JP2000236129A - Optical transmission device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission device which is simple in structure and capable of obtaining satisfactory optical transmission characteristic for controlling the center of an optical filter transmission wavelength band, when electrical signals to be transmitted are analogue signals. SOLUTION: An electro-optical conversion part 10 converts electric signals that are to be transmitted into optical signals, thorough direct intensity modulation. An optical amplification part 11 amplifies optical signals outputted from the electro-optical conversion part 10. An optical filter 13 which has a transmission wavelength band, whose center wavelength is set changeable and that is specified in a band width, removes noise components from the optical signals guided by the optical fiber 12. The photoelectric conversion part 15 converts optical signals outputted from the optical filter 13 into electrical signals. An optical filter control part 14 controls the center wavelength of the transmission wavelength band of the optical filter 13, so as to maximize the power of electrical signals outputted from the photoelectric conversion part 15. By this setup, the power of electrical signals outputted from the photoelectric conversion part 15 is measured, through which an optical transmission device simple in structure can be made satisfactory in transmission characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical transmission apparatus and method, and more particularly, to an optical transmission apparatus using an optical filter and a method of controlling a center wavelength of a transmission wavelength band of the optical filter.

[0002]

2. Description of the Related Art In an optical transmission apparatus for performing optical communication or the like, when an optical amplifier is used for long-distance transmission,
In some cases, wavelength multiplexing technology is employed for the purpose of expanding transmission capacity. In the former case, in order to remove a noise component due to spontaneous emission light of the optical amplifier from the optical signal, in the latter case, in order to extract a desired optical signal from a plurality of wavelength-multiplexed optical signals, an optical filter is provided. Required.

FIG. 6 is a block diagram showing a configuration of a conventional optical transmission device. This type of apparatus is disclosed in, for example,
No. 3,450,517. In FIG.
The conventional optical transmission device includes an electro-optical converter 100, an optical fiber 101, an optical amplifier 102, an optical filter 103, an optical filter controller 104, and an opto-electric converter 105.

[0004] The electro-optical converter 100 converts an electric signal to be transmitted into an optical signal by direct intensity modulation. The optical fiber 101 guides an output optical signal of the electro-optical converter 100.
The optical amplifier 102 amplifies the optical signal guided by the optical fiber 101. The optical filter 103 has a transmission wavelength band of a predetermined width whose center wavelength can be changed.
02 from the output optical signal. The optical filter control unit 104 controls the center wavelength of the transmission wavelength band of the optical filter 103. The photoelectric conversion unit 105 converts the output optical signal of the optical filter 103 into an electric signal.

[0005] The operation of the conventional optical transmission device will be described below. First, the electric signal to be transmitted is transmitted to the electro-optical converter 100.
Is input to The electric signal to be transmitted is an analog signal. The electro-optical converter 100 converts an input electric signal into an optical signal. The output optical signal of the electro-optical converter 100 is guided by the optical fiber 101 and input to the optical amplifier 102. The optical amplifier 102 amplifies an input optical signal. The output optical signal of the optical amplifier 102 is input to the optical filter 103. The optical signal input to the optical filter 103 includes an optical amplifier 1
02 includes a noise component due to the spontaneous emission light generated. The optical filter 103 removes this noise component from the input optical signal. Then, the output optical signal of the optical filter 103 is input to the photoelectric conversion unit 105. Photoelectric conversion unit 1
05 converts an input optical signal into an electric signal. At that time, the optical filter control unit 104 controls the center wavelength of the transmission wavelength band of the optical filter 103 (hereinafter, the center of the transmission wavelength band) so that the power of the output optical signal of the optical filter 103 is maximized. Thereby, the current value (light receiving current) of the output electric signal of the photoelectric conversion unit 105 can be maximized. Note that the power of the output optical signal of the optical filter 103 is maximized when the center of the transmission wavelength band of the optical filter 103 matches the wavelength of the output optical signal of the optical filter 103.

As described above, in the conventional optical transmission device, by controlling the center of the transmission wavelength band of the optical filter 103 so that the power of the output optical signal of the optical filter 103 is maximized, a maximum light receiving current is obtained. I have. However, the best transmission characteristics were not obtained. Because the optical filter 103
This is because when the center of the transmission wavelength band coincides with the wavelength of the output optical signal of the optical filter 103 and the electric signal to be transmitted is an analog signal, the signal-to-noise ratio of the demodulated signal generally does not become the maximum. Therefore, another conventional optical transmission device that can obtain good transmission characteristics has been proposed.

FIG. 7 is a block diagram showing the configuration of another conventional optical transmission device. This type of apparatus is described, for example, in Japanese Patent Application Laid-Open No. 6-310010. In FIG. 7, another conventional optical transmission device includes an electro-optical converter 110, an optical fiber 111, an optical amplifier 112, an optical filter 113,
An optical filter control unit 114, a photoelectric conversion unit 115, and a demodulation unit 116 are provided.

[0008] The electro-optical converter 110 converts an electric signal to be transmitted into an optical signal by direct intensity modulation. The optical fiber 111 guides an optical signal output from the electro-optical converter 110.
The optical amplifier 112 amplifies the optical signal guided by the optical fiber 111. The optical filter 113 has a transmission wavelength band of a predetermined width whose center wavelength can be changed.
The noise component is removed from the twelve output optical signals. The optical filter control unit 114 controls the center wavelength of the transmission wavelength band of the optical filter 113. The photoelectric conversion unit 115 converts an optical signal output from the optical filter 113 into an electric signal. Demodulation unit 11
6 demodulates the output electric signal of the photoelectric conversion unit 115.

The operation of another conventional optical transmission device will be described below. First, the electric signal to be transmitted is transmitted to the electro-optical converter 1.
Input to 10. The electric signal to be transmitted is an analog signal. The electro-optical converter 110 converts an input electric signal into an optical signal. The output optical signal of the electro-optical converter 110 is guided by the optical fiber 111 and input to the optical amplifier 112. The optical amplifier 112 amplifies an input optical signal. The output optical signal of the optical amplifier 112 is input to the optical filter 113. The optical signal input to the optical filter 113 includes a noise component due to spontaneous emission light generated in the optical amplifier 112. The optical filter 113 removes this noise component from the input optical signal. Then, the output optical signal of the optical filter 113 is input to the photoelectric conversion unit 115. The photoelectric conversion unit 115 converts an input optical signal into an electric signal. The output electric signal of the photoelectric conversion unit 115 is input to the demodulation unit 116. Demodulation section 116 demodulates the input electric signal. At this time, the optical filter control unit 114 controls the center of the transmission wavelength band of the optical filter 113 so that the signal-to-noise ratio of the output electric signal (demodulated signal) of the demodulation unit 116 is maximized. Thereby, when the electric signal to be transmitted is an analog signal, good transmission characteristics can be obtained. Note that the signal-to-noise ratio of the demodulated signal is maximized not when the center of the transmission wavelength band of the optical filter 113 coincides with the wavelength of the output optical signal of the optical filter 113, but when the wavelength is shifted by a certain distance. .

[0010]

As described above, in another conventional optical transmission device, when the electric signal to be transmitted is an analog signal, the optical filter 113 is designed to maximize the signal-to-noise ratio of the demodulated signal. By controlling the center of the transmission wavelength band, good transmission characteristics are obtained. However,
To perform such control, the signal level and the noise level of the demodulated signal must be measured, and the signal-to-noise ratio must be calculated from the measurement result. Therefore, another conventional optical transmission device has a problem that the configuration is complicated.

Therefore, an object of the present invention is to control the center of the transmission wavelength band of an optical filter with a simple configuration when an electric signal to be transmitted is an analog signal, thereby obtaining good transmission characteristics. An object is to provide an optical transmission device.

[0012]

A first aspect of the present invention is an optical transmission apparatus for converting an electric signal into an optical signal and transmitting the converted signal, wherein the electric signal to be transmitted is directly converted into an optical signal by intensity modulation. An electro-optical conversion section for converting the output light signal of the electro-optical conversion section into an optical amplifier, an optical fiber for guiding the output optical signal of the electro-optical conversion section, and a transmission wavelength band of a predetermined width whose center wavelength can be changed. An optical filter for removing a noise component from an optical signal guided by an optical fiber, an optical filter control unit for controlling a center wavelength of a transmission wavelength band of the optical filter, and converting an output optical signal of the optical filter into an electric signal The optical filter control unit includes an opto-electric conversion unit. When the electric signal to be transmitted is an analog signal, the power of the output electric signal of the opto-electric conversion unit is maximized by setting the center wavelength of the transmission wavelength band of the optical filter to the maximum. Like It is characterized by controlling.

In the first aspect, when the electric signal to be transmitted is an analog signal, the center of the transmission wavelength band of the optical filter is controlled so that the electric power of the electric signal output from the photoelectric converter becomes maximum. Therefore, it is sufficient to measure the power of the output electric signal of the photoelectric conversion unit, so that good transmission characteristics can be obtained with a simple configuration.

According to a second aspect of the present invention, in the first aspect, there is further provided a branching unit for branching the output electric signal of the photoelectric conversion unit into two, and the optical filter control unit converts one of the two output electric signals of the branching unit. The center wavelength of the transmission wavelength band of the optical filter is controlled by monitoring.

According to a third aspect of the present invention, there is provided an optical transmission apparatus for converting an electric signal into an optical signal and transmitting the converted signal, wherein the monitor signal generator generates a monitor signal, and multiplexes the electric signal to be transmitted with the monitor signal. A multiplexing unit, an electro-optical conversion unit that converts an output electric signal of the multiplexing unit into an optical signal by direct intensity modulation, an optical amplification unit that amplifies an output optical signal of the electro-optical conversion unit, and an output optical signal of the electro-optical conversion unit Optical filter, which has a transmission wavelength band of a predetermined width whose center wavelength can be changed, removes noise components from the optical signal guided by the optical fiber, and controls the center wavelength of the transmission wavelength band of the optical filter An optical filter control unit, a photoelectric conversion unit that converts an output optical signal of the optical filter into an electric signal, and a separation unit that separates the output electric signal of the photoelectric conversion unit into an electric signal to be transmitted and a monitor signal, Optical filter control When the electric signal to be transmitted is an analog signal, the monitor signal output by the separation unit is monitored to set the center wavelength of the transmission wavelength band of the optical filter so that the power of the output electric signal of the photoelectric conversion unit is maximum. It is characterized in that it is controlled so that

In the third aspect, when the electric signal to be transmitted is an analog signal, the center of the transmission wavelength band of the optical filter is controlled so that the electric power of the electric signal output from the photoelectric converter becomes maximum. Therefore, it is sufficient to measure the power of the output electric signal of the photoelectric conversion unit, so that good transmission characteristics can be obtained with a simple configuration. Further, since the above control is performed by monitoring a monitor signal different from the electric signal to be transmitted, the transmission efficiency is improved as compared with the case where the electric signal to be transmitted is monitored.

According to a fourth aspect of the present invention, in the third aspect, in the optical frequency modulation generated at the time of the electro-optical conversion in the electro-optical converter, the frequency modulation index by the electric signal to be transmitted and the frequency modulation index by the monitor signal are mutually different. It is characterized by being equal.

A fifth aspect of the present invention is an optical transmission device for converting n (n is an arbitrary integer of 2 or more; the same applies hereinafter) electrical signals into optical signals and multiplexing and transmitting the optical signals. N number of electro-optical converters for converting an electric signal to be transmitted into first to n-th optical signals by direct intensity modulation, an optical multiplexing unit for multiplexing output optical signals of the respective electro-optical converters, and an optical multiplexing unit An optical fiber that guides the output optical signal of the unit, having a transmission wavelength band of a predetermined width whose center wavelength can be changed, and extracting any one of the first to n-th optical signals from the optical signal guided by the optical fiber An optical filter, an optical filter control unit that controls a center wavelength of a transmission wavelength band of the optical filter, and an opto-electrical conversion unit that converts an output optical signal of the optical filter into an electric signal. If the signal is an analog signal,
The center wavelength of the transmission wavelength band of the optical filter is controlled so that the power of the output electric signal of the photoelectric conversion unit is maximized.

According to the fifth aspect, when the electric signal to be transmitted is an analog signal, the center of the transmission wavelength band of the optical filter is controlled so that the electric power of the electric signal output from the photoelectric converter becomes maximum. I do. Therefore, it is sufficient to measure the power of the output electric signal of the photoelectric conversion unit, so that good transmission characteristics can be obtained with a simple configuration.

According to a sixth aspect based on the fifth aspect, the apparatus further comprises a branching unit for branching the output electric signal of the photoelectric conversion unit into two, and the optical filter control unit converts one of the two output electric signals of the branching unit. The center wavelength of the transmission wavelength band of the optical filter is controlled by monitoring.

According to a seventh aspect of the present invention, there is provided an optical transmission apparatus for converting n electrical signals (n is an arbitrary integer of 2 or more; the same applies hereinafter) into optical signals and multiplexing them with each other for transmission. N monitor signal generating units for generating signals, n multiplexing units for multiplexing each electric signal to be transmitted and the monitor signal with each other, and output electric signals of each multiplexing unit are subjected to a first intensity modulation by a first intensity modulation. To n-th
N optical-to-optical converters that convert optical signals into optical signals, an optical multiplexing unit that multiplexes the output optical signals of each electro-optical converter with each other, an optical fiber that guides the output optical signal of the optical multiplexing unit, and its center wavelength can be changed An optical filter that has a transmission wavelength band of a predetermined width and extracts one of the first to n-th optical signals from an optical signal guided by an optical fiber, and light that controls the center wavelength of the transmission wavelength band of the optical filter. A filter control unit, a photoelectric conversion unit for converting an output optical signal of the optical filter into an electric signal, and a separation unit for separating an output electric signal of the photoelectric conversion unit into an electric signal to be transmitted and a monitor signal; The unit monitors the monitor signal output by the separation unit when each of the electric signals to be transmitted is an analog signal, thereby setting the center wavelength of the transmission wavelength band of the optical filter to the output electric signal of the photoelectric conversion unit. Maximum power It is characterized by controlling so.

According to the seventh aspect, when the electric signal to be transmitted is an analog signal, the center of the transmission wavelength band of the optical filter is controlled so that the power of the output electric signal of the photoelectric conversion unit is maximized. I do. Therefore, it is sufficient to measure the power of the output electric signal of the photoelectric conversion unit, so that good transmission characteristics can be obtained with a simple configuration. Further, since the above control is performed by monitoring a monitor signal different from the electric signal to be transmitted, the transmission efficiency is improved as compared with the case where the electric signal to be transmitted is monitored.

According to an eighth invention, in the seventh invention, in the optical frequency modulation generated at the time of the electro-optical conversion in each electro-optical converter, the frequency modulation index of the electric signal to be transmitted and the frequency modulation index of the monitor signal are different. It is characterized by being equal to each other.

A ninth invention is a method of converting an electric signal into an optical signal and transmitting the converted signal. The electric signal to be transmitted is directly converted into an optical signal by intensity modulation, and the obtained optical signal is converted. The amplified optical signal is guided by an optical fiber, and the center wavelength of the optical signal is changed by an optical filter having a transmission wavelength band of a predetermined width that can be changed to remove noise components from the guided optical signal. When controlling the center wavelength, converting the optical signal obtained by the removal into an electric signal, and controlling the center wavelength of the transmission wavelength band of the optical filter, if the electric signal to be transmitted is an analog signal, the optical filter Is controlled so that the power of an electric signal obtained by converting the center wavelength of the transmission wavelength band is maximized.

A tenth invention is a method of converting an electric signal into an optical signal and transmitting the optical signal. The method generates a monitor signal, multiplexes the electric signal to be transmitted with the monitor signal, and multiplexes the monitor signal. The electrical signal is converted to an optical signal by direct intensity modulation,
Amplify the optical signal obtained by the conversion, guide the optical signal obtained by the amplification, and remove the noise component from the guided optical signal by an optical filter having a transmission wavelength band of a predetermined width in which the center wavelength can be changed. Controlling the center wavelength of the transmission wavelength band of the optical filter, converting the optical signal obtained by the removal into an electrical signal, separating the converted electrical signal into an electrical signal to be transmitted and a monitor signal, When controlling the center wavelength of the transmission wavelength band of the filter, if the electric signal to be transmitted is an analog signal, the center wavelength of the transmission wavelength band of the optical filter is monitored by monitoring the monitor signal obtained separately. , Is controlled so that the power of the electric signal obtained by the conversion is maximized.

An eleventh invention is a method of converting n electrical signals (n is an arbitrary integer of 2 or more; the same applies hereinafter) into optical signals and multiplexing them with each other for transmission. The electric signal to be converted is converted into the first to n-th optical signals by direct intensity modulation, the first to n-th optical signals are multiplexed with each other, and an optical signal obtained by multiplexing is derived, and the center wavelength is An optical filter having a changeable transmission wavelength band having a predetermined width extracts one of the first to n-th optical signals from the guided optical signal, and controls and extracts the center wavelength of the transmission wavelength band of the optical filter. When the optical signal obtained by the above is converted into an electric signal and the center wavelength of the transmission wavelength band of the optical filter is controlled, when the electric signal to be transmitted is an analog signal, the center of the transmission wavelength band of the optical filter is controlled. The wavelength is controlled so that the power of the electrical signal obtained by conversion is maximized. It is characterized in that.

A twelfth invention is a method of converting n electrical signals (n is an arbitrary integer of 2 or more; the same applies hereinafter) into optical signals, multiplexing them with each other, and transmitting the optical signals. The generated electric signals to be transmitted and the monitor signal are multiplexed with each other, and the electric signals obtained by the multiplexing are converted into first to n-th optical signals by direct intensity modulation. n optical signals are optically multiplexed with each other, an optical signal obtained by optically multiplexing the optical signals is derived, and an optical filter having a transmission wavelength band of a predetermined width whose center wavelength can be changed is used to convert the first to n-th optical signals from the guided optical signals. The optical signal to be extracted is controlled, the center wavelength of the transmission wavelength band of the optical filter is controlled, the optical signal obtained by the extraction is converted into an electric signal, and the electric signal obtained by the conversion is transmitted. And the monitor signal, and controls the center wavelength of the transmission wavelength band of the optical filter. In this case, when the electric signal to be transmitted is an analog signal, by monitoring the monitor signal obtained separately, the power of the electric signal obtained by converting the center wavelength of the transmission wavelength band of the optical filter is converted. Is controlled to be maximum.

[0028]

(First Embodiment) FIG. 1 is a block diagram showing a configuration of an optical transmission device according to a first embodiment of the present invention. In FIG. 1, an optical transmission device (hereinafter, referred to as an optical transmission device) according to a first embodiment of the present invention includes an electro-optical converter 10, an optical amplifier 11, an optical fiber 12, an optical filter 1,
3, an optical filter control unit 14, a photoelectric conversion unit 15, and a branch unit 16.

The electro-optical converter 10 converts an electric signal to be transmitted into an optical signal by direct intensity modulation. Optical amplifier 1
1 amplifies the output optical signal of the electro-optical converter 10. The optical fiber 12 guides an output optical signal of the optical amplifier 11. The optical filter 13 has a transmission wavelength band of a predetermined width whose center wavelength can be changed, and removes a noise component from the optical signal guided by the optical fiber 12. The optical filter control unit 14
The center wavelength of the transmission wavelength band of the optical filter 13 is controlled.
The photoelectric conversion unit 15 converts the output optical signal of the optical filter 13 into an electric signal. The branching unit 16 branches the output electric signal of the photoelectric conversion unit 15 into two.

Hereinafter, the operation of the conventional optical transmission device will be described. First, an electric signal to be transmitted is input to the electro-optical converter 10. The electric signal to be transmitted is an analog signal. The electro-optical converter 10 converts an input electric signal into an optical signal. Then, the output optical signal of the electro-optical converter 10 is input to the optical amplifier 11. The optical amplifier 11 amplifies an input optical signal. The output optical signal of the optical amplifier 11 is
And input to the optical filter 13.

The input optical signal to the optical filter 13 contains a noise component due to the spontaneous emission light generated in the optical amplifier 11. The optical filter 13 removes this noise component from the input optical signal. Then, the output optical signal of the optical filter 13 is input to the photoelectric conversion unit 15. Photoelectric conversion unit 15
Converts an input optical signal into an electrical signal. Photoelectric conversion unit 1
The output electric signal 5 is input to the branching unit 16. The branching unit 16 branches the input electric signal into two. One of the output electric signals of the branching unit 16 is input to a demodulator or the like (not shown), and the other is input to the optical filter control unit 14.

The optical filter control unit 14 is provided with the optical filter 13
Center wavelength of transmission wavelength band (hereinafter, center of transmission wavelength band)
Is controlled so that the power of the input electric signal (the power of the output electric signal of the photoelectric conversion unit 15) is maximized. Thereby, when the electric signal to be transmitted is an analog signal, the signal-to-noise ratio of the demodulated signal is maximized, so that good transmission characteristics can be obtained.

The electric power of the electric signal input to the optical filter control unit 14 is maximized (ie, the photoelectric conversion unit 15
(The power of the output electric signal of the optical filter 13 becomes maximum) when the center of the transmission wavelength band of the optical filter 13 is shifted by a certain distance from the wavelength of the output optical signal of the optical filter 13. The difference between the center of the transmission wavelength band of the optical filter 13 and the wavelength of the output optical signal of the optical filter 13 (dL; dL = output optical signal wavelength−center of the transmission wavelength band) and the power of the output electric signal of the photoelectric conversion unit 15 ( FIG. 2 shows an example of the relationship with the carrier level.

In FIG. 2, the solid line indicates d when the optical signal input to the optical filter 13 is not subjected to optical frequency modulation.
The relationship between L and the carrier level is shown. The dotted line indicates the relationship between dL and the carrier level when the optical signal input to the optical filter 13 has been subjected to optical frequency modulation. It is to be noted that the electric signal input to the electro-optical converter 10 is a sine wave having a frequency of 3927 [MHz], the light modulation degree of the electro-optical converter 10 is 20 [%], and the electro-optical converter 10 is illustrated. Bias current (not shown) to 50 [m
A], the chirp amount of the electro-optical converter 10 is set to 700 [MHz].
/ MA] and the 3 dB band of the optical filter 13 is set to 0.51 [n
m].

Here, the optical frequency modulation will be described. For example, in FIG. 1, the electro-optical converter 10 converts an input electric signal into an optical signal by direct intensity modulation,
At this time, generally, the output optical signal of the electro-optical converter 10 is an optical signal having not only an intensity modulation component but also a frequency modulation component. The phenomenon in which an optical signal undergoes not only intensity modulation but also frequency modulation when an electric signal is converted into an optical signal by direct intensity modulation is called optical frequency modulation.

As shown in FIG. 2, when the optical signal has not been subjected to optical frequency modulation, dL = 0, that is, the center of the transmission wavelength band of the optical filter 13 coincides with the wavelength of the output optical signal of the optical filter 13. Sometimes the carrier level is at a maximum. On the other hand, when the optical signal is subjected to optical frequency modulation, dL 0.2, that is, the center of the transmission wavelength band of the optical filter 13 is shorter than the wavelength of the output optical signal of the optical filter 13 by about 0.2 [nm]. When shifted to the side, the carrier level is at the maximum. Note that this shift is considered to occur because a part of the frequency modulation component of the optical signal is converted into an intensity modulation component when passing through the optical filter 13, and as a result, the wavelength of the output optical signal of the optical filter 13 fluctuates. Can be

As described above, in this embodiment, when the electric signal to be transmitted is an analog signal, the photoelectric conversion unit 1
The center of the transmission wavelength band of the optical filter 13 is controlled so that the power of the output electric signal of No. 5 is maximized. Therefore, it is sufficient to measure the power of the output electric signal of the photoelectric conversion unit 15, so that good transmission characteristics can be obtained with a simple configuration.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
It is a block diagram showing the composition of the optical transmission device concerning an embodiment. In FIG. 3, an optical transmission device (hereinafter, an optical transmission device) according to a second embodiment of the present invention includes a monitor signal generator 2
0, multiplexing unit 21, electric-optical conversion unit 22, optical amplification unit 23, optical fiber 24, optical filter 25, optical filter control unit 2
6, a photoelectric conversion unit 27 and a separation unit 28 are provided.

The monitor signal generator 20 generates a monitor signal. The multiplexing unit 21 multiplexes the electric signal to be transmitted and the monitor signal. The electro-optical converter 22 converts the output electric signal of the multiplexer 21 into an optical signal by direct intensity modulation.
The optical amplifier 23 amplifies the output optical signal of the electro-optical converter 22. The optical fiber 24 guides the output optical signal of the optical amplifier 23. The optical filter 25 has a transmission wavelength band of a predetermined width whose center wavelength can be changed, and removes a noise component from the optical signal guided by the optical fiber 24. The optical filter control unit 26 controls the center wavelength of the transmission wavelength band of the optical filter 25. The photoelectric conversion unit 27 converts the output optical signal of the optical filter 25 into an electric signal. The separation unit 28 separates the output electric signal of the photoelectric conversion unit 27 into an electric signal to be transmitted and a monitor signal.

Hereinafter, the operation of the conventional optical transmission device will be described. First, the monitor signal generator 20 generates a monitor signal, and the electric signal to be transmitted and the monitor signal are input to the multiplexer 21. The electrical and monitor signals to be transmitted are
It is an analog signal. The output electric signal of the multiplexing unit 21 is input to the electro-optical conversion unit 22. The electro-optical converter 22 converts an input electric signal into an optical signal. Then, the output optical signal of the electro-optical converter 22 is input to the optical amplifier 23. The optical amplifier 23 amplifies an input optical signal. The output optical signal of the optical amplifier 23 is guided by the optical fiber 24 and input to the optical filter 25.

The optical signal input to the optical filter 25 contains a noise component due to spontaneous emission light generated in the optical amplifier 23. The optical filter 25 removes this noise component from the input optical signal. Then, the output optical signal of the optical filter 25 is input to the photoelectric conversion unit 27. Photoelectric conversion unit 27
Converts an input optical signal into an electrical signal. Photoelectric conversion unit 2
7 is input to the separation unit 28. The separation unit 28 separates the input electric signal into an electric signal to be transmitted and a monitor signal. The electric signal to be transmitted output from the separation unit 28 is input to a demodulator or the like (not shown), and the monitor signal is input to the optical filter control unit 26.

The optical filter control section 26 includes an optical filter 25
Center wavelength of transmission wavelength band (hereinafter, center of transmission wavelength band)
Is controlled such that the power of the monitor signal (∝the power of the output electric signal of the photoelectric conversion unit 27) is maximized. Thereby, when the electric signal to be transmitted is an analog signal, the signal-to-noise ratio of the demodulated signal is maximized, so that good transmission characteristics can be obtained.

The reason that the power of the monitor signal becomes maximum (that is, the power of the output electric signal of the photoelectric conversion unit 27 becomes maximum) is that the center of the transmission wavelength band of the optical filter 25 is the output light of the optical filter 25. This is when the wavelength deviates from the signal wavelength by a certain distance. The relationship between the difference between the center of the transmission wavelength band of the optical filter 25 and the wavelength of the output optical signal of the optical filter 25 and the power of the output electrical signal of the photoelectric converter 27 is determined when the electro-optical converter 22 converts the electric light into light. In the resulting optical frequency modulation, when the frequency modulation index of the electric signal to be transmitted and the frequency modulation index of the monitor signal are equal to each other, FIG.
Is the same as

As described above, in this embodiment, when the electric signal to be transmitted is an analog signal, the photoelectric conversion unit 2
The center of the transmission wavelength band of the optical filter 25 is controlled so that the power of the output electric signal of the signal 7 becomes maximum. Therefore, it is sufficient to measure the power of the output electric signal of the photoelectric conversion unit 27, so that good transmission characteristics can be obtained with a simple configuration. Also, since the above control is performed by monitoring a monitor signal different from the electric signal to be transmitted, unlike the first embodiment in which the electric signal to be transmitted is monitored, the electric signal to be transmitted is not branched. The transmission efficiency is good.

In the first and second embodiments, the optical filters (13, 25) remove noise components caused by spontaneous emission light generated during optical amplification. In the fourth embodiment, the optical filter (33,
45) selects a desired optical signal from the optical signal obtained by multiplexing a plurality of optical signals.

(Third Embodiment) FIG. 4 shows a third embodiment of the present invention.
It is a block diagram showing the composition of the optical transmission device concerning an embodiment. In FIG. 4, an optical transmission device (hereinafter, an optical transmission device) according to a third embodiment of the present invention includes n (n is an arbitrary integer of 2 or more) electro-optical conversion units 30, an optical multiplexing unit 31, Optical fiber 32, optical filter 33, optical filter control unit 34,
A photoelectric conversion unit 35 and a branch unit 36 are provided.

Each electro-optical converter 30 converts an electric signal to be transmitted into an optical signal by direct intensity modulation. The optical multiplexing unit 31 multiplexes the output optical signals (the first optical signal to the n-th optical signal) of the respective electro-optical conversion units 30. Optical fiber 32
Guides the output optical signal of the optical multiplexing unit 31. Optical filter 33
Has a transmission wavelength band of a predetermined width whose center wavelength can be changed, and converts a desired optical signal (any one of the first optical signal to the n-th optical signal) from the optical signal guided by the optical fiber 32. Extract. The optical filter control unit 34 controls the center wavelength of the transmission wavelength band of the optical filter 33. Photoelectric conversion unit 35
Converts the optical signal output from the optical filter 33 into an electric signal. The branching unit 36 branches the output electric signal of the photoelectric conversion unit 35 into two.

Hereinafter, the operation of the conventional optical transmission device will be described. First, the electrical signal to be transmitted is
Is input to The electric signal to be transmitted is an analog signal. Each electro-optical converter 30 converts an input electric signal into an optical signal. Then, the output optical signal of each electro-optical conversion unit 30 is input to the optical multiplexing unit 31. The optical multiplexing unit 31 multiplexes the input optical signals (first to n-th optical signals) with each other.
The output optical signal of the optical multiplexing unit 31 is guided by the optical fiber 32 and input to the optical filter 33.

The input optical signal to the optical filter 33 includes the first
To n-th optical signal. Optical filter 3
3 extracts any of the first to n-th optical signals from the input optical signal. Then, the output optical signal of the optical filter 33 is input to the photoelectric conversion unit 35. Photoelectric conversion unit 35
Converts an input optical signal into an electrical signal. Photoelectric conversion unit 3
The output electric signal of No. 5 is input to the branching unit 36. The branching unit 36 branches the input electric signal into two. One of the output electric signals of the branching unit 36 is input to a demodulator (not shown) and the other is input to the optical filter control unit 34.

The optical filter control unit 34 includes an optical filter 33
Center wavelength of transmission wavelength band (hereinafter, center of transmission wavelength band)
To the power of the input electric signal to the optical filter control unit 34 (∝
The control is performed so that the output electric power of the photoelectric conversion unit 35 is maximized. Thereby, when the electric signal to be transmitted is an analog signal, the signal-to-noise ratio of the demodulated signal is maximized, so that good transmission characteristics can be obtained.

The power of the electric signal input to the optical filter control unit 34 is maximized (ie, the photoelectric conversion unit 35).
(The power of the output electric signal becomes maximum) when the center of the transmission wavelength band of the optical filter 33 is shifted from the wavelength of the output optical signal of the optical filter 33 by a certain distance. The relationship between the difference between the center of the transmission wavelength band of the optical filter 33 and the wavelength of the output optical signal of the optical filter 33 and the power of the output electrical signal of the photoelectric converter 35 is the same as in FIG.

As described above, in this embodiment, when the electric signal to be transmitted is an analog signal, the photoelectric conversion unit 3
The center of the transmission wavelength band of the optical filter 33 is controlled so that the power of the output electric signal of No. 5 is maximized. Therefore, it is sufficient to measure the power of the output electric signal of the photoelectric conversion unit 35, so that good transmission characteristics can be obtained with a simple configuration.

(Fourth Embodiment) FIG. 5 shows a fourth embodiment of the present invention.
It is a block diagram showing the composition of the optical transmission device concerning an embodiment. In FIG. 5, an optical transmission device (hereinafter, referred to as an optical transmission device) according to a fourth embodiment of the present invention includes n monitor signal generators 40 and n multiplexers corresponding to each monitor signal generator 40. 41, n electrical-to-optical converters 42 corresponding to each multiplexer 41, optical multiplexer 43, optical fiber 44, optical filter 4
5, an optical filter control unit 46, a photoelectric conversion unit 47, and a separation unit 48.

Each monitor signal generator 40 generates a monitor signal. Each multiplexing unit 41 multiplexes an electric signal to be transmitted and a monitor signal. Each electro-optical conversion unit 42 converts an output electric signal of the corresponding multiplexing unit 41 into an optical signal by direct intensity modulation. The optical multiplexing unit 43 multiplexes the output optical signals of the respective electro-optical conversion units 42 with each other. The optical fiber 44 guides an optical signal output from the optical multiplexing unit 43. The optical filter 45 has a transmission wavelength band of a predetermined width whose center wavelength can be changed, and converts an optical signal guided by the optical fiber 44 into a desired optical signal (any one of the first to n-th optical signals). Or). The optical filter control unit 46 controls the center wavelength of the transmission wavelength band of the optical filter 45. The photoelectric conversion unit 47 converts the output optical signal of the optical filter 45 into an electric signal. The separation unit 48 separates the output electric signal of the photoelectric conversion unit 47 into an electric signal to be transmitted and a monitor signal.

The operation of the conventional optical transmission device will be described below. First, each monitor signal generation unit 40 generates a monitor signal, and the electric signal to be transmitted and the monitor signal are combined into each multiplexing unit 4.
1 is input. The electric signal and the monitor signal to be transmitted are analog signals. Each multiplexing unit 41 multiplexes an electric signal to be transmitted and a monitor signal. The output electric signal of each multiplexing unit 41 is input to the corresponding electro-optical conversion unit 42. Each electro-optical converter 42 converts an input electric signal into an optical signal. Then, the output optical signals of the respective electro-optical conversion units 42 are input to the optical multiplexing unit 43. The optical multiplexing unit 43 multiplexes the input optical signals (first optical signal to n-th optical signal) with each other. The output optical signal of the optical multiplexing unit 43 is guided by the optical fiber 44 and input to the optical filter 45.

The input optical signal to the optical filter 45 includes the first
To n-th optical signal. Optical filter 4
5 extracts any of the first to n-th optical signals from the input optical signal. Then, the output optical signal of the optical filter 45 is input to the photoelectric conversion unit 47. Photoelectric conversion unit 47
Converts an input optical signal into an electrical signal. Photoelectric conversion unit 4
7 is input to the separation unit 48. The separating unit 48 separates the input electric signal into an electric signal to be transmitted and a monitor signal. The electric signal to be transmitted output from the separation unit 48 is input to a demodulator (not shown) or the like, and the monitor signal is input to the optical filter control unit 46.

The optical filter controller 46 includes an optical filter 45
Center wavelength of transmission wavelength band (hereinafter, center of transmission wavelength band)
Is controlled so that the power of the monitor signal (the power of the output electric signal of the photoelectric conversion unit 47) is maximized. Thereby, when the electric signal to be transmitted is an analog signal, the signal-to-noise ratio of the demodulated signal is maximized, so that good transmission characteristics can be obtained.

The reason why the power of the monitor signal becomes maximum (that is, the power of the output electric signal of the photoelectric conversion unit 47 becomes maximum) is that the center of the transmission wavelength band of the optical filter 45 is the output light of the optical filter 45. This is when the wavelength deviates from the signal wavelength by a certain distance. The relationship between the difference between the center of the transmission wavelength band of the optical filter 45 and the wavelength of the output optical signal of the optical filter 45 and the power of the output electrical signal of the photoelectric converter 47 is determined when the electro-optical converter 42 converts the electro-optical signal. In the resulting optical frequency modulation, when the frequency modulation index of the electric signal to be transmitted and the frequency modulation index of the monitor signal are equal to each other, FIG.
Is the same as

As described above, in this embodiment, when the electric signal to be transmitted is an analog signal, the photoelectric conversion unit 4
The center of the transmission wavelength band of the optical filter 45 is controlled so that the power of the output electric signal of the optical filter 7 becomes maximum. Therefore, it is sufficient to measure the power of the output electric signal of the photoelectric conversion unit 47, so that good transmission characteristics can be obtained with a simple configuration. Also, since the above control is performed by monitoring a monitor signal different from the electric signal to be transmitted, unlike the third embodiment in which the electric signal to be transmitted is monitored, the electric signal to be transmitted is not branched. The transmission efficiency is good.

[Brief description of the drawings]

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

FIG. 2 shows the difference (dL) between the center of the transmission wavelength band of the optical filter 13 in FIG. 1 and the wavelength of the output optical signal of the optical filter 13 and the power (carrier level) of the output electrical signal of the photoelectric converter 15. It is a figure showing an example of a relation.

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

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

FIG. 5 is a block diagram illustrating a configuration of an optical transmission device according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration of a conventional optical transmission device.

FIG. 7 is a block diagram illustrating a configuration of another conventional optical transmission device.

[Explanation of symbols]

 10, 22, 30, 42 electro-optical converter 11, 23 optical amplifier 12, 24, 32, 44 optical fiber 13, 25, 33, 45 optical filter 14, 26, 34, 46 optical filter controller 15, 27, 35, 47 photoelectric conversion section 16, 36 branch section 20, 40 monitor signal generation section 21, 41 multiplexing section 28, 48 demultiplexing section 31, 43 optical multiplexing section

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masanori Iida 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5F072 HH02 HH05 KK30 MM20 YY17

Claims (12)

[Claims] 1. An optical transmission device for converting an electric signal into an optical signal and transmitting the converted signal, wherein the electro-optical converter converts the electric signal to be transmitted into an optical signal by direct intensity modulation. An optical amplifier that amplifies an output optical signal; an optical fiber that guides an output optical signal of the electro-optical converter; an optical signal that has a transmission wavelength band of a predetermined width whose center wavelength can be changed, and is guided by the optical fiber An optical filter that removes a noise component from the optical filter, an optical filter control unit that controls a center wavelength of a transmission wavelength band of the optical filter, and a photoelectric conversion unit that converts an output optical signal of the optical filter into an electric signal, When the electric signal to be transmitted is an analog signal, the filter control unit controls the center wavelength of the transmission wavelength band of the optical filter so that the power of the output electric signal of the photoelectric conversion unit is maximized. An optical transmission device, comprising: 2. The optical filter according to claim 1, further comprising: a branching unit that branches the output electric signal of the photoelectric conversion unit into two, wherein the optical filter control unit monitors one of the two output electric signals of the branching unit, thereby obtaining the light. 2. The optical transmission device according to claim 1, wherein a central wavelength of a transmission wavelength band of the filter is controlled. 3. An optical transmission device for converting an electric signal into an optical signal and transmitting the converted signal, comprising: a monitor signal generator for generating a monitor signal; and a multiplexer for multiplexing the electric signal to be transmitted and the monitor signal. An electric-to-optical conversion unit that converts an output electric signal of the multiplexing unit into an optical signal by direct intensity modulation; an optical amplifying unit that amplifies an output optical signal of the electro-optical conversion unit; an output optical signal of the electro-optical conversion unit An optical fiber that has a transmission wavelength band of a predetermined width whose center wavelength can be changed, and removes a noise component from an optical signal guided by the optical fiber; a center wavelength of the transmission wavelength band of the optical filter An optical filter control unit that controls an optical filter, an optical-electrical conversion unit that converts an output optical signal of the optical filter into an electrical signal, and separates an output electrical signal of the optical-electrical conversion unit into the electrical signal to be transmitted and the monitor signal. When the electric signal to be transmitted is an analog signal, the optical filter control unit monitors a monitor signal output by the separation unit, thereby controlling a center wavelength of a transmission wavelength band of the optical filter. Is controlled so that the power of the output electric signal of the photoelectric conversion unit is maximized,
Optical transmission device. 4. An optical frequency modulation generated at the time of electro-optical conversion in the electro-optical converter, wherein a frequency modulation index by the electric signal to be transmitted and a frequency modulation index by the monitor signal are equal to each other. The optical transmission device according to claim 3. 5. An optical transmission device for converting n electric signals (n is an arbitrary integer of 2 or more; the same applies hereinafter) into optical signals and multiplexing them with each other for transmission, wherein each electric signal to be transmitted is N number of electro-optical converters for converting a signal into first to n-th optical signals by direct intensity modulation, an optical multiplexer for multiplexing output optical signals of the respective electro-optical converters with each other, An optical fiber for guiding an output optical signal, having a transmission wavelength band of a predetermined width whose center wavelength can be changed, and extracting any one of the first to n-th optical signals from the optical signal guided by the optical fiber An optical filter, comprising: an optical filter control unit that controls a center wavelength of a transmission wavelength band of the optical filter; and an opto-electric conversion unit that converts an output optical signal of the optical filter into an electric signal. The electric signal to be transmitted is an analog signal. An optical transmission device, wherein a central wavelength of a transmission wavelength band of the optical filter is controlled so that power of an output electric signal of the photoelectric conversion unit is maximized. 6. The optical filter control section further includes a branching section for branching an output electric signal of the photoelectric conversion section into two, and the optical filter control section monitors one of the two output electric signals of the branching section so as to monitor the optical signal. The optical transmission device according to claim 5, wherein a center wavelength of a transmission wavelength band of the filter is controlled. 7. An optical transmission device for converting n electrical signals (n is an arbitrary integer of 2 or more; the same applies hereinafter) into optical signals and multiplexing them with each other for transmission, and generates a monitor signal. n monitor signal generating units, n multiplexing units for multiplexing each of the electric signals to be transmitted and the monitor signal with each other, and output electric signals of the multiplexing units are first to n number of electro-optical converters for converting into n optical signals, an optical multiplexer for multiplexing the output optical signals of the respective electro-optical converters with each other, an optical fiber for guiding the output optical signal of the optical multiplexer, a center wavelength thereof An optical filter having a variable transmission wavelength band of a predetermined width, and extracting any one of the first to n-th optical signals from the optical signal guided by the optical fiber; An optical filter control unit for controlling a center wavelength; An optical-electrical conversion unit that converts an optical signal into an electric signal, a separation unit that separates the output electric signal of the photoelectric conversion unit into the electric signal to be transmitted and the monitor signal, and the optical filter control unit includes: When the electric signal to be transmitted is an analog signal, by monitoring the monitor signal output by the separation unit, the center wavelength of the transmission wavelength band of the optical filter is changed to the power of the output electric signal of the photoelectric conversion unit. An optical transmission device, wherein the control is performed so that is maximized. 8. An optical frequency modulation generated at the time of electro-optical conversion in each of the electro-optical converters, wherein a frequency modulation index by the electric signal to be transmitted and a frequency modulation index by the monitor signal are equal to each other. The optical transmission device according to claim 7. 9. A method of converting an electric signal into an optical signal and transmitting the converted signal, wherein the electric signal to be transmitted is directly converted into an optical signal by intensity modulation, and the converted optical signal is amplified. The optical signal is guided by an optical fiber, a noise component is removed from the guided optical signal by an optical filter having a transmission wavelength band of a predetermined width in which the center wavelength can be changed, and the center wavelength of the transmission wavelength band of the optical filter is changed. Controlling, converting the optical signal obtained by the removal into an electric signal, and controlling the center wavelength of the transmission wavelength band of the optical filter, when the electric signal to be transmitted is an analog signal, An optical transmission method characterized by controlling a central wavelength of a transmission wavelength band so that electric power of an electric signal obtained by conversion is maximized. 10. A method for converting an electric signal into an optical signal and transmitting the same, comprising: generating a monitor signal; multiplexing the electric signal to be transmitted with the monitor signal; and multiplexing the electric signal. Is directly converted into an optical signal by intensity modulation, an optical signal obtained by the conversion is amplified, an optical signal obtained by the amplification is guided, and an optical filter having a transmission wavelength band of a predetermined width whose center wavelength can be changed. By removing the noise component from the guided optical signal, controlling the center wavelength of the transmission wavelength band of the optical filter, converting the optical signal obtained by the removal into an electric signal, and converting the electric signal obtained by the conversion into the electric signal A monitor signal that is separated into an electric signal to be transmitted and the monitor signal, and is separated when the electric signal to be transmitted is an analog signal when controlling the center wavelength of the transmission wavelength band of the optical filter. The moni It allows the center wavelength of the transmission wavelength band of the optical filter, and the controller controls so that the power of the electric signal obtained by conversion is maximized, optical transmission method for. 11. A method of converting n electric signals (n is an arbitrary integer of 2 or more; the same applies hereinafter) into optical signals and multiplexing them with each other for transmission, wherein each electric signal to be transmitted is Converting the first to n-th optical signals by direct intensity modulation, multiplexing the first to n-th optical signals with each other, leading an optical signal obtained by the multiplexing, and changing the center wavelength thereof The first to n-th light signals are guided by an optical filter having a transmission wavelength band of a predetermined width.
Extracting any one of the optical signals, controlling the center wavelength of the transmission wavelength band of the optical filter, converting the extracted optical signal into an electrical signal, and setting the center wavelength of the transmission wavelength band of the optical filter. When controlling, when each of the electric signals to be transmitted is an analog signal, the central wavelength of the transmission wavelength band of the optical filter is controlled so that the power of the electric signal obtained by conversion is maximized. Characteristic optical transmission method. 12. A method of converting n electrical signals (n is an arbitrary integer of 2 or more; the same applies hereinafter) into optical signals, multiplexing them with each other, and transmitting the optical signals. The electric signal to be transmitted and the monitor signal are multiplexed with each other, and the electric signals obtained by the multiplexing are converted into first to n-th optical signals by direct intensity modulation. The optical signals are optically multiplexed with each other, an optical signal obtained by optical multiplexing is derived, and the first to n-th optical signals are derived from the optical signal guided by an optical filter having a transmission wavelength band of a predetermined width in which the center wavelength can be changed. Extracting one of the optical signals, controlling the center wavelength of the transmission wavelength band of the optical filter, converting the extracted optical signal into an electrical signal, and converting the electrical signal obtained by the conversion into the electrical signal to be transmitted. Signal and the monitor signal, and transmitted through the optical filter. When controlling the center wavelength of the long band, if the electric signal to be transmitted is an analog signal, the center wavelength of the transmission wavelength band of the optical filter is converted by monitoring a monitor signal obtained by separation. An optical transmission method characterized in that control is performed so that the power of an electric signal obtained as a result is maximized.