JP2024113976A - Optical receiving device - Google Patents

Optical receiving device Download PDF

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JP2024113976A
JP2024113976A JP2023019298A JP2023019298A JP2024113976A JP 2024113976 A JP2024113976 A JP 2024113976A JP 2023019298 A JP2023019298 A JP 2023019298A JP 2023019298 A JP2023019298 A JP 2023019298A JP 2024113976 A JP2024113976 A JP 2024113976A
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昇太 石村
英憲 高橋
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KDDI Corp
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Abstract

【課題】光受信装置の方向を信号光の方向に調整することなく、２つのストークスパラメータの値により情報を復調できる様にする。【解決手段】光受信装置は、第１円偏波の変調光と前記第１円偏波とは直交する第２円偏波の連続光とを偏波多重した信号光を少なくとも第１信号光と第２信号光とに分岐する分岐手段と、前記第１信号光のストークスパラメータＳ１の値と、前記第２信号光のストークスパラメータＳ２の値と、に基づき前記変調光を復調する復調手段と、を備えている。【選択図】図２[Problem] To demodulate information based on the values of two Stokes parameters without adjusting the direction of an optical receiving device to the direction of a signal light. [Solution] The optical receiving device includes a branching means for branching a signal light obtained by polarization multiplexing modulated light of a first circular polarization and continuous light of a second circular polarization orthogonal to the first circular polarization into at least a first signal light and a second signal light, and a demodulating means for demodulating the modulated light based on the value of the Stokes parameter S1 of the first signal light and the value of the Stokes parameter S2 of the second signal light. [Selected Figure] Figure 2

Description

本開示は、光受信装置に関する。 This disclosure relates to an optical receiving device.

非特許文献１は、ストークスベクトル検波方式の光受信装置を用いた光通信システムを開示している。この光通信システムにおいて、光送信装置は、互いに直交する２つの直線偏波のうちの一方のＸ偏波の連続光（無変調光）と、他方のＹ偏波の変調光と、を合波することで信号光を生成する。そして、光送信装置は、光ファイバを介して、生成した信号光を光受信装置に送信する。光受信装置は、受信した信号光のストークスパラメータＳ２及びＳ３を求め、Ｓ２及びＳ３の値から光送信装置が送信した情報を復調する。 Non-Patent Document 1 discloses an optical communication system using an optical receiving device of a Stokes vector detection method. In this optical communication system, an optical transmitting device generates signal light by multiplexing continuous light (unmodulated light) of one of two linearly polarized waves that are orthogonal to each other, which is an X-polarized wave, and modulated light of the other, which is a Y-polarized wave. Then, the optical transmitting device transmits the generated signal light to an optical receiving device via an optical fiber. The optical receiving device calculates the Stokes parameters S2 and S3 of the received signal light, and demodulates the information transmitted by the optical transmitting device from the values of S2 and S3 .

また、非特許文献２は、光ファイバを用いることなく、信号光を空間伝送する空間光通信システムを開示している。 Non-Patent Document 2 discloses a spatial optical communication system that transmits signal light through space without using optical fibers.

Ｑｉａｎ Ｈｕ，ｅｔ ａｌ．，"Ａｄｖａｎｃｅｄ ｍｏｄｕｌａｔｉｏｎ ｆｏｒｍａｔｓ ｆｏｒ ｈｉｇｈ ｐｅｒｆｏｒｍａｎｃｅ ｓｈｏｒｔ ｒｅａｃｈ ｏｐｔｉｃａｌ ｉｎｔｅｒｃｏｎｎｅｃｔｓ"，ＯＰＴＩＣＳ ＥＸＰＲＥＳＳ，Ｖｏｌ．２３，Ｎｏ．３，ｐｐ．３２４５－３２５９，２０１５年Qian Hu, et al. , "Advanced modulation formats for high performance short reach optical interconnects", OPTICS EXPRESS, Vol. 23, No. 3, pp. 3245-3259, 2015 Ｋ．Ｍａｔｓｕｄａ，ｅｔ ａｌ．，"Ｄｅｍｏｎｓｔｒａｔｉｏｎ ｏｆ ａ Ｒｅａｌ－Ｔｉｍｅ １４Ｔｂ／ｓ Ｍｕｌｔｉ－Ａｐｅｒｔｕｒｅ Ｔｒａｎｓｍｉｔ Ｓｉｎｇｌｅ－Ａｐｅｒｔｕｒｅ Ｒｅｃｅｉｖｅ ＦＳＯ Ｓｙｓｔｅｍ Ｗｉｔｈ Ｃｌａｓｓ １ Ｅｙｅ－Ｓａｆｅ Ｔｒａｎｓｍｉｔ Ｉｎｔｅｎｓｉｔｙ"，ｉｎ Ｊｏｕｒｎａｌ ｏｆ Ｌｉｇｈｔｗａｖｅ Ｔｅｃｈｎｏｌｏｇｙ，ｖｏｌ．４０，ｎｏ．５，ｐｐ．１４９４－１５０１，２０２２年３月１日K. Matsuda et al. ,"Demonstration of a Real-Time 14Tb/s Multi-Aperture Transmit Single-Aperture Receive FSO System With Class 1 Eye-Safe Tra nsmit Intensity", in Journal of Lightwave Technology, vol. 40, no. 5, pp. 1494-1501, March 1, 2022

図７（Ａ）は、非特許文献１が開示する光受信装置の説明図である。信号光は、カップラ１で第１信号光、第２信号光及び第３信号光に３分岐される。第１信号光、第２信号光及び第３信号光は、それぞれ、第１パス、第２パス及び第３パスに出力される。第１パスに出力された第１信号光は、直接、検出器５に入力される。第２パスに出力された第２信号光は、半波長板（ＨＷＰ）２を介して検出器５に入力される。第３パスに出力された第３信号光は、１／４波長板（ＱＷＰ）３を介して検出器５に入力される。 Figure 7 (A) is an explanatory diagram of an optical receiving device disclosed in Non-Patent Document 1. Signal light is split into three parts, a first signal light, a second signal light, and a third signal light, by coupler 1. The first signal light, the second signal light, and the third signal light are output to the first path, the second path, and the third path, respectively. The first signal light output to the first path is directly input to detector 5. The second signal light output to the second path is input to detector 5 via half-wave plate (HWP) 2. The third signal light output to the third path is input to detector 5 via quarter-wave plate (QWP) 3.

図７（Ｂ）は、検出器５の構成図である。偏波ビームスプリッタ（ＰＢＳ）５１は、入力される光を、第１直線偏波の第１光と、第１直線偏波とは直交する第２直線偏波の第２光とに偏波分離する。第１光は、フォトダイオード（ＰＤ）５２に入力され、第２光は、ＰＤ５３に入力される。ＰＤ５２及びＰＤ５３は、入力される光の光電変換を行って電気信号を出力する。減算部５４は、ＰＤ５２からの電気信号とＰＤ５３からの電気信号との差分を出力する。ＰＤ５２、ＰＤ５３及び減算部５４は、所謂、バランスドＰＤを構成している。 Figure 7 (B) is a diagram showing the configuration of the detector 5. The polarizing beam splitter (PBS) 51 splits the input light into a first light of a first linear polarization and a second light of a second linear polarization that is orthogonal to the first linear polarization. The first light is input to a photodiode (PD) 52, and the second light is input to a PD 53. The PD 52 and PD 53 perform photoelectric conversion of the input light and output an electrical signal. The subtraction unit 54 outputs the difference between the electrical signal from the PD 52 and the electrical signal from the PD 53. The PD 52, PD 53, and the subtraction unit 54 constitute a so-called balanced PD.

以下の説明においては、検出器５のＰＢＳ５１が出力する第１直線偏波の電界方向（偏波面の方向）を"光受信装置の第１方向"と表記する。光受信装置のＨＷＰ２の遅軸は、光受信装置の第１方向に対して２２．５度の角度となる様に配置される。ＨＷＰ２の遅軸に対する角度がＸである直線偏波の光を入力すると、ＨＷＰ２は、その偏波面を角度２Ｘだけ回転させた直線偏波を出力する。光受信装置のＱＷＰ３の遅軸は、光受信装置の第１方向に対して４５度の角度となる様に配置される。ＱＷＰ３の遅軸に対する角度が４５度の直線偏波をＱＷＰ３に入力すると、ＱＷＰ３は、入力される直線偏波を円偏波に変換して出力する。なお、ＨＷＰ２及びＱＷＰ３の遅軸の角度は、上述した値に対して９０の整数倍を加えた値であっても良い。つまり、ＨＷＰ２の遅軸は、第１方向に対して、２２．５度、１１２．５度、２０２．５度、又は、２９２．５度にし得る。同様に、ＱＷＰ３の遅軸は、第１方向に対して、４５度、１３５度、２２５度、又は、３１５度にし得る。 In the following description, the electric field direction (direction of the polarization plane) of the first linearly polarized wave output by the PBS51 of the detector 5 is referred to as the "first direction of the optical receiving device". The slow axis of the HWP2 of the optical receiving device is arranged to be at an angle of 22.5 degrees with respect to the first direction of the optical receiving device. When linearly polarized light having an angle of X with respect to the slow axis of the HWP2 is input, the HWP2 outputs a linearly polarized wave with its polarization plane rotated by an angle of 2X. The slow axis of the QWP3 of the optical receiving device is arranged to be at an angle of 45 degrees with respect to the first direction of the optical receiving device. When a linearly polarized wave having an angle of 45 degrees with respect to the slow axis of the QWP3 is input to the QWP3, the QWP3 converts the input linearly polarized wave into a circularly polarized wave and outputs it. The angles of the slow axes of the HWP2 and QWP3 may be an integer multiple of 90 added to the above-mentioned values. That is, the slow axis of HWP2 can be 22.5 degrees, 112.5 degrees, 202.5 degrees, or 292.5 degrees with respect to the first direction. Similarly, the slow axis of QWP3 can be 45 degrees, 135 degrees, 225 degrees, or 315 degrees with respect to the first direction.

図７（Ａ）に示す様に、第１パスの検出器５の出力は、ストークスパラメータＳ１を示す。また、上記の様にＨＷＰ２の遅軸を設定することで、第２パスの検出器５の出力は、ストークスパラメータＳ２を示す。さらに、上記の様にＱＷＰ３の遅軸を設定することで、第３パスの検出器５の出力は、ストークスパラメータＳ３を示す。 7A, the output of the detector 5 of the first path indicates the Stokes parameter S 1. Moreover, by setting the slow axis of the HWP2 as described above, the output of the detector 5 of the second path indicates the Stokes parameter S 2. Furthermore, by setting the slow axis of the QWP3 as described above, the output of the detector 5 of the third path indicates the Stokes parameter S 3 .

例えば、信号光に含まれる連続光の偏波方向を、光受信装置の第１方向に対して９０度の整数倍に一致させる。つまり、連続光の偏波方向（電界方向）と、光受信装置の第１方向との角度を０、９０、１８０、２７０のいずれかにする。以下、この状態を"信号光の方向と光受信装置の方向が一致している"と表記する。以下では、基本的には、信号光に含まれる連続光の偏波方向を、光受信装置の第１方向に一致させたものとして説明する。この場合、連続光の電界成分をＥｘとして、変調光の電界成分をＥｙとすると、ストークスパラメータＳ１、Ｓ２及びＳ３は、それぞれ、以下の式で示す値になる。
Ｓ１＝｜Ｅｘ｜２－｜Ｅｙ｜２ （１）
Ｓ２＝２Ｒｅ（Ｅｘ×Ｅｙ＊） （２）
Ｓ３＝２Ｉｍ（Ｅｘ×Ｅｙ＊） （３）
なお、式（２）の"Ｒｅ（Ａ）"は、複素数Ａの実数部分を取り出す関数であり、式（３）の"Ｉｍ（Ａ）"は、複素数Ａの虚数部分を取り出す関数である。また、Ｅｙ＊は、Ｅｙの複素共役である。 For example, the polarization direction of the continuous light included in the signal light is made to coincide with an integer multiple of 90 degrees with respect to the first direction of the optical receiving device. In other words, the angle between the polarization direction (electric field direction) of the continuous light and the first direction of the optical receiving device is made to be any one of 0, 90, 180, and 270. Hereinafter, this state is expressed as "the direction of the signal light and the direction of the optical receiving device coincide". In the following, it is basically described that the polarization direction of the continuous light included in the signal light coincides with the first direction of the optical receiving device. In this case, if the electric field component of the continuous light is Ex and the electric field component of the modulated light is Ey, the Stokes parameters S 1 , S 2 , and S 3 are respectively values shown in the following formulas.
S 1 = |Ex| 2 - |Ey| 2 (1)
S2 =2Re(Ex×Ey * ) (2)
S 3 =2Im(Ex×Ey * ) (3)
In addition, “Re(A)” in formula (2) is a function that extracts the real part of complex number A, and “Im(A)” in formula (3) is a function that extracts the imaginary part of complex number A. In addition, Ey * is the complex conjugate of Ey.

ストークスパラメータＳ２及びＳ３は、それぞれ、変調光と連続光のビート成分であり、光受信装置は、Ｓ２＋ｊＳ３の値を求めることで、光送信装置が送信した情報を復調することができる。信号光の方向と光受信装置の方向が一致している場合、ストークスパラメータＳ１は情報の復調に必要ではないため、図７の第１パスを省略できる。一方、信号光の方向と光受信装置の方向を一致させることが難しい場合、値の補正のためにストークスパラメータＳ１が必要となり、図７の第１パスを省略することはできない。 The Stokes parameters S2 and S3 are the beat components of the modulated light and the continuous light, respectively, and the optical receiving device can demodulate the information transmitted by the optical transmitting device by determining the value of S2 + jS3 . When the direction of the signal light and the direction of the optical receiving device are the same, the Stokes parameter S1 is not necessary for demodulating the information, so the first pass in Fig. 7 can be omitted. On the other hand, when it is difficult to make the direction of the signal light and the direction of the optical receiving device match, the Stokes parameter S1 is required to correct the value, and the first pass in Fig. 7 cannot be omitted.

例えば、空間光通信システム等、信号光の方向と光受信装置の方向を一致させることが難しい場合がある。この様な場合、光受信装置には、３つのストークスパラメータＳ１、Ｓ２及びＳ３を出力する３つのパスが必要となる。 For example, in a free-space optical communication system, it may be difficult to match the direction of a signal light with that of an optical receiving device. In such a case, the optical receiving device needs three paths that output three Stokes parameters S 1 , S 2 , and S 3 .

本開示は、光受信装置の方向を信号光の方向に調整することなく、２つのストークスパラメータの値により情報を復調できる様にする技術を提供するものである。 This disclosure provides a technology that enables information to be demodulated using the values of two Stokes parameters without adjusting the direction of the optical receiving device to match the direction of the signal light.

本開示の一態様によると、光受信装置は、第１円偏波の変調光と前記第１円偏波とは直交する第２円偏波の連続光とを偏波多重した信号光を少なくとも第１信号光と第２信号光とに分岐する分岐手段と、前記第１信号光のストークスパラメータＳ１の値と、前記第２信号光のストークスパラメータＳ２の値と、に基づき前記変調光を復調する復調手段と、を備えている。 According to one aspect of the present disclosure, an optical receiving device includes a branching means for branching a signal light obtained by polarization multiplexing modulated light of a first circular polarization and continuous light of a second circular polarization orthogonal to the first circular polarization, into at least a first signal light and a second signal light, and a demodulating means for demodulating the modulated light based on a value of a Stokes parameter S1 of the first signal light and a value of a Stokes parameter S2 of the second signal light.

本開示によると、光受信装置の方向を信号光の方向に調整することなく、２つのストークスパラメータの値により情報を復調することができる。 According to the present disclosure, information can be demodulated using the values of two Stokes parameters without adjusting the direction of the optical receiving device to match the direction of the signal light.

幾つかの実施形態による、光送信装置の構成図。FIG. 2 is a block diagram of an optical transmitting device according to some embodiments. 一実施形態による、光受信装置の構成図。FIG. 1 is a configuration diagram of an optical receiving device according to an embodiment. 一実施形態による、光受信装置の構成図。FIG. 1 is a configuration diagram of an optical receiving device according to an embodiment. 一実施形態による、光受信装置の構成図。FIG. 1 is a configuration diagram of an optical receiving device according to an embodiment. 一実施形態による、光送信装置の構成図。FIG. 1 is a configuration diagram of an optical transmitting device according to an embodiment. 一実施形態による、光受信装置の構成図。FIG. 1 is a configuration diagram of an optical receiving device according to an embodiment. 背景技術の説明図。FIG.

以下、添付図面を参照して実施形態を詳しく説明する。なお、以下の実施形態は特許請求の範囲に係る発明を限定するものではなく、また実施形態で説明されている特徴の組み合わせの全てが発明に必須のものとは限らない。実施形態で説明されている複数の特徴のうちの二つ以上の特徴が任意に組み合わされてもよい。また、同一若しくは同様の構成には同一の参照番号を付し、重複した説明は省略する。 The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. In addition, the same reference numbers are used for the same or similar configurations, and duplicate descriptions are omitted.

＜第一実施形態＞
図１は、本実施形態による光送信装置の構成図である。光源１１は直線偏波の連続光を生成する。光源１１が生成した連続光は、偏波分離器１２で、Ｘ偏波の第１連続光と、Ｘ偏波とは直交するＹ偏波の第２連続光と、に分離される。なお、第１連続光と第２連続光の振幅が等しくなる様に、偏波分離器１２は、入力される連続光を分離する構成とし得る。偏波分離器１２が出力する第１連続光は、偏波多重器１４に入力される。一方、偏波分離器１２が出力する第２連続光は、変調器１３に入力される。変調器１３は、送信するデータで第２連続光を変調し、変調光を偏波多重器１４に出力する。偏波多重器１４は、Ｘ偏波の第１連続光と、Ｙ偏波の変調光と、を偏波多重した多重信号光を変換器１５に出力する。 First Embodiment
FIG. 1 is a configuration diagram of an optical transmission device according to this embodiment. A light source 11 generates continuous light of linear polarization. The continuous light generated by the light source 11 is separated by a polarization separator 12 into a first continuous light of X polarization and a second continuous light of Y polarization orthogonal to the X polarization. The polarization separator 12 may be configured to separate the input continuous light so that the amplitudes of the first and second continuous lights are equal. The first continuous light output by the polarization separator 12 is input to a polarization multiplexer 14. Meanwhile, the second continuous light output by the polarization separator 12 is input to a modulator 13. The modulator 13 modulates the second continuous light with data to be transmitted and outputs the modulated light to the polarization multiplexer 14. The polarization multiplexer 14 outputs a multiplexed signal light obtained by polarization multiplexing the first continuous light of X polarization and the modulated light of Y polarization to a converter 15.

変換器１５は、Ｘ偏波及びＹ偏波の光を、それぞれ、互いに直交する円偏波の光に変換する。一例として、変換器１５は、Ｘ偏波の光を右旋回偏波に変換し、Ｙ偏波の光を左旋回偏波に変換する。変換器１５は、例えば、ＱＷＰであり得る。変換器１５は、互いに直交する円偏波の連続光と変調光とを偏波多重した信号光を、例えば、空間を介して光受信装置に送信する。 The converter 15 converts the X-polarized and Y-polarized light into mutually orthogonal circularly polarized light. As an example, the converter 15 converts the X-polarized light into right-handed circularly polarized light and the Y-polarized light into left-handed circularly polarized light. The converter 15 may be, for example, a QWP. The converter 15 transmits, for example, via space, a signal light obtained by polarization multiplexing the mutually orthogonal circularly polarized continuous light and modulated light to an optical receiving device.

図２は、本実施形態による光受信装置の構成図である。光受信装置は、カップラ２１と、復調部２００と、を有する。カップラ２１は、光送信装置から受信する信号光を、少なくとも、第１信号光と第２信号光の２つの信号光に分岐して復調部２００に出力する分岐部である。復調部２００において、第１信号光は、直接、検出器５に入力される。一方、第２信号光は、ＨＷＰ２を介して検出器５に入力される。検出器５は、図７（Ｂ）と同様である。図２の光受信装置についても、検出器５のＰＢＳ５１が出力する偏波の方向に基づき第１方向が定義される。ＨＷＰ２の遅軸は、第１方向に対して２２．５度に設定される。つまり、図２の光受信装置は、図７に示す第１パスと第２パスを有するが第３パスを有さない。光受信装置は、第１パスの検出器５が出力するストークスパラメータＳ１の値と、第２パスの検出器５が出力するストークスパラメータＳ２の値と、に基づき光送信装置が送信した情報を復調する。 FIG. 2 is a configuration diagram of an optical receiving device according to this embodiment. The optical receiving device has a coupler 21 and a demodulation unit 200. The coupler 21 is a branching unit that branches the signal light received from the optical transmitting device into at least two signal lights, a first signal light and a second signal light, and outputs them to the demodulation unit 200. In the demodulation unit 200, the first signal light is directly input to the detector 5. On the other hand, the second signal light is input to the detector 5 via the HWP2. The detector 5 is the same as that in FIG. 7(B). In the optical receiving device of FIG. 2, the first direction is also defined based on the direction of polarization output by the PBS 51 of the detector 5. The slow axis of the HWP2 is set to 22.5 degrees with respect to the first direction. In other words, the optical receiving device of FIG. 2 has the first path and the second path shown in FIG. 7, but does not have the third path. The optical receiving apparatus demodulates the information transmitted by the optical transmitting apparatus based on the value of the Stokes parameter S1 output by the detector 5 on the first path and the value of the Stokes parameter S2 output by the detector 5 on the second path.

以下、第１パスの検出器５及び第２パスの検出器５の出力に基づき光送信装置が送信した情報を復調できる理由について説明する。連続光の電界成分をＥｘとし、変調光の電界成分をＥｙとすると、連続光と変調光は互いに回転方向の異なる円偏波であるため、信号光は、以下のジョーンズベクトルで表される。 The reason why the information transmitted by the optical transmitting device can be demodulated based on the output of the detector 5 of the first path and the detector 5 of the second path will be explained below. If the electric field component of the continuous light is Ex and the electric field component of the modulated light is Ey, the continuous light and the modulated light are circularly polarized waves with different rotation directions, so the signal light is expressed by the following Jones vector.

Figure 2024113976000002
Figure 2024113976000002

したがって、図２の光受信装置の第１パスの検出器５の出力Ａは、式（１）におけるＥｘを（１／√２）（Ｅｘ＋Ｅｙ）とし、Ｅｙをｊ（１／√２）（Ｅｘ－Ｅｙ）としたものになる。したがって、第１パスの検出器５の出力Ａは、以下の式（４）の通りとなる。 Therefore, the output A of the detector 5 on the first path of the optical receiving device in Figure 2 is calculated by replacing Ex in equation (1) with (1/√2)(Ex+Ey) and Ey with j(1/√2)(Ex-Ey). Therefore, the output A of the detector 5 on the first path is as shown in the following equation (4).

Figure 2024113976000003
Figure 2024113976000003

同様に、図２の光受信装置の第２パスの検出器５の出力Ｂは、式（２）におけるＥｘを（１／√２）（Ｅｘ＋Ｅｙ）とし、Ｅｙをｊ（１／√２）（Ｅｘ－Ｅｙ）としたものになる。したがって、第２パスの検出器５の出力Ｂは、以下の式（５）の通りとなる。 Similarly, the output B of detector 5 on the second path of the optical receiving device in Figure 2 is calculated by replacing Ex in equation (2) with (1/√2)(Ex+Ey) and Ey with j(1/√2)(Ex-Ey). Therefore, the output B of detector 5 on the second path is as shown in equation (5) below.

Figure 2024113976000004
Figure 2024113976000004

式（５）及び式（６）に示す様に、第１パスの検出器５の出力Ａは、式（２）の値に対応し、第２パスの検出器５の出力Ｂは、式（３）の値に対応する。したがって、光受信装置２は、２つのストークスパラメータの値により情報を復調することができる。 As shown in equations (5) and (6), the output A of the detector 5 on the first path corresponds to the value of equation (2), and the output B of the detector 5 on the second path corresponds to the value of equation (3). Therefore, the optical receiving device 2 can demodulate information using the values of the two Stokes parameters.

以上、本実施形態では、光受信装置の方向を信号光に対して調整することなく、２つのストークスパラメータの値により情報を復調することができる。 As described above, in this embodiment, information can be demodulated using the values of the two Stokes parameters without adjusting the direction of the optical receiving device relative to the signal light.

＜第二実施形態＞
続いて、第二実施形態について第一実施形態との相違点を中心に説明する。本実施形態の光送信装置の構成は第一実施形態と同様である。図３は、本実施形態による光受信装置の構成図である。 Second Embodiment
Next, the second embodiment will be described focusing on the differences from the first embodiment. The configuration of the optical transmitter of this embodiment is the same as that of the first embodiment. Fig. 3 is a configuration diagram of the optical receiver according to this embodiment.

本実施形態による光受信装置は、ＱＷＰ２２と、カップラ２１と、復調部２０１と、を有する。復調部２０１は、図７（Ａ）に示す、ストークスパラメータＳ２の値を検出するための第２パスと、ストークスパラメータＳ３の値を検出するための第３パスと、を有する。第２パス及び第３パスに設けられるＨＷＢ２及びＱＷＰ３の遅軸の方向は、図７（Ａ）で説明した通りである。本実施形態の光受信装置も、検出器５のＰＢＳ５１が出力する偏波の方向に基づき第１方向が定義される。なお、光受信装置の第１方向は、復調部２０１の第１方向としても参照され得る。 The optical receiving device according to this embodiment includes a QWP 22, a coupler 21, and a demodulation unit 201. The demodulation unit 201 includes a second path for detecting the value of the Stokes parameter S2 and a third path for detecting the value of the Stokes parameter S3 , as shown in FIG. 7A. The directions of the slow axes of the HWB 2 and the QWP 3 provided in the second and third paths are as described in FIG. 7A. In the optical receiving device according to this embodiment, the first direction is also defined based on the direction of the polarization output by the PBS 51 of the detector 5. The first direction of the optical receiving device may also be referred to as the first direction of the demodulation unit 201.

ＱＷＰ２２は、受信する円偏波の信号光を直線偏波に変換する。直線偏波の信号光は、互いに直交する直線偏波の連続光と変調光とを含む。ＱＷＰ２２は、その遅軸が第１方向に対して９０度の整数倍となる様に設けられる。言い換えると、ＱＷＰ２２は、円偏波の光が入力された場合、その旋回方向に応じて、第１直線偏波又は第２直線偏波の光をカップラ２１に出力する様に設けられる。よって、カップラ２１に入力される連続光の偏波の方向は、第１方向に対して９０度の整数倍となる。したがって、図７（Ａ）で説明した様に、第２パスの検出器５は、式（２）対応する値を出力し、第３パスの検出器５は、式（３）に対応する値を出力する。したがって、光受信装置２は、光受信装置の方向を信号光に対して調整することなく、２つのストークスパラメータの値により情報を復調することができる。 The QWP 22 converts the received circularly polarized signal light into linearly polarized light. The linearly polarized signal light includes linearly polarized continuous light and modulated light that are orthogonal to each other. The QWP 22 is arranged so that its slow axis is an integer multiple of 90 degrees with respect to the first direction. In other words, when circularly polarized light is input, the QWP 22 is arranged to output the first linearly polarized light or the second linearly polarized light to the coupler 21 depending on the rotation direction. Therefore, the polarization direction of the continuous light input to the coupler 21 is an integer multiple of 90 degrees with respect to the first direction. Therefore, as described in FIG. 7(A), the detector 5 of the second path outputs a value corresponding to equation (2), and the detector 5 of the third path outputs a value corresponding to equation (3). Therefore, the optical receiving device 2 can demodulate information using the values of the two Stokes parameters without adjusting the direction of the optical receiving device with respect to the signal light.

＜第三実施形態＞
続いて、第三実施形態について第一実施形態及び第二実施形態との相違点を中心に説明する。本実施形態の光送信装置の構成は第一実施形態と同様である。図４は、本実施形態による光受信装置の構成図である。 Third Embodiment
Next, the third embodiment will be described focusing on the differences from the first and second embodiments. The configuration of the optical transmitting device of this embodiment is the same as that of the first embodiment. Fig. 4 is a configuration diagram of the optical receiving device according to this embodiment.

本実施形態による光受信装置は、ＱＷＰ２２と、カップラ２１と、復調部２０２と、を有する。復調部２０２は、図７（Ａ）に示す、ストークスパラメータＳ１の値を検出するための第１パスと、ストークスパラメータＳ３の値を検出するための第３パスと、を有する。本実施形態の光受信装置では、第３パスの検出器５のＰＢＳ５１が出力する偏波の方向に基づき第１方向が定義される。なお、光受信装置の第１方向は、復調部２０２の第１方向としても参照され得る。また、本実施形態では、第１パスを第３パスに対して４５度だけ回転させる。つまり、第１パスの検出器５のＰＢＳ５１が出力する第３直線偏波と、第３直線偏波とは直交する第４直線偏波の偏波面は、第３パスの検出器５のＰＢＳ５１が出力する第１直線偏波及び第２直線偏波の偏波面と４５度の角度を有する。 The optical receiving device according to this embodiment includes a QWP 22, a coupler 21, and a demodulator 202. The demodulator 202 includes a first path for detecting the value of the Stokes parameter S1 and a third path for detecting the value of the Stokes parameter S3 , as shown in FIG. 7A. In the optical receiving device of this embodiment, a first direction is defined based on the direction of polarization output by the PBS 51 of the detector 5 of the third path. The first direction of the optical receiving device can also be referred to as the first direction of the demodulator 202. In addition, in this embodiment, the first path is rotated by 45 degrees with respect to the third path. That is, the third linearly polarized wave output by the PBS 51 of the detector 5 of the first path and the polarization plane of the fourth linearly polarized wave orthogonal to the third linearly polarized wave have an angle of 45 degrees with the polarization planes of the first linearly polarized wave and the second linearly polarized wave output by the PBS 51 of the detector 5 of the third path.

ＱＷＰ２２は、第二実施形態と同様であり、円偏波を第１直線偏波又は第２直線偏波に変換する。第３パスは、第二実施形態と同様であり、第３パスの検出器５は、式（３）に対応する値を出力する。一方、本実施形態では、第１パスの検出器５１には、そのＰＢＳ５１が出力する２つの直線偏波に対して４５度だけ回転させた偏波の直線偏波の信号光が入力される。これは、第二実施形態における第２パスの検出器５に入力される信号光と同じである。よって、第１パスの検出器５は、式（２）に対応する値を出力する。したがって、光受信装置２は、光受信装置の方向を信号光に対して調整することなく、２つのストークスパラメータの値により情報を復調することができる。 The QWP 22 is the same as in the second embodiment, and converts the circularly polarized wave into the first linear polarization or the second linear polarization. The third path is the same as in the second embodiment, and the detector 5 of the third path outputs a value corresponding to equation (3). On the other hand, in this embodiment, the detector 51 of the first path receives linearly polarized signal light with a polarization rotated by 45 degrees with respect to the two linearly polarized waves output by the PBS 51. This is the same as the signal light input to the detector 5 of the second path in the second embodiment. Therefore, the detector 5 of the first path outputs a value corresponding to equation (2). Therefore, the optical receiving device 2 can demodulate information using the values of the two Stokes parameters without adjusting the direction of the optical receiving device with respect to the signal light.

なお、本実施形態の第１パスの検出器５は、第３パスの検出器に対して４５度だけ回転させて設けられる。このため、復調部２０２の全体として考えると、第１パスは、ストークスパラメータＳ１の値を検出するものではなく、ストークスパラメータＳ２の値を検出するものと見做すこともできる。言い換えると、本実施形態の第１パスは、第二実施形態の第２パスに設けられたＨＷＰ２を省略する代わりに、第二実施形態の第２パスの検出器５を４５度だけ回転させたものと見做すことができる。しかしながら、第１パスのみを見ると、ＨＷＰ２がもうけられていないため、本実施形態では、第１パスがストークスパラメータＳ１の値を検出するものとしている。なお、第１パスが検出するものが、ストークスパラメータＳ１であっても、ストークスパラメータＳ２であっても、２つのストークスパラメータ（Ｓ１又はＳ２と、Ｓ３）のみを使用して情報を復調することには変わりない。 The detector 5 of the first path in this embodiment is rotated by 45 degrees with respect to the detector of the third path. Therefore, when considering the demodulation unit 202 as a whole, the first path can be regarded as detecting the value of the Stokes parameter S2 , not the value of the Stokes parameter S1 . In other words, the first path in this embodiment can be regarded as a detector 5 of the second path in the second embodiment rotated by 45 degrees, instead of omitting the HWP2 provided in the second path in the second embodiment. However, when only the first path is considered, since the HWP2 is not provided, in this embodiment, the first path is assumed to detect the value of the Stokes parameter S1 . Whether the first path detects the Stokes parameter S1 or the Stokes parameter S2 , the information is still demodulated using only two Stokes parameters ( S1 or S2 and S3 ).

＜第四実施形態＞
続いて、第四実施形態について、第二実施形態及び第三実施形態との相違点を中心に説明する。図５は、本実施形態による光送信装置の構成図である。なお、以下では、図１に示す光送信装置との構成との相違点を中心に説明する。本実施形態では、偏波分離器１２が出力する第１連続光も変調器１３で変調する。したがって、光送信装置は、互いに直交する円偏波の変調光を偏波多重した信号光を光受信装置に送信する。 <Fourth embodiment>
Next, the fourth embodiment will be described, focusing on the differences from the second and third embodiments. Fig. 5 is a configuration diagram of an optical transmission device according to this embodiment. The following description will focus on the differences from the configuration of the optical transmission device shown in Fig. 1. In this embodiment, the first continuous light output by the polarization separator 12 is also modulated by the modulator 13. Therefore, the optical transmission device transmits to the optical receiving device a signal light obtained by polarization multiplexing modulated light of mutually orthogonal circularly polarized waves.

図６は、本実施形態による光受信装置の構成図である。本実施形態の光受信装置２は、光源２４と、ＱＷＰ２２と、ＰＢＳ２５と、２つのカップラ２１と、２つの復調部２０１を有する。本実施形態では、２つの復調部２０１の第１方向を一致させるものとする。しかしながら、一方の復調部２０１の第１方向と、他方の復調部２０１の第１方向との角度が９０度の整数倍であれば良い。 Figure 6 is a configuration diagram of an optical receiving device according to this embodiment. The optical receiving device 2 of this embodiment has a light source 24, a QWP 22, a PBS 25, two couplers 21, and two demodulation units 201. In this embodiment, the first directions of the two demodulation units 201 are made to coincide. However, it is sufficient that the angle between the first direction of one demodulation unit 201 and the first direction of the other demodulation unit 201 is an integer multiple of 90 degrees.

ＱＷＰ２２は、第二実施形態と同様である。つまり、ＱＷＰ２２の遅軸は、光受信装置の第１方向に対して９０度の整数倍となる様に設けられる。したがって、ＱＷＰ２２は、第１直線偏波の変調光と第２直線偏波の変調光とを多重した偏波多重光をＰＢＳ２５に出力する。第１直線偏波の変調光と第２直線偏波の変調光の内の一方は、光送信装置におけるＸ偏波の変調光であり、他方は、光送信装置におけるＹ偏波の変調光である。光源２４は、無変調の連続光である局所光を生成してＰＢＳ２５に出力する。ＰＢＳ２５が第１直線偏波の変調光と第２直線偏波の局所光を偏波多重した信号光を生成して一方のカップラ２１に出力し、第２直線偏波の変調光と第１直線偏波の局所光を偏波多重した信号光を生成して他方のカップラ２１に出力する様に光源２４及びＰＢＳ２５は設けられる。したがって、第二実施形態で説明した様に、２つの復調部２０１は、それぞれ、光送信装置におけるＸ偏波の変調光と、Ｙ偏波の変調光との復調を行うことができる。 The QWP 22 is the same as in the second embodiment. That is, the slow axis of the QWP 22 is arranged to be an integer multiple of 90 degrees with respect to the first direction of the optical receiving device. Therefore, the QWP 22 outputs polarization multiplexed light in which the modulated light of the first linear polarization and the modulated light of the second linear polarization are multiplexed to the PBS 25. One of the modulated light of the first linear polarization and the modulated light of the second linear polarization is the modulated light of the X polarization in the optical transmitting device, and the other is the modulated light of the Y polarization in the optical transmitting device. The light source 24 generates local light, which is unmodulated continuous light, and outputs it to the PBS 25. The light source 24 and the PBS 25 are provided so that the PBS 25 generates signal light by polarization multiplexing the modulated light of the first linear polarization and the local light of the second linear polarization and outputs it to one coupler 21, and generates signal light by polarization multiplexing the modulated light of the second linear polarization and the local light of the first linear polarization and outputs it to the other coupler 21. Therefore, as described in the second embodiment, the two demodulation units 201 can demodulate the modulated light of the X polarization and the modulated light of the Y polarization in the optical transmission device, respectively.

なお、第三実施形態の構成を本実施形態に適用することもできる。この場合、図６の復調部２０１は、復調部２０２となる。また、２つの復調部の内の一方を第二実施形態の復調部２０１とし、他方を第三実施形態の復調部２０２とすることもできる。 The configuration of the third embodiment can also be applied to this embodiment. In this case, the demodulation unit 201 in FIG. 6 becomes the demodulation unit 202. Also, one of the two demodulation units can be the demodulation unit 201 of the second embodiment, and the other can be the demodulation unit 202 of the third embodiment.

以上、本実施形態でも、光受信装置の方向を信号光に対して調整することなく、２つのストークスパラメータの値により情報を復調することができる。また、本実施形態では、光通信システムの伝送容量を第一実施形態から第三実施形態の光通信システムより増加させることができる。 As described above, in this embodiment as well, information can be demodulated using the values of the two Stokes parameters without adjusting the direction of the optical receiving device relative to the signal light. Furthermore, in this embodiment, the transmission capacity of the optical communication system can be increased compared to the optical communication systems of the first to third embodiments.

以上の構成により、光受信装置の方向を信号光の方向に調整することなく、２つのストークスパラメータの値により情報を復調することができる。したがって、国連が主導する持続可能な開発目標（ＳＤＧｓ）の目標９「レジリエントなインフラを整備し、持続可能な産業化を推進するとともに、イノベーションの拡大を図る」に貢献することが可能となる。 With the above configuration, it is possible to demodulate information using the values of the two Stokes parameters without adjusting the direction of the optical receiving device to match the direction of the signal light. This makes it possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote sustainable industrialization and foster innovation."

発明は上記の実施形態に制限されるものではなく、発明の要旨の範囲内で、種々の変形・変更が可能である。 The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the invention.

２１：カップラ、２：半波長板、５：検出器、２００：復調部 21: coupler, 2: half-wave plate, 5: detector, 200: demodulator

Claims (14)

第１円偏波の変調光と前記第１円偏波とは直交する第２円偏波の連続光とを偏波多重した信号光を少なくとも第１信号光と第２信号光とに分岐する分岐手段と、
前記第１信号光のストークスパラメータＳ１の値と、前記第２信号光のストークスパラメータＳ２の値と、に基づき前記変調光を復調する復調手段と、
を備えている、光受信装置。 a branching means for branching a signal light obtained by polarization multiplexing a modulated light of a first circular polarization and a continuous light of a second circular polarization orthogonal to the first circular polarization into at least a first signal light and a second signal light;
a demodulation means for demodulating the modulated light based on a value of a Stokes parameter S1 of the first signal light and a value of a Stokes parameter S2 of the second signal light;
An optical receiving device comprising: 前記復調手段は、
前記第１信号光が入力される第１検出手段と、
半波長板を介して前記第２信号光が入力される第２検出手段と、
を備え、
前記第１検出手段及び前記第２検出手段は、それぞれ、
入力される光を第１直線偏波の第１光と前記第１直線偏波とは直交する第２直線偏波の第２光に分離する分離手段と、
前記第１光を光電変換した信号と前記第２光を光電変換した信号との差分を出力する出力手段と、
を備え、
前記半波長板の遅軸と前記第１直線偏波の偏波面との角度は、２２．５度、１１２．５度、２０２．５度、又は、２９２．５度である、請求項１に記載の光受信装置。 The demodulation means
a first detection means to which the first signal light is input;
a second detection means to which the second signal light is input via a half-wave plate;
Equipped with
The first detection means and the second detection means each include
a splitter for splitting an input light into a first light having a first linear polarization and a second light having a second linear polarization that is orthogonal to the first linear polarization;
an output unit that outputs a difference between a signal obtained by photoelectrically converting the first light and a signal obtained by photoelectrically converting the second light;
Equipped with
2. The optical receiving device according to claim 1, wherein an angle between a slow axis of the half-wave plate and a polarization plane of the first linearly polarized light is 22.5 degrees, 112.5 degrees, 202.5 degrees, or 292.5 degrees. 第１円偏波の変調光と前記第１円偏波とは直交する第２円偏波の連続光とを偏波多重した第１信号光を、第１直線偏波の前記変調光と前記第１直線偏波とは直交する第２直線偏波の前記連続光とを偏波多重した第２信号光に変換する変換手段と、
前記第２信号光を、少なくとも第３信号光と第４信号光とに分岐する分岐手段と、
前記第３信号光のストークスパラメータＳ２の値と、前記第４信号光のストークスパラメータＳ３の値と、に基づき、前記変調光を復調する復調手段と、
を備えている、光受信装置。 a conversion means for converting a first signal light obtained by polarization multiplexing modulated light of a first circular polarization and continuous light of a second circular polarization orthogonal to the first circular polarization, into a second signal light obtained by polarization multiplexing modulated light of a first linear polarization and continuous light of a second linear polarization orthogonal to the first linear polarization;
a branching means for branching the second signal light into at least a third signal light and a fourth signal light;
a demodulation unit that demodulates the modulated light based on a value of a Stokes parameter S2 of the third signal light and a value of a Stokes parameter S3 of the fourth signal light;
An optical receiving device comprising: 前記復調手段は、
半波長板を介して前記第３信号光が入力される第１検出手段と、
１／４波長板を介して前記第４信号光が入力される第２検出手段と、
を備え、
前記第１検出手段及び前記第２検出手段は、それぞれ、
入力される光を前記第１直線偏波の第１光と前記第２直線偏波の第２光に分離する分離手段と、
前記第１光を光電変換した信号と前記第２光を光電変換した信号との差分を出力する出力手段と、
を備え、
前記半波長板の遅軸と前記第１直線偏波の偏波面との角度は、２２．５度、１１２．５度、２０２．５度、又は、２９２．５度であり、
前記１／４波長板の遅軸と前記第１直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度である、請求項３に記載の光受信装置。 The demodulation means
a first detection means to which the third signal light is input via a half-wave plate;
a second detection means to which the fourth signal light is input via a quarter-wave plate;
Equipped with
The first detection means and the second detection means each include
a splitter for splitting an input light into a first light of the first linear polarization and a second light of the second linear polarization;
an output unit that outputs a difference between a signal obtained by photoelectrically converting the first light and a signal obtained by photoelectrically converting the second light;
Equipped with
the angle between the slow axis of the half-wave plate and the polarization plane of the first linearly polarized light is 22.5 degrees, 112.5 degrees, 202.5 degrees, or 292.5 degrees;
4. The optical receiving device according to claim 3, wherein an angle between a slow axis of the quarter-wave plate and a polarization plane of the first linearly polarized wave is 45 degrees, 135 degrees, 225 degrees, or 315 degrees. 第１円偏波の変調光と前記第１円偏波とは直交する第２円偏波の連続光とを偏波多重した第１信号光を、第１直線偏波の前記変調光と前記第１直線偏波とは直交する第２直線偏波の前記連続光とを偏波多重した第２信号光に変換する変換手段と、
前記第２信号光を、少なくとも第３信号光と第４信号光とに分岐する分岐手段と、
前記第３信号光のストークスパラメータＳ１の値と、前記第４信号光のストークスパラメータＳ３の値と、に基づき、前記変調光を復調する復調手段と、
を備えている、光受信装置。 a conversion means for converting a first signal light obtained by polarization multiplexing modulated light of a first circular polarization and continuous light of a second circular polarization orthogonal to the first circular polarization, into a second signal light obtained by polarization multiplexing modulated light of a first linear polarization and continuous light of a second linear polarization orthogonal to the first linear polarization;
a branching means for branching the second signal light into at least a third signal light and a fourth signal light;
a demodulation unit that demodulates the modulated light based on a value of a Stokes parameter S1 of the third signal light and a value of a Stokes parameter S3 of the fourth signal light;
An optical receiving device comprising: 前記復調手段は、
前記第３信号光が入力される第１検出手段と、
１／４波長板を介して前記第４信号光が入力される第２検出手段と、
を備え、
前記第１検出手段は、
入力される光を第３直線偏波の第１光と前記第３直線偏波とは直交する第４直線偏波の第２光に分離する第１分離手段と、
前記第１光を光電変換した信号と前記第２光を光電変換した信号との差分を出力する第１出力手段と、
を備え、
前記第２検出手段は、
入力される光を前記第１直線偏波の第３光と前記第２直線偏波の第４光に分離する分離手段と、
前記第３光を光電変換した信号と前記第４光を光電変換した信号との差分を出力する第２出力手段と、
を備え、
前記第１直線偏波の偏波面と前記第３直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度であり、
前記１／４波長板の遅軸と前記第１直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度である、請求項５に記載の光受信装置。 The demodulation means
a first detection means to which the third signal light is input;
a second detection means to which the fourth signal light is input via a quarter-wave plate;
Equipped with
The first detection means is
a first splitter for splitting an input light into a first light of a third linear polarization and a second light of a fourth linear polarization orthogonal to the third linear polarization;
a first output means for outputting a difference between a signal obtained by photoelectrically converting the first light and a signal obtained by photoelectrically converting the second light;
Equipped with
The second detection means is
a splitter for splitting an input light into a third light of the first linear polarization and a fourth light of the second linear polarization;
a second output means for outputting a difference between a signal obtained by photoelectrically converting the third light and a signal obtained by photoelectrically converting the fourth light;
Equipped with
an angle between the polarization plane of the first linear polarization and the polarization plane of the third linear polarization is 45 degrees, 135 degrees, 225 degrees, or 315 degrees;
6. The optical receiving device according to claim 5, wherein an angle between a slow axis of the quarter-wave plate and a polarization plane of the first linearly polarized light is 45 degrees, 135 degrees, 225 degrees, or 315 degrees. 第１円偏波の第１変調光と前記第１円偏波とは直交する第２円偏波の第２変調光とを偏波多重した第１信号光を、第１直線偏波の前記第１変調光と前記第１直線偏波とは直交する第２直線偏波の前記第２変調光とを偏波多重した第２信号光に変換する変換手段と、
連続光を生成する光源と、
前記第２信号光と前記連続光とに基づき、前記第１直線偏波の前記第１変調光と前記第２直線偏波の前記連続光とを偏波多重した第３信号光と、前記第１直線偏波の前記連続光と前記第２直線偏波の前記第２変調光とを偏波多重した第４信号光と、を生成する生成手段と、
前記第３信号光を、少なくとも第５信号光と第６信号光とに分岐する第１分岐手段と、
前記第５信号光のストークスパラメータＳ１又はＳ２の値と、前記第６信号光のストークスパラメータＳ３の値と、に基づき、前記第１変調光を復調する第１復調手段と、
前記第４信号光を、少なくとも第７信号光と第８信号光とに分岐する第２分岐手段と、
前記第７信号光のストークスパラメータＳ１又はＳ２の値と、前記第８信号光のストークスパラメータＳ３の値と、に基づき、前記第２変調光を復調する第２復調手段と、
を備えている、光受信装置。 a conversion means for converting a first signal light obtained by polarization multiplexing a first modulated light of a first circular polarization and a second modulated light of a second circular polarization orthogonal to the first circular polarization, into a second signal light obtained by polarization multiplexing the first modulated light of a first linear polarization and the second modulated light of a second linear polarization orthogonal to the first linear polarization;
A light source that generates continuous light;
a generating means for generating, based on the second signal light and the continuous light, a third signal light obtained by polarization multiplexing the first modulated light of the first linear polarization and the continuous light of the second linear polarization, and a fourth signal light obtained by polarization multiplexing the continuous light of the first linear polarization and the second modulated light of the second linear polarization;
a first branching means for branching the third signal light into at least a fifth signal light and a sixth signal light;
a first demodulation unit that demodulates the first modulated light based on a value of the Stokes parameter S1 or S2 of the fifth signal light and a value of the Stokes parameter S3 of the sixth signal light;
a second branching means for branching the fourth signal light into at least a seventh signal light and an eighth signal light;
a second demodulation means for demodulating the second modulated light based on the value of the Stokes parameter S1 or S2 of the seventh signal light and the value of the Stokes parameter S3 of the eighth signal light;
An optical receiving device comprising: 前記生成手段は、偏波ビームスプリッタである、請求項７に記載の光受信装置。 The optical receiving device according to claim 7, wherein the generating means is a polarizing beam splitter. 前記第１復調手段は、
半波長板を介して前記第５信号光が入力される第１検出手段と、
１／４波長板を介して前記第６信号光が入力される第２検出手段と、
を備え、
前記第１検出手段及び前記第２検出手段は、それぞれ、
入力される光を前記第１直線偏波の第１光と前記第２直線偏波の第２光に分離する第１分離手段と、
前記第１分離手段が分離した前記第１光を光電変換した信号と前記第１分離手段が分離した前記第２光を光電変換した信号との差分を出力する第１出力手段と、
を備え、
前記第１検出手段の前記半波長板の遅軸と前記第１直線偏波の偏波面との角度は、２２．５度、１１２．５度、２０２．５度、又は、２９２．５度であり、
前記第２検出手段の前記１／４波長板の遅軸と前記第１直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度である、請求項７に記載の光受信装置。 The first demodulation means
a first detection means to which the fifth signal light is input via a half-wave plate;
a second detection means to which the sixth signal light is input via a quarter-wave plate;
Equipped with
The first detection means and the second detection means each include
a first splitter for splitting an input light into a first light of the first linear polarization and a second light of the second linear polarization;
a first output means for outputting a difference between a signal obtained by photoelectrically converting the first light separated by the first separation means and a signal obtained by photoelectrically converting the second light separated by the first separation means;
Equipped with
the angle between the slow axis of the half-wave plate of the first detection means and the polarization plane of the first linearly polarized wave is 22.5 degrees, 112.5 degrees, 202.5 degrees, or 292.5 degrees;
8. The optical receiving device according to claim 7, wherein an angle between the slow axis of the quarter-wave plate of the second detecting means and the polarization plane of the first linearly polarized wave is 45 degrees, 135 degrees, 225 degrees, or 315 degrees. 前記第１復調手段は、
前記第５信号光が入力される第１検出手段と、
１／４波長板を介して前記第６信号光が入力される第２検出手段と、
を備え、
前記第１検出手段は、
入力される光を第３直線偏波の第３光と前記第３直線偏波とは直交する第４直線偏波の第４光に分離する第１分離手段と、
前記第１分離手段が分離した前記第３光を光電変換した信号と前記第１分離手段が分離した前記第４光を光電変換した信号との差分を出力する第１出力手段と、
を備え、
前記第２検出手段は、
入力される光を前記第１直線偏波の第１光と前記第２直線偏波の第２光に分離する第２分離手段と、
前記第２分離手段が分離した前記第１光を光電変換した信号と前記第２分離手段が分離した前記第２光を光電変換した信号との差分を出力する第２出力手段と、
を備え、
前記第１直線偏波の偏波面と前記第３直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度であり、
前記第２検出手段の前記１／４波長板の遅軸と前記第１直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度である、請求項７に記載の光受信装置。 The first demodulation means
a first detection means to which the fifth signal light is input;
a second detection means to which the sixth signal light is input via a quarter-wave plate;
Equipped with
The first detection means is
a first splitter for splitting an input light into a third light having a third linear polarization and a fourth light having a fourth linear polarization orthogonal to the third linear polarization;
a first output means for outputting a difference between a signal obtained by photoelectrically converting the third light separated by the first separation means and a signal obtained by photoelectrically converting the fourth light separated by the first separation means;
Equipped with
The second detection means is
a second splitter for splitting the input light into a first light of the first linear polarization and a second light of the second linear polarization;
a second output means for outputting a difference between a signal obtained by photoelectrically converting the first light separated by the second separation means and a signal obtained by photoelectrically converting the second light separated by the second separation means;
Equipped with
an angle between the polarization plane of the first linear polarization and the polarization plane of the third linear polarization is 45 degrees, 135 degrees, 225 degrees, or 315 degrees;
8. The optical receiving device according to claim 7, wherein an angle between the slow axis of the quarter-wave plate of the second detecting means and the polarization plane of the first linearly polarized wave is 45 degrees, 135 degrees, 225 degrees, or 315 degrees. 前記第２復調手段は、
半波長板を介して前記第７信号光が入力される第３検出手段と、
１／４波長板を介して前記第８信号光が入力される第４検出手段と、
を備え、
前記第３検出手段及び前記第４検出手段は、それぞれ、
入力される光を前記第１直線偏波の第１光と前記第２直線偏波の第２光に分離する第３分離手段と、
前記第３分離手段が分離した前記第１光を光電変換した信号と前記第３分離手段が分離した前記第２光を光電変換した信号との差分を出力する第３出力手段と、
を備え、
前記第３検出手段の前記半波長板の遅軸と前記第１直線偏波の偏波面との角度は、２２．５度、１１２．５度、２０２．５度、又は、２９２．５度であり、
前記第４検出手段の前記１／４波長板の遅軸と前記第１直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度である、請求項９又は１０に記載の光受信装置。 The second demodulation means
a third detection means to which the seventh signal light is input via a half-wave plate;
a fourth detection means to which the eighth signal light is input via a quarter-wave plate;
Equipped with
The third detection means and the fourth detection means each include
a third splitter for splitting the input light into a first light of the first linear polarization and a second light of the second linear polarization;
a third output means for outputting a difference between a signal obtained by photoelectrically converting the first light separated by the third separation means and a signal obtained by photoelectrically converting the second light separated by the third separation means;
Equipped with
the angle between the slow axis of the half-wave plate of the third detection means and the polarization plane of the first linearly polarized wave is 22.5 degrees, 112.5 degrees, 202.5 degrees, or 292.5 degrees;
11. The optical receiving device according to claim 9, wherein an angle between the slow axis of the quarter-wave plate of the fourth detection means and the polarization plane of the first linearly polarized wave is 45 degrees, 135 degrees, 225 degrees, or 315 degrees. 前記第２復調手段は、
前記第７信号光が入力される第３検出手段と、
１／４波長板を介して前記第８信号光が入力される第４検出手段と、
を備え、
前記第３検出手段は、
入力される光を第３直線偏波の第３光と前記第３直線偏波とは直交する第４直線偏波の第４光に分離する第３分離手段と、
前記第３分離手段が分離した前記第３光を光電変換した信号と前記第３分離手段が分離した前記第４光を光電変換した信号との差分を出力する第３出力手段と、
を備え、
前記第２検出手段は、
入力される光を前記第１直線偏波の第１光と前記第２直線偏波の第２光に分離する第４分離手段と、
前記第４分離手段が分離した前記第１光を光電変換した信号と前記第４分離手段が分離した前記第２光を光電変換した信号との差分を出力する第４出力手段と、
を備え、
前記第１直線偏波の偏波面と前記第３直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度であり、
前記第２検出手段の前記１／４波長板の遅軸と前記第１直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度である、請求項９又は１０に記載の光受信装置。 The second demodulation means
a third detection means to which the seventh signal light is input;
a fourth detection means to which the eighth signal light is input via a quarter-wave plate;
Equipped with
The third detection means is
a third splitter for splitting the input light into a third light having a third linear polarization and a fourth light having a fourth linear polarization that is orthogonal to the third linear polarization;
a third output means for outputting a difference between a signal obtained by photoelectrically converting the third light separated by the third separation means and a signal obtained by photoelectrically converting the fourth light separated by the third separation means;
Equipped with
The second detection means is
a fourth splitter that splits the input light into a first light of the first linear polarization and a second light of the second linear polarization;
a fourth output means for outputting a difference between a signal obtained by photoelectrically converting the first light separated by the fourth separation means and a signal obtained by photoelectrically converting the second light separated by the fourth separation means;
Equipped with
an angle between the polarization plane of the first linear polarization and the polarization plane of the third linear polarization is 45 degrees, 135 degrees, 225 degrees, or 315 degrees;
11. The optical receiving device according to claim 9, wherein an angle between the slow axis of the quarter-wave plate of the second detecting means and the polarization plane of the first linearly polarized wave is 45 degrees, 135 degrees, 225 degrees, or 315 degrees. 前記変換手段は、１／４波長板である、請求項３から８のいずれか１項に記載の光受信装置。 The optical receiving device according to any one of claims 3 to 8, wherein the conversion means is a quarter-wave plate. 第１円偏波の変調光と前記第１円偏波とは直交する第２円偏波の連続光とを偏波多重した第１信号光を、第１直線偏波の前記変調光と前記第１直線偏波とは直交する第２直線偏波の前記連続光とを偏波多重した第２信号光に変換する変換手段と、
前記第２信号光を、少なくとも第３信号光と第４信号光とに分岐する分岐手段と、
前記変調光を復調する復調手段と、
を備え、
前記復調手段は、
前記第３信号光が入力される第１検出手段と、
１／４波長板を介して前記第４信号光が入力される第２検出手段と、
を備え、
前記第１検出手段は、
入力される光を第３直線偏波の第１光と前記第３直線偏波とは直交する第４直線偏波の第２光に分離する第１分離手段と、
前記第１光を光電変換した信号と前記第２光を光電変換した信号との差分を出力する第１出力手段と、
を備え、
前記第２検出手段は、
入力される光を前記第１直線偏波の第３光と前記第２直線偏波の第４光に分離する分離手段と、
前記第３光を光電変換した信号と前記第４光を光電変換した信号との差分を出力する第２出力手段と、
を備え、
前記第１直線偏波の偏波面と前記第３直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度であり、
前記１／４波長板の遅軸と前記第１直線偏波の偏波面との角度は、４５度、１３５度、２２５度、又は、３１５度であり、
前記復調手段は、前記第１出力手段の出力と、前記第２出力手段の出力と、に基づき前記変調光を復調する、光受信装置。 a conversion means for converting a first signal light obtained by polarization multiplexing modulated light of a first circular polarization and continuous light of a second circular polarization orthogonal to the first circular polarization, into a second signal light obtained by polarization multiplexing modulated light of a first linear polarization and continuous light of a second linear polarization orthogonal to the first linear polarization;
a branching means for branching the second signal light into at least a third signal light and a fourth signal light;
demodulation means for demodulating the modulated light;
Equipped with
The demodulation means
a first detection means to which the third signal light is input;
a second detection means to which the fourth signal light is input via a quarter-wave plate;
Equipped with
The first detection means is
a first splitter for splitting an input light into a first light of a third linear polarization and a second light of a fourth linear polarization orthogonal to the third linear polarization;
a first output means for outputting a difference between a signal obtained by photoelectrically converting the first light and a signal obtained by photoelectrically converting the second light;
Equipped with
The second detection means is
a splitter for splitting an input light into a third light of the first linear polarization and a fourth light of the second linear polarization;
a second output means for outputting a difference between a signal obtained by photoelectrically converting the third light and a signal obtained by photoelectrically converting the fourth light;
Equipped with
an angle between the polarization plane of the first linear polarization and the polarization plane of the third linear polarization is 45 degrees, 135 degrees, 225 degrees, or 315 degrees;
the angle between the slow axis of the quarter-wave plate and the polarization plane of the first linearly polarized wave is 45 degrees, 135 degrees, 225 degrees, or 315 degrees;
The demodulation means demodulates the modulated light based on the output of the first output means and the output of the second output means.
JP2023019298A 2023-02-10 2023-02-10 Optical receiving device Pending JP2024113976A (en)

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