JPH0730175A - Laser diode drive device - Google Patents

Abstract

PURPOSE:To improve reliability in light data communication by reducing the influence of pulsation characteristics of a laser diode on pulse modulation in light data communication by compensating the drive waveform of the laser diode. CONSTITUTION:Light pulse output is optimized by compensating drive waveform by a mark length detection circuit 10 for constituting a compensation means 3, a circuit 11 for selecting amount of compensation and a modulation width compensation circuit 12 according to data 4b and 4c for modulating a laser diode 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode driving apparatus used for supplying a pulse current for data communication to a laser diode used as an element for converting electricity into an optical signal in an optical communication system. Regarding

[0002]

2. Description of the Related Art FIG. 9 is a block diagram of a conventional laser diode driving circuit. In FIG. 9, 21 is a laser diode, 22 is a driving circuit, 23 is an optical fiber, and 24 is a receiving circuit. The operation of FIG. 9 will be described with reference to the pulse modulation waveform diagram of FIG. 10. When the data 4g is input to the drive circuit 22, the DC current 22d and the pulse current 2 are generated according to the data 4g.
The laser diode 21 is driven by the drive current 22g added with 2p. In recent years, as a laser diode, unlike a conventional relaxation oscillation type, a pulsation type laser diode capable of reducing the influence of returning light has been developed.

FIG. 10 shows a conventional laser diode drive circuit 22.
FIG. 5 is a diagram showing a waveform when a laser diode is pulse-modulated by using. Reference numeral 4g in FIG. 10 is data input to the drive circuit 22, and 22g is a current waveform for driving the laser diode. Reference numeral 25 denotes an optical output waveform when a conventional relaxation oscillation type laser diode is used as the laser diode 21. Received data, which is received by the receiving circuit 24 through the optical fiber 23, of the optical output of the relaxation oscillation type laser diode is indicated by 26.

On the other hand, 27 is a waveform of the optical output when a pulsation type laser diode is used as the laser diode 21. The optical output 27 of this pulsation type laser diode is transmitted through the optical fiber 23 to the receiving circuit 24.
28 shows the data received in. When a pulsation type laser diode is used in this way, due to the characteristics of the pulsation, it is not possible to obtain an optical output equivalent to the "high" level section of the drive current 22g.
The data 28 received at 24 may be shorter than the data 29 originally desired to be transmitted.

[0005]

When the pulsation type laser diode is used as described above, particularly when the modulation is performed at high speed, a portion which is not output with respect to the original pulse width occurs, and the data is reproduced. When doing so, there is a problem in that jitter increases in the receiving section and data reliability cannot be sufficiently secured.

An object of the present invention is to solve such conventional problems and improve reliability in optical data communication.

[0007]

In order to achieve the above object, the present invention provides a drive circuit for modulating a laser diode according to data and a correction circuit for eliminating an influence on the pulse modulation of the laser diode. A mark length detection circuit for detecting the mark length of the data, a correction amount selection circuit for selecting the correction amount of the modulation width of the data according to the mark length detected by the mark length detection circuit, and a selection by the correction amount selection circuit. A modulation width correction circuit for correcting the modulation width with the corrected correction amount, and a correction amount storage circuit for storing the correction amount of the correction amount selection circuit; and a pulsation pulse which is a pulsation characteristic of the laser diode. A pulsation width detection circuit for detecting the width and data of an arbitrary mark length are generated, and the correction amount storage circuit responds to the mark length. A control circuit for storing Seiryo, characterized by having a time management means for operating each optimal time interval the control circuit to the correction means.

[0008]

According to the present invention, the drive waveform is corrected by the mark length detection circuit, the correction amount selection circuit, and the modulation width correction circuit, which constitute the correction means, according to the data for modulating the laser diode. I do. Further, the correction amount stored in the correction amount storage circuit is set according to the pulsation characteristic of the laser diode. Further, the correction amount of the correction amount selection circuit is set by the pulsation width detection circuit. Further, the time management means resets the value of the correction amount for each optimum time interval in the correction amount storage circuit. That is, according to the present invention, the correction amount stored in the correction amount storage circuit is selected by the mark length detection circuit and the correction amount selection circuit according to the data for modulating the laser diode, and the laser beam is corrected by the modulation width correction circuit. The drive waveform for driving the diode is corrected, and the laser diode is driven by the drive circuit to optimize the optical output.

Therefore, the present invention can improve the reliability of data by correcting the pulsation characteristic of the laser diode by the correction means.

[0010]

1 is a basic principle diagram of the present invention, and FIG. 2 is a time chart of a conventional example and a basic principle diagram. In FIG. 1, 1 is a laser diode, 2 is a drive circuit for driving the laser diode 1, and 3 is correction means for eliminating the influence of the pulsation characteristic of the laser diode 1 on the pulse modulation of data. Data 5 is an optical fiber for transmitting the optical output of the laser diode 1, and 6 is a receiving circuit for receiving the modulated light.

In FIG. 2, the laser diode 21 is driven by the conventional drive circuit 22 shown in FIG. 9 and the laser diode 21 is driven by the drive circuit 2 with the correction means 3 shown in the basic principle of the present invention shown in FIG. The operation when the diode 1 is driven will be described. In the conventional example of FIG. 9, the drive waveform when the data 4a is driven by the conventional drive circuit 22 is 22a, and the optical output when the laser diode 21 is driven is 21a.
The data received by the receiving circuit 24 through this fiber 23 is shown by 24a. A jitter component 8 is generated with respect to the data 7a that is originally desired to be transmitted, and the pulse width is narrowed, thus lowering the reliability of data communication.

On the other hand, according to the basic principle of the present invention, the transmitted data 4a is input to the drive circuit 2 and the correction means 3, and the correction means 3 corrects the drive waveform to obtain the corrected drive waveform 3a. Become. Drive waveform 3a after this correction
To drive the driving circuit 2 and the optical output 1 of the laser diode 1
get a This optical output 1a is guided to the receiving circuit 6 through the fiber 5. The data received by the receiving circuit 6 is 6a, and there is only a slight jitter component 9 with respect to the data 7a originally desired to be transmitted. Therefore, as shown in the basic principle diagram of the present invention, by correcting the waveform for driving the laser diode 1 by the correction means 3, the received data in the receiving circuit approaches the data to be originally transmitted, so that the reliability in data communication is improved. Can be improved.

FIG. 3 is a block diagram showing the structure of a laser diode driving device according to the first embodiment of the present invention.
In the configuration of the correction means 3 in FIG. 3, 10 is a mark length detection circuit for detecting the mark length of data, 11 is a correction amount selection circuit for selecting a correction amount according to the mark length detected by the mark length detection circuit 10, Reference numeral 12 is a modulation width correction circuit that performs correction based on the information indicated by the correction amount selection circuit 11.

The data to be transmitted is the mark length detection circuit 10
The continuous mark length (the number of data "1") is detected by, the correction amount selection circuit 11 selects the correction amount according to the continuous mark length, and the modulation width correction circuit 12 corrects the drive waveform. The laser diode 1 is driven by the drive circuit 2.

FIG. 4 is a timing chart when transmitting data 4b having a mark length of "1", and FIG. 5 is a timing chart when transmitting data 4c having a mark length of "3". Below, the mark length is "1", "3"
Each operation of the present embodiment in the case of will be described.

First, referring to FIG. 4, the laser diode 1
The optical output 21b of the laser diode 21 when the data 4b having a mark length of "1" is driven by the conventional drive circuit 22 of FIG. 9 is output at the end of the drive pulse. It has not been. Therefore, the received data received by the receiving circuit 24 through the fiber 23 is 24b.
Therefore, it has 14b as a jitter component with respect to the data 13b that is originally desired to be transmitted.

According to this embodiment, the mark length detecting circuit 10 determines that the data 4b having a mark length of "1" is the length "1" bit time, and the mark length detecting circuit 10 outputs the data "b" indicating the length. 1 "is output (10b), and the correction amount selection circuit 11 selects and outputs the preset correction amount 11b,
The modulation waveform correction circuit 12 corrects the drive waveform and outputs (12b).

The output 12b of the modulation width correction circuit 12 outputs the optical output 1b of the laser diode 1 which has driven the laser diode 1 by the drive circuit 2 and emitted light at the end of the drive pulse. This optical output 1b is received by a receiving circuit (not shown) through an optical fiber (not shown) and becomes received data 15b. In this way, the correction waveform is corrected by the function of the correction means 3 to form the reception data 15b, and the jitter component 16b for the data 13b originally desired to be transmitted is the same as that of the conventional drive circuit.
It is smaller than the jitter component 14b due to 22.

Next, referring to FIG. 5, the light output 21c obtained when the data 4c having the mark length of "3" is driven by the conventional drive circuit 22 is the light output at the end of the drive pulse in this example. There is. The data received by the receiving circuit 24 through the optical fiber 23 is 24c, and the jitter component 14c for the originally desired data 13c is small.

According to this embodiment, the data 4c having the mark length "3" is judged by the mark length detection circuit 10 to have the length "3" bit time, and the mark length detection circuit 10 outputs the data "3" indicating the bit length. Is output (10c), the preset correction amount 11c is output by the correction amount selection circuit 11, the drive waveform is corrected by the modulation width correction circuit 12, and the drive circuit is output by the output 12c of the modulation width correction circuit 12. At 2, the laser diode 1 is driven.

Although the correction amount in this case is small, the optical output of the laser diode 1 when it is corrected becomes 1c, and this optical output 1c is passed through an optical fiber (not shown) to the receiving circuit.
The received data when received by (not shown) is 15c.
The jitter component at this time is 16c.

In this case, the jitter component when driven by the conventional drive circuit 22 is 14 with respect to the data 13c to be originally transmitted.
c, and the jitter component when driven by the drive circuit 2 of this embodiment is 16c, and both jitter components are small, but these conditions are pulsation characteristics such as the pulsation interval of the laser diode and the length of the mark length. It depends on the size. That is, it is possible to obtain the optimum light output by presetting the optimum correction amount according to the length of the mark length and the pulsation characteristic of the laser diode.

Further, generally, in optical data communication, it is necessary to regenerate a clock in the receiving section, so that the number of consecutive data "1" or "0" is limited. Therefore, the type of the mark length is finite, and the type of the correction amount selected by the correction amount selection circuit 11 is also finite, and the circuit configuration can be realized with a simple configuration.

Next, FIG. 6 is a block diagram showing the structure of a laser diode driving device according to the second embodiment of the present invention. In FIG. 6, blocks having the same numbers as those in FIG. 3 have the same functions. Reference numeral 17 denotes a correction amount storage circuit that stores a correction amount for performing correction according to the length of the mark length, and is selected by the correction amount selection circuit 11 according to the mark length detected by the mark length detection circuit 10. It has a function of storing the correction amount.

In this embodiment, when the transmission data 4d similar to the transmission data 4b and 4c described in FIGS. 4 and 5 is input, the mark length detection circuit 10 detects the mark length of the data 4d and corrects it. The amount selection circuit 11 selects a correction amount according to the mark length stored in the correction amount storage circuit 17, the modulation width correction circuit 12 corrects the modulation width, and the drive circuit 2 drives the laser diode 1.

Since the correction amount according to the mark length can be stored, for example, the pulsation characteristic of each laser diode is measured at the time of production, and the correction amount according to the mark length is stored. Thus, it becomes possible to realize the optimum correction.

FIG. 7 is a block diagram showing the structure of a laser diode driving device according to the third embodiment of the present invention.
7, blocks having the same numbers as in FIG. 6 have the same functions. Reference numeral 18 denotes a pulsation width detection circuit for detecting the pulsation width which is the pulsation characteristic of the laser diode 1, and 19 stores it in the correction amount storage circuit 17 in accordance with the pulsation width detected by the pulsation width detection circuit 18. Is a control circuit for.

In this embodiment, the control circuit 19 generates data having different mark lengths, determines the correction amount based on the detection amount (pulsation width) from the pulsation width detection circuit 18, and corrects the correction amount. It is stored in the quantity storage circuit 17. The transmitted data 4e similar to the transmitted data 4b and 4c described with reference to FIGS. 4 and 5 has a mark length detected by the mark length detection circuit 10, and the mark length stored in the correction amount storage circuit 17 depends on the mark length. The correction amount selection circuit 11 selects the correction amount, the modulation width correction circuit 12 corrects the drive waveform, and the drive circuit 2 drives the laser diode 1.

Therefore, in this embodiment, since the pulsation width which is the characteristic of the pulsation of the laser diode 1 can be detected by the pulsation width detection circuit 18 and the correction can be added, a more optimal correction can be performed. it can. In the embodiment of the present invention, the pulsation width detection circuit 18 detects the pulsation width by changing the correction amount by the control circuit 19 with respect to the data having different mark lengths generated by the control circuit 19. It is needless to say that a means for detecting the pulsation interval may be used, and it can be realized as long as it has a similar function.

FIG. 8 is a block diagram showing the structure of a laser diode driving device according to the fourth embodiment of the present invention.
8, blocks having the same numbers as in FIG. 7 have the same functions. What is different from FIG. 7 is that it has a time management means 20.

In this embodiment, the operation of the time management means 20 causes the control circuit 19 to generate data having different mark lengths at optimum time intervals, and the pulsation width detection circuit 18 detects the amount of detection (pulsation). The correction amount is determined based on (width) and stored in the correction amount storage circuit 17.

Even if the pulsation characteristic of the laser diode 1 changes due to environmental factors, life, etc., in this embodiment, the pulsation width, which is the characteristic of the pulsation, is detected and corrected at each optimum time interval. Therefore, the drive circuit can perform more optimal correction on the transmission data 4f similar to the transmission data 4b and 4c described in FIGS. The optimum time interval here may be a fixed time interval or may be different.

[0033]

As described above, in the laser diode driving device of the present invention, the influence of the pulsation characteristics of the laser diode on the pulse modulation of data can be reduced by the correction means, and the reliability in optical data communication is improved. Can be achieved.

[Brief description of drawings]

FIG. 1 is a basic principle diagram of the present invention.

FIG. 2 is a time chart of a conventional example and a basic principle diagram.

FIG. 3 is a block diagram showing a configuration of a laser diode driving device according to the first embodiment of the present invention.

FIG. 4 is a timing chart when the mark length is “1” in the first embodiment.

FIG. 5 is a timing chart when the mark length is “3” in the first embodiment.

FIG. 6 is a block diagram showing a configuration of a laser diode driving device according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a laser diode driving device according to a third embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a laser diode driving device according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram of a conventional laser diode drive circuit.

10 is a pulse modulation waveform diagram using the laser diode drive circuit of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser diode, 2 ... Driving circuit, 3 ... Correction means, 4 ... Data, 5 ... Optical fiber, 6 ... Receiving circuit, 7, 13 ... Data to be originally transmitted, 8, 9, 14
b, 14c, 16b, 16c ... Jitter component, 10 ... Mark length detection circuit, 11 ... Correction amount selection circuit, 11b, 11c ... Correction amount, 12
... modulation width correction circuit, 15 ... received data, 17 ... correction amount storage circuit, 18 ... pulsation width detection circuit, 19 ... control circuit, 20 ... time management means.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04B 10/04 10/06

Claims (4)

[Claims] 1. A drive circuit for modulating a laser diode according to data, a mark length detecting circuit for detecting a mark length of the data as a correction means for eliminating an influence on the pulse modulation of the laser diode, A correction amount selection circuit that selects a correction amount of the modulation width of the data according to the mark length detected by the mark length detection circuit, and a modulation width correction circuit that corrects the modulation width with the correction amount selected by the correction amount selection circuit. And a drive waveform is corrected by the mark length detection circuit, the correction amount selection circuit, and the modulation width correction circuit according to the data for modulating the laser diode. 2. The correction means has a correction amount storage circuit for storing the correction amount selected by the correction amount selection circuit, and the correction amount stored in the correction amount storage circuit is determined according to the pulsation characteristic of the laser diode. The laser diode drive device according to claim 1, wherein the laser diode drive device is set. 3. A pulsation width detection circuit for detecting the pulsation pulse width, which is the pulsation characteristic of the laser diode, and a mark length in the correction amount storage circuit for generating data of an arbitrary mark length in the correction means. 2. The laser diode drive device according to claim 1, further comprising a control circuit for storing an optimum correction amount according to the above, and the correction amount of the correction amount storage circuit is set by the pulsation width detection circuit. . 4. The correction means has a time management means for operating a control circuit at each optimum time interval, and the correction amount value is stored in the correction amount storage circuit by the time management means at each optimum time interval. The laser diode drive device according to claim 1, wherein the laser diode drive device is reset.