JP2002152288A - Optical transmitter, optical receiver, optical transmission system and optical transmitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of the conventional high-speed digital signal optical transmission, employing an optical fiber has had difficulty of stable operation at a low cost, in optical communication, optical CATV and mobile communication or the like. SOLUTION: The optical transmitter is provided with a digital/analog converter 1, that receives M kinds of binary and/or multivalued signals and converts the signals into N (<M) kinds of signals, including at least a multi-value signal on the basis of a predetermined rule and with a semiconductor laser 3 that converts N kinds of signals into optical signals respectively. For the digital/ analog converter 1, combinations of the N kinds of signals are decided, in correspondence with any of combination patterns of M kinds of the signals on the basis of the above rule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmitter, an optical receiver, an optical transmission system, and an optical transmission device used for, for example, optical communication, CATV, optical measurement, mobile communication, and the like.

[0002]

2. Description of the Related Art In recent years, in a video surveillance system, CATV, subscriber system, mobile communication, etc., optical transmission by converting multi-channel video, audio or data into digital signals utilizing the low loss and wide band characteristics of optical fibers. Has been put to practical use. In these, since all media are digitized, the data transmission speed tends to increase.

[0003] First, FIG. 9 and FIG.
The configuration and operation of the conventional optical transmission system will be described with reference to FIG. FIG. 9 is a configuration diagram of a conventional optical transmission system. FIG. 10A is an explanatory diagram of the time variation of the digital signal at D1, and FIG.
FIG. 10C is an explanatory diagram of the time variation of the digital signal in D2. FIG. 10C shows the output of the time division multiplexer 100 (B in FIG. 9).
It is explanatory drawing of the time variation of a time division multiplex signal in 1).

On the optical transmitter 800 side, the two digital signals D1 and D2 are input to a time division multiplexer 100. These are time-division multiplexed and output as one signal from B1 (see FIG. 10 (c)).
The signal is amplified at 00 and input to the electro-optical converter 300.
The electric signal amplified by the amplifier 200 is converted into an optical signal by the electric-optical converter 300 and transmitted to the optical receiver 801 by the optical fiber 400.

[0005] The transmitted optical signal is input to an optical receiver 801 and is converted into an electric signal by an optical / electrical converter 500.
The signal is amplified by the amplifier 600 in front. Then, the amplified electric signal is input to the time divider 700, divided into two digital signals D1 and D2, and output.

[0006]

However, in the above-mentioned conventional system, the signal at B1 is a time-division multiplex of the signals at D1 and D2, so that the data rate is twice as long (time interval 0.5Ts). As a result, the signal is converted into an optical signal by the electric / optical converter. Further, the optical receiver also receives this high-speed optical signal.

Therefore, the response required of the electric-optical converter and the optical-electric converter must be high-speed, and if the number of digital signal systems to be transmitted increases, an optical transmission device (for example, a semiconductor A laser or a photodiode as a photodetector) is required. This is because high-accuracy temperature control and high-frequency circuit design are required to achieve stable transmission performance.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described conventional problems, and provides a simple and low-cost optical transmission system capable of relaxing required performance of an optical transmission device when optically transmitting a high-speed digital signal. An object is to provide an optical transmitter, an optical receiver, an optical transmission device, and an optical transmission system that can be constructed.

[0009]

Means for Solving the Problems The first invention (claim 1)
N) (M <= M) including at least a multi-level signal based on a predetermined rule based on input of M types of signals whose possible values are binary and / or multi-level.
Means for converting the number of signals on the transmission side for conversion into signals of different types;
Each of the N types of signals includes a transmission-side optical signal conversion unit for converting each of the N types of signals into an optical signal. Upon the conversion by the transmission-side signal number conversion unit, a combination of the values of the N types of signals is An optical transmitter characterized in that the optical transmitter is determined in accordance with any pattern of combinations of the values of the M types of signals based on the rule.

The second invention (corresponding to claim 2) uses M types of signals whose possible values are binary and / or multivalued, and is generated by conversion based on a predetermined rule. N including at least multi-level signals (<
M) receiving-side optical signal conversion means for performing conversion for restoring N types of optical signals generated by performing optical conversion on the types of signals into optical signals into the N types of signals; Receiving side signal number converting means for performing conversion for restoring the M types of signals from the restored N types of signals based on a predetermined relationship corresponding to the rule, At the time of the conversion by the number conversion means, the combination of the values of the M types of signals is determined based on the relationship in accordance with any pattern of the combinations of the values of the N types of signals. It is an optical receiver.

According to a third aspect of the present invention (corresponding to claim 3), the dividing means for generating the M kinds of binary and / or multilevel signals by dividing an externally input signal is provided. An optical transmitter according to a first aspect of the present invention, comprising:

According to a fourth aspect of the present invention (corresponding to claim 4), the M types of binary and / or multi-level signals are generated by dividing an externally input signal.
The present invention according to a second aspect of the present invention, characterized by comprising a synthesizing means for synthesizing the restored M kinds of binary and / or multi-level signals to restore the signal inputted from the outside. An optical receiver.

According to a fifth aspect of the present invention (corresponding to claim 5), the conversion of the N types of signals into the optical signals is performed using lights having different wavelengths, and the lights having different wavelengths are used. Multiplexing means for multiplexing the N types of optical signals converted and converted into N ′ (<N) types of optical signals, and transmitting the multiplexed N ′ ( An optical transmitter according to a first aspect of the present invention, which is performed using <N) types of optical signals.

According to a sixth aspect of the present invention (corresponding to claim 6), the N types of optical signals are generated by conversion using light having different wavelengths, multiplexed with N 'types of optical signals, and transmitted. A separating means for restoring the N types of optical signals by separating the N 'types of optical signals transmitted after being multiplexed. An optical receiver.

A seventh aspect of the present invention (corresponding to claim 7) is a pilot which generates a pilot signal to be transmitted to a receiving side based on a predetermined rule and used for correcting a level fluctuation of the optical signal. An optical transmitter according to a first aspect of the present invention, comprising a signal generation unit.

An eighth aspect of the present invention (corresponding to claim 8) is that, by using a pilot signal transmitted from a transmitting side and used for correcting a level variation of the optical signal, the optical signal is used. The optical receiver according to the second aspect of the present invention is provided with a level fluctuation correcting means for correcting the level fluctuation.

A ninth aspect of the present invention (corresponding to claim 9) is characterized in that a premodulation means for compensating waveform degradation of the optical signal with respect to the N types of signals is provided. Of the present invention.

A tenth aspect of the present invention (corresponding to claim 10) is provided with an equalizing means for compensating the waveform deterioration for the restored N kinds of signals. 3 is an optical receiver according to the present invention.

The eleventh invention (corresponding to claim 11) provides:
The pilot signal is generated by using a bit in a predetermined time slot of the M types of binary and / or multilevel signals as a reference value, and is transmitted to a receiving side based on the predetermined rule. The optical transmitter according to a seventh aspect of the present invention, wherein the signal is transmitted to a receiving side as a part of the optical signal by using the conversion of the N kinds of signals into the optical signal. is there.

The twelfth invention (corresponding to claim 12) provides:
The pilot signal is generated by using a bit in a predetermined time slot of the M kinds of binary and / or multi-level signals as a reference value, and using the pilot signal means that the pilot signal in the predetermined time slot is used. An eighth aspect of the present invention is the optical receiver according to the present invention, wherein the reference value is taken out.

A thirteenth aspect of the present invention (corresponding to claim 13) is:
The pilot signal is converted into an optical signal, and transmitted to the receiving side based on the predetermined rule means that the pilot signal is transmitted to the receiving side using a dedicated optical transmission path. A seventh aspect of the present invention is an optical transmitter according to the present invention.

The fourteenth invention (corresponding to claim 14) is:
The pilot signal is converted to an optical signal and transmitted to the receiving side using a dedicated optical transmission line.Using the pilot signal means that the receiving side uses the dedicated optical transmission line. An eighth aspect of the optical receiver according to the present invention, characterized in that the pilot signal is restored from the transmitted optical signal and used.

The fifteenth invention (corresponding to claim 15) is:
The pilot signal is converted into an optical signal, and is transmitted to a receiving side based on the predetermined rule.
A seventh optical transmitter according to the present invention, characterized in that the optical transmitter is combined with all or a part of the optical signals and then transmitted to the receiving side.

According to a sixteenth aspect of the present invention (corresponding to claim 16),
The pilot signal is converted into an optical signal, transmitted to the receiving side after being combined with all or a part of the N types of optical signals, and using the pilot signal means that the N types of optical signals The eighth aspect of the present invention, wherein the optical signal transmitted to the receiving side after being combined with all or a part of the optical signal is separated, and the pilot signal is restored and used. An optical receiver.

The seventeenth invention (corresponding to claim 17) is:
The M types of binary and / or multilevel signals are RZ
(Return to zero) signal according to the first aspect of the present invention.

The eighteenth invention (corresponding to claim 18) is:
For inputting M kinds of signals whose possible values of a signal are binary and / or multi-level, and converting them into N (<M) kinds of signals including at least a multi-level signal based on a predetermined rule And a transmitting-side optical signal converting means for converting each of the N types of signals into an optical signal. When the converting is performed by the transmitting-side signal number converting means, The combination of the values of each type of signal is determined based on the rule by the optical transmitter determined in accordance with any pattern of the combination of the values of the M types of signals, and the transmission-side optical signal conversion unit. A receiving-side optical signal converting unit that performs conversion for restoring the N types of optical signals generated by the conversion to the N types of signals; and the rules corresponding to the rules from the respectively restored N types of signals. Do A receiving-side signal number converting unit that performs conversion for restoring the M types of signals based on a fixed relationship. The combination of the values connects the optical receiver, the optical transmitter, and the optical receiver, which are determined based on the relationship in accordance with any pattern of the combinations of the values of the N types of signals. And an optical transmission path for transmitting an optical signal.

The nineteenth invention (corresponding to claim 19) is:
The M kinds of binary and / or multi-level signals refer to the M kinds of binary and / or multi-level signals S ₁ ,. . . ,
S _M and the N types of signals including the at least multi-level signals include the N types of signals T ₁ ,. . . , T _N , wherein the combination of the values of the N types of signals is determined according to any pattern of the combination of the values of the M types of signals based on the rule. , (I.ltoreq.i.ltoreq.M), the signal _S.sub.i is L (N.ltoreq.L <M) having M types of signals as elements
Groups G ₁ ,. . . , _GL , (2)
For an arbitrary j (1 ≦ j ≦ N), the signal T _j is composed of L groups H ₁ ,. . . , H _L
Belongs to any one of (3) for any k (1 ≦ k ≦ L) , the type of signals belonging to the group H _k less than the kind of signals belonging to the group G _k, each belonging to the group H _k the combination of the signal values is the eighteenth optical transmission system of the present invention characterized by being determined to correspond to any of pattern combinations of values of the signals belonging to the group G _k.

The twentieth invention (corresponding to claim 20) is:
By type of signal belonging to the group H _k is less than the kind of signals belonging to the group G _k, a L = N, the signal belonging to the group H _k is only one type of signal T _k That is, if the value combination of the signals belonging to the group H _k is determined corresponding to any pattern of the combination of the signal values belonging to the group G _k , the value of the signal T _{k at} a predetermined timing is a nineteenth optical transmission system of the present invention which is characterized in that is determined in one-to-one correspondence with any of the patterns of the combinations of the values of the signals belonging to the group G _k at that time.

The twenty-first invention (corresponding to claim 21)
Is an optical transmission device comprising the optical transmitter according to the first aspect of the present invention and the optical receiver according to the second aspect of the present invention.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) First, the configuration of an optical transmission system according to Embodiment 1 will be described with reference to FIGS. 1 and 2A to 2C. In addition, FIG.
It is a block diagram of the optical transmission system of this Embodiment. Also,
FIG. 2A is a diagram illustrating the time variation of the digital signal in D1, FIG. 2B is a diagram illustrating the time variation of the digital signal in D2, and FIG. FIG. 3 is an explanatory diagram of a time variation of a time division multiplexed signal at an output (A1 in FIG. 1).

As shown in FIG. 1, the optical transmission system comprises an optical transmitter 90 and an optical receiver 91.

The optical transmitter 90 comprises a digital-to-analog converter 1, a signal amplifier 2, and a semiconductor laser 3 for performing electrical-optical conversion. Note that the optical signal from the optical transmitter 90 is
The light is transmitted through the optical fiber 4 and input to the optical receiver 91. The optical receiver 9 includes an optical / electrical converter 5, an amplifier 6, and an analog / electrical converter.
It is constituted by a digital converter 7.

The digital-to-analog converter 1 corresponds to the transmitting side signal number converting means of the present invention, and the semiconductor laser 3 corresponds to the transmitting side optical signal converting means of the present invention. In addition, light
The electric conversion unit 5 corresponds to the receiving side optical signal converting unit of the present invention, and the analog / digital converter 7 corresponds to the receiving side signal number converting unit of the present invention.

Next, the operation of the optical transmission system according to this embodiment will be described.

In the optical transmitter 90, a digital signal shown in FIG. 2A is input to an input D1, and a digital signal shown in FIG. 2B is input to an input D2. The input signal is an upper bit (D1 in the present embodiment) and a lower bit (D1 in the present embodiment) of the digital / analog converter 1, respectively.
It corresponds to 2).

The digital / analog converter 1 converts a parallel digital signal input during each time slot Ts into a multilevel signal. That is, the digital-analog converter 1
From the output (A1) of the first and second signals, the upper bit of the signal output in parallel corresponds to D1, and the lower bit corresponds to D2.
An output signal as shown in FIG. 2C is obtained as a multi-level signal having four levels according to the inputs D1 and D2.

After this signal is amplified by the amplifier 2, it is converted into an optical signal by the semiconductor laser 3 and transmitted by the optical fiber 4.

On the optical receiver 91 side, the transmitted optical signal is converted into an electric signal by the (1) optical / electrical converter 5,
(2) The analog-to-digital converter 7 at the subsequent stage by the amplifier 6
The signal is amplified to a predetermined level required for the analog-to-digital conversion in the step (1), and (3) converted into a digital signal by the analog-to-digital converter 7.

At this time, the upper bit of the signal output in parallel corresponds to D1 and the lower bit corresponds to D2,
D1 is the signal of FIG. 2A, and D2 is the signal of FIG. 2B. Each will be output.

With the above-described configuration, if digital-to-analog conversion is used as a method for multiplexing signals, the fluctuation time of the signal to be transmitted optically is made the same as the time slot of the digital signal input to the digital-to-analog converter. And the equivalent transmission speed for transmission can be doubled.

Thus, the responsiveness of the optical transmission device can be
It can be independent of the number of signals to be multiplexed. Therefore, as an optical device having a high cost ratio when viewed as an apparatus, a low-cost semiconductor laser (for example, a coaxial type or a surface mount type module) that does not require broadband response.
And a light-to-electric conversion element such as a photodiode.

In the present embodiment, the input to the optical transmitter is two systems, but the present invention is not limited to this, and the number of input signals may be large. In that case, the number of levels of the multilevel signal of the output signal from the digital-analog converter increases, but the response of the optical device may be the same.

Also, in the present embodiment, the input signals to the optical transmitter have the same transmission speed. However, the present invention is not limited to this.
It is only necessary to ensure the responsiveness of a high-speed signal among the input signals.

For example, when there are three input signals and these inputs are performed in time slots Ts, 2Ts, and 3Ts, it is only necessary to ensure responsiveness to the speed corresponding to time slot Ts.

In short, the time slot of the fastest input signal may be set as a time unit for determining the level of the output signal from the digital-to-analog converter. Of course, the output signal corresponding to the slower input signal other than the fastest input signal has the same level in each time slot of the fastest input signal as included in that time slot. . In addition, digital
There should be no large deviation in the time timing when the level of each input signal input to the analog converter is determined. This is because if there is a large difference in the timing, when the output becomes unstable such as when the level of the output signal is determined (for example, when the level changes from 0 to 1), the level of the output signal becomes incorrect. This may result in the occurrence of

(Embodiment 2) Next, the configuration of an optical transmission system according to Embodiment 2 will be described with reference to FIG. FIG. 3 is a configuration diagram of the optical transmission system of the present embodiment.

As shown in the figure, the optical transmission system includes an optical transmitter 92 and an optical receiver 93.

The optical transmitter 92 has a signal splitter (hereinafter referred to as DE).
MUX) 8 and a digital / analog converter 11,
12, signal amplifiers 21 and 22, and semiconductor lasers 31 and 32 for performing electric / optical conversion. The optical transmitter 93
Are transmitted through the optical fibers 41 and 42, respectively, and input to the optical receiver 93. The optical receiver 93 is
Optical-to-electrical converters 51 and 52, amplifiers 61 and 62, analog-to-digital converters 71 and 72, and a signal multiplexing / combining device (hereinafter, referred to as MUX) 9 for multiplexing signals on a time axis.
Composed of

The signal divider 8 corresponds to the dividing means of the present invention, the means including the digital / analog converters 11 and 12 corresponds to the transmitting side signal number converting means of the present invention, and the semiconductor lasers 31 and 32 are used. The means included corresponds to the transmission side optical signal conversion means of the present invention. The signal multiplexing / synthesizing unit 9 corresponds to the synthesizing unit of the present invention, and the unit including the optical / electrical conversion units 51 and 52 corresponds to the receiving side optical signal converting unit of the present invention.
The means including the digital converters 71 and 72 corresponds to the receiving side signal number converting means of the present invention.

Next, the operation of the optical transmission system according to the present embodiment will be described.

High-speed digital signals (for example, 10 Gbp
s) is input from the input signal line 25 to the optical transmitter 92,
The DEMUX 8 divides the signal into four in time series (each signal corresponds to 2.5 Gbps) and outputs the signals to D1 to D4.

The digital signals D1 and D2 are digital
The analog signal is converted into an output signal having a multilevel by the analog converter 11, is converted into an optical signal by the semiconductor laser 31 via the amplifier 21, and is transmitted through the optical fiber 41. Similarly, D3, D4
Is an output signal having a multi-value level in the digital-to-analog converter 12,
An optical signal is formed by the semiconductor laser 32 and transmitted through the optical fiber 42.

On the optical receiver 93 side, the optical fiber 4
The optical signal from 1 is converted into an electric signal by an optical / electrical converter 51, and is amplified by an amplifier 61 to a predetermined level required for analog / digital conversion by an analog / digital converter 71 at a subsequent stage. The digital signal is converted by the digital converter 71 into a digital signal. Similarly, the optical signal from the optical fiber 42 is converted into an electric signal by an optical / electrical converter 52, and the analog / digital converter 7
The signal is amplified to a predetermined level required for the analog-to-digital conversion in step 2 and converted into a digital signal by the analog-to-digital converter 72.

The four parallel digital signals thus obtained are time-division multiplexed by the MUX 9 and output from the signal line 26. In order to match the timing of each signal, for example, a two-core tape core may be used as the optical fibers 41 and 42.

With the above configuration, a high-speed digital signal is time-division-divided into several low-speed signals, which are converted into multi-level signals using several digital-to-analog converters. By transmitting an optical fiber using a low-cost optical transmission device whose performance is not strict, a system capable of equivalently high-speed transmission can be provided at a low cost.

In this embodiment, DEMUX is 4
A specific example is shown in which the division and the digital / analog conversion are provided only in two systems. However, the number of divisions and the number of digital-to-analog conversion systems are not limited to this.
There is no particular limitation as long as the multi-level signal identification is within a range that can be performed by the analog-to-digital converter in the optical receiver.

(Embodiment 3) Next, the configuration and operation of an optical transmission system according to Embodiment 3 will be described with reference to FIG. FIG. 4 is a configuration diagram of the optical transmission system of the present embodiment.

The optical transmission system of the present embodiment is different from the above-described optical transmission system of the second embodiment (see FIG. 3) mainly in the following two points. That is,
(1) In the optical transmitter 94, when the multilevel signal from the amplifier 21 is converted into an optical signal by the semiconductor laser 33 and the multilevel signal from the amplifier 22 is converted into an optical signal by the semiconductor laser 34, The optical signal oscillates at a wavelength different from that of the semiconductor laser 34, and the optical signal converted by them is wavelength-multiplexed by the optical multiplexer 35 and transmitted by one optical fiber 34. (2) The optical receiver 95 The wavelength division multiplexed optical signal is wavelength-separated by the optical demultiplexer 36, the light of each wavelength is converted into an electric signal by the optical / electrical converters 53 and 54, and the analog / digital conversion is performed by the amplifiers 63 and 64. The analog-to-digital converters 71 and 72 convert the signals to digital signals.

The optical multiplexer 35 corresponds to the multiplexing means of the present invention. Further, the optical demultiplexer 36 corresponds to the separating means of the present invention.

With such a configuration, an optical transmission system can be constructed with a single optical transmission line, and even if a plurality of systems of signals are added, semiconductor lasers and optical multiplexers having different wavelengths are added or replaced. This facilitates system expandability.

In the present embodiment, the multiplexing of the present invention is performed by combining two optical signals into one optical signal. However, the multiplexing of the present invention is not limited to this. In short, the multiplexing is performed by combining N optical signals converted using lights having different wavelengths into N ′ (<N) optical signals. I just need.

(Embodiment 4) Next, FIGS.
The configuration and operation of the optical transmission system according to the fourth embodiment will be described with reference to FIG. FIG. 5 (a)
FIG. 5B is a diagram illustrating the time variation of the digital signal in D1, FIG. 5B is a diagram illustrating the time variation of the digital signal in D2, and FIG. 5C is time division multiplexing in the output of the digital-to-analog converter 1. FIG. 4 is an explanatory diagram of a time variation of a signal.

The configuration of the optical transmission system of this embodiment is as follows.
The configuration is the same as the configuration of the optical transmission system according to the first embodiment described above. However, in this embodiment, digital
As shown in FIGS. 5A and 5B, the signals at D1 and D2 input to the analog converter 1 (see FIG. 1) are always set to 0 level even if they are at 1 level within the unit time slot Ts. A return RZ (Return Zero) signal is used. As a result, the multilevel signal from the digital-to-analog converter 1 is also output as a signal that returns to the 0 level within the unit time slot, as shown in FIG.

By adopting such a signal system, the signal level always returns to 0 level within the unit time slot. Therefore, the transmission band does not need to have a low frequency range, and it is sufficient if the band allows the pulse response of the RZ signal in a unit time slot. A system that does not require a wide band characteristic as a transmission system is constructed. it can.

In this embodiment, an example is shown in which an RZ signal is used as an input signal. However, in a normal high-speed digital signal generator, the signal is NRZ (non-return).
zero) signal. Therefore, an NRZ-RZ converter (not shown) may be inserted before the digital-to-analog converter to perform NRZ-RZ conversion.

(Embodiment 5) Next, the configuration and operation of an optical transmission system according to Embodiment 5 will be described with reference to FIG. FIG. 6 is a configuration diagram of the optical transmission system of the present embodiment.

The optical transmission system of the present embodiment is different from the above-described optical transmission system of the first embodiment (see FIG. 1) mainly in the following two points. That is,
(1) The optical transmitter 96 has a signal input section P for inputting a pilot signal, converts the pilot signal input via the amplifier 23 into an optical signal by the semiconductor laser 38, and outputs the optical signal to the optical fiber 45. (2) The optical receiver 97 converts the optical signal from the optical fiber 45 into an electric signal by the optical / electrical converter 56 and the analog / digital converter 1 by the amplifier 66.
The point is that the signal is amplified to be a reference level (for example, 1 level) at the time of performing analog-to-digital conversion at 0, and is input to the input unit P of the analog-to-digital converter 10.

The means including the signal input section P for inputting the pilot signal corresponds to the pilot signal generating means of the present invention. The means including the input section P of the analog / digital converter 10 corresponds to the level fluctuation correcting means of the present invention.

With such a configuration, if a pilot signal corresponding to the reference level is separately provided and transmitted, the overall level fluctuation during signal transmission can be corrected, and normal analog-to-digital conversion in the optical receiver can be performed.

In this embodiment, an optical fiber for transmitting a pilot signal is separately provided.
By making the oscillation wavelengths of the semiconductor laser 7 and the semiconductor laser 38 different from each other and performing wavelength multiplexing using an optical multiplexer, transmission can be performed with one optical fiber. In that case, an optical demultiplexer is provided in the optical receiver, and the wavelength-multiplexed optical signal is wavelength-separated.

(Embodiment 6) Next, FIGS.
The configuration and operation of the optical transmission system according to the sixth embodiment will be described with reference to FIG. FIG. 7 (a)
Fig. 7B is an explanatory diagram of the time variation of the digital signal in D1, Fig. 7B is an explanatory diagram of the time variation of the digital signal in D2, and Fig. 7C is a diagram of the digital-analog converter 1;
FIG. 4 is an explanatory diagram of a time variation of an output signal into which a pilot signal is inserted.

The configuration of the optical transmission system of this embodiment is as follows.
Optical transmission system according to the fifth embodiment described above (see FIG. 6)
The configuration is the same as that described above. However, in the present embodiment, the pilot signal is generated in advance in the digital-to-analog converter of the optical transmitter, and the digital signal is generated by the input signals from D1 and D2 (see FIGS. 7A and 7B). The signal is output from the digital-to-analog converter so as to be inserted into the analog conversion signal.

As an example of the output signal, as shown in FIG. 7C, one-level pilot signals 75 and 76 are inserted and converted into RZ signals.

In the optical receiver, an output signal from the digital-to-analog converter transmitted as an optical signal is converted into an electric signal. Then, the analog-to-digital converter extracts a pilot signal from the input signal (see FIG. 7 (c)), and refers to the level to extract the pilot signal.
It performs digital conversion.

By adopting such a configuration, a pilot signal is attached and transmitted by electrical time multiplexing, and overall level fluctuation at the time of signal transmission is corrected, so that normal analog-to-digital conversion in the optical receiver can be performed. it can.

In this embodiment, the pilot signal is inserted by inserting pilot signals 75 and 76 into D
1. This was performed by finding and inserting an empty slot of the input signal from D2. However, not limited to this,
The insertion of the pilot signal may be performed, for example, by shifting input signals from D1 and D2 to actively generate an empty slot for inserting the pilot signal. Further, in the above-described embodiment, the pilot signal is converted into an RZ signal.
The present invention is not limited to this, and may not be converted into an RZ signal.

(Embodiment 7) Next, the configuration and operation of an optical transmission system according to Embodiment 7 will be described with reference to FIG. FIG. 8 is a configuration diagram of the optical transmission system of the present embodiment.

The optical transmission system of the present embodiment differs from the optical transmission system of the first embodiment (see FIG. 1) mainly in the following two points. That is,
(1) In the optical transmitter 98, a pre-modulation unit 81 for correcting waveform deterioration during optical transmission is provided between the amplifier 2 and the semiconductor laser 3. (2) In the optical reception unit 99,
The point is that a compensator 82 for correcting waveform deterioration during optical transmission is provided between the amplifier 6 and the analog / digital converter 7.

With such a configuration, waveform distortion due to the influence of chromatic dispersion and the like in the optical fiber 4 can be corrected, and normal analog-to-digital conversion can be performed in the optical receiver.

Further, a pre-modulation section and a compensation section can be provided so as to complement the frequency response of the semiconductor laser and the optical / electrical conversion section. For example, when the responsiveness on the high frequency side is low, a pre-modulation unit or a complementary unit with high responsiveness on the high frequency side is used in advance. Of course, it is not necessary to provide the premodulation unit and the complementing unit at the same time, and they may be provided in either the optical transmitter or the optical receiver.

In the above embodiment, the semiconductor laser is, for example, an InP in a wavelength band of 1.2 to 1.6 μm.
A long-wavelength laser of a system material, a semiconductor laser of a 0.98 μm band, a laser of a GaAlAs-based material having an oscillation wavelength of 0.78 μm, or the like can be used.

In the above embodiment, for example, a normal optical fiber is used as the optical fiber. This includes, for example, a normal optical fiber having a core diameter of about 10 to 300 μm. Note that either a multi-mode optical fiber or a single-mode optical fiber can be used.

In the above embodiment, the amplifier is inserted. However, if the signal level is sufficiently secured, it is not necessary to insert the amplifier.

As apparent from the above description, the present invention provides, for example, a method in which a plurality of digital signals are input to a digital-to-analog converter, and a multi-value output signal from the digital-to-analog converter is converted into an electric-optical signal. It is an optical transmitter that converts it into an optical signal and transmits it. Note that the plurality of digital signals input to the digital-to-analog converter of the optical transmitter are RZ (return to zero) signals or, if the signals are NRZ (non-return zero) signals, converted to RZ signals. You may.

Further, the present invention provides, for example, a time divider for converting a time-division multiplexed digital signal into a plurality of time-division signals, and at least one or more digital signals to which a plurality of signals from the time-divider are input. An optical transmitter that converts an analog converter and a multi-level output signal from the digital-analog converter into an optical signal by an electric-optical converter and transmits the optical signal.

Further, according to the present invention, for example, as an optical receiver for receiving an optical signal from the optical transmitter, the optical / electrical converter converts the electric signal into an electric signal, and converts the electric signal to an analog / digital converter. A plurality of parallel signals input and output from an output terminal are extracted as a plurality of transmitted digital signals.

Further, a plurality of multi-valued output signals from a plurality of digital / analog converters are converted into optical signals having different wavelengths by a plurality of electric / optical converters, and the light of each wavelength is converted into one by an optical multiplexer. An optical transmitter for transmitting the optical fiber and an optical receiver for receiving the light can also be configured. Further, a bit in a predetermined time slot of a plurality of digital signals input to the digital-to-analog converter is set to 1, and a signal from the digital-to-analog converter in the time slot is used as a pilot signal together with a multi-level output signal. An optical transmitter for transmitting and an optical receiver for receiving this light can also be configured.

Further, the present invention comprises, for example, a pilot signal source, converts a reference level signal from the pilot signal source into an optical signal having a different wavelength by an electro-optical converter, and performs wavelength multiplexing by an optical multiplexer. An optical transmitter that outputs the light and an optical receiver that receives the light can also be configured.

The present invention also includes, for example, at least one optical transmitter and at least one optical receiver according to the present invention, and has at least one optical signal input / output unit.
An optical transmission device for transmitting and receiving an optical signal.

The present invention also relates to an optical transmission system comprising, for example, a combination of the optical transmitter, optical receiver and optical transmission device according to the present invention.

In the above-described embodiment, the M kinds of binary or multi-level signals of the present invention are binary digital signals of two or four systems that take two values of 0 or 1. there were. However, the present invention is not limited to this, and the M kinds of binary or multi-level signals of the present invention are basically M kinds of binary or multi-level signals S ₁ ,. . . , S _M.

Further, the M kinds of signals S ₁ ,. . . , Based on a predetermined rule S _M N _(<M) types of signals T1,. . . , TN, (1) For any i (1 ≦ i ≦ M), the signal S _i is L (N ≦ L <M) vacant with M kinds of signals as elements. No groups G ₁ ,. . . , _GL , and (2) for any j (1 ≦ j ≦ N), the signal T _j
Are L non-empty groups H ₁ ,. . . , H _L , and (3) any k (1
≤ k ≤ L), the combination of the values of the signals belonging to the group H _k may be determined corresponding to any pattern of the combination of the values of the signals belonging to the group G _k .
However, since it is difficult to use a conventional digital-to-analog converter as it is as a conversion means for performing such conversion, a dedicated converter must be created. In such a case, the analog-to-digital converter on the receiving side needs to be similarly improved.

[0094] Note that signals belonging to the group H _k may be a plurality, of course. For example, five types of binary signals S ₁ ,. . . , S ₅ , consider two groups G ₁ = {S ₁ , S ₂ , S ₃ }, G ₂ = {S ₄ , S ₅ } and consider the signals S ₁ , S ₂ , S ₅ belonging to group G _{1 3} from group H ₁ to the signal a is 4 value of the signal T ₁ belonging ⁽¹⁾ and binary signal T ₁ ⁽²⁾ generates a signal S ₄ in the group G _2,
A quaternary signal T ₂ which belongs to the group H ₂ from S ₅
May be generated. In short, any k (1 ≦ k ≦ L)
On the other hand, the types of signals belonging to the group H _k need only be smaller than the types of signals belonging to the group G _k .

With such a configuration, a high-speed data rate can be ensured as an optical transmission system while reducing the responsiveness of an optical transmission device, and a low-cost optical transmission system can be constructed.

[0096]

As is apparent from the above description, the present invention has an advantage that, for example, a large-capacity transmission is possible with a simple configuration, and the required performance of an optical transmission device can be relaxed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical transmission system according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a time variation of a digital signal at D1 (FIG. 2A), an explanatory diagram of a time variation of a digital signal at D2 (FIG. 2B), and a digital signal according to the first embodiment of the present invention. -Explanatory drawing of the time variation of the time division multiplexed signal at the output of the analog converter 1 (FIG. 2 (c))

FIG. 3 is a configuration diagram of an optical transmission system according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical transmission system according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a time variation of a digital signal in D1 according to the fourth embodiment of the present invention (FIG. 5A), an explanatory diagram of a time variation of a digital signal in D2 (FIG. 5B), and FIG. -Explanatory drawing of the time variation of the time division multiplexed signal at the output of the analog converter 1 (FIG. 5 (c))

FIG. 6 is a configuration diagram of an optical transmission system according to a fifth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a time variation of a digital signal in D1 (FIG. 7A), an explanatory diagram of a time variation of a digital signal in D2 (FIG. 7B), and a digital signal according to a sixth embodiment of the present invention. FIG. 7 (c) illustrates the time variation of the output signal of the analog converter 1 into which the pilot signal is inserted.

FIG. 8 is a configuration diagram of an optical transmission system according to a seventh embodiment of the present invention.

FIG. 9 is a configuration diagram of a conventional optical transmission system.

FIG. 10 is an explanatory diagram of a conventional digital signal time variation at D1 (FIG. 10A), an explanatory diagram of a digital signal time variation at D2 (FIG. 10B), and an output of the time division multiplexer 100. (FIG. 10 (c)) is an explanatory diagram of the time variation of the time division multiplexed signal in FIG.

[Explanation of symbols]

90, 92, 94, 96, 98 Optical transmitters 91, 93, 95, 97, 99 Optical receivers 3, 31, 32, 33, 34, 37, 38 Semiconductor lasers 5, 51, 52, 53, 54, 55 , 56 Opto-electric converters 1, 11, 12 Digital-to-analog converters 7, 71, 72, 10 Analog-to-digital converters 8 DEMUX (time-division multiplexer) 9 MUX (time-division multiplexer) 4, 41, 42, 43, 44, 45 Optical fiber 35 Optical multiplexer 36 Optical demultiplexer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroyuki Asakura 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5K002 AA01 AA03 BA05 BA13 CA01 DA02 DA03 DA06 FA01 5K029 AA11 CC04 FF02 GG03 JJ01

Claims (21)

[Claims] 1. A method according to claim 1, wherein M types of signals having binary and / or multi-valued possible values are input, and N (<at least including multi-valued signals based on a predetermined rule.
M) transmitting side signal number converting means for converting into N kinds of signals; and transmitting side optical signal converting means for converting each of the N kinds of signals into an optical signal. In the conversion by the means, the combination of the values of the N types of signals is determined based on the rule in accordance with any pattern of the combinations of the values of the M types of signals. Optical transmitter. 2. The method according to claim 1, wherein the signal has at least N (<M) signals including at least a multi-level signal generated by conversion based on a predetermined rule using M types of signals whose values are binary and / or multi-level. N) types of optical signals generated by performing optical conversion on the type of signals into optical signals,
Receiving-side optical signal conversion means for performing conversion for restoring to the N types of signals; and the M types of signals based on a predetermined relationship corresponding to the rule from the respective restored N types of signals. Receiving-side signal number converting means for performing conversion for restoring the number of signals. At the time of the conversion by the receiving-side signal number converting means, a combination of values of the M types of signals is determined based on the relationship. An optical receiver characterized in that it is determined according to any one of patterns of combinations of values of types of signals. 3. The apparatus according to claim 1, further comprising a dividing unit configured to generate the M types of binary and / or multi-level signals by dividing an externally input signal. Optical transmitter. 4. The M kinds of binary and / or multi-level signals are generated by dividing an externally input signal, and the restored M kinds of binary and / or multi-level signals are generated. 3. The optical receiver according to claim 2, further comprising a synthesizing means for synthesizing the signals of (i) and (ii) to restore the externally input signal. 5. The conversion of the N types of signals into the optical signals is performed using light of different wavelengths, and the N types of optical signals converted using the light of different wavelengths are , N ′ (<N) types of optical signals, and transmission to the receiving side is performed using the multiplexed N ′ (<N) types of optical signals. The optical transmitter according to claim 1, wherein: 6. The N types of optical signals are generated by conversion using light of different wavelengths, multiplexed with N ′ types of optical signals and transmitted, and the multiplexed and transmitted N 3. The optical receiver according to claim 2, further comprising: separating means for recovering said N kinds of optical signals by separating 'type' optical signals. 7. A pilot signal generating means for generating a pilot signal to be transmitted to a receiving side based on a predetermined rule and used for correcting a level fluctuation of the optical signal. Item 2. The optical transmitter according to Item 1. 8. A level fluctuation correction for correcting a level fluctuation of the optical signal by using a pilot signal transmitted from a transmitting side and used for correcting a level fluctuation of the optical signal. 3. The optical receiver according to claim 2, further comprising means. 9. The optical transmitter according to claim 1, further comprising a pre-modulation unit for compensating waveform degradation of the optical signal with respect to the N types of signals. 10. The optical receiver according to claim 2, further comprising an equalizing means for compensating for the waveform deterioration with respect to the restored N types of signals. 11. The pilot signal is generated by using a bit in a predetermined time slot of the M types of binary and / or multilevel signals as a reference value, and based on the predetermined rule, a receiving side. The method of claim 7, wherein transmitting to the receiver means that the signal is transmitted to a receiving side as a part of the optical signal by using the conversion of the N types of signals into the optical signal. Optical transmitter. 12. The pilot signal is generated by using a bit in a predetermined time slot of the M types of binary and / or multi-level signals as a reference value. 9. The optical receiver according to claim 8, wherein a reference value in a predetermined time slot is extracted. 13. The conversion of the pilot signal into an optical signal, and the transmission of the pilot signal to the receiving side based on the predetermined rule means that the pilot signal is transmitted to the receiving side using a dedicated optical transmission path. The optical transmitter according to claim 7, wherein: 14. The pilot signal is converted into an optical signal and transmitted to a receiving side using a dedicated optical transmission line. To use the pilot signal means to use the dedicated optical transmission line. 9. The optical receiver according to claim 8, wherein the pilot signal is recovered from the optical signal transmitted to the receiving side and used. 15. When the pilot signal is converted into an optical signal and is transmitted to a receiving side based on the predetermined rule, the pilot signal is combined with all or a part of the N types of optical signals. And transmitting the data to a receiving side.
An optical transmitter as described. 16. The pilot signal is converted into an optical signal, is combined with all or a part of the N types of optical signals, is transmitted to a receiving side, and uses the pilot signal. The optical signal transmitted to the receiving side after being multiplexed with all or a part of the N types of optical signals, and restoring and using the pilot signal. Item 10. The optical receiver according to Item 8. 17. The optical transmitter according to claim 1, wherein the M kinds of binary and / or multilevel signals are RZ (return to zero) signals. 18. An M type signal having two and / or multi-valued possible values of a signal is input, and based on a predetermined rule, at least N (<< including at least a multi-valued signal)
M) transmitting side signal number converting means for converting into N kinds of signals; and transmitting side optical signal converting means for converting each of the N kinds of signals into an optical signal. In the conversion by the conversion unit, the combination of the values of the N types of signals is based on the rule, and the optical transmitter is determined corresponding to any pattern of the combinations of the values of the M types of signals. Receiving-side optical signal converting means for performing conversion for restoring the N types of optical signals generated by the conversion by the transmitting-side optical signal converting means into the N types of signals, respectively; Receiving signal number conversion means for performing conversion for restoring the M types of signals based on a predetermined relationship corresponding to the rule from the signals of the type; and To conversion At the time,
The combination of the values of the M types of signals is an optical receiver that is determined based on the relationship according to any pattern of the combinations of the values of the N types of signals, An optical transmission system, comprising: an optical transmission path for transmitting an optical signal, the optical transmission path being connected to an optical receiver. 19. The M kinds of binary and / or multi-level signals refer to the M kinds of binary and / or multi-level signals S ₁ ,. . . , S _M , and the N kinds of signals including the at least multi-valued signal include the N kinds of signals T ₁ ,. . . , T _N , and that the combination of the values of the N types of signals is determined in accordance with any pattern of the combinations of the values of the M types of signals based on the rule: I (1
≦ i ≦ M), the signal S _i is composed of L (N ≦ L <M) groups G ₁ ,. . . ,
_GL , and (2) for any j (1 ≦ j ≦ N), the signal T _j is composed of L groups H ₁ ,. . . Belongs to one of H _L, (3) for any k (1 ≦ k ≦ L) , the type of signals belonging to the group H _k less than the kind of signals belonging to the group G _k, Group H _k the optical transmission system according to claim 18, wherein the combination of the values of each signal, characterized in that is determined in response to any pattern of combination of values of the signals belonging to the group G _k belonging to. 20. The method according to claim 20, wherein the type of the signal belonging to the group H _k is smaller than the type of the signal belonging to the group G _k .
L = N, and the signals belonging to the group H _k are only one kind of the signal T _k , and the combination of the values of the signals belonging to the group H _k is the combination of the values of the signals belonging to the group G _k Is determined in accordance with any of the patterns, the value of the signal T _{k at} a predetermined timing is determined by the group G _{k at} that timing.
20. The method is determined in a one-to-one correspondence with any one of combinations of signal values belonging to
The optical transmission system according to the above. 21. An optical transmission device comprising: the optical transmitter according to claim 1; and the optical receiver according to claim 2.