JP2001244883A - Optical transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission device which can reduce distortion components generated by a transmission system and a reception-side main amplifier. SOLUTION: On a transmission side, a distributing means 1 divides an object signal to be sent into a main signal and a subordinate signal and transmitting means 2 to 4 send the main and subordinate signals as light signals to a reception side through an optical transmission line F3. On the reception side, electric converting means 11, 12, and 15 convert the main signal and subordinate signal received from the transmission side into electric signals and a main amplifier 13 amplifies the main signal; and a distortion component acquiring means 16 puts together part of the amplified signals outputted from the main amplifier 13 and the subordinate signal together to obtain the distortion component of the amplified signal and a distortion component reducing means 17 puts together the rest of the amplified signals from the main amplifier and the obtained distortion component to reduce a distortion component included in the rest of the amplified signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission apparatus for transmitting an optical signal from a transmission side to a reception side via an optical transmission line, and more particularly to a distortion component generated in a transmission system and a main amplifier on a reception side. The present invention relates to an optical transmission device capable of reducing a distortion component generated.

[0002]

2. Description of the Related Art In recent years, a technique for transmitting a high-frequency signal using, for example, an optical fiber has been generalized, and an example of an optical analog transmission system using such a technique is shown in FIG. In the optical analog transmission system shown in FIG.
The electrical / optical converter 51 generates an optical signal that is analog-modulated with a high-frequency signal to be transmitted, and transmits the optical signal through an optical transmission medium 52 made of an optical fiber.
3 demodulates the transmitted optical signal into the original high-frequency signal and outputs it.

When an optical signal is transmitted using an optical fiber as described above, the signal can be transmitted by utilizing the excellent characteristics of the optical fiber, such as low loss, light weight, and small diameter. For this reason, a transmission method using an optical fiber is more suitable than a conventional transmission method using a metal wire, particularly when transmitting a signal of a high frequency or transmitting over a long distance.

[0004] In general, as an optical modulation system,
An optical intensity modulation method for modulating the intensity of an optical signal with a high-frequency signal is used. Although it has not been widely used,
As another optical modulation method, for example, an optical frequency modulation method for modulating the light emission frequency of an optical signal is also known.

The advantages of the above-mentioned light intensity modulation method are as follows.
It is easy to convert a high-frequency signal into an optical signal. Specifically, for example, when a semiconductor laser is used as a light emitting device, the intensity of an optical signal can be modulated (direct modulation) by directly modulating the driving current of the semiconductor laser with a high-frequency signal. It is. When a signal in which a plurality of signals are multiplexed by a frequency multiplexing method, a code multiplexing method, a time division multiplexing method, or the like is used as a high-frequency signal, the multiplexed signal can be collectively transmitted as an optical signal. It is possible to reproduce the multiplexed signal after transmission.

As an application field of optical analog transmission which can transmit a high frequency signal with a relatively simple configuration as described above, for example, a device for transmitting a plurality of video signals in a cable television (CATV), For example, there is an apparatus that relays a wireless signal communicated in mobile communication.

[0007] When transmitting an analog-modulated optical signal as described above, it is important to improve the transmission quality in the optical transmission system. In particular,
Since transmission quality in an optical transmission system is degraded by noise and distortion generated in the optical transmission system, it is necessary to reduce such noise and distortion.

Here, the noise generated in the optical transmission system includes, for example, a noise generated by a light emitting device such as a laser and a noise generated by a light receiving device. In addition, as distortion generated in the optical transmission system, for example, there is an odd-order distortion signal.
When an analog signal to be transmitted has a certain finite band and no other band, an odd-order distortion signal is generated at a position near the band of the analog signal.

Specifically, for example, in mobile communication of a portable telephone system, several tens of MHz around 800 MHz
When a communication signal having a bandwidth of? Is transmitted, a third-order distortion signal generated in the vicinity of the communication signal to be transmitted is generated in the bandwidth, so the third-order distortion signal is removed by a frequency filter. It is not easy to do. In addition,
When transmitting the communication signal as described above, a direct current (0H
z) Near or 1600 (ie twice 800 MHz)
Although a secondary distortion signal is generated in the MHz band, the secondary distortion signal is far away from the 800 MHz band to be transmitted, and thus can be easily removed by a frequency filter.

As described above, in the optical transmission system, it is necessary to reduce the amount of odd-order distortion, particularly the third-order distortion, in order to improve transmission quality. Considering the above-mentioned noise, the dynamic range of the optical transmission system is
For example, it can be said that it is limited by the amount of noise generated in the optical transmission system and the amount of distortion generated in the optical transmission system.

Here, the relationship between the degree of optical modulation in the case where an analog signal is generated in an optical transmission system and the amount of noise or distortion generated in the optical transmission system will be described. First,
The absolute value of the amount of noise generated in the optical transmission system depends on devices such as a light-emitting device such as a laser, a light-receiving device, and an optical fiber, but is almost independent of the degree of light modulation. For this reason, the ratio of the signal P1 to be transmitted to the generated noise P2 (CNR = P1 / P2) increases as the optical modulation degree increases, and the noise characteristics are reduced.

On the other hand, the amount of distortion generated in the optical transmission system increases as the degree of optical modulation increases. For this reason, the smaller the light modulation degree is, the smaller the generated distortion is, which results in low distortion characteristics. As described above, the transmission quality in the optical transmission system changes depending on the degree of optical modulation, and the degree of optical modulation can be set by balancing the amount of noise and the amount of distortion generated in the optical transmission system. Will be Assuming that the degree of light modulation is fixedly set, the dynamic range of the optical transmission system depends on a light-emitting device such as a laser, a light-receiving device, an optical transmission loss, and the like.

By the way, the transmitter / receiver of a base station device used in mobile communication such as a portable telephone system is composed of, for example, a modulation / demodulation device for modulating a radio signal, a power amplifying device for amplifying the signal, and the like. . Here, since a radio signal of a plurality of frequencies is usually transmitted by one base station apparatus, the plurality (that is, the number of frequencies) is provided as a modem.

On the other hand, with respect to the power amplifying device, conventionally, a plurality of (ie, the number of frequencies) amplifying devices are provided corresponding to each frequency, and outputs from all these amplifying devices are combined and transmitted. However, in recent years, it is common practice to provide a common amplifying device that collectively amplifies signals of a plurality of frequencies and perform common amplification.

In such a common amplification method, since signals of a plurality of frequencies are collectively amplified, intermodulation distortion such as the above-described third-order distortion occurs, and the distortion signal becomes an unnecessary signal for transmission. I will. Such an unnecessary signal can be reduced by using, for example, a low-distortion amplifier, but generally, a low-distortion amplifier is an amplifier that outputs a large amount of power, and the power consumption and the amount of heat are large. Therefore, it is not economical and not preferable.

For this reason, it is possible to realize low-distortion amplification without increasing the output as low as a low-distortion amplifier.
A configuration is employed. As the distortion compensation method, there are various methods such as a negative feedback method, an envelope feedback method, a heterodyne feedback method, a predistortion method, a Cuban predistortion method, and a feedforward method. There is an effect with.

Here, among the various distortion compensation methods described above, the feed-forward method has a very good characteristic of improving the amount of distortion. The mainstream is to reduce distortion by the feedforward method.

FIG. 7 shows an example of an amplifying device for performing distortion compensation by a feedforward method, and shows a specific example of signal processing performed by the amplifying device. As shown in the figure, an amplifier for performing distortion compensation by a feedforward method includes a main amplifier 62 and an auxiliary amplifier 64.
Are provided as amplifiers.

First, a signal to be amplified is split by a splitter 61, one split signal [E (t)] is input to a main amplifier 62, and the other split signal [E (t)] is an auxiliary amplifier 64. Is input to Note that t indicates time, for example, “E (t)” indicates that “E” is a function of time t, and the same applies to “(t)” below. Here, the symbols in “[]” attached to each signal indicate the level of each signal.

In the main amplifier 62, the input signal [E (t)] is amplified by the amplification factor A1, and the amplified fundamental signal [A1 ·
E (t)] and the resulting distortion signal [IM (t)] are output from the main amplifier 62 as a signal [A1 · E (t) + IM (t)]. The signal output from the main amplifier 62 is split by the splitter 63 at a predetermined split ratio (D1: D2), and one of the split signals [D1 ｛A1 ・ E] is output.
(T) + IM (t)}] is input to the combiner 65, and the other branch signal [D2 {A1E (t) + IM (t)}]
Is input to the auxiliary amplifier 64.

Here, it is assumed that D1> D2, and the branching unit 6
It is assumed that the level of the signal input from 3 to the auxiliary amplifier 64 is sufficiently lower than the level of the signal input to the synthesizer 65. In the auxiliary amplifier 64, first, at the input unit, a difference signal [D2 · ΔA1 · E] between the signal input from the splitter 63 and the signal input from the splitter 61.
(T) + IM (t)｝ − E (t) = (D2 · A1-1)
E (t) + D2IM (t)}] is obtained.

Here, for example, (D2 · A1-
1) The level of the signal input to the auxiliary amplifier 64 is adjusted by adjusting the branching ratio (D1: D2) so that = 0, or by using an attenuator (attenuator), an amplifier, or the like. Thus, at the input of the auxiliary amplifier 64, the distortion signal [D2 · IM
(T)] only.

Then, in the auxiliary amplifier 64, the distortion signal obtained at the input section is amplified by the amplification factor A2, and the amplified signal [A2 · D2 · IM (t)] is input to the combiner 65. Note that, as described above, the branch amplifier 63 outputs the auxiliary amplifier 6
Since the level of the signal input to 4 is sufficiently small, the amount of distortion generated in the auxiliary amplifier 64 is very small and can be ignored.

In the combiner 65, the signal input from the splitter 63 and the signal input from the auxiliary amplifier 64 are combined with a predetermined combining ratio (C1: C2), and the combined signal [C1, D1,.・ E (t) + IM (t)｝ + C2
· A2 · D2 · IM (t) = C1 · D1 · A1 · E
(T) + (C1 · D1 + C2 · A2 · D2) · IM
(T)] is output.

Here, for example, the above (C1.D1 + C
2 · A2 · D2) = 0 so that the branching ratio (D1: D
2), the composition ratio (C1: C2), and the amplification degree A2 of the auxiliary amplifier
Is adjusted, the distortion signal included in the signal output from the combiner 65 is reduced.

Next, the distortion signal generated in the optical transmission system will be described in detail. The distortion signal is generated due to the nonlinearity when the high-frequency signal Ei is input to a nonlinear device such as a semiconductor laser having nonlinear input / output characteristics, and the signal E output from the nonlinear device is output.
o can be represented by a series that takes the sum of a linear signal term and a non-linear signal term in the input signal Ei.

Here, an example of the signal Ei input to the nonlinear device is shown in Expression 1, and an example of the signal Eo output from the nonlinear device in this case is shown in Expression 2. In addition,
Ai indicates the amplitude, ki indicates the wave number of the signal, t indicates time, and a1, a2, a3,... Indicate unique coefficient values determined based on the input / output characteristics of the nonlinear device.

[0028]

(Equation 1)

[0029]

(Equation 2)

Further, in this case, assuming that, for example, signals of two frequencies (E1 + E2 = Ei) are input as the input signal Ei, the output signal Eo is expressed by Expression 3. Also,
By substituting Equation 1 into the right side of Equation 3, Equation 4 is obtained.

[0031]

(Equation 3)

[0032]

(Equation 4)

Here, on the right side of Equation 3 and the right side of Equation 4, for example, one item and two items of signals represent fundamental wave signals, three to five items of signals represent secondary distortion signals,
Signals from six to nine items indicate third-order distortion signals.
Among the generated distortion signals, the distortion signals generated near the fundamental signal are signals of seven items and eight items. In particular,
For example, when two signals, a signal of frequency f1 and a signal of frequency f2, are input to the nonlinear device as fundamental signals, the frequency (2 · f2−f1) and the frequency (2 · f1)
A third-order distortion signal is generated at the frequency position of -f2).

As shown in the above equations (3) and (4), for example, when the level of an input signal is increased, the third-order distortion signal increases at a rate three times the rate of the input signal.
As a method of improving the distortion characteristics of the nonlinear device by reducing such a third-order distortion signal, for example, there is a method of reducing a3 / a1, which is equivalent to improving the distortion characteristics of the nonlinear device itself. . As another method, for example, the intensity (level) of the input signal A1, A
There is a way to make 2 smaller.

Next, as an example of an optical transmission device that performs distortion compensation by a feedforward method, Japanese Patent Laid-Open No. 7-245 is disclosed.
The feedforward optical transmission device described in Japanese Patent Application Publication No. 599 (hereinafter, referred to as Document 1) will be briefly described. That is, on the transmission side of the feedforward optical transmission device,
An electric signal to be transmitted is distributed, and one of the distributed signals is amplified by an amplifier (hereinafter, referred to as an amplifier P) to obtain an amplified signal including a distortion signal generated in the amplifier P. Further, only the distortion signal generated in the amplifier P is obtained by subtracting the amplified signal and the other distribution signal. Then, the obtained two signals are transmitted to the receiving side as optical signals.

On the other hand, the receiving side of the feedforward optical transmission apparatus subtracts two signals received from the transmitting side to reduce a distortion signal included in the amplified signal. With the above operation, in the feedforward optical transmission device, it is possible to reduce the distortion signal generated in the amplifier P provided on the transmission side on the reception side.

[0037]

However, in a conventional optical transmission apparatus, for example, when a signal transmitted from a transmission side to a reception side is amplified by a reception side amplifier, a distortion component generated in the amplifier is reduced. Nothing suitable,
Further, for example, there is a problem that there is no one suitable for reducing a distortion component generated in a transmission system. In the feedforward optical transmission device described in the above document 1, although the distortion component generated in the amplifier P on the transmission side can be reduced, the distortion component generated in the amplifier on the reception side and the distortion component generated in the transmission system can be reduced. It was insufficient to reduce the distortion component generated.

The present invention has been made to solve such a conventional problem. When an optical signal is transmitted from a transmission side to a reception side via an optical transmission line, distortion generated in an amplifier on the reception side is generated. It is an object of the present invention to provide an optical transmission device capable of reducing components and also reducing a distortion component generated in a transmission system.

[0039]

In order to achieve the above object, an optical transmission apparatus according to the present invention transmits an optical signal from a transmitting side to a receiving side via an optical transmission path as follows. The distortion component generated in the signal is reduced. That is, on the transmitting side, the distribution unit divides the signal to be transmitted into a main signal and an auxiliary signal, and the transmission unit receives the distributed main signal and the distributed auxiliary signal as optical signals via the optical transmission path. Send to the side. On the receiving side, the electric conversion means converts the main signal and the auxiliary signal received as optical signals from the transmitting side via the optical transmission line into electric signals, respectively, and the main amplifier amplifies the main signal converted into the electric signal. And
The distortion component acquisition unit combines a part of the amplified signal output from the main amplifier and the auxiliary signal converted into an electric signal to obtain a distortion component of the amplified signal, and the distortion component reduction unit outputs the distortion component from the main amplifier. The other part of the amplified signal and the distortion component obtained by the distortion component obtaining means are combined to reduce the distortion component included in the other part of the amplified signal.

Therefore, since the distortion component is reduced on the receiving side by using the main signal and the auxiliary signal distributed on the transmitting side as described above, for example, an amplifier on the receiving side (main amplifier according to the present invention) Can reduce the distortion component generated in the above. Further, as a preferred embodiment, for example, when the transmission side performs distribution such that the distortion component generated in the auxiliary signal is smaller than the distortion component generated in the main signal in the transmission system,
The distortion component generated in the transmission system may be sufficiently reduced on the receiving side.

In the optical transmission device according to the present invention, in the above-described configuration, the distortion component generated in the signal is reduced as follows. That is, on the transmitting side, the predetermined signal combining means combines a predetermined signal with a signal to be transmitted. Then, on the receiving side, the filter unit extracts the distortion component of the predetermined signal from the signal whose distortion component has been reduced by the distortion component reduction unit, and the adjustment unit extracts a small distortion component of the predetermined signal. As described above, at least one of the parameters of the amplitude and the phase of the signal synthesized by the distortion component acquiring unit is adjusted.

Therefore, even when the magnitude of the signal transmission loss or the magnitude of the phase change of the signal differs depending on the length of the optical transmission path, for example, the signal is combined with the signal to be transmitted. Based on the distortion component generated in the predetermined signal, the distortion component generated in the main amplifier on the receiving side and the distortion component generated in the transmission system can be reduced.

In a preferred embodiment, for example, when the frequency of the predetermined signal is located near the frequency of the signal to be transmitted, a distortion component generated in the predetermined signal and a distortion component generated in the signal to be transmitted are reduced. Are the same (or almost the same), so that the effect of reducing the distortion component may be largely obtained.

Further, in the optical transmission device according to the present invention, in the above configuration, the distortion component generated in the signal is reduced as follows. That is, the adjusting means provided on the receiving side has a vibrating means for vibrating the parameter to be adjusted, and the distortion component is changed based on a change in the distortion component of the predetermined signal caused by the vibration. Adjust to the minimum parameter.

Therefore, for example, even in the case where the state of the amplifier or the state of the transmission system fluctuates, based on the change in the distortion component of the predetermined signal caused by the oscillation of the above-described parameters, the main signal on the receiving side is obtained. The distortion component generated in the amplifier and the distortion component generated in the transmission system can be reduced to the minimum value.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical transmission device according to a first embodiment of the present invention will be described with reference to FIG. The optical transmission device according to the present invention is applicable to, for example, a device in which a high-frequency signal is transmitted as an optical signal from a transmission side to a reception side, and the reception side amplifies power of the high-frequency signal. In particular,
For example, a high-frequency signal such as a radio signal in mobile communication such as a mobile phone system is transmitted as an optical signal from a transmitting side to a receiving side by an optical fiber for several hundred meters to several kilometers, and the receiving side power-amplifies and outputs the high-frequency signal. It is applicable to such a base station apparatus and the like.

FIG. 1 shows an example of the configuration of the optical transmission apparatus according to the present embodiment.
, Main electric / optical converter 2, auxiliary electric / optical converter 3, optical fiber F1, optical fiber F2, and wavelength division type optical coupler (WD
An M coupler 4 is provided, and a wavelength division type optical coupler 11, an optical fiber F4, an optical fiber F5, a main optical / electrical converter 12, a main amplifier 13, a splitter 14, an auxiliary optical / electrical A converter 15, an auxiliary amplifier 16, and a combiner 17 are provided. Also, the wavelength division type optical coupler 4 on the transmitting side
The wavelength division type optical coupler 11 on the receiving side is connected via an optical fiber F3 which is an optical transmission line.

First, a configuration example and an operation example of the transmitting side will be described. The splitter 1 receives, for example, a signal to be transmitted (in this example, a high-frequency analog electric signal) from the outside, splits (divides) the input signal into two signals, and outputs one of the split signals (hereinafter, referred to as a split signal). , Main signal) to the main electric / optical converter 2 and the other branch signal (hereinafter, referred to as an auxiliary signal) to the auxiliary electric / optical converter 3.

The main electric / optical converter 2 is composed of, for example, a semiconductor laser or the like which emits an optical signal whose optical intensity is modulated by an input signal. , And a main optical signal), and outputs the main optical signal to the wavelength division optical coupler 4 via the optical fiber F1.

The auxiliary electric / optical converter 3 is composed of, for example, a semiconductor laser or the like that emits an optical signal whose optical intensity is modulated by an input signal.
(Hereinafter referred to as an auxiliary optical signal) and outputs the auxiliary optical signal to the wavelength division optical coupler 4 via the optical fiber F2. In this example, different values are set as the wavelength λ1 of the main optical signal and the wavelength λ2 of the auxiliary optical signal.

Here, the branching device 1 of the present embodiment performs branching so that the level of the main signal is relatively high and the level of the auxiliary signal is relatively low. When such branching is performed, low noise characteristics are realized in which the influence of noise is relatively small for the main signal but the distortion generated is relatively large, while the influence of noise is relatively large for the auxiliary signal. The low distortion characteristic that the distortion to be generated is relatively small is realized. Note that this is, for example, as described in the above-mentioned conventional example, in the main electric / optical converter 2 and the auxiliary electric / optical converter 3.
Usually, the higher the level of the input signal, the higher the degree of light modulation.

The wavelength division type optical coupler 4 combines the main optical signal input from the main electric / optical converter 2 and the auxiliary optical signal input from the auxiliary electric / optical converter 3 by frequency multiplexing, and synthesizes. The obtained optical signal (hereinafter, referred to as a combined optical signal) is transmitted via an optical fiber F3 to a wavelength division type optical coupler 11 on the receiving side.
It has the function of sending to

Next, a configuration example and an operation example of the receiving side will be described. The wavelength division type optical coupler 11 receives the combined optical signal transmitted from the transmission side wavelength division type optical coupler 4 via the optical fiber F3, and receives the combined optical signal with the main optical signal having the wavelength λ1 and the wavelength λ2. The auxiliary optical signal is split into an auxiliary optical signal and the split main optical signal is output to the main optical / electrical converter 12 via the optical fiber F4, while the split auxiliary optical signal is output via the optical fiber F5 to the auxiliary optical / electrical converter. 15 is provided.

As described above, in this example, the wavelength λ of the main optical signal is used.
1 and the wavelength λ2 of the auxiliary optical signal, the two different signals (that is, the main signal and the auxiliary signal) can be transmitted by using, for example, one optical fiber F3 as an optical transmission line. It is possible.

The main optical / electrical converter 12 converts the main optical signal input from the wavelength division optical coupler 11 into an electric signal (in this example, a high-frequency electric signal), and converts the electric signal to the main amplifier 13. It has a function to output. Main amplifier 13
Is composed of, for example, a power amplifier, and has a function of amplifying a signal input from the main optical / electrical converter 12 and outputting the amplified signal to the splitter 14.

Here, the amplified signal output from the main amplifier 13 to the branching unit 14 includes, for example, a signal originally intended for transmission on the transmission side (that is, a main signal branched by the branching unit 1).
And the distortion component generated in the main amplifier 13 and the influence of the optical transmission system from the transmission side to the reception side (for example, the distortion component generated in the optical transmission system) are superimposed.

The splitter 14 has a function of splitting the amplified signal input from the main amplifier 13 into two signals, outputting one branched signal to the combiner 17 and outputting the other branched signal to the auxiliary amplifier 16. Have. Auxiliary light / electric converter 15
Converts the auxiliary optical signal input from the wavelength division optical coupler 11 into an electric signal (in this example, a high-frequency electric signal),
It has a function of outputting the electric signal to the auxiliary amplifier 16.

The auxiliary amplifier 16 obtains a difference signal between the signal input from the splitter 14 and the signal input from the auxiliary optical / electrical converter 15, amplifies the difference signal, and outputs it to the combiner 17. Has a function. Here, in this example,
Auxiliary light / electrical converter 15
The result obtained by subtracting the input signal from the differential signal is used as a difference signal, but a configuration in which the difference signal is inverted in sign is also possible. The synthesizer 17 has a function of synthesizing a signal input from the splitter 14 and a signal input from the auxiliary amplifier 16 and outputting the synthesized signal to the outside, for example.

Next, a specific example of the distortion component reduction processing performed by the optical transmission device of this embodiment will be described. First, the level of the signal input to the splitter 1 on the transmission side is E1 (t), and the level of the main signal output from the splitter 1 and transmitted through the optical transmission system is B1 · E1 (t). The level of the auxiliary signal output from the splitter 1 and transmitted through the optical transmission system is B3 · E1
(T).

Note that t indicates time, for example, “E1
(T) "indicates that" E1 "is a function of time t,
The same applies to “(t)” below. Further, E1 (t) described above indicates a periodic function of the high-frequency signal in this example. Further, in this example, the amplitude level of the signal is used as the signal level, and inversion of the sign of the amplitude level means that the phase of the signal is inverted (the phase is shifted by 180 degrees).

In this case, assuming that the level of the distortion component generated in the main signal in the optical transmission system from the transmission side to the reception side is IM1 (t), the level E2 of the signal input to the main amplifier 13 on the reception side is obtained. (T) is represented by, for example, Expression 5.

[0062]

(Equation 5)

Assume that the amplification degree of the main amplifier 13 is B2, and the distortion component generated in the main amplifier 13 is IM2 (t).
, The level E3 (t) of the amplified signal output from the main amplifier 13 to the splitter 14 is expressed by Expression 6.

[0064]

(Equation 6)

Assuming that the branching ratio of the branching unit 14 is G1: G2, the level E4 (t) of the branching signal output from the branching unit 14 to the combiner 17 is expressed by the following equation (7).
4 to the auxiliary amplifier 16 at the level E of the branch signal.
5 (t) is expressed by Expression 8.

[0066]

(Equation 7)

[0067]

(Equation 8)

On the other hand, assuming that the level of the distortion component generated in the auxiliary signal in the optical transmission system from the transmitting side to the receiving side is IM3 (t), the auxiliary optical / electrical converter 15 on the receiving side sends the signal to the auxiliary amplifier 16. The level E6 (t) of the input signal is represented by, for example, Expression 9.

[0069]

(Equation 9)

Assuming that the amplification degree of the auxiliary amplifier 16 is B4, the level E7 (t) of the signal output from the auxiliary amplifier 16 to the synthesizer 17 is expressed by, for example, Expression (10).
In this example, the level of the signal input from the splitter 14 to the auxiliary amplifier 16 is set low so that the amount of distortion generated in the auxiliary amplifier 16 becomes negligible.

[0071]

(Equation 10)

Here, in this example, the coefficient of E1 (t) is zero (ie, G2 ·
B2 · B1−B3 = 0), the amplification factors B1 and B3 in the optical transmission system, the amplification factor B2 of the main amplifier 13, and the branching ratio G2 of the splitter 14 are set. And only the distortion component is obtained. Assuming that the combining ratio of the combining unit 17 is G3: G4, the level E8 of the combined signal output from the combining unit 17
(T) is represented by Expression 11.

[0073]

[Equation 11]

Here, in this example, since the low distortion characteristic is realized for the auxiliary signal as described above, the level IM3 (t) of the distortion component generated in the optical transmission system is considered to be negligibly small. In this case, the level E8 (t) of the composite signal described above is expressed by Expression 12.

[0075]

(Equation 12)

In this example, the amplification factor B2 of the main amplifier 13 and the coefficient B2 of the main amplifier 13 are set so that the coefficient of IM1 (t) and the coefficient of IM2 (t) become small (preferably zero) with respect to the right side of the above equation 12. The amplification degree B4 of the auxiliary amplifier 16 and the branching device 14
Are set, and the combining ratios G3 and G4 of the combiner 17 are set. For this reason, in the present example, the distortion component included in the composite signal E8 (t) output from the combiner 17 (that is, the signal term of the distortion component IM1 (t) generated in the optical transmission system and the signal component generated in the main amplifier 13) Distortion component IM2 (t)
Signal term) can be reduced.

As described above, in the optical transmission apparatus of this embodiment, the transmitting side branches the signal to be transmitted into a main signal having low noise characteristics and an auxiliary signal having low distortion characteristics.
The two signals are transmitted as optical signals through the optical fiber F3, and when the main signal received by the receiving side is amplified by the main amplifier 13, the signal is included in the amplified signal output from the main amplifier 13 using the auxiliary signal received by the receiving side. Thus, the distortion component generated in the main amplifier 13 and the distortion component generated in the transmission system can be reduced.

Therefore, in the optical transmission device of the present embodiment, for example, a light emitting device on the transmitting side (in this example, the main electric / optical converter 2 and the auxiliary electric / optical converter 3) and a light receiving device on the receiving side (in this example). , Chief light /
Even if the noise characteristic and the distortion characteristic inherent to the optical transmission system including the electric converter 12 and the auxiliary optical / electrical converter 15) and the transmission path (in this example, the optical fiber F3) are not improved as compared with the related art. In addition, the dynamic range of the transmission signal can be expanded as compared with the related art. Specifically, for example, when the device is configured using the same device as before, the dynamic range can be improved as compared with the conventional device, and, for example, when the same dynamic range as the conventional device is required, It is also possible to configure the device using an inexpensive device having inferior characteristics to the conventional device.

Here, on the transmitting side of the optical transmission device of this example,
The function of the splitter 1 for splitting a signal to be transmitted into a main signal and an auxiliary signal constitutes a distribution means according to the present invention. On the transmitting side of the present example, the main electric / optical converter 2, the auxiliary electric / optical converter 3, and the wavelength division type optical coupler 4 transmit the branched main signal and the branched auxiliary signal as optical signals, respectively, as optical signals. The function of transmitting to the receiving side via the path (in this example, the optical fiber F3) constitutes the transmitting means according to the present invention.

On the receiving side of the optical transmission apparatus according to the present embodiment, the wavelength division type optical coupler 11, the main optical / electrical converter 12, and the auxiliary optical / electrical converter 15 are connected from the transmitting side to the optical transmission line (in this example, The function of converting the main signal and the auxiliary signal received as optical signals via the optical fiber F3) into electric signals, respectively,
The electric conversion means according to the present invention is configured.

On the receiving side of the present embodiment, the amplifier (main amplifier) 13 for amplifying the main signal converted into the electric signal corresponds to the main amplifier according to the present invention. On the receiving side of the present example, the auxiliary amplifier 16 has a function of combining a part of the amplified signal output from the main amplifier 13 and the auxiliary signal converted into an electric signal to obtain a distortion component of the amplified signal. The distortion component acquiring means according to the present invention is constituted.

In the distortion component acquiring means of this embodiment, only the distortion component is extracted as a preferable mode. However, for example, if the distortion component can be reduced, the transmission side is not the original transmission target. The obtained signal (that is, the original signal component existing before the generation of the distortion component) may be included in the obtained distortion component.

On the receiving side of the present embodiment, the combiner 17 outputs another portion of the amplified signal output from the main amplifier 13 and the distortion component obtained by the distortion component obtaining means (the auxiliary amplifier 16 in this example). The function of reducing the distortion component included in the other part of the amplified signal by combining the above components constitutes a distortion component reduction unit according to the present invention.

In the optical transmission device of this embodiment, the splitter 14
Output to the auxiliary amplifier 16 from the
The amplitude of the signal is adjusted with respect to the signal output to the combiner 17, the signal output from the auxiliary optical / electrical converter 15 to the auxiliary amplifier 16, and the signal output from the auxiliary amplifier 16 to the synthesizer 17. Although no attenuator, amplifier, or phase shifter for adjusting the phase of the signal is provided, for example, one or both of the amplitude adjustment and the phase adjustment may be performed on all or a part of these signals.

Next, an optical transmission device according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 2 shows an example of the configuration of the optical transmission apparatus according to the present embodiment. The configuration of the optical transmission apparatus includes, for example, a pilot signal generator 21 and a combiner 22 in front of the transmission-side splitter 1. , A variable attenuator 31 is provided between the branching device 14 on the receiving side and the auxiliary amplifier 16, and the auxiliary optical / electrical converter 15 and the auxiliary amplifier 1 on the receiving side are provided.
6, a variable attenuator 32 is provided, and a branching unit 33, a filter 34, and a detection controller 3 are provided after the combiner 17 on the receiving side.
Except that the optical transmission device 5 is provided, for example, the configuration is the same as that of the optical transmission device shown in FIG. 1 of the first embodiment.

For this reason, in FIG. 2 and this example, FIG.
Each of the processing units 1 to 4 and 1 having the same functions as those shown in FIG.
1 to 17 and F1 to F5 are denoted by the same reference numerals as those shown in FIG. 1, and the processing units 1 to 4, 11 to 17 and F1 to F5 having similar functions are described in detail. Description is omitted.

In the following, components 21, 22 and 31 to 35 different from those in the first embodiment will be described in detail. In this example, it is assumed that a signal to be transmitted on the transmission side is a signal having a certain bandwidth. Specifically, for example, when a communication signal in mobile communication such as a mobile phone system is to be transmitted. Is that the signal to be transmitted on the transmitting side is a signal having a bandwidth of several MHz to several tens MHz.

First, a configuration example and an operation example of the transmitting side will be described. The pilot signal generator 21 has a function of generating a predetermined pilot signal and outputting the pilot signal to the synthesizer 22. Here, in this example, a signal of two frequencies located near the band of the signal to be transmitted on the transmitting side is used as the pilot signal. FIG. 3 shows an example of a pilot signal composed of signals having two different frequencies f1 and f2. The horizontal axis of the graph in FIG. 3 indicates the frequency, and the vertical axis indicates the signal intensity. .

The combiner 22 receives, for example, a signal to be transmitted from the outside and outputs the signal to the pilot signal generator 2.
1 has a function of inputting a pilot signal output from 1, synthesizing these two input signals, and outputting the synthesized signal to the splitter 1. In this example, the pilot signal is combined with the signal to be transmitted on the transmitting side in this manner, and the subsequent processing units 1 to 4, 11 to 17, and F1 on the transmitting side and the receiving side are combined.
In steps F5 to F5, the synthesized signal is processed in the same manner as in the first embodiment, for example.

Next, a configuration example and an operation example of the receiving side will be described. The variable attenuator 31 receives the signal output from the branching device 14, attenuates the level of the input signal by an amount of attenuation according to control from a detection controller 35 described later, and converts the signal after the attenuation into an auxiliary amplifier. 16 is provided. The variable attenuator 32 receives the signal output from the auxiliary optical / electrical converter 15, attenuates the level of the input signal by an amount of attenuation according to the control from the detection controller 35 described later, It has a function of outputting a signal to the auxiliary amplifier 16.

The splitter 33 has a function of inputting a signal output from the synthesizer 17 and, when outputting the signal, for example, externally, splitting a part of the signal and outputting it to the filter 34. . Here, the signal output from the synthesizer 17 of the present example includes the above-described pilot signal. For example, when the distortion component is not reduced to zero, the distortion component generated by the pilot signal ( Hereinafter, the distortion component is referred to as a pilot signal distortion component).

The filter 34 is composed of, for example, a band-pass filter or the like, and has a function of extracting only the distortion component of the pilot signal from the signal input from the splitter 33 and outputting the distortion component to the detection controller 35. ing. Also,
FIG. 3 shows an example of two tertiary distortion components generated by the pilot signal shown in FIG. 3. The position where the frequency is (2 · f2−f1 = fi +) and the frequency are (2 ·
Third-order distortion components are generated at positions where f1−f2 = fi−).

The detection controller 35 controls the amount of attenuation of the two variable attenuators 31 and 32 so that the distortion component of the pilot signal input from the filter 34 is reduced (preferably minimized). It has a function of reducing the distortion component of the main signal included in the signal output from 17 (the same applies to the signal output from the splitter 33).

Here, in the distortion component reduction processing of this example,
Since the pilot signal is located near the band of the main signal (a signal to be transmitted on the transmission side), the increase or decrease of the distortion component generated by the pilot signal reflects the increase or decrease of the distortion component generated by the main signal. That is, it is assumed that the distortion component of the main signal can be reduced (eg, minimized) by reducing the distortion component of the pilot signal (eg, minimized).

As described above, in the optical transmission device of this embodiment, the magnitude of the signal transmission loss or the magnitude of the phase change of the signal is indefinite depending on, for example, the length of the optical fiber F3. However, it is possible to reduce the distortion component generated in the main amplifier 13 on the receiving side and the distortion component generated in the transmission system based on the distortion component generated in the pilot signal combined with the signal to be transmitted.

More specifically, for example, when the optical transmission apparatus of the present embodiment is actually implemented in various modes, the length of the optical transmission line is different in each mode, so that the magnitude of the signal transmission loss is large. Will be different. Further, for example, when the length of the optical transmission line is different, the magnitude of the phase change of the signal is also different. For this reason, for example, in a configuration in which the branching ratio of the branching unit 14 and the combining ratio of the combiner 17 are fixedly set as in the optical transmission device shown in FIG. It is necessary to set these values together, but it is preferable in the optical transmission device of this example that the detection controller 35 can automatically adjust the values.

Note that the processing for reducing the distortion component as in the present example does not necessarily have to be performed based on all the distortion components of the pilot signal included in the output from the splitter 33. If the range is assured, distortion component reduction processing may be performed based on, for example, a part of the distortion component of the pilot signal.

In this example, the amplitude of the signal output from the splitter 14 to the auxiliary amplifier 16 and the auxiliary optical / electrical converter 1
5 and the amplitude of the signal output to the auxiliary amplifier 16 is adjusted, but it is also possible to adopt a configuration in which, for example, only one is adjusted. In the present embodiment, the amplitude of the signal is adjusted. However, for example, the phase of the signal or both the amplitude and the phase can be adjusted.

In this example, since the signal output from the splitter 33 to the outside includes a pilot signal, for example, a band-pass filter having a characteristic of removing the pilot signal and extracting a main signal is used. Is preferably provided on the output side of the splitter 33. By providing such a filter, it is possible to prevent the pilot signal from remaining in the output signal.

Here, on the transmitting side of the optical transmission apparatus of this example,
The pilot signal described above as a reference for grasping the magnitude of the distortion component corresponds to the predetermined signal according to the present invention. In addition,
As the predetermined signal, any signal may be used as long as the distortion component can be reduced. Also, on the transmitting side in this example, the pilot signal generator 21 and the combiner 2
The function of combining a pilot signal with a signal to be transmitted constitutes a predetermined signal combining means according to the present invention.

On the receiving side of the optical transmission apparatus according to the present embodiment, the splitter 33 and the filter 34 convert the pilot signal of the pilot signal from the signal whose distortion component has been reduced by the distortion component reducing means (in this example, the combiner 17). The function of extracting the distortion component constitutes the filter means according to the present invention.

On the receiving side in this example, the detection controller 35
Controls the two variable attenuators 31 and 32 so that the amplitude of the signal synthesized by the distortion component acquisition means (the auxiliary amplifier 16 in this example) is reduced so that the distortion component of the extracted pilot signal is reduced. The function of adjusting at least one parameter with the phase constitutes the adjusting means according to the present invention. As described above, the parameters of only one of the two signals synthesized by the distortion component acquisition unit may be adjusted, or the parameters of both signals may be adjusted. Further, as described above, only one of the amplitude and the phase may be adjusted, or both may be adjusted.

Next, an optical transmission device according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 4 shows an example of the configuration of the optical transmission apparatus according to the present embodiment. The configuration of the optical transmission apparatus is, for example, the addition between a detection controller 35 on the receiving side and the respective variable attenuators 31 and 32. The adders 42 and 43 are provided, and the oscillator 4 common to the two adders 42 and 43 is provided.
For example, the configuration is the same as that of the optical transmission apparatus shown in FIG.

For this reason, in FIG. 4 and this example, FIG.
Each of the processing units 1 to 4 and 1 having the same functions as those shown in FIG.
1 to 17, 21, 22, 31 to 35, and F1 to F5 are denoted by the same reference numerals as those shown in FIG.
In addition, each of the processing units 1 to 4, 11
, 17, 21, 22, 31 to 35 and F1 to F5 will not be described in detail.

In the following, a configuration example and an operation example of the components 41 to 43 on the receiving side, which are different from those in the second embodiment, will be described in detail. In this example, the detection controller 35 controls the attenuation of each of the variable attenuators 31 and 32 by transmitting a control signal to each of the variable attenuators 31 and 32 via each of the adders 42 and 43. The variable attenuators 31 and 32 are each
The attenuation is controlled according to the magnitude of the control signal input from 2, 43.

The oscillator 41 has a function of, for example, generating an AC signal having a small amplitude and outputting the AC signal as a perturbation signal to each of the adders 42 and 43. The adder 42 receives the control signal output from the detection controller 35 to the variable attenuator 31, inputs the perturbation signal output from the oscillator 41, and adds the control signal and the perturbation signal. It has a function of outputting the result to the variable attenuator 31.

Similarly, the adder 43 inputs the control signal output from the detection controller 35 to the variable attenuator 32, and also inputs the perturbation signal output from the oscillator 41. It has a function of outputting the result of adding the perturbation signal to the variable attenuator 32.

As described above, when the attenuation of each of the variable attenuators 31 and 32 is controlled by adding the control signal and the perturbation signal, the distortion component of the pilot signal input from the filter 34 to the detection controller 35 is obtained. Changes according to the perturbation signal. Based on the change, the detection controller 35 of the present example outputs the main signal included in the signal output from the combiner 17 (the same applies to the signal output from the splitter 33). Minimize distortion components.

Here, a specific example of the distortion component reduction processing of this example will be described. In this example, the two variable attenuators 31, 3
2, the same process is performed, so one variable attenuator 31 will be described as a representative. FIG. 5 shows, for example, the magnitude of the control signal (“control amount”) input to the variable attenuator 31.
And the magnitude of the distortion component (“distortion amount”) of the pilot signal input from the filter 34 to the detection controller 35, and the horizontal axis indicated by the solid line indicates “control amount”. The vertical axis indicates the “distortion amount”. Note that such a relationship is monitored by, for example, the detection controller 35.

As shown in the figure, the above-mentioned "distortion amount" becomes minimum when the above-mentioned "control amount" becomes a certain value, and this value becomes the optimum value (optimum control value) of the "control amount". Becomes In addition, FIG. 3 shows a perturbation signal p ( 4 shows an example of the relationship between t) and a change ΔH (t) in the “distortion amount” H (t) caused by the perturbation signal p (t). Note that t indicates time.

Specifically, in the same figure, in the above two cases, the time axis is indicated by a dotted line in the same vertical axis direction as the “distortion amount”, and the magnitude of the perturbation signal p (t) with respect to time t is shown. Is shown. In this example, for example, a perturbation signal p (t) = sin (ω · t) composed of a sine function is used (ω
Is a predetermined value). In the same figure, in the above two cases, the time axis is indicated by a broken line in the same horizontal axis direction as the “control amount”, and the change ΔH of the “distortion amount” H (t) with respect to time t is shown.
The size of (t) is shown.

As shown in the figure, for example, “control amount”
Is more positive than the optimal control value (ie, greater than the optimal control value), the "distortion amount" H
(T) (= H1 (t)) indicates a change in phase with the perturbation signal p (t), and specifically, the “distortion amount” H1 (t)
Is represented, for example, by Expression 13. “Cont1” is
It shows the “distortion amount” when no perturbation signal p (t) is given.

[0113]

(Equation 13)

Although not shown, for example, when the “control amount” is shifted in the negative direction from the optimal control value (ie, smaller than the optimal control value), the “distortion amount”
H (t) (= H2 (t)) indicates a change in phase opposite to the perturbation signal p (t), and specifically, the “distortion amount” H2
(T) is represented by, for example, Expression 14. Note that "cont
"2" indicates the "distortion amount" when the perturbation signal p (t) is not given.

[0115]

[Equation 14]

Here, the “distortion amount” H shown in the above equation (13)
As a result of differentiating 1 (t) at time t, H1 ′ (t) is given by equation (15).
The result H2 ′ (t) obtained by differentiating the “distortion amount” H2 (t) shown in the above Expression 14 at the time t is shown by Expression 16.

[0117]

(Equation 15)

[0118]

(Equation 16)

The result S (t) (= S1 (t)) obtained by dividing H1 ′ (t) shown in the above equation 15 by the result p ′ (t) of differentiating the perturbation signal p (t) is The result S (t) obtained by dividing H2 ′ (t) shown in Expression 16 by the result p ′ (t) obtained by differentiating the perturbation signal p (t) shown in Expression 17
(Shown as S2 (t)) is shown in Expression 18.

[0120]

[Equation 17]

[0121]

(Equation 18)

As shown in the above equation 17, for example, when the “control amount” deviates in the positive direction from the optimal control value, the “distortion amount” increases as the perturbation signal p (t) increases. On the other hand, when the perturbation signal p (t) decreases, the “distortion amount” decreases. On the other hand, as shown in the above Expression 18, for example, when the “control amount” deviates in the negative direction from the optimal control value, the “distortion amount” decreases as the perturbation signal p (t) increases. On the other hand, when the perturbation signal p (t) decreases, the “distortion amount” increases.

When the “control amount” is the optimum control value, for example, the “control amount” is determined by the perturbation signal p (t).
The characteristic shown in the above-mentioned expression 17 and the characteristic shown in the above-mentioned expression 18 are alternately and repeatedly shown depending on whether or not is shifted in the positive direction or the negative direction. That is, when the “control amount” is the optimum control value, the temporal average value of S (t) becomes zero (= 0), and the detection controller 35
For example, based on the value of S (t), the variable attenuator 31
By adjusting the control signal for, the “control value” described above can always be adjusted to the optimal control value.

As described above, in the optical transmission apparatus of this embodiment, the distortion component of the pilot signal is constantly monitored, and the magnitude of the distortion component is always set to, for example, a predetermined value or less (in this embodiment, the minimum). Since the attenuation of each of the variable attenuators 31 and 32 is controlled, even when, for example, a change in the state of the amplifier or a change in the state of the optical transmission system occurs, the change in the state is tracked. In addition, the distortion component generated in the main amplifier 13 on the receiving side and the distortion component generated in the transmission system can always be reduced.

In this example, the above-described perturbation signal is used for both the signal output from the splitter 14 to the auxiliary amplifier 16 and the signal output from the auxiliary optical / electrical converter 15 to the auxiliary amplifier 16. Although the "control amount" is adjusted, it is also possible to adopt a configuration in which such adjustment is performed for only one of them, for example. In the present embodiment, such an adjustment is made with respect to the amplitude of the signal. However, for example, such an adjustment can be made with respect to the phase of the signal or both the amplitude and the phase.

Here, on the receiving side of the optical transmission device of this example,
The oscillator 41 and the adders 42 and 43 add a perturbation signal to the control signal output from the detection controller 35 to vibrate the amplitude of the two signals synthesized by the auxiliary amplifier 16, so that the vibration according to the present invention is obtained. Means are configured.
In this example, the amplitude of the two signals synthesized by the distortion component acquisition means (in this example, the auxiliary amplifier 16) corresponds to the parameter to be adjusted according to the present invention.

Further, as shown in the present embodiment, the adjusting means (the detection controller 35 in the present embodiment) provided on the receiving side of the present embodiment is based on the change in the distortion component of the pilot signal caused by the above-described vibration. In this way, the parameter is adjusted to a parameter that minimizes the distortion component, whereby the distortion component generated in the main amplifier and the distortion component generated in the transmission system are reduced.

As described above, the parameter of only one of the two signals synthesized by the distortion component acquiring means may be oscillated, or the parameters of both signals may be oscillated. Further, as described above, only one of the amplitude and the phase may be vibrated, or both may be vibrated.

The configuration of the optical transmission device according to the present invention is not necessarily limited to the one described above, and various configurations may be used. As an example, for example, a light emitting device or the like provided on the transmitting side, a light receiving device or the like provided on the receiving side,
Various types of optical transmission lines connecting the transmitting side and the receiving side may be used. Further, the application field of the optical transmission apparatus according to the present invention is not necessarily limited to the field relating to a base station apparatus or a relay station apparatus for mobile communication, and the present invention can be applied to apparatuses in various fields.

In various processes such as a distortion component reduction process performed by the optical transmission device according to the present invention, for example, the processor executes a control program stored in a ROM in a hardware resource including a processor and a memory. For example, each functional means for executing the processing may be configured as an independent hardware circuit. Further, the present invention can be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD-ROM in which the above-mentioned control program is stored. The processing according to the present invention can be performed by causing a processor to execute the processing.

[0131]

As described above, according to the optical transmission apparatus of the present invention, the transmission side distributes a signal to be transmitted to a main signal and an auxiliary signal, and the main signal and the auxiliary signal are respectively transmitted to the optical signal. As a transmission to the receiving side via the optical transmission line, the receiving side converts the main signal and the auxiliary signal received as optical signals from the transmitting side via the optical transmission line into electric signals, and the main signal is converted by the main amplifier. Amplify, obtain a distortion component of the amplified signal by combining a part of the amplified signal output from the main amplifier and the auxiliary signal, and obtain another part of the amplified signal output from the main amplifier and the distortion component. To reduce the distortion component included in the other part of the amplified signal, the distortion component generated in the main amplifier on the receiving side can be reduced, and the distortion component generated in the transmission system can be reduced. Enough on the receiving side It is also possible to Gensa.

Further, in the optical transmission apparatus according to the present invention, in the above-described configuration, the transmitting side combines a predetermined signal with the signal to be transmitted, and the receiving side converts the signal with the reduced distortion component into the signal. Since the distortion component of the predetermined signal is extracted and at least one parameter of the amplitude and the phase of the signal synthesized at the time of the distortion component is adjusted so that the distortion component is reduced, for example, in the optical transmission line Even if the magnitude of the signal transmission loss or the magnitude of the phase change of the signal differs, the distortion component generated in the main amplifier on the receiving side and the transmission The distortion component generated in the system can be reduced.

In the optical transmission device according to the present invention, in the above-described configuration, the parameter to be adjusted is vibrated on the receiving side, and the distortion is adjusted based on a change in the distortion component of the predetermined signal caused by the vibration. Since the parameters are adjusted to minimize the components, even if the state of the amplifier or the state of the transmission system fluctuates, for example, distortion components generated in the main amplifier on the receiving side or generated in the transmission system Can be reduced to the minimum value at all times.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a configuration example of an optical transmission device according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a pilot signal and a distortion component thereof.

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

FIG. 5 is a diagram for explaining an example of a method of adjusting to an optimum control value.

FIG. 6 is a diagram illustrating an example of an optical analog transmission system.

FIG. 7 is a diagram illustrating an example of an amplification device that performs distortion compensation by a feedforward method.

[Explanation of symbols]

1, 14, 33 · · · branching device, 2 · · · main electrical / optical converter, 3 · · auxiliary electrical / optical converter, 4, 11 · · · wavelength division type optical coupler, 12 · · · primary optical / electrical converter , 13 ...
Main amplifier, 15 Auxiliary optical / electrical converter, 16 Auxiliary amplifier, 17, 22 Synthesizer, 21 Pilot signal generator, 31, 32 Variable attenuator, 34
Filter, 35 detection controller, 41 oscillator
42, 43 ... Adder, F1 to F5 ... Optical fiber,

Claims (3)

[Claims] 1. An optical transmission device for transmitting an optical signal from a transmitting side to a receiving side via an optical transmission line, comprising: a transmitting unit that distributes a signal to be transmitted into a main signal and an auxiliary signal; Transmitting means for transmitting each of the distributed main signal and the distributed auxiliary signal as an optical signal to the receiving side via the optical transmission line, wherein the receiving side has an optical signal from the transmitting side via the optical transmission line. Electric conversion means for converting the received main signal and auxiliary signal into electric signals, a main amplifier for amplifying the main signal converted to the electric signal, and a part of the amplified signal output from the main amplifier and the electric signal. A distortion component obtaining unit that obtains a distortion component of the amplified signal by combining the converted auxiliary signal; and a distortion component obtained by the distortion component obtaining unit and another portion of the amplified signal output from the main amplifier. Synthesize and increase An optical transmission device comprising: a distortion component reducing unit configured to reduce a distortion component included in another portion of the width signal. 2. The optical transmission apparatus according to claim 1, wherein the transmitting side includes a predetermined signal combining unit that combines a predetermined signal with a signal to be transmitted, and the receiving side includes a distortion component reducing unit. Filter means for extracting the distortion component of the predetermined signal from the signal in which the distortion component has been reduced; and amplitude and phase of the signal synthesized by the distortion component acquisition means such that the extracted distortion component of the predetermined signal is reduced. And an adjusting means for adjusting at least one of the parameters: 3. The optical transmission device according to claim 2, wherein the adjustment unit includes a vibration unit that vibrates a parameter to be adjusted, and based on a change in a distortion component of the predetermined signal caused by the vibration. An optical transmission device, wherein the parameter is adjusted to a parameter that minimizes the distortion component.