JPH0491525A - Bi-directional optical communication system - Google Patents

Abstract

PURPOSE:To improve the S/N of this system by adding a branched part of signals inputted to a transmitter to signals received by a receiver as a neutralization signal after adjustment. CONSTITUTION:Transmitted signal DATA-IN is supplied to an LED drive circuit 2 through an input buffer l and transmitted to a transmission circuit after the electric signal is converted into signal light by means of a light source 3. The signal light made incident to a photoreceptor element 4, on the other hand, is converted into electric signals. The converted electric signal is led to a differential amplifier 6 after the signal is amplified by means of an amplifier 5. Thereafter, received signal DATA-OUT is obtained from a waveform reproduction circuit 7 through an output buffer 8. In addition, part of the output of the input buffer l is supplied to the differential amplifier 6 as a neutralization signal after its damping quantity and delay time are adjusted by means of an attenuation circuit 9 and delay circuit 10. The damping quantity and delay time by means of the circuits 9 and 10 are made adjustable and adjusted in advance so that the neutralization signal can become the same as a reflected signal component reflected in a transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to optical communication, and particularly to a bidirectional optical communication system configured by combining an optical digital link and an optical branching device.

(Prior Art) FIG. 3 is a configuration diagram for explaining an example of a conventional bidirectional optical communication system configured by combining an optical digital link and an optical branching device. In the figure, 12°15 is a transmitter using an LED (light emitting diode) or LD (laser diode) as a light source, 13.16 is a receiver having a light receiving element such as a photodiode, 14.17 is an optical splitter, and 18 is a It is an optical transmission line.

Transmitter 12. The receiver 13 constitutes an optical digital link on the A side, and the transmitter 15 . The receiver 16 constitutes a B-side optical digital link.

The signal light DATA1 transmitted from the A-side transmitter 12 is
The signal is transmitted to the optical fiber transmission line 18 via the optical branching device 14 and received by the receiver 16 on the B side.

The signal light DATA2 transmitted from the B-side transmitter 15 also
The signal lights are similarly sent to the receiver 13 on the A side, but the wavelengths of these signal lights are the same. In this case, optical fiber transmission line 1
8, it is assumed that there is a location where light is reflected at the position indicated by point P. Then, the signal light DAT from the transmitter 12 on the A side
A portion of the AI is reflected at the reflection point P. Therefore, A
The receiver 13 on the side receives the signal light D from the transmitter 15 on the B side.
The reflected light at point P of the signal light DATAI is superimposed on ATA2 and received. As a result, the S/N ratio of the input signal light in the A-side receiver deteriorates, and the code error rate of the output data of the receiver deteriorates. The S/N ratio of the receiver input signal on the B side is similarly degraded. Such a reflection point P is caused by a connector connection point or the like.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and has a simple configuration that suppresses reflected signal components in received signals and provides bidirectional optical communication with a good S/N ratio. The purpose is to provide a method.

(Means for Solving the Problems) The present invention provides a two-way optical communication system using light of the same wavelength, which is configured by combining an optical digital link including a transmitter and a receiver, and an optical branching device. The method is characterized in that a part of the signal input to the receiver is adjusted and added as a neutralization signal to the signal received by the receiver.

(Function) The present invention provides a two-way optical communication system using light of the same wavelength, which is configured by combining an optical digital link including a transmitter and a receiver, and an optical branching device. By branching a part of the S /N ratio can be improved.

A neutralized signal from the transmitter can be obtained by adjusting the amplitude and delay time of a portion of the signal input to the transmitter using an attenuation circuit and a delay circuit.

(Embodiment) FIG. 1 is a block diagram of an optical digital link used in a bidirectional optical communication system according to an embodiment of the present invention. In the figure, 1
is a large capacitor, 2 is an LED drive circuit, 3 is a light source such as an LED, 4 is a light receiving element such as a photodiode, 5 is a preamplifier, 6 is a differential amplifier, 7 is a waveform regeneration circuit, 8 is an output buffer, and 9 is attenuation. The circuit 10 is a delay circuit. T surrounded by dotted lines is a part that operates as a transmitter, and R is a part that operates as a receiver.

The signal DATA-IN to be transmitted is given to the LED drive circuit 2 via a large buffer, and the electrical signal is converted into signal light by a light source 3 such as an LED, and is transmitted toward the transmission circuit. On the other hand, the signal light incident on the light receiving element 4 such as a photodiode is converted into an electric signal and sent to the preamplifier 5.
is amplified by the differential amplifier 6, and is then amplified by the waveform reproducing circuit 7.
The received signal DATA-OUT is sent from the output buffer 8 through the output buffer 8.
is obtained. Also, part of the pressure of the large capabuae is absorbed by the damping circuit 9. The attenuation amount and delay time are adjusted by the delay circuit 10 and provided to the differential amplifier 6 as a neutralization signal.

Here, attenuation circuit 9. If the amount of attenuation and delay time in the delay circuit 10 are adjustable and DATA1 in FIG. 3 is adjusted to be equal to the reflected signal component reflected from the reflection point P, the reflected Wave components can be sufficiently suppressed.

Furthermore, if a plurality of attenuation circuits 9 and delay circuits 10 are provided and connected in parallel so that the attenuation amount and delay time of each can be set independently, there will be multiple reflection points and multiple reflections will occur. It is also possible to deal with circuits such as

Since the adjustment amount of the adjustment circuit consisting of the attenuation circuit 9 and the delay circuit 10 described above differs depending on the terminal, a plurality of adjustment circuits are provided and the adjustment amount is adjusted in advance according to each terminal. At this time, by switching to an adjustment circuit compatible with the communication terminal, the reflected wave component can be suppressed more accurately.

FIG. 2 is a block diagram of an optical digital link used in a bidirectional optical communication system according to another embodiment of the present invention. Components similar to those in FIG. 1 are designated by the same reference numerals and their explanations will be omitted. In this embodiment, a control circuit 11 is provided,
The attenuation amount and delay time can be automatically adjusted. The control circuit 11 controls the attenuation circuit 9 and the delay circuit 10 according to the output of the differential amplifier 6. The operation of this circuit will be explained. A transmission path is connected to a terminal for communication, and the control circuit 11 is activated in a state where no signal is received from the other party. When the control circuit 11 controls the attenuation circuit 9 and the delay circuit 10 so that the pressure of the differential amplifier 6 is minimized, the reflected signal from the transmission path is canceled, so the control circuit By locking the attenuation circuit 11 and maintaining the attenuation amount and delay time of the attenuation circuit 9 and the delay circuit 10, the influence of reflected waves can be minimized in subsequent communications.

(Effects of the Invention) As is clear from the above description, according to the present invention, in a two-way communication system using the same wavelength, noise components due to reflected waves superimposed on signal light from the other party input to the receiver This has the effect of reducing the influence of , and improving the bit error rate of the receiver output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical digital link used in a bidirectional optical communication system according to an embodiment of the present invention, and FIG. 2 is a block diagram of an optical digital link used in a bidirectional optical communication system according to another embodiment of the present invention. A block diagram of a link, FIG. 3 is a configuration diagram for explaining an example of a conventional bidirectional optical communication system configured by combining an optical digital link and an optical branching device. 1... Large power buffer, 2... LED drive circuit, 3.
...LED, 4...light receiving element, 5...preamplifier,
6... Differential amplifier, 7... Waveform regeneration circuit, 8...
Output buffer, 9... Attenuation circuit, 10... Delay circuit, 11... Control circuit, P... Reflection point, T.
...Transmitter, R...Receiver. Patent Request University Shimadzu Corporation

Claims (1)

[Claims] In a bidirectional optical communication system using light of the same wavelength, which is configured by combining an optical digital link including a transmitter and a receiver, and an optical splitter, a part of the signal input to the transmitter is adjusted to A two-way optical communication system characterized by adding a neutralization signal to the signal received by a receiver.