodiment, the optical multiplexer/demultiplexer 7 has a wavelength separation of 10 dB, or, similarly to the optical multiplexer/demultiplexer 8, an optical multiplexer/demultiplexer 7 with a wavelength separation of 20 dB or more may be used.

However, in the above embodiment, the optical multiplexer/demultiplexer 7.8 is used only in the slave stations 5A+ and 5Ar, or the optical multiplexer/demultiplexer 7.8 may be used in the remaining slave stations as well.

"Effects of the Invention" As explained above, according to the optical communication system according to the present invention, the first optical multiplexer/demultiplexer is used to connect the transmission path to the first slave station located closest to the master station. Then, the connection between the transmission line of the first optical multiplexer and demultiplexer and the first slave station is established such that most of the optical signals from each of the master station and the first slave station are output to the transmission line. In addition, a second optical multiplexer/demultiplexer is used to connect the Nth slave station located farthest from the master station to the transmission line, and the emission wavelength of the Nth slave station is set to be the same as that of the master station. and the transmission line of the second optical multiplexer/demultiplexer and the Nth optical multiplexer/demultiplexer.
connection with the slave stations, most of the optical signals from the master station are supplied to the Nth slave station, and only the optical signals from all the slave stations except the Nth slave station are supplied to the master station. Conventionally,
Branching loss is reduced compared to the optical coupler used in the first and Nth slave stations. Therefore, since the branching loss is small, it is possible to increase the transmission distance and the number of slave stations, resulting in the effect that the system scale can be expanded. In addition, even if the system scale requires a repeater with conventional technology, the repeater is not required in actual practice, so the transmission path can be powered-free, which is a feature of the multi-drop optical communication system. can be extracted to a large extent.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a multi-drop type optical communication system which is an embodiment of the present invention, Figs. 2 and 3 are diagrams showing an optical multiplexer/demultiplexer applied to the same embodiment, and Fig. 4. 5 is a diagram showing the connection state of each optical multiplexer/demultiplexer to a transmission line, and FIG. 5 is a schematic configuration diagram showing a conventional multitrotub type optical communication system. A... Master station, 2... Transmission line (optical fiber), A,
3B-electrical/optical conversion circuit, A, 4B...optical/electrical conversion circuit, A, ~5A...slave station A1 is the first slave station, 5A is the Nth slave station), A・・・・・・
Broadband wavelength coupler,... Optical multiplexer/demultiplexer (first optical multiplexer/demultiplexer),...
...Optical multiplexer/demultiplexer (second optical multiplexer/demultiplexer).

Claims (1)

[Scope of Claims] An optical communication system comprising one master station and a plurality of slave stations connected to a transmission path in the order of receiving the optical signal output from the master station closest to the slave station. an Nth slave station that receives the optical signal output from the master station at the farthest distance and outputs an optical signal having the same wavelength as the optical signal from the master station; a first slave station that receives the optical signal and outputs an optical signal having the same wavelength as the optical signal output from each of the remaining slave stations except the Nth slave station; and a transmission path between the first slave station and the transmission line. a first optical multiplexer/demultiplexer that connects and outputs most of the optical signal from the master station and most of the optical signal from the first slave station to a transmission line; the Nth slave station and the a transmission line, supplies most of the optical signals from the master station to the Nth slave station, and supplies most of the optical signals from all the slave stations except the Nth slave station. a second optical multiplexer/demultiplexer that outputs to the transmission line; and a second optical multiplexer/demultiplexer that connects each of the slave stations except the first and Nth slave stations to the transmission line, and connects each of the optical signals of the two different wavelengths to the transmission line. What is claimed is: 1. An optical communication system comprising: a broadband wavelength coupler having characteristics equivalent to that of a broadband wavelength coupler;