JP2000307522A - Light sending device and light transmitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence of distortion in the band of a multi-channel signal which is affected by a group delay deviation on a reception device side and is frequency-multiplexed after FM modulation by reducing a harmonies signal that an FM collective modulation signal has and transmitting it. SOLUTION: An FM collection modulation signal obtained by modulating the collective frequency of a frequency multiplex multi-channel signal to an FM modulator 1 is amplified by a wide band amplifier 2. The harmonies signal of the FM collective modulation signal generated in an FM modulator 1 and the wide band amplifier 2 is reduced and is given to a light modulator 4 in a harmonies reducer 3. The intensity of signal light is modulated and is light- transmitted through an optical fiber transmission line 6. The light signal is photoelectrically converted in a light receiver 7 and the FM collective modulation signal is obtained. It is FM-modulated by an FM demodulator 8 and the multi-channel signal of frequency multiplex is reproduced. The harmonies signal that the FM collective conversion signal generated in the FM modulator 1 and the wide band amplifier 2 has is reduced and it can be transmitted in the harmonies reducer 3 of a light transmission device 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device and an optical transmission device for collectively frequency-modulating a frequency-multiplexed multi-channel signal for optical transmission.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a configuration of a conventional optical transmission apparatus for transmitting frequency-multiplexed multi-channel signals by collectively frequency-modulating the signals. In FIG. 1, an FM modulator 1 frequency-modulates a carrier signal by a frequency-multiplexed multi-channel signal. The broadband amplifier 2 amplifies the FM batch modulation signal, and the optical modulator 4 modulates the intensity of the signal light with the FM batch modulation signal. An optical transmitter 5 is constituted by the FM modulator 1 to the optical modulator 4.

An optical fiber transmission line 6 transmits a modulated optical signal, and an optical receiver 7 photoelectrically converts the transmitted optical signal. The FM demodulator 8 FM-demodulates the FM batch modulation signal and outputs a frequency-multiplexed multi-channel signal. An optical receiver 9 is constituted by the optical receiver 7 and the FM demodulator 8.

[0004]

In the conventional optical transmission device, the harmonic signal of the FM batch modulation signal generated by the FM modulator 1 and the broadband amplifier 2 is affected by the group delay deviation in the optical receiver 7, As a result, distortion generated in the frequency-multiplexed multi-channel signal band after the FM demodulation may increase.

The present invention has been made to solve such a conventional problem. A harmonic signal included in an FM batch modulation signal is affected by a group delay deviation on a receiving device side, and the FM
It is an object of the present invention to provide an optical transmission device and an optical transmission device that can reduce the occurrence of distortion in a demodulated frequency-multiplexed multi-channel signal band.

[0006]

An optical transmitting apparatus according to the present invention comprises:
An FM modulator that collectively modulates the frequency of a multi-channel signal that has been frequency-multiplexed, a harmonic reducer that reduces a harmonic signal of an FM batch modulated signal that is obtained by frequency modulation, and a harmonic reducer And an optical modulator for optically transmitting the signal light by intensity-modulating the signal light with the FM batch modulation signal in which the wave signal is reduced.

According to the present invention, by reducing and transmitting the harmonic signal of the FM batch modulation signal, the frequency multiplexed multi-channel after the FM demodulation is affected by the group delay deviation on the receiving device side. An optical transmitter capable of reducing the occurrence of distortion in the signal band is obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical transmitter according to a first aspect of the present invention comprises: an FM modulator for collectively frequency modulating a frequency-multiplexed multi-channel signal; and an FM batch modulation obtained by frequency modulation. Harmonic reducer for reducing a harmonic signal included in a signal, and FM in which the harmonic signal is reduced by the harmonic reducer
And an optical modulator for optically transmitting the signal light by intensity-modulating the signal light with the collective modulation signal, and has an operation of reducing and transmitting a harmonic signal included in the FM collective modulation signal.

[0009] The optical transmitter according to the second aspect is the first aspect.
In the invention described in the above, the harmonic reducer has a flat group delay characteristic of the harmonic signal band, and the level of the harmonic signal of the FM batch modulation signal is reduced without being affected by the group delay deviation. It has the effect of being reduced and transmitted.

[0010] The optical transmission device according to claim 3 is an optical transmission device according to claim 1.
In the invention as described in (2), the harmonic reducer includes a low-pass filter, and the harmonic reducer including the low-pass filter reduces a harmonic signal included in the FM batch modulation signal. Has the effect of transmitting.

[0011] The optical transmission device according to claim 4 is the first invention.
In the invention described in the item (2), the harmonic reducer is constituted by a feedforward distortion canceller, and the harmonic reducer constituted by the feedforward distortion canceller is configured to convert the harmonic signal of the FM batch modulation signal It has the effect of reducing and transmitting.

The optical transmission device according to the fifth aspect is the first aspect of the invention.
In the invention described in 2 or 2, the harmonic reducer is configured by a feedback-type distortion canceller, and the harmonic reducer configured by the feedback-type distortion canceller reduces a harmonic signal included in the FM batch modulation signal. Has the effect of transmitting.

[0013] The optical transmission device according to the sixth aspect is the first aspect.
And an optical receiving device connected to the optical transmitting device via an optical fiber transmission line, wherein the optical receiving device photoelectrically converts the transmitted optical signal. An optical receiver for obtaining an FM batch modulation signal and an FM demodulator for FM demodulating the FM batch modulation signal obtained by photoelectric conversion to reproduce a frequency-multiplexed multi-channel signal. By reducing and transmitting the harmonic signal included in the FM batch modulation signal, the optical receiving apparatus is prevented from being affected by the group delay deviation and causing distortion in the frequency-multiplexed multi-channel signal band after the FM demodulation. It has the effect of being able to reduce.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that parts that perform the same or common functions as the above-described conventional optical transmission device will be described using the same reference numerals.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of an optical transmission device and an optical transmission device according to Embodiment 1 of the present invention. The optical transmitter 5 according to the present embodiment includes an FM modulator 1, a broadband amplifier 2, a harmonic reducer 3, and an optical modulator 4. The signal modulated by the optical transmitting device 5 is transmitted to the optical receiving device 9 via the optical fiber transmission line 6. The optical receiving device 9 includes an optical receiver 7 and an FM demodulator 8.

Next, the operation will be described. The frequency-multiplexed multi-channel signal input to the FM modulator 1 is frequency-modulated collectively. The obtained FM batch modulation signal is amplified by the broadband amplifier 2, and the harmonics are reduced by the harmonic reducer 3.
A harmonic signal included in the FM batch modulation signal generated by the modulator 1 and the broadband amplifier 2 is reduced.

The FM batch modulation signal from which the harmonic signal has been reduced is applied to the optical modulator 4 where the signal light is intensity-modulated and optically transmitted through the optical fiber transmission line 6. The transmitted optical signal is photoelectrically converted by the optical receiver 7 to obtain an FM batch modulation signal. The obtained FM batch modulation signal is transmitted to the FM demodulator 8
Thus, a multi-channel signal which is FM-demodulated and frequency-multiplexed is reproduced.

As described above, according to the present embodiment, the harmonic reducer 3 provided in the optical transmitter 5 converts the harmonic signal included in the FM batch conversion signal generated in the FM modulator 1 or the broadband amplifier 2 into a signal. It is possible to reduce the transmission.

For this reason, it is possible to reduce the distortion generated in the frequency-multiplexed multi-channel signal band after the FM demodulation due to the influence of the group delay deviation in the optical receiver 7 on the higher harmonic signal, and to obtain a high quality frequency. A multiplexed multi-channel signal can be transmitted.

(Embodiment 2) FIG. 2 is a block diagram showing the configuration of an optical transmission apparatus and an optical transmission apparatus according to Embodiment 2 of the present invention. This embodiment is similar to the first embodiment.
Low-pass filter 1 in place of the harmonic reducer 3
Except for using 0, the configuration is the same as that of the first embodiment.

Next, the operation will be described. The frequency-multiplexed multi-channel signal input to the FM modulator 1 is frequency-modulated collectively. The obtained FM batch modulation signal is amplified by the broadband amplifier 2, and the low-pass filter 10 reduces a harmonic signal included in the FM batch modulation signal generated by the FM modulator 1 or the broadband amplifier 2.

The FM batch modulated signal from which the harmonic signal has been reduced is applied to the optical modulator 4 where the signal light is intensity-modulated and optically transmitted through the optical fiber transmission line 6. The transmitted optical signal is photoelectrically converted by the optical receiver 7 to obtain an FM batch modulation signal. The obtained FM batch modulation signal is transmitted to the FM demodulator 8
To reproduce a frequency-multiplexed multi-channel signal.

FIG. 3 shows the frequency of the low-pass filter 10.
It is an amplitude characteristic figure. As shown in the figure, by providing the low-pass filter 10 with the characteristic of attenuating at twice or three times the frequency of the FM carrier frequency fc, it is possible to reduce the harmonic signal of the FM batch modulation signal. .

FIG. 4 shows a frequency-group delay characteristic diagram of the low-pass filter 10. As shown in the figure, the FM batch modulation signal including the harmonic signal passes through the low-pass filter 10 so that the group delay characteristic is flat up to the harmonic signal band so as not to be affected by the group delay deviation. Has become.

As described above, according to the present embodiment, the low-pass filter 10 provided in the optical transmitter 5 allows the F modulator 1 and the broadband amplifier 2 of the optical transmitter 5 to generate the F
Higher harmonic signals included in the M batch modulation signals can be reduced and transmitted.

For this reason, it is possible to reduce the distortion generated in the frequency-multiplexed multi-channel signal band after the FM demodulation due to the influence of the group delay deviation in the optical receiver 7 on the harmonic signal. A multiplexed multi-channel signal can be transmitted.

(Embodiment 3) FIG. 5 is a block diagram showing a configuration of an optical transmission apparatus and an optical transmission apparatus according to Embodiment 3 of the present invention. This embodiment is similar to the first embodiment.
Has the same configuration as that of the first embodiment except that a feedforward type distortion canceller 11 is used in place of the harmonic reducer 3 in.

Next, the operation will be described. The frequency-multiplexed multi-channel signal input to the FM modulator 1 is frequency-modulated collectively. The obtained FM batch modulation signal is amplified by the broadband amplifier 2, and the feedforward distortion canceller 11 reduces the harmonic signal of the FM batch modulation signal generated by the FM modulator 1 or the broadband amplifier 2.

The FM batch modulated signal from which the harmonic signal has been reduced is applied to the optical modulator 4, which modulates the intensity of the signal light and transmits the signal light via the optical fiber transmission line 6. The transmitted optical signal is photoelectrically converted by the optical receiver 7 to obtain an FM batch modulation signal. The obtained FM batch modulation signal is transmitted to the FM demodulator 8
To reproduce a frequency-multiplexed multi-channel signal.

The group delay characteristic of the feedforward type distortion canceller 11 is the same as that of the low-pass filter 1 shown in FIG.
Similarly to the characteristic of 0, the group delay characteristic is flat up to the harmonic signal band so that the FM batch modulation signal including the harmonic signal passes therethrough so as not to be affected by the group delay deviation.

As described above, according to the present embodiment, the FM batch modulation signal generated in the FM modulator 1 or the broadband amplifier 2 of the optical transmission device 5 by the feedforward distortion canceller 11 provided in the optical transmission device 5. Can be transmitted with reduced harmonic signals.

For this reason, it is possible to reduce the distortion generated in the frequency-multiplexed multi-channel signal band after the FM demodulation due to the influence of the group delay deviation in the optical receiver 7 on the harmonic signal. A multiplexed multi-channel signal can be transmitted.

(Embodiment 4) FIG. 6 is a block diagram showing a configuration of an optical transmission apparatus and an optical transmission apparatus according to Embodiment 4 of the present invention. This embodiment is similar to the first embodiment.
Has the same configuration as that of the first embodiment except that a feedback type distortion canceller 12 is used in place of the harmonic reducer 3 in.

Next, the operation will be described. The frequency-multiplexed multi-channel signal input to the FM modulator 1 is frequency-modulated collectively. The obtained FM batch modulation signal is amplified by the broadband amplifier 2, and the feedback type distortion canceller 12 reduces the harmonic signal of the FM batch modulation signal generated by the FM modulator 1 or the broadband amplifier 2.

The FM batch modulation signal from which the harmonic signal has been reduced is applied to the optical modulator 4 where the signal light is intensity-modulated and optically transmitted through the optical fiber transmission line 6. The transmitted optical signal is photoelectrically converted by the optical receiver 7 to obtain an FM batch modulation signal. The obtained FM batch modulation signal is transmitted to the FM demodulator 8
To reproduce a frequency-multiplexed multi-channel signal.

Also, a feedback type distortion canceller 1
The group delay characteristic of No. 2 is similar to the characteristic of the low-pass filter 10 shown in FIG. 4, because the FM batch modulation signal including the harmonic signal passes therethrough so that the harmonics are not affected by the group delay deviation. The group delay characteristics are flat up to the signal band.

As described above, according to the present embodiment, the feedback type distortion canceller 12 provided in the optical transmitter 5
Thereby, it is possible to reduce and transmit a harmonic signal included in the FM batch modulation signal generated in the FM modulator 1 or the broadband amplifier 2 of the optical transmitter 5.

For this reason, it is possible to reduce the distortion that occurs in the frequency-multiplexed multi-channel signal band after the FM demodulation due to the influence of the group delay deviation in the optical receiver 7 on the higher harmonic signal. A multiplexed multi-channel signal can be transmitted.

[0039]

According to the present invention, by reducing and transmitting the harmonic signal of the FM batch modulation signal on the optical transmitting device side, the optical receiving device side is affected by the group delay deviation and performs FM demodulation. Has the advantageous effect of reducing the occurrence of distortion in the frequency-multiplexed multi-channel signal band.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration of an optical transmission device and an optical transmission device according to a second embodiment of the present invention.

FIG. 3 is a frequency-amplitude characteristic diagram of the low-pass filter shown in FIG. 2;

FIG. 4 is a frequency-group delay characteristic diagram of the low-pass filter shown in FIG. 2;

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

FIG. 6 is a block diagram illustrating a configuration of an optical transmission device and an optical transmission device according to a fourth embodiment of the present invention.

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 FM modulator 2 Broadband amplifier 3 Harmonic reducer 4 Optical modulator 5 Optical transmitter 6 Optical fiber transmission line 7 Optical receiver 8 FM demodulator 9 Optical receiver 10 Low-pass filter 11 Feedforward distortion canceller 12 Feedback Type distortion canceller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/18 H04J 1/02

Claims (6)

[Claims] An FM modulator for collectively frequency-modulating a frequency-multiplexed multi-channel signal; a harmonic reducer for reducing a harmonic signal included in the FM-modulated signal obtained by frequency modulation; An optical transmitter, comprising: an optical modulator that intensity-modulates signal light with an FM batch modulation signal in which the harmonic signal has been reduced by the harmonic reducer and optically transmits the signal light. 2. The harmonic reducer according to claim 1, wherein the group delay characteristic of the harmonic signal band is set flat.
The optical transmission device as described in the above. 3. The optical transmitter according to claim 1, wherein the harmonic reducer comprises a low-pass filter. 4. The optical transmitter according to claim 1, wherein the harmonic reducer is constituted by a feedforward type distortion canceller. 5. The optical transmitter according to claim 1, wherein the harmonic reducer is configured by a feedback type distortion canceller. 6. An optical transmission device comprising: the optical transmission device according to claim 1; and an optical reception device connected to the optical transmission device via an optical fiber transmission line. The optical receiving device photoelectrically converts the transmitted optical signal to F
An optical transmission apparatus comprising: an optical receiver that obtains an M batch modulation signal; and an FM demodulator that reproduces a frequency-multiplexed multi-channel signal by FM demodulating the FM batch modulation signal obtained by performing the photoelectric conversion. .