JPH0456431A - Feedback control optical communication equipment - Google Patents

Abstract

PURPOSE:To facilitate the adjustment for the dispersion in a light emitting element by transferring optical reception level information measured by a reception section to a transmission section and controlling the optical transmission level automatically so that the optical reception level reaches a prescribed range. CONSTITUTION:An optical signal is sent from a transmission section 1 to a reception section 2 through an optical fiber 18. An optical level sensor section 16 smoothes a branched optical signal 15 to measure the resulting level to calculate a reception optical signal 9 from the measured value. The calculated data is coded by a feedback transfer section 17 and transferred to an optical output level control section 8 as optical reception level information 7 to control the optical output level of a light emitting element 5. When the signal 9 exceeds an upper limit reference value as the operation of the entire system, the system controls the optical output level to be decreased. Furthermore, when the received optical signal 9 is lower than the lower limit reference value, the system controls the level so as to be increased. The upper and lower limit reference values are adjusted by the feedback transfer section 17.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a feedback control optical communication device, and in particular to a feedback control optical communication device that controls the optical output level according to the optical reception level received at the receiving section and always maintains the optical reception level within a certain range. The present invention relates to a feedback control optical communication device.

[Conventional technology]

Conventionally, in optical communication equipment, the optical output level is fixed at a constant level, and the optical reception level of the receiving section is set within a range to compensate for level fluctuations due to the length of the optical fiber, temperature, aging, etc. We have responded. An optical attenuator was installed when the optical reception level was higher than the optical reception level of the receiver. Also, if the level was lower than the optical reception level, a repeater was installed in the middle.

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

The conventional optical communication device connects the transmitter 1a via the optical fiber 18.
The transmitting unit 1a has a light emitting element 5 that emits a multiplication power signal 4, a driving circuit 6 that receives an input signal and converts it into a transmitting electric signal 3 that drives the light emitting element 5, and a transmitting unit 1a. The receiver 2a includes a light output level adjuster 19 that adjusts the level of the optical signal 4, while the receiver 2a includes a light receiving element 13 that converts the received optical signal 9 received via the optical fiber 18 into a received electrical signal 12; It was configured to include an amplifier circuit 14 that amplifies the received electrical signal 12 and outputs it as an output signal, and was used under the above-mentioned operating conditions.

[Problem to be solved by the invention]

The conventional optical communication device described above mainly has the following three drawbacks.

The first problem is that there are variations in the light output level of the light emitting elements. Light emitting elements have very large variations in the correspondence between optical output level and drive current, and conventionally it took time to adjust the optical output level. Another drawback is that it is very difficult to make complete adjustments, and the standard has to have a wide range.

The second problem is that the dynamic range of conventional optical communication devices is determined by the capability of the first-stage amplifier circuit of the receiving section. The optical reception level of optical communication equipment depends on temperature, aging,
Since it changes due to an increase in fiber loss due to splicing, etc., it is necessary to consider these margins when determining the optical reception level. For this reason, since a part of the optical receivable level range is considered as a margin, the actual optical receivable level range becomes narrower and the transmission distance of the optical signal becomes shorter.

Third, it is difficult to predict the optical reception level. Normally, before installation of optical communication equipment, the system is designed and it is considered whether there are any problems with the transmission distance of optical signals. If the transmission distance was too short, an optical attenuator was installed. Also, if the transmission distance was too long, a repeater was inserted in the middle. However, these studies are conducted using standard values for each factor, so when the equipment is actually installed, there may be a large difference between the study values and the actual measured values. Therefore, there are disadvantages in that it is inevitable to install unnecessary intermediate relay devices and to run out of optical attenuators.

[Means to solve the problem]

The feedback control optical communication device of the present invention includes a light emitting element that modulates a transmitted electrical signal into a transmitted optical signal, a drive circuit that drives this light emitting element, and a light receiving level of the transmitted optical signal sent out via an optical fiber. a transmitter having an optical output level controller that controls the optical output level of the light emitting element so as to maintain the optical output level within a range; a half mirror that transmits and branches a received optical signal received via the optical fiber; - a light receiving element that demodulates the transmitted light signal transmitted through the half mirror into a received electrical signal; a light level sensor section that measures the light reception level based on the branched light signal branched by the half mirror; and a receiving section having a feedback transmission section that feeds back optical reception level information to the optical output level control section of the transmitting section.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. The configuration of the embodiment shown in FIG. 1 consists of a transmitting section 1 and a receiving section 2.

The transmitting section 1 includes a light emitting element 5 that modulates a transmitted electrical signal 3 into a transmitted optical signal 4, a drive circuit 6 that drives the light emitting element 5, and a light receiving level information 7 received from the receiving section 2.
and a light output level control section 8 for controlling the light output level of the light source.

On the other hand, the receiving section 2 includes a half mirror that branches the received optical signal 9.
10, a light receiving element 13 that demodulates the transmitted optical signal 11 that has passed through the half mirror 10 into a received electrical signal 12, and an amplifier circuit 14 that amplifies and waveforms the received electrical signal 12.
It comprises an optical level sensor section 16 that measures the optical reception level from the branched optical signal 15 branched by the half mirror 10, and a feedback transfer section 17 that transfers the measured optical reception level information 7 to the optical output level control section 8.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

Optical fiber 1 is used to transmit optical signals from transmitter 1 to receiver 2.
8 is used, but aerial propagation is also possible depending on operational conditions. In the case of a bidirectional optical communication device, the optical reception level information 7 transferred from the receiving section 2 to the transmitting section is carried on surplus bits of the reverse direction signal. In the case of a one-way optical communication device, a separate transfer means is required.

The ratio of the optical signal 11 passing through the half mirror 10 to the optical signal branching 15 is approximately 10:1.20:1, and a small portion of the received optical signal is used for measuring the optical reception level.

The optical level sensor section 16 smoothes the branched optical signal 15, measures the level, and calculates the received optical signal 9 from this measured value. The calculated take is encoded in the feedback transfer unit 17,
The signal is transferred as optical reception level information 7 to the optical output level control section 8, and the optical output level of the light emitting element 5 is controlled.

As for the operation of the entire system, when the received optical signal 9 exceeds the upper limit reference value, control is performed to lower the optical output level. Further, when the received optical signal 9 falls below the lower limit reference value, control is performed to increase the optical output level. The upper limit reference value and the lower limit reference value can be adjusted by the feedback transfer section 17. Therefore, it is also possible to manually change the optical output level on the transmitting side from the receiving side.

In this way, by controlling the optical transmission level based on the optical reception level information, variations in light emitting elements can be largely absorbed. In general, light emitting elements have large variations, and it is a time-consuming task to adjust each device one by one when the device is shipped. However, in this example,
Since it has an automatic adjustment mechanism, the adjustment of the light-emitting element no longer requires the same precision as in the past, making shipping adjustment much easier.

Furthermore, the dynamic range of the device can be made significantly wider than before. In conventional optical communication devices, the receiving section has a dynamic range. However, the dynamic range of the receiving section is limited to the noise level of the first stage amplifier circuit.
It was determined by abilities such as saturation level. However, in this embodiment, the dynamic range of the device is the sum of the dynamic range of the receiving section and the variable range of the light output level control section of the light emitting element of the transmitting signal, so the overall dynamic range is significantly wider than that of the conventional device. Therefore, the transmission distance of the optical signal can be increased, and the margin of the receiving section can be increased accordingly.

Furthermore, it becomes easier to predict the optical reception level during system design. Conventionally, when designing a system, the transmission distance of an optical signal has been examined based on the standard values for each factor, so there have been cases where the examined value and the actual measured value differ greatly. However, in this embodiment, since the optical reception level is measured and the optical transmission level is controlled, it is also possible to absorb the difference between the considered value and the actual measurement value.

[Effects of the Invention] As explained above, the present invention transfers the optical reception level information measured by the receiving section to the transmitting section, and automatically controls the optical transmission level so that the optical reception level is within a certain range. This makes it extremely easy to adjust for variations in the light emitting elements, greatly increases the dynamic range of the device and the margin of the receiver, and also makes it much easier to predict the optical reception level during system design. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional optical communication device. DESCRIPTION OF SYMBOLS 1... Transmission part, 2... Receiving part, 3... Transmission electric signal, 4... Transmission optical signal, 5... Light emitting element, 6...
Drive circuit, 7... Optical reception level information, 8... Optical output level control section, 9... Received optical signal, 10... Half mirror 111... Passing optical signal, 12... Received electricity Signal, 13... Light receiving element, 14... Amplifying circuit, 15.
・Branch optical signal, 16 ・Light level sensor section, 17
...Return transfer section, 18...Optical fiber, 19...
・Light output level adjustment section.

Claims (1)

[Claims] A light emitting element that modulates a transmitted electrical signal into a transmitted optical signal, a drive circuit that drives this light emitting element, and a light emitting element that maintains a light reception level of the transmitted optical signal sent out via an optical fiber within a predetermined range. a transmitting unit having an optical output level control unit that controls the optical output level of the optical fiber; a half mirror that transmits and branches the received optical signal received via the optical fiber; a light receiving element that demodulates the signals; a light level sensor section that measures the light reception level based on the branched optical signal branched by the half mirror; and a light reception level information measured by the light level sensor section that is transmitted to the transmitter. 1. A feedback control optical communication device comprising: a receiving section having a feedback transmission section that feeds feedback to an optical output level control section.