JP4447192B2 - PMD detector and wavelength division multiplexing optical transmission system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a PMD detector that detects a polarization mode dispersion characteristic that degrades the quality of a transmission signal in a wavelength division multiplexing optical transmission system that performs ultrahigh-speed optical transmission, and a wavelength division multiplexing optical transmission system that has a PMD compensation function. is there.
[0002]
[Prior art]
When light travels through materials having different refractive indexes, the propagation speed of light in the material varies depending on the refractive index. In addition, in the propagation of light in materials (anisotropic materials) having different refractive indices depending on the polarization direction of incident light, a phenomenon occurs in which the delay time after passing through the material varies depending on the state of polarization in the material. . Here, the delay time difference generated in the light polarized in each intrinsic polarization direction in the material is referred to as polarization mode dispersion (hereinafter referred to as “PMD” (Polarization Mode Dispersion)).
[0003]
In general, a single mode fiber used in an optical transmission line has a slight anisotropy locally along its longitudinal direction. Therefore, when light propagates in such an anisotropy fiber, there is a delay difference depending on the polarization direction of the optical signal at the location where the refractive index anisotropy exists in the propagation path. Arise. If the delay difference due to the difference in polarization is accumulated in the optical transmission path, the signal waveform at the receiving end is degraded.
[0004]
FIG. 6 is a diagram showing the relationship between the PMD size of an optical transmission line that causes a 1 dB penalty in optical transmission of an NRZ (Non-Return to Zero) signal whose pulse width is equal to the pulse interval, and the optical transmission speed (bit rate). is there. The relationship shown in FIG. 6 is described in the document “Fading in lightwave systems due to polarization-mode dispersion” (CD Poole, RW Tkach, AR Chraplyvy and DA Fishman, IEEE Photonics Technol. Lett. Vol.3, no.1, pp.68-70, 1991).
[0005]
That is, in the above document, the relationship between the PMD magnitude Δτ when the power penalty is deteriorated by 1 dB and the pulse width T of the NRZ signal (T = 1 / B: B is a bit rate) is expressed by the following equation (1). As shown. That is, Δτ / T˜0.4 (1). Based on this equation (1), when the relationship between the PMD magnitude Δτ when the power penalty is degraded by 1 dB and the bit rate B of the NRZ signal is obtained, the result shown in FIG. 6 is obtained. For example, when transmitting an NRZ signal of 40 Gbit / s, it can be seen that the PMD of the transmission path must be suppressed to 10 ps or less.
[0006]
On the other hand, in an actual transmission path, PMD having an average of about 0.1 ps / √km exists even with a low PMD fiber. This indicates that 10 ps PMD occurs after 10,000 km transmission. Furthermore, the PMD in the transmission path has a characteristic that its size varies with time. Therefore, after laying the optical fiber, it is necessary to perform PMD compensation according to the PMD temporal variation.
[0007]
When PMD compensation is performed according to time variation, a highly accurate PMD detection method that follows time variation is required. Also, when considering mounting on a transmission system, miniaturization of the PMD detector is required.
[0008]
As a PMD detection method that can follow a time variation and perform high-accuracy measurement, for example, a Jones matrix (Jones Matrix) disclosed in Japanese Patent Application Laid-Open No. H5-273082 (polarization mode dispersion determination device and method of an optical device) is disclosed. ) Law is best known. In the Jones Matirix method, the PMD size is obtained by calculation from the ellipsometric results for a small number of wavelengths, so that high-speed and high-precision PMD detection is possible. Furthermore, since PMD detection is performed by calculation, it is suitable for downsizing the PMD detector.
[0009]
As other means for detecting PMD based on ellipsometry, the Poincare sphere method, the SOP method, and the FA (fixed analyzer) method are known. The Poincare sphere method and the SOP method are suitable for the purpose of performing PMD detection using each channel signal of wavelength multiplexed light, because PMD is calculated based on the polarization analysis result at each wavelength.
[0010]
On the other hand, the FA method is a method for performing PMD analysis from wavelength characteristics using a wavelength variable light source. FIG. 7 is a diagram for explaining a PMD detection method based on the FA method. This shows an example of a conventional PMD compensation method in a wavelength division multiplexing (WDM) optical transmission system.
[0011]
In FIG. 7, the transmission side includes a wavelength variable light source 41 and a polarizer 42. The receiving side includes a polarizer 43 and an optical power meter 44. The polarizer 42 and the polarizer 43 are connected by an optical transmission path 45.
[0012]
On the transmission side, the wavelength tunable light source 41 generates signal light of various wavelengths at a predetermined sweep period and outputs the signal light to the polarizer 42. The polarizer 42 gives a known polarization state to the signal light transmitted from the wavelength variable light source 41 and sends it to the optical transmission line 45. On the receiving side, the signal light input from the optical transmission path 45 is input to the optical power meter 44 via the polarizer 43. In the optical power meter 44, the wavelength characteristic of the light intensity of the signal light input from the optical transmission path 45 is observed through the polarizer 43. The PMD amount is approximately calculated by analyzing the observed wavelength characteristics. As described above, the FA method shown in FIG. 7 can detect the PMD amount in the optical transmission line.
[0013]
[Problems to be solved by the invention]
However, in the conventional FA method, the PMD amount is calculated by measuring the wavelength characteristic of the delay amount of the light to be measured with a variable light source. Therefore, in the actual operation state where other signal light exists, the time of the PMD amount It is difficult to detect fluctuations.
[0014]
The present invention has been made in view of the above. A PMD detector capable of detecting temporal fluctuations in the amount of PMD in an optical transmission line and capable of being miniaturized, and a wavelength capable of performing PMD compensation using the PMD detector. An object is to obtain a multiplexed optical transmission system.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a PMD detector according to the present invention includes a part of an optical transmission line through which wavelength-multiplexed data signal light including data signal light of any two wavelengths whose polarization relationship is known is transmitted. Measurement light acquisition means for extracting wavelength multiplexed data signal light, first wavelength selection means for extracting each of the two wavelength data signal lights from output light of the measurement light acquisition means, and output light of the first wavelength selection means A first light intensity detecting means for detecting the signal light intensity of each of the two wavelength data signal lights, a polarizer for allowing a predetermined polarization component of the output light of the measurement light obtaining means to pass through, and the polarizer A second wavelength selection means for extracting each of the two-wavelength data signal light from the output light, and receiving the output light of the second wavelength selection means to detect the signal light intensity of each of the two-wavelength data signal light 2nd light intensity Characterized by comprising a detecting means.
[0016]
According to this invention, a part of the wavelength multiplexed data signal is transmitted from the optical transmission line through which the wavelength multiplexed data signal light including the data signal light of any two wavelengths whose polarization relationship is known is transmitted by the measurement light acquisition means. Light is extracted. When the first wavelength selection means extracts each of the two wavelength data signal lights from the output light of the measurement light acquisition means, the first light intensity detection means extracts the extracted two wavelength data signals. The signal light intensity of each light is detected. On the other hand, when a predetermined polarization component is extracted from the output light of the measurement light acquisition means by the polarizer, each of the two wavelength data signal lights is output from the output light of the polarizer by the second wavelength selection means. The second light intensity detecting means extracts the signal light intensity of each of the two wavelength data signal lights in a predetermined polarization state.
[0017]
The PMD detector according to the next invention is characterized in that, in the above invention, the first wavelength selection means and the second wavelength selection means are variable wavelength selection means.
[0018]
According to this invention, the variable wavelength selection means is used for the first wavelength selection means and the second wavelength selection means.
[0019]
The PMD detector according to the next invention extracts a part of the wavelength multiplexed data signal light from the optical transmission line through which the wavelength multiplexed data signal light including the data signal light of any two wavelengths whose polarization relationship is known is transmitted. Measurement light acquisition means, a polarizer that passes a predetermined polarization component of the output light of the measurement light acquisition means, and the wavelength multiplexed data signal light including the data signal light of the two wavelengths from the output light of the polarizer, respectively And a light intensity detecting means for detecting the signal light intensity.
[0020]
According to this invention, a part of the wavelength multiplexed data signal is transmitted from the optical transmission line through which the wavelength multiplexed data signal light including the data signal light of any two wavelengths whose polarization relationship is known is transmitted by the measurement light acquisition means. When the light is extracted, the polarizer extracts a predetermined polarization component from the output light of the measurement light acquisition means, and the light intensity detection means includes the data signal light of the two wavelengths from the output light of the polarizer. The signal light intensity of each wavelength multiplexed data signal light is detected.
[0021]
The PMD detector according to the next invention is characterized in that a polarization beam splitter is used instead of the polarizer.
[0022]
According to the present invention, a polarization beam splitter is used instead of the polarizer. In the polarization beam splitter, the input wavelength multiplexed data signal light is separated into orthogonal polarization components, and the light intensity is detected.
[0023]
The wavelength division multiplexing optical transmission system according to the next invention is a wavelength division multiplexing optical transmission system for transmitting wavelength division multiplexed data signal light including data signal light of any two wavelengths whose polarization relation is known. A PMD detector according to any one of claims 1 to 4, wherein a part of the wavelength multiplexed data signal light is extracted from an optical transmission line through which light is transmitted, and the signal light intensity of at least the two wavelength data signal lights is detected. First PMD compensation means arranged to perform PMD compensation operation on the output light of the measurement light acquisition means in the PMD detector, and PMD compensation operation on the wavelength multiplexed data signal light transmitted through the optical transmission line The second PMD compensation means arranged to perform the above-mentioned, and the PMD analyzed from the signal light intensity detected by the PMD detector is minimized. Controls 1PMD compensation means, characterized in that a condition of the first 1PMD compensation means for the PMD to minimize and control means providing said first 2PMD compensation means.
[0024]
According to this invention, the first PMD compensation means is arranged to perform PMD compensation operation on the output light of the measurement light acquisition means in the PMD detector, and the second PMD compensation means is for the wavelength multiplexed data signal light on the optical transmission line. Arranged to perform PMD compensation operations. The control means controls the first PMD compensation means so that the PMD analyzed from the signal light intensity detected by the PMD detector is minimized, and the condition of the first PMD compensation means for minimizing PMD is the second PMD compensation means. Given to.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of a PMD detector and a wavelength division multiplexing optical transmission system according to the present invention will be explained below in detail with reference to the accompanying drawings.
[0026]
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a PMD detector according to the first embodiment of the present invention. In FIG. 1, wavelength multiplexed data signal light (λ1... Λm... Λn... Λz) including two wavelengths (λn, λm) whose polarization relationship is known is transmitted to the optical transmission line 10.
[0027]
The PMD detector shown in FIG. 1 includes an optical tap 11 that extracts a part of wavelength multiplexed data signal light from an optical transmission line 10, an optical demultiplexer 12 that bifurcates the output light of the optical tap 11, and an optical demultiplexer. An optical demultiplexer 13 that further branches one branched light of 12 into two, and optical filters 14 and 15 that receive each branched light from the optical demultiplexer 13 and extract data signal light of specific wavelengths (λm, λn); Wavelength multiplexed data signal light having a specific polarization from photodiodes (hereinafter referred to as “PD”) 16 and 17 that electrically convert the output light of the optical filters 14 and 15 and the other branched light of the optical demultiplexer 12 A polarizer 18 to be extracted, an optical demultiplexer 19 that bifurcates the output light of the polarizer 18, and an optical filter that receives each branched light from the optical demultiplexer 19 and extracts signal light of specific wavelengths (λm, λn). 20, 21 and the output light of the optical filters 20, 21 are electrically converted. And a PD22,23.
[0028]
Next, the operation of the PMD detector configured as described above will be described. Wavelength multiplexed data signal light (λ1... Λm... Λn... Λz) including two wavelength (λn, λm) data signal light whose polarization relationship is known is transmitted to the optical transmission line 10. Wavelength multiplexed data signal light (λ1... Λm... Λn... Λz) taken out from the optical transmission line 10 by the optical tap 11 is branched into two by the optical demultiplexer 12 and input to the optical demultiplexer 13 and the polarizer 18. .
[0029]
In the optical filter 14 that receives one branched light of the optical demultiplexer 13, the data signal light having the wavelength λm is extracted from the branched light. As a result, the PD 16 outputs an intensity detection signal of the data signal light having the wavelength λm. Similarly, in the optical filter 15 that receives the other branched light of the optical demultiplexer 13, the data signal light having the wavelength λn is extracted from the branched light. As a result, the intensity detection signal of the data signal light having the wavelength λn is output from the PD 17.
[0030]
In the polarizer 18, wavelength division multiplexed data signal light having a specific polarization is extracted from the branched light input from the optical demultiplexer 12 and is output to the optical demultiplexer 19. In the optical filter 20 that receives one branched light of the optical demultiplexer 19, the data signal light having the wavelength λm is extracted from the branched light. As a result, an intensity detection signal of the data signal light having the wavelength λm is output from the PD 22. Similarly, in the optical filter 21 that receives the other branched light of the optical demultiplexer 19, the data signal light having the wavelength λn is extracted from the branched light. As a result, the PD 23 outputs an intensity detection signal of the data signal light having the wavelength λn.
[0031]
Next, in a detection processing unit (not shown) that receives the outputs of the PDs 16, 17, 22, and 23, the signal light intensities of the wavelengths λm and λn detected by the PDs 16 and 17 when the polarizer 18 is not interposed, and the polarizer 18 are interposed. The polarization relationship at the time of output is calculated with respect to the polarization relationship at the time of input of the optical transmission line 10 from the relationship with the signal light intensity of the wavelengths λm and λn detected by the PDs 22 and 23. The time variation of the PMD amount at is analyzed.
[0032]
Therefore, according to the first embodiment, the PMD can be detected by specifying the wavelength. Therefore, in the WDM optical transmission system, the time variation of the PMD amount can be followed and detected. Further, since it is possible to detect the PMD amount over the entire wavelength band by measuring the polarization relationship of a plurality of wavelengths, it is possible to reduce the size of the PMD detector.
[0033]
Embodiment 2. FIG.
FIG. 2 is a block diagram showing a configuration of a PMD detector according to the second embodiment of the present invention. In the second embodiment, as shown in FIG. 2, in the configuration shown in FIG. 1, variable optical filters 24-27 capable of changing the center wavelength are provided instead of the optical filters 14, 15, 20, and 21. Yes. The rest is the same as the configuration shown in FIG. Here, the description will be focused on the portion related to the second embodiment.
[0034]
By making the optical filter variable, it is possible to detect the light intensity with and without a polarizer for data signal light of two or more wavelengths, so that more accurate PMD detection can be performed. It becomes possible.
[0035]
Therefore, according to the second embodiment, the PMD can be detected by specifying the wavelength, so that the time variation of the PMD amount can be detected following the WDM optical transmission system. Further, since it is possible to detect the PMD amount over the entire wavelength band by measuring the polarization relationship of a plurality of wavelengths, it is possible to reduce the size of the PMD detector. Furthermore, the PMD amount can be analyzed from two or more signal lights, and the PMD amount can be detected with higher accuracy.
[0036]
Embodiment 3 FIG.
FIG. 3 is a block diagram showing the configuration of the PMD detector according to the first embodiment of the present invention. In FIG. 3, wavelength multiplexed data signal light (λ1... Λm... Λn... Λz) including two wavelengths (λn, λm) whose polarization relationship is known is transmitted to the optical transmission line 10.
[0037]
The PMD detector shown in FIG. 3 includes an optical tap 11 that extracts a part of wavelength multiplexed data signal light (λ1... Λm... Λn... Zz) from the optical transmission line 10, and a polarizer 18 that receives output light from the optical tap 11. And an optical spectrum analyzer 28 that receives the output light of the polarizer 18 and simultaneously detects the light intensity of each data signal of the wavelength multiplexed data signal light (λ1... Λm... Λn... Λz).
[0038]
Next, the operation of the PMD detector configured as described above will be described. Wavelength multiplexed data signal light (λ1... Λm... Λn... Λz) including two wavelength (λn, λm) data signal light whose polarization relationship is known is transmitted to the optical transmission line 10.
[0039]
Wavelength multiplexed data signal light (λ1... Λm... Λn... Λz) taken out from the optical transmission line 10 by the optical tap 11 is input to the optical spectrum analyzer 28 via the polarizer 18. The optical spectrum analyzer 28 simultaneously detects the light intensities of the wavelength multiplexed data signal light (λ1... Λm... Λn... Λz).
[0040]
Then, in a detection processing unit (not shown) that receives the output of the optical spectrum analyzer 28, the polarization relationship when the optical transmission line 10 is input is determined based on the relationship between the signal light intensities after the polarizer detected by the optical spectrum analyzer 28. Thus, the polarization relationship at the time of output is calculated, and the temporal variation of the PMD amount in the optical transmission line 10 is analyzed.
[0041]
Therefore, according to the third embodiment, the PMD can be detected by specifying the wavelength, so that the time variation of the PMD amount can be detected following the WDM optical transmission system. Further, since it is possible to detect the PMD amount over the entire wavelength band by measuring the polarization relationship of a plurality of wavelengths, it is possible to reduce the size of the PMD detector. Furthermore, since it is possible to analyze the PMD amount over the entire wavelength band, it becomes possible to detect the PMD amount with higher accuracy.
[0042]
Embodiment 4 FIG.
FIG. 4 is a block diagram showing a configuration of a PMD detector according to the fourth embodiment of the present invention. In the fourth embodiment, as shown in FIG. 4, in the configuration shown in FIG. 1, a polarization beam splitter 29 is provided in place of the polarizer 18 and the optical demultiplexer 19. The rest is the same as the configuration shown in FIG. Here, the description will be focused on the portion related to the fourth embodiment.
[0043]
In FIG. 4, a polarization beam splitter 29 separates the wavelength multiplexed light input from the optical demultiplexer 12 into polarization components that are orthogonal to each other. Therefore, the optical filters 20 and 21 and the PDs 22 and 23 can detect the light intensity as in the first embodiment, and can obtain the same effects as those in the first embodiment.
[0044]
Therefore, according to the fourth embodiment, the PMD can be detected by specifying the wavelength. Therefore, in the WDM optical transmission system, the time variation of the PMD amount can be detected following the FA method. Further, since it is possible to detect the PMD amount over the entire wavelength band by sweeping the variable length light source using the FA method, the PMD detector can be downsized. The polarizer 18 in the third embodiment (FIG. 3) can be similarly replaced with a polarization beam splitter.
[0045]
Embodiment 5 FIG.
FIG. 5 is a block diagram showing a configuration of a wavelength division multiplexing optical transmission system having a PMD compensation function according to Embodiment 5 of the present invention. As shown in FIG. 5, in this wavelength division multiplexing optical transmission system, a PMD compensating optical circuit 34 is provided between the output end of the optical tap 11 and the input end of the optical demultiplexer 12 in the configuration shown in FIG. In addition, a PMD compensation optical circuit 35 is provided on the optical transmission line 10, and a control circuit 36 for electrically controlling the PMD compensation optical circuits 34 and 35 is provided. Intensity signals detected from the PDs 16, 17, 22, and 23 are input to the control circuit 36.
[0046]
Next, a PMD compensation operation in the wavelength division multiplexing optical transmission system having the PMD compensation function configured as described above will be described. Wavelength multiplexed data signal light (λ1... Λm... Λn... Λz) including two wavelength (λn, λm) data signal light whose polarization relationship is known is transmitted to the optical transmission line 10.
[0047]
Wavelength multiplexed data signal light (λ1... Λm... Λn... Λz) taken out from the optical transmission line 10 by the optical tap 11 is guided to the optical demultiplexer 12 through the PMD compensation optical circuit 34. The control circuit 36 analyzes the PMD amount of the data signal light having the wavelengths λm and λn based on the intensity signals from the PDs 16, 17, 22, and 23, and the PMD compensation optical circuit 34 so that the PMD amount is minimized. To control.
[0048]
Next, the control circuit 36 applies the condition of the PMD compensation optical circuit 34 that minimizes the PMD amount obtained as a result of the control to the PMD compensation optical circuit 35. As a result, PMD in the optical transmission line 10 can be compensated.
[0049]
As described above, according to the fifth embodiment, the PMD in the optical transmission line 10 can be compensated by combining the PMD detector, the PMD compensation optical circuit, and the control circuit. Therefore, in the WDM optical transmission system, it is possible to follow and detect and compensate for the time variation of the PMD amount.
[0050]
In the fifth embodiment, the configuration of the PMD detector in the first embodiment is used, but it goes without saying that the configuration of the PMD detector in the second to fourth embodiments can be used similarly.
[0051]
【The invention's effect】
As described above, according to the present invention, the measurement light acquisition means starts from the optical transmission line through which the wavelength multiplexed data signal light including the data signal light of any two wavelengths whose polarization relationship is known is transmitted. The wavelength division multiplexed data signal light is extracted. When the first wavelength selection means extracts each of the two wavelength data signal lights from the output light of the measurement light acquisition means, the first light intensity detection means extracts the extracted two wavelength data signals. The signal light intensity of each light is detected. On the other hand, when a predetermined polarization component is extracted from the output light of the measurement light acquisition means by the polarizer, each of the two wavelength data signal lights is output from the output light of the polarizer by the second wavelength selection means. The second light intensity detecting means extracts the signal light intensity of each of the two wavelength data signal lights in a predetermined polarization state. Therefore, it is possible to analyze and detect the PMD amount temporal variation in the optical transmission line based on the signal light intensity obtained in the state where the polarizer is not interposed and in the state where the polarizer is interposed. This can be applied over the entire wavelength range, and it becomes possible to detect the PMD amount following the time variation. As a result, the PMD detector can be downsized.
[0052]
According to the next invention, in the above invention, a wavelength variable selecting means is used for the first wavelength selecting means and the second wavelength selecting means. Therefore, since the signal light intensity with and without the polarizer can be obtained from the signal light having two or more wavelengths, PMD can be detected with higher accuracy.
[0053]
According to the next invention, in the measurement light acquisition means, a part of the wavelength multiplexed data is transmitted from the optical transmission line through which the wavelength multiplexed data signal light including the data signal light of any two wavelengths whose polarization relationship is known is transmitted. When the signal light is extracted, the polarizer extracts a predetermined polarization component from the output light of the measurement light acquisition means, and the light intensity detection means includes the data signal light of the two wavelengths from the output light of the polarizer. The signal light intensity of each of the wavelength multiplexed data signal light is detected. As a result, it is possible to obtain the signal light intensity when the polarizer is present in the entire wavelength range, so that PMD detection can be performed with higher accuracy.
[0054]
According to the next invention, a polarization beam splitter can be used instead of the polarizer. In the polarization beam splitter, the input wavelength multiplexed data signal light is separated into orthogonal polarization components, and the light intensity is detected. Therefore, the same effect as the above invention can be obtained.
[0055]
According to the next invention, the first PMD compensation means is arranged to perform a PMD compensation operation on the output light of the measurement light acquisition means in the PMD detector, and the second PMD compensation means is the wavelength multiplexed data signal light on the optical transmission line. Are arranged to perform a PMD compensation operation. The control means controls the first PMD compensation means so that the PMD analyzed from the signal light intensity detected by the PMD detector is minimized, and the condition of the first PMD compensation means for minimizing PMD is the second PMD compensation means. Given to. Therefore, a wavelength division multiplexing optical transmission system capable of detecting and compensating for PMD can be constructed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a PMD detector according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a PMD detector according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of a PMD detector according to a third embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a PMD detector according to a fourth embodiment of the present invention.
FIG. 5 is a configuration diagram of a wavelength division multiplexing optical system having a PMD compensation function according to a fifth embodiment of the present invention.
FIG. 6 is a diagram showing the relationship between the bit rate of an optical signal and PMD that causes a 1 dB power penalty.
FIG. 7 is a diagram for explaining a PMD detection method by a conventional FA method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Optical transmission line, 11 Optical tap, 12, 13, 19 Optical demultiplexer, 14, 15, 20, 21 Optical filter, 16, 17, 22, 23 Photodiode (PD), 18 Polarizer, 24, 25, 26, 27 Variable optical filter, 28 Optical spectrum analyzer, 29 Polarization beam splitter, 34, 35 PMD compensation optical circuit, 36 Control circuit.

Claims (4)

And any two wavelengths of the data signal light polarization relationship is known, the wavelength from the optical transmission path polarization relationships wavelength multiplexed optical data signal comprising one wavelength or more data signal light is unknown is transmitted Measuring light acquisition means for extracting a part of the output of the multiplexed data signal light;
First wavelength selection means for extracting data signals of two wavelengths whose polarization relationship is known from the output light of the measurement light acquisition means;
First light intensity detection means for receiving the output light of the first wavelength selection means and detecting the signal light intensity of the two-wavelength data signal light whose polarization relationship is known ;
A polarizer that passes a predetermined polarization component of the output light of the measurement light acquisition means;
Second wavelength selection means for extracting data signal light of two wavelengths whose polarization relationship is known from the output light of the polarizer ;
Second light intensity detecting means for receiving the output light of the second wavelength selecting means and detecting the signal light intensity of the data signal light of two wavelengths whose polarization relation is known ;
Equipped with a,
A PMD detector for detecting a PMD amount in each wavelength band of the wavelength multiplexed data signal light based on detection results of the first light intensity detection means and the second light intensity detection means .   The PMD detector according to claim 1, wherein the first wavelength selection unit and the second wavelength selection unit are variable wavelength selection units. Instead of the polarizer, PMD detector according to claim 1 or 2, characterized in that the polarization beam splitter is used. In a wavelength division multiplexing optical transmission system that transmits wavelength-multiplexed data signal light including data signal light of any two wavelengths whose polarization relationship is known and data signal light of one wavelength or more whose polarization relationship is unknown ,
Removed portion from the optical transmission line in which the wavelength-multiplexed data signal light is transmitted in the output of the wavelength-multiplexed data signal light, according to claim 1 to 3 for detecting a PMD amount in each wavelength band of the wavelength-multiplexed optical data signal A PMD detector according to any one of the above;
First PMD compensation means arranged to perform a PMD compensation operation on the output light of the measurement light acquisition means in the PMD detector;
Second PMD compensation means arranged to perform a PMD compensation operation on the wavelength multiplexed data signal light transmitted through the optical transmission line;
The first PMD compensation means is controlled so that the PMD analyzed from the signal light intensity detected by the PMD detector is minimized, and the condition of the first PMD compensation means for minimizing PMD is defined in the second PMD compensation means. Giving control means,
A wavelength division multiplexing optical transmission system.

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