JP6363933B2 - Optical transmitter / receiver, optical receiver, and optical transmitter / receiver method - Google Patents

Description

The present invention relates to an optical transmission receiver apparatus for use in an optical transmission system using digital coherent demodulation, to an optical receiver and an optical transmission and reception method.

  As a transmission code used in an optical transmission system, a QAM signal capable of transmitting a large-capacity optical signal at a low symbol rate has attracted attention. The simplest QAM is quaternary QAM (Quadrature Amplitude Modulation) and is called QPSK (Quadrature Phase Shift Keying).

FIG. 4 is a diagram showing a configuration of a conventional optical QAM signal transmission / reception system. A CW (Continuous Wave) light source 1 outputs CW light having a wavelength λ _sig with high coherency. The optical transmitter 2 receives the CW light, performs optical modulation, generates an optical QAM signal, and transmits it. The optical QAM signal emitted from the optical transmitter 2 is transmitted through the optical fiber 3. The optical receiver 4 receives an optical QAM signal via the optical fiber 3. In order to demodulate the optical QAM signal in the optical receiver 4, a technique called digital coherent demodulation is generally used.

In digital coherent demodulation, a received optical signal is converted into an electrical signal, and then demodulation is performed by calculating information on the optical phase and optical amplitude at the time of transmission using a high-speed computing unit. For digital coherent demodulation, local light with high coherency is essential. The optical receiver 4 inputs the local light of the wavelength λ _Lo generated by the local light source 5 together with the signal light. The optical receiver 4 includes an optical interferometer 100 called a 90-degree hybrid (hereinafter referred to as a 90-degree hybrid 100), an OE (Optical Electronic) converter connected to the optical interferometer 100, and an amplifier that operates and amplifies the outputs thereof. The photoelectric conversion unit 101 is provided.

There are various styles of the 90-degree hybrid 100 and the photoelectric conversion unit 101. Here, the simplest configuration example will be described. FIG. 5 is a diagram illustrating a configuration of the 90-degree hybrid 100 and the photoelectric conversion unit 101 having the simplest configuration. The signal light and the local light input from the signal light input terminal 6 and the local light input terminal 7 are transmitted by the first optical branch 8, the second optical branch 9, the third optical branch 10 and the fourth optical branch 11. , Demultiplexed or combined. Then, a total of four optical outputs are obtained from the third optical branch 10 and the fourth optical branch 11. Here, a part of the local light is added to the optical phase by a delay of π / 2 by the optical delay circuit 12. The obtained four types of interference light are converted into electrical signals by the first OE converter 13, the second OE converter 14, the third OE converter 15, and the fourth OE converter 16 and output. This output is amplified and output by the first differential amplifier 17 and the second differential amplifier 18. Then, finally obtaining two electric signals _{V 1} and _{V 2.}

Here, the relationship between the signal light and local electric light electric fields E _sig and E _Lo and the electric signals V ₁ and V ₂ will be briefly described. The optical electric field E _sig of the signal light is expressed by E _sig = A _sig exp (iω _sig t + iφ _sig ) (1)
And the local electric light field E _Lo is E _Lo = exp (iω _Lo t) (2)
It expresses. Here, ω _sig and ω _Lo are the carrier frequency of signal light and the angular frequency of local light, t is time, and i is an imaginary unit. A _sig and φ _sig are information propagated by the QAM signal. In the case of QPSK, A _sig = 1 and φ _sig is π / 2 × nrad. Here, n is an integer. In the following equations, non-essential coefficients are omitted. In the optical receiver 4, the optical electric fields E _sig and E _Lo are combined by a 90-degree hybrid and then electrically converted,
V ₁ = A _sig sin {(ω _sig −ω _Lo ) t + φ _sig } (3)
V ₂ = A _sig cos {(ω _sig −ω _Lo ) t + φ _sig } (4)
To obtain the binary value. Here, ω _sig −ω _Lo is called a frequency offset.

In heterodyne detection, the frequency offset is larger than the spectral band of the optical QAM signal, and in ideal homodyne detection, the frequency offset is zero. If ω _sig and ω _Lo are constant regardless of time, since (ω _sig −ω _Lo ) t increases monotonically with time, the frequency offset can be canceled relatively easily. If the frequency offset is canceled, the values of φ _sig and A _sig can be obtained from the comparison between the electric signals V ₁ and V ₂ , and the optical QAM signal can be demodulated. For canceling the frequency offset, an existing algorithm such as an n-th power method can be used.

However, in the prior art, since the CW light source 1 and the local light source 5 are installed at locations separated from each other, it is difficult to keep the wavelength difference constant, and an error always occurs. This error reaches several GHz at the end of life. Therefore, the frequency offset ω _sig −ω _Lo is not a constant value but also changes over time. Another error factor is fluctuation of the optical phase of the CW light source 1 and the local light source 5. Since there is no perfect CW light source, the optical electric fields E _sig and E _Lo have optical phase noises φ _Noise and φ _LoNoise , and the optical electric fields E _sig and E _Lo are written in the following form.
E _sig = A _sig exp (iω _sig t + iφ _sig + iφ _Noise ) (5)
_{E Lo = exp (iω Lo t} + iφ LoNoise) ··· (6)
If the electric signals V ₁ and V ₂ are rewritten using these equations (5) and (6), V ₁ = A _sig sin {(ω _sig −ω _Lo ) t + φ _sig + φ _Noise −φ _LoNoise } (...) 7)
V ₂ = A _sig cos {(ω _sig −ω _Lo ) t + φ _sig + φ _Noise −φ _LoNoise } (8)
Get.

If the frequency offset ω _sig −ω _Lo is not completely compensated, or if the optical phase noises φ _Noise and φ _LoNoise are so large that they cannot be ignored, signal quality degradation will occur, so that these effects can be completely compensated or reduced. Very important. In the prior art, the frequency offset compensation algorithm has a certain pull-in range, and can follow the wavelength change of the light source to some extent. However, in order to perform such processing, it is necessary to perform real-time arithmetic processing using a high-speed digital signal processor. Further, the optical phase noises φ _Noise and φ _{LoNoise do not} have an effective means for compensation in the conventional demodulation technique.

For this reason, it is necessary to reduce the optical phase noises φ _Noise and φ _LoNoise by using the CW light source 1 having the _highest possible performance. These methods in the prior art lead to an increase in the size of the transmission / reception device, making circuit design difficult. In particular, in a subscriber optical transmission system, an increase in the size and price of a receiving device and an increase in power consumption are very serious problems.

On the other hand, as a conventional technique for suppressing the influence of the optical phase noise φ _Noise , the output is branched before modulating the output of the CW light source 1, and the branched CW light is sent to the optical receiver 4 and used as local light. There is technology to do. Although this technique cannot suppress the optical phase noise φ _Noise itself, the optical phase noise φ _Noise and φ _LoNoise in the equations (7) and (8) become equal, so the influence of the optical phase noise can be ignored. .

  However, in this prior art, in order to transmit local light having the same wavelength as that of signal light, signal light and local light are polarization-multiplexed (for example, see Non-Patent Document 1), or signal light using a multi-core fiber. Thus, it is necessary to devise a method of spatially multiplexing the local light (for example, see Non-Patent Document 2).

Moriya Nakamura and Yukiyoshi Kamio, "30-Gbps (5-Gsymbol / s) 64-QAM Self-Homodyne Transmission over 60-km SSMF using Phase-Noise Cancelling Technique and ISI-Suppression based on Electronic Digital Processing", OSA / OFC / NFOEC 2009 JM Delgado Mendinueta, BJ Puttnam, J. Sakaguchi, RS Luis, W. Klaus, Y. Awaji, N. Wada, A. Kanno and T. Kawanishi, "Energy Efficient Carrier Phase Recovery for Self-Homodyne Polarization-Multiplexed QPSK", 2013 IEICE

  As described above, in the prior art, since the CW light source and the local light source are installed at locations separated from each other, it is difficult to keep the wavelength difference constant, and there is a problem that an error always occurs. . In order to solve such a problem, the signal light and the local light are transmitted by polarization multiplexing to transmit the local light having the same wavelength as the signal light, or the signal light and the local light are spatially multiplexed using a multi-core fiber. There is a way.

  However, in these methods, in order to transmit local light having the same wavelength as the signal light, the signal light and local light are polarization-multiplexed, or the signal light and local light are spatially multiplexed using a multi-core fiber. Since a device is necessary, there is a problem that the configuration is complicated and the frequency utilization efficiency of the transmission path is lowered.

The present invention has been made in view of such circumstances, the optical transmission receiver device capable of removing both the frequency offset and the light source of the optical phase noise with a simple configuration, an optical receiver and an optical transmission and reception method The purpose is to provide.

The present invention modulates the output of the CW light source and the CW light source so that the optical modulation signal having the carrier frequency ω _c and the optical frequency ω _c ± nω _Δ (where n is a natural number and ω _Δ is the angle of each emission line spectrum. Light modulation means for generating and outputting a plurality of emission line spectra having a frequency interval).

The present invention includes a CW light source, a light branching means for branching the output of the CW light source, a data signal modulating means carrier frequency by modulating the output of one of said optical branching means for generating a modulated optical signal of omega _c The emission line spectrum that modulates the other output of the optical branching means to generate a plurality of emission line spectra having an optical frequency of ω _c ± nω _Δ (where n is a natural number and ω _Δ is the angular frequency interval of each emission line spectrum). And generating means, and combining means for combining the output of the data signal modulating means and the output of the bright line spectrum generating means to output to the optical transmission line.

The present invention provides a multi-wavelength light generating means for generating a plurality of CW lights having the same frequency interval, and at least one of the CW lights output from the multi-wavelength light generating means for modulation to modulate the carrier frequency. a data signal modulating means for generating an optical modulation signal of ω _c , and an optical frequency of ω _c ± nω _Δ (where n is a natural number and ω _Δ is a multi-wavelength light generating means of the CW light output from the multi-wavelength light generating means The bright line spectrum generating means for demultiplexing at least two CW lights having an angular frequency interval), and the output of the data signal modulating means and the output of the bright line spectrum generating means are combined and output to the optical transmission line. And a multiplexing means.

  According to the present invention, the multi-wavelength light generating means includes at least two types of CW light sources and an optical waveguide, and the optical waveguide receives the output of the CW light source, and the optical waveguide is subjected to at least three types of CW by four-wave mixing. It is characterized by outputting light.

  The present invention is characterized in that at least one of the output of the data signal modulating means and the output of the bright line spectrum generating means is polarization multiplexed.

In the present invention, an optical modulation signal having a carrier frequency of ω _c and an optical frequency of ω _c ± nω _Δ (n is a natural number, ω _Δ is an angular frequency of each emission line spectrum) from an optical signal transmitted from an optical transmission line. Signal local oscillation separating means for separating at least two types of bright line spectra that are intervals), and the light modulation signal and the bright line spectrum separated by the signal local oscillation separating means are respectively input to the signal light input port and the local light emission input. A 90-degree hybrid that is input to the port, and an electrical conversion unit that receives and electrically converts interference light output from the 90-degree hybrid.

The present invention includes a low-pass filter that cuts off a high-frequency component from the output of the electrical conversion means, and the cutoff frequency of the low-pass filter is larger than a symbol rate of the optical modulation signal and smaller than _ωΔ .

The present invention relates to an optical transmitter comprising a CW light source, optical branching means, data signal modulating means, bright line spectrum generating means, and multiplexing means, signal local oscillation separating means, 90-degree hybrid, electrical conversion An optical transmission / reception method performed by an optical communication system comprising: an optical receiver comprising: an optical branching step in which the optical branching unit branches an output of the CW light source; and the data signal modulating unit includes the optical signal a data signal modulating step of the carrier frequency to produce a modulated optical signal of omega _c by modulating the output of one of the branching means, the line spectrum generating means, the other a modulates the optical frequency of the output of said optical branching means ω _c ± nω Δ _(n is a natural number, the omega _delta angular frequency interval of each bright line spectrum) and line spectrum generation step of generating a plurality of line spectra are, said multiplexing means, said data A combining step for combining the output of the signal modulation means and the output of the bright line spectrum generating means and outputting the combined signal to the optical transmission line; and the signal local oscillation separating means from the optical signal sent from the optical transmission line A signal local oscillation separating step for separating the optical modulation signal having a carrier frequency of ω _c and a plurality of emission line spectra having an optical frequency of ω _c ± nω _Δ , and the 90-degree hybrid comprises the signal local oscillation separation means A 90 degree hybrid step for inputting the optical modulation signal and the bright line spectrum separated by the signal light into the signal light input port and the local light emission input port, respectively, and the electrical conversion means outputs the interference light output from the 90 degree hybrid. And an electrical conversion step for receiving light and performing electrical conversion.

  According to the present invention, it is possible to remove both the frequency offset and the optical phase noise of the light source with a simple configuration without using a high-speed arithmetic device. Further, since it is not necessary to prepare local light on the optical receiver side, there is an effect that the apparatus configuration and price of the optical receiver can be reduced.

It is a figure which shows the structure of the optical QAM transmission system by 1st Embodiment of this invention. It is a figure which shows the structure of the optical QAM transmission system by 2nd Embodiment of this invention. It is a figure which shows the structure of the optical QAM transmission system by 4th Embodiment of this invention. It is a figure which shows the structure of the optical QAM signal transmission / reception system by a prior art. FIG. 5 is a diagram illustrating a configuration of an optical interferometer (90-degree hybrid) 100 and a photoelectric conversion unit 101 illustrated in FIG. 4.

  Hereinafter, an optical transmitter and an optical receiver according to embodiments of the present invention will be described with reference to the drawings. The present embodiment can be used for any multi-level QAM modulator including QPSK, and can also be applied to a BPSK (Binary Phase Shift Keying) signal whose optical phase does not have a quadrature component. For simplicity, the optical QAM signal system will be described here. Although this embodiment can also be used for polarization multiplexed signals, for the sake of simplicity, description will be given mainly using a single polarization optical QAM transmission / reception system as an example.

In this embodiment, a single CW light source is provided on the optical transmitter side, from which an optical modulation signal having a carrier frequency of ω _c and an optical frequency of ω _c ± nω _Δ (where n is a natural number and ω _Δ is an emission line spectrum). And a plurality of emission line spectra having an angular frequency interval). The bright line spectrum is sent to the transmission line together with the optical modulation signal for use as local light. CW light source outputs light field _{E c} a _{E c = exp (iω c t} + iφ Noise) ··· (9)
And

Here, φ _Noise is the optical phase noise of the light source as described above, and it is difficult to make it zero. From this light, a plurality of CW lights having a frequency interval of ω _Δ are generated. Here, there are a total of three types. The resulting three types of optical electric fields E _c , E _Lo1 , E _Lo2 are:
_{E c = exp (iω c t} + iφ Noise) ··· (10)
E _Lo1 = exp (i (ω _c + ω _Δ ) t + iφ _Noise ) (11)
E _Lo2 = exp (i (ω _c −ω _Δ ) t + iφ _Noise + iπ) (12)
It becomes. Here, E _Lo2 has a term of iπ because it is assumed that CS-RZ modulation is used for generation of E _Lo1 and E _Lo2 , but in other embodiments, this term has a value other than iπ. There is no problem.

Next, optical modulation of _{E c.} Here, it is assumed that an optical QAM signal is generated by an IQ modulator. Similar to equation (5),
_{E sig = A sig exp (iω} c t + iφ sig + iφ Noise + iθ) ··· (13)
Get. The optical phase θ is a fixed optical phase delay caused by the delay time difference τ between the input and output of the IQ modulator. If the fluctuation amount of φ _Noise in the delay time difference τ is sufficiently small, what value is θ? However, there is no problem in demodulation.

In the present embodiment, three types of optical signals E _sig , E _Lo1 , and E _Lo2 are input to the optical transmission line. In the optical receiver, these optical signals are separated into two sets of E _sig and E _Lo1 and E _Lo2, and E _sig is _handled as signal light, and both E _Lo1 and E _Lo2 are handled as local light. E _sig is input to the 90 ° hybrid signal light input terminal 6 shown in FIG. 5, and two of E _Lo1 and E _Lo2 are input to the local light input terminal 7 simultaneously. It should be noted here that in Expressions (7) and (8), φ _Noise and φ _LoNoise are random values that are uncorrelated with each other, so that φ _Noise −φ _LoNoise does not become zero. Since one CW light is used, this term in the equations (7) and (8) becomes zero. Instead, in this embodiment, the beat frequency is generated because two local lights are used.

If details are omitted, but only the calculation results are shown, the electric signals V ₁ and V ₂ obtained in the final stage of the configuration shown in FIG. 5 are V ₁ = 8A _sig cos (φ _sig + θ) sin (ω _Δ t) ( 14)
V ₂ = −8A _sig sin (φ _sig + θ) sin (ω _Δ t) (15)
It becomes. If the ratio of the two is taken, the factor of sin (ω _Δ t) is canceled, and φ _sig + θ can be obtained by using an inverse trigonometric function. Here, θ remains without being erased, but the value of θ is a constant that hardly depends on time. _Therefore, the phases φ _sig (t) + θ and φ _sig (t−ΔT) + θ of two temporally continuous symbols By taking the difference, θ can be removed. ΔT is a symbol period. Alternatively, as in the prior art, θ can be mathematically removed using a fourth power method or the like. On the other hand, A _sig can be obtained by taking the sum of the squares of both V ₁ and V ₂ .

The above description does not depend on the value of ω _Δ. Therefore, by using the above-described method, the frequency offset can be easily eliminated and the influence of the phase noise φ _Noise of the light source can be compensated. Moreover, not even appear affecting the demodulated signal as in the aging deterioration or temperature change for other reasons optical transmitter side of the apparatus omega _delta began variation. If ω _Δ is sufficiently larger than the signal band, it is also possible to suppress the factor of sin (ω _Δ t) by inserting an LPF (low-pass filter) into the outputs of V ₁ and V ₂ . The cutoff frequency of this LPF is set to be larger than the symbol rate of the optical modulation signal and smaller than ω _Δ .

<First Embodiment>
Next, the configuration of the optical QAM transmission system according to the first embodiment to which the above-described method is applied will be described. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, the same parts as those of the conventional apparatus shown in FIG. First, the CW light having the angular frequency ω _c generated by the CW light source 1 is split by the coupler 20.

The data signal modulation means 2 inputs one light divided by the coupler 20 and performs optical modulation to generate an optical QAM signal. The CS-RZ modulator 21 is driven by a sine wave having an angular frequency ω _RZ . By making an optical pulse train from the other light divided by the coupler 20 by optical modulation by the CS-RZ modulator 21, it is converted into two CW lights having an angular frequency of ω _c ± ω _RZ and output. The optical QAM signal that is the output of the data signal modulator 2 and the two CW lights that are the output of the CS-RZ modulator 21 are combined by the coupler 22. The optical fiber 3 transmits this combined light.

The duplexer 102 divides the light after transmission through the optical fiber 3 into two sets of ω _c and ω _c ± ω _RZ . The 90-degree hybrid 100 inside the optical receiver 4 inputs these two sets of light. The duplexer 102 can use a periodic optical filter such as an interleaver or an MZI interferometer.

  The photoelectric conversion unit 101 amplifies the output of the 90-degree hybrid 100 in the same manner as in the conventional technique, and demodulates it by the method described above. Since the periodic change in intensity in the CS-RZ modulator 21 is not essential, a double peak may be formed on the optical frequency axis by an optical phase modulator instead of the CS-RZ modulator 21.

Second Embodiment
Next, the configuration of the optical QAM transmission system according to the second embodiment will be described. FIG. 2 is a block diagram showing the configuration of the embodiment. In this figure, the same parts as those in the apparatus shown in FIG. In the configuration of the second embodiment illustrated in FIG. 2, ω _c and ω _c ± ω _Δ are generated by the multi-wavelength light source 110 instead of the CS-RZ modulator 21.

The demultiplexer 103 demultiplexes the generated multi-wavelength light into ω _c and ω _c ± ω _Δ . The data signal modulation means 2 receives the demultiplexed ω _c and performs optical modulation. The coupler 22 combines the demultiplexed ω _c ± ω _Δ and the output of the data signal modulation means 2. Since the processing operation after transmission by the optical fiber 3 is the same as that in the first embodiment, detailed description thereof is omitted here.

  The multi-wavelength light source 110 can be realized by using a nonlinear optical effect such as four-wave mixing. When three to four CW lights are generated from two CW lights by four-wave mixing, the frequency interval of each CW light is kept constant, so that the phase fluctuation of the light source is also shared by each CW light. For this reason, the effect similar to 1st Embodiment is acquired.

<Third Embodiment>
Next, the configuration of the optical QAM transmission system according to the third embodiment will be described. In the description of the above-described embodiment, the optical QAM transmission with a single polarization has been described as an example for the sake of simplicity. However, transmission using polarization-multiplexed optical QAM is also widely performed in order to increase the frequency utilization efficiency. It has been broken.

When performing polarization multiplexed optical QAM according to the present embodiment, it can be realized by introducing a polarization multiplexed IQ modulator in the optical transmitter. It is desirable that the local light is also polarization-multiplexed before the optical transmission. However, after the two sets of local light of ω _c ± ω _Δ or ω _c ± ω _RZ are polarization-multiplexed with themselves, the signal light is transmitted by the coupler 22. Just combine.

When generating a plurality of bright line spectrum of the local light in the CS-RZ modulator 21 as described in the first embodiment, the light pulse train of period [pi / omega _delta occurs, the local light and their own In the case of polarization multiplexing, interleaved polarization multiplexing may be performed by adding a time difference of π / (2ω _Δ ). That is, it is preferable to perform polarization multiplexing such that two optical pulse trains having orthogonal polarizations have the same maximum light intensity and the other light intensity minimum on the time axis. In ordinary 90-degree hybrids, a single polarization is often used as the local light, but when the single polarization is cut out from the polarization-multiplexed local light, interleaved polarization multiplexing must be performed. There is an advantage that a light intensity of 50% can be secured.

<Fourth embodiment>
Next, the configuration of the optical QAM transmission system according to the fourth embodiment will be described. FIG. 3 is a block diagram showing the configuration of the embodiment. In this figure, the same parts as those in the apparatus shown in FIG. In the first embodiment, two types of light modulation devices are used, one of which is used as the data signal modulation means 2, and the other one, the CS-RZ modulator 21, is used as the bright line spectrum generation means. The optical QAM transmission system according to the fourth embodiment is a combination of these two optical modulators into one IQ modulator 200.

In this configuration, in the drive signal of the IQ modulator 200, the clock component of ω _RZ is superimposed on a random signal having information on A _sig and φ _sig . Compared to the first embodiment, a wide band is required for the modulator drive system, but there is an advantage that the configuration on the transmitter side is simplified.

  As described above, on the transmitting side, two local lights having a frequency interval strictly maintained with respect to the carrier frequency of the optical QAM signal are generated and transmitted together with the optical QAM signal. Thus, both the frequency offset and the optical phase noise of the light source can be removed with a simple configuration without using a high-speed arithmetic device. In addition, since it is not necessary to prepare local light on the optical receiver side, the apparatus configuration and price of the optical receiver can be greatly reduced. The latter is particularly important in subscriber systems.

  This configuration is suitable for an optical transmitter and an optical receiver used in an optical transmission system using digital coherent demodulation, and particularly for a subscriber system that transmits / receives a QAM (Quadrature Amplitude Modulation) signal having a value higher than four values. Suitable for optical transceiver.

  As mentioned above, although embodiment of this invention has been described with reference to drawings, the said embodiment is only the illustration of this invention, and it is clear that this invention is not limited to the said embodiment. is there. Therefore, additions, omissions, substitutions, and other modifications of the components may be made without departing from the technical idea and scope of the present invention.

  The optical modulation apparatus and optical modulation method according to the present invention can be effectively applied in constructing an optical transmission system using an optical QAM signal, particularly an optical transmission system in a subscriber system.

  DESCRIPTION OF SYMBOLS 1 ... CW light source, 2 ... Data signal modulation means, 3 ... Optical fiber, 4 ... Optical receiver, 5 ... Local light source, 6 ... Signal light input terminal, 7 ..Local light-emitting input terminal, 8... 1st optical branch, 9... 2nd optical branch, 10... 3rd optical branch, 11. Optical delay circuit 13 ... first OE converter 14 ... second OE converter 15 ... third OE converter 16 ... fourth OE converter 17 ... first 1 differential amplifier, 18 ... second differential amplifier, 20 ... coupler, 21 ... CS-RZ modulator, 22 ... coupler, 100 ... 90 degree hybrid, 101 ... -Photoelectric conversion unit, 102 ... demultiplexer, 103 ... demultiplexer, 110 ... multi-wavelength light source, 200 ... IQ modulator

Claims (8)

A CW light source;
By modulating the output of the CW light source, a light modulation signal having a carrier frequency of ωc and a plurality of emission line spectra having an optical frequency of ωc ± nωΔ (where n is a natural number and ωΔ is an interval of angular frequencies of each emission line spectrum) Optical modulation means for generating and outputting
An optical transmitter having
A signal local oscillation separation means for separating an optical modulation signal having a carrier frequency of ωc and at least two types of bright line spectra having an optical frequency of ωc ± nωΔ from an optical signal transmitted from an optical transmission line;
A 90 degree hybrid for inputting the optical modulation signal and the bright line spectrum separated by the signal local oscillation separating means to the signal light input port and the local light input port,
Electrical conversion means for receiving and electrically converting the interference light output from the 90-degree hybrid;
Light transmission receiving device, characterized in that it comprises an optical receiver having a. A CW light source;
Light branching means for branching the output of the CW light source;
Data signal modulating means for modulating one of the outputs of the optical branching means to generate an optical modulation signal having a carrier frequency of ωc;
Emission line spectrum generating means for modulating the other of the outputs of the light branching means to generate a plurality of emission line spectra whose optical frequency is ωc ± nωΔ (n is a natural number, ωΔ is an interval of angular frequencies of each emission line spectrum);
A combining unit that combines the output of the data signal modulating unit and the output of the bright line spectrum generating unit and outputs the combined signal to an optical transmission line;
An optical transmitter having
A signal local oscillation separation means for separating an optical modulation signal having a carrier frequency of ωc and at least two types of bright line spectra having an optical frequency of ωc ± nωΔ from an optical signal transmitted from an optical transmission line;
A 90 degree hybrid for inputting the optical modulation signal and the bright line spectrum separated by the signal local oscillation separating means to the signal light input port and the local light input port,
Electrical conversion means for receiving and electrically converting the interference light output from the 90-degree hybrid;
Light transmission receiving device, characterized in that it comprises an optical receiver having a. Multi-wavelength light generating means for generating a plurality of CW lights having equal frequency intervals;
Data signal modulation means for demultiplexing and modulating at least one of the CW lights output from the multi-wavelength light generation means to generate an optical modulation signal having a carrier frequency of ωc;
At least two CW lights having an optical frequency of ωc ± nωΔ (n is a natural number, and ωΔ is an angular frequency interval of the multiwavelength light generating means) among the CW lights output from the multiwavelength light generating means are demultiplexed. Bright line spectrum generating means;
A combining unit that combines the output of the data signal modulating unit and the output of the bright line spectrum generating unit and outputs the combined signal to an optical transmission line;
An optical transmitter having
A signal local oscillation separation means for separating an optical modulation signal having a carrier frequency of ωc and at least two types of bright line spectra having an optical frequency of ωc ± nωΔ from an optical signal transmitted from an optical transmission line;
A 90 degree hybrid for inputting the optical modulation signal and the bright line spectrum separated by the signal local oscillation separating means to the signal light input port and the local light input port,
Electrical conversion means for receiving and electrically converting the interference light output from the 90-degree hybrid;
Light transmission receiving device, characterized in that it comprises an optical receiver having a. The multi-wavelength light generating means includes at least two types of CW light sources and an optical waveguide,
The optical waveguide receives the output of the CW light source,
The optical waveguide is an optical transmission receiver device according to claim 3, characterized in that outputs at least three kinds of CW light by four-wave mixing. Light transmission receiving apparatus according to claim 2 or 3, at least one, characterized in that it is polarization multiplexed with the output of the output and the bright line spectrum generating unit of the data signal modulating means. An optical modulation signal having a carrier frequency of ωc and an optical frequency of ωc ± nωΔ (where n is a natural number and ωΔ is an angular frequency interval of each emission line spectrum) from an optical signal transmitted from an optical transmission line. A signal local separation means for separating the emission line spectrum;
A 90 degree hybrid for inputting the optical modulation signal and the bright line spectrum separated by the signal local oscillation separating means to the signal light input port and the local light input port,
An optical receiver comprising: electrical conversion means for receiving and electrically converting interference light output from the 90-degree hybrid. A low pass filter that cuts off high frequency components from the output of the electrical conversion means,
The optical receiver according to claim 6, wherein a cutoff frequency of the low-pass filter is larger than a symbol rate of the optical modulation signal and smaller than ωΔ. An optical transmitter including a CW light source, an optical branching unit, a data signal modulating unit, an emission line spectrum generating unit, and a multiplexing unit, a signal local oscillation separating unit, a 90-degree hybrid, and an electrical conversion unit. An optical transmission / reception method performed by an optical communication system including an optical receiver,
An optical branching step in which the optical branching means branches the output of the CW light source;
A data signal modulation step in which the data signal modulation means modulates one of the outputs of the optical branching means to generate an optical modulation signal having a carrier frequency ωc;
The bright line spectrum generating means modulates the other of the outputs of the light branching means to generate a plurality of bright line spectra having an optical frequency of ωc ± nωΔ (n is a natural number, and ωΔ is an angular frequency interval of each bright line spectrum). A bright line spectrum generation step,
The multiplexing unit combines the output of the data signal modulation unit and the output of the bright line spectrum generation unit and outputs to the optical transmission line;
The signal station generating and separating means separates the optical modulation signal having a carrier frequency of ωc and the plurality of emission line spectra having an optical frequency of ωc ± nωΔ from the optical signal transmitted from the optical transmission line. A separation step;
A 90-degree hybrid step in which the 90-degree hybrid inputs the optical modulation signal and the bright line spectrum separated by the signal local oscillation separating means to the signal light input port and the local light input port, respectively;
An electrical transmission and reception method, wherein the electrical conversion means includes an electrical conversion step of receiving and electrically converting the interference light output from the 90-degree hybrid.

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