JP2013068670A - Polarization mode dispersion generator - Google Patents

Abstract

The present invention generates polarization mode dispersion having an arbitrary wavelength profile.
The present invention provides an input optical signal with a delay difference between orthogonally polarized waves of the input optical signal so as to depend on the wavelength of the input optical signal (delay difference T ₁ (λ)). ) The first delay difference providing device 1A, the polarization plane rotating device 2 that rotates the polarization plane of the output optical signal from the first delay difference providing device 1A (rotation angle Ψ), and the output light from the polarization plane rotating device 2 The delay difference between the orthogonal polarizations of the signal is given to the output optical signal from the polarization plane rotation device 2 so as to depend on the wavelength of the output optical signal from the polarization plane rotation device 2 (delay difference T ₂ (λ)) a second delay difference providing device 1B.
[Selection] Figure 3

Description

  The present invention relates to a polarization mode dispersion generator that simulates polarization mode dispersion characteristics.

  As the demand for data communication increases, optical transmission networks using optical signal modulation technology and optical signal multiplexing technology that enable transmission of large-capacity traffic are becoming widespread. On the other hand, with an increase in data transmission speed, there is a concern about the influence of polarization mode dispersion of an optical fiber transmission line on optical signal waveform deterioration. In analyzing this effect, it is difficult to control a naturally occurring polarization mode dispersion, and a technique for artificially generating polarization mode dispersion is important.

  FIG. 1 shows a configuration of a polarization mode dispersion generator of the prior art (see, for example, Non-Patent Document 1). The polarization mode dispersion generator includes a first delay difference applying device 1A, a polarization plane rotating device 2, and a second delay difference applying device 1B. The first delay difference providing device 1A includes a first delay difference providing unit 11A 'and a first polarization separation unit 12A. The second delay difference providing device 1B includes a second delay difference providing unit 11B 'and a second polarization separation unit 12B.

The first delay difference applying device 1A (for example, polarization maintaining fiber) adds a delay difference between orthogonal polarizations of the input optical signal to the input optical signal (delay difference T ₁ ). In the first delay difference providing device 1A, the first polarization separation unit 12A separates the input optical signal into optical signals having orthogonal polarizations, and the first delay difference provision unit 11A ′ performs the first polarization separation. A delay difference is provided between the output optical signals of the unit 12A corresponding to the polarizations of the output optical signals of the first polarization separation unit 12A.

  The polarization plane rotating device 2 (for example, a variable Faraday rotator) rotates the polarization plane of the output optical signal from the first delay difference providing device 1A (rotation angle Ψ).

The second delay difference providing device 1B (for example, the polarization maintaining fiber) uses the difference in delay between orthogonal polarizations of the output optical signal from the polarization plane rotating device 2 as the output optical signal from the polarization plane rotating device 2. (Delay difference T ₂ ). In the second delay difference providing device 1B, the second polarization separation unit 12B separates the output optical signal from the polarization plane rotating device 2 into optical signals having orthogonal polarizations, and the second delay difference providing unit 11B ′. Gives a delay difference between the output optical signals of the second polarization separation unit 12B corresponding to the polarizations of the output optical signals of the second polarization separation unit 12B.

Hiroshi Amimura, Kazuhiro Ikeda, Tatsuya Hatano, Takeshi Takagi, Sugiyo Wako, Hiroshi Matsuura, “PMD Compensator and PMD Emulator”, Furukawa Electric Times, No. 112 (July 2003), pp. 21-25. Hideki Kanno, “Current Status and Prospects of Dispersion Compensation Devices”, Laser Research, Volume 30 No. 10 (October 2002), pp. 593-597.

  The wavelength dependency of the conventional DGD and PCD is shown in FIG. DGD is the size of the PMD vector, and PCD is a component in the same direction as the PMD vector in the rate of change of the PMD vector with respect to the wavelength λ. DGD is independent of wavelength, and PCD is zero. Therefore, polarization mode dispersion having an arbitrary wavelength profile cannot be generated. However, the polarization mode dispersion of an optical fiber transmission line generally exhibits complicated wavelength dependence.

  Accordingly, in order to solve the above-described problems, an object of the present invention is to provide a polarization mode dispersion generating apparatus that generates polarization mode dispersion having an arbitrary wavelength profile.

  In order to achieve the above object, a delay difference between orthogonal polarizations of an optical signal is given to the optical signal so as to depend on the wavelength of the optical signal.

  Specifically, the present invention provides a first delay difference that is added to the input optical signal such that a delay difference between orthogonal polarizations of the input optical signal depends on the wavelength of the input optical signal. A delay difference between a device, a polarization plane rotation device that rotates a polarization plane of an output optical signal from the first delay difference applying device, and an orthogonal polarization of an output optical signal from the polarization plane rotation device And a second delay difference providing device that imparts to the output optical signal from the polarization plane rotating device so as to depend on the wavelength of the output optical signal from the polarization plane rotating device. It is a mode dispersion generator.

  According to this configuration, it is possible to provide a polarization mode dispersion generating apparatus that generates polarization mode dispersion having an arbitrary wavelength profile.

の３式が成立するように、前記第１遅延差付与装置が遅延差Ｔ_１（λ）を付与し、前記偏波面回転装置が回転角Ψを付与し、前記第２遅延差付与装置が遅延差Ｔ_２（λ）を付与することを特徴とする偏波モード分散発生装置である。 Further, the present invention provides a wavelength λ of an optical signal, a delay difference T ₁ (λ) provided by the first delay difference applying device, a rotation angle Ψ provided by the polarization plane rotating device, and the second delay difference applying device. The desired difference in the same direction as the PMD vector among the delay difference T ₂ (λ), the desired size of the PMD (Polarization Mode Dispersion) vector DGD (Differential Group Delay), and the rate of change of the PMD vector with respect to the wavelength λ About a desired component Depol (Depolarization) in the direction perpendicular to the PMD vector among the rate of change with respect to the wavelength λ of the PMD (Polarization-dependent Chromatic Dispersion) and the PMD vector,

The first delay difference giving device gives the delay difference T ₁ (λ), the polarization plane rotating device gives the rotation angle Ψ, and the second delay difference giving device delays so that It is a polarization mode dispersion generating apparatus characterized by giving a difference T ₂ (λ).

According to this configuration, polarization mode dispersion having a desired wavelength profile can be generated by controlling the delay difference T ₁ (λ), the rotation angle Ψ, and the delay difference T ₂ (λ).

  In the present invention, the first delay difference providing device separates the input optical signal into optical signals having orthogonal polarizations and separates the input optical signals into optical signals having different wavelengths. And a delay difference corresponding to the polarization and wavelength of each output optical signal of the first polarization wavelength separation unit between the output optical signals of the first polarization wavelength separation unit. A delay difference providing unit, wherein the second delay difference providing device separates the output optical signal from the polarization plane rotating device into optical signals having orthogonal polarizations, and converts the output optical signals into optical signals having different wavelengths. Corresponding to the polarization and wavelength of each output optical signal of the second polarization wavelength separation unit between the second polarization wavelength separation unit to be separated and the output optical signals of the second polarization wavelength separation unit And a second delay difference providing unit for providing a delay difference. A polarization mode dispersion generator for.

  According to this configuration, it is possible to provide a polarization mode dispersion generating apparatus that generates polarization mode dispersion having an arbitrary wavelength profile.

  The present invention is characterized in that at least one of the wavelength separation portion of the first polarization wavelength separation portion and the wavelength separation portion of the second polarization wavelength separation portion is a diffraction grating. It is a polarization mode dispersion generator.

  According to this configuration, wavelength separation can be performed using a diffraction grating.

  According to the present invention, at least one of the wavelength separation portion of the first polarization wavelength separation portion and the wavelength separation portion of the second polarization wavelength separation portion is a VIPA (Virtual Imaging Phased Array) glass plate. This is a polarization mode dispersion generating device.

  According to this configuration, wavelength separation can be performed using a VIPA glass plate.

  Further, the present invention is the polarization mode dispersion generating device, wherein at least one of the first delay difference providing unit and the second delay difference providing unit is LCoS (Liquid Crystal on Silicon).

  According to this configuration, it is possible to add a delay difference using LCoS.

  Further, the present invention is the polarization mode dispersion generating device, wherein at least one of the first delay difference providing unit and the second delay difference providing unit is a three-dimensional mirror.

  According to this configuration, the delay difference can be given using the three-dimensional mirror.

  In addition, the present invention provides a combination of a wavelength separation part and the first delay difference providing part in the first polarization wavelength separation part, and a wavelength separation part and the second part in the second polarization wavelength separation part. Of the combinations of the delay difference providing units, at least one of the combinations is a FBG (Fiber Bragg Grating).

  According to this configuration, wavelength separation and delay difference provision can be performed using FBG.

  The present invention can provide a polarization mode dispersion generating apparatus that generates polarization mode dispersion having an arbitrary wavelength profile.

It is a figure which shows the structure of the polarization mode dispersion | distribution generator of a prior art. It is a figure which shows the wavelength dependence of DGD and PCD of a prior art. It is a figure which shows the structure of the polarization mode dispersion generator of this invention. It is a figure which shows the wavelength dependence of DGD and PCD of this invention. It is a figure which shows the outline of delay difference provision of this invention. It is a figure which shows the outline of delay difference provision of this invention. 1 is a diagram illustrating a configuration of a polarization mode dispersion generating apparatus according to Embodiment 1. FIG. It is a figure which shows the structure of the polarization mode dispersion generation apparatus of Embodiment 2. FIG. It is a figure which shows the structure of the polarization mode dispersion generator of Embodiment 3. It is a figure which shows the structure of the polarization mode dispersion generator of Embodiment 4. It is a figure which shows the structure of the polarization mode dispersion generator of Embodiment 5. It is a figure which shows the structure of the polarization mode dispersion generator of Embodiment 6.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Outline of the present invention)
The configuration of the polarization mode dispersion generator of the present invention is shown in FIG. The polarization mode dispersion generator includes a first delay difference applying device 1A, a polarization plane rotating device 2, and a second delay difference applying device 1B. The first delay difference providing device 1A includes a first wavelength separation delay difference providing unit 11A and a first polarization separation unit 12A. The second delay difference providing device 1B includes a second wavelength separation delay difference providing unit 11B and a second polarization separation unit 12B.

The first delay difference applying device 1A adds a delay difference between orthogonal polarizations of the input optical signal to the input optical signal so as to depend on the wavelength of the input optical signal (delay difference T ₁ (λ )). In the first delay difference providing device 1A, the first polarization separation unit 12A separates the input optical signal into optical signals having orthogonal polarization, and the first wavelength separation delay difference providing unit 11A Each output optical signal of the separation unit 12A is separated into optical signals having different wavelengths, and is delayed between the optical signals after wavelength separation in accordance with the polarization and wavelength of each optical signal after wavelength separation. Give the difference.

  The polarization plane rotating device 2 (for example, a variable Faraday rotator) rotates the polarization plane of the output optical signal from the first delay difference providing device 1A (rotation angle Ψ).

The second delay difference providing device 1B depends on the wavelength of the output optical signal from the polarization plane rotating device 2 for the delay difference between the orthogonal polarizations of the output optical signal from the polarization plane rotating device 2. To the output optical signal from the polarization plane rotating device 2 (delay difference T ₂ (λ)). In the second delay difference providing device 1B, the second polarization separation unit 12B separates the output optical signal from the polarization plane rotating device 2 into optical signals having orthogonal polarizations, and the second wavelength separation delay difference providing unit. 11B separates the output optical signals of the second polarization separation unit 12B into optical signals having different wavelengths, and polarizations of the optical signals after wavelength separation between the optical signals after wavelength separation. And a delay difference corresponding to the wavelength.

  The wavelength dependence of DGD and PCD of the present invention is shown in FIG. DGD is the size of the PMD vector, and PCD is a component in the same direction as the PMD vector in the rate of change of the PMD vector with respect to the wavelength λ. DGD depends on wavelength, and PCD also depends on wavelength. Therefore, polarization mode dispersion having an arbitrary wavelength profile can be generated.

Next, control parameters will be described. Let λ be the wavelength of the optical signal. The necessary control parameters are the delay difference T ₁ (λ) provided by the first delay difference applying device 1A, the rotation angle Ψ provided by the polarization plane rotating device 2, and the delay difference T provided by the second delay difference applying device 1B. ₂ (λ). The desired PMD parameters are the PMD vector magnitude DGD, the component PCD in the same direction as the PMD vector of the change rate of the PMD vector with respect to the wavelength λ, and the direction perpendicular to the PMD vector of the change rate of the PMD vector with respect to the wavelength λ. Component Depol.

Ｔ_１（λ）＝Ｔ_２（λ）＝Ｔ（λ）が成立するとき、数３及び数４が成立する。

よって、遅延差Ｔ_１（λ）、回転角Ψ及び遅延差Ｔ_２（λ）を制御して、所望の波長プロファイルを有する偏波モード分散を発生させることができる。 Necessary control parameters (T ₁ (λ), ψ, T ₂ (λ)) and desired PMD parameters (DGD, PCD, Depol) satisfy the relationship of Equation 2.

When T ₁ (λ) = T ₂ (λ) = T (λ) holds, Equations 3 and 4 hold.

Therefore, polarization mode dispersion having a desired wavelength profile can be generated by controlling the delay difference T ₁ (λ), the rotation angle Ψ, and the delay difference T ₂ (λ).

  Next, an outline of delay difference provision will be described. The outline of delay difference application of the present invention is shown in FIGS. Here, LCoS is a device in which liquid crystals are arranged in a cell shape on a silicon substrate, and is a device that changes the refractive index of liquid crystals depending on the position by applying a voltage to each cell. The three-dimensional mirror is a mirror that changes the curvature of the curved surface according to the position.

  FIG. 5 shows that optical signals having different wavelengths are given different phase and delay differences when reflected at different positions of the LCoS or 3D mirror. The wavelength profile of the phase difference, the delay difference, and the chromatic dispersion is, for example, as shown in the lower diagram of FIG. FIG. 6 shows that optical signals having different polarizations and wavelengths are given different phase differences and delay differences when reflected at different positions on the LCoS or three-dimensional mirror. For example, the wavelength profile of the phase difference and the delay difference is as shown in the upper diagram and middle diagram of FIG. 6, and the wavelength profile of the DGD is as shown in the lower diagram of FIG. Here, since the maximum value of the delay difference to be applied to the TE mode is Te and the minimum value of the delay difference to be applied to the TM mode is Tm, the maximum value of DGD is Te−Tm.

(Embodiment 1)
The configuration of the polarization mode dispersion generating apparatus of the first embodiment is shown in FIG. In the first embodiment, T ₁ (λ) = T ₂ (λ), and the first delay difference providing device 1A and the second delay difference providing device 1B are realized by the same device. Of the wavelength separation delay difference providing unit, a diffraction grating is used as the wavelength separation means, and LCoS is used as the delay difference providing means.

  The optical signal enters the spatial optical system through the input terminal and the optical circulator 3, becomes a parallel light beam in the lens 4, and is separated into a TE mode and a TM mode in the polarization separation unit 12.

The TE mode passes through the four mirrors 111, but the TM mode does not pass through the four mirrors 111. Therefore, _a delay difference Ta independent of wavelength is given between the TE mode and the TM mode. Here, by adjusting the distance between the four mirrors 111, it is possible to adjust the delay difference T _a between the TE and TM modes.

The TE mode and the TM mode are reflected by the diffraction grating 112 and separated into optical signals having different wavelengths. Here, the direction of wavelength separation is a direction perpendicular to the paper surface. Optical signals having different polarizations and wavelengths are reflected at different positions of the LCoS 113. Therefore, a delay difference T _b (λ) depending on the wavelength is given between the different polarizations.

  The TE mode and the TM mode are reflected again by the diffraction grating 112, combine optical signals having different wavelengths, and combine themselves in the polarization separation unit 12.

  The optical signal is given a rotation angle Ψ / 2 of the polarization plane at the variable Faraday rotator 21, reflected by the mirror 22, and again given a rotation angle Ψ / 2 of the polarization plane at the variable Faraday rotator 21. Therefore, the rotation angle Ψ of the polarization plane is given to the optical signal.

The optical signal reaches the output terminal following the reverse direction. Therefore, the delay difference T ₁ (λ) = T ₂ (λ) = T (λ) = T _a + T _b (λ) and the rotation angle Ψ are added to the optical signal.

(Embodiment 2)
The configuration of the polarization mode dispersion generating apparatus of the second embodiment is shown in FIG. In the second embodiment, T ₁ (λ) ≠ T ₂ (λ), and the first delay difference providing device 1A and the second delay difference providing device 1B are realized by different devices. Of the wavelength separation delay difference providing unit, a diffraction grating is used as the wavelength separation means, and LCoS is used as the delay difference providing means.

  The optical signal enters the spatial optical system via the input terminal and the first optical circulator 3A, becomes a parallel light beam in the first lens 4A, and is separated into the TE mode and the TM mode in the first polarization separation unit 12A.

The TE mode passes through the four first mirrors 111A, but the TM mode does not pass through the four first mirrors 111A. Therefore, a delay difference T _1a / 2 independent of the wavelength is given between the TE mode and the TM mode. Here, the delay difference T _1a / 2 between the TE mode and the TM mode can be adjusted by adjusting the distance between the four first mirrors 111A.

The TE mode and the TM mode are transmitted through the first diffraction grating 112A and separated into optical signals having different wavelengths. Here, the direction of wavelength separation is a direction perpendicular to the paper surface. Optical signals having different polarizations and wavelengths are reflected at different positions of the first LCoS 113A. Therefore, a delay difference T _1b (λ) depending on the wavelength is given between the different polarizations.

  The optical signal follows the direction opposite to the above in the first wavelength separation delay difference providing unit 11A and the first polarization separation unit 12A, and is given the rotation angle Ψ of the polarization plane in the polarization plane rotating device 2, In the two-wavelength separation delay difference providing unit 11B and the second polarization separation unit 12B, the output terminal is reached by following the same and opposite directions as described above.

  Here, the second optical circulator 3B, the second lens 4B, the second polarization separation unit 12B, the four second mirrors 111B, the second diffraction grating 112B, and the second LCoS 113B are the first optical circulator 3A and the first lens, respectively. This corresponds to 4A, the first polarization separation unit 12A, the four first mirrors 111A, the first diffraction grating 112A, and the first LCoS 113A.

However, the delay difference due to the four second mirrors 111B is T _2a / 2, and the delay difference due to the second LCoS 113B is T _2b (λ). Therefore, delay difference T ₁ (λ) = T _1a / 2 + T _1b (λ) + T _1a / 2 = T _1a + T _1b (λ), delay difference T ₂ (λ) = T _2a / 2 + T _2b (λ) + T _2a / 2 = T _2a + T _2b (λ) and the rotation angle Ψ are given to the optical signal.

(Embodiment 3)
FIG. 9 shows the configuration of the polarization mode dispersion generating apparatus of the third embodiment. In the third embodiment, T ₁ (λ) = T ₂ (λ), and the first delay difference providing device 1A and the second delay difference providing device 1B are realized by the same device. Of the wavelength separation delay difference providing unit, a VIPA glass plate is used as the wavelength separation means, and a three-dimensional mirror is used as the delay difference providing means. Here, the VIPA glass plate is a material in which a reflection film is coated on both surfaces of a thin plate, and a high-angle dispersion element using a virtual point light source is realized by using the multiple reflection (for example, see Non-Patent Document 2).

  The optical signal enters the spatial optical system through the input terminal and the optical circulator 3, becomes a parallel light beam in the lens 4, and is separated into a TE mode and a TM mode in the polarization separation unit 12.

The TE mode passes through the four mirrors 111, but the TM mode does not pass through the four mirrors 111. Therefore, _a delay difference Ta independent of wavelength is given between the TE mode and the TM mode. Here, by adjusting the distance between the four mirrors 111, it is possible to adjust the delay difference T _a between the TE and TM modes.

The TE mode and the TM mode are reflected by the VIPA glass plate 114 and separated into optical signals having different wavelengths. Here, the direction of wavelength separation is a direction perpendicular to the paper surface. Optical signals having different polarizations and wavelengths are reflected at different positions on the three-dimensional mirror 115. Therefore, a delay difference T _b (λ) depending on the wavelength is given between the different polarizations.

  The TE mode and the TM mode are reflected again by the VIPA glass plate 114, combine optical signals having different wavelengths, and combine themselves in the polarization separation unit 12.

  The optical signal is given a rotation angle Ψ / 2 of the polarization plane at the variable Faraday rotator 21, reflected by the mirror 22, and again given a rotation angle Ψ / 2 of the polarization plane at the variable Faraday rotator 21. Therefore, the rotation angle Ψ of the polarization plane is given to the optical signal.

The optical signal reaches the output terminal following the reverse direction. Therefore, the delay difference T ₁ (λ) = T ₂ (λ) = T (λ) = T _a + T _b (λ) and the rotation angle Ψ are added to the optical signal.

(Embodiment 4)
The configuration of the polarization mode dispersion generating apparatus according to the fourth embodiment is shown in FIG. In the fourth embodiment, T ₁ (λ) ≠ T ₂ (λ), and the first delay difference providing device 1A and the second delay difference providing device 1B are realized by different devices. Of the wavelength separation delay difference providing unit, a VIPA glass plate is used as the wavelength separation means, and a three-dimensional mirror is used as the delay difference providing means.

  The optical signal enters the spatial optical system via the input terminal and the first optical circulator 3A, becomes a parallel light beam in the first lens 4A, and is separated into the TE mode and the TM mode in the first polarization separation unit 12A.

The TE mode passes through the four first mirrors 111A, but the TM mode does not pass through the four first mirrors 111A. Therefore, a delay difference T _1a / 2 independent of the wavelength is given between the TE mode and the TM mode. Here, the delay difference T _1a / 2 between the TE mode and the TM mode can be adjusted by adjusting the distance between the four first mirrors 111A.

The TE mode and the TM mode are transmitted through the first VIPA glass plate 114A and separated into optical signals having different wavelengths. Here, the direction of wavelength separation is a direction perpendicular to the paper surface. Optical signals having different polarizations and wavelengths are reflected at different positions of the first three-dimensional mirror 115A. Therefore, a delay difference T _1b (λ) depending on the wavelength is given between the different polarizations.

  The optical signal follows the direction opposite to the above in the first wavelength separation delay difference providing unit 11A and the first polarization separation unit 12A, and is given the rotation angle Ψ of the polarization plane in the polarization plane rotating device 2, In the two-wavelength separation delay difference providing unit 11B and the second polarization separation unit 12B, the output terminal is reached by following the same and opposite directions as described above.

  Here, the second optical circulator 3B, the second lens 4B, the second polarization separation unit 12B, the four second mirrors 111B, the second VIPA glass plate 114B, and the second three-dimensional mirror 115B are respectively the first optical circulator 3A. This corresponds to the first lens 4A, the first polarization separation unit 12A, the four first mirrors 111A, the first VIPA glass plate 114A, and the first three-dimensional mirror 115A.

However, the delay difference due to the four second mirrors 111B is T _2a / 2, and the delay difference due to the second three-dimensional mirror 115B is T _2b (λ). Therefore, delay difference T ₁ (λ) = T _1a / 2 + T _1b (λ) + T _1a / 2 = T _1a + T _1b (λ), delay difference T ₂ (λ) = T _2a / 2 + T _2b (λ) + T _2a / 2 = T _2a + T _2b (λ) and the rotation angle Ψ are given to the optical signal.

(Embodiment 5)
FIG. 11 shows the configuration of the polarization mode dispersion generating apparatus of the fifth embodiment. In the fifth embodiment, T ₁ (λ) = T ₂ (λ), and the first delay difference providing device 1A and the second delay difference providing device 1B are realized by the same device. An FBG is used as the wavelength separation delay difference providing unit. Here, since the FBG is not a variable device, the delay difference to be applied cannot be controlled to a variable value and is fixed to a constant value, but a spatial optical system need not be used. The polarization separation unit 12 may use an optical waveguide or may use a spatial optical system.

  The optical signal passes through the input terminal and the optical circulator 3 and is separated into the TE mode and the TM mode in the polarization separation unit 12.

The TE mode passes through the delay line 116, the FBG 117, and the optical circulator 118, but the TM mode does not pass through the delay line 116, the FBG 117, and the optical circulator 118. Therefore, _a delay difference Ta that does not depend on the wavelength and a delay difference T _b (λ) that depends on the wavelength are given between the TE mode and the TM mode. In the TE mode and the TM mode, the polarization separation unit 12 multiplexes itself and reaches the optical circulator 23, and the variable Faraday rotator 21 is given a rotation angle Ψ of the polarization plane.

The optical signal reaches the output terminal following the reverse direction. Therefore, the delay difference T ₁ (λ) = T ₂ (λ) = T (λ) = T _a + T _b (λ) and the rotation angle Ψ are added to the optical signal.

(Embodiment 6)
The configuration of the polarization mode dispersion generator of Embodiment 6 is shown in FIG. In the sixth embodiment, T ₁ (λ) ≠ T ₂ (λ), and the first delay difference providing device 1A and the second delay difference providing device 1B are realized by different devices. An FBG is used as the wavelength separation delay difference providing unit.

  The optical signal is separated into a TE mode and a TM mode in the first polarization separation unit 12A via the input terminal.

The TE mode passes through the first delay line 116A, the first FBG 117A, and the first optical circulator 118A, but the TM mode does not pass through the first delay line 116A, the first FBG 117A, and the first optical circulator 118A. Therefore, a delay difference T _1a that does not depend on the wavelength and a delay difference T _1b (λ) that depends on the wavelength are given between the TE mode and the TM mode. The TE mode and the TM mode are combined by the first polarization separation unit 12A, and the polarization plane rotation angle Ψ is given by the polarization plane rotation device 2.

The second delay line 116B, the second FBG 117B, and the second optical circulator 118B correspond to the first delay line 116A, the first FBG 117A, and the first optical circulator 118A, respectively. However, the delay difference due to the second delay line 116B is T _2a , and the delay difference due to the second FBG 117B is T _2b (λ). Therefore, the delay difference T ₁ (λ) = T _1a + T _1b (λ), the delay difference T ₂ (λ) = T _2a + T _2b (λ), and the rotation angle Ψ are added to the optical signal.

(Modification)
In the first and second embodiments, a diffraction grating is used as the wavelength separating unit, and LCoS is used as the delay difference providing unit. In the third and fourth embodiments, a VIPA glass plate is used as the wavelength separation unit, and a three-dimensional mirror is used as the delay difference providing unit. Here, as a first modification, a diffraction grating may be used as the wavelength separation unit, and a three-dimensional mirror may be used as the delay difference providing unit. As a second modification, a VIPA glass plate may be used as the wavelength separation unit, and LCoS may be used as the delay difference providing unit.

  In Embodiment 1-6, the first delay difference providing device 1A and the second delay difference providing device 1B are realized by using similar wavelength separation delay difference providing means. Here, as a third modification, the first delay difference applying device 1A and the second delay difference applying device 1B may be realized by using different wavelength separation delay difference applying means. In Embodiment 1-6, the delay difference providing apparatus has two stages. Here, as a fourth modification, the delay difference providing device may be multi-staged, and multistage connection is possible using an optical circulator. In Embodiment 1-6, the first delay difference providing device 1A and the second delay difference providing device 1B perform wavelength separation after performing polarization separation. Here, as a fifth modification, the first delay difference providing apparatus 1A and the second delay difference providing apparatus 1B may perform polarization separation after performing wavelength separation.

  The polarization mode dispersion generating apparatus according to the present invention can generate complex polarization mode dispersion including polarization dependence and wavelength dependence in a simulated manner when generating the polarization mode dispersion in a simulated manner.

DESCRIPTION OF SYMBOLS 1A: 1st delay difference provision apparatus 1B: 2nd delay difference provision apparatus 2: Polarization surface rotation apparatus 3: Optical circulator 4: Lens 11: Wavelength separation delay difference provision part 12: Polarization separation part 21: Variable Faraday rotator 22 : Mirror 23: Optical circulator 111: Mirror 112: Diffraction grating 113: LCoS
114: VIPA glass plate 115: Three-dimensional mirror 116: Delay line 117: FBG
118: Optical circulator

Claims (8)

A first delay difference providing device that applies a delay difference between orthogonal polarizations of the input optical signal to the input optical signal so as to depend on a wavelength of the input optical signal;
A polarization plane rotating device that rotates the polarization plane of the output optical signal from the first delay difference providing device;
Output from the polarization rotator so that the delay difference between orthogonal polarizations of the output optical signal from the polarization rotator depends on the wavelength of the output optical signal from the polarization rotator. A second delay difference applying device for applying to an optical signal;
A polarization mode dispersion generator comprising: The wavelength λ of the optical signal, the delay difference T ₁ (λ) provided by the first delay difference applying device, the rotation angle Ψ provided by the polarization plane rotating device, and the delay difference T provided by the second delay difference applying device. ₂ (λ), the desired magnitude of the PMD (Polarization Mode Dispersion) vector DGD (Differential Group Delay), and the desired component PCD (Polarization-Dependent Chromatic in the same direction as the PMD vector among the rate of change of the PMD vector with respect to the wavelength λ Dispersion) and a desired component Depol (Depolarization) in the direction perpendicular to the PMD vector among the rate of change of the PMD vector with respect to the wavelength λ.

The first delay difference giving device gives the delay difference T ₁ (λ), the polarization plane rotating device gives the rotation angle Ψ, and the second delay difference giving device delays so that The polarization mode dispersion generating apparatus according to claim 1, wherein a difference T ₂ (λ) is given. The first delay difference providing device includes:
A first polarization wavelength separation unit for separating the input optical signal into optical signals having orthogonal polarizations and separating optical signals having different wavelengths;
A first delay difference that gives a delay difference corresponding to the polarization and wavelength of each output optical signal of the first polarization wavelength separation unit between the output optical signals of the first polarization wavelength separation unit. A granting unit,
The second delay difference providing device includes:
The output optical signal from the polarization plane rotating device is separated into optical signals having orthogonal polarizations, and a second polarization wavelength separation unit that separates optical signals having different wavelengths;
A second delay difference that gives a delay difference corresponding to the polarization and wavelength of each output optical signal of the second polarization wavelength separation unit between the output optical signals of the second polarization wavelength separation unit. The polarization mode dispersion generating apparatus according to claim 1, further comprising: an adding unit.   The wavelength separation part of the first polarization wavelength separation part and at least one of the wavelength separation part of the second polarization wavelength separation part is a diffraction grating. Polarization mode dispersion generator.   At least one of the wavelength separation part of the first polarization wavelength separation part and the wavelength separation part of the second polarization wavelength separation part is a VIPA (Virtual Imaging Phased Array) glass plate, The polarization mode dispersion generator according to claim 3.   4. The polarization mode dispersion generating apparatus according to claim 3, wherein at least one of the first delay difference providing unit and the second delay difference providing unit is LCoS (Liquid Crystal on Silicon). 5.   4. The polarization mode dispersion generating apparatus according to claim 3, wherein at least one of the first delay difference providing unit and the second delay difference providing unit is a three-dimensional mirror.   A combination of the wavelength separation part and the first delay difference providing part in the first polarization wavelength separation part, and a combination of the wavelength separation part and the second delay difference providing part in the second polarization wavelength separation part. 4. The polarization mode dispersion generating apparatus according to claim 3, wherein at least one of the combinations is FBG (Fiber Bragg Grating). 5.

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