JPH088829A - Optical communication equipment - Google Patents

Abstract

PURPOSE:To adjust a luminous quantity from an optical transmission unit automatically in the optical communication. CONSTITUTION:An optical signal 11 outputted from a voltage-to-optical transducer circuit 1 is dispersed by an optical prism 2 to produce a light 13 for luminous quantity measurement in addition to a communication light 12 and the light 13 for luminous quantity measurement is transduced to a voltage by an optical- to-voltage transducer solar cell 3. A transduced voltage V11 is compared with a reference voltage V1, V2 generated by a reference voltage circuit 14 at a comparator 5, 6 and a switch 7 is thrown depending on outputs VO1, VO2 of the comparators 5, 6 to select automatically a current limit resistor 8 thereby adjusting the luminous quantity of the voltage-to-optical transducer circuit 1 automatically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication device capable of converting a signal into an optical signal and performing long-distance communication at a high speed with respect to noise when serially communicating a digital signal. It is a thing.

[0002]

2. Description of the Related Art In recent years, optical communication technology has been characterized by high-speed transmission and by being unaffected by disturbances such as noise.
From a digital communication network such as Fax, it has come to be used also as an internal signal transmission device for general household electric appliances such as audio.

An example of the above-mentioned conventional optical communication technique will be described below with reference to the drawings. 2 and 3 are a control block diagram of a transmission unit and a reception unit of a conventional optical communication technique, and a characteristic diagram showing a relationship between a light amount and a current limiting resistance.

In FIG. 2, reference numeral 21 is a photodiode for light transmission, which is composed of a light emitting element. Reference numeral 22 is a photodiode control circuit that controls ON / OFF of the photodiode 21, 23 is a photodiode current control circuit that determines the current value that flows in the photodiode 21, and 24 is a photodiode that determines the current value that flows in the photodiode control circuit 22. This is a photodiode current limiting resistor built in the current control circuit 23. Reference numeral 25 denotes an optical connector that is coupled to the optical transmission unit 31 to receive a controlled optical signal from the photodiode 21 including a light emitting element.
Reference numeral 6 is an optical fiber for transmitting the optical signal received by the optical connector 25, and 27 is an optical connector for coupling the optical signal transmitted from the optical fiber 26 to the optical receiving unit 32. Reference numeral 28 denotes a light receiving photodiode of the light receiving unit 32, which converts an optical signal received from the optical connector 27 into an electric signal and outputs the electric signal through a conversion circuit 29.

The operation of the optical transmitting / receiving unit having the following structure will be described below. In serial communication using a digital signal, first, the transmission signal 30
Is input to the photodiode control circuit 22, the photodiode control circuit 22 turns on and off in synchronization with the transmission signal 30, so that a current intermittently flows to the optical transmission photodiode 21. Since the light emission amount of the diode, that is, the power of the light output changes depending on the magnitude of this current, the magnitude of the current limiting resistor 24 of the photodiode current control circuit 23 is set to the most suitable value using the relationship of FIG. Decide in advance. With the optimum amount of light emission,
The optical signal is transmitted from the optical transmission unit 31 through the optical connector 25, the optical fiber 26, and the optical connector 27 to the optical reception unit 3
2 is sent. The light receiving unit 32 receives the received light signal by the light receiving photodiode 28 and generates a received signal through the conversion circuit 29.

[0006]

However, in the above-mentioned configuration, the power of the optical output changes with the aging of the photodiode on the transmitting side, so that the resistance value of the photodiode current limiting resistor 24 is regularly checked. Due to
Alternatively, there is a problem that maintenance must always be performed because a review must be performed when communication trouble occurs.

In view of the above problems, the present invention is to automatically adjust the power of an optical output, that is, the amount of light in an optical transmission unit.

[0008]

In order to solve the above-mentioned problems, an optical communication device of the present invention is an optical prism that splits a signal optically converted by an electric / optical conversion circuit and divides it into a communication signal and a light amount measurement signal. And a light-to-voltage conversion element that converts the dispersed light signal into a voltage in proportion to the light intensity for light quantity measurement, and to adjust the light emission amount of the electricity-light conversion circuit according to the converted voltage. A means for changing the resistance value, comparing the reference voltage for obtaining the optimum light emission amount with the voltage converted by the light / voltage conversion element, and changing the resistance value according to the difference between the reference voltage Is.

[0009]

According to the present invention, the light emission amount of the current transmission signal can be switched by changing the resistance value while constantly comparing it with the reference voltage, so that the present invention can respond to the change of the light emission amount with good responsiveness. Therefore, it is possible to provide a maintenance-free optical communication device without regularly checking the adjustment of the light emission amount or dealing with a trouble caused by a decrease in the light emission amount.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical communication apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a control block diagram of an optical transmission unit in an optical communication apparatus according to an embodiment of the present invention. In FIG. 1, 1 is an electric / optical conversion circuit, 2 is an optical prism, 3 is a conversion solar cell which is a light / voltage conversion element, 4 is a reference voltage circuit, and 5 and 6 are generated by a reference voltage circuit 4. A comparator that compares the reference voltage with the voltage output from the solar cell 3 for light / voltage conversion, 7 is a switch that switches according to the outputs of the comparators 5 and 6, and 8 is a switch in the electricity / light conversion circuit 1 that is switched by the switch 7. It is a current limiting resistor that controls the amount of light emission. 10 is a transmission signal,
Reference numeral 11 is an optical signal after optical conversion, 12 is communication light after spectroscopy, 13
Is light for measuring the quantity of light after the spectroscopy.

The optical transmission unit 9 configured as described above
The operation will be described below with reference to FIG. The transmission signal 10 is converted into an optical signal 11 by the electro-optical conversion circuit 1. The optical signal 11 is split by the optical prism 2 into a communication light 12 that is transmitted as it is and a light quantity measuring light 13 that travels to the light-voltage converting solar cell 3. The light amount measuring light 13 input to the voltage converting solar cell 3 is converted into a voltage according to the amount of light, and is compared with the reference voltage of the reference voltage circuit 4 by the comparators 5 and 6.

The reference voltage circuit 4 has a resistor R₁, R₂, R₃Or
And the following reference voltage V₁, V₂To generate. V₁= V_cc・ (R₂+ R₃) / (R₁+ R₂+ R₃) V₂= V_cc・ R₃/ (R₁+ R₂+ R₃) Now, the light quantity measuring light 13 is transmitted by the solar cell 3 for light / voltage conversion.
The converted voltage is V _I1Then, the comparator 5
Output V_O1And the output V of the comparator 6_O2Is V_I1And V₁V
₂Depending on the relationship with

The output V _{O1 of the} comparator 5 is V _I1 ≦ V ₁ , V _O1 ≧ 0 V _I1 > V ₁ , V _O1 <0, and the output V _{O2 of the} comparator 6 is V _I1 ≦ V ₂ . When V _O2 ≧ 0 V _I1 > V ₂ , V _O2 <0 _holds . Therefore, depending on the size of V _I1 , V ₀₁ , v _o2
When V _I1 > V ₁ , V _O1 <0, V _O2 <0 V ₁ ≧ V _I1 > V ₂ , when V _O1 ≧ 0, V _O2 <0 V _I1 ≦ V ₂ , V _O1 ≧ 0 and V _O2 ≧ 0.

Therefore, when the resistance values R ₄ , R ₅ , and R ₆ of the three types of current limiting resistors 8 are set to _satisfy the relationship of R ₄ <R ₅ <R ₆ , the switches are switched according to the outputs of V _O1 and V _O2. 7 for V _O1
When <0, V _O2 <0 (amount of light is large), switch to the R ₆ side, and when V _O1 ≧ 0, V _O2 <0 (amount of light is appropriate), R ₅
To the R ₄ side, and when V _O1 ≧ 0 and V _O2 ≧ 0 (light amount is small), switch to the R ₄ side.

As described above, according to this embodiment, the reference voltage values V ₁ and V ₂ are set to the resistances R ₁ and R of the reference voltage circuit 4 depending on whether the amount of communication light is large, appropriate, or small. ₂ and R ₃ are set in advance, and the range of the voltage V _I1 obtained by converting the amount of light dispersed by the optical prism 2 by the light / voltage conversion solar cell 3 is output V _O1 , V 0 of the comparators 5 and 6 Detected by _O2 , current limiting resistor 8 according to the detection result
By switching resistance values R ₄ , R ₅ , and R ₆ of the switch 7 by the switch 7, the light emission amount by the transmission signal 10 can be automatically adjusted in the electric / optical conversion circuit 1, and stable optical communication is realized. can do.

[0016]

As described above, according to the present invention, an electrical / optical conversion circuit, an optical prism for separating the optically converted signal into communication light and light for measuring light quantity, and a spectrum for measuring light quantity. Since a light-voltage conversion element for converting the voltage of the emitted light into a voltage in proportion to the intensity of the light and a means for changing the resistance value for adjusting the light emission amount by the transmission signal according to the converted voltage are provided. Stable light communication can be performed by automatically detecting a large amount and a small amount and automatically switching appropriately the current limiting resistor for adjusting the light emission amount according to the detected result.

[Brief description of drawings]

FIG. 1 is a control block diagram of an optical transmission unit in an optical communication device according to an embodiment of the present invention.

FIG. 2 is a control block diagram of a conventional optical communication device.

FIG. 3 is a characteristic diagram showing a relationship between a light amount and a current limiting resistance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electro-optical conversion circuit 2 Optical prism 3 Light / voltage conversion solar cell 4 Reference voltage circuit 5,6 Comparator 7 Switch 8 Current limiting resistor 9 Optical receiving unit 10 Transmission signal 11 Optical signal 12 Communication light 13 Light quantity measurement light

Claims (1)

[Claims] 1. In serial communication using a digital signal, an electrical / optical conversion circuit for converting a digital transmission signal into intensity of light emission, and an optical signal obtained by the electrical / optical conversion circuit are dispersed to perform communication. Light, and an optical prism that splits the light intensity measurement light to measure the intensity of light emission,
A light-voltage conversion element that converts the light for measuring the amount of emitted light into a voltage proportional to its intensity, and the voltage converted by the light-voltage conversion element is compared with the reference voltage of the optimum light emission amount, and the reference voltage An optical communication device having means for automatically switching the light emission amount according to the difference between the light emission amount and the light emission amount.