JP2005110091A - Optical transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission device enabling an optical transmission inhibiting a waveform distortion in the case of a reception by a simple constitution even when a general light source at a low cost having a modulation-frequency dependency is frequency-modulated without using an optical phase modulator. <P>SOLUTION: An information-signal control section 1001 controls a deviation depending upon a modulation frequency so as to suppress the deviation regarding the phase of the optical-frequency fluctuation component of an optical signal from a light source 1002. A bias tee 1003 adds the modulating current of an output from the control section 1001 to a bias current, and the light source 1002 carries out an optical-frequency modulation by the modulation signal of an output from the bias tee 1003. An optical transmission section 2000 transmits the optical signal from an optical transmission section 1000, and an optical-phase/intensity conversion section 3001 makes the optical signal delayed at 1 bit interfere and converts the optical signal into an intensity optical signal to the optical signal from the optical transmission section 2000. An optical electric conversion section 3002 converts the output optical signal of the conversion section 3001 into an electric signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical transmission apparatus that transmits an optical signal subjected to optical phase modulation, that is, optical frequency modulation.

  FIG. 4 is a block diagram illustrating a configuration of an optical transmission apparatus that transmits an optical signal subjected to optical phase modulation by an optical phase modulator. Hereinafter, a conventional optical transmission apparatus will be described with reference to FIG.

  In FIG. 4, the conventional optical transmission apparatus includes a light source 1002, a bias tee 1003, an optical phase modulator 1004, an optical transmission unit 2000, an optical phase / intensity conversion unit 3001, and a photoelectric conversion unit 3002. The light source 1002, the bias tee 1003, and the optical phase modulator 1004 constitute an optical transmitter 1000, and the optical phase / intensity converter 3001 and the photoelectric converter 3002 constitute an optical receiver 3000.

In the optical transmission apparatus configured as described above, the light source 1002 outputs continuous light, the bias tee 1003 outputs a modulation signal by adding a DC bias and an information signal, and the optical phase modulator 1004 has a bias. Optical phase modulation is performed on the continuous light output from the light source 1002 using the modulation signal output from the tee 1003, and the optical phase modulation signal is output to the optical transmission unit 2000. The optical phase / intensity conversion unit 3001 is composed of, for example, a Mach-Zehnder interferometer, converts an optical phase variation component of the optical signal transmitted by the optical transmission unit 2000 into a change in optical intensity, and the photoelectric conversion unit 3002 An information signal is output by converting the light intensity signal output from the intensity converter 3001 into an electrical signal (see, for example, Patent Document 1).
1998 IEICE Technical Report, PS-98-8, (1998)

  However, in the conventional optical transmission apparatus described above, when an optical phase modulator is used, there is a problem that the cost of the optical transmission apparatus is increased and it is difficult to control the polarization and the like. On the other hand, in order to solve this problem, if a light source is subjected to frequency modulation without using an optical phase modulator, a general light source has a modulation frequency dependency on the phase of the optical frequency fluctuation component. There arises a new problem that the output waveform is distorted (for example, in the case of a modulation frequency of 300 Mbps, see FIG. 5).

  Therefore, the object of the present invention is to use a simple configuration and a waveform at the time of reception even when a low-cost general light source having modulation frequency dependency is frequency-modulated without using an optical phase modulator. An object of the present invention is to provide an optical transmission device that enables transmission with reduced distortion.

  According to a first aspect of the present invention, an information signal control unit that inputs an information signal and controls the frequency dependence of the phase to a predetermined characteristic, and a signal output from the information signal control unit, based on a predetermined encoding method, A light source that outputs an optical signal whose frequency is modulated, an optical transmission unit that transmits an optical signal output from the light source, and an optical phase variation component of the optical signal output from the optical transmission unit is converted into an optical intensity variation component, An optical phase / intensity conversion unit for outputting, and a photoelectric conversion unit for converting an output optical signal of the optical phase / intensity conversion unit into an electrical signal.

  A second invention is an invention subordinate to the first invention, wherein the information signal control unit sets a deviation depending on the modulation frequency to a predetermined frequency with respect to the phase of the optical frequency fluctuation component of the optical signal output from the light source. A predetermined characteristic is controlled so as to suppress in a band.

  A third invention is an invention subordinate to the first invention, wherein the information signal control unit has a predetermined frequency band for the modulation frequency dependence of the phase of the optical frequency fluctuation component of the optical signal output from the light source. The predetermined characteristic is controlled so that the reverse characteristic is obtained in step.

  A fourth invention is an invention subordinate to the second or third invention, wherein the predetermined frequency band is substantially equal to an occupied band of a signal input to the light source.

  The fifth invention is an invention dependent on the second or third invention, wherein the predetermined frequency band includes the frequency of the inflection point in the modulation frequency dependency of the optical frequency fluctuation amount of the light source. .

  The sixth invention is an invention subordinate to the fifth invention, and the frequency of the inflection point in the modulation frequency dependency of the optical frequency fluctuation amount of the light source is determined by the dominant factor of the optical frequency fluctuation phenomenon from the thermal effect to the carrier. The frequency is substantially the same as the frequency that changes due to the density fluctuation effect.

  A seventh invention is an invention subordinate to the first invention, wherein the information signal control unit is an electric filter.

  The eighth invention is an invention subordinate to the seventh invention, wherein the information signal control unit is an electrical filter that can be created by connecting LCR circuits in parallel.

  A ninth invention is an invention dependent on the seventh invention, wherein the information signal control unit is a band-pass filter.

  A tenth invention is an invention subordinate to the seventh invention, wherein the information signal control unit is a low-pass filter.

  An eleventh invention is an invention dependent on the first invention, wherein the information signal control unit is an electric amplifier.

  A twelfth invention is an invention subordinate to the first invention, wherein the light source is a semiconductor laser.

  A thirteenth invention is an invention subordinate to the first invention, wherein the optical phase / intensity conversion unit is a Mach-Zehnder interferometer.

  A fourteenth invention is an invention subordinate to the first invention, and the predetermined code system is an RZ (Return Zero) code.

  According to a fifteenth aspect of the present invention, there is provided an information signal control unit that inputs an electric signal and controls the frequency dependence of the phase to a predetermined characteristic, and a signal output from the information signal control unit based on a predetermined encoding method. A light source that outputs an optical signal whose frequency is modulated.

  According to a sixteenth aspect of the present invention, there is provided an information signal control unit that inputs an electric signal and controls the frequency dependence of the level to a predetermined characteristic, and a signal output from the information signal control unit based on a predetermined encoding method. A light source that outputs an optical signal whose frequency is modulated, an optical transmission unit that transmits an optical signal output from the light source, and an optical phase variation component of the optical signal output from the optical transmission unit is converted into an optical intensity variation component, An optical phase / intensity conversion unit for outputting, and a photoelectric conversion unit for converting an output optical signal of the optical phase / intensity conversion unit into an electrical signal.

  According to a seventeenth aspect of the present invention, an information signal control unit that inputs an electric signal and controls the frequency dependency of the level and phase to a predetermined characteristic, and a signal output from the information signal control unit is based on a predetermined encoding method. A light source that outputs an optical signal whose optical frequency is modulated, an optical transmission unit that transmits the optical signal output from the light source, and an optical phase variation component of the optical signal output from the optical transmission unit that is converted into an optical intensity variation component And an optical phase / intensity conversion unit for outputting, and a photoelectric conversion unit for converting the output optical signal of the optical phase / intensity conversion unit into an electrical signal.

  According to the optical transmission device of the present invention, even when a low-cost general light source having a modulation frequency dependency is frequency-modulated without using an optical phase modulator, a simple configuration can be used for reception. Optical transmission with suppressed waveform distortion becomes possible.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the optical transmission apparatus according to Embodiment 1 of the present invention. In FIG. 1, the optical transmission apparatus of the present embodiment includes an information signal control unit 1001, a light source 1002, a bias tee 1003, an optical transmission unit 2000, an optical phase / intensity conversion unit 3001, and a photoelectric conversion unit 3002. The optical signal transmission unit 1000 is configured by the information signal control unit 1001, the light source 1002, and the bias tee 1003, and the optical reception unit 3000 is configured by the optical phase / intensity conversion unit 3001 and the photoelectric conversion unit 3002. Hereinafter, the operation of the optical transmission apparatus will be described with reference to FIG.

  The information signal control unit 1001 controls the phase depending on the modulation frequency of the information signal to be transmitted. Specifically, when the modulation frequency dependence of the phase of the optical frequency fluctuation component of the optical signal output from the semiconductor laser, which is a general light source 1002, is as shown in FIG. A deviation depending on the modulation frequency with respect to the phase of the optical frequency variation component of the optical signal output from the optical transmission unit 1000 by the information signal control unit having the phase opposite to the dependency, as shown in FIG. Repress. The bias tee 1003 adds the modulation current output from the information signal control unit 1001 to the bias current, and the light source 1002 modulates the frequency with the modulation signal output from the bias tee 1003 as shown in FIG. Then, an optical signal having an optical phase as shown in FIG.

  The optical transmission unit 2000 transmits the optical signal output from the optical transmission unit 1000 and outputs the optical signal to the optical reception unit 3000.

  The optical phase / intensity conversion unit 3001 has a 1-bit delay unit, and is a diagram obtained by delaying an optical signal having an optical phase as shown in FIG. 3B output from the optical transmission unit 2000 by 1 bit. By causing an optical signal having an optical phase as shown in 3 (c) to interfere, an intensity optical signal as shown in FIG. 3 (d) is output. The photoelectric conversion unit 3002 converts the output optical signal of the optical phase / intensity conversion unit 3001 into an electrical signal (information signal).

  As described above, according to the optical transmission device according to the present embodiment, in the optical transmission unit, the information signal control unit depends on the modulation frequency with respect to the phase of the optical frequency variation component of the optical signal output from the semiconductor laser. Control to suppress the deviation. This enables optical transmission with a simple configuration and reduced waveform distortion during reception, even when a low-cost general light source with modulation frequency dependency is frequency-modulated without using an optical phase modulator. Is possible.

  In the present embodiment, the optical transmission unit is controlled so as to suppress the deviation depending on the modulation frequency with respect to the phase of the optical frequency fluctuation component of the optical signal output from the semiconductor laser. In this regard, the control may be performed so as to suppress the deviation depending on the modulation frequency.

  The optical transmission apparatus of the present invention is useful as a transmission apparatus using an optical fiber regardless of long distance or short distance.

Configuration diagram of optical transmission apparatus according to Embodiment 1 of the present invention The figure which shows an example of a mode which controls so that the deviation depending on a modulation frequency may be suppressed regarding the phase of the optical frequency fluctuation component of the optical signal output from the semiconductor laser shown in FIG. The figure which shows an example of a mode that the phase and intensity | strength of a modulation signal and an optical signal change in the optical transmission apparatus which concerns on Embodiment 1 of this invention. Configuration of conventional optical transmission equipment The figure which showed the received waveform distortion at the time of transmitting the optical signal of modulation frequency 300Mbps using the conventional optical transmission apparatus.

Explanation of symbols

1000 Optical transmission unit 1001 Information signal control unit 1002 Light source 1003 Bias tee 1004 Optical phase modulator 2000 Optical transmission unit 3000 Optical reception unit 3001 Optical phase / intensity conversion unit 3002 Photoelectric conversion unit

Claims (17)

An information signal controller that inputs an information signal and controls the frequency dependence of the phase to a predetermined characteristic;
A light source that outputs an optical signal obtained by modulating an optical frequency based on a predetermined encoding method based on a signal output from the information signal control unit;
An optical transmission unit for transmitting an optical signal output from the light source;
An optical phase / intensity conversion unit that converts an optical phase fluctuation component of an optical signal output from the optical transmission unit into a light intensity fluctuation component, and outputs the optical phase fluctuation component;
An optical transmission device comprising: an optical / electrical converter that converts an optical signal output from the optical phase / intensity converter into an electrical signal. The information signal control unit controls the predetermined characteristic so as to suppress a deviation depending on a modulation frequency in a predetermined frequency band with respect to a phase of an optical frequency variation component of an optical signal output from the light source; The optical transmission device according to claim 1, wherein: The information signal control unit controls the predetermined characteristic so as to have an inverse characteristic in a predetermined frequency band with respect to a modulation frequency dependency of a phase of an optical frequency fluctuation component of an optical signal output from the light source. The optical transmission device according to claim 1. 4. The optical transmission apparatus according to claim 2, wherein the predetermined frequency band is substantially equal to an occupied band of a signal input to the light source. The optical transmission apparatus according to claim 2, wherein the predetermined frequency band includes a frequency at an inflection point in a modulation frequency dependency of an optical frequency fluctuation amount of the light source. The frequency of the inflection point in the modulation frequency dependence of the optical frequency fluctuation amount of the light source is substantially equal to the frequency at which the dominant factor of the optical frequency fluctuation phenomenon changes from the thermal effect to the carrier density fluctuation effect. Item 6. The optical transmission device according to Item 5. The optical transmission apparatus according to claim 1, wherein the information signal control unit is an electric filter. 8. The optical transmission device according to claim 7, wherein the information signal control unit is an electric filter that can be created by connecting LCR circuits in parallel. The optical transmission apparatus according to claim 7, wherein the information signal control unit is a band-pass filter. The optical transmission device according to claim 7, wherein the information signal control unit is a low-pass filter. The optical transmission apparatus according to claim 1, wherein the information signal control unit is an electric amplifier. The optical transmission apparatus according to claim 1, wherein the light source is a semiconductor laser. The optical transmission device according to claim 1, wherein the optical phase / intensity conversion unit is a Mach-Zehnder interferometer. The optical transmission apparatus according to claim 1, wherein the predetermined code system is an RZ (Return Zero) code. An information signal control unit that inputs an electrical signal and controls the frequency dependence of the phase to a predetermined characteristic;
An optical transmission device comprising: a light source that outputs an optical signal obtained by modulating an optical frequency based on a predetermined encoding method based on a signal output from the information signal control unit. An information signal control unit that inputs an electrical signal and controls the frequency dependence of the level to a predetermined characteristic;
Based on a signal output from the information signal control unit, a light source that outputs an optical signal whose optical frequency is modulated based on a predetermined encoding method;
An optical transmission unit for transmitting an optical signal output from the light source;
An optical phase / intensity conversion unit that converts an optical phase fluctuation component of an optical signal output from the optical transmission unit into a light intensity fluctuation component, and outputs the optical phase fluctuation component;
An optical transmission apparatus comprising: an optical / electrical conversion unit that converts an optical signal output from the optical phase / intensity conversion unit into an electrical signal. An information signal control unit that inputs an electrical signal and controls the frequency dependence of the level and phase to predetermined characteristics;
Based on a signal output from the information signal control unit, a light source that outputs an optical signal whose optical frequency is modulated based on a predetermined encoding method;
An optical transmission unit for transmitting an optical signal output from the light source;
An optical phase / intensity conversion unit that converts an optical phase fluctuation component of an optical signal output from the optical transmission unit into a light intensity fluctuation component, and outputs the optical phase fluctuation component;
An optical transmission apparatus comprising: an optical / electrical conversion unit that converts an optical signal output from the optical phase / intensity conversion unit into an electrical signal.

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