JP2001292100A - Optical information transmitter and optical information receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information transmitter that adopts a method for information transmission by an optical fiber and eliminates a noise in a transmission signal. SOLUTION: The optical information transmitter is provided with a means 20 that converts a digital electric signal from a transmission unit 1 into a differential optical signal, optical fibers 4a, 4b that are used to send the differential optical signal from the optical transmitter to an optical receiver, and an electric signal re-conversion means 21 that re-converts the differential optical signal into a digital electric signal. Then a reception unit 7 receives the re-converted digital electric signal. A differential receiver 9 has a hysteresis characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information transmission system, and more particularly, to an optical information transmission device and an optical information reception device for reducing noise of a digital signal to be transmitted.

[0002]

2. Description of the Related Art Information transmission by light is widely used in the communication field, for example, as information transmission by optical fibers.
Optical information transmission requires an optical transmitter that converts an electrical signal to be transmitted into an optical signal and an optical receiver that converts an optical signal transmitted from the optical transmitter into an electrical signal.

An optical transmitter converts an electric signal into an optical signal using, for example, a light emitting diode (hereinafter, referred to as “LED”) or a laser diode (hereinafter, referred to as “LD”) as a light emitting element. Further, the optical receiver converts an optical signal into an electric signal using a photodiode (hereinafter, referred to as “PD”) as a light receiving element, amplifies the electric signal with an amplifier circuit, and outputs the electric signal.

A specific example of information transmission by light using an optical fiber will be described with reference to the drawings. FIG. 4 is a configuration diagram of a conventional optical information transmission device. In the figure, a digital transmission electric signal 10 output from a transmission unit 1 is converted into an optical signal by an optical transmitter 3 and transmitted through an optical fiber 4 as a transmission path. The optical signal transmitted through the optical fiber 4 is converted into an electric signal by the optical receiver 5 and output as a received signal 11, converted into a digital received electric signal 12 by the comparator 8, and received by the receiving unit 7. You.

[0005] The optical transmitter 3 is, for example, an LE as a light emitting element.
An electrical signal is converted to an optical signal using D or LD, but LE
Since D and LD do not have the same rising and falling characteristics of an optical signal, distortion occurs at the time of conversion into an optical signal. The optical receiver 5 converts an optical signal into an electric signal by using, for example, a PD as a light receiving element, amplifies the electric signal with an amplifier circuit, and outputs the electric signal. The light receiving element and the amplifier circuit convert the optical signal into an electric signal. At the time of conversion, since it is difficult to make the rising characteristic and the falling characteristic of the electric signal equal, distortion occurs at the time of conversion to the electric signal.

FIG. 5 is a configuration diagram of another conventional optical information transmission apparatus. In the apparatus shown in FIG. 5, the digital transmission electric signal 10 from the transmission unit 1 is converted into differential electric signals 13a and 13b by the differential driver 2, and is converted into differential optical signals by the optical transmitters 3a and 3b. The differential optical signal is transmitted by the optical fibers 4a and 4b. The differential optical signals transmitted by the optical fibers 4a and 4b are converted by the optical receivers 5a and 5b into differential electrical signals 11a and 11b.
After being converted to b, the signal is converted back to the digital received electric signal 12 by the differential receiver 9 and received by the receiving unit 7.

[0007] The operation of the device thus constructed will be described with reference to a timing chart. FIGS. 6A and 6B are timing charts in the optical information transmission system of FIG. 5, wherein FIG. 6A is a transmission electric signal 10, and FIG. 6B is a differential electric signal 11a, 11b.
(C) is a received electric signal 1 output from the differential receiver 9.
2 is shown. The differential receiver 9 has a differential electric signal 11a.
And 11b are compared. When the differential electric signal 11a has a higher voltage than the differential electric signal 11b, a signal of a logic level "1" is output, and when the differential electric signal 11a has a lower voltage than the differential electric signal 11b. Outputs a signal of logic level "0".

[0008]

However, such a conventional optical information transmission apparatus includes a transmission signal 1 of a transmission unit 1.
When 0 is the waveform 101 (see FIG. 6A), the signal 1
If the waveforms 1a and 11b include noise at the time of rising and falling like the waveforms 102a and 102b (FIG. 6)
(B), the output signal 12 of the differential receiver 9 has a waveform 1
As shown in FIG. 03, there is a problem that a signal including a noise 104 is generated at a change point of the logic level (see FIG. 6C). The present invention has been made in view of the above circumstances, and has as its object to provide an optical information transmission device free of noise in optical information transmission.

[0009]

In order to solve the above-mentioned problems, an optical information transmission apparatus according to the present invention has a structure as shown in FIG.
Means (differential optical signal converting means) 20 for converting the digital electric signal from the transmitting unit 1 into a differential optical signal, and means 4a, 4b for transmitting the differential optical signal from the optical transmitter to the optical receiver
And a means (electric signal re-conversion means) 21 for re-converting the differential optical signal into a digital electric signal. Then, the re-converted digital electric signal is received by the receiving unit 7. Here, the electric signal re-conversion means 21 has a hysteresis characteristic.

According to the first aspect of the present invention, the differential optical signal is converted back into the digital electric signal by using the differential receiver having the hysteresis characteristic. Even if the optical signal contains noise or jitter, it is possible to eliminate the noise of the digital electric signal output from the differential receiver and input to the receiving unit.

Preferably, as set forth in claim 2, the differential optical signal converting means 20 includes the differential driver 2 and the optical transmitter 3.
a, 3b, and the electric signal re-conversion means 21
With the configuration having the differential receivers a and 5b and the differential receiver 6, the optical information transmission device can be realized with a simple configuration. Claim 3
Assuming that the hysteresis characteristic of the differential receiver 6 is such that the bit stream of the digital electric signal can be smoothly reconverted, the differential optical signal transmitted from the optical transmission line is converted into the digital electric signal without delay. Can be converted. Further, as described in claim 4, the hysteresis characteristic of the differential receiver 6 is caused by the asymmetry of the rising characteristic and the falling characteristic of at least one of the differential optical signal converting means 20 and the electric signal re-converting means 22. With a configuration for reducing noise, jitter and the like do not mix into the re-converted digital electric signal.

According to another aspect of the present invention, there is provided an optical information receiving apparatus which receives a differential optical signal converted from a digital electric signal from an optical transmission line, and converts the differential optical signal into a digital electric signal. An optical information receiving apparatus for reconverting the digital electric signal into a signal and receiving the received signal at a receiving unit, wherein the digital electric signal reconverting means has a hysteresis characteristic. The hysteresis characteristic of the digital electric signal re-conversion means reduces noise caused by the asymmetry of the rising and falling characteristics of the electric signal re-conversion means, so that jitter and the like do not mix into the re-converted digital electric signal.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An optical information transmission apparatus according to the present invention is an optical information transmission apparatus using a differential receiver having hysteresis characteristics as a differential receiver of the electric signal re-conversion means. FIG.
FIG. 1 is a configuration diagram of an optical information transmission device showing an embodiment of the present invention. 1 to 3, the same components as those described in FIGS. 4 to 6 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, a transmission unit 1 outputs a digital transmission electric signal 10. Differential optical signal conversion means 20
Has a differential driver 2 and optical transmitters 3a and 3b. The differential driver 2 converts the transmission digital electric signal 10 into differential electric signals 13a and 13b. Here, one of the differential electric signals 13a and 13b has the same logic as the digital transmission electric signal 10, and the other has the opposite logic.
The optical transmitters 3a and 3b convert the differential electric signals 13a and 13b into differential optical signals and transmit the differential optical signals through the optical fibers 4a and 4b.

The electric signal re-conversion means 21 includes the optical receiver 5
a and 5b and a differential receiver 6. Optical receiver 5
a and 5b reconvert the differential optical signals transmitted by the optical fibers 4a and 4b into differential electrical signals 11a and 11b. The differential receiver 6 has a hysteresis characteristic and converts the differential electric signals 11a and 11b into digital received electric signals 12a.
Return to The receiving unit 7 receives a digital received electric signal 12 from the differential receiver 6.

FIG. 2 is a diagram showing the relationship between a differential electric signal input to a differential receiver having hysteresis characteristics and a received electric signal output from the differential receiver. In the figure, the horizontal axis indicates the voltage of the difference between the differential electric signals 11a and 11b, and the + direction indicates that the signal 11a is higher in voltage than the signal 11b. The vertical axis indicates the logical level of the received electric signal 12. A graph 22 shows the relationship between the differential electric signals 11a and 11b and the received electric signal 12 of the differential receiver 6 having the hysteresis characteristic.

Differential receiver 6 having hysteresis characteristics
Then, as shown in FIG. 2, even if the differential electric signal 11a becomes higher in voltage than the differential electric signal 11b, the received electric signal 12 output from the differential receiver 6 immediately becomes the logical level "1". Instead, when the difference between the differential electrical signals 11a and 11b exceeds a certain voltage ΔV, the logic level becomes “1”. Similarly, the differential electric signal 11a is
As soon as the lower voltage is reached, the received electrical signal 12 does not go to the logic level "0" and the differential electrical signals 11b and 11a
When the difference exceeds a certain voltage −ΔV, the logic level becomes “0”.

FIGS. 3A and 3B are timing charts of the apparatus shown in FIG. 1. FIG. 3A shows a transmission signal 10, FIG. 3B shows differential electric signals 11a and 11b, and FIG. An electrical signal 12 is shown. 1 and 3, the transmission electric signal 10 of the transmission unit 1 is represented by a waveform 101.
Is a specific example. As shown in FIG. 3B, the differential electric signals 11a and 11b have the waveform 102a and the waveform 1
Even when noise is included at the time of rising and falling as in 02b, the received electric signal 12 of the differential receiver 6 having the hysteresis characteristic is once the logical level changes from "0" to "1". The logic level does not return to "0" unless the voltage difference between the differential electric signal 11b and the differential electric signal 11a exceeds a certain voltage (-.DELTA.V). Similarly, once the received electric signal 12 changes from the logical level “1” to “0”,
The logic level does not return to “1” unless the voltage difference between the differential electric signal 11a and the differential electric signal 11b exceeds a certain voltage (ΔV).

For this reason, as shown in FIG. 3C, the received electric signal 12 can be a signal containing no noise such as the waveform 105. Similarly, the differential electric signals 11a,
Even if 11b contains noise other than at the time of rising and falling, a received electric signal 12 containing no noise is obtained unless the voltage difference between the differential electric signals 11a and 11b is changed until the logic level of the differential receiver 6 is changed. be able to. Further, as shown in FIG. 3C, the hysteresis characteristic of the differential receiver 6 has a characteristic that the bit stream of the digital electric signal can be smoothly re-converted. Optical signals can be reconverted to digital electrical signals without delay.

In the above-described embodiment, the case where an optical fiber is used as a means for transmitting an optical signal has been described as an example. However, the present invention is not limited to this. For example, an optical transmission means other than an optical fiber may be used.

[0021]

According to the optical information transmission apparatus of the first aspect of the present invention, since the differential optical signal is reconverted into the digital electric signal by using the electric signal reconverting means having the hysteresis characteristic, the optical receiver is required Even if the output differential optical signal contains noise and jitter, it is possible to eliminate the noise of the digital electric signal output from the electric signal reconverting means and input to the receiving unit. Further, according to the optical information receiving apparatus of claim 5 of the present invention, the differential optical signal converted from the digital electric signal is received from the optical transmission line, and the differential optical signal is re-converted into the digital electric signal. In the optical information receiving apparatus for receiving by the receiving unit, the means for re-converting the digital electric signal has a hysteresis characteristic, so that the re-converted digital electric signal is not mixed with jitter or the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical information transmission device according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between input and output signals of a differential receiver having hysteresis characteristics.

FIG. 3 is a timing chart in the embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional optical information transmission device.

FIG. 5 is a configuration diagram of another conventional optical information transmission device.

FIG. 6 is a timing chart in another conventional optical information transmission.

[Explanation of symbols]

1: Transmission unit 2: Differential driver 3, 3a, 3b: Optical transmitter 4, 4a, 4b: Optical fiber 5, 5a, 5b: Optical receiver 6: Differential receiver 7: Receiving unit 8: Comparator 9: Conventional Of differential receiver 10: Transmission electric signal 11: Electric signal as output of optical receiver 11a, 11b: Differential electric signal as output of optical receiver 12: Received electric signal 13a, 13b: Output of differential driver A certain differential electric signal 20: Differential optical signal conversion means 21: Electric signal re-conversion means 22: Relationship between a transmission electric signal input to a differential receiver having hysteresis characteristics and a reception electric signal output from the differential receiver 101 : Waveform example of the transmission signal 10 102a, 102b: Output waveforms of the optical receivers 5a and 5b containing noise at the rise and fall 103: Output of the differential receiver 9 Waveform 104: Output noise of differential receiver 9 105: Output waveform of differential receiver 6 having hysteresis characteristics

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Claims (5)

[Claims] 1. A means for converting a digital electric signal from a transmission unit into a differential optical signal; a means for transmitting the differential optical signal from an optical transmitter to an optical receiver; Means for re-converting to a signal, wherein the optical information transmission apparatus receives the re-converted digital electric signal at a receiving unit, wherein the means for re-converting to an electric signal has a hysteresis characteristic. Optical information transmission device. 2. The apparatus according to claim 1, wherein said means for converting to a differential optical signal has a differential driver and an optical transmitter, and said electric signal re-conversion means has an optical receiver and a differential receiver. An optical information transmission device according to claim 1. 3. The optical information transmission apparatus according to claim 2, wherein the hysteresis characteristic of the differential receiver is a characteristic that enables a bit stream of the digital electric signal to be smoothly converted. 4. The hysteresis characteristic of the differential receiver reduces noise caused by the asymmetry of the rising characteristic and the falling characteristic of at least one of the means for converting to a differential optical signal and the means for reconverting to an electric signal. The optical information transmission device according to claim 3, wherein: 5. A re-converted digital signal, comprising: means for receiving a differential optical signal converted from a digital electric signal from an optical transmission line; and means for re-converting the differential optical signal into a digital electric signal. An optical information receiving apparatus for receiving an electric signal in a receiving unit, wherein the means for reconverting the electric signal into an electric signal has a hysteresis characteristic.