JPS6142975B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a system for transmitting and receiving optical signals between a transmitting device and a receiving device using an optical fiber as a transmission path, in which the level of the optical signal reaching the receiving device is set to a predetermined level. The present invention relates to a method for adjusting an optical transmission line that can be adjusted with a simple operation and an economical configuration.

A system for transmitting and receiving optical signals by connecting a transmitting device having an electrical-to-optical converter that converts an electrical signal to an optical signal and a receiving device having an optical-to-electrical converter that converts an optical signal to an electrical signal through an optical fiber. In this case, it is necessary to adjust the level of the optical signal applied to the optical-to-electrical converter provided in the receiving device so that it falls within a certain predetermined range. This is because if the input level of the optical signal is too high or too low, the optical-to-electrical converter will not operate normally.

If the transmitting device and receiving device are placed close to each other, or if the level of the optical signal output from the electrical-to-optical converter of the transmitting device is too high, the optical-to-electrical converter of the receiving device may Since the level of the applied optical signal becomes too high, conventionally, as shown in FIG. An optical attenuator 4 is interposed in the optical path 3 to adjust the level of the optical signal input to the optical-to-electrical converter 2 to be within a permissible range, but the following drawbacks occur.
In the figure, numerals 5 to 7 are optical connectors.

(1) It is not economical because it uses an expensive optical attenuator.

(2) It is necessary to measure the input level using an optical power meter, which complicates the adjustment work as described below.

Light emitting element (not shown) in the electricity/light converter 1
The sum total of variations in the level of the optical signal output from the optical connector 5, variations in the coupling loss of the optical connector 5, variations in the transmission line 3, etc. In other words, the variation in the optical level in the optical connector 6 is several dB due to the characteristics of each element. optical connector 7.
Connect an optical power meter to the
It is common to take fixed discrete values such as 6dB and 10dB. ) between the optical connectors 6 and 7, actually measuring the optical power level at the optical connector 7, and determining the optical attenuator to be connected based on the measurement results. Moreover, it is uneconomical because it is necessary to prepare a plurality of optical attenuators with different attenuation amounts. In addition, if you use a variable optical attenuator that can continuously change the amount of attenuation,
Although the adjustment operation becomes easier, variable optical attenuators are expensive and therefore uneconomical.

For example, if the allowable input level difference of the optical-to-electrical converter 2 is 3 dBm, the variation in the optical output level of the electrical-to-optical converter 1 is 3 dBm, and the variation in connection loss of the optical connector 5 is 1 dBm, the level diagram at this time is is shown in Figure 2. Therefore, if the connection loss of the optical connectors 6 and 7 is a negligible value, when the level of the optical signal input to the optical connector 6 is at the level of point A shown in the figure,
An optical attenuator with an attenuation of 6 dB is connected, and the level of the optical signal output from the optical attenuator is adjusted to the level at point A', and the level of the optical signal input to the optical connector 6 is adjusted to the level at point B. In this case, it is necessary to connect an optical attenuator with an attenuation of 3 dB so that the level of the optical signal output from the optical attenuator matches the level at point B'.

(3) The reliability of the transmission line decreases because an optical attenuator is involved, which has little experience in use and whose reliability is uncertain.

The present invention has improved the above-mentioned drawbacks, and its purpose is to make it possible to adjust the level of an optical signal reaching a receiving device with a simple operation and an economical configuration. Examples will now be described in detail.

FIG. 3 is a block diagram of an apparatus for carrying out the method of the present invention, in which 8 is a transmitter, 9 is a receiver, 1
0 and 22 are electrical/optical converters, 11 and 23 are adjustment circuits, 12 and 19 are display circuits, 13 and 20 are switching circuits, 14 and 21 are transmission data input terminals, and 15 and 1
7 is an optical/electrical converter, 16 and 18 are detection circuits, 2
4 and 25 are transmission lines, and 26 to 29 are optical connectors. Although the transmitting device 8 and the receiving device 9 are connected using two transmission paths 24 and 25, it goes without saying that they may be connected using one bidirectional transmission path.

When carrying out the method of the present invention, first, as shown in the figure, the switching circuit 13 of the transmitting device 8 is connected to point a, the switching circuit 20 of the receiving device 9 is connected to point c,
Next, from the transmission data input terminal 14, for example, as shown in FIG.
Add the adjustment signal T ₁ shown in . This adjustment signal
T ₁ is connected to the electrical/optical converter 10 via the switching circuit 13
added to. For example, as shown in FIG. 5, the electrical/optical converter 10 and the adjustment circuit 11 include a resistor 30, a light emitting element 31, a transistor 32, a drive circuit 33,
It is composed of a variable resistor 34, and the electrical/optical converter 10 receives the adjustment signal _T1 from the switching circuit 13.
By controlling the current flowing through the base of the transistor 32 via the drive circuit 33, as well as through the resistor 30, the light emitting element 31, and the transistor 32,
The light emitting element 31 transmits an optical signal corresponding to the adjustment signal _T1 .
The adjustment circuit 11 also includes a variable resistor 3 connected in parallel to the light emitting element 31.
By changing the value of 4 and changing the current flowing through the light emitting element 31, the level of the optical signal output from the light emitting element 31 is adjusted.

The optical signal corresponding to the adjustment signal T ₁ from the light emitting element 31 is sent to the optical-to-electrical converter 1 of the receiving device 9 via the optical connector 26 , the transmission line 24 , and the optical connector 27 .
Added to 7. For example, as shown in FIG. 6, the optical/electrical converter 17 includes a light receiving element 35, a resistor 36,
It is composed of an amplifier 37, a filter 38, and a comparator 39. The optical signal applied via the optical connector 27 is converted into an electrical signal by the light receiving element 35, and this electrical signal is sent to the comparator 39 via the amplifier 37 and filter 38. In addition, it is added to the detection circuit 18 after waveform shaping.

By the way, if the level of the optical signal corresponding to the adjustment signal T ₁ applied to the light receiving element 35 is appropriate, the output signal T ₃ of the comparator 39 will be approximately equal to the adjustment signal T ₁ ; If the level of the optical signal corresponding to the applied adjustment signal _T1 is too high, the signal _T2 applied to the comparator 39 will be as shown in Figure B, and the output signal _T3 of the comparator 39 will be as shown in Figure C. It will be shown. As can be seen from A and C in the same figure, when the level of the optical signal applied to the light receiving element 35 is too high, the high level period of the signal T ₃ is longer than that of the adjustment signal T ₁ (t ₁ < _t2 ). Furthermore, if the level of the optical signal corresponding to the adjustment signal T ₁ applied to the light receiving element 35 is too low, the signal T ₂ applied to the comparator 39 becomes as shown in figure D, and the output signal T ₃ of the comparator 39 becomes As shown in FIG. 5E, the high level period is shorter than that of the adjustment signal _T1 . In addition, in FIGS. B and D, S indicates the threshold level of the comparator 39.

The signal T ₃ output from the comparator 39 of the optical/electrical converter 17 is applied to the detection circuit 18, and the detection circuit 18 determines the level of the optical signal applied to the light receiving element 35 based on this signal T ₃ . When it is determined that it is appropriate, the output signal R is set to "1". Detection circuit 1
8, for example, as shown in FIG. 7, a driver 40;
It is composed of a capacitor 41, comparators 42, 43, an AND gate 44, and resistors 45 to 48, and the output signal _T3 of the optical/electrical converter 17 is "1".
During the period, the driver 40 is turned on and the charge in the capacitor 41 is discharged through the resistor 45, and during the period when the signal _T3 is "0", the driver 40 is turned on.
0 is turned off, and the capacitor 41 is charged via the resistor 46. Therefore, the relationship between the terminal voltage V _IN of the capacitor 41 and the mark width of the signal T ₃ (the period during which the signal T ₃ is at a high level) is as shown in FIG.

The comparator 42 compares the terminal voltage V _IN of the capacitor 41 with the reference voltage V _L , and when the terminal voltage V _IN is higher, that is, the mark width t _L of the signal T ₃ corresponds to the reference voltage V _L. The comparator 43 compares the terminal voltage V _IN with the reference voltage V _H , and when the terminal voltage V _IN is lower, that is, the comparator 43 sets the output signal V _OL to "1". , when the mark width of the signal T ₃ is wider than the mark width corresponding to the reference voltage V _H , the output signal V _OH is set to "1". Therefore, if the mark width of the signal _T3 is approximately equal to the mark width _t1 of the adjustment signal _T1 and is within the range of _tH to _tL , the output signal R of the AND gate 44
becomes “1” and is applied to the electrical/optical converter 22 via the switching circuit 20.

The electrical/optical converter 22 converts the signal R into an optical signal, and connects the optical connector 29, the transmission line 25, and the optical connector 2.
8 to the optical-to-electrical converter 15 of the transmitting device 8 , and the optical-to-electrical converter 15 converts this optical signal into an electrical signal and applies it to the display circuit 12 . Display circuit 12
For example, as shown in FIG. 9, the driver 49,
It is composed of a light emitting element 50 and a resistor 51,
When the signal from the optical/electrical converter 15 becomes "1", that is, when the output signal R of the detection circuit 18 becomes "1", the driver 49 supplies current to the light emitting element 50, causing it to emit light. It is something.

Therefore, when performing an adjustment operation, the operator only has to adjust the value of the variable resistor 34 shown in FIG. 5 while looking at the display circuit 12 so that the light emitting element 50 emits light. It will be easy.
Further, when adjusting the level of the optical signal reaching the optical/electrical converter 15, the switching circuits 13 and 20 may be connected to points b and d, respectively, and the same operation as described above may be performed.

In the embodiment described above, as shown in FIG. 5, by connecting the variable resistor 34 in parallel to the light emitting element 31 and changing the value of the variable resistor 34,
Although the level of the optical signal output from the light emitting element 31 is adjusted, the variable resistor 34 may be connected in series with the light emitting element 31 as shown in FIG. Of course, it is also possible to connect the variable resistor 34 between the drive circuit 33 and the transistor 32 as shown in FIG.

As explained above, when adjusting the level of an optical signal reaching an optical-to-electrical converter, the present invention outputs an optical signal corresponding to the adjustment signal from the transmitting side, and the receiving side adjusts the level of the optical signal that has reached the optical to electrical converter. is within a predetermined range, and transmits this detection result to the transmitting side, which uses an adjustment circuit to adjust the level of the optical signal to be output according to the display on the display circuit that displays this detection result. Since it is a device to be adjusted, it has the advantage that the adjustment operation is easy. In addition, it is economical because it does not use an expensive optical attenuator, and
Another advantage is that reliability can be improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the conventional example, Fig. 2 is a level diagram of the conventional example, Fig. 3 is a block diagram of an apparatus implementing the method of the present invention, and Figs. 4 A to E are explanatory diagrams of the operation of Fig. 3. , FIG. 5 shows the electrical/optical converters 10 and 22.
and a block diagram of the adjustment circuits 11 and 23, FIG. 6 is a block diagram of the optical/electrical converters 15 and 17, FIG. 7 is a circuit diagram of the detection circuits 16 and 18, and FIG. 8 is a mark width and terminal voltage. FIG. 9 is a circuit diagram of the display circuits 12 and 19, and FIGS. 10 and 11 are block diagrams of different embodiments from FIG. 5, respectively. 1, 10, 22 are electrical/optical converters, 2, 15,
17 is an optical/electrical converter, 3, 24, 25 are transmission lines, 4 is an optical attenuator, 5-7, 26-29 are optical connectors, 8 is a transmitting device, 9 is a receiving device, 11, 23
is an adjustment circuit, 12, 19 is a display circuit, 13, 20
is a switching circuit, 14 and 21 are transmission data input terminals,
16, 18 are detection circuits, 30, 36, 45 to 48
31 and 50 are resistors, 31 and 50 are light emitting elements, 32 are transistors, 33 are drive circuits, 34 are variable resistors, 35 are light receiving elements, 37 are amplifiers, 38 are filters, 3
9, 42, 43 are comparators, 40, 49 are drivers, 41 is a capacitor, and 44 is an AND gate.

Claims (1)

[Claims] 1. In a system that connects a transmitting device and a receiving device, each having both an electrical-to-optical converter and an optical-to-electrical converter, through an optical transmission line and transmits and receives optical signals,
The transmitting device sends out an optical signal corresponding to the adjustment signal, and the receiving device detects whether the level of the optical signal corresponding to the adjustment optical signal is within a predetermined range and transmits the detection result to the above. A method for adjusting an optical transmission line, the method comprising adjusting the level of an optical signal sent to a device and outputted by an adjustment circuit in accordance with a display of a display circuit that displays the detection result in the transmitting device. .