JPH02111127A - Driving controller for light emitting element - Google Patents

Abstract

PURPOSE:To attain stable transmission accuracy of an optical signal by splitting the band of an input data signal, amplifying its high frequency component at a broad band AC amplifier, amplifying its low frequency component at a narrow band DC amplifier, synthesizing the band of both the amplifier outputs and supplying the result to a light emitting element as a drive signal. CONSTITUTION:An input data signal is fed to a band splitter 22 comprising an LC filter. Then a signal of a high frequency component from the band splitter from 22 is fed to a broad band AC amplifier 23 and amplified. Moreover, a signal of a low frequency component is fed to a narrow band DC amplifier 24 and amplified. Then an output signal of a high frequency component from the broad band AC amplifier 23 and an output signal from the narrow band DC amplifier 25 are fed to band synthesizer 26, in which both the output signals are synthesized and the resulting signal is fed to a light emitting element 27 comprising a semiconductor laser as drive signal. Thus, since the broad band pulse amplifier amplifying and processing the input data is constituted by an AC amplifier, the constitution is simplified and the stable operating state is obtained against the temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Field of Industrial Application) The present invention relates to a drive control device for a semiconductor light emitting element used for optical communication using an optical cable.

(Prior art) The information transmission speed in optical communications has been increasing rapidly in recent years, and in such cases, it has become a problem to widen the bandwidth of drive circuits for light emitting elements made up of semiconductor lasers, which are key devices in optical communications. It becomes.

Conventionally, such a semiconductor laser drive circuit is
For example, it is configured as shown in FIG.

That is, a manual data signal consisting of an electrical pulse signal from an input terminal 11 is amplified by a broadband direct current (DC) amplifier 12 and converted into a current pulse signal, and this pulse signal is used to generate a 4M light emitting cord 13 formed by a semiconductor laser. to drive.

Here, it is necessary to supply a bias current to the light emitting element 13, and the bias current is supplied from the bias current source 15 through the inductor 14 to the threshold value of the semiconductor laser constituting the light emitting element 13. I have to.

Furthermore, a semiconductor laser has the property that its optical output fluctuates depending on the temperature. Therefore, a light receiving element iG consisting of a photodiode, etc. for the above-mentioned camera monitor is set, and this light receiving element 16 detects light from the light emitting element 13. The light output of the light emitting element 13 is monitored. The data input is also supplied to a low-pass filter 17, which detects the mark rate of the input signal. Then, the mark rate detected by the filter 17 and the monitor output detected by the light receiving element 16 are compared by a comparator 18, and the bias current source 15 is controlled by this comparison output, and the light from the light emitting element 13 is controlled. Ensure that the output is stabilized.

However, as the transmission speed of optical communication increases,
A problem arises in that the circuit configuration of the wideband DC amplifier 12 becomes complicated. In addition, due to temperature fluctuations, the broadband DC amplifier 12
The amplitude of the output pulse signal fluctuates, which poses a problem that affects the light emission characteristics of the light emitting element 13.

(Problems to be Solved by the Invention) This invention solves the problem that even when the transmission speed of optical communication increases as described above, the circuit configuration becomes complicated and the light emitting element of the light emitting element is affected by temperature fluctuation. This was done to solve the problem, and it can easily simplify the configuration of amplifier circuits, etc., and it can also easily and reliably suppress fluctuations in pulse current due to temperature changes, improving reliability. It is an object of the present invention to provide a drive control circuit for a light emitting element that facilitates information transmission in high-performance optical communications.

[Structure of the Invention] (Means for Solving the Problems) In the drive control device for a light emitting element according to the present invention,
The input data signal is band-separated by a band separation means, the high frequency component of the input data signal is amplified by a wideband 1/evening current amplifier, and the low frequency component is amplified by a narrowband [direct current amplifier], and the above amplified outputs are 1F 1y-i and supply it to the light emitting element as a drive signal]. Also, the monitor output of the light emitting element is 4! above! The comparison output and a reference voltage corresponding to a set bias current are supplied to the narrow band amplifier.

(Function) In the light emitting element drive control device configured as described above, the high frequency component of the data input signal is amplified by the wide range AC amplifier. Compared to a DC amplifier, the configuration of this amplifier section does not require, for example, a DC coupling configuration for the internal circuit, so the configuration can be made sufficiently simple. Further, by using such an AC amplifier, it becomes easy to reduce fluctuations in the output pulse amplitude due to temperature fluctuations, which is effective in stabilizing the transmission accuracy of optical signals.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows its configuration, in which the data input terminal 21
The human input data signal is supplied to a band separator 22, which is an LC filter constituted by an inductor LL and a capacitor C1, and is separated into a high frequency component signal and a low frequency component signal. The high frequency component signal from the band separator 22 is then supplied to a wideband alternating current (AC) amplifier 23 for amplification. Further, the low frequency component signal from the band separator 22 is supplied to an adder 24, and the output signal from the adder 24 is a narrow band DC amplifier set to have the same gain as the wide band AC amplifier 23. (DC) is supplied to the amplifier 25 and amplified.

Here, the output signal waveform from the broadband AC amplifier 23 is as shown in FIG. 2A, for example, and this waveform is a signal that does not have a DC component. The low frequency component signal from the band separator 22 becomes the mark rate component of the input data signal, as shown by the broken line in FIG. 2(B). The narrowband DC amplifier 25 amplifies the mark rate component.

The high frequency component output signal from the wideband AC amplifier 23 is supplied to a band synthesizer 2G constituted by an LC filter including an inductor L2 and a capacitor C2, and the output signal from the narrowband DC amplifier 25 is further supplied to the band synthesizer 2G. 26 to combine the two-sided force signals. The combined output signal from the band synthesizer 26 is a signal in which even the DC component is amplified, and this signal is supplied as a drive signal to the light emitting element 27 made of a semiconductor laser.

Here, the semiconductor laser requires a bias current to flow close to a threshold value, and the reference power supply 28 is set for this purpose. Then, the voltage v set by this reference power supply 28
b is supplied to the adder 24 and narrowband DC amplifier 25
A signal as shown by the solid line in FIG. 2(B) is supplied to
The light emitting element 27 is driven by a signal as shown in FIG. 2(C).

The optical signal generated by the light emitting element 27 is received by a monitoring light receiving element 29 composed of a photodiode, so that a monitor signal can be obtained.

The monitor signal detected by this light receiving element 29 is
A comparator 30 is provided. The comparator 30 is supplied with the low frequency component output signal of the band separator 22 as a comparison signal, and the output signal from the comparator 30 is further supplied to the adder 24 as an addition signal.

That is, the optical output from the light emitting element 27 is automatically stabilized without depending on the mark rate included in the signal component.

Incidentally, in the above embodiment, the band separator 22 and the band synthesizer 26 are each constructed by an LC filter, but this is not limited to the LC filter, and may be applied to other circuits (
It is also good depending on the composition.

[Effects of the Invention] As described above, according to the light emitting element drive control device according to the present invention, a wideband pulse amplifier that amplifies input data can be configured with an AC amplifier. Therefore, even if the data transmission speed is significantly increased, the configuration can be easily simplified.
Moreover, stable operating conditions can be obtained even with temperature changes, and high reliability can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram illustrating a light emitting element drive control device according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram illustrating the operation of the above embodiment, and FIG. 3 is a conventional drive control device. FIG. 2 is a configuration diagram illustrating an example of a circuit. 22...Band separator, 23...Broadband alternating current (AC)
Amplifier, 24...Adder, 25...Narrowband DC (D
C) Amplifier, 26...Band synthesizer, 27...Light emitting element (semiconductor laser), 28...4 power supplies, 29...
Monitor light receiving element, 30... comparator. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) Band separation means to which a data input signal is supplied and separates it into a high frequency component signal and a low frequency component signal, and a high frequency component signal separated by this band separation means is supplied. A wideband AC amplifier, a narrowband DC amplifier that amplifies the low frequency component signal from the band separation means, and output signals from each of the wideband AC amplifier and narrowband DC amplifier are supplied, and a light emission driving signal is supplied to the light emitting element. a monitoring light-receiving element that receives light from the light-emitting element; and comparing the monitor signal from the light-receiving element with the low frequency component signal from the band separation means. Comparing means, a reference power source for biasing the light emitting element, and adding means for adding and synthesizing the voltage signal from the reference power source, the output from the comparing means, and the low frequency component from the band separating means. A drive control device for a light emitting element, characterized in that the narrowband DC amplifier is supplied with a signal from the adding means. (2) The drive control device for a light emitting element according to claim 1, wherein the band separation means and the band synthesis means are each constituted by a filter circuit consisting of an inductor and a capacitor.