JPS5873253A - Optical signal transmission system - Google Patents

Abstract

PURPOSE:To eliminate the need for a large dynamic range in a receiving circuit, by eliminating a photo detection level at each terminal from being changed with a transmission signal from any terminal. CONSTITUTION:An output signal from terminal devices 7a-7d is converted into an optical signal with an electrooptic conversion circuits 5a-5d, coupled with the feeder fiber 10 with optical branching devices 4a-4d and transmitted to a main receiver at the termination section. The output of the device 8 is applied to a main transmitter 9, which converts an electric signal into an optical signal, and the optical signal passes through the devices 4a-4d via the 2nd feeder fiber 11 and applied to optoelectirc conversion circuits 6a-6d provided at terminal sections 7a-7d. The output of the circuits 6a-6d are applied to the terminals 7a-7d. Each terminal receives an adderss included in the signal when it is the address of itself and does not receive if different.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to provide an optical signal transmission system that replaces a data bus with an optical transmission line and takes advantage of the characteristics of optical fiber transmission.

A conventional optical network is T-shaped as shown in FIG.

It is roughly divided into three types: a loop shape as shown in FIG. 2, and a star shape as shown in FIG. In Figs. 1 to 3, 1 is a terminal device;
2 is an optical splitter, and 3 is a star coupler, which is a type of large splitter.

In general T-shaped networks and loop-shaped networks, when optical branching is performed using a passive access coupler, branching loss increases exponentially in proportion to the number of terminals, and as the number of terminals increases, optical fibers with a large dynamic range The disadvantage is that it requires a receiver.

A star network has the characteristic that branching loss only increases logarithmically with respect to the number of terminals, and a network of the required scale can be constructed using optical receivers with a relatively small dynamic range. However, if there are terminals in each room in a building, the wiring becomes complicated.

The present invention aims to eliminate the above-mentioned drawbacks, and embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 4, the output signals of the terminal devices 7d to 7d are converted into optical signals by the electro-optical conversion circuits (E/○) 6a to 6d, and then sent to the first trunk fiber 1o by the optical splitters 4a to 4d.
and is transmitted to the main receiving device 8 at the terminal end. The output of the main receiving device 8 is supplied to the main transmitting device 9. The main transmitter 9 converts the electrical signal into an optical signal, and the optical signal is passed through the optical splitters 4A to 4D by the second trunk fiber 11 to the photoelectric conversion circuits 6a to 6a provided at each terminal part 7a to 7b. 6d
supplied to The outputs of the photoelectric conversion circuits 6a to 6d are supplied to each terminal 7a to 7d. Each of the terminals 7a to 7d accepts the signal if the address included in the signal is its own address, and does not accept the signal if the address is different.

For details of this communication control means, please refer to Ethevnet.
etc., so it is omitted here.

This method according to the present invention has a major feature in that the reception circuit does not require a large dynamic range because the level of light received at each terminal does not change regardless of the signal transmitted from any terminal.

Furthermore, if the above features are used, the direction of insertion from the branch to the main line and the direction of branching from the main line to the branch are constant, so the branch ratio can be changed in advance depending on the location of the switch. Once installed, the light emission level at any position can be made almost constant. That is, in FIG. 2, assuming that there is no fiber loss or connector loss, n
Assuming that there are 3 terminals, the branching ratios are -, ~, □, ... n in order from the branching switch closest to the main transmitter.
If R-1n-2 .

The same applies to the light emission level.The coupling ratios are set as 1 n'n-1' n in order from the main receiving device side7. ......, i, 1, even if the optical output of the photoelectric conversion circuit 6 of each terminal is constant, the main receiving device can receive the signal from any terminal with almost constant optical power. . This makes it extremely easy to design optical power distribution and nine circuits, leading to stability and cost reduction.

Next, using Figure 6, we will explain a single-wire transmission network that takes advantage of the features of the present invention.The basic idea is the same as the one in Figure 4, but the basic idea is to use a single trunk fiber, and from the terminal to the terminal. Wire saving is achieved by using the first wavelength of light in the up direction, which is the direction of the main receiving device, and using the second wavelength in the down direction.

In FIG. 5, the signal transmitted from the terminal 7 is transmitted to the photoelectric conversion circuit 2.
5 emits light at a first wavelength λ1, and is supplied to the branching coupler 31. Details of the branching coupler 31 are shown in FIG. In FIG. 4, if the optical power of λ1 at part 21 is expressed as P1λ1, the following relationship (ignoring insertion loss) is P2λ1"3'1"::p,a.

P2λ2+P4λ2 slope P1λ2 P3λ1/P2λ什P4λ2/P2λ2 - Regarding the axis, that is, λ1, the input of P2 and the input of P3 are mixed,
The output is On the other hand, regarding λ2, the signal supplied to Pl (from the outside) is branched to P2 and P4.

Next, in FIG. 5, the optical signal supplied to the branching coupler 31 is transmitted through the trunk fiber 32, and the optical signal is transmitted through the optical splitter 3 at the terminal end.
Details of the optical distributor 36 supplied to the optical system 6 are shown in FIG. In Figure 7, the light of λ1 entering from point A is B
The light of λ2 entering from point 0 is output to point A.

Again in FIG. 6, the upstream optical signal that has passed through the distributor 36 is
It reaches the main receiving device 8. The electrical output of the main receiving device is supplied to the main transmitting device 39. The oscillation wavelength of the main oscillator 39 is oscillated at a second wavelength λ 2 and is transmitted down the trunk fiber 32 via the distributor 36 . This optical signal passes through the branch coupler 31 and then passes through the photoelectric conversion circuit 6 at each terminal.
will receive 4 salaries.

As mentioned above, by using only one trunk fiber,
The lines are reduced without sacrificing the features of Figure 2.

The number of connectors can be reduced.

Next, using FIG. 8, a configuration for expanding this method will be described. In FIG. 8, a main line section 61 and branch line sections 62, 6
3. The components consisting of... are the same as in Figure 3, but the terminal unit of the main line section is not directly connected to the terminal device, but the main transmitting device and main receiving device of the branch line section are connected. be done. That is, the output of the photoelectric conversion circuit 6 of the main line section 61 is connected to the main transmitting device 39 of the branch line section 62, and the output of the main receiving device 8 of the branch line section 62 is connected to the electro-optical conversion circuit 26 of the main line section.

Other terminal portions of the main line portion may be similarly coupled to the branch line portion, or some terminal devices may be coupled as they are. With such a configuration, two-dimensional wiring can be performed.

In other words, it is conceivable to route the main line section vertically within the pill, and route the branch line section horizontally for each floor. With this two-dimensional wiring, compared to one-dimensional wiring that simply connects continuously, the number of branch couplers that pass through from the longest terminal to the terminal is reduced, allowing for efficient design. It becomes possible.

For example, when considering 16 terminals, it is necessary to pass through a maximum of 16 branch couplers in a -dimensional wiring, but a maximum of 8 in a two-dimensional wiring.

This allows a signal transmitted from any one terminal to be supplied to all terminals almost simultaneously.

As described above, according to the present invention, the light reception level of each terminal does not vary depending on the signal from any terminal.

Furthermore, by changing the branching/coupling ratio depending on the installation location, the light reception level and light emission level of each terminal are almost constant. In addition, it can be transmitted using a single fiber, saving wires. moreover,
A two-dimensional configuration is possible, wiring can be done in groups for each procif, and an efficient wiring configuration is possible. It also allows for effective and equal distribution in terms of light level.

[Brief explanation of drawings]

1, 2, and 3 are configuration diagrams of optical networks in conventional examples, FIG. 4 is a block diagram showing the basic configuration of the optical signal transmission system of the present invention, and FIG. 6 is a block diagram showing the basic configuration of the optical signal transmission system of the present invention. FIGS. 6 and 7 are block diagrams of a part of FIG. 4, and FIG. 8 is a block diagram of another embodiment. 4a to 4d... optical splitter, 6a to 6d...
...Electronic conversion circuit, 7a to 7d...Terminal device,
8... Main receiving device, 9... Main transmitting device, 10°11... Trunk fiber, 6a to 6d.
...Photoelectric conversion circuit, 4A to 4D... Optical splitter, 26... Photoelectric conversion circuit, 31...
Branch coupler, 32... Trunk fiber, 36...
...Optical distributor, 39...-Main transmitter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure! Figure 3 Figure 4 115 Figure \7/ Figure 6 j

Claims (4)

[Claims] (1) A T-shaped network is provided in which a plurality of optical branching couplers are cascaded by trunk fibers, and the optical signal transmitted from the electro-optical conversion circuit coupled to the branch part of the optical branching coupler is connected to the trunk fiber. The electrical signal transmitted through the fiber in the same upstream direction is received by the main receiving device installed at the end, and the output of this main receiving device is supplied to the main transmitting device, and the optical signal from this oscillating device is is an optical signal transmission method characterized by being transmitted in the same downstream direction and supplied to the photoelectric conversion circuits of all terminals. (2) Claim 1 describes the use of an integrated fiber as the trunk fiber, transmitting at a first wavelength in the up direction, transmitting at a second wavelength in the down direction, and providing a splitter at the terminal end. optical signal transmission method. (3) The optical signal transmission system according to claim 1, in which the branching ratio of the branching coupler is changed according to the number and position of the terminals so that the light reception level of each terminal is almost constant. (4) The output of the photoelectric conversion circuit of the terminal section of the first transmission system is connected to the input of the main transmitter of the second transmission system, and the input of the electro-optical conversion circuit of the terminal section is connected to the input of the main transmitter of the second transmission system. By connecting the output of the main receiver,