JPH07288355A - Parallel e/o converter - Google Patents

Abstract

PURPOSE:To provide an n-channel parallel E/O converter that allows the transmission of data of optical signals containing DC components. CONSTITUTION:A parallel E/O converter consists of n pieces of laser diode drivers 3; n pieces of laser diodes 5, 6 having equivalent characteristics; an n-channel laser diode array 4; and a monitoring light receiving element 7. When a reference voltage VREF is inputted to a data signal input terminal 2, the light receiving element 7 monitors the luminous power outputted from one 6 of the laser diodes, and outputs a voltage proportional to the luminous power. In addition a comparator 8 is included. Fed with the reference voltage VREF and the output voltage of the monitoring light receiving element, the comparator 8 compares them, and inputs the differential output signal to the feedback signal input terminal 9 of each of the n laser diode drivers 3 to control the n laser diodes 5, 6. Reference voltage VREF is a voltage outputted from the monitoring light receiving element 7 when the clock signal input terminal 2 is fed with clock signals the marking ratio of which is always 50%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an E / O converter, and more particularly to a function for automatically adjusting light emission power.

[0002]

2. Description of the Related Art Since a conventional parallel E / O converter does not have a function of automatically adjusting the light emission power, it is necessary to limit the ability of the light emitting element or the operating environment.

When the conventional automatic light emission power adjusting circuit is used, the average value of the light emission power obtained by inputting the data signal is used as the feedback signal. The mark ratio becomes smaller than 50%, and the automatic light emission power adjusting circuit operates to increase the bias current value of the laser diode (hereinafter, referred to as LD) so that the light emitting power is increased. Further, when the light emission state is continued, the mark ratio of the average value of the light emission power becomes larger than 50%, the automatic light emission power adjustment circuit operates, and the bias current value of the LD is reduced.
The light emission power was adjusted to be small.

FIG. 4 is a diagram showing a relationship between a conventional input data signal, a feedback signal and a light emission power. As shown in FIG. 4, the feedback signal for controlling the bias current value of the LD is obtained from the average value of the emission power of the input data signal. Therefore, the feedback signal fluctuates due to the change of the mark ratio of the data signal, Bias current value fluctuates. Therefore, when a data signal having a continuous low level or high level is input, the light emission power is adjusted by the fluctuation of the bias current value of the LD, and the light emission power is not converted to the correct light emission power.

[0005]

SUMMARY OF THE INVENTION This conventional parallel E / O
In the converter, the emission power fluctuates due to external factors such as temperature fluctuations or power supply voltage fluctuations, which makes it difficult to design the optical transmission system or shortens the transmission distance. Also, the L of each channel arranged in parallel
When the automatic light emission power adjustment function is provided in D, the number of feedback circuits increases and a modulator is required. Further, in the case of using the conventional automatic light emission power adjustment circuit, the average value of the data signal is reflected in the feedback signal, so that a direct current (hereinafter, DC) such as a level signal is used.
When a data signal including a component is input, the bias current value changes and the emission or extinction state cannot be maintained, and the average value of the emission power is always output.

In view of such a point, an object of the present invention is to provide an n-channel parallel E / O converter capable of data transmission of an optical signal containing a DC component.

[0007]

A parallel E / O converter according to the present invention comprises n laser diode drivers arranged in parallel, each having a data signal input terminal and a feedback signal input terminal. The respective output signals of the laser diode drivers are used as input signals, and the current signals are driven by the data signals input to the data signal input terminals of the n laser diode drivers, respectively, and the n laser diode drivers are driven. Drive current can be adjusted by the feedback signal input to the feedback signal input terminal of, and n laser diodes having equivalent characteristics,
An n-channel laser diode array in which the n laser diodes are connected in an array;
A first laser diode driver among the laser diode drivers, and a first laser diode for inputting an output signal of the first laser diode driver,
In the case of the first channel, when a predetermined reference voltage is input to the data signal input terminal of the first laser diode driver, the light emission power output from the first laser diode is monitored, A monitor light-receiving element that outputs a voltage proportional to the light emission power, and the reference voltage and the output voltage of the monitor light-receiving element are input and compared, and a differential output signal is output to each of the n laser diode drivers. A comparator for controlling the n laser diodes by inputting to the feedback signal input terminal, and when the comparator controls the n laser diodes, the output of the monitor light receiving element When the voltage is lower than the reference voltage, the driving current of each of the n laser diode drivers is increased,
When the output voltage of the monitor light receiving element is higher than the reference voltage, the driving current of each of the n laser diode drivers is reduced.

In the parallel E / O converter of the present invention, the light emission power obtained when the reference voltage is a clock signal having a mark ratio of always 50% is input to the first channel for the monitor. The voltage is equivalent to the voltage monitored and output by the light receiving element.

[0009]

[Action]

(1) A reference voltage is input to the first channel, the voltage obtained from the light emission power of the first channel through the light receiving element for monitoring is compared with the reference voltage, and the differential output signal of the comparator is fed back to all channels. Since the data signal is input to the signal input terminal, the data signal is not fed back, and the bias current of the LD is not adjusted even when the mark ratio of the average value of the input data signal largely deviates from 50%. The emission and extinction states can be maintained in all channels, and the input data signal can be faithfully converted to emission power and output. Further, since the voltage obtained from the light emission power when the reference voltage is input to the first channel is compared with the reference voltage, the light emission power of the LD is not adjusted in a stable state, and temperature fluctuations, power supply voltage fluctuations, etc. When the reference voltage fluctuates due to an external factor, the emission power of all LDs can be automatically adjusted.

(2) Since a clock signal having a mark ratio of 50% is used as a reference voltage, even if a signal containing a DC component is input, it is not affected by the DC component, and the input data signal is faithfully converted into a light emission power. It can be converted and output.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

The configuration of FIG. 1 will be described. The data signal input terminal 1 inputs a data signal to the LD driver 3. The clock signal input terminal 2 inputs a clock signal to the LD driver 3. The LD driver 3 is the LD array 4
To drive. The LD array 4 has n LDs 5 and 6 arranged in parallel. The monitor light receiving element 7 is
The emission power of the LD 6 which is one channel of the LD array 4 is monitored. The reference voltage V _REF is a clock signal input terminal 2 for a clock signal whose mark ratio is always 50%.
Light-receiving element 7 for monitoring when the reference light emission power in the steady state, which is output from the LD 6 when being input to
It is a voltage equivalent to the output voltage of. The comparator 8 compares the output voltage of the monitor light receiving element 7 with the reference voltage V _REF and inputs the difference output signal to all the feedback signal input terminals 9.
The feedback signal input terminal 9 inputs to the LD driver 3
The drive currents of 5 and 6 can be adjusted individually.

If the clock signal is always input to the clock signal input terminal 2, the light emission power of the LD 6 in the steady state becomes the reference value, and the drive currents of the LD 5 and 6 are not adjusted.

LD due to temperature fluctuations or power supply voltage fluctuations
When the light emission power of 6 becomes larger than the reference value, the comparator 8 reduces the light emission power of the LDs 5 and 6 so that the LD
The drive current of the driver 3 is reduced and the operation for returning to the reference value of the emission power is performed. On the contrary, when the emission power of the LD 6 becomes smaller than the reference value, the drive current of the LD driver 3 is increased to the reference value of the emission power. Perform the return operation.

Further, even when a signal including a DC component is input to the data signal input terminal 1, the data signal input terminal 2
Since a clock signal is input to, the value to be fed back does not change, and the light emission and extinction states are maintained. Unlike the normal LD APC (Automatic Power Control) circuit, the light emitting and extinguishing states can be maintained.

FIG. 2 is a diagram showing changes in the light emission power of the LD of the clock signal dedicated channel of the present invention and changes in the drive current of the LD driver. FIG. 2A shows the variation of the light emission power of the LD 6, and FIG. 2B shows the LD driver 3
The change of the drive current of is shown.

The operation of FIG. 2 will be described. At point A, L
When the light emission power P of D6 increases from the reference value, the drive current I of the LD driver 3 decreases, and the light emission power P of point B
The drive current I continues to decrease even when is decreased. When the light emission power P returns to the reference value at the point C, the drive current I holds the value at that time. The drive current I increases when the emission power P decreases below the reference value at the point D, and the drive current I continues to increase even if the emission power P increases at the point E. When the emission power P returns to the reference value at the point F, the drive current I holds the value at that time.

FIG. 3 is a diagram showing the relationship between the input data signal and the clock signal of the present invention, the feedback signal and the emission power. As is clear from comparison with FIG. 4, the feedback signal for controlling the bias current value of the LD always has a mark ratio of 5
The average value is always output because it is obtained from the light emission power when the clock signal of 0% is input. Therefore, the input data signal is faithfully converted to the emission power and output.

[0019]

As described above, the present invention has the effects described below.

(1) A reference voltage is input to the first channel, the voltage obtained from the light emission power of the first channel through the light receiving element for monitoring is compared with the reference voltage, and the differential output signal of the comparator is calculated. By inputting to the feedback signal input terminal of the channel, the data signal is not fed back, and the mark ratio of the average value of the input data signal is 50%.
Even if it deviates significantly from the above, the state of light emission and extinction can be maintained in all channels without adjusting the bias current of the LD, and the input data signal is faithfully converted to the light emission power and output. It has the effect that In addition, by comparing the voltage obtained from the light emission power when the reference voltage is input to the first channel with the reference voltage, the LD is stable in a stable state.
When the reference voltage fluctuates due to external factors such as temperature fluctuations and power supply voltage fluctuations without adjusting the light emission power of the
This has the effect that the light emission power of can be automatically adjusted.

(2) By using a clock signal with a mark ratio of 50% as a reference voltage, even if a signal containing a DC component is input, the DC component is not affected and the input data signal is faithfully emitted. It has the effect that it can be converted into and output.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing changes in the light emission power of the LD of the channel dedicated to the clock signal of the present invention and changes in the drive current of the LD driver.

FIG. 3 is a diagram showing a relationship between an input data signal and a clock signal of the present invention, and a feedback signal and a light emission power.

FIG. 4 is a diagram showing a relationship between an input data signal of a conventional example, a feedback signal and a light emission power.

[Explanation of symbols]

1 data signal input terminal 2 clock signal input terminal 3 LD driver 4 LD array 5, 6 LD 7 light receiving element for monitoring 8 comparator 9 feedback signal input terminal V _REF reference voltage

Claims (2)

[Claims] 1. An n number of laser diode drivers, which are provided in parallel with a data signal input terminal and a feedback signal input terminal, and output signals of each of the n laser diode drivers are input signals. A current is driven by a data signal input to the data signal input terminal of each of the n laser diode drivers, and a drive current is driven by a feedback signal input to each feedback signal input terminal of each of the n laser diode drivers. Of n laser diodes having equivalent characteristics, an n-channel laser diode array in which the n laser diodes are connected in an array, and a laser diode driver of the n laser diode drivers. A first laser diode driver and an output signal of the first laser diode driver And a first laser diode for inputting a signal to the first channel, the first laser diode is operated when a predetermined reference voltage is input to the data signal input terminal of the first laser diode driver. A monitor light-receiving element that monitors the light-emission power output from the diode and outputs a voltage proportional to the light-emission power, and the reference voltage and the output voltage of the monitor light-receiving element are input and compared, and a differential output A comparator for controlling the n laser diodes by inputting a signal to each of the feedback signal input terminals of the n laser diode drivers, the comparator controlling the n laser diodes. When the output voltage of the monitor light receiving element is smaller than the reference voltage, each of the n laser diode drivers is The serial driving current is increased, to reduce each of the driving current of said n laser diode driver when the output voltage of the monitor light-receiving element is larger than the reference voltage, parallel E / O converter. 2. The mark ratio of the reference voltage is always 50%.
2. The parallel E / O according to claim 1, wherein the light emission power obtained when the clock signal is input to the first channel is a voltage equivalent to the voltage output from the monitor light receiving element by monitoring. converter.