JPH0787061A - Error correction method and device using multi-wavelength light source, and optical communication system using same - Google Patents

Abstract

PURPOSE:To provide the error correction method, device using a multi- wavelenght light source and the optical communication system using it in which transmission error of a transmission signal whose transmission speed is several hundreds Mbps or over is corrected with simple circuit configuration. CONSTITUTION:Optical signals with at least three wavelengths are sent from at least one light source 1 through an optical transmission line 12 and a majority decision circuit 7 takes majority decision among reception signals of each wavelength whose phases are arranged to correct the transmission error, or optical signals with at least three wavelengths are sent from at least one light 1 source and the signals are overlapped while the phases of the optical signals of each wavelength are shifted to make coding and an error based on the code rule used for the coding is detected to correct the transmission error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission error correction method and device in an optical communication system and the like and an optical communication system using the same.

[0002]

2. Description of the Related Art Conventionally, as a method of correcting a transmission error of a digital signal, for example, a transmitter encodes a signal based on a certain arithmetic expression and sends it out, and a receiver checks whether the coding rule is correct. , A method of identifying an error bit and correcting a transmission error is used.

[0003]

However, the error correction coding circuit requires a large-scale circuit in order to improve the error correction capability, and there is a problem that it is difficult to increase the speed. Especially in the optical communication field, a transmission speed of several hundred Mbps or higher is required, but since an error correction circuit corresponding to that speed has not been realized at present, it is said that a highly reliable network is not provided. There is a problem.

Therefore, an object of the present invention is to provide a transmission error correction method and apparatus in an optical communication system and the like, which solves the above problems, and an optical communication system using the same.

[0005]

According to the present invention, an optical signal of at least three wavelengths is transmitted from at least one light source, and a plurality of these signals are majority voted to correct a transmission error, or the plurality of signals are transmitted. Coding is performed by shifting the phases of the optical signals of the wavelengths and superimposing them, and the transmission error is corrected by examining the coding rule, enabling error correction without using a large-scale coding circuit. It is a thing.

More specifically, the first error correction method is to transmit an optical signal of at least three wavelengths from at least one light source and correct the transmission error by taking a majority decision between the received signals of the respective wavelengths. Is characterized by. An error correction device using the first error correction method is a transmission unit including at least one light source that emits light of three or more wavelengths,
And a means for separating the light of the plurality of wavelengths, a means for converting the separated optical signals into electric signals, and a means for taking a majority decision between the plurality of electric signals and restoring the original signals. It is characterized by having a department. The receiving unit may further include means for aligning the phases of the plurality of electric signals.

Another error correction device using the first error correction method is at least one light source which emits light of three or more wavelengths, and means for separating the light of the plurality of wavelengths. A means for aligning the phases of the separated optical signals, a transmitter having means for multiplexing the optical signals of the plurality of wavelengths, and a means for separating the light from the transmitter into each wavelength, It is characterized by having a receiving unit equipped with means for converting an optical signal into an electric signal and means for taking a majority decision among the plurality of electric signals and returning it to the original signal, or using at least three light sources having different wavelengths from each other. A transmitting unit provided with, a transmitting unit including means for multiplexing optical signals output from the plurality of light sources, a unit for separating light of a plurality of wavelengths from the transmitting unit, and the separated optical signals Means for converting to an electrical signal and the plurality of electrical signals Or characterized by having a receiving unit having a means for returning to the original signal by taking the majority.

In the second error correction method, optical signals of at least three wavelengths are transmitted from at least one light source, the optical signals of the respective wavelengths are shifted in phase, and the signals are overlapped. It is characterized by detecting the error of the coding rule used at that time and correcting the transmission error. An error correction device using the second error correction method includes at least one light source that emits light of at least three wavelengths, a unit that separates the light beams of the plurality of wavelengths, and a phase shift of the separated optical signals. Means, a transmitter having means for multiplexing and encoding the optical signals of the plurality of wavelengths, means for converting an optical signal from the transmitter into an electrical signal, and a coding rule at the time of encoding It is characterized by having a receiving unit equipped with means for detecting an error used in and restoring the original signal.

An optical communication system according to the present invention is characterized by using the above-mentioned first or second error correction method.

[0010]

Embodiment 1 FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a schematic energy band diagram near the active layer of a semiconductor laser which emits light at three wavelengths used in the present invention, and FIG. FIG. 4 is a diagram showing modulation waveforms when the semiconductor laser is made to emit light at three wavelengths, and FIG. 4 is a diagram showing waveforms at various parts in the network.

First, the principle of transmission error correction using a multi-wavelength light source will be described. Now, the same optical signals of at least three wavelengths are sent out from a single or a plurality of light sources to the optical transmission line, and the signals of the plurality of wavelengths are compared by the receiving section. If there is no transmission error, the same signal can be obtained, but if an error occurs in any of the signals, the errored bits will not match. Therefore, if the majority vote is taken, the error is corrected. The error cannot be corrected if there are more erroneous bits than correctly transmitted bits,
Since the probability that the same bit will be erroneous is quite low in the error rate that is normally used, it is considered that the error can be accurately corrected by majority voting. The accuracy of error correction can be improved by increasing the number of wavelengths used.

Next, a first embodiment of the present invention will be described. In FIG. 1, 1 is an optical transmitter using a multi-wavelength laser, 5 is a demultiplexer for separating the signal from the multi-wavelength laser 1 into optical signals of respective wavelengths, and 2, 3, and 4 are respectively separated. An optical receiver for converting an optical signal into an electric signal, 6 is an optical receiver 2,
A phase controller for aligning the phases of the electric signals from the optical receivers 3, 4 is a circuit for taking majority of the signals from the optical receivers 2, 3, 4, and 12 is an optical transmission line such as an optical fiber.

As the light source 1, semiconductor lasers described in JP-B-63-211786, JP-B-63-211787 and the like can be used. The semiconductor lasers have different energy levels as shown in FIG. It has an active layer composed of a plurality of light emitting layers. By injecting a current into the active layer, signals of different wavelengths can be transmitted at the same time. As for the modulation waveform, as shown in FIG. 3, when the RZ signal is current-driven, optical pulses of wavelengths λ ₁ , λ ₂ , and λ _{3 having} different phases are sequentially transmitted. In addition, depending on the pulse width and the amount of injected current, it is possible to emit light pulses of an arbitrary number of wavelengths.

In FIG. 1, the multi-wavelength light source 1 is a digital R
When modulated with the Z signal 1101 pattern, (Fig.
(A)), optical signals of three wavelengths with different phases are obtained ((b) in the same figure), and when this signal is sent to the optical fiber transmission line 12, the waveform is deteriorated due to optical fiber loss, mode dispersion, and the like. While traveling through the optical transmission line 12. The respective signals transmitted through the optical transmission line 12 are separated into respective wavelengths by the optical demultiplexer 5 in the receiver and input to the optical receivers 2 to 4 ((c), (d), () in the figure). e)). Optical receiver 2
Reference numeral 4 converts the inputted optical signal into an electric signal, discriminates and reproduces 1 and 0 of the digital signal, and outputs them.

In the optical receivers 2 to 4, at the time of signal identification and reproduction, waveform deterioration due to the optical transmission line 12, shot noise when converting an optical signal into an electric signal, thermal noise of an electric circuit, etc. Signal error occurs. However, in the optical transmission line 12, each signal independently deteriorates in waveform due to a difference in the transmission waveform of each signal, a difference in wavelength, a difference in phase, etc., and the noise levels of the receivers 2 to 4 are also different. Therefore, an error occurs independently.

The signals output from the optical receivers 2 to 4 are input to the phase controller 6 and their phases are aligned (FIG. 4 (f),
(G), (h)). Phase of each signal, when sent from the optical transmitter 1, since the offset approximately one-sixth bit at as shown in FIG. 4 (b), the wavelength lambda ₁ of the signal 2
If the signals of / 6 bit and λ ₂ are delayed by 1/6 bit, the phases of the respective signals can be aligned. Normally, the same signal is obtained at the output of the phase controller 6, but if a transmission error occurs in a signal of any wavelength ((f), (g), (h) in the same figure), Since different results are output, the majority decision circuit 7 makes a majority decision for each bit,
If the number of 1's is greater than the number of 0's, 1 is output as the correct result if the number of 1's is less than the number of 0's ((j) in the same figure). In this way, a transmission error can be corrected by taking a majority vote between the received signals of the respective wavelengths.

[0017]

Second Embodiment FIG. 5 is a diagram showing a second embodiment of the present invention. In FIG. 5, 8 is a multiplexer or combiner that combines or combines lights of three wavelengths, 9 is a demultiplexer that separates lights of three wavelengths, and 10 is an arbitrary phase of three optical signals. This is an optical phase controller for shifting to the position, and the same parts as those in the above embodiment are shown by the same numbers.

The second embodiment is an example in which the phase control of the signals of three wavelengths is performed in the transmitting section, and the other operations are the same as in the first embodiment. In FIG. 5, the multi-wavelength light source 1 is a digital RZ.
When modulated with the signal 1101 pattern (FIG. 4A), optical signals of three wavelengths with different phases are obtained (FIG. 4B), and this signal is separated into respective wavelengths by the optical demultiplexer 9. ((C), (d), (e) in the same figure) is input to the optical phase controller 10. The optical phase controller 10 is composed of an optical fiber or the like, and delays the signal of FIG. 4 (c) whose phase is advanced by about 2/6 bit and the signal of FIG. 4 (d) by about 1/6 bit and delays each signal. Are output with their phases aligned ((f), (g), (h) in the same figure).

The respective signals are multiplexed by the multiplexer 8 and sent out to the optical fiber transmission line 12, where the loss of the optical fiber 12
It travels through the optical transmission line while undergoing waveform deterioration due to mode dispersion. The three signals transmitted through the optical transmission line 12 are
In the receiving section, the wavelengths are separated by the optical demultiplexer 5 and input to the optical receivers 2, 3 and 4. Optical receivers 2, 3,
Reference numeral 4 converts the inputted optical signal into an electric signal, discriminates and reproduces 1 and 0 of the digital signal, and outputs them. Optical receiver 2,
If an error has occurred in any of the signals output from 3 and 4 (hatched portions in FIGS. 4 (f), 4 (g) and 4 (h)), the number of 1's in the majority decision circuit 7 is 0. If the number is larger than 1, the number of 1s is smaller than the number of 0s, it is determined to be 0, and the transmission error is corrected.

[0020]

[Third Embodiment] FIG. 6 is a diagram showing a third embodiment of the present invention, FIG. 7 is a diagram showing a code rule of the present embodiment, and FIG. 8 is a diagram showing waveforms of respective portions on a network. In FIG. 6, reference numeral 11 is a code conversion circuit for converting the coding rule of this embodiment into an RZ signal, and the same parts as those in the above embodiment are designated by the same reference numerals.

In FIG. 6, the multi-wavelength light source 1 is modulated with a digital RZ signal 1101 pattern (see FIG. 8).
(A)), three optical signals having different wavelengths and phases are obtained (b) in the figure), and the signals are separated into respective wavelengths by the optical demultiplexer 9 ((c) and (d) in the figure). , (E)), and input to the optical phase controller 10. The optical phase controller 10 outputs the signal of FIG.
The signal of (e) is delayed by about 2/6 bit ((g) and (h) of the same figure), and the pulse of each signal is shifted by 2/6 bit and output.

The respective signals are multiplexed by the multiplexer 8 ((i) in the figure) and sent to the optical fiber transmission line 12. This signal has a coding rule in which "1" of the RZ signal is represented by a triple speed RZ111 pattern and "0" is represented by a triple speed RZ000 pattern. The signal output from the multiplexer 8 to the optical fiber 12 is the loss of the optical fiber 12,
It travels through the optical transmission line while undergoing waveform deterioration due to mode dispersion. A signal transmitted through the optical transmission line 12 (see FIG. 8).
(I)) is input to the optical receiver 2, and the optical receiver 2 converts the optical signal into an electric signal, identifies and reproduces 1 and 0 of the digital signal, and outputs it.

When an error has occurred in the signal output from the optical receiver 2 (hatched portion in FIG. 8 (i)), the code conversion circuit 11 violates the above-mentioned coding rule, and therefore the original RZ signal is generated in the code conversion circuit 11. ((J) in the figure). The code conversion circuit 11 is composited based on a conversion rule as shown in FIG. 7, or the number of pulses in 3 bits is counted and the number of pulses is 2
In the above case, "1" may be set, and in the case of less than or equal to "0".

The code rule described in this embodiment is not limited to the above, and a code obtained by shifting the phases of signals of a plurality of wavelengths and superimposing them may be used.

[0025]

Fourth Embodiment FIG. 9 is a diagram showing a fourth embodiment of the present invention. In FIG. 9, 13 to 15 are optical transmitters having different emission wavelengths, and the same parts as those in the above-mentioned embodiment are designated by the same reference numerals. In FIG. 9, when the optical transmitters 13 to 15 are modulated with the same digital signal, three optical signals having different wavelengths are obtained, and these signals are multiplexed by the multiplexer 8 and sent to the optical fiber transmission line 12. . The signal output to the optical fiber 12 travels in the optical transmission line while undergoing waveform deterioration due to loss of the optical fiber, mode dispersion, and the like.

The signals transmitted through the optical transmission line 12 are demultiplexed into respective wavelengths by the optical demultiplexer 5 and input to the optical receivers 2-4, which convert the optical signals into electrical signals. After conversion, 1 and 0 of the digital signal are discriminated and reproduced and output. The same signals are usually obtained at the outputs of the optical receivers 2-4,
If a transmission error has occurred, the bit in which the error occurred will not match. Therefore, the majority decision circuit 7 takes those majority votes to correct the transmission error. In the case of this embodiment,
Since the phases are matched from the beginning, the phase controller is unnecessary.

[0027]

Other Embodiments Although the number of wavelengths of the light source is 3 in the above embodiment, the number of wavelengths of the present invention is not limited to 3 and can be applied to 3 or more wavelengths. However, when the number of wavelengths is an even number, the condition when the number of 1 and 0 is the same (for example, 1 and 0)
If the numbers are the same, set 1).

The network configuration is 1 (sending side) to 1
Not limited to (reception side), stars, buses,
It can also be applied to loops, etc.

[0029]

As described above, the optical signals of at least three wavelengths are transmitted from at least one light source, the mismatch between the received signals of each wavelength is detected to correct the transmission error, and the transmission error of plural wavelengths is corrected. A simple circuit configuration by performing encoding by shifting the phase of the optical signal of each wavelength of the optical signal sent from the light source that emits light and superimposing it, detecting the error of the coding rule and correcting the transmission error Is effective in correcting a transmission error of a transmission signal of several hundred Mbps or more.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is an energy band diagram near the active layer of the semiconductor laser used in the present invention.

FIG. 3 is a diagram showing a modulation waveform when the semiconductor laser used in the present invention is oscillated at three wavelengths by using one signal.

FIG. 4 is a diagram showing a waveform of each part in the network of the first embodiment.

FIG. 5 is a diagram showing a second embodiment of the present invention.

FIG. 6 is a diagram showing a third embodiment of the present invention.

FIG. 7 is a diagram showing a coding rule in the third embodiment.

FIG. 8 is a diagram showing a waveform of each part on the network in the third embodiment.

FIG. 9 is a diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Optical Transmitter Using Multiwavelength Laser 2-4 Optical Receiver 5, 9 Demultiplexer 6 Phase Controller 7 Majority Decision Circuit 8 Multiplexer or Combiner 10 Optical Phase Controller 11 Code Converter 12 Optical Transmission Line 13 ~ 15 Optical transmitter

Claims (9)

[Claims] 1. At least 3 from at least one light source
An error correction method characterized in that an optical signal of one wavelength is transmitted and a transmission error is corrected by taking a majority vote between received signals of each wavelength. 2. A transmitter having at least one light source for emitting light of three or more wavelengths, means for separating the light of the plurality of wavelengths, and the separated optical signal into an electrical signal. An error correction device comprising a receiving unit having a converting unit and a unit for taking a majority decision between the plurality of electric signals and returning the original signals. 3. The error correction device according to claim 2, wherein the receiving unit further includes means for aligning the phases of the plurality of electric signals. 4. At least one light source that emits light of three or more wavelengths, means for separating the light of the plurality of wavelengths, means for aligning the phases of the separated optical signals, and the plurality of wavelengths. And a means for separating the light from the transmitter into respective wavelengths, a means for converting each separated optical signal into an electric signal, and the plurality of electric signals An error correction device having a receiving unit equipped with means for recovering the original signal by taking a majority decision between them. 5. A transmitter having at least three light sources having different wavelengths, a transmitter having means for multiplexing optical signals output from the plurality of light sources, and a plurality of wavelengths from the transmitter. A receiver having a means for separating light, a means for converting the separated optical signal into an electric signal, and a means for taking a majority decision between the plurality of electric signals and restoring the original signal. Error correction device. 6. At least 3 from at least one light source
Coding is performed by transmitting optical signals of one wavelength, shifting the phases of the optical signals of each wavelength, and superimposing them, and detecting the error of the coding rule used at the time of the coding to correct the transmission error. An error correction method characterized by. 7. At least one light source that emits light of at least three wavelengths, means for separating the light of the plurality of wavelengths, means for shifting the phases of the separated optical signals, and optical signals of the plurality of wavelengths. And a means for converting an optical signal from the transmitter into an electric signal, and an error of the coding rule used at the time of encoding to detect the original signal. An error correction device having a receiving unit having means for returning to a signal. 8. An optical communication system using the error correction method according to claim 1. 9. An optical communication system using the error correction method according to claim 5.