JPH09312610A - Optical transmitter with distortion compensation function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical transmitter to compensate decoding distortion. SOLUTION: The optical transmitter is provided with an input distributer 101, one path section 103 consisting of one distortion generating section 105, of a distributer 111 distributing a distortion signal to other path via a delay circuit 117 and of a level adjustment device 112, with other path section 104 consisting of other distortion generating section 114, of a level adjustment device 116, of a synthesizer 118 synthesizing a distortion signal and the distortion signal via the delay circuit 117, and of a level adjustment device 119, a 3rd path section 105 having a delay circuit 120 to adjust a phase difference between the one path section and the other path section 105, with a synthesizer 121 synthesizing signals of the one, other and 3rd path sections, and with a light emitting section 113, and adjusts the level of the distortion signal of the light emitting section and the level of the distortion signal from the distributer to be the same so as to cancel the distortion signals with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device with a distortion compensation function, and more particularly to a distortion compensation method for an optical transmission device.

[0002]

2. Description of the Related Art A conventional optical transmission device will be described with reference to FIG.

FIG. 2 is a schematic diagram showing the configuration of a conventional optical transmission device having a composite distortion compensation function in multichannel high frequency analog transmission.

In FIG. 2, 201 is a distributor, 202 is a distortion generator, 203 is a first delay circuit, 204 is a first coupler, 205 is a light emitting element for transmission, 206 is a light emitting element, and 2 is a light emitting element.
Reference numeral 07 is a photodiode, 208 is an amplifier, 209 is a second delay circuit, and 210 is a second coupler.

The distributor 2 having distribution terminals in three directions
01, a distortion generating section 202 connected to the bidirectional distribution terminals, a first coupler 204 connected to the output terminal of the distortion generating section 202, and a first coupler 204 The transmission light emitting element 205 is connected in series.

For this series connection circuit, the distributor 2
01 remaining unidirectional distribution terminal and the first coupler 20.
A first delay circuit 203 is connected in parallel between the four.

The distortion generating section 202 has a light emitting element 206 at a unidirectional distribution terminal among the bidirectional distribution terminals to be inputted.
, The photodiode 207, and the amplifier 208 are connected in series, and this series connection circuit serves as an input of the second coupler 210.

The distribution terminal in the other direction and the second coupler 21.
A second delay circuit 209 is connected in series between 0s.

The operation of the optical transmission device having the above configuration will be described.

The signals distributed in three directions by the distributor 201 are S ₁ , S ₂ , and S ₃ .

The signals S ₁ and S ₂ are input to the distortion generator 202. The signal S ₁ is converted into an optical signal by the light emitting element 206. The light emitting element 206 is the transmitting light emitting element 20.
Since the light emitting element having the same distortion characteristic as that of No. 5 is selected, the optical signal converted by the light emitting element 206 causes the same composite distortion as that of the transmitting light emitting element 205.

The optical signal is input to the photodiode 207, becomes an electrical signal, and is input to the amplifier 208. The amplifier 208 regulates the electrical signal to the same level as the signal S ₂ . The adjusted electrical signal is transferred to the second combiner 2
It becomes one input of 10.

The signal S ₂ is set by the second delay circuit 209 so as to be 180 degrees out of phase with the adjusted electrical signal and serves as another input to the second coupler 210. A second combiner 210 for combining the two input signals
Outputs only the composite distortion due to the light emitting element 206.
This composite distortion output signal is input to the first combiner 204.

The signal S ₃ from the distributor 201 is 180 degrees out of phase with the output of the second coupler 210, that is, the composite distortion output signal from the light emitting element 206, by the first delay circuit 203. Is adjusted.

Since the light-emitting element 205 and the light-emitting element 206 have the same distortion characteristics as described above, the coupler 204 outputs a signal including the complex distortion that may be generated in the light-emitting element 5, and the light-emitting element 205. To drive.

The output optical signal from the output light emitting element 205 driven by the output signal including the composite distortion as described above can be a small distortion that cancels the composite distortion generated in the light emitting element 205. .

[0017]

In the above-mentioned conventional optical transmission device with distortion compensation function, the transmitting light emitting element 205 and the light emitting element 2 are used.
06 is required to have the same distortion characteristics, and when one light emitting element is damaged, a light emitting element having the same distortion characteristics as the light emitting element must be prepared.

If the preparation is not possible, both the transmitting light emitting element 205 and the light emitting element 206 must be replaced. This is very costly and requires re-adjustment based on the difference in the characteristics of the light emitting element, which is a troublesome problem.

The present invention has been made in order to solve the problems of the prior art, and uses a pair of light emitting elements that do not have the same distortion characteristics and compensates the generated distortion by optical transmission with a distortion compensation function. The purpose is to provide a device.

[0020]

In order to achieve the above object, an optical transmitter with a distortion compensation function for transmitting multi-channel high frequency analog signals has a configuration in which multiple high frequency analog signals are transmitted. , A first distortion generator for generating a composite distortion signal from the distribution signal to the first path, and a phase of the composite distortion signal by a first delay circuit. A first path portion having a first distributor for delaying and distributing to the second path and a first level adjuster to which a composite distortion signal from the first distributor is input; A second distortion generator for generating a composite distortion signal from a distribution signal to the path portion, a second level adjuster to which the composite distortion signal is input, a composite distortion signal from the second level adjuster, and the first Complex distortion from distributor through first delay circuit And a third level adjuster to which a composite distortion signal of the first combiner is input, and a third path part. A third path portion including a second delay circuit that adjusts a distribution signal to the second path portion so that the output of the first path portion and the output of the second path portion are 180 degrees out of phase with each other; First, second,
An output multiplexer for multiplexing the output of the third path portion, and a light emitting portion for converting the output of the output multiplexer into an optical signal,
The first level adjuster, in the composite distortion signal generated in the light emitting unit, any order, in the composite distortion signal from the first distributor, to adjust the same order to the same level, the The second level adjuster adjusts the order adjusted by the first level adjuster and a composite distortion signal from the second distortion generating unit to the same level, and the third level. The adjuster is the same as the unadjusted order in the first level adjuster in the composite distortion signal of the light emitting unit, and the order in the composite distortion signal of the light emitting unit and the first multiplexer. It is characterized in that the order is adjusted to the same level as the order in the complex distortion signal.

In the optical transmission device with a distortion compensation function described in the preceding paragraph, each of the first distortion generating section and the second distortion generating section has a re-distributor for re-distributing an input into two signals, and the re-distributor. An electrically non-linear element for generating a multi-order composite distortion signal from the generated one signal, and an amplifier for adjusting the redistributed other one signal to the same level as the multi-order composite distortion signal,
A delay circuit that is connected in series with the amplifier and shifts its output signal by a phase different from that of the composite distortion signal by 180 degrees; and a multiplexer that multiplexes the output signal of the electrical nonlinear element and the output signal of the delay circuit. It is characterized by consisting of.

[0022]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to FIG.

[First Embodiment] FIG. 1 is a schematic configuration diagram of an optical transmission device having a composite distortion compensation function in multichannel high frequency analog transmission according to an embodiment of the present invention.

In FIG. 1, 101 is an input distributor and 10
2 is a first path part, 103 is a second path part, 104 is a third path part, 105 is a first distortion generator, 106, 122
Are redistributors, 107 and 115 are non-linear elements, and 108 and 1
23 is an attenuator, 109 and 124 are delay circuits, 110 and 1
25 is a multiplexer, 111 is a first distributor, 112 is a first level adjuster, 113 is a light emitting element for transmission, 114 is a second distortion generator, 116 is a second level adjuster, 117 is A first delay circuit, 118 is a first multiplexer, 119 is a third level adjuster, 120 is a second delay circuit, and 121 is an output multiplexer. A transmission device is configured.

First, the distortion compensation method used in the present invention will be described.

A laser diode is used as a light emitting element for transmission of an optical transmission device for transmitting high frequency signals of multiple channels. When this laser diode is intensity-modulated by a multi-channel high frequency signal, a complex distortion is generated due to the nonlinearity of the laser diode. 2 in this composite distortion
Since the second- and third-order distortion components are larger than the other orders, methods for reducing these distortion components are being studied.

At an input level that does not cause clipping of the laser diode, the second-order composite distortion and the third-order composite distortion characteristics that occur when the laser diode is modulated by a multi-channel high-frequency analog signal are respectively expressed by the following equation ( It is represented by 1) and (2).

[0028]

[Equation 1]

[0029]

[Equation 2]

In the above equation, K ₂ is a second-order distortion coefficient indicating the second-order nonlinearity of the laser diode, K ₃ is a third-order distortion coefficient indicating the third-order nonlinearity of the laser diode, and μ is m · N ^1/2 . Yes, m is the degree of optical modulation per channel, and N is the number of transmission channels.

Since the optical modulation degree per channel is proportional to the input power of the laser diode, the second-order composite distortion is proportional to the input power, and the third-order composite distortion is proportional to the square of the input power. The non-linear element of the electric signal system is proportional to the input power like the laser diode. Therefore, it is possible to generate the same second-order complex distortion signal and third-order complex distortion signal generated by the nonlinearity of the laser diode by using the nonlinear element of the electric signal system. The present invention compensates for distortion of a laser diode, which is a light emitting element for transmission of an optical transmission device, by using the second-order composite distortion and third-order composite distortion signals of the non-linear element of the electric signal system.

An embodiment of the present invention will be specifically described.

FIG. 1 is a schematic block diagram of an optical transmission device with a composite distortion compensation function according to an embodiment of the present invention.

The plurality of carrier waves on which the data are superimposed are distributed by the input distributor 101 in the three directions of the first path section 102, the second path section 103, and the third path section 104.

First, the second path portion 103 will be described.

The signal of the second path portion 103 is a first distortion generator 10 that generates a composite distortion from the input electric signal.
5 is input.

In the first distortion generator 105, the redistribution unit 106 re-distributes the distribution signal to the two paths.
One redistribution signal is input to the non-linear element 107, for example, a diode. The output of the non-linear element 107 becomes one input of the multiplexer 110.

The other redistributed signal is attenuated by the attenuator 108 so as to be at the same level as the signal passed through the nonlinear element 107, and further adjusted by the delay circuit 109 so that the phase is shifted by 180 degrees. . This adjusted output becomes the other input of the multiplexer 110.

After that, when the two outputs are combined by the combiner 110, the plurality of carrier waves on which the data are superimposed cancel each other out except the composite distortion signal, and become only the composite distortion signal.

The output signal of the composite distortion signal of the multiplexer 110 is divided into two directions by the first divider 111.
One of the output signals is directly transmitted to the first level adjuster 112 in the second path unit 103. The other output is shifted to the third path unit 104 by the first delay circuit so that the phase is different by 180 degrees, distributed, and transmitted.

In the first level adjuster 112, the secondary complex distortion or 3 caused by the transmitting light emitting element 113 is generated.
Adjust to the same level as any one of the following complex distortion components.

Next, the third path portion 104 will be described.

The third path portion 104 is also the second path portion 103.
Similarly, the second distortion generator 114 is configured to generate only a composite distortion signal.

Nonlinear element 1 of the second distortion generator 114
No. 15 does not have to have the same distortion characteristics as the non-linear element 107 used in the first distortion generator 105.

The first distributor 1 of the second path portion 103
Among the distortion signals distributed from 11 by the first delay circuit so that the phases are different by 180 degrees, the second-order composite distortion or the third-order composite distortion whose level is adjusted by the first level adjuster 112. And the same-order composite distortion signal generated by the second distortion generator 114 are adjusted to the same level by the second level adjuster 116.

The signal distributed and transmitted from the first distributor 111 is 180 degrees out of phase with the distorted signal output from the second level adjuster 116 by the first delay circuit 117.

When the distributed and transmitted composite distortion signal of the first distributor 111 and the output signal of the first level adjuster 116 are combined by the first combiner 118, the first level adjuster 112. Either the second-order composite distortion or the third-order composite distortion component whose level is adjusted in 1 is canceled out, and only the distortion signal of the order whose level is not adjusted remains.

After that, the level of either the second-order composite distortion component or the third-order composite distortion component whose level is not adjusted by the first level adjuster 112 and the homogeneity generated in the transmitting light emitting element 113. The level of the distortion signal output from the first multiplexer 118 is adjusted by the second level adjuster 116 so as to make up for the difference with the level of the complex distortion component of.

The plurality of carrier waves on which the data distributed in the three directions by the input distributor 101 are superimposed are the distortion signal from the first level adjuster 112 of the second path unit 103 and the third path unit. The distortion signal from the third level adjuster 119 of 104 and the second delay circuit 1 of the first path unit 102.
A signal whose phase is shifted by 180 degrees by 20 is multiplexed by the output multiplexer 121. The combined signal includes a signal that cancels the second-order composite distortion component and the third-order composite distortion component that would be generated by the transmitting light emitting element 113. Therefore, when the transmission light emitting element 113 is driven by using the multiplexed signal, the output optical signal has the second-order composite distortion component and the third-order composite distortion component removed.

[0050]

As described above in detail, according to the configuration of the present invention, it is possible to provide an optical transmission device that uses a pair of light emitting elements that do not have the same distortion characteristics and that compensates the generated complex distortion. it can.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical transmission device with a composite distortion compensation function in multi-channel high frequency analog transmission according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an optical transmission device having a composite distortion compensation function in conventional multi-channel high frequency analog transmission.

[Explanation of symbols]

 101 Input distributor 102 1st path part 103 2nd path part 104 3rd path part 105 1st distortion generator 106,122 Redistributor 107,115 Non-linear element 108,123 Attenuator 109,124 Delay circuit 110, 125 Multiplexer 111 First distributor 112 First level adjuster 113 Transmitting light emitting element 114 Second distortion generator 116 Second level adjuster 117 First delay circuit 118 First combiner Device 119 Third level adjuster 120 Second delay circuit 121 Output multiplexer 201 Distributor 202 Distortion generator 203 First delay circuit 204 First coupler 205 Transmission light emitting element 206 Light emitting element 207 Photo diode 208 Amplifier 209 Second delay circuit 210 Second coupler

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04B 10/26 10/14 10/04 10/06

Claims (2)

[Claims] 1. An input distributor for distributing a signal of a multiplexed high frequency analog signal to first, second and third path parts, and a first for generating a composite distortion signal from the signal distributed to the first path part. And a first distributor for inputting the composite distortion signal from the first distributor, which delays the phase of the composite distortion signal by 180 degrees by the first delay circuit and distributes it to the second path. A first path section having a level adjuster, a second distortion generating section for generating a composite distortion signal from a distribution signal to the second path section, and a second level input by the composite distortion signal. A first combiner for combining the composite distortion signal from the adjuster and the second level adjuster with the composite distortion signal from the first distributor via the first delay circuit, and the first combiner. A second path portion having a third level adjuster to which the composite distortion signal of the wave device is input, and A third delay circuit that adjusts a distribution signal to the third path portion so that the output of the first path portion and the output of the second path portion are 180 degrees out of phase with each other. A path section, an output multiplexer that multiplexes the outputs of the first, second, and third path sections, and a light emitting section that converts the output of the output multiplexer into an optical signal, The first level adjuster adjusts one of the orders in the composite distortion signal generated in the light emitting unit and the same order in the composite distortion signal from the first distributor to the same level, The second level adjuster adjusts the order adjusted by the first level adjuster and the same order in the composite distortion signal from the second distortion generator to the same level, and the third level adjuster. The unit has the same order as the unadjusted order of the first level adjuster in the composite distortion signal of the light emitting unit, and Distortion compensating function with optical transmission apparatus characterized by being configured to adjust a degree in the composite distortion signal from the the degree in distorted signals first multiplexer to the same level. 2. The optical transmission device with distortion compensation function according to claim 1, wherein each of the first distortion generating section and the second distortion generating section comprises a re-distributor for redistributing an input into two signals. An electrically non-linear element for generating a multi-order composite distortion signal from the redistributed one signal, and an amplifier for adjusting the other redistributed signal to the same level as the multi-order composite distortion signal And a delay circuit that is connected in series with the amplifier and shifts its output signal to a phase different from the composite distortion signal by 180 degrees, and a multiplexing circuit that multiplexes the output signal of the electrical nonlinear element and the output signal of the delay circuit. An optical transmission device with a distortion compensation function, which comprises: