JPH08154075A - Optical transmitter - Google Patents

Abstract

PURPOSE: To automatically compensate dispersion without depending on a transmission distance and to improve the flexibility of an optical transmitter by performing a control imparting delay for at least one optical wavelength so that the propagation delay time difference of the inter-optical waves due to dispersion may be zero. CONSTITUTION: The control signal generation means 13 of a dispersion compensation means 8 sweeps delay time within the range of the variable delay time of an optical delay means 5 by a control signal for a period when a detection means 12 detects the generation of the optical propagation delay time difference of wavelengths ν1 and ν0 When the fact that propagation delay time difference is zero is detected by this delay operation, the delay time of the means 5 is fixed. As a result, the propagation delay time difference between the optical wavelengths due to the wavelength dispersion generated because an optical digital signal 101 propagates a dispersible medium 200 is detected by the peak level difference of the signals detecting and amplifying the optical signal which enters the means 8. Because the delay time of the light of one optical wavelength is selectively controlled based on the detection result and a dispersion compensation is automatically performed, the original optical signal 101 becomes possible to be reproduced by the output stage of an optical coupler 6 without depending on the transmission distance.

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 for compensating the spread of an optical pulse signal due to wavelength dispersion in IM / DD (Direct Intensity Modulation) long distance optical digital transmission using a semiconductor laser diode. is there.

[0002]

2. Description of the Related Art IM using a semiconductor laser diode
In the / DD long-distance optical digital transmission device, the spread of the optical pulse signal due to wavelength dispersion causes a discrimination error between high level and low level of data at the time of reception, which is a great obstacle in constructing the system. The spread of the optical pulse signal due to the wavelength dispersion is such that the central wavelength of the signal light changes with time by modulating the semiconductor laser, the central wavelength of the signal light, and SMF (single mode fiber). It is caused by the mismatch of the zero dispersion wavelength of the dispersion medium.

An example of the configuration of a conventional IM / DD long-distance optical digital transmission device using a semiconductor laser diode is shown in FIG.
Shown in

In FIG. 5, a digital modulation signal 100
Thereby, the semiconductor laser diode 1 is directly intensity-modulated, and the optical digital signal 101 is emitted to the dispersion medium 200. Optical Digital Signal 10 Propagated in Dispersion Medium 200
The optical signal 1 is converted into a digital reception signal 102 by the optical-electrical conversion means 9 constituting the optical reception means 23, and the signal is reproduced.

[0005]

In the conventional IM / DD long-distance optical digital transmission apparatus, the transmission distance is limited due to the accumulation of the dispersion amount and the spread of the optical pulse signal due to the dispersion as the transmission path becomes longer. Was there. In order to overcome such a conventional problem, the dispersion value of the entire transmission line is canceled by canceling the chromatic dispersion generated in the SMF which is the transmission line with a device having an inverse dispersion characteristic, for example, a DCF (dispersion compensation fiber). A method of compensating for is also proposed. With this method, dispersion compensation can be performed by adjusting the dispersion amount having a negative dispersion characteristic with the length of the DCF with respect to the total dispersion amount of chromatic dispersion corresponding to the transmission distance of the SMF.

However, for example, in the optical transmission device for further expanding or branching the above-mentioned dispersion-compensated transmission path, the transmission path distance from the branch destination to each signal reproducing means is different. Since it becomes necessary to adjust the DCF and compensate for the dispersion, flexibility as an optical transmission device becomes a problem.

Furthermore, as the transmission path becomes longer, the DCF length required for compensating for dispersion becomes longer, resulting in an increase in size of the optical transmission device. Further, under the present circumstances, there is a problem that the cost of DCF is high.

In consideration of such a problem in the conventional IM / DD long-distance optical digital transmission device, the present invention positively utilizes chromatic dispersion, controls the delay time of the central wavelength of light, and automatically disperses it. An object of the present invention is to provide an optical transmission device which can increase flexibility of the optical transmission device and facilitate expansion of a transmission line by performing compensation.

[0009]

In order to solve the above-mentioned problems, the present invention is directed to a semiconductor laser diode biased to a threshold current or more and directly intensity-modulated by a digital modulation signal, and light emitted from the semiconductor laser diode. Corresponding to a high level of the digital modulation signal from one optical output of the optical branch output, a first optical branching device for branching the optical digital signal propagating through the dispersion medium, for example, an SMF in which the digital signal propagates A first optical filter for selecting an optical wavelength to be used, a second optical filter for selecting an optical wavelength corresponding to a low level of a digital modulation signal from another optical output, a first optical filter or a second optical filter.
Optical delay means having a control terminal for varying the delay time for at least one output light of the output light of the optical filter,
An optical coupler that multiplexes the output light of the first optical filter or the second optical filter to which the optical delay unit is not connected and the output light of the optical delay unit, and the second optical branch that splits the output light of the optical coupler. And at least one output light split by the second optical splitter, and the propagation delay due to the dispersion of the output light of the first optical filter and the output light of the second optical filter from the detection output. An optical transmission device is configured with a dispersion compensating unit that detects a time difference and controls the delay time of the optical delay unit based on the detection result.

[0010]

According to the present invention, the optical signal propagating through the dispersion medium, which is the transmission line, is separated into the wavelengths of light corresponding to the high level and the low level of the digital modulation signal by the above-mentioned structure, and the wavelengths between the optical wavelengths due to the dispersion are separated. By controlling the delay of at least one of the optical wavelengths so that the propagation delay time difference becomes zero, the dispersion is automatically compensated without depending on the transmission distance, so that the flexibility of the optical transmission device can be improved. it can.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

FIG. 1 is a block diagram of an optical transmission device according to a first embodiment of the present invention. In the figure, 1 is a semiconductor laser diode, 2 is a first optical branching device, 3 is a first optical filter for selecting a wavelength ν ₁ , 4 is a second optical filter for selecting a wavelength ν ₀ , and 5 is a control. Optical delay means for varying the delay time by a signal, 6 an optical coupler, 7 a second optical branching device, 8 dispersion compensation means, 9 optical-electrical conversion means, 10 detection means,
Reference numeral 11 is amplification means, 12 is detection means, and 13 is control signal generation means. Further, 100 is a digital modulation signal, 10
1 is an optical digital signal, and 200 is a dispersion medium.

FIG. 2 is an explanatory diagram of the operation of the optical transmission device of the first embodiment. In the same figure, FIG. 2-A shows a digital modulation signal 100 for modulating the semiconductor laser diode 1, and FIGS. 2-B, C, and D are optical signal outputs of the semiconductor laser diode 1, the dispersion medium 200, and the optical coupler 6, respectively. The light wavelength and the light intensity level in the step are shown.

The operation of the first embodiment will be described below with reference to FIGS. 1 and 2.

The semiconductor laser diode 1 is biased to a threshold current or more and directly intensity-modulated by the digital modulation signal 100, whereby the semiconductor laser diode 1 is operated as a light source of FSK (frequency shift keying). As shown in FIG. 2-B, in the optical spectrum distribution of the optical signal emitted from the semiconductor laser diode 1, the central wavelength ν ₁ when the digital modulated signal 100 is at high level and the central wavelength ν ₀ when the digital modulated signal 100 is at low level. Appears. Further, continuous sidebands are generated for each center wavelength. The center wavelengths ν ₁ and ν ₀ have light intensity levels P ₁ and P ₀ , respectively, due to the AM component at the time of direct intensity modulation. Therefore, at the time of modulation, the digital modulation signal 100
According to the above logic, either the light having the central wavelength ν ₁ and the light intensity level P ₁ or the light having the central wavelength ν ₀ and the light intensity level P ₀ is emitted from the semiconductor laser diode 1. .

The optical digital signal 101 emitted from the semiconductor laser diode 1 enters the dispersion medium 200 and propagates. At the output stage of the dispersive medium 200, as shown in FIG. 2C, a propagation delay time difference τ due to chromatic dispersion occurs between the lights of wavelength ν ₁ and wavelength ν ₀ . Due to this propagation delay time difference τ, the light intensity level at the output stage of the dispersion medium 200 is the light intensity level P corresponding to the wavelength ν ₁ and the wavelength ν _0.
It becomes the sum of the electric powers of ₁ and P ₀ , the state of excessive light (P ₁ + P ₀ ),
The state where the light is turned off appears. As described in the conventional example, it is difficult to directly detect the light intensity level and reproduce the original digital modulated signal 100.

The optical signal propagating through the dispersion medium 200 is
The light is input to the first optical branching device 2 and branched. The wavelengths of the branched output lights are selected by the first optical filter 3 that selects the light of wavelength ν ₁ or the second optical filter 4 that selects the light of wavelength ν ₀ . Of these, the optical signal of wavelength ν ₀ wavelength-selected by the optical filter 4 is delayed by the optical delay means 5 for the delay time based on the control signal of the control signal generation means 12, and then the optical filter is performed by the optical coupler 6. It is multiplexed with the optical signal of wavelength ν ₁ whose wavelength is selected in 3. As shown in FIG. 2-D, only when the light having the wavelength ν ₀ is delay-compensated by the optical delay means 5 by the propagation delay time difference τ, the output stage of the semiconductor laser diode 1 is output at the output stage of the optical coupler 6. The optical digital signal 101 can be reproduced. Further, when the light of the wavelength ν ₀ is delayed by a delay time different from the propagation delay time difference τ, the light intensity level of the output stage of the optical coupler 6 may be excessive or the light may not be emitted due to the reason described above. The state of being turned off appears.

The output light from the optical coupler 6 is split again by the second optical splitter 7. It should be noted that one of the branched output lights is emitted to a different dispersion medium and propagates. The other branched output light is incident on the dispersion compensating means 8 composed of the optical-electrical converting means 9, the detecting means 10, the amplifying means 11, the detecting means 12, and the control signal generating means 13. The operation of the dispersion compensator 8 will be described below.

The optical signal incident on the dispersion compensating means 8 is directly detected by an optical-electrical converting means 9 such as a pin photodiode and converted into an electric signal, and then the detecting means 1 is detected.
The envelope is detected by 0 and amplified by the amplifying means 11. The detection means 12 detects the peak level of the output signal of the amplification means 11, compares it with the reference level, and then outputs the detection result to the control signal generation means 13.

Here, the reference level is, for example, the peak level of the output signal of the amplifying means 11 when an optical signal having a signal amplitude of the light intensity level difference P ₁ -P ₀ (P ₁ > P ₀ ) is directly detected by light. The difference. First, in the output stage of the optical coupler 6, when there is a propagation delay time difference between the light having the wavelength ν _{1 and} the light having the wavelength ν ₀ , as described above, the light intensity level is excessive (P ₁ + P The state of ₀ ) or the state where the light is turned off appears, and the difference in the light intensity levels is (P ₁ + P ₀ ) at the maximum. The peak level difference of the output signal of the amplifying means 11 when this optical signal is directly detected by light is always larger than the reference level.
Next, when there is no propagation delay time difference between the light of wavelength ν _{1 and} the light of wavelength ν ₀ , the peak level difference of the output signal of the amplification means 11 becomes equal to the reference level.

The control signal generation means 13 detects the occurrence of a propagation delay time difference between the light of wavelength ν _{1 and} the light of wavelength ν _{0 by} the detection means 12 during the variable delay time of the optical delay means 5 by the control signal. Sweep the delay time within the range. When the delay operation detects that the difference in propagation delay time is zero, the delay time of the optical delay means 5 is fixed.

By the above operation, the optical digital signal 10
The propagation delay time difference between optical wavelengths caused by chromatic dispersion when 1 propagates through the dispersion medium 200 is detected by the peak level difference of the signal obtained by photodetecting and amplifying the optical signal incident on the dispersion compensating means 8. Dispersion compensation is automatically performed by selectively controlling the delay time of the light of one optical wavelength based on the above. Therefore, the original optical digital signal 101 is output at the output stage of the optical coupler 6 without depending on the transmission distance. Can be played. With the configuration in which the branched output light of the optical coupler 6, that is, the output light of the optical splitter 7 is emitted to different dispersion media,
It can be used as a dispersion compensation optical repeater. Further, the original digital modulated signal 1 has a configuration in which at least one of the branched output lights of the optical branching device 7 is received by the optical receiving means.
00 can be used as a dispersion compensating light receiving means.

The optical delay means 5 can be composed of, for example, an optical waveguide of lithium niobate, and by utilizing its electro-optic effect, acousto-optic effect, or magneto-optic effect under the control of the outside, the propagation characteristics of light. Can be changed.

By the way, in the optical transmission apparatus of the first embodiment, the presence or absence of the propagation delay time difference between the light of wavelength ν _{1 and} the light of wavelength ν _{0 in} the optical coupler 6 is detected by the signal input to the detection means 12. This is done by comparing the peak level difference of and the reference level. In this case, the S / N ratio required for detection is
A value obtained by subtracting the light intensity level difference (P ₁ −P ₀ ) when the propagation delay time difference is zero from the maximum light intensity level difference (P ₁ + P ₀ ) when the propagation delay time difference occurs, that is, 2P. It becomes ₀ . Further, in order to improve the S / N ratio for detection, it is necessary that the light intensity level P ₁ be large and that P ₁ and P ₀ be equal. However, since the semiconductor laser diode 1 is directly intensity-modulated,
The light intensity levels P ₁ and P ₀ are different. Therefore, with the configuration of the first embodiment, it is difficult to improve the S / N ratio required for detection.

Therefore, the second invention for improving the S / N ratio necessary for detection will be described below with reference to FIG.

The optical transmission system of the second embodiment is the same as the semiconductor laser diode 1 and the dispersion medium 200 of the first embodiment.
Connect constituted the light intensity constant means for equalizing the light intensity level of the light intensity level P ₀ of the light intensity level P ₁ and the light wavelength [nu ₀ of the optical wavelength [nu ₁ between.

In the optical transmission device of the present configuration, by making the light intensity levels of P ₁ and P ₀ equal, the S / N ratio required for detecting the presence / absence of the propagation delay difference in the detecting means 12 is improved. be able to.

The optical output fixing means can be easily realized by, for example, a method of using an optical fiber amplifier and utilizing its gain tilt characteristic, or a method of using an optical filter and utilizing its filter characteristic.

Next, an optical transmission device having a dispersion compensating means independent of the light intensity levels P ₁ and P ₀ will be described.

FIG. 3 is a block diagram of an optical transmission device according to a third embodiment of the present invention. In FIG. 3, 14 is an optical detection means, 22
Is a branching means, 15 is a first filter for selecting the frequency f ₁ , 16 is a second filter for selecting the frequency f ₀ , 17
Is a first detection means, 18 is a second detection means, and 19 is a detection means. Further, in the figure, the constituent elements having the same operations as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The operation of the third embodiment will be described below with reference to FIG.

The semiconductor laser diode 1 is biased above the threshold current and directly intensity-modulated by the digital modulation signal 100. The optical digital signal 101 emitted from the semiconductor laser diode 1 is a dispersion medium 200.
To the first optical branching device 2 and is then branched. The wavelengths of the branched output lights are selected by the first optical filter 3 for selecting the light having the wavelength ν ₁ or the second optical filter 4 for selecting the light having the wavelength ν ₀ . Of these, the light of wavelength ν ₀ wavelength-selected by the optical filter 4 is
After being delayed by the optical delay means 5 for a delay time based on the control signal of the control signal generation means 12, the optical coupler 6 multiplexes the optical signal with the wavelength ν ₁ selected by the optical filter 3.
The output light of the optical coupler 6 is split again by the second optical splitter 7. One of the branched output lights is emitted to a different dispersion medium and propagates. The other branched output light is the optical detection means 14, the amplification means 11, the branching means 22, the first filter 15, the second optical filter 16, the first detection means 17,
It is incident on the dispersion compensating means 8 including the second detecting means 18, the detecting means 19 and the control signal generating means 13. The operation of the dispersion compensator 8 will be described below.

The light having the wavelength ν _{1 and} the light having the wavelength ν ₀ that have entered the dispersion compensating means 8 are heterodyne-detected by the local oscillating light having the oscillation wavelength ν by the photodetecting means 14, and each of them has a difference frequency from the oscillation wavelength ν. IF (intermediate frequency) of f ₁ and f ₀ determined by
Converted to electrical signals in the band. This IF band electrical signal is
It is amplified by the amplification means 11 and branched by the branching means 22. The branched outputs are respectively the filter 15 for selecting the frequency f ₁ and the filter 16 for selecting the frequency f _0.
Frequency is selected by. The signal of the frequency f ₁ selected by the filter 15 is envelope-detected by the detection means 17. Similarly, the signal of the frequency f ₀ selected by the filter 16 is envelope-detected by the detection means 18. Detection means 17
And the output signal of the detection means 18 is input to the detection means 19 and the exclusive OR of the detection means 19 is output.

First, in the output stage of the optical coupler 6, when the propagation delay time difference between the light of wavelength ν _{1 and} the light of wavelength ν ₀ is zero, it corresponds to the high level or low level of the digital modulation signal 100. There is only light of either wavelength ν ₁ or wavelength ν ₀ . Therefore, the waveforms obtained by envelope detection of the signals of frequency f ₁ and f ₀ which are the outputs of the photodetection output 14 are differential waveforms, and the detection means 19 outputs the exclusive OR of the both waveforms. The detection result is always low level.

Next, when the propagation delay time difference in the light of the wavelength [nu ₁ of light and the wavelength [nu ₀ has occurred, the situation in which the light of wavelength [nu ₁ and the wavelength [nu ₀ is absent or present simultaneously occurs. In this case, the relationship between the signal of frequency f _{1 and} the signal of f ₀ which is the photodetection output of the photodetection means 14 is similar. Therefore, a high level appears in the detection result of the detection means 19 which outputs the exclusive OR of the waveforms of the signals of the frequency f _{1 and} the signal f ₀ which are envelope-detected.

When the detecting means 12 detects the occurrence of the propagation delay time difference between the light having the wavelength ν _{1 and} the light having the wavelength ν ₀ , the control signal generating means 13 is within the range of the variable delay time of the optical delay means 5 by the control signal. Sweep the delay time with. When the delay operation detects that the difference in propagation delay time is zero, the delay time of the optical delay means 5 is fixed.

By the above operation, the optical digital signal 10
1 propagates through the dispersion medium 200, a propagation delay time difference between optical wavelengths due to wavelength dispersion is detected by the optical detection means 14 at a frequency in the IF band, and one optical wavelength is selectively selected based on the detection result. Since the dispersion compensation is automatically performed by controlling the delay time of, the original optical digital signal 101 can be regenerated at the output stage of the optical coupler 6 without depending on the transmission distance. With this operation, the above-described embodiment detects the presence of the light of wavelength ν _{1 and} the light of wavelength ν ₀ , and thereby compensates the chromatic dispersion regardless of the light intensity levels P ₁ and P _0. It can be used as a means or a dispersion compensation light receiving means.

By the way, in the control method of the optical delay element 5 in the optical transmission apparatus of the third embodiment, when the detecting means 19 detects the occurrence of the dispersion delay time difference, the optical delay element 5 is kept until the dispersion delay becomes zero. The delay time is swept within the variable delay time of. Therefore, when the dispersion characteristic of the dispersion medium 200 changes, the control method of the dispersion compensating means 8
Since it takes time to reestablish delay compensation,
Continuous operation of optical transmission equipment becomes difficult.

A fourth invention for realizing continuous operation of the optical transmission device will be described below with reference to FIG.

In the optical transmission apparatus of the fourth embodiment, a pulse width detecting means for detecting the pulse width of the output signal of the detecting means 19 is connected between the detecting means 19 and the control signal generating means 13 in the third embodiment. Composed.

In the optical coupler 6, the light of wavelength ν ₁ and the wavelength ν ₀
Light propagation delay time difference τ occurs, and this propagation delay time difference τ is the clock cycle τ _CL of the optical digital signal 101.
When it is shorter, the exclusive logical sum of the waveforms detected by the envelope detecting means 17 and the envelope detecting means 18 is always an electric pulse signal having a pulse width of τ. This pulse width is detected by the pulse width detecting means, and based on the detection result, the control signal generating means 13 constitutes a feedback loop for controlling the delay time of the optical delay means 5 so that the pulse width becomes infinitely small. By the above operation, even when the dispersion characteristic of the dispersion medium 200 changes, the dispersion can be constantly compensated, and thus the continuous operation of the transmission device can be realized.

FIG. 4 is a block diagram of an optical transmission device according to a fifth embodiment of the present invention. In the figure, 20 is a signal reproducing means, 21 is a dispersion compensating means, and 22 is a branching means. Further, in the figure, the constituent elements having the same operations as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The operation of the fifth embodiment will be described below with reference to FIG.

The semiconductor laser diode 1 is biased above the threshold current and directly intensity-modulated by the digital modulation signal 100. The optical digital signal 101 emitted from the semiconductor laser diode 1 is a dispersion medium 200.
To the first optical branching device 2 and is then branched. The wavelengths of the branched output lights are selected by the first optical filter 3 that selects the light of wavelength ν ₁ or the second optical filter 4 that selects the light of wavelength ν ₀ . Of these, the light having the wavelength ν ₀ selected by the optical filter 4 is delayed by the optical delay means 5 for a delay time based on the control signal of the control signal generation means 12, and then the optical filter 3 is used by the optical coupler 6. And is multiplexed with the optical signal of wavelength ν ₁ selected by. The output light from the optical coupler 6 is used as an optical-electrical converting means 9 and a branching means 2.
2, signal reproduction means 20, detection means 10, amplification means 11,
The light is incident on the dispersion compensating means 21 including the detecting means 12 and the control signal generating means 13. The operation of the dispersion compensating means 21 will be described below.

The optical signal incident on the dispersion compensating means 21 is converted into an electric signal by the optical-electrical converting means 9, and the branching means 22 is provided.
Is branched at.

First, one output signal of the branching means 22 is
Envelope detection is performed by the detection means 10 and amplified by the amplification means 11. The detection means 12 detects the peak level of the output of the amplification means 11, compares it with the reference level, and then outputs the detection result to the control signal generation means 13. When the detecting means 12 detects the difference in propagation delay time between the light having the wavelength ν _{1 and} the light having the wavelength ν ₀ , the control signal generating means 13 sweeps the delay time within the range of the variable delay time of the optical delay means 5 by the control signal. To do. When the delay operation detects that the difference in propagation delay time is zero, the delay time of the optical delay means 5 is fixed. Next, the other output signal of the branching means 22 is reproduced by the signal reproducing means 20 and the digital reception signal 102 is output. When the dispersion compensation means 21 delay-compensates the propagation delay time difference, the digital reception signal 102 output from the signal reproduction means 20.
Is a reproduction output of a digital modulation signal 100 that modulates the semiconductor laser diode 1.

With the above-described configuration, in this embodiment, the propagation delay time difference between the optical wavelengths due to the chromatic dispersion generated when the optical digital signal 101 propagates through the dispersion medium 200 is detected in the optical signal incident on the dispersion compensating means 21. The output is detected from one of the branched outputs, and dispersion compensation is automatically performed by selectively controlling the delay time of the light of one optical wavelength based on the detection result, and the signal from the other branched output is used. By reproducing the signal, the original digital modulated signal 100 can be used as a dispersion compensating optical receiving means for reproducing the original digital modulated signal 100 at the output stage of the signal reproducing means 20 without depending on the transmission distance.

[0048]

As is apparent from the above description,
In the present invention, an optical signal propagating in a dispersion medium which is a transmission path is separated into wavelengths of light corresponding to high level and low level of a digital modulation signal, and a propagation delay time difference between optical wavelengths due to dispersion is zero. By controlling so that at least one of the optical wavelengths is delayed so that dispersion is automatically compensated without depending on the transmission distance, the flexibility of the optical transmission device can be improved.

[Brief description of drawings]

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

FIG. 2 is an operation explanatory diagram of the optical transmission device according to the first embodiment.

FIG. 3 is a configuration diagram of dispersion compensating means according to a third embodiment of the present invention.

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

FIG. 5 shows a conventional optical transmission device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser diode 2 1st optical splitter 3 1st optical filter 4 2nd optical filter 5 Optical delay means 6 Optical coupler 7 2nd optical splitter 8 Dispersion compensation means 9 Optical-electrical conversion means 10 Detection Means 11 Amplifying means 12 Detecting means 13 Control signal generating means 14 Optical detecting means 15 First filter 16 Second filter 17 First detecting means 18 Second detecting means 19 Detecting means 20 Signal reproducing means 21 Dispersion compensating means 22 Splitting means 23 Optical receiving means 100 Digital modulation signal 101 Optical digital modulation signal 102 Digital reception signal 103 Optical digital reproduction signal 200 Dispersion medium

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location H04B 10/142 10/04 10/06 (72) Inventor Susumu Morikura 1006 Kadoma, Kadoma, Osaka Prefecture Address: Matsushita Electric Industrial Co., Ltd. (72) Inventor, Katsuyuki Fujito 1006, Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. A semiconductor laser diode biased to a threshold current or more and directly intensity-modulated by a digital modulation signal, a dispersion medium in which an optical digital signal emitted from the semiconductor laser diode propagates, and a dispersion medium which propagates in the dispersion medium. A first optical branching device that branches the optical digital signal, and a first optical branching device that selects an optical wavelength corresponding to a high level of the digital modulation signal from one optical output of the first optical branching device.
Optical filter, a second optical filter for selecting an optical wavelength corresponding to a low level of the digital modulation signal from another optical output of the first optical branching device, the first optical filter or the first optical filter Optical delay means having a control terminal for varying the delay time of at least one of the output lights of the second optical filter; the first optical filter or the second optical filter to which the optical delay means is not connected. An optical coupler that multiplexes the output light of the optical filter and the output light of the optical delay unit, a second optical splitter that splits the output light of the optical coupler, and a split by the second optical splitter. At least one output light of the output lights detected is detected, and a propagation delay time difference due to dispersion of the output light of the first optical filter and the output light of the second optical filter is detected, and based on the detection result. The optical delay means The optical transmission apparatus characterized by comprising a dispersion compensating means for sending a control signal to the control terminal. 2. The dispersion compensating means includes an opto-electric converting means for directly detecting incident light, a detecting means for detecting a signal component from an output of the opto-electric converting means, and an output signal of the detecting means. Amplifying means for amplifying, detecting means for detecting the peak level of the output signal of the amplifying means, and control signal generating means for sending a control signal to the control terminal of the optical delay means based on the detection result of the detecting means. The optical transmission device according to claim 1, further comprising: 3. A light intensity level of a light wavelength corresponding to a high level of a digital modulation signal and a light intensity of a light wavelength corresponding to a low level of the digital modulation signal, which are connected between the semiconductor laser diode and a dispersion medium. 3. The optical transmission device according to claim 2, further comprising a light intensity fixing unit that equalizes the levels. 4. The dispersion compensating means, an optical detecting means for performing optical heterodyne detection of incident light by local oscillation light and converting it into an IF signal, an amplifying means for amplifying the IF signal output from the detecting means, and the amplifying means. Branching means for branching the output signal of the means, a first filter for selecting a frequency corresponding to a high level of the digital modulation signal from one output signal of the branching means, and another output signal of the branching means Second selection of the frequency corresponding to the low level of the digital modulation signal
Filter, first detection means for envelope detection of the output of the first filter, second detection means for envelope detection of the output of the second filter, and output of the first detection means And detection means for outputting an exclusive OR of the outputs of the second detection means, and control signal generation means for sending a control signal to the control terminal of the optical delay means based on the detection result of the detection means. The optical transmission device according to claim 1, wherein: 5. Between the detecting means and the control signal generating means,
The optical transmission device according to claim 4, further comprising pulse width detection means for detecting a pulse width of the output signal of the detection means. 6. A semiconductor laser diode biased to a threshold current or more and directly intensity-modulated by a digital modulation signal, a dispersion medium in which an optical digital signal emitted from the semiconductor laser diode propagates, and a dispersion medium which propagates in the dispersion medium. A first optical branching device that branches the optical digital signal, and a first optical branching device that selects an optical wavelength corresponding to a high level of the digital modulation signal from one optical output of the first optical branching device.
Optical filter, a second optical filter for selecting an optical wavelength corresponding to a low level of the digital modulation signal from another optical output of the first optical branching device, the first optical filter or the first optical filter Optical delay means having a control terminal for varying the delay time of at least one of the output lights of the second optical filter; the first optical filter or the second optical filter to which the optical delay means is not connected. An optical coupler that multiplexes the output light of the optical filter and the output light of the optical delay unit, and the first optical filter that detects the output light of the optical coupler and branches the detected output from one output signal. Of the output light of the second optical filter and the propagation delay time difference due to the dispersion of the output light of the second optical filter, and based on the detection result, sends a control signal to the control terminal of the optical delay means and the other output of the detection output. An optical transmission apparatus comprising: a dispersion compensating means having both a function of reproducing a digital signal from a force signal and outputting the digital signal. 7. The dispersion compensating means includes an opto-electric converting means for directly detecting incident light, a branching means for branching an output of the opto-electrical converting means, and an electric signal from one output signal of the branching means. A signal reproducing means for reproducing and outputting a digital signal, a detecting means for detecting another output signal of the branching means, an amplifying means for amplifying the output signal of the detecting means, and a peak level of the output signal of the amplifying means. 7. The optical transmission device according to claim 6, further comprising: a detection unit for detecting, and a control signal generation unit for transmitting a control signal to a control terminal of the optical delay unit based on a detection result of the detection unit. 8. The dispersion compensating means, an optical detecting means for performing optical heterodyne detection of the incident light by local oscillation light and converting it into an IF signal, an amplifying means for amplifying the IF signal output from the detecting means, and the amplifying means. Branching means for branching the output signal of the means, signal playback means for playing back and outputting an electric digital signal from at least one output signal of the branching means, and high level of a digital modulation signal from at least one output signal of the branching means A first filter for selecting a frequency corresponding to, a second filter for selecting a frequency corresponding to a low level of the digital modulation signal from at least one output signal of the branching means, and an output of the first filter A first detecting means for performing envelope detection on the output, a second detecting means for performing envelope detection on the output of the second filter, and the first Wave detecting means and detecting means for detecting the output of the second detecting means, and control means for transmitting a control signal to the control terminal of the optical delay means based on the detection result of the detecting means. The optical transmission device according to claim 6.