JPH10285064A - Distortion compensation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the distortion compensation device by which distortion is uniformly compensated without dispersion for each frequency component, the circuit configuration and its fineadjustment are facilitated. SOLUTION: Based on the pre-distortion system, a distortion signal generated in advance by a distortion generating section 200 has a different delay from each frequency component (frequency deviation in a delay). A delay frequency deviation adjustment section 700 gives a frequency deviation of a same delay as a frequency deviation of a delay provided by a nonlinear circuit being a component of the distortion generating section 200. A 1st phase inversion synthesis section 500 synthesizes the 1st frequency multiplex signal and a distortion signal in a relation of an inverted phase. An optical modulation section 600 generates an optical modulation signal with an output signal from the 1st phase inversion synthesis section 500.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distortion compensating apparatus, and more particularly, to a distortion compensating apparatus for compensating, using a predistortion method, a distortion generated when performing an optical modulation or the like on a frequency-multiplexed signal. About.

[0002]

2. Description of the Related Art In optical communication, generally, a transmitting side transmits an optically modulated signal in which the intensity of light is modulated by a signal to be transmitted, and a receiving side demodulates the optically modulated signal and converts the original signal. obtain. By the way, light emitting elements such as semiconductor lasers
When the applied current is changed, the power of the optical output also changes.
An optical modulation signal is generated using such a phenomenon.
However, the optical modulation signal is distorted due to the non-linearity of the semiconductor laser. The effect of this distortion is relatively small when transmitting a digital signal, but is noticeable when transmitting an analog signal, and there is a problem in that the transmission quality of data is deteriorated.

One of the methods for solving this problem is a pre-distortion method. In this method, a distortion signal that cancels distortion generated by a semiconductor laser or the like is added to the transmission signal. Therefore, when the optical modulation is performed, the distortion signal cancels out the distortion caused by the nonlinearity. Thus, the data transmission quality is not degraded. Hereinafter, an optical transmission device using a predistortion method will be described with reference to FIG.

In FIG. 5, a branch unit 100 branches a transmission signal (main signal) into two by an optical modulation unit 600 composed of a semiconductor laser or the like. One of the two branched main signals is the first
And is input to the phase inversion multiplexing unit 500, and the other is output to the second path. On the second path, a distortion generator 200, an amplitude adjuster 300, and a delay amount adjuster 400 are arranged. When the main signal is input, the distortion generation unit 200 generates a signal (distortion signal) that cancels out the distortion generated in the optical modulation unit 600. The amplitude adjustment unit 300
The amplitude level of the distortion signal is adjusted so that the amplitude level becomes the same as the distortion generated when the optical modulation unit 600 generates the optical modulation signal. The delay amount adjustment unit 400 adjusts the delay amount of the distortion signal so that the delay amount becomes the same as that of the main signal propagating through the first path. The phase inversion multiplexing section 500 adds the main signal and the distortion signal so as to have a phase difference of 180 degrees. Therefore, the output signal from the phase inversion multiplexing unit 500 has the same amplitude level as the distortion generated when the optical modulation signal is generated in the optical modulation unit 600 by the main signal, and has the opposite phase. Signal. Therefore, in the optical modulation section 600, the distortion caused by the non-linearity of the semiconductor laser is canceled by the distortion signal, so that no distortion occurs in the optical modulation signal.

However, in the optical transmission device shown in FIG. 5, the nonlinear circuit constituting the distortion generating section 200 has a different delay amount for each frequency component instead of a constant delay amount over a wide band. Therefore, when transmitting a wideband signal, for example, a frequency-division multiplexed signal, the delay amount adjustment unit 400 determines the amount of delay of the distortion signal over the entire frequency band by using the main signal (frequency-division multiplexed signal) propagated on the first path. ), It is difficult to equalize the delay amount, that is, to eliminate the frequency deviation. Therefore, in the optical transmission device shown in FIG. 5, there has been a problem that a considerable difference occurs in the effect of distortion compensation for each frequency component such as a frequency multiplexed signal.

Therefore, a method of applying a phase equalizer to the optical transmitter shown in FIG. 5 has been adopted. Below,
An optical transmission device using a phase equalizer will be described with reference to FIG. 6, the optical transmission device is the same as the configuration shown in FIG. 5 except that the optical transmission device includes a phase equalization unit 601.
The same reference numerals are given and the description is omitted. The phase equalizing unit 601 includes a coil, a resistor, and a capacitor. The phase equalizing unit 601 equalizes the frequency deviation of the delay amount of the distortion signal generated by the distortion generating unit 200 at low, middle, and high frequencies. Thus, the frequency deviation of the amount of delay of the distortion signal is corrected.

[0007]

However, in the optical transmitter shown in FIG. 6, it is difficult to completely equalize the frequency deviation of the delay amount generated in the nonlinear circuit constituting the distortion generating section 200, and it is difficult to perform phase equalization. The circuit configuration of the unit itself is complicated, and there is a problem that fine adjustment is required. Therefore, the present invention is capable of uniformly compensating distortion without variation in each frequency component when performing frequency modulation or the like on a frequency multiplexed signal by a predistortion method,
It is another object of the present invention to provide a distortion compensating device that can easily perform a fine adjustment of a circuit configuration.

[0008]

A first aspect of the present invention is a distortion compensating apparatus for compensating, using a pre-distortion method, distortion generated when a frequency-multiplexed signal is modulated by a predetermined method. A first branching unit that branches the frequency-multiplexed electric signal into first and second frequency-multiplexed signals and outputs the first and second frequency-multiplexed signals to the first and second paths; A delay amount frequency deviation adjusting unit for giving a frequency deviation of the delay amount to one frequency multiplexed signal; and a distortion generating unit for generating and outputting a distortion signal using the second frequency multiplexed signal propagated on the second path. A first phase inversion multiplexing unit that multiplexes the distortion signal and the first frequency multiplexed signal output from the delay amount frequency deviation adjustment unit so as to have a phase difference of 180 degrees.

When using the pre-distortion method,
When the distortion signal is generated from the frequency multiplexed signal, a frequency deviation of the delay amount occurs. However, according to the first aspect, the delay amount frequency deviation adjuster gives the first frequency multiplexed signal a frequency deviation of the delay amount. The first phase inversion multiplexing unit multiplexes the first frequency multiplexed signal and the distortion signal as described above so as to have a phase difference of 180 degrees. When the output signal from the first phase inversion multiplexing unit is modulated by the above-described predetermined method, the distortion compensation amount of each wave of the frequency multiplexed signal can be made uniform.

[0010] In a second aspect based on the first aspect, the apparatus further comprises an amplitude adjuster for adjusting the amplitude level of the distortion signal.

According to the second aspect of the present invention, the amplitude level of the distortion signal can be adjusted. The distortion compensation amount of each wave of the multiplex signal can be made more uniform.

A third invention according to the first or second invention, further comprises a delay amount adjusting section for adjusting a delay amount of the distortion signal.

According to the third aspect, the absolute value of the delay amount of the distortion signal can be adjusted. Adjustment of such an absolute value is simple as is well known. This facilitates the circuit configuration of the distortion compensator and its fine adjustment.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the distortion generating section converts the input signals from the first branching section so that the amplitude levels are equal and opposite in phase. 1
And a phase inversion branching unit for branching to the second signal, first and second nonlinear circuits for giving the same characteristics as the frequency deviation to the first and second signals, and the first and second nonlinear circuits. A multiplexing unit that multiplexes the output signals, wherein the first and second nonlinear circuits set operating conditions so that the amplitude levels of the signals output from the multiplexing units are the same, and Is characterized in that the output signal comprises only the second-order distortion component of the input signal.

According to the fourth aspect of the present invention, when the output signal from the first phase inversion multiplexing section is modulated by the above-mentioned predetermined method, the compensation amount of the one-wave one-wave secondary distortion of the frequency multiplexed signal is obtained. Can be made uniform.

In a fifth aspect based on the first to third aspects, the distortion generating section branches the input signal from the first branching section into two and outputs the signal to the first and second paths. And the branch of
The signal input via the second path is split into two so that the amplitude levels are equal and opposite phases,
Phase inverting / branching unit that outputs to the next path, first and second nonlinear circuits that give the same characteristics as frequency deviation to signals that propagate through the primary and secondary paths, and first and second nonlinear circuits A second phase inversion multiplexing unit for multiplexing the output signals from the first and second signals in opposite phases, a signal propagating in the first path, and an output signal from the second phase inversion multiplexing unit in opposite phases And a first and second nonlinear circuit,
The operating conditions are set so that the amplitude levels of the signals output from the respective units are the same, and the output signal from the second phase inversion multiplexing unit is composed of the main signal of the input signal and its third-order distortion component. And that the output signal from the third phase-inversion multiplexing unit is composed of only the third-order distortion component of the input signal.

According to the fifth aspect of the present invention, when the output signal from the first phase inversion multiplexing unit is modulated by the above-mentioned predetermined method, the compensation amount of the third-order distortion of one wave per wave of the frequency multiplexed signal is obtained. Can be made uniform.

According to a sixth aspect of the present invention, in the fourth or fifth aspect, the same nonlinear circuit is used for the delay amount frequency deviation adjusting section and the first and second nonlinear circuits.

According to the sixth aspect of the present invention, it is possible to easily equalize the amount of distortion compensation for each wave of the frequency multiplexed signal.

In a seventh aspect based on the sixth aspect, the nonlinear circuit of the delay amount frequency deviation adjusting section operates in a linear region, and the frequency deviation given by the delay amount frequency deviation adjusting section is such that the distortion generating section is internally provided. The present invention is characterized in that it does not deviate from the frequency deviation of the delay amount caused by the nonlinear circuit including, and does not cause a distortion component in the output signal from the nonlinear circuit of the delay amount frequency deviation adjusting unit.

According to the seventh aspect, when the output signal from the first phase inversion multiplexing section is modulated by the above-mentioned predetermined method, the distortion compensation amount of each wave of the frequency multiplexed signal can be made more uniform. can do.

In an eighth aspect based on the second aspect, the delay amount frequency deviation adjusting section is constituted by a non-linear circuit, and the distortion generating section converts the input signal from the first branching section into a signal having an amplitude level. First and second so that they are equal and opposite in phase.
A phase inverting / branching unit that branches to the first signal, a first and a second nonlinear circuit that gives the first and second signals the same characteristics as the frequency deviation, and an output signal from the first and the second nonlinear circuit. A multiplexing unit for multiplexing, the first and second nonlinear circuits set operating conditions so that the amplitude levels of the signals output from the multiplexing unit are the same, and output signals from the multiplexing unit. Is that only the second-order distortion component of the input signal is included, and the amplitude adjustment unit, if the output signal from the nonlinear circuit includes a distortion component, cancels the distortion signal with the distortion signal so that the distortion signal cancels the distortion component. The amplitude level is adjusted.

According to the eighth aspect, even if a distortion is generated by the delay amount frequency deviation adjusting section, the distortion is compensated by the distortion signal. This facilitates the setting of the operation conditions of the delay amount frequency deviation adjuster. In addition, this first
When modulated by the above-mentioned predetermined method by the output signal from the phase inversion multiplexing unit, the frequency multiplexed signal has two
The compensation amount of the secondary distortion can be made uniform.

In a ninth aspect based on the second aspect, the delay amount frequency deviation adjusting section is constituted by a non-linear circuit, and the distortion generating section branches the input signal from the first branching section into two. , A second branch for outputting to the first and second paths,
The signal input via the second path is split into two so that the amplitude levels are equal and opposite phases,
Phase inverting / branching unit that outputs to the next path, first and second nonlinear circuits that give the same characteristics as frequency deviation to signals that propagate through the primary and secondary paths, and first and second nonlinear circuits A second phase inversion multiplexing unit for multiplexing the output signals from the first and second signals in opposite phases, a signal propagating in the first path, and an output signal from the second phase inversion multiplexing unit in opposite phases And a first and second nonlinear circuit,
The operating conditions are set so that the amplitude levels of the signals output from the respective units are the same, and the output signal from the second phase inversion multiplexing unit is composed of the main signal and the third-order distortion component of the input signal. And that the output signal from the third phase inversion multiplexing unit includes only a third-order distortion component of the input signal. The amplitude adjustment unit determines that the output signal from the nonlinear circuit includes a distortion component. The amplitude level of the distortion signal is adjusted so that the distortion component is canceled by the signal.

According to the ninth aspect, even if a distortion is generated by the delay amount frequency deviation adjuster, the distortion is compensated for by the distortion signal. This facilitates the setting of the operation conditions of the delay amount frequency deviation adjuster. In addition, this first
Is modulated by the above-mentioned predetermined method using the output signal from the phase inversion multiplexing unit of FIG.
The compensation amount of the secondary distortion can be made uniform.

A tenth aspect of the present invention is a distortion compensating apparatus for compensating, using a predistortion method, a distortion generated when a frequency-multiplexed signal is modulated by a predetermined method. A first branching unit that splits the signal into first and second frequency multiplexed signals and outputs the signals to the first and second paths and a first frequency multiplexed signal that propagates along the first path has a delay amount. A delay amount frequency deviation adjusting unit for giving a frequency deviation, a distortion generating unit for generating and outputting a distortion signal using a second frequency multiplexed signal propagated on a second path, a distortion signal, and a delay amount frequency deviation A first phase inversion multiplexing unit that multiplexes the first frequency multiplexed signal output from the adjustment unit so as to have a phase difference of 180 degrees, and the distortion generation unit propagates through the second path The second frequency multiplexed signal is split into two to And a second branching section for outputting to the secondary path and a non-linear circuit having a frequency characteristic of the same delay amount as that of the delay amount frequency deviation adjusting section and including a distortion component in a signal propagating through the primary path and outputting the signal. A second amplitude adjustment unit that adjusts and outputs the amplitude level of a signal that propagates through the secondary path, and a second delay amount adjustment unit that adjusts and outputs the delay amount of a signal that propagates through the secondary path. A second phase inversion multiplexing unit that multiplexes signals propagating in the primary path and the secondary path in opposite phases.

According to the tenth aspect, when the output signal from the first phase inversion multiplexing section is modulated by the above-mentioned predetermined method, the compensation amount of each wave of the frequency multiplexed signal is made uniform. be able to.

According to an eleventh aspect, in the tenth aspect,
The same non-linear circuit is used for the delay amount frequency deviation adjusting unit and the non-linear circuit.

According to the eleventh aspect, it is possible to easily equalize the amount of distortion compensation for each wave of the frequency multiplexed signal.

According to a twelfth aspect, in the tenth aspect,
The delay amount frequency deviation adjusting unit is configured by a non-linear circuit, and the output signal from the second phase inversion multiplexing unit is
Consisting of only the second and third order distortion components of the frequency multiplexed signal of
The nonlinear circuit that constitutes the delay frequency deviation adjustment unit is
The operating condition is set such that the third-order distortion component is canceled by the first phase inversion multiplexing unit from the output signal from the second phase inversion multiplexing unit.

According to the twelfth aspect, even if the distortion is generated by the delay amount frequency deviation adjusting section, the distortion is compensated by the distortion signal. This facilitates the setting of the operation conditions of the delay amount frequency deviation adjuster. Further, when the output signal from the first phase-inversion multiplexing unit is modulated by the above-mentioned predetermined method, it is possible to make uniform the amount of compensation for one-wave one-wave secondary distortion of the frequency multiplexed signal.

According to a thirteenth aspect, in the tenth aspect,
The delay amount frequency deviation adjusting unit is configured by a non-linear circuit, and the output signal from the second phase inversion multiplexing unit is
Consisting of only the second and third order distortion components of the frequency multiplexed signal of
The nonlinear circuit that constitutes the delay frequency deviation adjustment unit is
The operating condition is set so that the second-order distortion component is canceled by the first phase inversion multiplexing unit from the output signal from the second phase inversion multiplexing unit.

According to the thirteenth aspect, even if the distortion is generated by the delay amount frequency deviation adjusting section, the distortion is compensated by the distortion signal. This facilitates the setting of the operation conditions of the delay amount frequency deviation adjuster. Further, when the output signal from the first phase inversion multiplexing unit is modulated by the above-mentioned predetermined method, the compensation amount of the third-order distortion of each wave of the frequency multiplexed signal can be made uniform.

[0034]

FIG. 1 is a diagram showing a configuration of an optical transmission apparatus to which a distortion compensator (see inside a dotted line) according to a first embodiment of the present invention is applied. In FIG. 1, the distortion compensating apparatus includes a first branching unit 100, a distortion generating unit 200, a first amplitude adjusting unit 300, and a first delay amount adjusting unit 400.
, A first phase inversion multiplexing unit 500, and a delay amount frequency deviation adjusting unit 700. The first branch 100
A main signal (frequency multiplexed signal) that is input from the outside and is to be optically modulated by the optical modulator 600 including a semiconductor laser or the like
To the first and second frequency multiplexed signals. The first frequency multiplexed signal is output on a first path, and the second frequency multiplexed signal is output on a second path. On the first path, a delay amount frequency deviation adjusting unit 700 is provided.
The distortion generator 200 and the first amplitude adjuster 30
Zero and first delay amount adjustment units 400 are provided. When the second frequency multiplexed signal is input, the distortion generator 200 generates a signal (hereinafter, referred to as a “distortion signal”) that cancels the distortion generated in the optical modulator 600. The distortion signal has a different delay amount (frequency deviation of the delay amount) for each frequency component. The first amplitude adjustment unit 300 is a signal having the same amplitude as the distortion generated when the optical modulation unit 600 disposed at the subsequent stage of the distortion compensator generates an optical modulation signal.
Adjust the amplitude level of the distortion signal. The first delay amount adjustment section 400 adjusts the delay amount of the distortion signal so that the delay amount becomes the same as that of the first frequency multiplexed signal propagating through the first path. The delay amount frequency deviation adjusting section 700 gives the same frequency deviation of the delay amount of the distortion signal propagating through the second path to the first frequency multiplexed signal propagating through the first path. The first phase inversion multiplexing section 500 adds the first frequency multiplexed signal given the frequency deviation of the delay amount and the distortion signal so as to have a phase difference of 180 degrees and outputs the sum. Therefore, the first phase inversion multiplexing unit 5
The output signal from the first frequency multiplexed signal is
Having the same amplitude level as the distortion generated when the optical modulation signal is generated in the optical modulation unit 600 using the frequency multiplexed signal of
In addition, it is composed of a distortion signal having the opposite phase to the distortion. Therefore, in the optical modulation section 600, the distortion caused by the non-linearity of the semiconductor laser is canceled by the distortion signal, so that the optical modulation signal does not cause distortion.

Incidentally, the distortion signal is given a frequency deviation of the delay amount by a nonlinear circuit constituting the distortion generating section 200. That is, the delay amount differs for each frequency component of the distortion signal. However, the delay amount frequency deviation adjusting unit 700 gives the same characteristic as the characteristic of the frequency deviation of the delay amount provided by the nonlinear circuit to the first frequency multiplexed signal. Therefore, the first delay amount adjusting unit 400
Then, only the absolute value of the delay amount needs to be adjusted. As a result, even when optically modulating a frequency multiplexed signal, it is possible to provide a distortion compensating device that can uniformly compensate for distortion for each frequency component without variation, and that can easily adjust the circuit configuration.

The branching ratio of the first branching section 100 does not need to be specified. However, the light modulator 600
If the amplitude level of the distortion generated in the first branching unit 100 is known in advance and the magnitude of the output (distortion signal) with respect to the input (second frequency multiplexed signal) of the distortion generating unit 200 can be grasped, By setting the branch ratio appropriately,
The first amplitude adjuster 300 can be omitted. Also, by setting the first path shown in FIG. 1 to an appropriate length, the first delay amount adjustment unit 400 can be omitted.

The delay amount frequency deviation adjusting unit 700
Is constituted by a non-linear circuit, the non-linear circuit is operated in a linear region, and the delay amount frequency deviation adjusting unit 700 is used.
It is desirable that the output signal from the PC should not be distorted.
However, even when the output signal is distorted, the distortion generated in the output signal can be canceled by the distortion signal generated by the distortion generating section 200. However,
In this case, it is necessary to make the amplitude level of the distortion signal after canceling out the distortion generated in the nonlinear circuit the same as the amplitude level of the distortion generated in the optical modulator 600.

Next, an example of the configuration of the distortion generator 200 will be described with reference to FIG. 2 or FIG. FIG. 2 shows a distortion generator 200.
FIG. 2 is a block diagram showing a first configuration example (see FIG. 1).
2, the distortion generator 200 includes a first phase inverting / branching unit 201, a first nonlinear circuit 202, a second nonlinear circuit 203, and a multiplexing unit 204. (Comprising only the second-order distortion component). The phase inversion splitter 201 splits the second frequency multiplexed signal input from the first splitter 100 into two, and outputs the split signal to the primary path and the secondary path. The signals output to the primary path and the secondary path have a phase difference of 180 degrees, and are input to the first nonlinear circuit 202 and the second nonlinear circuit 203.
Output signals from the first nonlinear circuit 202 and the second nonlinear circuit 203 have a main signal, a second-order distortion component, and a third-order distortion component, respectively. The main signal and the third-order distortion component of both have a phase difference of 180 degrees, but the secondary distortion components of both have the same phase.
Therefore, when the output signals from the first nonlinear circuit 202 and the second nonlinear circuit 203 are multiplexed by the multiplexing unit 204, the main signal and the third-order distortion component are canceled, and only the second-order distortion component is output as a distortion signal. Is done.

FIG. 3 is a block diagram showing a second configuration example of the distortion generator 200 (see FIG. 1). In FIG. 3, the distortion generating section 200 includes a second branching section 301, a phase inversion branching section 302, a first nonlinear circuit 303, and a second
And a second phase inversion multiplexing unit 305
, A second amplitude adjustment unit 306, a second delay amount adjustment unit 307, and a third phase inversion multiplexing unit 308, and generates a distortion signal (consisting of only a third-order distortion component). . The second branching unit 301 branches the second frequency multiplexed signal input from the first branching unit 100 into two, and outputs the resulting signal to the first path and the second path. The phase inversion branching unit 302 branches the second frequency multiplexed signal input from the second branching unit 301 via the first path into two, and outputs it to the primary path and the secondary path. The signals output to the primary path and the secondary path have a phase difference of 180 degrees, and are input to the first nonlinear circuit 303 and the second nonlinear circuit 304.
Output signals from the first nonlinear circuit 303 and the second nonlinear circuit 303 have a main signal, a second-order distortion component, and a third-order distortion component, respectively. Both the main signal and the third-order distortion component have a phase difference of 180 degrees, but the second-order distortion component has the same phase. Therefore, the first nonlinear circuit 202 and the second nonlinear circuit 2
When the output signal from the third unit 03 is multiplexed by the second phase inversion multiplexing unit 305 with an opposite phase relationship, only the second-order distortion component is canceled, and the main signal and the third-order distortion component are output. The second amplitude adjusting section 306 transmits the amplitude level of the main signal included in the output signal from the first phase inversion / multiplexing section 305 to the third phase inversion / multiplexing section 308 through the first path. Second input
Is adjusted to be the same as the amplitude level of the frequency multiplexed signal. The second delay amount adjustment unit 307 determines the delay amount of the output signal from the second amplitude adjustment unit 306 by the first delay amount.
Is adjusted so as to be equal to the delay amount of the second frequency multiplexed signal propagating through the path. The third phase inversion multiplexing section 308 multiplexes the second frequency multiplexed signal propagating in the first path and the output signal from the second delay amount adjustment section 307 in an opposite phase relationship. Since the main signal of the second frequency multiplexed signal and the main signal of the output signal from the second delay amount adjusting unit 307 have the same amplitude level and the same delay amount, only the main signal is canceled and the third-order distortion component is distorted. Are output from the third phase inversion multiplexing unit 308.

FIG. 4 is a block diagram showing an overall configuration of a distortion compensating apparatus according to a second embodiment of the present invention.
In particular, the third of the distortion generator 200 included in the distortion compensator is
Is shown. In the distortion compensating apparatus shown in FIG. 4, those corresponding to the configuration shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Here, the distortion generator 20
0 indicates a second branching unit 401, a nonlinear circuit 402 having the same delay amount frequency deviation characteristic as the nonlinear circuit constituting the delay amount frequency deviation adjusting unit 700, a second amplitude adjusting unit 403, 2, a delay amount adjustment unit 404,
The second phase inversion / multiplexing unit 405 can generate a distortion signal including second-order and third-order distortions.

In the distortion generating section 200, the second branch section 4
01 splits the second frequency multiplexed signal input from the first splitter 100 into two, and outputs it to the primary path and the secondary path. On this primary path, a nonlinear circuit 402
On the secondary path, a second amplitude adjustment unit 403 and a second delay amount adjustment unit 404 are arranged. Non-linear circuit 402
Outputs a signal having second and third order distortion components based on the input second frequency multiplexed signal. Also, the second amplitude adjustment unit 403 sets the amplitude level of the second frequency multiplexed signal propagating through the secondary path to be the same as the amplitude level of the main signal of the signal output from the nonlinear circuit 402. adjust. The second delay amount adjustment unit 404 adjusts the delay amount of the second frequency multiplexed signal propagating through the secondary path so that it becomes the same as the delay amount of the signal output from the nonlinear circuit 402. The second phase inversion multiplexing unit 405 multiplexes the output signals from the non-linear circuit 402 and the second delay amount adjustment unit 404 with an opposite phase relationship. Therefore, in the output signal from the second phase inversion / multiplexing unit 405, only the main signal of the output signal from the nonlinear circuit 402 is canceled, and the second-order distortion component and the third-order distortion component are output as distortion signals.

However, the operating conditions (such as bias voltage) of the nonlinear circuit 402 are such that when only the second-order distortion component generated in the optical modulation section 600 (see FIG. 1) is compensated, the output signal from the nonlinear circuit 402 includes the main signal and the output signal. It is desirable to set so as to include only the second-order distortion component. Also, the light modulator 6
In the case where only the third-order distortion component generated in 00 is compensated, it is desirable to set so that the output signal from the nonlinear circuit 402 is only the main signal and the third-order distortion component. Thus, by inputting the output signal from the nonlinear circuit 402 and the second frequency multiplexed signal whose amplitude level and delay amount are adjusted and propagates the secondary path to the phase inversion multiplexing unit 405, The output signal from the phase inversion multiplexing unit 405 can obtain only a distortion component to be compensated in the optical modulation unit 600 according to the above-described operating conditions.

The delay amount frequency deviation adjusting unit 700
When operating the nonlinear circuit that composes in the nonlinear region,
The first frequency multiplexed signal input to first phase inversion / multiplexing section 500 includes a distortion component, and the distortion signal output from distortion generation section 200 shown in FIG. If the first phase inversion multiplexing unit 500 includes the first
Is not completely canceled out. When the distortion generator 200 and the delay amount frequency deviation adjuster 700 are adjusted in this way, a distortion component remains in the first frequency multiplexed signal input to the optical modulator 600. If the distortion component is left, the optical modulation signal generated by the optical modulator 600 composed of a non-linear semiconductor laser or the like will not be distorted.

In the above embodiment, the case where the present distortion compensator is applied to optical communication has been described.
However, the present distortion compensation apparatus is not limited to optical communication, but can be applied to all communication using a predistortion method. Further, in the present distortion compensation device, as a nonlinear circuit, an element having a nonlinear relationship between the input signal and the output signal, for example, a diode,
FETs or transistors can be used.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an optical transmission device to which a distortion compensation device according to a first embodiment of the present invention has been applied.

FIG. 2 is a block diagram illustrating a first configuration example of a distortion generator 200 (see FIG. 1).

FIG. 3 is a block diagram illustrating a second configuration example of the distortion generator 200 (see FIG. 2).

FIG. 4 is a block diagram illustrating an overall configuration of a distortion compensating apparatus according to a second embodiment of the present invention, and particularly illustrates a distortion generating unit 20;
0 shows a third configuration example.

FIG. 5 is a block diagram illustrating a configuration of an optical transmission device to which a conventional distortion compensator (first configuration example) is applied.

FIG. 6 is a block diagram illustrating a configuration of an optical transmission device to which a conventional distortion compensation device (second configuration example) is applied.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 first branching section 200 distortion generating section 300 first amplitude adjusting section 400 first delay amount adjusting section 500 first phase inversion multiplexing section 600 optical modulation section 700 delay amount frequency deviation Adjustment units 201, 302... Second phase inversion branching units 202, 303... First nonlinear circuits 203, 304... Second nonlinear circuits 204. 403: second amplitude adjustment section 307, 404: second delay amount adjustment section 308: third phase inversion multiplexing section 401: second branch section 402: nonlinear circuit

Claims (13)

[Claims] A first branching unit that branches the frequency-multiplexed electric signal into first and second frequency-multiplexed signals and outputs the first and second frequency-multiplexed signals to first and second paths; To the first frequency multiplexed signal that propagates
A delay amount frequency deviation adjuster that provides a frequency deviation of the delay amount; a distortion generator that generates and outputs a distortion signal using a second frequency multiplexed signal that propagates on the second path; A first phase inversion multiplexing unit that multiplexes the first frequency multiplexed signal output from the delay amount frequency deviation adjustment unit with a phase difference of 180 degrees.
Distortion compensator. 2. The distortion compensator according to claim 1, further comprising an amplitude adjustment unit that adjusts an amplitude level of the distortion signal. 3. The distortion compensator according to claim 1, further comprising a delay amount adjusting unit that adjusts a delay amount of the distortion signal. 4. A phase inverting branching unit for branching an input signal from the first branching unit into first and second signals so that amplitude levels are equal and opposite in phase. A first and a second nonlinear circuit for giving the same characteristics to the first and second signals as the frequency deviation; and a multiplexing unit for multiplexing output signals from the first and the second nonlinear circuits. Wherein the first and second nonlinear circuits set operating conditions such that the amplitude levels of the signals output from the first and second nonlinear circuits are the same, and the output signal from the multiplexing unit is the input signal The distortion compensator according to claim 1, wherein the distortion compensator comprises only a second-order distortion component. 5. The distortion generator, further comprising: a second branching unit that branches the input signal from the first branching unit into two and outputs the signals to first and second paths; A phase inversion branching unit that divides a signal input through the oscillating unit into two signals so that the amplitude levels are equal and opposite phases, and outputs the signals to a primary path and a secondary path, and propagates the primary path and the secondary path. First and second non-linear circuits for giving the same characteristic to the signal as the frequency deviation, and a second phase inversion multiplexing unit for multiplexing the output signals from the first and second non-linear circuits in opposite phases And a third phase inversion multiplexing unit that multiplexes a signal propagating through the first path and an output signal from the second phase inversion multiplexing unit in opposite phases. The second nonlinear circuit sets the operating conditions so that the amplitude levels of the signals output from the respective circuits are the same. The output signal from the second phase inversion multiplexing unit is composed of a main signal of the input signal and a third-order distortion component thereof; and the output signal from the third phase inversion multiplexing unit is 4. The distortion compensator according to claim 1, wherein the distortion compensator comprises only a third-order distortion component of the input signal. 6. The distortion compensator according to claim 4, wherein the same nonlinear circuit is used for the delay amount frequency deviation adjusting unit and the first and second nonlinear circuits. . 7. The nonlinear circuit of the delay amount frequency deviation adjusting unit operates in a linear region, and the frequency deviation given by the delay amount frequency deviation adjusting unit is a delay amount generated by a nonlinear circuit included in the distortion generating unit. 7. A distortion component is not generated in the output signal from the non-linear circuit of the delay amount frequency deviation adjusting unit without deviating from the frequency deviation of the delay amount.
5. The distortion compensating device according to item 1. 8. The delay amount frequency deviation adjusting section is configured by a non-linear circuit, and the distortion generating section causes input signals from the first branching section to have equal amplitude levels and opposite phases. A phase inverting / branching unit that branches into first and second signals; first and second nonlinear circuits that give the first and second signals the same characteristics as the frequency deviation; A multiplexing unit that multiplexes an output signal from a second non-linear circuit, wherein the first and second non-linear circuits set operating conditions so that the amplitude levels of the signals output from each of the first and second non-linear circuits are the same. And that the output signal from the multiplexing unit includes only a second-order distortion component of the input signal; and the amplitude adjustment unit includes: when an output signal from the nonlinear circuit includes a distortion component, The distortion signal cancels out the distortion component. In, and in that adjusting the amplitude level of the distortion signal, the distortion compensating apparatus according to claim 2. 9. The delay amount frequency deviation adjusting section is configured by a non-linear circuit, and the distortion generating section splits an input signal from the first branching section into two and outputs first and second signals. A second branching section that outputs to the path, and a signal that is input via the second path is branched into two so that the amplitude levels are equal and opposite in phase, and are output to the primary path and the secondary path. A phase inverting / branching unit, first and second nonlinear circuits for giving the same characteristic as the frequency deviation to signals propagating through the primary path and the secondary path, and a signal from the first and second nonlinear circuits. A second phase inversion multiplexing section for multiplexing the output signals in opposite phases; a signal propagating through the first path and an output signal from the second phase inversion multiplexing section in opposite phases And a third phase inversion multiplexing unit, wherein the first and second nonlinear circuits Operating conditions are set so that the amplitude levels of the signals output from the second phase inversion and multiplexing unit are the same as the main signal of the input signal and the third-order distortion component thereof. And the output signal from the third phase inversion / multiplexing unit comprises only a third-order distortion component of the input signal; and the amplitude adjustment unit outputs the distortion signal from the nonlinear circuit. The distortion compensating apparatus according to claim 2, wherein, when including the distortion signal, the amplitude level of the distortion signal is adjusted so that the distortion component is canceled by the distortion signal. 10. A first branching unit that splits a frequency-multiplexed electric signal into first and second frequency multiplexed signals and outputs the first and second frequency-multiplexed signals to first and second paths. To the first frequency multiplexed signal that propagates
A delay amount frequency deviation adjuster that provides a frequency deviation of the delay amount; a distortion generator that generates and outputs a distortion signal using a second frequency multiplexed signal that propagates on the second path; A first frequency inversion multiplexing unit that multiplexes the first frequency multiplexed signal output from the delay amount frequency deviation adjustment unit with a phase difference of 180 degrees, and the distortion generation unit includes: A second branching unit that splits the second frequency multiplexed signal propagating through the second path into two branches and outputs the resulting signal to a primary path and a secondary path; and a delay amount equal to the delay amount frequency adjustment unit. A non-linear circuit having frequency characteristics and outputting the signal propagating through the primary path with a distortion component included therein, and a second amplitude adjusting unit adjusting and outputting the amplitude level of the signal propagating through the secondary path; Delay of a signal propagating through the secondary path Distortion compensation comprising: a second delay amount adjustment unit that adjusts and outputs an amount; and a second phase inversion multiplexing unit that multiplexes signals propagating through the primary path and the secondary path in opposite phases. apparatus. 11. The delay amount frequency deviation adjusting unit,
The distortion compensator according to claim 10, wherein the same nonlinear circuit is used as the nonlinear circuit. 12. The delay amount frequency deviation adjusting section,
The output signal from the second phase inversion multiplexing unit is a first non-linear circuit.
The nonlinear circuit constituting only the second and third order distortion components of the frequency-division multiplexed signal has a third-order distortion component from the output signal from the second phase-inversion multiplexing unit. The distortion compensating apparatus according to claim 10, wherein operating conditions are set so as to cancel each other in the first phase inversion multiplexing unit. 13. The delay amount frequency deviation adjusting section,
The output signal from the second phase inversion multiplexing unit is a first non-linear circuit.
The nonlinear circuit constituting only the second and third order distortion components of the frequency multiplexed signal of the above, wherein the nonlinear circuit constituting the delay amount frequency deviation adjusting unit converts the second order distortion component from the output signal from the second phase inversion multiplexing unit, The distortion compensating apparatus according to claim 10, wherein operating conditions are set so as to cancel each other in the first phase inversion multiplexing unit.