JP2010135937A - Polarization modulator, optical transmitter/receiver, and light transmission system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform failure determination using a tone modulation signal in order to increase a number of nodes. <P>SOLUTION: This invention includes an optical transmitter and an optical receiver. The optical transmitter has: N units of main signal transmission means; N units of tone modulation signal generation means which generate tone modulation signals of different frequencies; a polarization modulation means which performs polarization modulation of main signals output from respective main signal transmission means by respective tone modulation signals of different frequencies in order to superimpose the tone modulation signals; and a wavelength multiplexing means which performs wavelength multiplexing of the superimposed main signals. The optical receiver has: a wavelength division means which receives a wave length multiplexing signal from the optical transmitter, and performs wavelength division for one of the branched wavelength multiplexed signal; a main signal reception means which receives the separated main signal; a polarization extraction means which extracts a specified polarization component from another branched tone modulation signal; an O/E means which converts the polarization component to an electrical signal; and a tone modulation signal extraction means which extracts N units of tone modulation signals from the electrical signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarization modulator, an optical transceiver, and an optical transmission system using the same, and particularly, in a transparent optical network, monitors a failure due to a node on an optical network or a fiber break using a tone modulation signal. The present invention relates to a polarization modulator, an optical transceiver, and an optical transmission system using the same.

  Conventionally, an optical network monitoring method by superimposing a tone modulation signal on a main signal has been proposed. As a conventional method of superimposing a tone signal, there is intensity modulation (phase modulation) (see, for example, Patent Document 1).

  FIG. 15 shows a monitoring system using conventional intensity modulation.

  In the system shown in the figure, the transmission node 1 is connected to the relay node 2, and the reception node 4 is connected to the relay node 3.

  The transmission node 1 has an optical transmitter 10, and the reception node 4 has an optical receiver 40.

  The optical receiver 10 modulates the intensity of the tone modulation signal input from the main signal transmitter 11 that transmits the main signal, the tone modulation signal generator 13 that generates the tone modulation signal, and the tone modulation signal generator 13. It comprises an intensity modulator 12 that is superimposed on the main signal input from the signal transmitter 11 and output onto the optical fiber.

The optical receiver 40 includes a demultiplexer 41 that demultiplexes the optical signal received from the optical transmitter 10, a main signal receiver 43 that receives the optical signal demultiplexed by the demultiplexer 41, and a demultiplexer 41. The optical-electrical converter 42 that converts the optical signal demultiplexed in step 1 into an electrical signal, and the tone modulation signal extractor 44 that extracts the tone modulation signal from the converted electrical signal.
Japanese Patent Laid-Open No. 10-107772

  However, in the intensity modulator in the optical transmitter of the conventional system shown in FIG. 14, there is a problem that if the modulation degree of the tone modulation signal is increased, the influence on the main signal is increased.

  On the other hand, in order to reduce the influence on the main signal, if the modulation degree is set to several percent or less, the optical signal-to-noise ratio is severely limited, so the number of nodes that can be monitored is reduced, and a high dynamic range is provided on the optical receiver side. A low noise opto-electric converter is required.

  The present invention has been made in view of the above points, and in a transparent optical network, when performing failure determination using a tone modulation signal using polarization modulation, the number of nodes that can be monitored is increased, It is another object of the present invention to provide a polarization modulator, an optical transmitter / receiver, and an optical transmission system using the same, which are capable of monitoring failure using tone modulation capable of reducing the cost.

  FIG. 1 is a principle configuration diagram of the present invention.

The present invention (Claim 1) includes polarization splitting means 121 for splitting input light into two polarizations of P polarization and S polarization,
Phase modulation means for phase-modulating one of P-polarized light and S-polarized light using a tone modulation signal generator;
The polarization modulator 120 includes polarization combining means 122 that combines light that has not been converted into phase-modulated light using the phase modulation means.

The present invention (Claim 2) includes a light source and branching means for branching the light of the light source into two parts,
Two signal modulation means for independently modulating the bifurcated light into signal light;
An optical transmitter comprising phase modulation means for phase-modulating one of the two signal lights using a tone modulation signal generator.

The present invention (Claim 3) is an optical transmission means for arranging two or more optical transmission means according to claim 2 using a plurality of wavelengths in an optical signal in parallel, and wavelength-multiplexing and outputting them in a wavelength multiplexing section. And
It is a wavelength multiplexed polarization modulated optical transmitter that is tone modulated at two or more different frequencies.

The present invention (Claim 4) includes wavelength multiplexing means for wavelength-multiplexing optical signals of two or more wavelengths, and
Polarization separation means for separating the wavelength-multiplexed light into P-polarized light and S-polarized light;
Wavelength demultiplexing means for separating P-polarized light and S-polarized light for each wavelength;
Tone modulation means for tone-modulating one of the P-polarized light and the S-polarized light of the signal light separated and polarized by the polarization separation means and the wavelength demultiplexing means at two or more different frequencies;
Wavelength multiplexing means for wavelength-multiplexing polarized light that is tone-modulated and polarized light that is not modulated;
Polarization combining means for combining wavelength multiplexed light with polarization;
Is a wavelength division multiplexing polarization modulation optical transmitter.

The present invention (Claim 5) includes branching means for branching the wavelength multiplexed polarization modulated light transmitted by the wavelength multiplexed polarization modulated optical transmitter according to claim 3 or 4 into two,
In order to extract a tone modulation frequency component from one of the wavelength multiplexed polarization modulated light branched by the branching means, a polarizer, an optical-electric converter, and a frequency extraction means for extracting the tone modulation frequency component; Prepared,
This is a wavelength multiplexing polarization-modulated optical receiver including an optical receiving unit that wavelength-separates the other light branched by the branching unit by the wavelength demultiplexing unit and receives an optical signal for each separated wavelength.

  The present invention (Claim 6) includes the wavelength division multiplexing polarization optical transmitter according to any one of Claims 2, 3, and 4 and the wavelength division multiplexing polarization optical receiver according to Claim 5. This is an optical transmission system.

  As described above, according to the present invention, when the tone modulation signal is modulated, the modulation degree can be increased by using the polarization modulation without using the intensity modulation, so that the number of nodes is increased. It is possible. As a result, the performance condition of the optical-electrical converter is relaxed on the receiver side, and the cost can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 2 is a configuration diagram of a monitoring system using tone modulation according to the first embodiment of the present invention.

  The system shown in FIG. 1 includes a transmission side node 1, a plurality of relay nodes 2 and 3, and a reception node 4.

  The transmission node 1 connected to the relay node 2 includes an optical transmitter 100, and the optical transmitter 100 includes a main signal transmitter 110, a polarization modulator 120, and a tone modulation signal generator 130. The main signal transmitter 110 outputs the main signal to the polarization modulator 120, and the tone modulation signal generator 130 outputs the tone modulation signal to the polarization modulator 120. As a result, the polarization modulator 120 modulates the main signal based on the tone modulation signal from the tone modulation signal generator 130 and outputs the result.

  The optical receiver 200 of the receiving node 4 connected to the relay node 3 includes a branching unit 210 that demultiplexes an optical signal input via the relay node 3, and a polarizer that extracts polarized light from one of the demultiplexed optical signals. 220, an optical-electrical converter 230 for converting the extracted polarized light into an electric signal, a tone modulation signal extractor 250 for extracting a tone modulation signal from the electric signal, and the other optical signal demultiplexed by the branching unit 210 Main signal receiver 260.

  FIG. 3 shows a detailed configuration example of the optical transmitter 100 in the transmission method in which two main signals are polarization multiplexed in the first embodiment of the present invention.

  The main signal transmission unit 108 modulates one of the demultiplexed signals, a CW (Continuous Wave) light source 111 that is a light source that emits light continuously, a branching device 112 that demultiplexes the optical signal from the CW light source 111 into two. It comprises a polarizer 113 that outputs P-polarized light to the polarization modulator 109 and a polarizer 114 that modulates one of the demultiplexed signals and outputs S-polarized light to the polarization modulator 109.

When the S-polarized light from the polarizer 114 and the tone modulation signal from the tone modulation signal generator 130 are input to the polarization modulator 109, the polarization modulator 109 superimposes the tone modulation signal on the S-polarized light and outputs the phase modulator 121. It comprises a polarization multiplexer 122 that combines the P-polarized light input from the modulator 113 and the phase-modulated optical signal input from the phase modulator 121 and outputs the resultant signal. The polarization modulator 109 can be realized by a PLC (Planar Lightwave Circuit), LiNbO ₃ or the like. In the case of PLC, the thermo-optic effect can be used in the phase modulator 121. In the case of LiNbO ₃ , the electro-optic effect can be used.

  FIG. 4 is a diagram showing the influence (power penalty) on the main signal in the conventional tone modulation and the polarization tone modulation of the present invention. In the case of intensity and phase modulation, the main signal that increases the modulation degree deteriorates rapidly. On the other hand, by using polarization tone modulation, the modulation degree can be set high at an arbitrary modulation frequency. Therefore, the number of nodes can be increased.

  FIG. 5 shows a configuration (part 1) of a WDM (Wavelength Division Multiplexing) optical transmitter according to the first embodiment of the present invention. A WDM optical transmitter 100A shown in the figure is an example when wavelength multiplexing (WDM) is performed by an optical transmitter.

  The WDM optical transmitter 100A includes N (N is a natural number) main signal transmitters 110, N polarization modulators 120, a tone modulation signal generator 130, and a wavelength multiplexing unit 140.

  The N main signal generators 110 output main signals having different wavelengths to the respective polarization modulators 120, and the tone modulation signal generator 130 outputs different tone modulation signals to the respective polarization modulators 120. In each polarization modulator 120, a main signal having a different wavelength is subjected to polarization modulation with a different tone modulation signal, whereby different tone frequencies can be assigned to the main signal. N main signals on which tone modulation signals are individually superimposed are multiplexed in the wavelength region by the wavelength multiplexing unit 140 and output.

  A WDM optical receiver that receives a wavelength multiplexed signal from the WDM optical transmitter 100A will be described.

  In the system of FIG. 5 described above, in the optical transmitter 100A, tone modulation signals having different frequencies are assigned to each of N main signals having different wavelengths by polarization modulation, and then wavelength-multiplexed and transmitted. , N tone frequency modulated signals are extracted at once. As a result, even in an optical network in which the main signals of a plurality of channels are wavelength-multiplexed and transferred, the main signal of the failed channel can be identified by evaluating the tone frequency component.

  FIG. 6 shows a configuration of a WDM optical receiver according to the first embodiment of the present invention.

  The WDM optical receiver 200 shown in FIG. 1 includes a branching unit 210 that branches an optical signal, a polarizer 220 that extracts a specific polarization component from one of the branched optical signals, and a light that converts the extracted polarized light into an electrical signal. An electrical converter 230; a tone modulation signal extractor 250 that extracts N tone modulation signals from the electrical signal; a wavelength demultiplexer 240 that demultiplexes the other optical signal demultiplexed by the branching unit 210 in a wavelength region; The main signal receiver 260 includes N main signal receivers 260 that respectively receive the wavelength-demultiplexed optical signals.

  FIG. 7 shows the configuration (part 2) of the WDM optical transmitter according to the first embodiment of the present invention.

  The WDM optical transmitter 100B shown in the figure includes N light sources 115, a wavelength multiplexing unit 140, a tone modulation signal generator 130, and a multi-wavelength polarization modulator 150.

  N main signals of different wavelengths output from the N light sources 115 are multiplexed in the wavelength region by the wavelength multiplexing unit 140 and output to the multi-wavelength polarization modulator 150. The tone modulation signal generator 130 outputs N tone modulation signals having different frequencies to the multi-wavelength polarization modulator 150. Multi-wavelength polarization modulator 150 performs polarization modulation with different tone modulation signals on N different main signals having different wavelengths, and assigns different tone frequencies to the respective main signals. The multi-wavelength polarization modulator 150 outputs a wavelength multiplexed main signal on which tone modulation signals of different frequencies are superimposed for each channel.

  The configuration of the WDM optical transmitter 100B in FIG. 7 is characterized in that, in the multi-wavelength polarization modulator 150, tone modulation signals having different frequencies are assigned by polarization modulation for each channel of the wavelength multiplexed signal.

  Hereinafter, the multi-wavelength polarization modulator 150 will be described.

  FIG. 8 shows the configuration of the multi-wavelength polarization modulator according to the first embodiment of the present invention. FIG. 3A shows a configuration viewed from the side, and FIG. 4B shows a configuration viewed from above.

  The multi-wavelength polarization modulator 150 includes an optical circulator 151, a polarization demultiplexer / synthesizer 152, a wavelength demultiplexer / multiplexer 153, a phase modulator array 154, a reflection unit 155, and a tone modulation signal generator 156. The A wavelength multiplexed signal is input from the wavelength multiplexing unit 140 from the input port of the optical circulator 151 and output from the common port of the optical circulator 151 to the polarization beam splitter / multiplexer 152. After being separated into two orthogonal linearly polarized lights (P-polarized light and S-polarized light) in the polarization separation / multiplexer 152, they are separated in the wavelength region by the wavelength demultiplexing / multiplexer 153. The wavelength-separated P-polarized light (or S-polarized light) is output to the phase modulator array 154, and the wavelength-separated S-polarized light (or P-polarized light) is output to the reflecting unit 155. The phase modulator array 154 is an array of phase modulators for the wavelengths (λ1, λ2,..., ΛN) of each channel. In each phase modulator, the P-polarized light (or S-polarized light) of each channel. Are modulated by the tone modulation signal from the tone modulation signal generator 156 and reflected. The P-polarized light (or S-polarized light) reflected by the phase modulation by the phase modulator array 154 and the S-polarized light (or P-polarized light) reflected by the reflection unit 155 are wavelength-multiplexed by the wavelength demultiplexer / multiplexer 153 to separate the polarized light After polarization multiplexing by the multiplexing unit 152, the light is guided to the common port of the optical circulator 151. The optical signal input from the common port of the optical circulator 151 is output from the output port. In all phase modulators, by modulating the phase at the tone modulation frequency, a phase difference is produced between the P-polarized light and the S-polarized light, and the polarization of the signal light of all the polarization-combined channels is modulated at the tone modulation frequency. Can do.

  FIG. 9 shows the configuration (part 3) of the WDM optical transmitter according to the first embodiment of the present invention.

  The WDM optical transmitter 100 </ b> C shown in FIG. 1 includes N light sources 115, a tone modulation signal generator 130, and a wavelength multiplexing / polarization modulator 160. N optical signals (main signals) of different wavelengths output from the N light sources 115 are output to the wavelength multiplexing / polarization modulator 160. The tone modulation signal generator 130 outputs N tone modulations having different frequencies to the wavelength division multiplexing / polarization modulator 160. In the wavelength division multiplexing / polarization modulator 160, polarization modulation is performed on each of N main signals having different wavelengths by using a different tone modulation signal, and a different tone frequency is assigned to each main signal. Each main signal on which the tone modulation signal is superimposed is wavelength-multiplexed and output.

  The WDM optical transmitter 100C of FIG. 9 is characterized in that, in the wavelength multiplexing / polarization modulator 160, tone modulation having different frequencies for each channel is allocated by polarization modulation and then wavelength-multiplexed and output.

  The wavelength multiplexing / polarization modulator 160 will be described.

  FIG. 10 is a configuration example (No. 2) of the multi-wavelength polarization modulator according to the first embodiment of the present invention.

  FIG. 2A shows the configuration viewed from the side, and FIG. 2B shows the configuration viewed from above. The multi-wavelength polarization modulation 160 shown in the figure includes a wavelength multiplexing / demultiplexing device 161, a polarization demultiplexing / multiplexing device 162, a wavelength demultiplexing / multiplexing device 163, a phase modulator array 164, a reflection unit 165, and tone modulation. It consists of a signal generator 166.

  Wavelength multiplexed signals from the N main signal generators 110 are multiplexed by the wavelength multiplexing / demultiplexing unit 161 and output to the polarization separation / multiplexing unit 162. After being separated into two orthogonal linearly polarized light (P-polarized light and S-polarized light) in the polarization separation / multiplexer 162, the light is separated in the wavelength region by the wavelength demultiplexing / multiplexer 163. The wavelength-separated P-polarized light (or S-polarized light) is output to the phase modulator array 164, and the wavelength-separated S-polarized light (or P-polarized light) is output to the reflecting unit 165. The phase modulator array 164 is an array of phase modulators for the wavelengths (λ1, λ2,..., ΛN) of each channel. In each phase modulator, the P-polarized light (or S) of each channel is arranged. The phase of the polarized light is modulated by the tone modulation signal from the tone modulation signal generator 166 and reflected. The P-polarized light (or S-polarized light) phase-modulated and reflected by the phase modulator array 164 and the S-polarized light (or P-polarized light) reflected by the reflector 165 are wavelength-multiplexed by the wavelength demultiplexer / multiplexer 163 to be polarized and separated. Polarization multiplexing is performed by the multiplexer 162. By adjusting the reflection angle at the phase modulator array 164 and the reflection unit 165, the signal light from the polarization multiplexing is guided to the output port. As with the multi-wavelength polarization modulator 150 described above, in all phase modulations, the phase is modulated at the tone modulation frequency, so that a phase difference occurs between the P-polarized light and the S-polarized light, and all the channels that are polarized and combined The polarization of the signal light can be modulated with the tone modulation frequency.

  Specifically, a modulator array using liquid crystal can be used as the phase modulator array 154 of the multi-wavelength polarization modulator 150 and the phase modulator array 164 of the wavelength multiplexing / polarization modulator 160.

  The receiver has the same configuration as that shown in FIG.

<Second Embodiment>
FIG. 11 is a node configuration diagram to which tone modulation is applied according to the second embodiment of the present invention.

  The node 500 shown in the figure is assumed to have the same configuration on both the transmission side and reception side nodes.

  The node 500 is provided on the input side, and is provided on the output side, an optical coupler 510 that demultiplexes the optical signal from the path, a distribution optical coupler 530 that is connected to the optical transmitter 100 via the wavelength multiplexing means 501, and the output side. The optical coupler 510 from the input side and the WSS 520 that selects and outputs the optical signal from the distribution optical coupler 530 are configured.

  The polarization modulator 120 connected to the add port is provided at the position a if the output destinations of the respective routes are the same, and is provided at the position b when the output destinations of the respective routes are different. Further, the branching device 210, the polarizer 220, the optical-electrical converter 230, and the tone bias signal extractor 250 connected to the drop port are provided at the position c or the position d.

  An optical transmitter 100 having the configuration shown in FIG. 3 is connected to the optical coupler 530 connected to the add port via the wavelength multiplexing means 501, and the light on which the tone modulation signal input from the polarization modulator 120 is superimposed. The signal is output to WSS 520a and 520b.

  The optical receiver 200 having the configuration shown in FIG. 2 is connected to the WSS 520c connected to the drop port via the wavelength demultiplexing unit 502, and the optical signals input from the input-side optical couplers 510a and 510b are converted into wavelengths. Select and output to the optical receiver 200.

  A description will be given of a case where the polarization modulator 120 is connected to the position a when the node 500 functions as a transmission-side node.

The optical signal transmitted from the optical transmitter 100 is wavelength-multiplexed by the wavelength multiplexing unit 501, and the tone modulation signal is superimposed by the polarization modulator 120 arranged at the position a and input to the optical coupler 530. . The optical coupler 530 demultiplexes the optical signal and outputs it to the WSS 520a and WSS 520b on the output side. Thereby, WSS520a and WSS520b select a wavelength based on control from a management control function part (not shown), and output it to route 1 and route 2, respectively.
Next, a case where the polarization modulator 120 is connected to the position b (wavelength multiplexing unit 501 connected to the add port) will be described.

  The optical signal on which the tone modulation signal is superimposed is input from the polarization modulator 120 of the optical transmitter 100 connected to the add port to the wavelength combining unit 501, and is combined with the wavelength and input to the optical coupler 530. The optical coupler 530 demultiplexes the optical signal and outputs it to the WSS 520a and WSS 520b on the output side. Thereby, WSS520a and WSS520b select a wavelength based on control from a management control function part (not shown), and output it to route 1 and route 2, respectively.

  A case where the optical receiver 200 is connected to the position c when the node 500 functions as a receiving node will be described.

  Each of the optical couplers 510a and 510b receives the optical signal on which the node modulation signal is superimposed, which is input from each of the paths 1 and 2, and splits it to the WSS 520a and WSS 520b on the output side and the WSS 520c connected to the drop port. Wave and output. The WSS 520c selects a wavelength based on control from a management control function unit (not shown) and outputs it to the drop port. As a result, the optical signal is input to the optical receiver 200 connected to the drop port. The tone modulation signal extractor 250 of the optical receiver 200 extracts the tone modulation signal superimposed on the optical signal, and determines whether there is a failure.

  A case where the optical receiver 200 is connected to the position d will be described.

  Each of the optical couplers 510a and 510b receives the optical signal on which the node modulation signal is input, which is input from each of the paths 1 and 2, and distributes the optical signal to the WSS 520a and WSS 520b on the output side and the WSS 520c connected to the drop port. Wave and output. The WSS 520 selects a wavelength based on control from a management control function unit (not shown) and outputs it to the drop port. As a result, the optical signal demultiplexed by the wavelength demultiplexing means 502 connected to the drop port is input to the optical receiver 200. The tone modulation signal extractor 250 of the optical receiver 200 extracts the tone modulation signal superimposed on the optical signal, and determines whether there is a failure.

<Third Embodiment>
In this embodiment, an example is shown in which a polarization scrambling modulator is used as an optical transmitter and an electrical dispersion compensator (EDC) is used as an optical receiver.

  As a transmission method for compensating for polarization dispersion, a method in which polarization scrambling and an electrical dispersion compensator (EDC) are combined has been reported (for example, see E. Yoshida, ECOE2007, 3.1.3, 20007). . An example of this is shown in FIG.

  The system shown in FIG. 1 includes an optical transmitter 50 connected to the transmission side node 20 and an optical receiver 60 connected to the reception side node 30.

The optical transmitter 50 includes a main signal transmitter 51 that transmits a main signal, and a polarization scrambling modulator 52 that polarization scrambles the signal input from the main signal transmitter 51 and outputs the signal onto an optical fiber. The This configuration is realized using LiNbO ₃ (lithium niobate single crystal) or a wave plate.

  The optical receiver 60 connected to the receiving side node 30 includes an optical-electrical converter 61 that converts an optical signal into an electrical signal, an EDC 62 that compensates for dispersion of a transmission line at an electrical stage, and an electrical signal input from the EDC 62. It is comprised from the signal processing part 63 which processes.

  FIG. 13 shows a system configuration in the third embodiment of the present invention.

  The system shown in the figure includes a transmission side node 20, a reception side node 30, an optical transmitter 600 connected to the transmission side node 20, and an optical receiver 700 connected to the reception side node 30.

  The optical transmitter 600 includes a main signal transmitter 610, a polarization scrambling modulator 620, and a tone modulation signal generator 630. Main signal transmitter 610 outputs the main signal to polarization scrambling modulator 620, and tone modulation signal generator 630 outputs the tone modulation signal to polarization modulator 620. Thereby, the polarization scrambling modulator 620 scrambles the main signal with the tone modulation signal superimposed thereon.

  The optical receiver 700 includes an optical demultiplexer 705, an optical-electrical converter 710, an EDC 720, a signal processing unit 730, a polarizer 740, an optical-electrical converter 750, and a tone modulation signal extractor 760.

  When an optical signal is input to the receiving side node 30, the optical signal is branched into two by the optical demultiplexer 705, and one is converted into an electric signal by the optical-electrical converter 710 and output to the EDC 720. The other side of the light demultiplexed by the optical demultiplexer 705 is output to the polarizer 740. The EDC 720 performs waveform shaping of the input electric signal and then outputs the signal to the signal processing unit 730.

  In the polarizer 740 to which the other output of the optical demultiplexer 705 is input, a specific polarization component is extracted and output to the opto-electric converter 750.

  The light-electric converter 750 converts the signal into an electric signal, and the tone modulation signal extractor 760 extracts the tone modulation signal.

  Also in this embodiment, the optical transmitter 600 is connected to the add port of FIG. 11 or the wavelength multiplexing means 501 connected to the add port, and the optical receiver 700 is connected to the drop port or the drop port. It is possible to connect to the wavelength demultiplexing means 502.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made within the scope of the claims.

  The present invention is applicable to a failure monitoring system in a transparent optical network.

It is a principle block diagram of this invention. It is a block diagram of the monitoring system using the tone modulation in the 1st Embodiment of this invention. It is a detailed block diagram of the optical transmitter in the transmission system which carries out the polarization multiplexing of the two main signals in the 1st Embodiment of this invention. It is a figure which shows the influence (power penalty) to the main signal in the polarization tone modulation in the 1st Embodiment of this invention. It is a block diagram (the 1) of the WDM optical transmitter in the 1st Embodiment of this invention. It is a block diagram of the WDM optical receiver in the 1st Embodiment of this invention. It is a block diagram (the 2) of the WDM optical transmitter in the 1st Embodiment of this invention. It is a structural example (the 1) of the multiwavelength polarization modulator in the 1st Embodiment of this invention. It is a block diagram (the 3) of the WDM optical transmitter in the 1st Embodiment of this invention. It is a structural example (the 2) of the wavelength division multiplexing and polarization modulator in the 1st Embodiment of this invention. It is a node block diagram which applied the tone modulation in the 2nd Embodiment of this invention. It is an example of the system which combined polarization scrambling and EDC. It is a system block diagram in the 3rd Embodiment of this invention. It is an example of the wavelength division multiplexing polarization modulation transmitter using the polarization scrambler in the 3rd Embodiment of this invention. It is a system block diagram which monitors using the conventional intensity | strength modulation | alteration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission node 2 and 3 Relay node 4 Reception node 10 Optical transmitter 11 Main signal transmitter 12 Intensity modulator 13 Tone modulation signal generator 20 Transmission side node 30 Reception side node 40 Optical receiver 41 Demultiplexer 42 Optical-electricity Converter 43 Main signal receiver 44 Tone modulation signal extractor 50 Optical transmitter 51 Main signal transmitter 52 Polarization scrambling modulator 60 Optical receiver 61 Optical-electric converter 62 EDC
63 Signal processing unit 100 Optical transmitter 108 Main signal transmission unit 109 Polarization modulation unit 110 Main signal transmitter 111 CW light source 112 Branch units 113 and 114 Polarizer 115 Light source 120 Polarization modulator 121 Phase modulator 122 Polarization multiplexing 125 Polarization scrambler 130 Tone modulation signal generator 140 Wavelength multiplexer 150 Multi-wavelength polarization modulator 151 Optical circulator 152 Polarization separator / synthesizer 153 Wavelength demultiplexer / multiplexer 154 Phase modulator array 155 Reflector 156 Tone Modulation signal generator 160 Wavelength multiplexing / polarization modulator 161 Wavelength multiplexing / demultiplexer 162 Polarization demultiplexing / multiplexer 163 Wavelength demultiplexing / multiplexer 164 Phase modulator array 165 Reflector 166 Tone modulation signal generator 200 Optical reception 210 210 Separator 220 Polarizer 230 Opto-electric converter 240 Wavelength demultiplexer 250 Tone modulation signal Can 260 main signal receiver 500 node 501 wavelength multiplexing means 502 wavelength demultiplexing means 510 optical coupler 520 WSS (wavelength selective switch)
530 Optical coupler for distribution 600 Optical transmitter 610 Main signal transmitter 620 Polarization scrambling modulator 630 Tone modulation signal generator 700 Optical receiver 705 Optical demultiplexer 710 Optical-electric converter 720 EDC
730 Signal processor 740 Polarizer 750 Opto-electric converter 760 Tone modulation signal extractor

Claims (6)

A polarization splitting means for splitting the input light into two polarizations of P polarization and S polarization orthogonal to each other;
Phase modulation means for phase-modulating one of P-polarized light and S-polarized light using a tone modulation signal generator;
Polarization combining means for polarization combining light that has not been phase-modulated using the phase modulation means;
A polarization modulator characterized by comprising: A light source and branching means for branching light from the light source into two;
Two signal modulation means for independently modulating the bifurcated light into signal light;
Phase modulation means for phase-modulating one of the two signal lights using a tone modulation signal generator;
An optical transmitter comprising: The optical transmission means according to claim 2, wherein two or more wavelengths are used for an optical signal, arranged in parallel, and wavelength-multiplexed by a wavelength multiplexing section and output,
2. A wavelength-division-multiplexed polarization-modulated optical transmitter that is tone-modulated at two or more different frequencies. Wavelength multiplexing means for wavelength multiplexing optical signals of two or more wavelengths,
Polarization separation means for separating the wavelength-multiplexed light into P-polarized light and S-polarized light;
Wavelength demultiplexing means for separating the P-polarized light and the S-polarized light for each wavelength;
Tone modulation means for tone-modulating one of P-polarized light and S-polarized light of the signal light that has been wavelength-separated and polarization-demultiplexed by the polarization separation means and the wavelength demultiplexing means at two or more different frequencies; ,
Wavelength multiplexing means for wavelength multiplexing the tone-modulated polarized light and the unmodulated polarized light;
Polarization combining means for combining the wavelength-multiplexed light with polarization;
A wavelength division multiplexing polarization-modulated optical transmitter. Branch means for branching the wavelength multiplexed polarization modulated light transmitted by the wavelength multiplexed polarization modulated light transmitter according to claim 3 or 4 into two;
In order to extract a tone modulation frequency component from one wavelength-division-multiplexed polarization modulated light branched by the branching means, a polarizer, an optical-electric converter, and a frequency extraction means for extracting the tone modulation frequency component; With
A wavelength-division-multiplexed polarization-modulated optical receiver comprising optical receiving means for wavelength-separating the other light branched by the branching means by wavelength demultiplexing means and receiving an optical signal for each separated wavelength .   An optical transmission system comprising: the wavelength division multiplexing polarization optical transmitter according to claim 2; and the wavelength division multiplexing polarization optical receiver according to claim 5.

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