JP2006217128A - Optical transmitter and optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive optical transmitter with a simple configuration capable of providing a plurality of services, and an optical transmission system. <P>SOLUTION: The optical transmitter includes an optical signal generating unit 2 for multiplexing and outputting two optical signals each subjected to intensity modulation by a first electric signal corresponding to a first service, and having wavelengths different from each other and phases inverted from each other; and an optical intensity modulator 3 for applying intensity modulation to the optical signals outputted from the unit 2 with a second electric signal corresponding to a second service. In an optical receiver 8, the optical signals having the different wavelengths which have been subjected to intensity modulation by the first electric signal are canceled each other and the second service corresponding to the second electric signal can be received. In an optical receiver 10, the optical signal of the one wavelength acquired via a wavelength separation filter 11 is subjected to photoelectric conversion, and the first service corresponding to the first electric signal can be received. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical transmission apparatus and an optical transmission system that provide a plurality of services in a PON (Passive Optical Network) system or the like.

  An optical transmission system that provides a plurality of services using a PON system is disclosed in Patent Document 1, for example.

  FIG. 8 is a configuration diagram of a PON system that can provide two types of services that can be considered based on the PON system described in Patent Document 1. Here, the electrical signal A is a signal that provides the service A, and the electrical signal B is a signal that provides the service B.

  In FIG. 8, the electric signal A is input to the optical oscillator 206 constituting the optical transmission device 202, and the electric signal B is input to the optical oscillator 207. Here, the optical oscillator 206 outputs an optical signal having a wavelength λ1 modulated by the electric signal A, and the optical oscillator 207 outputs an optical signal having a wavelength λ2 modulated by the electric signal B. The optical signals having the wavelengths λ1 and λ2 are optically wavelength-multiplexed by the wavelength multiplexing coupler 208 that constitutes the optical transmission device 202, and transmitted through one optical fiber 220.

  An optical signal transmitted from the optical transmission apparatus 202 through the optical fiber 220 is branched by the optical splitter 213, and the optical reception apparatus 203 that provides the service A, the optical reception apparatus 204 that provides the service B, the service A and the service B The information is input to each of the optical receivers 205 that provide the information.

  In the optical receiver 203, the optical signal having the wavelength λ1 is separated by the wavelength separation filter 209, and the optical signal having the wavelength λ1 is converted into the electric signal A by the photoelectric conversion unit 210 and output.

  In the optical receiver 204, the optical signal having the wavelength λ2 is separated by the wavelength separation filter 211, and the optical signal having the wavelength λ2 is converted into the electric signal B by the photoelectric conversion unit 214 and output.

Further, in the optical receiver 205, the optical signal having the wavelength λ1 and the wavelength λ2 is separated by the wavelength separation filter 212, and the optical signal having the wavelength λ1 is converted into the electric signal A by the photoelectric conversion unit 215 and output. At 216, the optical signal having the wavelength λ2 is converted into an electric signal B and output.
In general, since the photoelectric conversion units 210 and 214 to 216 have no wavelength selectivity, when only an optical signal having a specific wavelength is converted into an electrical signal, the wavelength is set to the previous stage as in the optical receivers 203, 204, and 205. Separation filters 209, 211, and 212 need to be provided.

Thus, the conventional PON system provided two types of services by wavelength multiplexing two optical signals.
JP 2001-333047 A

  However, in the conventional PON system shown in FIG. 8, all of the optical receiver 203 that provides the service A, the optical receiver 204 that provides the service B, and the optical receiver 205 that provides the service A and the service B. In this optical receiver, a wavelength separation filter for extracting the optical signal having the wavelength λ1 or λ2 is required. The wavelength separation filter is generally expensive, resulting in a problem that the entire PON system becomes expensive.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide an optical transmission apparatus and an optical transmission system that can easily provide a plurality of services with an inexpensive configuration.

  An optical transmission device according to the present invention includes an optical signal generation unit that multiplexes and outputs two optical signals that are intensity-modulated by the first electrical signal, have different wavelengths, and have mutually inverted phases, and an optical signal generation unit A light intensity modulation unit that modulates the intensity of the output optical signal with the second electric signal.

  With this configuration, the multiplexed optical signal input from the light intensity modulator can be photoelectrically converted and connected to an optical receiver having a photoelectric converter that outputs an electrical signal. In the optical receiver, the first electrical signal The modulation components cancel each other, and only the modulation component of the second electric signal can be converted into an electric signal and output.

  In the optical transmission device of the present invention, the optical signal generation unit outputs a first optical signal whose intensity is modulated by the first electric signal, and an inverted signal of the first electric signal. Output from the first optical oscillation unit, the second optical oscillation unit that outputs a second optical signal having a wavelength different from that of the first optical signal output from the first optical oscillation unit. It has a configuration including a first optical signal and a wavelength multiplexing coupling unit that wavelength-multiplexes and outputs the second optical signal output from the second optical oscillation unit.

  With this configuration, the optical signal generation unit is configured by using the two optical oscillation units and the wavelength multiplexing coupling unit, and the photoelectric conversion unit that photoelectrically converts the multiplexed optical signal input from the light intensity modulation unit and outputs an electrical signal. In the optical receiving device, the modulation components of the first electric signal cancel each other, and only the modulation component of the second electric signal can be converted into an electric signal and output.

  In the optical transmission device of the present invention, the optical signal generation unit includes the first optical oscillation unit that outputs the first optical signal whose intensity is modulated by the first electric signal, and the first optical oscillation unit that has a constant intensity and the first optical signal. A second optical oscillator that outputs a second optical signal having a wavelength different from that of the first optical signal output from the optical oscillator, an optical signal output from the first optical oscillator, and a second light It has a configuration comprising a wavelength division multiplexing unit that wavelength-multiplexes and outputs the second optical signal output from the oscillation unit, and an optical amplification unit that optically amplifies the output from the wavelength division coupling unit.

  With this configuration, the optical signal generating unit includes an optical oscillation unit that outputs an optical signal whose intensity is modulated by the first electric signal, a second optical oscillation unit that outputs an optical signal having a constant intensity, and a wavelength multiplexing coupling unit. Can be connected to an optical receiver having a photoelectric converter that photoelectrically converts an input multiplexed optical signal and outputs an electrical signal. In the optical receiver, the modulation component of the first electrical signal is By canceling each other, only the modulation component of the second electric signal can be converted into an electric signal and output.

  Furthermore, an optical transmission system according to the present invention includes an optical signal generator that multiplexes and outputs two optical signals that are intensity-modulated by the first electrical signal, have different wavelengths, and have mutually inverted phases, and an optical signal generator An optical transmitter having an optical intensity modulator that modulates the intensity of the optical signal output from the optical signal with the second electrical signal, and a photoelectric conversion that photoelectrically converts the optical signal output from the optical transmitter and outputs an electrical signal And an optical receiving device having a unit.

  With this configuration, in the optical receiving apparatus, the modulation component cancels out the first electric signal, and only the modulation component of the second electric signal can be converted into an electric signal and output.

  The optical transmission system of the present invention also includes an optical signal generator that multiplexes and outputs two optical signals that are intensity-modulated by the first electrical signal, have different wavelengths, and have mutually inverted phases, and an optical signal generator. An optical transmission device having an optical intensity modulation unit that modulates the intensity of the optical signal output from the optical signal with the second electrical signal, and outputs an optical signal having a single wavelength from the optical signal output from the optical transmission device A wavelength separation unit, a photoelectric conversion unit that photoelectrically converts an output of the wavelength separation unit, and a band pass unit that passes at least one band of the first electric signal or the second electric signal among the outputs of the photoelectric conversion unit And an optical receiving device.

  With this configuration, in the optical receiver, the single-wavelength optical signal extracted by the wavelength demultiplexing unit is photoelectrically converted and passed through a predetermined band-passing unit, so that the first electric signal or the second electric signal At least one electrical signal can be output.

  The optical transmission system of the present invention also includes an optical signal generator that multiplexes and outputs two optical signals that are intensity-modulated by the first electrical signal, have different wavelengths, and have mutually inverted phases, and an optical signal generator. An optical transmitter having an optical intensity modulator that modulates the intensity of the optical signal output from the optical signal with the second electrical signal, an optical splitter that branches and outputs the optical signal output from the optical transmitter, A first photoelectric conversion unit that photoelectrically converts an output of the branching unit, a wavelength separation unit that extracts and outputs an optical signal of a single wavelength out of outputs of the optical branching unit, and a first that photoelectrically converts an output of the wavelength separation unit And an optical receiving device including a band passing unit that passes and outputs the band of the second electric signal among the outputs of the second photoelectric converting unit.

  With this configuration, in the optical receiver, one output of the optical branching unit is photoelectrically converted to obtain a second electrical signal, and the other output of the optical branching unit is photoelectrically converted via the wavelength separation unit. Then, the first electric signal is obtained by passing the output through the band passing section.

  An optical transmission device according to the present invention includes an optical signal generation unit that multiplexes and outputs two optical signals that are intensity-modulated by the first electrical signal, have different wavelengths, and have mutually inverted phases, and an optical signal generation unit An optical transmission system having a configuration including a light intensity modulation unit that modulates the intensity of the output optical signal with the second electric signal, and can easily provide a plurality of services with an inexpensive configuration.

  The optical transmission system of the present invention also includes an optical signal generator that multiplexes and outputs two optical signals that are intensity-modulated by the first electrical signal, have different wavelengths, and have mutually inverted phases, and an optical signal generator. An optical transmitter having an optical intensity modulator that modulates the intensity of the optical signal output from the optical signal with the second electrical signal, and a photoelectric conversion that photoelectrically converts the optical signal output from the optical transmitter and outputs an electrical signal And a plurality of services can be easily provided with an inexpensive configuration.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing an optical transmission system according to Embodiment 1 of the present invention. The present embodiment is composed of a PON system, and includes an optical transmitter 1 that provides service A and service B, an optical receiver 8 that receives service A, an optical receiver 10 that receives service B, and a service. The optical receiver 14 is provided with A and the service B. The optical transmitter 1 and the optical receivers 8, 10, 14 are connected by an optical fiber 110 and an optical splitter 213. The electric signal A is an electric signal for providing the service A, and the electric signal B is an electric signal for providing the service B.

  For example, service A is a terrestrial television broadcasting service, and service B is an Internet connection service. Service A is an Internet connection service, and service B is a broadcasting service such as CS. Alternatively, service A is a low-speed Internet connection service, and service B is a high-speed Internet connection service.

  The optical transmitter 1 includes an optical signal generator 2 and an optical intensity modulator 3. The optical signal generator 2 includes a branch circuit 4, an optical oscillator 5, an optical oscillator 6, and a wavelength multiplexing coupler 7. The branch circuit 4 branches the input electric signal B (electric signal S1) into two electric signals S10 and S11. The electric signal S10 is input to the optical oscillator 5 without inverting the phase, and the electric signal S11 has a phase. The signal is inverted and input to the optical oscillator 6. The optical oscillator 5 outputs to the wavelength multiplexing coupler 7 an optical signal S2 of wavelength λ1 that has been intensity-modulated by the electrical signal S10 input from the branch circuit 4. The optical oscillator 6 outputs to the wavelength multiplexing coupler 7 an optical signal S3 having a wavelength λ2 that has been intensity-modulated by the electric signal S11 input from the branch circuit 4. The wavelength multiplexing coupler 7 wavelength-multiplexes the input optical signal S2 and optical signal S3, and outputs them to the optical intensity modulator 3 as an optical signal S4 of wavelength λ1 + λ2.

  The light intensity modulator 3 performs light intensity modulation on the optical signal S4 having the wavelength λ1 + λ2 output from the optical signal generator 2 with the electric signal A, and outputs the result as an optical signal S5 having the wavelength λ1 + λ2.

  The operation of the optical transmission device 1 will be described with reference to FIGS. 2A to 2F illustrate the case where the frequency band of the electric signal A is higher than the frequency band of the electric signal B. In order to simplify the explanation, both the electric signal A and the electric signal B are expressed as sine waves.

  FIG. 2A is a waveform diagram showing the electric signal B (electric signal S1). The electric signal S1 is inputted to the branch circuit 4 and branched, one of which is output to the optical oscillator 5 as the electric signal S10 without being inverted in phase, and the other is output to the optical oscillator 6 as the electric signal S11 with the phase inverted. . The optical signals S2 and S3 of the optical oscillator 5 and the optical oscillator 6 driven by these electric signals have waveforms whose phases are inverted as shown in FIGS. 2B and 2C. . These optical signals are multiplexed by the wavelength multiplexing coupler 7, and the optical intensity modulator 3 modulates the intensity by the electric signal A shown in FIG. 2D, and outputs it as an optical signal S5. The components of wavelength λ1 and wavelength λ2 of the optical signal S5 have the waveforms shown in FIGS. 2 (e) and 2 (f), respectively. That is, the waveforms of the wavelength λ1 component and the wavelength λ2 component of the optical signal S5 are inverted in phase with respect to the modulation component of the electrical signal B, and have the same phase with respect to the modulation component of the electrical signal A.

  Note that a phase-inverted signal may be obtained by using a differential circuit such as a differential amplifier for the branch circuit 4.

  The optical signal S5 output from the optical transmitter 1 is transmitted through the optical fiber 110 and input to the optical splitter 213. The optical splitter 213 branches the optical signal S5 and outputs it to the optical receiver 8, the optical receiver 10, and the optical receiver 14.

  The optical receiver 8 includes a photoelectric conversion unit 9. The photoelectric conversion unit 9 receives both the wavelength λ1 component of the optical signal S5 shown in FIG. 3A and the wavelength λ2 component of the optical signal S5 shown in FIG. Since the photoelectric conversion unit 9 does not have wavelength selectivity, the wavelength λ1 component and the wavelength λ2 component of the optical signal S5 are combined and converted into an electrical signal. As shown in FIGS. 3A and 3B, the signal S5 has a low frequency component (corresponding to the electric signal B) whose phases are inverted between the wavelength λ1 and the wavelength λ2. 9 cancel each other, and an electric signal S6 having a high frequency component shown in FIG.

  The optical receiver 10 includes a wavelength separation filter 11, a photoelectric conversion unit 12, and a low-pass filter 13. The wavelength separation filter 11 extracts the optical signal having the wavelength λ1 shown in FIG. 3A from the optical signal S5 having the wavelength λ1 + λ2, and outputs the optical signal to the photoelectric conversion unit 12. The photoelectric conversion unit 12 photoelectrically converts the optical signal having the wavelength λ1 output from the wavelength separation filter 11 and outputs the converted electric signal to the low-pass filter 13. The low-pass filter 13 extracts a low-band component corresponding to the electric signal B from the electric signal output from the photoelectric conversion unit 12, and outputs an electric signal S7 (electric signal B) shown in FIG.

  If the electrical signal B is an electrical signal that is frequency-modulated, for example, and is not affected by the phase inversion, the wavelength extracted by the wavelength separation filter 11 may be the wavelength λ2.

  In the optical receiver 10, the low-pass filter 13 is used on the assumption that the frequency band of the electric signal A is higher than the frequency band of the electric signal B. However, the frequency band of the electric signal B is higher than the frequency band of the electric signal A. In this case, a high pass filter may be used instead of the low pass filter 13.

  The optical receiver 14 includes a wavelength separation filter 15, a photoelectric conversion unit 16, a high pass filter 17, and a low pass filter 18. The wavelength separation filter 15 extracts the optical signal having the wavelength λ1 shown in FIG. 3A from the optical signal S5 having the wavelength λ1 + λ2, and outputs the optical signal to the photoelectric conversion unit 16. The photoelectric conversion unit 16 photoelectrically converts the optical signal output from the wavelength separation filter 15 and outputs the converted electric signal to the high-pass filter 17 and the low-pass filter 18. The high pass filter 17 extracts a high-frequency component corresponding to the electric signal A from the electric signal output from the photoelectric conversion unit 16, and outputs an electric signal S8 (electric signal A) shown in FIG. The low-pass filter 18 extracts a low-frequency component corresponding to the electric signal B from the electric signal output from the photoelectric conversion unit 16, and outputs it as an electric signal S9 (electric signal B) shown in FIG.

  In the case where the electric signal A and the electric signal B are, for example, frequency-modulated electric signals and are not affected at all by the phase inversion, the wavelengths extracted by the wavelength separation filters 11 and 15 are set to the wavelength λ2. It is also good.

  The optical receiver 14 outputs the electric signal A using the high-pass filter 17 on the assumption that the frequency band of the electric signal A is higher than the frequency band of the electric signal B, and outputs the electric signal B using the low-pass filter 18. When the frequency band of the electric signal B is higher than the frequency band of the electric signal A, the electric signal B is output using the high-pass filter 17 and the electric signal A is output using the low-pass filter 18. You can do that.

  As described above, according to the present embodiment, it is not necessary to mount an expensive wavelength separation filter in the optical receiver 8, and the entire system can be made inexpensive. In particular, when there are many users who receive service A and few users receive only service B, or when there are many users of service A and few users receive both services A and B, the conventional PON shown in FIG. Compared to the system, the entire system can be made cheaper.

  When the optical receiver 204 that receives service B in the conventional PON system shown in FIG. 8 is compared with the optical receiver 10 that receives service B in the PON system of the present embodiment, in this embodiment, Although a low-pass filter 13 is added, the low-pass filter 13 is a member of an electric circuit and is inexpensive compared to a member of an optical circuit such as a wavelength separation filter.

  8 is compared with the optical receiver 205 that receives the services A and B in the conventional PON system shown in FIG. 8, and the optical receiver 14 that receives the services A and B in the PON system of this embodiment. In this embodiment, only one photoelectric conversion unit is required, and a high-pass filter 17 and a low-pass filter 18 are added. However, the high-pass filter 17 and the low-pass filter 18 are members of an electric circuit, and are a wavelength separation filter and a photoelectric converter. It is less expensive than optical circuit members such as a converter.

  In the PON system of the present embodiment, it will be described below that service B can be added with an inexpensive configuration even when a PON system providing service A is already installed.

  FIG. 4 is a block diagram showing a PON system that already provides the service A. The optical transmission device 101 includes an optical oscillator 206, and when the electrical signal A is input, the optical oscillator 206 transmits an optical signal having a wavelength λ 1 modulated by the electrical signal A to the optical splitter 213 through the optical fiber 110. Output. The optical splitter 213 branches this optical signal and outputs it to the optical receiver 103 installed in each home. Each optical receiving device 103 includes a photoelectric conversion unit 210. The photoelectric conversion unit 210 converts an optical signal having a wavelength λ1 input to the optical receiving device 103 into an electrical signal A and outputs the electrical signal A. As described above, the PON system shown in FIG. 4 can receive the service A at home.

  However, if the PON system that provides only service A shown in FIG. 4 is changed to a system that can provide both service A and service B, the conventional configuration becomes the configuration of the PON system shown in FIG. It is necessary to add a wavelength separation filter 209 to the receiving apparatus 103.

  The optical receiver 103 is generally installed at a user's home. In order to add the wavelength separation filter 209 to the optical receiver 103, the optical receiver 103 visits each user's home where the optical receiver 103 is installed. It must be replaced or modified, which is expensive and requires a lot of labor.

  However, according to the present embodiment, as shown in FIG. 1, by using the conventional optical receiver 103 shown in FIG. 4 as the optical receiver 8 as it is, the entire system provides service A and service B. However, there is no need to change the optical receiver that receives only the service A. Therefore, it is not necessary to visit the user's home receiving the service A, replace or modify the optical receiving device, and is inexpensive and does not require labor.

  In this case, the optical transmission device 101 needs to be changed to the optical transmission device 1 shown in FIG. 1, but generally, the optical transmission device is centrally installed in one place, compared with the optical reception device. Very few installations are required, and replacement and modification are easy.

  As described above, in the present embodiment, even when a PON system that provides the service A is already installed, the optical transmission apparatus 103 can be changed without changing the optical reception apparatus 103 that has already received the service A. The service B can be additionally provided inexpensively and easily only by adding the optical receiver that receives the service B.

(Embodiment 2)
FIG. 5 is a block diagram showing an optical transmission system according to Embodiment 2 of the present invention. In FIG. 5, the same components as those of the optical transmission system of FIG.

  The difference between the optical transmission system of the present embodiment and the optical transmission system shown in FIG. 1 is that the optical signal generator 2 in the optical transmission device 1 of FIG. 1 has a different configuration.

  In FIG. 5, the optical signal generator 21 includes an optical oscillator 22, an optical oscillator 23, a wavelength multiplexing coupler 24, and a semiconductor optical amplifier 25. The optical oscillator 22 outputs an optical signal having a wavelength λ1 modulated by the electric signal B (electric signal S1) to the wavelength multiplexing coupler 24 as an optical signal S21. The optical oscillator 23 outputs an optical signal having a wavelength λ2 that is not intensity-modulated, that is, having a constant intensity, to the wavelength multiplexing coupler 24 as an optical signal S22. The wavelength multiplexing coupler 24 wavelength-multiplexes the input optical signal S 21 and the optical signal S 22 and outputs the multiplexed optical signal S 23 to the semiconductor optical amplifier 25. The semiconductor optical amplifier 25 performs optical amplification with a saturation phenomenon on the input optical signal S23 having the wavelength λ1 + λ2, and outputs the amplified optical signal as the optical signal S4.

  The operation of the optical signal generator 21 will be described with reference to FIGS. The optical oscillator 22 outputs the optical signal S21 having the wavelength λ1 shown in FIG. 6B, which has been intensity-modulated with the electric signal S1 shown in FIG. On the other hand, the optical oscillator 23 outputs the optical signal S22 having the wavelength λ2 shown in FIG. 6C, which is not subjected to intensity modulation, that is, has a constant intensity, to the wavelength multiplexing coupler 24. The wavelength multiplexing coupler 24 multiplexes the optical signal S21 and the optical signal S22, and outputs the multiplexed optical signal S23 to the semiconductor optical amplifier 25. At this time, the wavelength λ1 component of the optical signal S23 has the waveform shown in FIG. 6B, and the wavelength λ2 component of the optical signal S23 has the waveform shown in FIG. When receiving the optical signal S23, the semiconductor optical amplifier 25 outputs the optical signal S4 shown in FIG. 6D and FIG. 6E in which the wavelength λ1 component and the wavelength λ2 component are inverted from each other.

  This is due to the saturation phenomenon of the semiconductor optical amplifier, and is output so that the total light output is saturated. The gain in the semiconductor optical amplifier 25 for the wavelength λ2 component of the optical signal S23 shown in FIG. 6C increases as the optical intensity of the wavelength λ1 component of the optical signal S23 shown in FIG. As the light intensity of the wavelength λ1 component of S23 increases, it decreases. Therefore, the wavelength λ2 component of the optical signal S23 is modulated by the semiconductor optical amplifier 25 as shown in FIG. 6E, and is output as the wavelength λ2 component of the optical signal S4. Accordingly, the modulation component of the wavelength λ2 component of the optical signal S4 is inverted in phase from the modulation component of the wavelength λ1 component of the optical signal S4.

  As described above, also in the second embodiment, the optical signal generator 21 obtains the same optical signal S4 as that of the optical signal generator 1 of the first embodiment, and as a result, operates in the same manner as in the first embodiment. The optical transmission device 1 is obtained. Therefore, also in the optical transmission system of the second embodiment, two services can be easily provided at a low cost as in the first embodiment.

(Embodiment 3)
FIG. 7 is a block diagram showing an optical transmission system according to Embodiment 3 of the present invention. In FIG. 7, the same components as those of the optical transmission system of FIG.
In the present embodiment and the optical transmission system shown in FIG. 1, the optical receiver 31 of this embodiment has a different configuration from that of FIG. 1, and the other configurations are the same.

  The optical receiver 31 includes an optical splitter 32, a photoelectric conversion unit 33, a wavelength separation filter 34, a photoelectric conversion unit 35, and a low pass filter 36.

  The optical splitter 32 branches the optical signal S5 obtained by multiplexing the optical signals of the wavelengths λ1 and λ2 as it is, and outputs the branched optical signal S5 to the photoelectric conversion unit 33 and the wavelength separation filter 34.

  The photoelectric conversion unit 33 operates in the same manner as the photoelectric conversion unit 9 of the optical receiver 8 illustrated in FIG. 1, and outputs the signal illustrated in FIG. 3C as an electric signal S31 (electric signal A). In addition, the wavelength separation filter 34, the photoelectric conversion unit 35, and the low-pass filter 36 operate in the same manner as the wavelength separation filter 11, the photoelectric conversion unit 12, and the low-pass filter 13 of the optical receiver 10, and are illustrated in FIG. The signal is output as an electric signal S32 (electric signal B).

  As described above, also in the third embodiment, the electric signal A and the electric signal B are obtained using the optical receiver 31 as in the optical receiver 14 of the first embodiment. Therefore, also in the optical transmission system of the third embodiment, two services can be easily provided at a low cost as in the first embodiment.

  In each of the above embodiments, as the optical oscillators 5, 6, 22, and 23, an optical laser, a semiconductor laser, an LED, or the like may be used.

  In each of the above embodiments, the PON system has been described. However, the present invention is not limited to the PON system, and the optical signal S5 output from the transmission device 1 is not limited to the PON system. It can be used in all optical transmission systems input to 10, 14, and 31.

  Further, in the first and second embodiments, an optical transmission system in which the optical transmitter 1 and the optical receivers 8, 10, and 14 are combined. In the third embodiment, the optical transmitter 1 and the optical receivers 8, 10, and 31 are combined. However, the present invention is not limited to this combination, and the combination of the optical transmitter 1 and the optical receivers 8, 10, 14, and 31 may be arbitrary. That is, a combination of the optical transmitter 1 and the optical receiver 8, a combination of the optical transmitter 1 and the optical receiver 10, a combination of the optical transmitter 1 and the optical receiver 14, and a combination of the optical transmitter 1 and the optical receiver 31 Any combination of the optical transmitter 1 and the optical receivers 8 and 10 or the optical receiver 1 and the optical receivers 14 and 31 is possible.

  Further, in each of the above-described embodiments, the case where two services are provided has been described. However, the present invention is not limited to two services, and the optical signal generators 2 and 21 can transmit optical signals whose phases are different by 90 ° and 270 °. A system capable of providing a plurality of services such as generating optical signals of wavelengths λ3 and λ4 can be configured.

  The present invention can provide a plurality of services with an inexpensive configuration, and is useful for an optical transmission system using a PON system.

The block diagram which shows the optical transmission system in Embodiment 1 of this invention (A) Waveform diagram showing the electric signal S1 of the optical transmission apparatus according to the first embodiment of the present invention (b) Waveform diagram showing the signal S2 (c) Waveform diagram showing the signal S3 (d) The electric signal A (E) Waveform diagram showing the wavelength λ1 component of the signal S5 (f) Waveform diagram showing the wavelength λ2 component of the signal S5 (A) Waveform diagram showing the wavelength λ1 component of the signal S5 of the optical receiver in Embodiments 1 and 2 of the present invention (b) Waveform diagram showing the wavelength λ2 component of S5 (c) Electrical signal S6 (D) Waveform diagram showing the electric signal S7 Configuration diagram of a PON system receiving only service A for explaining the optical transmission system according to the first embodiment of the present invention The block diagram which shows the optical transmission system in Embodiment 2 of this invention (A) Waveform diagram showing signal S1 of optical signal generator 21 in Embodiment 2 of the present invention (b) Waveform diagram showing wavelength λ1 component of signals S21 and S23 (c) Wavelength λ2 component of S22 and S23 (D) Waveform diagram showing the wavelength λ1 component of the signal S4 (e) Waveform diagram showing the wavelength λ2 component of the signal S4 The block diagram which shows the optical transmission system in Embodiment 3 of this invention Configuration diagram showing a conventional optical transmission system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical transmitter 2, 21 Optical signal generation part 3 Optical intensity modulator 4 Branch circuit 5, 6, 22, 23 Optical oscillator 7, 24 Wavelength multiplexing coupler 8, 10, 14, 31 Optical receiver 9, 12, 16, 33, 35 Photoelectric conversion unit 11, 15, 34 Wavelength separation filter 13, 18, 36 Low pass filter 17 High pass filter 25 Semiconductor optical amplifier 110 Optical fiber 32, 213 Optical splitter

Claims (6)

An optical signal generator that multiplexes and outputs two optical signals that are intensity-modulated by the first electric signal, have different wavelengths, and have mutually inverted phases, and an optical signal output from the optical signal generator And an optical intensity modulation unit that modulates the intensity with the electric signal of 2. The optical signal generator is configured to output a first optical signal that outputs a first optical signal that has been intensity-modulated by the first electric signal; an intensity signal that is intensity-modulated by an inverted signal of the first electric signal; A second optical oscillation unit that outputs a second optical signal having a wavelength different from that of the first optical signal output from the first optical oscillation unit; and a first light output from the first optical oscillation unit The optical transmission device according to claim 1, further comprising: a signal; and a wavelength multiplexing coupling unit that wavelength-multiplexes and outputs the second optical signal output from the second optical oscillation unit. The optical signal generator outputs a first optical signal that outputs a first optical signal whose intensity is modulated by the first electric signal, and is output from the first optical oscillator that has a constant intensity. A second optical oscillation unit that outputs a second optical signal having a wavelength different from that of the first optical signal; an optical signal output from the first optical oscillation unit; and an output from the second optical oscillation unit 2. The optical transmission device according to claim 1, further comprising: a wavelength multiplexing coupling unit that wavelength-multiplexes and outputs the second optical signal; and an optical amplification unit that optically amplifies the output from the wavelength multiplexing coupling unit. An optical signal generator that multiplexes and outputs two optical signals that are intensity-modulated by the first electric signal, have different wavelengths, and have mutually inverted phases, and an optical signal output from the optical signal generator An optical transmission device having an optical intensity modulation unit that modulates the intensity of the electric signal by two electric signals, and an optical reception device having a photoelectric conversion unit that photoelectrically converts an optical signal output from the optical transmission device and outputs an electric signal. Optical transmission system equipped. An optical signal generator that multiplexes and outputs two optical signals that are intensity-modulated by the first electric signal, have different wavelengths, and have mutually inverted phases, and an optical signal output from the optical signal generator An optical transmission device having an optical intensity modulation unit that modulates the intensity with an electric signal of 2; a wavelength separation unit that extracts and outputs a single-wavelength optical signal from the optical signal output from the optical transmission device; and the wavelength separation An optical receiver having a photoelectric conversion unit that photoelectrically converts an output of the unit, and a band-passing unit that passes at least one band of the first electric signal or the second electric signal among the outputs of the photoelectric conversion unit And an optical transmission system. An optical signal generator that multiplexes and outputs two optical signals that are intensity-modulated by the first electric signal, have different wavelengths, and have mutually inverted phases, and an optical signal output from the optical signal generator An optical transmission device having an optical intensity modulation unit that modulates the intensity with an electric signal of 2, an optical branching unit that branches and outputs an optical signal output from the optical transmission device, and one output of the optical branching unit A first photoelectric conversion unit that performs photoelectric conversion, a wavelength separation unit that extracts and outputs an optical signal having a single wavelength out of the other output of the optical branching unit, and a second that performs photoelectric conversion on the output of the wavelength separation unit An optical transmission system comprising: a photoelectric conversion unit; and an optical receiver having a band-passing unit that passes and outputs the band of the second electric signal among the outputs of the second photoelectric conversion unit.

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