JPS61285834A - Optical transmission and reception equipment - Google Patents

Abstract

PURPOSE:To control the transmission state in response to the reception state by allowing a transmission/reception equipment itself to apply a reception output from a reception section as a comparison setting value for APC of a transmission section. CONSTITUTION:Level detectors 19A, 29A are provided and amplifiers (main amplifiers) 29, 19 are provided in place of an AGC circuit to eliminate the need for a pad 4. On the other hand, the amplifier 19 is provided in place of the AGC circuit. The AGC circuit is excluded because the transmission power is controlled at the sending side through the level detector 19A. Since the level of the reception output by a reception section 1B is supervised and the reception level is set as the threshold level of the APC circuit 13, the transmission output is controlled in response to the reception level and since a negative feedback path comprised of transmission section 1A optical fiber 3 reception section 2A transmission section 2B optical fiber 3 reception section 1B transmission section 1A is formed, the entire system is stabilized.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to an optical transmitter/receiver.

[Prior art]

Conventional optical transmitter/receiver equipment includes ``Practical 45-Mbit/s Regenerator Lightwave Transmission J (Practica145-
Mb/s Regenerator for Light
Twave Transmission) (BSTJ,
Vol, 57. No, 6. July-August 197
8th year, P.

1837-1856).

FIG. 4 is a diagram that collectively shows this conventional example.

The optical transceiver device consists of a transceiver 1 and a transceiver 2.
Both communicate via optical fiber 3.

The transceiver 1 consists of a transmitting section IA and a receiving section IB, and the transceiver 2 consists of a receiving section 2A and a transmitting section 2B.

The transmitting sections IA and 2B have the same configuration, including a laser diode drive circuit 10.24 and a laser diode 11.25.
Optical monitor circuit 12.26, automatic power control circuit (APC)
It consists of 13, 27, and comparison setting device (voltage setting device) 14.28.

The receiving section IB and the other two have the same configuration, and consist of a light receiving diode 15.20, a preamplifier 16.21, an AGC amplifier 17.22, and an AGC feedback section 18.23.

The operation of this configuration is as follows.

Upon receiving the transmission signal, the drive circuit 10 drives the laser diode 1
1 and sends out the transmission output to fiber 3. Generally, the laser diode 11 has a high light emission output, and if a laser diode with relatively low reliability is used, variations in output will occur. Therefore, a pad (
Attenuator) 4 is provided.

The receiving output by the receiving section 2A is leveled.

In the receiving section 2A, the output of the optical fiber 3 is received by a light receiving diode 20, firstly amplified by a preamplifier 21, and then sent to an AG.
The C circuit 22 applies AGC to obtain a stable reception output.

On the other hand, in order to obtain stable laser output, the transmitter LA
The monitor circuit 12 detects the light emission output, and the drive signal of the drive circuit 10 is adjusted via the APC 13.

The comparison setter 14 is provided to the APC 13 for setting an output threshold level.

The operation between the transmitter 2B and the receiver IB is also the same.

In such a conventional example, a pad 4 had to be inserted into the path of the optical fiber 3. The reason for inserting the pad is
In addition to the above-mentioned reasons, when the yarn path of the optical fiber 3 is short,
This is also to prevent the amount of light input to the light receiving diode 20 from increasing.

In addition, since the level of the comparison setting device 14 is fixed, it is difficult to perform APC control according to the output of the laser diode and the reception capability of the photodetector diode. The present invention provides an optical transmitting/receiving circuit that can control the transmission state depending on the state.

[Summary of the invention]

Optical transmitter/receiver circuits using laser diodes have a fairly wide optical dynamic range, and at high input levels, the preamplifier will become saturated. In order to configure an AGC amplifier with a wide dynamic range, there are problems such as a complicated circuit, a need for a large power supply voltage, and a large scale that cannot be miniaturized.

Even if it is corrected with a pad, maintainability is poor. Moreover, unnecessary current is constantly passed through the laser diode, shortening its lifespan.

Therefore, in order to deal with this problem on the transmitting side rather than on the light receiving side, we decided to have the transmitter/receiver itself supply the received output from the receiving section as a comparative setting value for APC of the transmitting section.

[Embodiments of the invention]

FIG. 1 shows an embodiment of an optical transmitter/receiver according to the present invention. The features of this embodiment include the provision of level detectors 19A and 29A, and the use of an amplifier (main amplifier) instead of the AGC circuit.
It is characterized by the provision of 29.19 and the elimination of the need for pad 4.

An embodiment of the APC circuit 13 (27) is shown in FIG. AP
The C circuit 13 includes a preamplifier 13A and a clamp circuit 13B.
It consists of a low pass filter (LPF) 13C, an amplifier 13D, and a feedback resistor 13E. The preamplifier 13A amplifies the received output received by the monitor circuit (2). Clamp circuit 13
In B, levels above a certain value are clamped.

LPF13C smoothes this clamp output.

Obtain a DC level signal. The amplifier 130 is a differential amplifier, and has the output of the LPF 13G and the level detector 19A.
Take the difference with the output of . The level detected by this level detector 19A is the output level of the amplifier 19.

The differential output thus obtained becomes a constant current source for the drive circuit 10. This constant current source causes a constant current corresponding to the differential output to flow through the laser diode 11 to emit light.

On the other hand, in this embodiment, instead of the AGC circuit 17, the amplifier 1
9 was set. The reason why the AGC circuit 17 could be eliminated is that the transmitted power can now be controlled through the level detector 19A on the transmitting side.

The level detector 19A has different detection levels depending on the transmission format. If the transmission format is the NRZ method shown in FIG. 3(a), peak detection is performed. According to the transmission format using the CMI method shown in FIG. 3(b), the CM engineering mean value level is detected.

According to this embodiment, the level of the reception output by the receiver IB is monitored, and this reception level is set as the threshold level of the APC circuit 13. As a result, it was possible to control the transmission output according to the reception level.

Furthermore, according to this embodiment, the current flowing through the laser diode can always be kept in an optimal state, so the output of the laser diode is stabilized. For example, if the transmission loss is less than 5 dB L, but the optimal light reception level is 125 dB, and the output is 15 dB, not only will a 15 dB batt be required, but a large output will be imposed on the laser diode, reducing reliability. It turns out. In this embodiment, this problem is eliminated.

Furthermore, since the output of the laser diode is controlled, saturation of the receiving side preamplifier cannot occur, so the AGC circuit is not needed and a normal amplifier can be used instead.

Furthermore, according to this embodiment, a negative feedback path of transmitting part IA → optical fiber 3 → receiving part 2A → transmitting part 2B → optical fiber 3 → receiving part IB → transmitting part IA was formed, so that the entire system was stabilized. I was able to measure.

Incidentally, for the level detector 19A, a reference level Vr is determined in advance, and a variation ΔV of the reception detection level of the level detector 19A is superimposed on this reference level Vr to obtain Vr±ΔV, and this Vr±ΔV is It may also be used as an input to the APC circuit 13.

This embodiment is preferably applied to a circuit configuration in which the transmitting section IA and the receiving section IB are formed on one circuit board.

〔Effect of the invention〕

According to the present invention, the transmission output can be adjusted based on the reception input.

[Brief explanation of drawings]

Figure 1 is an embodiment of the optical transmitter/receiver circuit of the present invention, and Figure 2 is A
FIG. 3 is a diagram showing an example of level detection, and FIG. 4 is a diagram showing a conventional optical transmitting/receiving circuit. 1.2... Transmission/reception circuit, 3... Optical fiber, IA,
2B... Transmission section, 18. 2A... Receiving section, 19.
29... Main amplifier, 19A, 29A... Level detector, 13.27... APC (automatic power controller)
. Agent Patent Attorney Tadashi Akimoto Figure 2 Figure 3

Claims (1)

[Claims] 1. The transmitting section of the first optical transceiver and the receiving section of the second optical transceiver are coupled by an optical fiber, and the transmitting section of the second optical transceiver and the first optical transceiver In an optical transmitter/receiver device, the transmitter of the first and second optical transceivers is coupled to a receiving section of the optical transceiver via an optical fiber, and the first and second optical transceivers perform optical communication via the optical fiber. are a drive circuit that drives a laser diode according to a transmission signal, a laser diode driven by the drive circuit, a monitoring circuit that monitors the output of the laser diode, and an output of the monitoring circuit and an external threshold value. an automatic power controller that outputs a direct current level according to the difference therebetween, and means for making the constant current source of the laser diode drive circuit variable by the automatic power controller, and the external threshold value is An optical transmitting/receiving device in which the first transmitting/receiving device is set by the receiving level of its own receiving section, and the second transmitting/receiving device is set by the receiving level of its own receiving section. 2. The optical transmitting/receiving device according to claim 1, wherein when the transmission format of the transmission signal is a CMI method, the reception level of the receiving section is an average level. 3. The optical transmitting/receiving device according to claim 1, wherein when the transmission format of the transmission signal is an NRZ system, the reception level of the receiving section is a peak level.