JPS6326935B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical bus transmission system comprising a light emitting element, a light receiving element, an optical branch, and an optical fiber cable.

Optical transmission is being put into practical use in a wide range of fields as optical transmission technology has developed in recent years. Optical transmission involves conversion between electrical and optical signals, but compared to electrical signal transmission, optical transmission has a larger transfer capacity, is less susceptible to interference, and allows for thinner cables, so it is expected to be applied to information processing systems. There is. In order to widely apply it to information processing systems, it is necessary to establish an optical bus transmission method similar to the conventional bus transmission method using electric signals.

As an optical bus transmission method, a method using an optical T branch/T coupler or an optical star branch/star coupler is known. FIG. 1 shows a conventional bus transmission system using electric signals, FIG. 2 shows an optical bus transmission system using optical T-branching, and FIG. 3 shows an optical bus transmission system using optical star branching.

For example, channels 1 and 1a in an information processing device
This is a bus transmission method or an optical bus transmission method provided between the IO controller (IOC) 2, 2a in a plurality of input/output devices.

In the conventional bus transmission system shown in FIG.
Receiving circuit (RV) 22 provided in channel 2 receives the electrical signal via electric cable 3 forming a transmission circuit, and conversely, RV 12 provided in channel 1 receives the electrical signal of each DV21 provided in a plurality of IOCs 2. It is normal to do so.

Figure 2 shows an optical bus transmission system using an optical T-branch/optical T-coupler for the electrical signal bus transmission system with the configuration shown in Figure 1, and Figure 3 shows an optical bus transmission system using an optical star branch/optical star coupler. This is an example of configuring a transmission method.

2 and 3, a light emitting element 31 and its driving circuit 32 are provided in the optical transmission channel 1a instead of the DV11 of the channel 1 in FIG. 1, and a light receiving element 41 and its amplifying circuit 42 are provided instead of the RV12. It is provided. Further, instead of the RV 22 in the plurality of IOCs 2, a light receiving element 41a and its amplifier circuit 42a are provided in the optical transmission IOC 2a, and instead of the DV 21, a light emitting element 31a and its driving circuit 32a are provided. 4 is an optical fiber cable. Optical T branch 5/Optical T coupler 5a
As shown in the cross-sectional views of FIGS. 4a and 4b, in each case, a half mirror 51 made of a transparent material, such as a metal vapor-deposited film formed on the surface of a glass plate, is arranged at 45 degrees to the optical axis.
Convex lenses 52a, b, c and optical connector 53
A, b, and c are arranged, and the structure is common and can be used interchangeably, except that the relationship between optical input and optical output is different.

In FIG. 4a, the incident light is transmitted through a convex lens 52a,
Half mirror 5 after becoming almost parallel due to b and c
1, the light is divided into branched light and transmitted light. Figure 4b
In this case, a portion of both incident lights become combined light.
The ratio takes a constant value according to the characteristics of the half mirror 51. A similar relationship also exists between the optical star branch 6 and the optical star coupler 6a. Note that 50 is a light-shielding container.

Comparing the optical bus transmission method using the optical T-branch 5/optical coupler 5a shown in FIG. 2 and the optical bus transmission method using the optical star branch 6/optical star coupler 6a shown in FIG. The total length is Hikari T
The branch 5/optical T coupler 5a is shorter,
It is also superior in terms of the cost of optical fiber cables and the difficulty of installing optical fiber cables.
It can be said that it is more preferable. However, optical T branch/optical T
An optical bus transmission system using a coupler has a drawback in that it is difficult to evenly distribute the power level of received light due to light distribution. For example, when using the optical T-branch 5,
When the division ratio of branched light/transmitted light of the optical T branch is large, the amount of light received by the light receiving element 41a at the near end IOC2a is large, and the amount of light received by the light receiving element 41a at the far end IOC2a is large.
When the amount of light received at a is small and the division ratio is small, the amount of light received at the far end is large and the amount of light received at the near end is small.

For example, in the configuration shown in Figure 2, if there are five IOC2a #1 to #5 and the insertion loss of the optical T-branch 5 and the loss of the fiber cable 4 can be ignored, the splitting ratio of branched light/transmitted light of the optical T-branch is 1. /3: In the case of 2/3, the received light amount of #1 IOC2a is -6.5db, -8.3db, -10.1db and -7.0db from 1/3 = -4.8db.
So, if the split ratio is 1/10:9/10, it is #1
The amount of light received by IOC2a is - in order from 1/10 = -10db
10.5db, -10.9db, -11.4db and -1.8db.

In this way, according to the division ratio of the optical T-branch, #1 to
There are cases where there is a difference in the amount of light received by the IOC 2a of No. 5.

Since the signal error rate is greatly affected by the amount of received light, we have explained an example of an optical T-branch using a half mirror, but the IOC can also be applied in the case of a T-branch using other means.
It is obvious that there will be a difference in the amount of light received by IOC 2a, so in the conventional optical transmission bus system using optical T-branch 5, the code error rate of multiple IOC 2a will vary, and the reliability of the optical transmission system as a whole will decrease. It also has the disadvantage that the maximum number of optical T-branches that can be connected downstream is limited.

The object of the present invention is to provide means for compensating for this drawback. Therefore, the present invention provides an optical bus transmission system comprising one light-emitting element, a plurality of light-receiving elements, an optical T-branch corresponding to the plurality of light-receiving elements, and an optical fiber cable connecting each of the elements and the optical T-branches. Each T-branch has a variable light amount division ratio of branched light/transmitted light, and the received light amount information of each light receiving element and the branched light/transmitted light at each optical T-branch are
It is equipped with a means for transmitting the light amount division ratio information of the transmitted light from the light receiving element side to the light emitting element side, and based on both information, the light amount division ratio of the branched light/transmitted light of each optical T branch is sent to the light emitting element side. This method is characterized in that the amount of light received by a plurality of light receiving elements is made equal by changing the instruction.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIGS. 5a and 5b are structural diagrams of an optical variable T-branch 7 having a function of variable branching light/transmitting light used in an optical bus transmission system in an embodiment of the present invention. The optical variable T-branch 7, as shown in the cross-sectional structural diagram of FIG.
The other configuration is the same convex lens 5 as in Fig. 4 a and b.
2a, b, c and optical connectors 53a, b, c. As shown in the perspective view of FIG. 5b, the variable half mirror 54 is configured to move according to the circumferential direction of the glass disk when a reflective film such as a metal vapor deposition film is formed on the surface of a disk-shaped transparent body, such as a glass disk. A shaft 54b is provided on a variable half mirror plate 54a whose film thickness is sequentially and continuously changed to become a half mirror.
The variable half mirror plate 54a is rotated by the rotation of the variable half mirror plate 54a, so that light can be continuously branched between 0% and 100% of the incident light. 50a is a light-shielding container. The optical variable T coupler 7a also has the same structure as shown in FIGS. 5a and 5b, and the optical T coupler 7a shown in FIGS.
Similar to the relationship between the branch 5 and the optical T coupler 5a, the input and output of light are in opposite directions.

FIG. 6 shows an optical bus transmission system according to an embodiment of the present invention, in which a plurality of optical T-branches 5/optical T-couplers 5a used in the conventional optical bus transmission system of FIG. Multiple optical T-branches 7/optical T-couplers 7 with variable branching light/transmitted light functions
They are all the same except that they are all replaced with a.

Now, according to the following procedure, each of the optical bus transmission systems using multiple optical T-branches 7 in FIG.
Adjust the amount of light received by IOC2a evenly.

(1) Initially, the light amount division ratio of each optical T-branch 7 is set to the minimum. (Increase the amount of transmitted light.) (2) At that point, measure the amount of light received by each light receiving element 41a. If the amount of received light does not reach the minimum level that allows optical transmission, the light amount division ratio of the optical T-branch 7 corresponding to that light receiving element 41a is increased to the minimum level that allows optical transmission.

(3) Each IOC 2a transmits the light amount division ratio of each optical T-branch 7 and information on the amount of light received by the light receiving element 41a to the channel 1a. In the example in Figure 6, each IOC
The light emitting element 31a provided in the channel 1a transmits light to the light receiving element 41 of the channel 1a through the optical fiber cable 4 and the optical T-coupler 7a.

(4) In the channel 1a, the loss in the optical fiber cable 4 and the optical T-branch 7 is calculated from the light intensity division ratio of the optical T-branch 7 from each IOC 2a, the received light quantity information of the light-receiving element 41a, and the light-emission quantity information of the light-emitting element 31 of channel 1a. Calculate. Based on these values, the light amount division ratio of each light T-branch 7 is calculated so that the amount of light received by all the light receiving elements 41a is equal.

(5) Transmit the calculated light amount division ratio information of the optical T-branch 7 to each IOC 2a. For this information transmission, the light emitting element 31 of the channel 1a uses the optical bus transmission system to send the information to each light receiving element 41a.

(6) Each IOC 2a changes and sets the light intensity division ratio of the corresponding optical T-branch 7 according to the light intensity division ratio information from the channel 1a.

As described above, each light receiving element 41 in each IOC2a
It is possible to equalize the amount of light received at a. For information processing systems, these procedures should be followed when changing the system.
Alternatively, if necessary, it may be incorporated into a function that automatically diagnoses each input/output device when the information processing system is powered on.

The above has explained the operation by optical T branch 7 from channel 1a to each IOC 2a, but optical transmission from each IOC 2a to channel 1a is also based on the amount of light received in the channel and T.
It goes without saying that the amount of received light can be made equal based on the information on the light amount synthesis ratio at the coupler. Furthermore, if a T coupler with no coupling loss is used without using a half mirror, the amount of light received in the channel will be approximately equal, and the amount of light emitted by the light emitting elements of each IOC can be adjusted as necessary.

As described above, according to an embodiment of the present invention, a highly reliable optical bus transmission system can be obtained by changing the light amount division ratio of each optical T-branch to equalize the amount of light received by each light receiving element. I can do it.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional bus transmission system using electrical signals, Figure 2 is a block diagram of a conventional optical bus transmission system using an optical T-branch/optical T-coupler, and Figure 3 is a conventional optical star branch/optical star coupler. Block diagram of optical bus transmission system by
Figures a and b are structural cross-sectional views of a conventional optical T-branch/optical T-coupler, Figures a and b are diagrams showing the structure of a variable T-branch, and Figure 6 is an optical bus transmission system in an embodiment of the present invention. FIG. 1 and 1a are channels, 2 and 2a are IO controllers, 3 is transmission cable, 4 is optical fiber cable, 5 is optical T branch, 5a is optical T coupler, 6 is optical star branch, 6a is optical star coupler, 7 is Optical variable T
Branch 7a is an optically variable T-coupler.

Claims (1)

[Claims] 1. In an optical bus transmission system consisting of one light-emitting element, multiple light-receiving elements, optical T-branches corresponding to the plurality of light-receiving elements, and optical fiber cables connecting each of the elements and the optical T-branches, each of the optical T-branches Variable light intensity division ratio of branched light/transmitted light,
It is equipped with means for transmitting information on the amount of light received by each light receiving element and information on the light amount division ratio of branched light/transmitted light in each light T branch from the light receiving element side to the light emitting element side, and based on both information, each light T An optical bus transmission method characterized in that the amount of light received by a plurality of light receiving elements is made equal by changing the light amount division ratio of branched light/transmitted light from the light emitting element side to the light receiving element side.