JPH06350564A - Error detection method using multi-wavelength light source, its device and system - Google Patents

Abstract

PURPOSE:To obtain an error detection method using a multi-wavelength light source, its device and system in which problems of a deteriorated throughout and a complicated coding circuit are settled. CONSTITUTION:An optical signals are sent from a light source 1 emitting lights of plural wavelengths and a dissidence detector 6 detects dissidence among received signals of each wavelength to detect a transmission error. A transmission error is detected by detecting an error in the code rule in coding by that phases of optical signals sent from the light source emitting lights of plural wavelengths are shifted and the shifted signals are overlapped with each other. Thus, the transmission error is detected without addition of an error check code.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission error detecting method in an optical communication system, an apparatus and a system therefor.

[0002]

2. Description of the Related Art Conventionally, as a method of detecting a transmission error of a digital signal, there is a method such as a parity check. This is to detect a transmission error by adding a check bit after an information bit in a transmitting section to send a signal and checking in a receiving section whether the check bit is correctly added.

[0003]

However, in the above-mentioned conventional example, there are problems that throughput is reduced and a coding circuit is complicated because a bit for parity check is added.

Therefore, it is an object of the present invention to provide an error detection method using a multi-wavelength light source, an apparatus and a system therefor, which solve these problems.

[0005]

According to the present invention for achieving the above object, an optical signal is transmitted from a light source which emits light of a plurality of wavelengths, a mismatch between received signals of respective wavelengths is detected, and a transmission error is detected. Detecting or encoding by shifting the phase of the optical signal of each wavelength of the optical signal sent from the light source that emits light of multiple wavelengths and superimposing, and detecting the error of the above coding rule to detect the transmission error As a result, transmission errors can be detected without adding an error detection code.

More specifically, the first error detection method transmits an optical signal from at least one light source that emits light of a plurality of wavelengths, detects a mismatch between received signals of respective wavelengths, and detects a transmission error. It is characterized by detecting. An error detection device using the first method is a transmission unit that transmits an optical signal including at least one light source that emits light of a plurality of wavelengths.
And means for separating the optical signals of the light of the plurality of wavelengths,
It is characterized by having a receiving unit equipped with a unit for converting the separated optical signal into an electric signal and a unit for detecting a mismatch between the plurality of electric signals. The receiving unit further has a means for aligning the phases of the plurality of electrical signals,
It may further have means for converting the pulse width of the received signal from the means for converting the separated optical signal into an electric signal and returning it to the original signal.

Further, the error detecting device using the first method has at least one light source for emitting light of a plurality of wavelengths, means for separating the optical signals of the light of the plurality of wavelengths, and the separated light. A means for aligning the phases of the signals, a transmitter having means for multiplexing the optical signals of the light of the plurality of wavelengths, and means for separating the light from the transmitter into each wavelength, and the separated optical signals Is converted into an electric signal, and a receiver having a means for detecting a mismatch of the plurality of electric signals is provided. The receiving unit may further include means for converting the pulse width of the received signal from the means for converting the separated optical signal into an electric signal and returning it to the original signal.

The second error detecting method performs encoding by shifting the phase of the optical signal of each wavelength of the optical signal transmitted from at least one light source that emits light of a plurality of wavelengths, and superimposing the optical signal. It is characterized by detecting a rule error and detecting a transmission error. An error detection device using the second method includes at least one light source that emits light of a plurality of wavelengths, and means for separating optical signals of the light of the plurality of wavelengths.
Means for shifting the phase of the separated optical signals, and a transmitter having means for multiplexing the optical signals of the light of the plurality of wavelengths, and
Means for converting the optical signal from the transmitter into an electrical signal,
It is characterized by having a receiving unit equipped with means for detecting an error in the coding rule. The receiver may further include means for decoding the received signal from the means for converting the optical signal from the transmitter into an electric signal into the original signal.

An optical communication system according to the present invention is characterized by using the first or second error detection 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 used in this embodiment, and FIG.
FIG. 4 is a diagram showing a modulation waveform when light is emitted at one wavelength, and FIG. 4 is a diagram showing a waveform of each part in the network.

First, the light source used in the optical transmitter will be described.
This light source is a semiconductor laser described in Japanese Patent Publication No. 63-211786, Japanese Patent Publication No. 63-211787, etc., and includes a plurality of light emitting layers 31 and 32 having different energy levels as shown in FIG. The active layer has a different active layer, and by injecting a current into the active layer, signals of different wavelengths can be transmitted at the same time. In FIG. 2, 33 is a barrier layer and 34 and 35 are clad layers. As shown in FIG. 3, when the current waveform is modulated by the RZ signal (FIG. 3A), the modulation waveform is such that an optical signal of wavelength λ ₂ is transmitted in the first half of the current pulse and an optical signal of wavelength λ ₁ is transmitted in the latter half of the current pulse (FIG. 3 (b)). Further, depending on the pulse width and the amount of injected current, it is possible to emit only one of the wavelengths.

Next, the principle of detecting a transmission error using the multi-wavelength light source will be described. If a light source that emits light of two wavelengths is used as the multi-wavelength light source, optical signals of wavelengths λ ₁ and λ ₂ with respect to the injection current as shown in FIG. 3 can be obtained. This optical signal is sent to the optical transmission line, and the receiving section separates it into optical signals of wavelengths λ ₁ and λ _{2 using} an optical demultiplexer and receives them. Then, when the signals are aligned in phase and then compared, the same signal is obtained, but if an error occurs in one of the signals, the bits in which the error occurs do not match. In other words, it means that an error has been detected. If the same bit in both signals is wrong, the error cannot be detected, but it is considered that there is no correlation between the two signals (receiver, transmission waveform, phase, wavelength are different), so the probability of the same bit being mistaken is extremely low. , Error rate 1 ×
It is considered that such an error is small when detecting an error of about 10 ⁻² to 1 × 10 ⁻¹⁰ .

Next, a first embodiment of the present invention will be described.
In FIG. 1, 1 is an optical transmitter using the multi-wavelength laser, 2 is a demultiplexer for separating signals from the multi-wavelength laser into optical signals of respective wavelengths, 3 and 4 are separated optical signals. To an electric signal, 5 is a phase controller for aligning the phases of the electric signals from the optical receivers 3 and 4, 6 is a circuit for detecting a mismatch between the two signals, and 7 is a received signal Is a pulse width conversion circuit for converting the pulse width of the RZ signal of the above, and 13 is an optical fiber.

In FIG. 1, the multi-wavelength light source 1 is a digital R
When modulated by the Z signal, optical signals of wavelengths λ ₁ and λ ₂ with respect to the injection current as shown in FIG. 3 are obtained, light of wavelength λ ₂ appears in the first half of the pulse, and light of wavelength λ ₁ appears in the second half of the pulse.

Hereinafter, FIG. 4 shows how the signal is transmitted. When the RZ signal 1101 pattern is input to the light source 1 as a transmission signal (FIG. 4A), two optical signals having different wavelengths and phases are obtained (b) and (c), and these signals are transmitted to the optical fiber transmission line 13. When it is sent out, it travels through the optical transmission line while undergoing waveform deterioration due to loss of the optical fiber 13, mode dispersion, and the like. Both signals transmitted through the optical transmission line 13 are separated into respective wavelengths by the optical demultiplexer 2 in the receiving section and input to the optical receiving sections 3 and 4. The optical receivers 3 and 4 convert the input optical signal into an electric signal, identify and reproduce 1 and 0 of the digital signal, and output. When the optical receiver discriminates and reproduces a signal, a signal error occurs due to waveform deterioration due to the optical transmission line 13, shot noise when converting an optical signal into an electric signal, thermal noise of an electric circuit, and the like. However, both signals are
In the above, the waveforms are independently deteriorated due to the difference in the transmission waveform of each signal, the difference in the wavelength, the difference in the phase, and the noise level of the receiver also differs depending on the receiver, so that an error occurs independently.

The signals output from the optical receivers 3 and 4 are input to the phase controller 5 and their phases are aligned (d),
(E). When the phase of both signals is transmitted from the optical transmitter 1, the signal of the wavelength λ ₂ is advanced by about 1/4 bit as shown in FIG. 3, so the signal on the wavelength λ ₂ side is delayed by 1/4 bit. If so, the phases of both signals can be aligned. The two signals whose phases have been aligned by the phase controller 5 are detected by the non-coincidence detection circuit 6 formed by exclusive OR or the like. Since both signals are the same signal, a mismatch is not usually detected, but if an error occurs in either of the signals ((e) hatched portion), the mismatch detection circuit 6 will detect an error. (F). However, if the same bit of both signals is incorrect, the mismatch detection circuit 6 judges that they are a match and does not detect an error, but both signals have no correlation and independently generate an error, and normally error detection is performed. At error rates better than 1 × 10 ^-2 , it is considered that the probability that the same bit in both signals will be erroneous is quite low. The original RZ signal of the received signal can be obtained by doubling the pulse width by the pulse width conversion circuit 7.

[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 for combining or combining lights of two wavelengths, 9 is a demultiplexer for separating lights of two wavelengths, and 10 is for aligning the phases of two optical signals. The same parts as those in the above embodiment are designated by the same reference numerals.

The second embodiment is an example in which the phase control of signals of two wavelengths is performed in the transmitting section, and 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), two optical signals having different wavelengths and phases are obtained, and the signals are separated into respective wavelengths by the optical demultiplexer 9 (b), (c). ,
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 (b) whose phase is advanced by about 1/4 bit and outputs the both signals in the same phase (d), (e). Both signals are combined by the multiplexer 8 and sent out to the optical fiber transmission line 13, where the loss of the optical fiber 13
It travels through the optical transmission line while undergoing waveform deterioration due to mode dispersion. Both signals transmitted through the optical transmission line 13 are separated into respective wavelengths by the optical demultiplexer 2 in the receiving section and input to the optical receivers 3 and 4. The optical receivers 3 and 4 convert the input optical signal into an electrical signal and convert the digital signal 1 and 0.
Discriminate and reproduce and output. When an error occurs in either of the signals output from the optical receivers 3 and 4 ((e)
In the shaded area, a mismatch is detected by the mismatch detection circuit 6 configured by exclusive OR or the like. The original RZ signal can be obtained by doubling the pulse width of the received signal in the pulse width conversion circuit 7.

[0019]

[Third Embodiment] FIG. 6 is a diagram showing a third embodiment of the present invention. In FIG. 6, reference numeral 11 is a code detection circuit for checking the coding rule and detecting an error, and 12 is a code conversion circuit for converting the coding rule of the present embodiment into an RZ signal. There is.

In FIG. 6, the multi-wavelength light source 1 is digital R
When modulated with the Z signal 1101 pattern (FIG. 4A),
Two optical signals having different wavelengths and phases are obtained, and these signals are separated into respective wavelengths by the optical demultiplexer 9 (b),
(C) Input to the optical phase controller 10. Optical phase controller 1
0 is about 1/4 of the (c) signal whose phase is delayed.
Bits are delayed and the pulses of both signals are shifted by half a bit and output (g) and (h). Both signals are multiplexed by the multiplexer 8 and sent to the optical fiber transmission line 13. This signal has a coding rule in which "1" of the RZ signal is represented by 1010 patterns and "0" is represented by 0000.

The signal output from the multiplexer 8 to the optical fiber 13 travels in the optical transmission line while undergoing waveform deterioration due to loss of the optical fiber, mode dispersion and the like. Optical transmission line 13
The signal transmitted by (i) is input to the optical receiver 3, which converts the optical signal into an electrical signal, identifies and reproduces 1 and 0 of the digital signal, and outputs the identified signal. When an error has occurred in the signal output from the optical receiver 3 ((i) hatched portion), the code detection circuit 11 detects an error because the code rule is violated (j). The received signal is converted back to the original RZ signal by the code conversion circuit 12.

[0022]

Other Embodiments In the above embodiments, the light source that outputs two wavelengths has been described as a multi-wavelength light source, but the number of wavelengths of the present invention is not limited to two, and a light source that outputs a plurality of wavelengths can be used. Applicable. In that case, a light source that outputs a plurality of wavelengths, a means that separates and combines a plurality of wavelengths, and a means that detects the mismatch by aligning the phases of these signals are sufficient. Alternatively, the phase of the light of each wavelength is controlled by the optical phase controller, and the coding rule is "1" of RZ code 101010.
The coding rule may be detected as. Further, the network configuration is not limited to 1 (transmission side) to 1 (reception side), and can be applied to a LAN such as a star, a bus and a loop. Furthermore, two light sources that oscillate at different wavelengths may be provided, and these may be driven by the same signal to output two wavelengths. In this case, since the phases are matched from the beginning, the optical phase controller is unnecessary in the case of the first embodiment.

[0023]

As described above, an optical signal is transmitted from a light source device which emits light of a plurality of wavelengths, a mismatch between received signals of respective wavelengths is detected to detect a transmission error, and The error detection code is detected by detecting the transmission error by detecting the error in the coding rule by appropriately shifting the phase of the optical signal of each wavelength of the optical signal transmitted from the light source device that emits light Transmission errors can be detected without adding. Therefore, there is an effect that a reduction in throughput due to the addition of the error detection code is not caused and a simple circuit configuration can be achieved.

[Brief description of drawings]

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 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 two wavelengths using one signal.

FIG. 4 is a diagram showing waveforms at various parts in the network.

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.

[Explanation of Codes] 1 Optical transmitter using multi-wavelength laser 2, 9 Demultiplexer 3, 4 Optical receiver 5, 10 Phase controller 6 Mismatch detection circuit 7 Pulse width conversion circuit 8 Combiner or combiner 11 Code detector 12 Code converter 13 Optical transmission line

Claims (11)

[Claims] 1. An error detection method comprising detecting an error in transmission by transmitting an optical signal from at least one light source that emits light of a plurality of wavelengths and detecting a mismatch between received signals of the respective wavelengths. 2. A transmitter for transmitting an optical signal, which comprises at least one light source for emitting a plurality of wavelengths of light, a means for separating the optical signals of the plurality of wavelengths of light, and the separated optical signals. An error detecting device comprising: a receiving unit having a unit for converting the electric signal into an electric signal and a unit for detecting a mismatch between the plurality of electric signals. 3. The error detection device according to claim 2, wherein the reception unit further includes means for aligning the phases of the plurality of electric signals. 4. The error detection according to claim 2, wherein the receiving section further includes means for converting a pulse width of a reception signal from the means for converting the separated optical signal into an electric signal and returning the pulse signal to an original signal. apparatus. 5. At least one light source for emitting light of a plurality of wavelengths, means for separating optical signals of the light of the plurality of wavelengths, means for aligning phases of the separated optical signals, and A transmitter having means for multiplexing optical signals of light, a means for separating the light from the transmitter into wavelengths, a means for converting each separated optical signal into an electric signal, and the plurality of electric An error detecting device having a receiving unit having means for detecting a signal mismatch. 6. The error detection according to claim 6, wherein the receiving section further includes means for converting the pulse width of the received signal from the means for converting the separated optical signal into an electric signal and returning the converted signal to the original signal. apparatus. 7. Encoding is performed by shifting the phases of the optical signals of the respective wavelengths of the optical signals transmitted from at least one light source that emits light of a plurality of wavelengths and superimposing them, and detecting an error in the coding rule. An error detection method characterized by detecting transmission errors. 8. At least one light source for emitting light of a plurality of wavelengths, means for separating an optical signal of the light of the plurality of wavelengths, means for shifting the phases of the separated optical signals, and A transmitter having a means for multiplexing optical signals of light, a means for converting an optical signal from the transmitter into an electric signal, and a receiver having means for detecting an error in the coding rule. An error detection device characterized by. 9. The error detection device according to claim 8, wherein the receiving unit further includes a unit that decodes the received signal from the unit that converts the optical signal from the transmitting unit into an electric signal into an original signal. 10. An optical communication system using the error detecting method according to claim 1. 11. An optical communication system using the error detecting method according to claim 7.